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Roles for the Drs2p–Cdc50p Complex in Protein Transport and Phosphatidylserine Asymmetry of the Yeast Plasma Membrane
Author(s) -
Chen Sophie,
Wang Jiyi,
Muthusamy BabyPeriyanayaki,
Liu Ke,
Zare Sara,
Andersen Raymond J,
Graham Todd R
Publication year - 2006
Publication title -
traffic
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.677
H-Index - 130
eISSN - 1600-0854
pISSN - 1398-9219
DOI - 10.1111/j.1600-0854.2006.00485.x
Subject(s) - biology , endoplasmic reticulum , golgi apparatus , microbiology and biotechnology , flippase , phosphatidylserine , clathrin , transport protein , endocytosis , membrane protein , copi , secretory pathway , biochemistry , membrane , cell , phospholipid
Drs2p, a P‐type adenosine triphosphatase required for a phosphatidylserine (PS) flippase activity in the yeast trans Golgi network (TGN), was first implicated in protein trafficking by a screen for mutations synthetically lethal with arf1 ( swa ). Here, we show that SWA4 is allelic to CDC50 , encoding a membrane protein previously shown to chaperone Drs2p from the endoplasmic reticulum to the Golgi complex. We find that cdc50 Δ exhibits the same clathrin‐deficient phenotypes as drs2Δ, including delayed transport of carboxypeptidase Y to the vacuole, mislocalization of resident TGN enzymes and the accumulation of aberrant membrane structures. These trafficking defects precede appearance of cell polarity defects in cdc50 Δ, suggesting that the latter are a secondary consequence of disrupting Golgi function. Involvement of Drs2p–Cdc50p in PS translocation suggests a role in restricting PS to the cytosolic leaflet of the Golgi and plasma membrane. Annexin V binding and papuamide B hypersensitivity indicate that drs2 Δ or cdc50 Δ causes a loss of plasma membrane PS asymmetry. However, clathrin and other endocytosis null mutants also exhibit a comparable loss of PS asymmetry, and studies with drs2‐ts and clathrin ( chc1‐ts ) conditional mutants suggest that loss of plasma membrane asymmetry is a secondary consequence of disrupting protein trafficking.