Journal
MOLECULAR BIOLOGY OF THE CELL
Volume 19, Issue 10, Pages 4177-4187Publisher
AMER SOC CELL BIOLOGY
DOI: 10.1091/mbc.E08-02-0220
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Funding
- National Institutes of Health [GM-45444, GM-62261]
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [R01GM045444, R37GM062261, R01GM062261] Funding Source: NIH RePORTER
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Rab GTPases recruit myosin motors to endocytic compartments, which in turn are required for their motility. However, no Ypt/Rab GTPase has been shown to regulate the motility of exocytic compartments. In yeast, the Ypt31/32 functional pair is required for the formation of trans-Golgi vesicles. The myosin V motor Myo2 attaches to these vesicles through its globular-tail domain (GTD) and mediates their polarized delivery to sites of cell growth. Here, we identify Myo2 as an effector of Ypt31/32 and show that the Ypt31/32-Myo2 interaction is required for polarized secretion. Using the yeast-two hybrid system and coprecipitation of recombinant proteins, we show that Ypt31/32 in their guanosine triphosphate (GTP)-bound form interact directly with Myo2-GTD. The physiological relevance of this interaction is shown by colocalization of the proteins, genetic interactions between their genes, and rescue of the lethality caused by a mutation in the Ypt31/32-binding site of Myo2-GTD through fusion with Ypt32. Furthermore, microscopic analyses show a defective Myo2 intracellular localization in ypt31 Delta/32ts and in Ypt31/32-interaction-deficient myo2 mutant cells, as well as accumulation of unpolarized secretory vesicles in the latter mutant cells. Together, these results indicate that Ypt31/32 play roles in both the formation of trans-Golgi vesicles and their subsequent Myo2-dependent motility.
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