Home | Help | Feedback | Subscriptions | Archive | Search | Table of Contents

This Article Abstract Full Text (PDF, 777K) PPT slides of all figures Alert me when this article is cited Citation Map Services Email this article Similar articles in this journal Similar articles in PubMed Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Peters, M. F. Articles by Froehner, S. C. Search for Related Content PubMed PubMed Citation Articles by Peters, M. F. Articles by Froehner, S. C. Social Bookmarking                            What's this?

© The Rockefeller University Press, 0021-9525/1997//81 $5.00
The Journal of Cell Biology, Volume 138, Number 1, , 1997 81-93

Differential Association of Syntrophin Pairs with the Dystrophin Complex

Department of Physiology, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7545

The syntrophins are a multigene family of intracellular dystrophin-associated proteins comprising three isoforms, 1, β1, and β2. Based on their domain organization and association with neuronal nitric oxide synthase, syntrophins are thought to function as modular adapters that recruit signaling proteins to the membrane via association with the dystrophin complex. Using sequences derived from a new mouse β1-syntrophin cDNA, and previously isolated cDNAs for 1- and β2-syntrophins, we prepared isoform-specific antibodies to study the expression, skeletal muscle localization, and dystrophin family association of all three syntrophins. Most tissues express multiple syntrophin isoforms. In mouse gastrocnemius skeletal muscle, 1- and β1-syntrophin are concentrated at the neuromuscular junction but are also present on the extrasynaptic sarcolemma. β1-syntrophin is restricted to fast-twitch muscle fibers, the first fibers to degenerate in Duchenne muscular dystrophy. β2-syntrophin is largely restricted to the neuromuscular junction.

The sarcolemmal distribution of 1- and β1-syntrophins suggests association with dystrophin and dystrobrevin, whereas all three syntrophins could potentially associate with utrophin at the neuromuscular junction. Utrophin complexes immunoisolated from skeletal muscle are highly enriched in β1- and β2-syntrophins, while dystrophin complexes contain mostly 1- and β1-syntrophins. Dystrobrevin complexes contain dystrophin and 1- and β1-syntrophins. From these results, we propose a model in which a dystrophin–dystrobrevin complex is associated with two syntrophins. Since individual syntrophins do not have intrinsic binding specificity for dystrophin, dystrobrevin, or utrophin, the observed preferential pairing of syntrophins must depend on extrinsic regulatory mechanisms.

Syntrophins are intracellular peripheral membrane proteins of 58–60 kD originally identified as proteins enriched at the postsynaptic apparatus in Torpedo electric organ (17). More recently, syntrophins in mammalian skeletal muscle have been shown to be part of a complex of proteins that associate with dystrophin, the product of the Duchenne/Becker muscular dystrophy gene (4, 28, 50, 54). Many of the dystrophin-associated proteins (DAPs)¹ are transmembrane proteins. Thus, the dystrophin complex as a whole is thought to link cortical actin to the extracellular matrix, thereby stabilizing the sarcolemma during repeated cycles of contraction and relaxation (3). At the neuromuscular junction (NMJ), the DAPs have been implicated in agrin-stimulated clustering of nicotinic acetylcholine receptors (for review see reference 46). Dystrophin and DAPs are also found at synapses in the brain and retina (29, 33, 45). Thus, the syntrophins and other DAPs may participate in synaptogenesis as well as in sarcolemmal stabilization.

The three syntrophin isoforms, 1, β1, and β2, are encoded by different genes but have similar domain organizations. All known syntrophins contain two pleckstrin homology (PH) domains (2, 19), which are modules of 100 amino acids found in a wide array of signaling proteins. PH domains in other proteins bind phosphatidylinositol lipids and proteins, such as the β-subunits of trimeric G proteins (for review see reference 47). Thus, PH domains may mediate signal-dependent membrane association. Inserted within the first syntrophin PH domain is a PDZ domain (originally identified in postsynaptic density-95, discs large, ZO-1), a 90–amino acid domain found in more than 40 proteins, many of which are restricted to membrane specializations such as tight junctions or synapses (48). A trend emerging from study of other PDZ-containing proteins suggests that PDZ domains bind the cytoplasmic carboxy-terminal tails of transmembrane proteins (examples of which include NMDA receptors, K⁺ channels, Fas [42], and EGF receptors (for review see reference 48]). Finally, the COOH-terminal 57 amino acids of syntrophins are highly conserved among the three isoforms but are otherwise unique. This region, termed the syntrophin-unique (SU) domain, may contain the binding site for dystrophin family members (2, 6). Thus, the syntrophins are a family of multidomain proteins that likely function as modular adapters in recruiting signaling proteins to dystrophin complexes and the membrane.

Differential association of dystrophin with certain syntrophin isoforms and/or DAPs may play a role in tailoring the complex for a particular membrane specialization. Indeed, the protein complexes assembled by muscle dystrophin should be functionally distinct from those organized by retinal dystrophin. Likewise, each of the dystrophin-related proteins, utrophin, dystrophin-related protein 2 (DRP-2), and dystrobrevin, may differentially associate with particular DAPs in different cell types. All of these dystrophin family members contain amino acid sequences homologous to the dystrophin carboxy terminus, the region in dystrophin shown to bind syntrophins and the DAPs. Dystrophin, utrophin, and dystrobrevin have been shown to be capable of binding all three syntrophin isoforms in vitro (4, 6). With the exception of dystrobrevin, each dystrophin family member also has a WW domain postulated to bind the transmembrane DAP complex. Since each of the dystrophin family members is expressed in a wide range of cell types, their association with specific subsets of syntrophins/DAPs may be critical for cell-specific function.

Among all the DAPs, the syntrophins appear particularly well suited for differentially associating with the dystrophin family members. Each of the three syntrophins is postulated to function as a modular adapter recruiting signaling proteins to dystrophin membrane complexes. Yet, syntrophin isoforms share only 50% amino acid identity, suggesting that each may recruit a distinct set of proteins. Like members of the dystrophin family, the syntrophins are expressed in a wide range of tissues (1, 5). We have shown previously that in rat skeletal muscle, 1-syntrophin is localized on the sarcolemma with dystrophin, whereas β2-syntrophin is restricted to the NMJ, similar to utrophin (38). In contrast, the transmembrane dystroglycans are expressed in many tissues and are the products of a single gene (for review see reference 21). The sarcoglycans are comprised of multiple forms, but these are highly restricted to muscle (35, 53). In addition, most sarcoglycans are unrelated in amino acid sequence (32, 35), suggesting that they have distinct functions. Thus, among the known DAPs, syntrophins are leading candidates for associating with different dystrophin family members and could be involved in targeting of dystrophin family members to distinct membrane sites, or in conferring different functions to DAP complexes.

Here, we examine the associations of all three syntrophin isoforms with dystrophin family members expressed in skeletal muscle. We have previously isolated mouse cDNAs encoding 1- and β2-syntrophins (1) and examined the corresponding protein localization (38). However, these studies did not consider the recently described mammalian dystrobrevins (8, 41) or β1-syntrophin (5). We began this study by isolating the mouse β1-syntrophin cDNA and generating and characterizing isoform-specific antibodies. These isoform-specific antibodies were then used to define the distribution of each syntrophin and the association of syntrophins with dystrophin, utrophin, and dystrobrevin isoforms from normal, dystrophin-deficient, and 71–74 dystrophin transgenic mouse skeletal muscle. We find that pairs of syntrophin isoforms selectively copurify with dystrophin and utrophin. Based on these results, we propose a model in which particular pairs of syntrophin isoforms associate with dystrophin/dystrobrevin or utrophin/dystrobrevin complexes.

	Materials and Methods

Top Abstract Materials and Methods Results Discussion References

 
Mouse β1-Syntrophin cDNA Isolation
A gt11 mouse liver cDNA library (Clontech Labs, Palo Alto, CA) was screened by hybridization with ³²P-labeled human β1-syntrophin cDNA (a generous gift of Dr. Louis Kunkel, Howard Hughes Medical Institute, Boston, MA) by methods described previously (1). Five clones were isolated, but none of them contained the extreme 5' coding region. Therefore, this sequence was obtained by two consecutive rounds of 5' rapid amplification of cDNA ends using a kit purchased from GIBCO BRL (Gaithersburg, MD) and RNA isolated from C57Bl6 mouse liver (13). PCR products were amplified with Vent polymerase (NEB) using the sequence-specific primers 5'-CCTAATCTTGGAGACTCAGGTGG (round 1) and 5'-TCCCGCAGGTCTGCTCCGTTC (round 2). Resulting DNA from each round was cloned into Bluescript II (Stratagene, La Jolla, CA), and multiple clones were sequenced by the University of North Carolina Automated DNA Sequencing Facility (Chapel Hill, NC) on a DNA sequencer (model 373A; Applied Biosystems, Inc., Foster City, CA). Sequence was analyzed with the aid of a DNAStar Lasergene computer software package (Madison, WI).

Antibodies
Antisyntrophin.
mAb SYN1351 raised against Torpedo syntrophin has been described previously (17). Polyclonal antibodies (Abs) specific for each syntrophin isoform were prepared by immunizing rabbits with peptides according to standard methods (36). The Ab SYN37 was prepared against the peptide C-RLGGGSAEPLSSQSFSFHRDR, corresponding to amino acids 220–240 of mouse β1-syntrophin, plus an NH₂-terminal cysteine (see boxed region in Fig. 1 B). The β2-syntrophin antibody, SYN28, was prepared against C-SGSEDSGSPKHQNTTKDR as an alternative to the weaker Ab SYN24 previously prepared against the same peptide (38). The 1-syntrophin antibody, SYN17, was described previously (38). Each antipeptide antibody used in this study was affinity purified with peptide coupled to Affi-Gel-10 or -15 (BioRad Labs, Hercules, CA) as described previously (28) and was used directly or after biotinylation with sulfo-NHS-biotin (Pierce, Rockford, IL) according to the manufacturer's protocol.

