Concentration of GPI-Anchored Proteins upon ER Exit in Yeast

• Published in: Traffic (Copenhagen, Denmark) Vol. 10; no. 2; pp. 186 - 200
• Main Authors: Castillon, Guillaume A, Watanabe, Reika, Taylor, Marcia, Schwabe, Tatjana M.E, Riezman, Howard
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.02.2009; Blackwell Publishing Ltd
• Subjects: Amino Acid Transport Systems - genetics; Amino Acid Transport Systems - metabolism; Bst1p; Cell Wall - genetics; Cell Wall - metabolism; COPII; Cwp2p; Cytoplasmic Vesicles - metabolism; Emp24p; Endoplasmic Reticulum - metabolism; ER exit site; Erv14p; Glucose Transport Proteins, Facilitative; Glycosylphosphatidylinositols - metabolism; GPI-anchored proteins; Hxt1p; Membrane Glycoproteins - genetics; Membrane Glycoproteins - metabolism; Membrane Proteins - genetics; Membrane Proteins - metabolism; Monosaccharide Transport Proteins - genetics; Monosaccharide Transport Proteins - metabolism; Per1p; Saccharomyces cerevisiae; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Temperature; Vesicular Transport Proteins - genetics; Vesicular Transport Proteins - metabolism
• ISSN: 1398-9219; 1600-0854; 1600-0854
• DOI: 10.1111/j.1600-0854.2008.00857.x

Previous biochemical work has revealed two parallel routes of exit from the endoplasmic reticulum (ER) in the yeast Saccharomyces cerevisiae, one seemingly specific for glycosyl-phosphatidylinositol (GPI)-anchored proteins. Using the coat protein II (COPII) mutant sec31-1, we visualized ER exit sites (ERES) and identified three distinct ERES populations in vivo. One contains glycosylated pro-α-factor, the second contains the GPI-anchored proteins Cwp2p, Ccw14p and Tos6p and the third is enriched with the hexose transporter, Hxt1p. Concentration of GPI-anchored proteins prior to budding requires anchor remodeling, and Hxt1p incorporation into ERES requires the COPII components Sec12p and Sec16p. Additionally, we have found that GPI-anchored protein ER exit is controlled by the p24 family member Emp24p, whereas ER export of most transmembrane proteins requires the Cornichon homologue Erv14p.