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J. Cell Biol.,
Volume 140, Number 4, February 23, 1998 779-793
* Center for Basic Research in Digestive Diseases and Department of Biochemistry and Molecular Biology, Mayo Clinic and
Foundation, Rochester, Minnesota 55905; and Abstract. Dynamins are 100-kilodalton guanosine
triphosphatases that participate in the formation of nascent vesicles during endocytosis. Here, we have tested
if novel dynamin-like proteins are expressed in mammalian cells to support vesicle trafficking processes at
cytoplasmic sites distinct from the plasma membrane. Immunological and molecular biological methods were
used to isolate a cDNA clone encoding an 80-kilodalton novel dynamin-like protein, DLP1, that shares up
to 42% homology with other dynamin-related proteins.
DLP1 is expressed in all tissues examined and contains two alternatively spliced regions that are differentially
expressed in a tissue-specific manner. DLP1 is enriched
in subcellular membrane fractions of cytoplasmic vesicles and endoplasmic reticulum. Morphological studies
of DLP1 in cultured cells using either a specific antibody or an expressed green fluorescent protein (GFP)-
DLP1 fusion protein revealed that DLP1 associates
with punctate cytoplasmic vesicles that do not colocalize with conventional dynamin, clathrin, or endocytic
ligands. Remarkably, DLP1-positive structures coalign with microtubules and, most strikingly, with endoplasmic reticulum tubules as verified by double labeling with
antibodies to calnexin and Rab1 as well as by immunoelectron microscopy. These observations provide the first
evidence that a novel dynamin-like protein is expressed
in mammalian cells where it associates with a secretory, rather than endocytic membrane compartment.
Department of Anatomy and Cell Biology, McGill University, Montreal,
Quebec, Canada H3A 2B2
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