View larger version (68K): [in this window] [in a new window] [Download PPT slide]   Figure 1 Cloning, sequence, and domain structure of murine β1-syntrophin sequence. (A) Strategy for cloning mouse β1-syntrophin and structure of the combined cDNAs, showing the coding region bounded by start and stop codons. (B) The deduced amino acid sequence of mouse β1-syntrophin is aligned with mouse 1- and β2-syntrophins (1, 2). Identical amino acids are shaded. The boundaries of PH (6, 19), PDZ (2), and SU (2) domains are indicated by arrows. The boxed region denotes sequences used to generate synthetic peptides for production of isoform-specific antibodies. (C) Schematic diagram showing the relative organization of PH, PDZ, and SU domains in syntrophins. Mouse β1-syntrophin cDNA sequence data are available from GenBank/EMBL/DBJ under the accession number U89997.

Antidystrophin.
Ab DYS3669 was prepared against COOH-terminal 10 amino acids of mouse dystrophin (22) plus a terminal cysteine (C-PGKPMREDTM) according to standard methods (36). mAb Mandys-8 (34) was purchased from Sigma Chemical Co. (St. Louis, MO).

Antiutrophin.
Ab UTR3165 was previously described (28). mAb DRP-1 was purchased from Novacastra Laboratories (Newcastle upon Tyne, UK).

Anti–myosin heavy chain (MHC).
mAbs BF-F3 (diluted 1:30) (44) and NCL-MHCf (Novacastra Laboratories, diluted 1:30) are specific for MHC expressed in type IIB fibers and all type II fibers, respectively. mAb A4.74 (diluted 1:30) (52) strongly labels rat MHC in type IIA and labels type IID fibers to a lesser extent.

Immunoaffinity Purification of Protein Complexes
Tissues from control (C57BL10 SNJ; Jackson Laboratory, Bar Harbor, ME), mdx (Jackson Laboratory), and 71–74/mdx mice (J.S. Chamberlain, University of Michigan, Ann Arbor, MI) (39) were dissected and frozen in liquid nitrogen. Protein complexes were partially purified as described previously (28). Briefly, tissues (5 g) were homogenized in 10 vol (wt/vol) of ice-cold homogenization buffer (HB; 10 mM Na phosphate, 0.4 M NaCl, 5 mM EDTA, pH 7.8, plus the protease inhibitors aprotinin, leupeptin, and antipain at 0.5 µg/ml each, pepstatin A, 0.05 µg/ml, and 2 mM PMSF) (28). The particulate fraction was pelleted (10 min at 12,000 g, model JA-20 rotor; Beckman Instruments, Fullerton, CA), resuspended in HB (10 vol), and recentrifuged. Washed pellets were solubilized in 1% Triton X-100/HB (3 vol) and incubated on ice for 15 min. For preparation of individual syntrophin isoforms (see Fig. 2), the particulate fractions were dissolved in 1% SDS/HB (3 vol) to disrupt possible complexes of multiple syntrophins. After incubation for 15 min, excess 1% Triton/HB (30 vol) was added. In all cases, the detergent-solubilized extracts were clarified by centrifugation (20 min at 53,000 g, model Ti 60 rotor; Beckman Instruments, Fullerton, CA) and incubated with antibody resins prepared by coupling 2 mg of affinity-purified antibody to 2 ml of Affi-gel 10 (BioRad Labs) according to manufacturer's specifications. After agitation for 2 h at 4°C, resins were collected in a column and washed sequentially with 1% Triton/HB (50 ml), 0.1% Triton/HB (10 ml), and HB (5 ml). Bound proteins were eluted with 0.1 M triethylamine, pH 11.5, precipitated with TCA, washed with 95% ethanol, and resuspended in SDS-PAGE sample buffer.

View larger version (44K): [in this window] [in a new window] [Download PPT slide]   Figure 2 Isoform specificity of syntrophin antibodies. Antibodies were characterized by immunoblotting samples enriched in individual syntrophin isoforms (as indicated above lanes). 1-, β1-, and β2-syntrophins were solubilized from crude membrane preparations from skeletal muscle, liver, and kidney, respectively, in 1% SDS to disrupt potential multi-syntrophin complexes. After addition of excess Triton, syntrophins were immunoaffinity purified with the appropriate antibody (Abs SYN17, SYN37, and SYN28). Blots were probed with mAb SYN1351 or biotinylated polyclonal antibodies as indicated. Labeling with each polyclonal antibody was eliminated by preincubation with the appropriate antigenic peptide (not shown). Positions of two molecular mass markers (52 and 59 kD) are shown on the right in the top panel.

Immunohistochemistry
The gastrocnemius, plantaris, and soleus were removed intact from mice, flash-frozen in liquid nitrogen–cooled isopentane, and cryosectioned (7 µm). Before labeling, sections were fixed with 0.5% paraformaldehyde, permeabilized with 0.5% Triton X-100/PBS/0.2 M NH₄Cl, and blocked with PBS containing 2% fish gelatin/0.08% BSA. Sections were incubated with primary antibodies (30 nM). After several PBS washes, sections were incubated with a cocktail containing either goat anti–rabbit IgG or anti–mouse IgM conjugated to Texas red (Jackson Immunoresearch; 1:200) mixed with either donkey anti–mouse IgG conjugated FITC or -bungarotoxin (Tx) conjugated to BODIPY-fluorescence (Molecular Probes, Eugene, OR; 1:300). Washed sections were fixed with 4% paraformaldehyde and mounted in glycerol containing n-propyl gallate to reduce photobleaching (20). Antibody specificity was tested by preincubating antibodies with their antigenic peptide (100 µM) for 30 min before labeling. Adjacent sections were stained with Mayers haematoxylin-eosin (30). Sections were viewed on a fluorescence microscope (model Axioskop; Carl Zeiss, Inc., Thornwood, NY) and photographed (TMax 400 film; Kodak, Rochester, NY).

	Results

Top Abstract Materials and Methods Results Discussion References

 
Isolation of Mouse β1-syntrophin cDNA
The cDNA encoding the mouse form of β1-syntrophin was obtained by screening a mouse gt11 cDNA library with the human β1-syntrophin cDNA. Five clones were isolated containing overlapping sequence that included >70% of the protein coding sequence and 820 base pairs of 3' untranslated region. The remaining 5' coding sequence was obtained by rapid amplification of cDNA ends (see Materials and Methods). The resulting cDNA (Fig. 1 A) contains 354 nucleotides 5' of a 1,611-nucleotide open reading frame. The first methionine codon is in a context favoring translation initiation (27) and aligns with that described for the human cDNA (5). The deduced protein contains 537 amino acids and has a predicted mass of 58,088 D and a pI of 8.3. Its amino acid sequence is 90% identical to human β1-syntrophin while sharing only 48 and 55% identity with human 1- and β2-syntrophins, respectively, indicating that it is the mouse ortholog of human β1-syntrophin (5). After the initial methionine, the amino termini of both mouse and human β1-syntrophin have a stretch of nine hydrophobic amino acids (alanine and valine). A similar sequence is present in the human β2-syntrophin (6) sequence but is absent in mouse β2-syntrophin (2) and the 1-syntrophins (1, 6, 54). Comparison of the amino acid sequences of the three mouse syntrophins shows marked conservation, particularly within the PDZ and SU domains (Fig. 1 B).

Specificity of Syntrophin Antibodies
To investigate the expression of syntrophins and their association with dystrophin and dystrophin-related proteins, we prepared and characterized a series of antisyntrophin antibodies. Polyclonal antibodies were generated against synthetic peptides corresponding to syntrophin sequences from a region poorly conserved among the three isoforms (see boxed region in Fig. 1 B). To test the specificity of these antibodies, syntrophin isoforms were partially purified with the appropriate syntrophin peptide antibody from mouse tissues rich in either 1-, β1-, or β2-syntrophin (skeletal muscle, liver, and kidney, respectively). To ensure that each preparation contained only a single syntrophin, samples were first treated with SDS to disrupt possible multimeric complexes and were then diluted with Triton X-100 before immunopurification. As expected from previous results (38), immunoblotting with the anti–1-syntrophin antibody, SYN17, labeled a single 60-kD protein in the 1-syntrophin preparation but did not recognize proteins in either the β1- or β2-syntrophin preparations (Fig. 2). Likewise, the anti–β1-syntrophin antibody, SYN37, strongly labeled proteins in the β1-syntrophin preparation without recognizing proteins in either the 1- or β2-syntrophin preparations. Finally, the β2-syntrophin antibodies, SYN24 and SYN28, recognized only β2-syntrophin. In contrast, mAb SYN1351, which recognizes an epitope in the PDZ domain (M.E. Adams, S.H. Gee, and S.C. Froehner, unpublished results), strongly labeled each syntrophin isoform (Fig. 2). Thus, we conclude that mAb SYN1351 is pan specific, while each of the syntrophin peptide antibodies is isoform-specific in immunoblotting and in immunoaffinity purification.

In addition to proteins of the size expected for full-length syntrophins, smaller proteins were recognized by the anti–β1- and anti–β2-syntrophin antibodies (Fig. 2). These proteins were also recognized by mAb SYN1351, thus confirming their identities as syntrophins. The tissue distribution patterns for these smaller syntrophin-related proteins are distinct from each other and from the corresponding full-length isoforms (Fig. 3). Although it is possible that the smaller proteins are proteolytic fragments, a more likely possibility is that they are generated by posttranslational modification or by alternative splicing of the β1- and β2-syntrophin mRNAs. Northern blot analysis identified multiple transcripts for β1- and β2-syntrophins, while only a single transcript for 1-syntrophin was found (1, 5, 6). Although the basis of these multiple transcripts is unknown, it is certainly possible that they encode modified forms of β1- and β2-syntrophins.

View larger version (68K): [in this window] [in a new window] [Download PPT slide]   Figure 3 Tissues express multiple syntrophin isoforms. Syntrophins were isolated from Triton X-100–solubilized tissue extracts with the pan-specific syntrophin antibody SYN1351. Sample loadings were adjusted to contain approximately equal amounts of total syntrophin, as judged by immunoblotting with SYN1351 (pan anti-syn). Individual syntrophin isoforms were identified by blotting with Abs SYN17 (anti–1 syn), SYN37 (anti–β1 syn), or SYN24 (anti–β2 syn). Positions of two molecular mass markers (52 and 59 kD) are shown on the right in the top panel.

