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© The Rockefeller University Press,
0021-9525/1998//735 $5.00
The Journal of Cell Biology, Volume 142, Number 3,
, 1998 735-750
Regular Articles |
Interaptin, an Actin-binding Protein of the
-Actinin Superfamily in Dictyostelium discoideum, Is Developmentally and cAMP-regulated and Associates with Intracellular Membrane Compartments



Institut für Biochemie I, Medizinische Fakultät, Universität zu Köln, 50931 Köln, Germany; and
Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030
In a search for novel members of the
-actinin superfamily, a Dictyostelium discoideum genomic library in yeast artificial chromosomes (YAC) was screened under low stringency conditions using the acting-binding domain of the gelation factor as probe. A new locus was identified and 8.6 kb of genomic DNA were sequenced that encompassed the whole abpD gene. The DNA sequence predicts a protein, interaptin, with a calculated molecular mass of 204,300 D that is constituted by an actin-binding domain, a central coiled-coil rod domain and a membrane-associated domain. In Northern blot analyses a cAMP-stimulated transcript of 5.8 kb is expressed at the stage when cell differentiation occurs. Monoclonal antibodies raised against bacterially expressed interaptin polypeptides recognized a 200-kD developmentally and cAMP-regulated protein and a 160-kD constitutively expressed protein in Western blots. In multicellular structures, interaptin appears to be enriched in anterior-like cells which sort to the upper and lower cups during culmination. The protein is located at the nuclear envelope and ER. In mutants deficient in interaptin development is delayed, but the morphology of the mature fruiting bodies appears normal. When starved in suspension abpD– cells form EDTA-stable aggregates, which, in contrast to wild type, dissociate. Based on its domains and location, interaptin constitutes a potential link between intracellular membrane compartments and the actin cytoskeleton.
Key Words: actin cytoskeleton Dictyostelium green fluorescent protein development cyclic AMP
Abbreviations used in this paper: ABD, actin-binding domain; ALC, anterior-like cells; BPAG-1, pemphigoid antigen 1; Bsr, blasticidin; DAPI, 4',6-diamidino-2-phenylindole; GSE, G-rich sequence elements; MAD, membrane-associated domain; PDI, protein disulfide isomerase; PIP2, phosphatidylinositol (4,5) bisphosphate; PVDF, polyvinylidene difluoride; YAC, yeast artificial chromosomes.
Address all correspondence to Angelika A. Noegel, Institut für Biochemie I, Medizinische Fakultät, Universität zu Köln, Joseph-Stelzmann-Str. 52, 50931 Köln, Germany. Tel.: 49 221 478 6980. Fax: 49 221 478 6979. E-mail: noegel{at}uni-koeln.de
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