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Vol. 19, Issue 10, 4177-4187, October 2008

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Direct Interaction between a Myosin V Motor and the Rab GTPases Ypt31/32 Is Required for Polarized Secretion

Zhanna Lipatova^*,, Andrei A. Tokarev^*,, Yui Jin, Jon Mulholland, Lois S. Weisman, and Nava Segev^*

*Laboratory for Molecular Biology, Department of Biological Sciences, University of Illinois at Chicago, Chicago, IL 60607; Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109; and Cell Sciences Imaging Facility, Beckman Center, Stanford University School of Medicine, Stanford, CA 94305-5301

Submitted February 28, 2008; Revised June 10, 2008; Accepted July 16, 2008
Monitoring Editor: Patrick J. Brennwald

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 ypt31/32ts 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.

These authors contributed equally to this work.

Address correspondence to: Nava Segev (nava{at}uic.edu)

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