Previously, we proposed that dystrophin and related proteins might each be associated with a particular syntrophin isoform (1). This proposal was based largely on the common expression patterns between dystrophin family members and individual syntrophin isoforms. In vitro binding studies have demonstrated, however, that all three syntrophins are able to bind to a region in the COOH-terminal domain of dystrophin encoded by exon 74, and to the analogous regions in utrophin and dystrobrevin (6, 15), with no intrinsic binding specificity. However, the associations that occur in vivo might be regulated by additional factors. To examine this possibility, we have used a combination of immunofluorescence microscopy and biochemical analysis to determine which syntrophin isoforms are associated with dystrophin, utrophin, and dystrobrevin complexes.

Skeletal muscle was chosen for these studies for several reasons. First, skeletal muscle expresses all three syntrophins, although 1-syntrophin is the predominant isoform (see Fig. 3 and results in references 1, 5, 6). Since the distributions of dystrophin, utrophin, and dystrobrevin are known in this tissue, a comparison of their localizations with the syntrophin isoforms can be used to corroborate the biochemical studies on isolated complexes. Furthermore, previous studies have shown that two syntrophins, 1 and β2, have distinct distributions in muscle, an observation that supports the idea of differential association of syntrophins and dystrophin family members (38). Finally, Duchenne muscular dystrophy has its most profound effects on skeletal muscle. Since the absence of dystrophin results in a loss of dystrophin-associated proteins, including syntrophins, understanding syntrophin's interactions in this tissue may be especially important in deciphering the molecular causes of this disease.

We performed immunofluorescence microscopy on sections of adult mouse muscle with the syntrophin isoform-specific antibodies. As reported previously (38, 55), labeling for 1-syntrophin was strong on sarcolemma with particular enrichment at NMJs (Fig. 4). A similar labeling pattern was identified for β1-syntrophin, although the staining intensity of individual fibers varied. Slow-twitch fibers (type I) displayed little or no β1-syntrophin labeling, while a subset of fast-twitch fibers (type II) showed intense labeling (Fig. 5 A). Among fast fibers, the most glycolytic ones (type IIB) showed stronger labeling than oxidative fibers (type IIA and D) (Fig. 5 B). Although this was the typical staining pattern, exceptions could be found. For example, in predominantly fast muscles, staining for β1-syntrophin in slow fibers was weak but clearly detectable (not shown). In contrast, differential staining of fiber types was not seen for 1-syntrophin (Fig. 5 A) or dystrophin (22).

View larger version (80K): [in this window] [in a new window] [Download PPT slide]   Figure 4 Localization of syntrophin isoforms in skeletal muscle. Regions of mouse gastrocnemius muscle containing NMJs were identified by -bungarotoxin (-BgTx). Distributions of 1-, β1-, and β2-syntrophins were determined with Abs SYN17, SYN37, and SYN28, respectively. In each case, the specificity of immunolabeling was confirmed in adjacent serial sections by preincubating antibodies with the appropriate antigenic peptide. Bar, 50 µm.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 5 Fiber-type specificity of β1-syntrophin. (A) Syntrophins were examined in sections of mouse hind limb muscle containing the mixed slow/fast-twitch plantaris (left of arrows) with the adjacent fast-twitch gastrocnemius (right of arrows). Labeling for 1- and β1-syntrophins (SYN17 and SYN37) is compared to that of fast fiber (type II) MHC staining (mAb NCL-MHCf). Note that β1-syntrophin labeling is highly restricted to a subset of type II myofibers, while 1-syntrophin labeling shows uniform fiber-type staining. (B) β1-syntrophin labeling was examined in subtypes of fast fibers identified by mAb BF-F3 specific for type IIB MHC (IIB) and mAb A4.74 specific for IIA, and to a lesser extent type IID MHC (IIA, D). β1 and IIA, D show a single cryosection double labeled as indicated, while IIB shows an adjacent serial section. Note the correspondence between strong labeling for β1-syntrophin (β1) and that of type IIB myosin (IIB). Bars: (A) 50 µm; (B) 80 µm.

Multiple Syntrophin Isoforms in Dystrophin and Utrophin Complexes
Previous biochemical studies showed that purified dystrophin complexes contain a triplet of syntrophin bands (55). However, the isoform identity of these syntrophin bands was not determined. Likewise, the syntrophin isoforms associated with utrophin in skeletal muscle have not been established. To determine which syntrophin isoforms are present in dystrophin and utrophin complexes, we partially purified dystrophin and utrophin from skeletal muscle extracts using immunoaffinity purification. When isolated in this way, dystrophin preparations contain no detectable utrophin, and utrophin preparations are free of detectable dystrophin (Fig. 6 A). Given the relative paucity of NMJ membrane (the site of highest concentration of utrophin) in skeletal muscle fibers, it is likely that much of the utrophin complex originated from nerve and blood vessels. In addition to the full-length utrophin (predicted to be 395 kD), a smaller utrophin-immunoreactive protein was identified. This 140-kD protein appears to be larger than G-utrophin and thus may either result from proteolysis of full-length utrophin or represent a previously undescribed utrophin homologue of Dp140. Aliquots of dystrophin and utrophin complexes containing approximately equal amounts of total syntrophin were analyzed by immunoblotting, thereby allowing comparison of the relative amounts of individual syntrophin isoforms. As shown in Fig. 6 A, dystrophin complexes were highly enriched in 1- and β1-syntrophins, while utrophin complexes contained mostly β1- and β2-syntrophins.

View larger version (60K): [in this window] [in a new window] [Download PPT slide]   Figure 6 Dystrophin and utrophin complexes contain distinct pairs of syntrophin isoforms. (A) Dystrophin and utrophin complexes were immunoaffinity purified from Triton-solubilized extracts of mouse skeletal muscle with antibodies DYS3669 and UTR3165, respectively. Sample loadings were adjusted to contain approximately equal amounts of syntrophin, as judged by immunoblotting (pan-Syn, mAb SYN1351). Duplicate blots were probed with mAbs Mandys-8 (Dys), and DRP-1 (Utr) or biotinylated polyclonal antibodies SYN17 (1-syn), SYN37 (β1-syn), and SYN28 (β2-syn). (B) Syntrophins were immunoaffinity purified from skeletal muscle extracts with Abs SYN17, SYN37, and SYN28. Sample loadings were adjusted to contain similar amounts of total syntrophin, as judged by immunoblotting (pan-Syn, mAb SYN1351). A duplicate blot was probed with mAb Mandys-8 (Dys), stripped, and reprobed with mAb DRP-1 (Utr). Positions of molecular mass markers (in kD) are shown in some panels. These results were replicated twice, and representative blots from a single experiment are shown.

Syntrophin Distribution in mdx Skeletal Muscle
Previous studies with the pan-specific syntrophin mAb SYN1351 showed that the loss of dystrophin from the sarcolemma causes a dramatic decrease of syntrophin staining (11). This decrease occurred despite the fact that total syntrophin, as measured by immunoblot analysis, was essentially unchanged in mdx muscle. To determine which isoforms are affected, we compared syntrophin isoform staining in normal and mdx gastrocnemius muscle. In wild-type mice, fibers of the gastrocnemius muscle, which are predominantly fast fiber type, have high levels of 1- and β1-syntrophins on the sarcolemma. However, in mdx muscle, the absence of dystrophin results in a dramatic reduction of both 1- and β1-syntrophin sarcolemmal staining (compare Fig. 7, A and B, to Fig. 4). This result provides further support for the association of 1- and β1-syntrophins with dystrophin.

View larger version (132K): [in this window] [in a new window] [Download PPT slide]   Figure 7 Localization of syntrophins in mdx mouse skeletal muscle. (A) The distribution of syntrophin isoforms was examined in regions containing NMJs (identified with -bungarotoxin; Tx). Labeling in the perisynaptic regions with antibodies SYN17 (1), SYN37 (β1), SYN28 (β2), and UTR3165 (Utr) was characterized. (B) In 8-wk-old mdx mice, regenerating fibers with central nuclei were identified by haematoxylin-eosin (H&E) staining. Serial sections were labeled with antibodies UTR3165 (Utr), DYS3669 (Dys), SYN17 (1), SYN37 (β1), and SYN28 (β2). Bars: (A; 1, β1, and Utr) 50 µm; (A; B2) 30 µm; (B) 50 µm.

In nonsynaptic regions, utrophin labeling was frequently seen on small caliber myofibers with centrally located nuclei, the hallmark of regenerated fibers (Fig. 7 B). In adjacent serial sections, staining for 1-syntrophin and especially β1-syntrophin mirrored that of utrophin. β2-syntrophin was not detectable under standard labeling conditions. These fibers are not revertants since antidystrophin labeling was negative (Fig. 7 B). Thus, although syntrophin immunoreactivity is dramatically reduced on the sarcolemma of mdx skeletal muscle, staining for at least two isoforms is retained in regions that express utrophin. When considered with the results of immunoaffinity purification, these data suggest that utrophin is capable of associating with each syntrophin isoform.

Two Syntrophin-binding Sites in the Dystrophin Complex
Results from other laboratories suggest that the syntrophin content in purified dystrophin complexes is approximately twice that of other dystrophin-associated proteins (16, 56). While only a single syntrophin-binding region has been clearly identified on dystrophin, a second syntrophin-binding protein, dystrobrevin, is known to be associated with the dystrophin complex in skeletal muscle (50, 51). Originally identified as a Torpedo phosphoprotein of 87 kD (51), dystrobrevin is homologous to the COOH-terminal region of dystrophin and contains a syntrophin-binding site (4, 15). This site is followed by two tandem heptad repeats of leucines predicted to form coiled-coils (7). Ozawa and colleagues have shown that dystrophin binds in vitro to a protein called A0, and they have mapped its binding site to the first heptad repeat of dystrophin (50). Subsequently, A0 was shown to be equivalent to dystrobrevin (58). A weaker binding site was found in the region of dystrophin that contains the second heptad repeat (50). Thus, we propose a model in which dystrophin and dystrobrevin associate via coiled-coil interactions (7) and could thus recruit two syntrophins to the dystrophin complex.

