Exit of GPI-anchored proteins from the ER differs in yeast and mammalian cells.
Previous studies have shown that yeast glycosylphosphatidylinositol-anchored proteins (GPI-APs) and other secretory proteins are preferentially incorporated into distinct coat protein II (COPII) vesicle populations for their transport from the endoplasmic reticulum (ER) to the Golgi apparatus, and that incorporation of yeast GPI-APs into COPII vesicles requires specific lipid interactions. We compared the ER exit mechanism and segregation of GPI-APs from other secretory proteins in mammalian and yeast cells. We find that, unlike yeast, ER-to-Golgi transport of GPI-APs in mammalian cells does not depend on sphingolipid synthesis. Whereas ER exit of GPI-APs is tightly dependent on Sar1 in mammalian cells, it is much less so in yeast. Furthermore, in mammalian cells, GPI-APs and other secretory proteins are not segregated upon COPII vesicle formation, in contrast to the remarkable segregation seen in yeast. These findings suggest that GPI-APs use different mechanisms to concentrate in COPII vesicles in the two organisms, and the difference might explain their propensity to segregate from other secretory proteins upon ER exit.
Rivier
Anne-Sophie
AS
Department of Biochemistry, University of Geneva, Sciences II, 30 quai Ernest-Ansermet, CH-1211 Geneva, Switzerland.
Castillon
Guillaume A
GA
Michon
Laetitia
L
Fukasawa
Masayoshi
M
Romanova-Michaelides
Maria
M
Jaensch
Nina
N
Hanada
Kentaro
K
Watanabe
Reika
R
D000818:Animals; D016466:CHO Cells; D022181:COP-Coated Vesicles / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D004721:Endoplasmic Reticulum / Q000378:metabolism* / Q000648:ultrastructure; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000737:chemistry / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism; D010743:Phospholipids / Q000737:chemistry / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D013107:Sphingolipids / Q000737:chemistry / Q000378:metabolism; D015003:Yeasts / Q000166:cytology / Q000378:metabolism*
D005656:Fungal Proteins; D017261:Glycosylphosphatidylinositols; D008565:Membrane Proteins; D010743:Phospholipids; D013107:Sphingolipids; C493083:SAR1A protein, human; D020559:Monomeric GTP-Binding Proteins