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Vol. 18, Issue 11, 4483-4492, November 2007

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Phosphatidylinositol 4,5-Bisphosphate Mediates the Targeting of the Exocyst to the Plasma Membrane for Exocytosis in Mammalian Cells

Department of Biology, University of Pennsylvania, Philadelphia, PA 19104-6018

Submitted May 17, 2007; Revised August 14, 2007; Accepted August 17, 2007
Monitoring Editor: Tom U. Martin

The exocyst is an evolutionarily conserved octameric protein complex that tethers post-Golgi secretory vesicles at the plasma membrane for exocytosis. To elucidate the mechanism of vesicle tethering, it is important to understand how the exocyst physically associates with the plasma membrane (PM). In this study, we report that the mammalian exocyst subunit Exo70 associates with the PM through its direct interaction with phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂). Furthermore, we have identified key conserved residues at the C-terminus of Exo70 that are crucial for the interaction of Exo70 with PI(4,5)P₂. Disrupting Exo70-PI(4,5)P₂ interaction abolished the membrane association of Exo70. We have also found that wild-type Exo70 but not the PI(4,5)P₂-binding–deficient Exo70 mutant is capable of recruiting other exocyst components to the PM. Using the ts045 vesicular stomatitis virus glycoprotein trafficking assay, we demonstrate that Exo70-PI(4,5)P₂ interaction is critical for the docking and fusion of post-Golgi secretory vesicles, but not for their transport to the PM.

The online version of this article contains supplemental material at MBC Online (http://www.molbiolcell.org).

* These authors contributed equally to this work.

Address correspondence to: Wei Guo (guowei{at}sas.upenn.edu)

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