In complexes that contain two syntrophin-binding proteins (dystrophin and dystrobrevin), it is difficult to determine the type of syntrophin associated with either protein independently. In this regard, the 71–74 transgenic mdx mouse is particularly useful since it expresses a dystrophin transgene in skeletal muscle that lacks exons 71–74, which includes the syntrophin-binding site (for review see reference 18). In mdx muscle, 71–74 dystrophin produced by the transgene is targeted to the sarcolemma, such that normal levels of membrane-bound dystrophin-associated proteins are restored (39, 40). Surprisingly, the 71–74 dystrophin transgene restores syntrophin immunoreactivity to the sarcolemma, despite lacking the syntrophin-binding site (39, 40). Since the 71–74 dystrophin transgene product retains most of the coiled-coil region encoded by exon 75, it might still associate with dystrobrevin, which could in turn bind syntrophin and target it to the membrane. Indeed, we find dystrobrevin localized on the sarcolemma along with both 1- and β1-syntrophins (Fig. 8 B). Thus, 1- and β1-syntrophins may be restored to the membrane in these transgenic mice via association with dystrobrevin bound to dystrophin.

View larger version (110K): [in this window] [in a new window] [Download PPT slide]   Figure 8 Dystrobrevin associates with 1- and β1-syntrophins in 71–74/mdx skeletal muscle. (A) Schematic comparing the structure of the cysteine-rich COOH-terminal region of normal dystrophin, of the dystrophin transgene lacking exons 71–74, and the corresponding structure of dystrobrevin. The locations of the sequences used for preparation of dystrobrevin antipeptide antibodies DB308 and DB433 are indicated by bars. H1, H2, and WW, position of helix 1 and helix 2 and the WW domain, respectively. (B) Immunofluorescence labeling for 1-syntrophin (1, Ab SYN17), β1-syntrophin (β1, Ab SYN37), and dystrobrevin labeling (Db, mAb 13H1), with the corresponding labeling with -bungarotoxin (Tx) shown to the right of each image. The labeling for β2-syntrophin (β2, Ab SYN28) and -bungarotoxin (Tx) was reduced in size and intensity compared to control mice. (C) Dystrobrevin complexes were immunoaffinity purified from Triton extracts of 71–74/mdx skeletal muscle with antipeptide dystrobrevin antibodies that recognize either a central region (Ab DB308, left lane) or the linker between the two coiled-coils (Ab DB433, right lane). Sample loadings were adjusted for approximately equal amounts of dystrobrevin immunoreactivity in each lane (Db, mAb 13H1). Complexes purified with Ab DB433 contained dramatically lower amounts of dystrophin, as expected if this antibody inhibits a coiled-coil interaction between dystrophin and dystrobrevin; see text (Dys, Mandys-8). The total amount of syntrophin (pan-Syn, mAb SYN1351) purified with dystrobrevins was approximately the same with either Db antibody. Both 1-syntrophin (1-syn, Ab SYN17) and β1-syntrophin (β1-syn, Ab SYN37) copurified with dystrobrevin, independent of the presence of dystrophin. Utrophin and β2-syntrophin were detectable only with much longer exposure times.

We did note one important difference in the dystrobrevin complexes isolated with Abs DB308 and DB433. The dystrophin content in Ab DB433 preparations was dramatically reduced in comparison with the amounts obtained when Ab DB308 was used (Fig. 8 C, lanes DB433). It appears that Ab DB433, which recognizes the linker sequence between the coiled-coils of dystrobrevin, disrupts the interaction between dystrophin and dystrobrevin. Alternatively, it is possible that the epitope for Ab DB433 is more accessible in dystrobrevins that are not bound to dystrophin. Both of these possibilities are consistent with the idea that interaction between dystrobrevin and dystrophin is mediated by their coiled-coil regions.

	Discussion

Top Abstract Materials and Methods Results Discussion References

 
The syntrophins are a multigene family of modular adapter proteins thought to recruit signaling proteins to the membrane via association with dystrophin and other members of the dystrophin family. The existence of three isoforms derived from distinct genes makes the syntrophins unique among dystrophin-associated proteins. In skeletal muscle, we find that the syntrophins have distinct but overlapping distributions. These differential localizations imply that each syntrophin has a unique function, probably derived in part from association with either dystrophin or utrophin, in combination with dystrobrevin.

Our results suggest that pairs of syntrophin isoforms associate with dystrophin and utrophin complexes. Previous stoichiometric analyses of purified dystrophin complexes is in good agreement with two syntrophins per complex (16, 56). Several features of the dystrophin complex could account for the presence of two syntrophins. In addition to the known syntrophin-binding site in dystrophin encoded by the first half of exon 74 (4, 50), a second syntrophin-binding site has been proposed. A peptide corresponding to the latter half of 74 and exon 75 of dystrophin binds an 60-kD DAP (50). Although this protein was thought to be β1-syntrophin, it may instead be the 60-kD form of dystrobrevin. Indeed, the peptide also bound a larger protein (A0) (50), which has since been identified as full-length dystrobrevin (58). Thus, the putative second syntrophin-binding site, which encompasses the first coiled-coil of dystrophin, may instead be a site of interaction between dystrophin and dystrobrevin. A second possibility is that two syntrophins in a dystrophin complex could result from syntrophin dimerization. Syntrophins have been shown to bind an 60-kD DAP, leading to the suggestion that syntrophins form dimers (55). However, this binding may also represent syntrophin association with the 60-kD dystrobrevin. In fact, syntrophin also bound a larger protein of the approximate molecular weight of full-length dystrobrevin (55). Finally, multiple syntrophins may also be recruited to dystrophin complexes by association with other DAPs (31).

The model we favor incorporates a previous proposal (7) that dystrophin and dystrobrevin interact via their coiled-coils. Considerable evidence, including new results that we present here, supports an association of dystrophin with dystrobrevin. Dystrophin and dystrobrevin colocalize in skeletal muscle (8, 12), copurify biochemically (51), and associate directly in vitro via the coiled-coil region of dystrophin (50). We now find that dystrobrevin complexes isolated with an antibody to the coiled-coil region of dystrobrevin contain only small amounts of dystrophin when compared to complexes isolated with an antibody directed to another site. Thus, antibody binding to the coiled-coil region is incompatible with dystrophin–dystrobrevin association. Finally, purified dystrophin complexes can be partially dissociated into three groups, a dystroglycan subcomplex, a sarcoglycan subcomplex, and a dystrophin–dystrobrevin– syntrophin subcomplex by treatment with n-octyl β-d-glucoside (57). Detailed characterization of this association will be needed to determine the precise stoichiometry and binding orientation of the coiled-coil interaction. Despite this reservation, the evidence for an interaction between dystrophin and dystrobrevin is quite strong and leads us to suggest a new model for the dystrophin COOH-terminal region in which dystrophin and dystrobrevin combine to recruit two syntrophins per complex (Fig. 9 A).

View larger version (20K): [in this window] [in a new window] [Download PPT slide]   Figure 9 (A) Hypothetical model of the dystrophin complex containing two syntrophin-binding proteins. Syntrophins bind the exon 74–encoded region of dystrophin and the homologous region of dystrobrevin (6, 15). In both proteins, the syntrophin-binding site is followed by two heptad repeats of leucines (H1 and H2), separated by a short linker region (7). (B) Hypothetical examples of syntrophin isoform combinations as adapters linking membrane proteins or effector enzymes to dystrophin and utrophin. In fast-twitch myofibers, 1- and/or β1-syntrophin bind nNOS (10). In slow-twitch myofibers, 1-syntrophin is the predominant isoform present on the sarcolemma. Since slow-twitch fibers lack nNOS, the 1-syntrophin binding partners are unknown. Utrophin complexes contain β1- and β2-syntrophins. The binding partners for both syntrophins may be of particular relevance to NMJ function. DGC, dystroglycan complex; SGC, sarcoglycan complex.

Since the pairing of syntrophin isoforms is thus unlikely to be determined by intrinsic selectivity for dystrophin family members, several possible pairings within an individual dystrophin–dystrobrevin complex can be envisioned. For example, the observed pairing of 1- and β1-syntrophins with dystrophin could represent either 1/β1 heterodimers or similar amounts of 1/1 and β1/β1 homodimers with dystrophin. Indeed, these two possibilities are not mutually exclusive and may both occur in a single membrane region or may be differentially regulated at particular membrane regions. Distinguishing between these two possibilities in native complexes may prove technically difficult. Perhaps identification of the mechanisms that determine the syntrophin pairs may help to address these possibilities.

Syntrophins in Duchenne Muscular Dystrophy
A role for the syntrophins in muscular dystrophies or other myopathies has not received much attention, despite the fact that sarcolemmal expression of syntrophins, like that of the other proteins of the dystrophin complex, is dramatically reduced in Duchenne muscular dystrophy (DMD). Defects in other proteins of the dystrophin complex are the primary causes of other muscular dystrophies in which dystrophin is normal. For example, mutations in the genes encoding the sarcoglycans have been implicated in severe childhood autosomal recessive muscular dystrophy and in several forms of limb-girdle muscular dystrophy (for review see reference 37). Although no myopathies or other diseases have been linked to primary defects in syntrophins, our finding that β1-syntrophin is enriched in fast-twitch type IIB muscle fibers raises new issues with regard to the importance of syntrophins in DMD. Normally, dystrophin is expressed in all myofiber types (23), yet DMD preferentially affects human fast type IIB fibers (52). Although the mechanisms underlying this selective pathology remain to be determined, an intriguing possibility is that among the syntrophins, the function of β1-syntrophin is particularly important in maintaining sarcolemmal integrity.

