Published 18 July 2005. doi:10.1083/jcb.200502055
The Rockefeller University Press, 0021-9525 $8.00
JCB, Volume 170, Number 2, 273-283
Lethal giant larvae proteins interact with the exocyst complex and are involved in polarized exocytosis
Xiaoyu Zhang1,
Puyue Wang1,
Akanksha Gangar2,
Jian Zhang1,
Patrick Brennwald2,
Daniel TerBush3, and
Wei Guo1
1 Department of Biology, University of Pennsylvania, Philadelphia, PA 19104
2 Department of Cell and Developmental Biology, University of North Carolina, Chapel Hill, NC 27599
3 Department of Biochemistry, Uniformed Services University of Health Sciences, Bethesda, MD 20814
Correspondence to Wei Guo: guowei{at}sas.upenn.edu
The tumor suppressor lethal giant larvae (Lgl) plays a critical role in epithelial cell polarization. However, the molecular mechanism by which Lgl carries out its functions is unclear. In this study, we report that the yeast Lgl proteins Sro7p and Sro77p directly interact with Exo84p, which is a component of the exocyst complex that is essential for targeting vesicles to specific sites of the plasma membrane for exocytosis, and that this interaction is important for post-Golgi secretion. Genetic analyses demonstrate a molecular pathway from Rab and Rho GTPases through the exocyst and Lgl to SNAREs, which mediate membrane fusion. We also found that overexpression of Lgl and t-SNARE proteins not only improves exocytosis but also rescues polarity defects in exocyst mutants. We propose that, although Lgl is broadly distributed in the cells, its localized interaction with the exocyst and kinetic activation are important for the establishment and reenforcement of cell polarity.
X. Zhang and P. Wang contributed equally to this work.
Abbreviations used in this paper: Lgl, lethal giant larvae; SC, synthetic complete media.

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