Yeast Homologs of Lethal Giant Larvae and Type V Myosin Cooperate in the Regulation of Rab-Dependant Vesicle Clustering and Polarized Exocytosis.

Lgl family members play an important role in the regulation of cell polarity in eukaryotic cells. The yeast homologues, Sro7 and Sro77, are thought to act downstream of the Rab GTPase Sec4, to promote SNARE function in post-Golgi transport. In this paper, we characterize the interaction between Sro7 and the ...
type V myosin, Myo2, and show that this interaction is important for two distinct aspects of Sro7 function. First, we show that this interaction plays a positive role in promoting the polarized localization of Sro7 to sites of active growth. Second, we find evidence that Myo2 negatively regulates Sro7 function in vesicle clustering. Mutants in either Myo2 or Sro7 that are defective for this interaction show hypersensitivity to Sro7 over-expression which results in Sec4-dependent accumulation of large groups of vesicles in the cytoplasm. This suggests that Myo2 serves a dual function, to both recruit Sro7 to secretory vesicles and inhibit its Rab-dependent tethering activity until vesicles reach the plasma membrane. Thus, Sro7 appears to coordinate the spatial and temporal nature of both Rab-dependent tethering and SNARE-dependent membrane fusion of exocytic vesicles with the plasma membrane.
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Date: Jan. 19, 2011
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