Identifying other proteins associated with β1-syntrophin may be particularly relevant to understanding the molecular origin of the DMD myopathy. One possibility is that β1-syntrophin mediates the targeting of the neuronal form of nitric oxide synthase (nNOS) to the membrane. Like β1-syntrophin, nNOS is expressed preferentially in fast-twitch myofibers and is the only other protein known to correlate so closely with the fiber-type specific onset of DMD (26, 52). In normal muscle, nNOS is found on the sarcolemma in association with the dystrophin complex (9). This association is mediated, at least in part, by PDZ– PDZ heterodimerization between nNOS and syntrophin (10). Thus far, this nNOS interaction has been studied only in vitro with 1-syntrophin. It is possible that in vivo β1-syntrophin alone or paired with 1-syntrophin may be essential for targeting of nNOS to the sarcolemma, and could thus explain the fiber-type differences seen for this enzyme.

The physiological role of nNOS in normal skeletal muscle remains unknown, although some results suggest that it promotes muscle relaxation through a cGMP signaling pathway (26). The mechanism by which nNOS is activated in skeletal muscle is also poorly understood, although it is known that activation requires calcium/calmodulin and nNOS homodimerization (25). Neither the source of activating calcium nor the requirements for dimerization has been determined. Syntrophin association may play a role in both aspects of nNOS regulation. For example, close pairing of two syntrophins (discussed below) may facilitate nNOS dimerization, while syntrophin-mediated membrane localization may target nNOS to an appropriate Ca²⁺ source. Furthermore, loss of the syntrophin–nNOS complex from the membrane in dystrophic muscle may disrupt the nNOS-mediated relaxation pathway in favor of inappropriate cytoplasmic nNOS activation. This combination of loss of a potentially protective activity and acquisition of a potentially cytotoxic function may be central to DMD pathogenesis.

Syntrophins at the Neuromuscular Synapse
All three syntrophins are concentrated at the NMJ, but only β2-syntrophin is highly restricted to the synapse. 1- and β1-syntrophins are found on the entire sarcolemma with particularly high concentrations at synapses, a distribution similar to dystrophin. In contrast, the distribution of β2-syntrophin more closely resembles that of utrophin. Using immunoaffinity purification from whole skeletal muscle, we find that dystrophin preparations are enriched in 1- and β1-syntrophins, while utrophin complexes contain β1- and β2-syntrophin. Thus, while it is tempting to speculate that these preferential syntrophin–dystrophin/ utrophin pairings hold within the postsynaptic apparatus, two considerations make this conclusion premature. First, we find that all three syntrophins remain concentrated at the NMJ in mdx mice, possibly in association with utrophin. Second, the utrophin complexes isolated from skeletal muscle by biochemical means are not derived exclusively from the postsynaptic membrane, but come in large part from nonmuscle cells. Thus, it remains to be seen which syntrophin or combination of syntrophins colocalize with utrophin at the AChR-rich crests of the postsynaptic folds, or with dystrophin in the troughs, the site of high sodium channel density. Future studies will address this issue and the identification of synapse-specific binding partners for β2-syntrophin since it is unique among all the DAPs in its restriction to the postsynaptic apparatus.

Paired Syntrophins: Implications for Function
The discovery of two syntrophin isoforms in dystrophin/ utrophin complexes has clear implications for the mechanism of syntrophin function within membrane specializations. Specifically, the pairing of two PDZ-containing proteins in a submembrane complex resembles the membrane-associated guanylate kinase (MAGUK) complex. Like the syntrophins, the MAGUKs are a multigene family of PDZ-containing proteins that form submembranous protein scaffolds. The best characterized MAGUKs are the neuronal forms: PSD-95, Chapsyn-110, SAP97, and SAP102, which when expressed in COS cells combine to form homotypic and heterotypic multimers (24). MAGUKs have recently been shown to cluster membrane proteins such as K⁺ channels and NMDA-type glutamate receptors (for review see reference 48). The PDZ domains of certain MAGUKs mediate binding to the extreme COOH terminus of the cytoplasmic tail of membrane proteins (14, 49). Because this binding is dependent on the sequence of the COOH-terminal tail of the membrane protein, different MAGUK isoforms appear to bind different sets of membrane proteins. Thus, the combination of MAGUK isoforms at a particular membrane site may determine the composition of membrane proteins clustered there.

In contrast to the MAGUKs, which have three PDZ domains, syntrophins have only a single PDZ motif. This would appear to limit the ability of syntrophins to act as adapters in membrane organization by binding simultaneously multiple types of membrane proteins (such as ion channels) or a single membrane protein and an effector enzyme (such as nNOS). However, an attractive feature of the model in which two syntrophins are present in a single dystrophin complex is that each simultaneously could bind different proteins. Furthermore, a single complex might bind different combinations of proteins, depending on the specificity of the syntrophin PDZ domains. Thus, by regulating the syntrophin isoforms associated with dystrophin and dystrobrevin, or utrophin and dystrobrevin, the associated membrane or signaling protein might be different. The models shown in Fig. 9 show hypothetical combinations that might confer distinct functions on utrophin and dystrophin complexes, depending on the binding partners for the syntrophin PDZ domains.

Further studies will be required to determine if syntrophins play a role similar to that of the MAGUKs in membrane organization. Identifying the syntrophin PDZ domain binding partners and understanding the mechanisms that regulate the combinations of syntrophin isoforms in dystrophin complexes will be important for understanding the role of syntrophins in muscular dystrophy and in synapse formation.

	Acknowledgments

 
We thank our colleagues in the Froehner and Sealock laboratories for helpful discussions and comments on the manuscript. We are indebted to A.H. Ahn and L.M. Kunkel for providing human β1-syntrophin cDNA and results before publication, to J.S. Chamberlain for supplying the 71– 74/mdx transgenic mice, to Katherine North for assistance with skeletal muscle fiber-typing, to J.B. Cohen for providing mAB 13H1, to R. Sealock and N.R. Kramarcy for providing Ab DYS3669, and to Kirk McNaughton and Curtis Conner for extensive assistance with cryosectioning.

This work was supported by National Institutes of Health Grants NS33145 (to S.C. Froehner and R. Sealock) and NS14871 (to S.C. Froehner) and a Muscular Dystrophy Association (MDA) Grant (to S.C. Froehner). M.E. Adams was an MDA postdoctoral fellow.

Submitted: 8 April 1997

Revised: 29 May 1997

1. Abbreviations used in this paper: DAPs, dystrophin-associated proteins; DMD, Duchenne muscular dystrophy; DRP, dystrophin-related protein; HB, homogenization buffer; MAGUK, membrane-associated guanylate kinase; MHC, myosin heavy chain; NMJ, neuromuscular junction; nNOS, neuronal nitric oxide synthase; PDZ, protein domain originally identified in postsynaptic density-95, discs large, ZO-1; PH, pleckstrin homology; SU, syntrophin-unique.

Address all correspondence to S.C. Froehner, Department of Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7545. Tel.: (919) 966-1239. Fax: (919) 966-6413. E-mail: froehner{at}med.unc.edu

	References

Top Abstract Materials and Methods Results Discussion References

 

