High impact information on SEC8

• A functional fusion of Sec3 protein with green fluorescent protein (Sec3-GFP) localizes to the site of polarized exocytosis for each cell-cycle stage, where it colocalizes with Sec4p and Sec8p [1].
• Concurrently, we biochemically purified the remaining unidentified polypeptides of the Sec6-Sec8-Sec15 complex for peptide microsequencing [2].
• These data indicate that the Sec8/15 complex contains Sec6 as a stable component [3].
• Sec6 cofractionates with Sec8/15 by immobilized metal affinity chromatography, gel filtration chromatography, and by sucrose velocity centrifugation [3].
• Sec8p and Sec15p are components of a plasma membrane-associated 19.5S particle that may function downstream of Sec4p to control exocytosis [4].

Biological context of SEC8

• The SEC8 and SEC15 genes are essential for exocytosis in the yeast Saccharomyces cerevisiae and exhibit strong genetic interactions with SEC4, a gene of the ras superfamily [4].
• When single exocytotic events were imaged by total internal reflection fluorescence microscopy, the fluorescence of the insulin surrogate, neuropeptide Y-monomeric red fluorescent protein brightened, diffused, and then vanished with kinetics that were unaffected by overexpression of truncated SEC8 or SEC10 [5].

Anatomical context of SEC8

• Two of these genes, SEC8 and SEC15, encode components of a 1-2-million D multi-subunit complex that is found in the cytoplasm and associated with the plasma membrane [3].
• Seb1p was coimmunoprecipitated from yeast cell lysates with Sec15p and Sec8p, components of the exocyst complex, and with Sec4p, a secretory vesicle associated Rab GTPase that binds to Sec15p and is essential for exocytosis [6].
• A novel 17S complex composed of eight proteins including rsec6 and rsec8, the rat homologues of the yeast secretory proteins, Sec6p and Sec8p, has been identified in rat brain cytosol [7].

Associations of SEC8 with chemical compounds

• Here, we examined the role of the SEC6-SEC8 (exocyst) complex, implicated in trafficking of secretory vesicles to fusion sites in the plasma membrane in yeast and in regulating glucose-stimulated insulin secretion from pancreatic MIN6 beta cells [5].
• The Sec8p sequence contains a 202 amino acid region that is 25% identical to the leucine rich domain of yeast adenylate cyclase that has been implicated in ras responsiveness [4].

Physical interactions of SEC8

• Sec6 and Sec15 coimmunoprecipitate from lysates with c-myc-tagged Sec8 [3].

Other interactions of SEC8

• Human Sec3 (hSec3) shares 17% sequence identity with yeast Sec3p, interacts in the two-hybrid system with other subunits of the complex (Sec5 and Sec8), and is expressed in almost all tissues tested [8].

Analytical, diagnostic and therapeutic context of SEC8

• Gel filtration studies suggest that a portion of Sec4p is in association with the Sec8p/Sec15p particle [4].
• In this study, oligonucleotide-directed mutagenesis is used to alter the COOH-terminal portion of Sec8 with a 6-histidine tag, a 9E10 c-myc epitope, or both, to allow the isolation of the Sec8/15 complex from yeast lysates either by immobilized metal affinity chromatography or by immunoprecipitation [3].
• The c-myc-Sec8 protein is localized by immunofluorescence to small bud tips indicating that the Sec6/8/15 complex may function at sites of exocytosis [3].

References