Sec3p is involved in secretion and morphogenesis in Saccharomyces cerevisiae.

Abstract

Two new temperature-sensitive alleles of SEC3, 1 of 10 late-acting SEC genes required for targeting or fusion of post-Golgi secretory vesicles to the plasma membrane in Saccharomyces cerevisiae, were isolated in a screen for temperature-sensitive secretory mutants that are synthetically lethal with sec4-8. The new sec3 alleles affect early as well as late stages of secretion. Cloning and sequencing of the SEC3 gene revealed that it is identical to profilin synthetic lethal 1 (PSL1). The SEC3 gene is not essential because cells depleted of Sec3p are viable although slow growing and temperature sensitive. All of the sec3 alleles genetically interact with a profilin mutation, pfy1-111. The SEC3 gene in high copy suppresses pfy1-111 and sec5-24 and causes synthetic growth defects with ypt1, sec8-9, sec10-2, and sec15-1. Actin structure is only perturbed in conditions of chronic loss of Sec3p function, implying that Sec3p does not directly regulate actin. All alleles of sec3 cause bud site selection defects in homozygous diploids, as do sec4-8 and sec9-4. This suggests that SEC gene products are involved in determining the bud site and is consistent with a role for Sec3p in determining the correct site of exocytosis.

The Brain Exocyst Complex Interacts with RalA in a GTP-dependent Manner

“…Sec3p in yeast may anchor the exocyst to the plasma membrane, and has been termed a "spatial landmark" for polarized secretion (33,34). We matched the peptide mass maps of a sheep brain 100-kDa protein to human FLJ10893, which has sequence similarity to yeast sec3p.…”

The Exocyst at a Glance

“…In budding yeast, mutations in the exocyst subunits lead to accumulation of post-Golgi secretory vesicles in the cytoplasm (Novick, et al, 1980;Finger and Novick, 1997;Guo et al, 1999b;He et al, 2007a,b). The exocyst is localized to the emerging bud tip, where it mediates exocytosis for the asymmetric expansion of daughter cell surfaces during polarized cell growth.…”

Sec6 mutations and theDrosophilaexocyst complex

“…Mutations of each have been shown to prevent exocytosis and to arrest growth of the daughter cell and cytokinesis Novick et al, 1980). The similarities of the phenotypes and extensive biochemical characterization have led to a model in which the complex functions as an integral unit that can interact with both plasma membranes and transport vesicles, and that, as a unit, marks sites of membrane insertion Finger and Novick, 1997;Haarer et al, 1996;Mondesert et al, 1997).…”