1. Adams ME, Butler MH, Dwyer TM, Peters MF, Murnane AA & Froehner SC. Two forms of mouse syntrophin, a 58 kd dystrophin-associated protein, differ in primary structure and tissue distribution, Neuron, 1993, 11, 531–540.[Medline]
2. Adams ME, Dwyer TM, Dowler LL, White RA & Froehner SC. Mouse 1- and β2-syntrophin gene structure, chromosome localization, and homology with a discs large domain, J Biol Chem, 1995, 270, 25859–25865.[Abstract/Free Full Text]
3. Ahn AH & Kunkel LM. The structural and functional diversity of dystrophin, Nat Genet, 1993, 3, 283–291.[Medline]
4. Ahn AH & Kunkel LM. Syntrophin binds to an alternatively spliced exon of dystrophin, J Cell Biol, 1995, 128, 363–371.[Abstract/Free Full Text]
5. Ahn AH, Yoshida M, Anderson MS, Feener CA, Selig S, Hagiwara Y, Ozawa E & Kunkel LM. Cloning of human basic A1, a distinct 59-kDa dystrophin-associated protein encoded on chromosome 8q23-24, Proc Natl Acad Sci USA, 1994, 91, 4446–4450.[Abstract/Free Full Text]
6. Ahn AH, Feener CA, Gussoni E, Yoshida M, Ozawa E & Kunkel LM. The three human syntrophin genes are expressed in diverse tissues, have distinct chromosomal locations, and each bind to dystrophin and its relatives, J Biol Chem, 1996, 271, 2724–2730.[Abstract/Free Full Text]
7. Blake DJ, Tinsley JM, Davies KE, Knight AE, Winder SJ & Kendrick-Jones J. Coiled-coil regions in the carboxy-terminal domains of dystrophin and related proteins: potentials for protein-protein interactions, Trends Biochem Sci, 1995, 20, 133–135.[Medline]
8. Blake DJ, Nawrotzki R, Peters MF, Froehner SC & Davies KE. Isoform diversity of dystrobrevin, the murine 87-kDa postsynaptic protein, J Biol Chem, 1996, 271, 7802–7810.[Abstract/Free Full Text]
9. Brenman JE, Chao DS, Xia H, Aldape K & Bredt DS. Nitric oxide synthase complexed with dystrophin and absent from skeletal muscle sarcolemma in Duchenne muscular dystrophy, Cell, 1995, 82, 743–752.[Medline]
10. Brenman JE, Chao DS, Gee SH, McGee AW, Craven SE, Santillano DR, Wu Z, Huang F, Xia H, Peters MF et al.. Interaction of nitric oxide synthase with the postsynaptic density protein PSD-95 and 1-syntrophin mediated by PDZ domains, Cell, 1996, 84, 757–767.[Medline]
11. Butler MH, Douville K, Murnane AA, Kramarcy NR, Cohen JB, Sealock R & Froehner SC. Association of the Mr 58,000 postsynaptic protein of electric tissue with Torpedodystrophin and the Mr 87,000 postsynaptic protein, J Biol Chem, 1992, 267, 6213–6218.[Abstract/Free Full Text]
12. Carr C, Fischbach GD & Cohen JB. A novel 87,000-Mr protein associated with acetylcholine receptors in Torpedoelectric organ and vertebrate skeletal muscle, J Cell Biol, 1989, 109, 1753–1764.[Abstract/Free Full Text]
13. Chomczynski P, Sacchi N & Harrison SC. Single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction, Anal Biochem, 1987, 162, 156–159.[Medline]
14. Cohen NA, Brenman JE, Synder SH & Bredt DS. Binding of the inward rectifier K+ channel Kir 2.3 to PSD-95 is regulated by protein kinase A phosphorylation, Neuron, 1996, 17, 759–767.[Medline]
15. Dwyer TM & Froehner SC. Direct binding of Torpedosyntrophin to dystrophin and the 87 kDa dystrophin homologue, FEBS (Fed Eur Biochem Sci) Lett, 1995, 375, 91–94.
16. Ervasti JM & Campbell KP. Membrane organization of the dystrophin-glycoprotein complex, Cell, 1991, 66, 1121–1131.[Medline]
17. Froehner SC, Murnane AA, Tobler M, Peng HB & Sealock R. A postsynaptic Mr 58,000 (58K) protein concentrated at acetylcholine receptor–rich sites in Torpedoelectroplaques and skeletal muscle, J Cell Biol, 1987, 104, 1633–1646.[Abstract/Free Full Text]
18. Froehner, S.C., M.E. Adams, M.F. Peters, and S.G. Gee. 1997. Syntrophins—modular adapter proteins at the neuromuscular junction and the sarcolemma. In Cytoskeletal Regulation of Membrane Function. S.C. Froehner and V. Bennett, editors. The Rockefeller University Press, New York. 197–207.
19. Gibson TJ, Hyvonen M, Musacchio A, Saraste M & Birney E. PH domain: the first anniversary, Trends Biochem Sci, 1994, 19, 349–353.[Medline]
20. Giloh H & Sedat JW. Fluorescence microscopy: reduced photobleaching of rhodamine and fluorescein protein conjugates by n-propyl gallate, Science (Wash DC), 1982, 217, 1252–1255.[Abstract/Free Full Text]
21. Henry MD & Campbell KP. Dystroglycan: an extracellular matrix receptor linked to the cytoskeleton, Curr Opin Cell Biol, 1996, 8, 625–631.[Medline]
22. Hoffman EP, Monaco AP, Feener CC & Kunkel LM. Conservation of the Duchenne muscular dystrophy gene in mice and humans, Science (Wash DC), 1987, 238, 347–350.[Abstract/Free Full Text]
23. Hoffman EP, Hudecki MS, Rosenberg PA, Pollina CM & Kunkel LM. Cell and fiber-type distribution of dystrophin, Neuron, 1988, 1, 411–420.[Medline]
24. Kim E, Cho K, Rothschild A & Sheng M. Heteromultimerization and NMDA receptor-clustering activity of chapsyn-110, a member of the PSD-95 family of proteins, Neuron, 1996, 17, 103–113.[Medline]
25. Klatt P, Schmid M, Leopold E, Schmidt K, Werner ER & Mayer B. The pteridine binding site of brain nitric oxide synthase. Tetrahydrobiopterin binding kinetics, specificity, and allosteric interaction with the substrate domain, J Biol Chem, 1994, 269, 13861–13866.[Abstract/Free Full Text]
26. Kobzik L, Reid MB, Bredt DS & Stamler JS. Nitric oxide in skeletal muscle, Nature (Lond), 1994, 372, 546–548.[Medline]
27. Kozak M. Point mutations define a sequence flanking the AUG initiator codon that modulates translation by eukaryotic ribosomes, Cell, 1986, 44, 283–292.[Medline]
28. Kramarcy NR, Vidal A, Froehner SC & Sealock R. Association of utrophin and multiple dystrophin short forms with the mammalian M(r) 58,000 dystrophin-associated protein (syntrophin), J Biol Chem, 1994, 269, 2870–2876.[Abstract/Free Full Text]
29. Lidov HG, Byers TJ, Watkins SC & Kunkel LM. Localization of dystrophin to postsynaptic regions of central nervous system cortical neurons, Nature (Lond), 1990, 348, 725–728.[Medline]
30. Luna, L.G. 1968. Manual of Histologic Staining Methods of the Armed Forces Institute of Pathology. McGraw-Hill, New York. 36–40.
31. Madhavan R & Jarrett HW. Interactions between dystrophin glycoprotein complex proteins, Biochemistry, 1995, 34, 12204–12209.[Medline]
32. McNally MN, Duggan D, Gorospe RJ, Bonnemann CG, Fanin M, Pegoraro E, Lidov HGW, Noguchi S, Ozawa E, Finkel RS et al.. Mutations that disrupt the carboxyl-terminus of delta-sarcoglycan cause muscular dystrophy, Hum Mol Genet, 1996, 5, 1841–1847.[Abstract/Free Full Text]
33. Montanaro F, Carbonetto S, Campbell KP & Lindenbaum M. Dystroglycan expression in the wild type and mdx mouse neural retina: synaptic colocalization with dystrophin, dystrophin-related protein but not laminin, J Neurosci Res, 1995, 42, 528–538.[Medline]
34. Nguyen thi M, Cartwright AJ, Morris GE, Love DR, Bloomfield JF & Davies KE. Monoclonal antibodies against defined regions of the muscular dystrophy protein, dystrophin, FEBS (Fed Eur Biochem Sci) Lett, 1990, 262, 237–240.
35. Nigro V, Piluso P, Belsito A, Politano L, Puca AA, Papparella S, Rossi E, Viglietto G, Esposito MG, Abbondanza C et al.. Identification of a novel sarcoglycan gene at 5q33 encoding a sarcolemmal 35 kDa glycoprotein, Hum Mol Genet, 1996, 5, 1179–1186.[Abstract/Free Full Text]
36. Ousley AH & Froehner SC. An anti-peptide antibody specific for the class A calcium channel 1 subunit labels mammalian neuromuscular junction, Proc Natl Acad Sci USA, 1994, 91, 12263–12267.[Abstract/Free Full Text]
37. Ozawa E, Yoshida M, Suzuki A, Mizuno Y, Hagiwara Y & Noguchi S. Dystrophin-associated proteins in muscular dystrophy, Hum Mol Genet, 1995, 4, 1711–1716.[Abstract]
38. Peters MF, Kramarcy NR, Sealock R & Froehner SC. β2-Syntrophin: localization at the neuromuscular junction in skeletal muscle, Neuroreport, 1994, 5, 1577–1580.[Medline]
39. Rafael JA, Sunada Y, Cole NM, Campbell KP, Faulkner JA & Chamberlain JS. Prevention of dystrophic pathology in mdxmice by a truncated dystrophin isoform, Hum Mol Genet, 1994, 3, 1725–1733.[Abstract/Free Full Text]
40. Rafael JA, Cox GA, Corrado K, Jung D, Campbell KP & Chamberlain JS. Forced expression of dystrophin deletion constructs reveals structure-function correlations, J Cell Biol, 1996, 134, 93–102.[Abstract/Free Full Text]
41. Sadoulet-Puccio HM, Khurana TS, Cohen JB & Kunkel LM. Cloning and characterization of the human homologue of a dystrophin related phosphoprotein found at the Torpedoelectric organ post-synaptic membrane, Hum Mol Genet, 1996, 5, 489–496.[Abstract/Free Full Text]
42. Sato T, Irie S, Kitada S & Reed J. FAP-1: a protein tyrosine phosphatase that associates with Fas, Science (Wash DC), 1995, 268, 411–415.[Abstract/Free Full Text]
43. Schagger H & von Jagow G. Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the separation of proteins in the range from 1 to 100 kDa, Anal Biochem, 1987, 166, 368–379.[Medline]
44. Schiaffino S, Gorza L, Sartore S, Saggin L, Ausoni S, Vianello M, Gundersen K & Lomo T. Three myosin heavy chain isoforms in type 2 skeletal muscle fibres, J Musc Res Cell Motil, 1989, 10, 197–205.[Medline]
45. Schmitz F, Holbach M & Drenckhahn D. Colocalization of retinal dystrophin and actin in postsynaptic dendrites of rod and cone photoreceptor synapses, Histochemistry, 1993, 100, 473–479.[Medline]
46. Sealock R & Froehner SC. Dystrophin-associated proteins and synapse formation: is -dystroglycan the agrin receptor? , Cell, 1994, 77, 617–619.[Medline]
47. Shaw G. The pleckstrin homology domain: an intriguing multifunctional protein module, Bioessays, 1996, 18, 35–46.[Medline]
48. Sheng M. PDZs and receptor/channel clustering: rounding up the latest suspects, Neuron, 1996, 17, 575–578.[Medline]
49. Songyang Z, Fanning AS, Fu C, Xu J, Marfatia SM, Chishti AH, Crompton A, Chan AC, Anderson JM & Cantley LC. Recognition of unique carboxyl-terminal motifs by distinct PDZ domains, Science (Wash DC), 1997, 275, 73–77.[Abstract/Free Full Text]
50. Suzuki A, Yoshida M & Ozawa E. Mammalian 1- and β1-syntrophin bind to the alternative splice-prone region of the dystrophin COOH terminus, J Cell Biol, 1995, 128, 373–381.[Abstract/Free Full Text]
51. Wagner KR, Cohen JB & Huganir RL. The 87K postsynaptic membrane protein from Torpedois a protein-tyrosine kinase substrate homologous to dystrophin, Neuron, 1993, 10, 511–522.[Medline]
52. Webster C, Silberstein L, Hays AP & Blau HM. Fast muscle fibers are preferentially affected in Duchenne muscular dystrophy, Cell, 1988, 52, 503–513.[Medline]
53. Yamamoto H, Mizuno Y, Hayashi K, Nonaka I, Yoshida M & Ozawa E. Expression of dystrophin-associated protein 35DAG (A4) and 50DAG (A2) is confined to striated muscles, J Biochem, 1994, 115, 162–167.[Abstract/Free Full Text]
54. Yang B, Ibraghimov-Beskrovnaya O, Moomaw CR, Slaughter CA & Campbell KP. Heterogeneity of the 59-kDa dystrophin-associated protein revealed by cDNA cloning and expression, J Biol Chem, 1994, 269, 6040–6044.[Abstract/Free Full Text]
55. Yang B, Jung D, Rafael JA, Chamberlain JS & Campbell KP. Identification of -syntrophin binding to syntrophin triplet, dystrophin, and utrophin, J Biol Chem, 1995, 270, 4975–4978.[Abstract/Free Full Text]
56. Yoshida M & Ozawa E. Glycoprotein complex anchoring dystrophin to sarcolemma, J Biochem, 1990, 108, 748–752.[Abstract/Free Full Text]
57. Yoshida M, Suzuki A, Yamamoto H, Noguchi S, Mizuno Y & Ozawa E. Dissociation of the complex of dystrophin and its associated proteins into several unique groups by n-octyl β-D-glucoside, Eur J Biochem, 1994, 222, 1055–1061.[Medline]
58. Yoshida M, Yamamoto H, Noguchi S, Mizuno Y, Hagiwara Y & Ozawa E. Dystrophin-associated protein A0 is a homologue of the Torpedo87K protein, FEBS (Fed Eur Biochem Sci) Lett, 1995, 367, 311–314.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Facebook

