The role of Myo2, a yeast class V myosin, in vesicular transport.
Previous studies have shown that temperature-sensitive, myo2-66 yeast arrest as large, unbudded cells that accumulate vesicles within their cytoplasm (Johnston, G. C., J. A. Prendergast, and R. A. Singer. 1991. J. Cell Biol. 113:539-551). In this study we show that myo2-66 is synthetically lethal in combination with a subset of the late-acting sec mutations. Thin section electron microscopy shows that the post-Golgi blocked secretory mutants, sec1-1 and sec6-4, rapidly accumulate vesicles in the bud, upon brief incubations at the restrictive temperature. In contrast, myo2-66 cells accumulate vesicles predominantly in the mother cell. Double mutant analysis also places Myo2 function in a post-Golgi stage of the secretory pathway. Despite the accumulation of vesicles in myo2-66 cells, pulse-chase studies show that the transit times of several secreted proteins, including invertase and alpha factor, as well as the vacuolar proteins, carboxy-peptidase Y and alkaline phosphatase, are normal. Therefore the vesicles which accumulate in this mutant may function on an exocytic pathway that transports a set of cargo proteins that is distinct from those analyzed. Our observations are consistent with a role for Myo2 in transporting a class of secretory vesicles from the mother cell along actin cables into the bud.
Govindan
B
B
Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut 06520-8002.
Bowser
R
R
Novick
P
P
D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003594:Cytoplasmic Granules / Q000378:metabolism* / Q000648:ultrastructure; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D008854:Microscopy, Electron; D009154:Mutation; D018995:Myosin Heavy Chains; D024462:Myosin Type II; D024701:Myosin Type V; D012441:Saccharomyces cerevisiae / Q000378:metabolism* / Q000648:ultrastructure; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins
D002352:Carrier Proteins; D005656:Fungal Proteins; C077512:MYO2 protein, S cerevisiae; C434211:MYO2 protein, S pombe; D029701:Saccharomyces cerevisiae Proteins; D029702:Schizosaccharomyces pombe Proteins; D024462:Myosin Type II; D024701:Myosin Type V; D018995:Myosin Heavy Chains