Ral GTPases Regulate Exocyst Assembly through Dual Subunit Interactions

• Published in: The Journal of biological chemistry Vol. 278; no. 51; pp. 51743 - 51748
• Main Authors: Moskalenko, Serge, Tong, Chao, Rosse, Carine, Mirey, Gladys, Formstecher, Etienne, Daviet, Laurent, Camonis, Jacques, White, Michael A.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 19.12.2003; American Society for Biochemistry and Molecular Biology
• Subjects: Carrier Proteins - metabolism; Cell Line; Humans; Life Sciences; Macromolecular Substances; Membrane Proteins - metabolism; Other; Protein Binding; Protein Subunits - metabolism; ral GTP-Binding Proteins - metabolism; ral GTP-Binding Proteins - physiology; Secretory Vesicles - metabolism; Transfection; Vesicular Transport Proteins
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M308702200

Ral GTPases have been implicated in the regulation of a variety of dynamic cellular processes including proliferation, oncogenic transformation, actin-cytoskeletal dynamics, endocytosis, and exocytosis. Recently the Sec6/8 complex, or exocyst, a multisubunit complex facilitating post-Golgi targeting of distinct subclasses of secretory vesicles, has been identified as a bona fide Ral effector complex. Ral GTPases regulate exocyst-dependent vesicle trafficking and are required for exocyst complex assembly. Sec5, a membrane-associated exocyst subunit, has been identified as a direct target of activated Ral; however, the mechanism by which Ral can modulate exocyst assembly is unknown. Here we report that an additional component of the exocyst, Exo84, is a direct target of activated Ral. We provide evidence that mammalian exocyst components are present as distinct subcomplexes on vesicles and the plasma membrane and that Ral GTPases regulate the assembly interface of a full octameric exocyst complex through interaction with Sec5 and Exo84.