Reddit

Technorati

Twitter

This article has been cited by other articles:

• Li, D., Long, C., Yue, Y., Duan, D. (2009). Sub-physiological sarcoglycan expression contributes to compensatory muscle protection in mdx mice. Hum Mol Genet 18: 1209-1220 [Abstract] [Full Text]  
• Lyssand, J. S., DeFino, M. C., Tang, X.-b., Hertz, A. L., Feller, D. B., Wacker, J. L., Adams, M. E., Hague, C. (2008). Blood Pressure Is Regulated by an {alpha}1D-Adrenergic Receptor/Dystrophin Signalosome. J. Biol. Chem. 283: 18792-18800 [Abstract] [Full Text]  
• Adams, M. E., Tesch, Y., Percival, J. M., Albrecht, D. E., Conhaim, J. I., Anderson, K., Froehner, S. C. (2008). Differential targeting of nNOS and AQP4 to dystrophin-deficient sarcolemma by membrane-directed {alpha}-dystrobrevin. J. Cell Sci. 121: 48-54 [Abstract] [Full Text]  
• Vandebrouck, A., Sabourin, J., Rivet, J., Balghi, H., Sebille, S., Kitzis, A., Raymond, G., Cognard, C., Bourmeyster, N., Constantin, B. (2007). Regulation of capacitative calcium entries by {alpha}1-syntrophin: association of TRPC1 with dystrophin complex and the PDZ domain of {alpha}1-syntrophin. FASEB J. 21: 608-617 [Abstract] [Full Text]  
• Frydenlund, D. S., Bhardwaj, A., Otsuka, T., Mylonakou, M. N., Yasumura, T., Davidson, K. G. V., Zeynalov, E., Skare, O., Laake, P., Haug, F.-M., Rash, J. E., Agre, P., Ottersen, O. P., Amiry-Moghaddam, M. (2006). Temporary loss of perivascular aquaporin-4 in neocortex after transient middle cerebral artery occlusion in mice. Proc. Natl. Acad. Sci. USA 103: 13532-13536 [Abstract] [Full Text]  
• Williams, J. C., Armesilla, A. L., Mohamed, T. M. A., Hagarty, C. L., McIntyre, F. H., Schomburg, S., Zaki, A. O., Oceandy, D., Cartwright, E. J., Buch, M. H., Emerson, M., Neyses, L. (2006). The Sarcolemmal Calcium Pump, {alpha}-1 Syntrophin, and Neuronal Nitric-oxide Synthase Are Parts of a Macromolecular Protein Complex. J. Biol. Chem. 281: 23341-23348 [Abstract] [Full Text]  
• Slater, C. R., Fawcett, P. R. W., Walls, T. J., Lyons, P. R., Bailey, S. J., Beeson, D., Young, C., Gardner-Medwin, D. (2006). Pre- and post-synaptic abnormalities associated with impaired neuromuscular transmission in a group of patients with 'limb-girdle myasthenia'.. Brain 129: 2061-2076 [Abstract] [Full Text]  
• Mercado, M. L., Amenta, A. R., Hagiwara, H., Rafii, M. S., Lechner, B. E., Owens, R. T., McQuillan, D. J., Froehner, S. C., Fallon, J. R. (2006). Biglycan regulates the expression and sarcolemmal localization of dystrobrevin, syntrophin, and nNOS. FASEB J. 20: 1724-1726 [Abstract] [Full Text]  
• Li, S., Kimura, E., Ng, R., Fall, B. M., Meuse, L., Reyes, M., Faulkner, J. A., Chamberlain, J. S. (2006). A highly functional mini-dystrophin/GFP fusion gene for cell and gene therapy studies of Duchenne muscular dystrophy. Hum Mol Genet 15: 1610-1622 [Abstract] [Full Text]  
• Chen, Z., Hague, C., Hall, R. A., Minneman, K. P. (2006). Syntrophins Regulate {alpha}1D-Adrenergic Receptors through a PDZ Domain-mediated Interaction. J. Biol. Chem. 281: 12414-12420 [Abstract] [Full Text]  
• Judge, L. M., Haraguchiln, M., Chamberlain, J. S. (2006). Dissecting the signaling and mechanical functions of the dystrophin-glycoprotein complex. J. Cell Sci. 119: 1537-1546 [Abstract] [Full Text]  
• Okuhira, K.-i., Fitzgerald, M. L., Sarracino, D. A., Manning, J. J., Bell, S. A., Goss, J. L., Freeman, M. W. (2005). Purification of ATP-binding Cassette Transporter A1 and Associated Binding Proteins Reveals the Importance of {beta}1-Syntrophin in Cholesterol Efflux. J. Biol. Chem. 280: 39653-39664 [Abstract] [Full Text]  
• Luo, S., Chen, Y., Lai, K.-O., Arevalo, J. C., Froehner, S. C., Adams, M. E., Chao, M. V., Ip, N. Y. (2005). {alpha}-Syntrophin regulates ARMS localization at the neuromuscular junction and enhances EphA4 signaling in an ARMS-dependent manner. JCB 169: 813-824 [Abstract] [Full Text]  
• Hogan, A., Yakubchyk, Y., Chabot, J., Obagi, C., Daher, E., Maekawa, K., Gee, S. H. (2004). The Phosphoinositol 3,4-Bisphosphate-binding Protein TAPP1 Interacts with Syntrophins and Regulates Actin Cytoskeletal Organization. J. Biol. Chem. 279: 53717-53724 [Abstract] [Full Text]  
• Adams, M. E., Kramarcy, N., Fukuda, T., Engel, A. G., Sealock, R., Froehner, S. C. (2004). Structural Abnormalities at Neuromuscular Synapses Lacking Multiple Syntrophin Isoforms. J. Neurosci. 24: 10302-10309 [Abstract] [Full Text]  
• Leonoudakis, D., Conti, L. R., Anderson, S., Radeke, C. M., McGuire, L. M. M., Adams, M. E., Froehner, S. C., Yates, J. R. III, Vandenberg, C. A. (2004). Protein Trafficking and Anchoring Complexes Revealed by Proteomic Analysis of Inward Rectifier Potassium Channel (Kir2.x)-associated Proteins. J. Biol. Chem. 279: 22331-22346 [Abstract] [Full Text]  
• Munehira, Y., Ohnishi, T., Kawamoto, S., Furuya, A., Shitara, K., Imamura, M., Yokota, T., Takeda, S., Amachi, T., Matsuo, M., Kioka, N., Ueda, K. (2004). {alpha}1-Syntrophin Modulates Turnover of ABCA1. J. Biol. Chem. 279: 15091-15095 [Abstract] [Full Text]  
• Albrecht, D. E., Froehner, S. C. (2004). DAMAGE, a Novel {alpha}-Dystrobrevin-associated MAGE Protein in Dystrophin Complexes. J. Biol. Chem. 279: 7014-7023 [Abstract] [Full Text]  
• Macioce, P., Gambara, G., Bernassola, M., Gaddini, L., Torreri, P., Macchia, G., Ramoni, C., Ceccarini, M., Petrucci, T. C. (2003). {beta}-Dystrobrevin interacts directly with kinesin heavy chain in brain. J. Cell Sci. 116: 4847-4856 [Abstract] [Full Text]  
• Abramovici, H., Hogan, A. B., Obagi, C., Topham, M. K., Gee, S. H. (2003). Diacylglycerol Kinase-{zeta} Localization in Skeletal Muscle Is Regulated by Phosphorylation and Interaction with Syntrophins. Mol. Biol. Cell 14: 4499-4511 [Abstract] [Full Text]  
• Martin, P. T. (2003). Dystroglycan glycosylation and its role in matrix binding in skeletal muscle. Glycobiology 13: 55R-66R [Abstract] [Full Text]  
• Khanna, S., Richmonds, C. R., Kaminski, H. J., Porter, J. D. (2003). Molecular Organization of the Extraocular Muscle Neuromuscular Junction: Partial Conservation of and Divergence from the Skeletal Muscle Prototype. IOVS 44: 1918-1926 [Abstract] [Full Text]  
• Michele, D. E., Campbell, K. P. (2003). Dystrophin-Glycoprotein Complex: Post-translational Processing and Dystroglycan Function. J. Biol. Chem. 278: 15457-15460 [Full Text]  
• Ebert, J. G., Zelenka, M., Gath, I., Godtel-Armbrust, U., Forstermann, U. (2003). Colocalization but differential regulation of neuronal NO synthase and nicotinic acetylcholine receptor in C2C12 myotubes. Am. J. Physiol. Cell Physiol. 284: C1065-C1072 [Abstract] [Full Text]  
• Thomas, G. D., Shaul, P. W., Yuhanna, I. S., Froehner, S. C., Adams, M. E. (2003). Vasomodulation by Skeletal Muscle-Derived Nitric Oxide Requires {alpha}-Syntrophin-Mediated Sarcolemmal Localization of Neuronal Nitric Oxide Synthase. Circ. Res. 92: 554-560 [Abstract] [Full Text]  
• Bailey, S. J., Stocksley, M. A., Buckel, A., Young, C., Slater, C. R. (2003). Voltage-Gated Sodium Channels and AnkyrinG Occupy a Different Postsynaptic Domain from Acetylcholine Receptors from an Early Stage of Neuromuscular Junction Maturation in Rats. J. Neurosci. 23: 2102-2111 [Abstract] [Full Text]  
• Grady, R. M., Akaaboune, M., Cohen, A. L., Maimone, M. M., Lichtman, J. W., Sanes, J. R. (2003). Tyrosine-phosphorylated and nonphosphorylated isoforms of {alpha}-dystrobrevin: roles in skeletal muscle and its neuromuscular and myotendinous junctions. JCB 160: 741-752 [Abstract] [Full Text]  
