Zhang X, et al. (2005) The critical role of Exo84p in the organization and polarized localization of the exocyst complex. J Biol Chem 280(21):20356-64
Abstract: The exocyst complex plays an essential role in tethering secretory vesicles at specific domains of the plasma membrane for exocytosis. However, how the exocyst complex is assembled and targeted to sites of secretion is unclear. Here we have investigated the role of the exocyst component, Exo84p, in these processes. We have generated an array of yeast exo84 temperature-sensitive mutants. Electron microscopy and cargo protein traffic analyses in these mutants indicate that Exo84p is specifically involved in the post-Golgi stage of secretion. Making use of various yeast mutants, we have systematically studied the localization of Exo84p and other exocyst proteins using fluorescence microscopy. We found that pre-Golgi traffic and polarized actin organization are required for Exo84p localization. However, none of the exocyst proteins controls Exo84p polarization. Sec3p, though a spatial landmark for exocytosis, is not responsible for the polarization of Exo84p or any other exocyst components to the daughter cell. On the other hand, several exocyst members including Sec10p, Sec15p, and Exo70p clearly require Exo84p for their polarization. Biochemical analyses of the exocyst composition indicate that the assembly of Sec10p, Sec15p, and Exo70p with the rest of the complex requires Exo84p. We propose that there are at least two distinct regulatory mechanisms for the exocyst polarization, one for Sec3p, and one for the other members including Exo84p. Exo84p plays a critical role in both the assembly and the targeting of the exocyst at sites of secretion.
|Status: Published||Type: Journal Article||PubMed ID: 15788396|
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