• Ou, Y., Strege, P., Miller, S. M., Makielski, J., Ackerman, M., Gibbons, S. J., Farrugia, G. (2003). Syntrophin gamma 2 Regulates SCN5A Gating by a PDZ Domain-mediated Interaction. J. Biol. Chem. 278: 1915-1923 [Abstract] [Full Text]  
• Hosaka, Y., Yokota, T., Miyagoe-Suzuki, Y., Yuasa, K., Imamura, M., Matsuda, R., Ikemoto, T., Kameya, S., Takeda, S.'i. (2002). {alpha}1-Syntrophin-deficient skeletal muscle exhibits hypertrophy and aberrant formation of neuromuscular junctions during regeneration. JCB 158: 1097-1107 [Abstract] [Full Text]  
• Rybakova, I. N., Patel, J. R., Davies, K. E., Yurchenco, P. D., Ervasti, J. M. (2002). Utrophin Binds Laterally along Actin Filaments and Can Couple Costameric Actin with Sarcolemma When Overexpressed in Dystrophin-deficient Muscle. Mol. Biol. Cell 13: 1512-1521 [Abstract] [Full Text]  
• Blake, D. J., Weir, A., Newey, S. E., Davies, K. E. (2002). Function and Genetics of Dystrophin and Dystrophin-Related Proteins in Muscle. Physiol. Rev. 82: 291-329 [Abstract] [Full Text]  
• Neely, J. D., Amiry-Moghaddam, M., Ottersen, O. P., Froehner, S. C., Agre, P., Adams, M. E. (2001). Syntrophin-dependent expression and localization of Aquaporin-4 water channel protein. Proc. Natl. Acad. Sci. USA 98: 14108-14113 [Abstract] [Full Text]  
• Stamler, J. S., Meissner, G. (2001). Physiology of Nitric Oxide in Skeletal Muscle. Physiol. Rev. 81: 209-237 [Abstract] [Full Text]  
• Adams, M. E., Kramarcy, N., Krall, S. P., Rossi, S. G., Rotundo, R. L., Sealock, R., Froehner, S. C. (2000). Absence of {alpha}-Syntrophin Leads to Structurally Aberrant Neuromuscular Synapses Deficient in Utrophin. JCB 150: 1385-1398 [Abstract] [Full Text]  
• Crawford, G. E., Faulkner, J. A., Crosbie, R. H., Campbell, K. P., Froehner, S. C., Chamberlain, J. S. (2000). Assembly of the Dystrophin-Associated Protein Complex Does Not Require the Dystrophin Cooh-Terminal Domain. JCB 150: 1399-1410 [Abstract] [Full Text]  
• Rafael, J. A., Townsend, E. R., Squire, S. E., Potter, A. C., Chamberlain, J. S., Davies, K. E. (2000). Dystrophin and utrophin influence fiber type composition and post-synaptic membrane structure. Hum Mol Genet 9: 1357-1367 [Abstract] [Full Text]  
• Claudepierre, T, Dalloz, C, Mornet, D, Matsumura, K, Sahel, J, Rendon, A (2000). Characterization of the intermolecular associations of the dystrophin-associated glycoprotein complex in retinal Muller glial cells. J. Cell Sci. 113: 3409-3417 [Abstract]  
• Loh, N., Newey, S., Davies, K., Blake, D. (2000). Assembly of multiple dystrobrevin-containing complexes in the kidney. J. Cell Sci. 113: 2715-2724 [Abstract]  
• Durbeej, M., Campbell, K. P. (1999). Biochemical Characterization of the Epithelial Dystroglycan Complex. J. Biol. Chem. 274: 26609-26616 [Abstract] [Full Text]  
• Wilson, J., Putt, W., Jimenez, C., Edwards, Y. H. (1999). Up71 and Up140, two novel transcripts of utrophin that are homologues of short forms of dystrophin. Hum Mol Genet 8: 1271-1278 [Abstract] [Full Text]  
• Hasegawa, M., Cuenda, A., Spillantini, M. G., Thomas, G. M., Buee-Scherrer, V., Cohen, P., Goedert, M. (1999). Stress-activated Protein Kinase-3 Interacts with the PDZ Domain of alpha 1-Syntrophin. A MECHANISM FOR SPECIFIC SUBSTRATE RECOGNITION. J. Biol. Chem. 274: 12626-12631 [Abstract] [Full Text]  
• Hashida-Okumura, A., Okumura, N., Iwamatsu, A., Buijs, R. M., Romijn, H. J., Nagai, K. (1999). Interaction of Neuronal Nitric-oxide Synthase with {alpha}1-Syntrophin in Rat Brain. J. Biol. Chem. 274: 11736-11741 [Abstract] [Full Text]  
• Kachinsky, A. M., Froehner, S. C., Milgram, S. L. (1999). A PDZ-containing Scaffold Related to the Dystrophin Complex at the Basolateral Membrane of Epithelial Cells. JCB 145: 391-402 [Abstract] [Full Text]  
• Kameya, S., Miyagoe, Y., Nonaka, I., Ikemoto, T., Endo, M., Hanaoka, K., Nabeshima, Y.-i., Takeda, S.'i. (1999). alpha 1-Syntrophin Gene Disruption Results in the Absence of Neuronal-type Nitric-oxide Synthase at the Sarcolemma but Does Not Induce Muscle Degeneration. J. Biol. Chem. 274: 2193-2200 [Abstract] [Full Text]  
• Huber, A., Saur, D., Kurjak, M., Schusdziarra, V., Allescher, H.-D. (1998). Characterization and splice variants of neuronal nitric oxide synthase in rat small intestine. Am. J. Physiol. Gastrointest. Liver Physiol. 275: G1146-G1156 [Abstract] [Full Text]  
• Peters, M. F., Sadoulet-Puccio, H. M., Mark Grady, R., Kramarcy, N. R., Kunkel, L. M., Sanes, J. R., Sealock, R., Froehner, S. C. (1998). Differential Membrane Localization and Intermolecular Associations of {alpha}-Dystrobrevin Isoforms in Skeletal Muscle. JCB 142: 1269-1278 [Abstract] [Full Text]  
• Nawrotzki, R, Loh, N., Ruegg, M., Davies, K., Blake, D. (1998). Characterisation of alpha-dystrobrevin in muscle. J. Cell Sci. 111: 2595-2605 [Abstract]  
• Blake, D. J., Nawrotzki, R., Loh, N. Y., Gorecki, D. C., Davies, K. E. (1998). beta -dystrobrevin, a member of the dystrophin-related protein family. Proc. Natl. Acad. Sci. USA 95: 241-246 [Abstract] [Full Text]  
• Gee, S. H., Madhavan, R., Levinson, S. R., Caldwell, J. H., Sealock, R., Froehner, S. C. (1998). Interaction of Muscle and Brain Sodium Channels with Multiple Members of the Syntrophin Family of Dystrophin-Associated Proteins. J. Neurosci. 18: 128-137 [Abstract] [Full Text]  
• Peters, M. F., O'Brien, K. F., Sadoulet-Puccio, H. M., Kunkel, L. M., Adams, M. E., Froehner, S. C. (1997). beta -Dystrobrevin, a New Member of the Dystrophin Family. IDENTIFICATION, CLONING, AND PROTEIN ASSOCIATIONS. J. Biol. Chem. 272: 31561-31569 [Abstract] [Full Text]  
• Sadoulet-Puccio, H. M., Rajala, M., Kunkel, L. M. (1997). Dystrobrevin and dystrophin: An interaction through coiled-coil motifs. Proc. Natl. Acad. Sci. USA 94: 12413-12418 [Abstract] [Full Text]  
• Piluso, G., Mirabella, M., Ricci, E., Belsito, A., Abbondanza, C., Servidei, S., Puca, A. A., Tonali, P., Puca, G. A., Nigro, V. (2000). gamma 1- and gamma 2-Syntrophins, Two Novel Dystrophin-binding Proteins Localized in Neuronal Cells. J. Biol. Chem. 275: 15851-15860 [Abstract] [Full Text]  
• Peters, M. F., Ross, C. A. (2001). Isolation of a 40-kDa Huntingtin-associated Protein. J. Biol. Chem. 276: 3188-3194 [Abstract] [Full Text]  
• McDearmon, E. L., Combs, A. C., Ervasti, J. M. (2001). Differential Vicia villosa Agglutinin Reactivity Identifies Three Distinct Dystroglycan Complexes in Skeletal Muscle. J. Biol. Chem. 276: 35078-35086 [Abstract] [Full Text]  
• Hogan, A., Shepherd, L., Chabot, J., Quenneville, S., Prescott, S. M., Topham, M. K., Gee, S. H. (2001). Interaction of gamma 1-Syntrophin with Diacylglycerol Kinase-zeta . REGULATION OF NUCLEAR LOCALIZATION BY PDZ INTERACTIONS. J. Biol. Chem. 276: 26526-26533 [Abstract] [Full Text]  
• Adams, M. E., Mueller, H. A., Froehner, S. C. (2001). In vivo requirement of the {alpha}-syntrophin PDZ domain for the sarcolemmal localization of nNOS and aquaporin-4. JCB 155: 113-122 [Abstract] [Full Text]  

This Article Abstract Full Text (PDF, 777K) PPT slides of all figures Alert me when this article is cited Citation Map Services Email this article Similar articles in this journal Similar articles in PubMed Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Peters, M. F. Articles by Froehner, S. C. Search for Related Content PubMed PubMed Citation Articles by Peters, M. F. Articles by Froehner, S. C. Social Bookmarking                            What's this?