Journal
JOURNAL OF CELL BIOLOGY
Volume 217, Issue 2, Pages 585-599Publisher
ROCKEFELLER UNIV PRESS
DOI: 10.1083/jcb.201706135
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Funding
- National Natural Science Foundation of China [31400693, 31770853]
- Natural Science Foundation of Jiangsu Province [BK20140141]
- Young Thousand program
- Program of Introducing Talents of Discipline to Universities [111-2-06]
- Japan Society for the Promotion of Science KAKENHI [JP16H04756]
- Grants-in-Aid for Scientific Research [17H06422] Funding Source: KAKEN
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Glycosylphosphatidylinositol (GPI) anchoring of proteins is a conserved posttranslational modification in the endoplasmic reticulum (ER). Soon after GPI is attached, an acyl chain on the GPI inositol is removed by post-GPI attachment to proteins 1 (PGAP1), a GPI-inositol deacylase. This is crucial for switching GPI-anchored proteins (GPI-APs) from protein folding to transport states. We performed haploid genetic screens to identify factors regulating GPI-inositol deacylation, identifying seven genes. In particular, calnexin cycle impairment caused inefficient GPI-inositol deacylation. Calnexin was specifically associated with GPI-APs, dependent on N-glycan and GPI moieties, and assisted efficient GPI-inositol deacylation by PGAP1. Under chronic ER stress caused by misfolded GPI-APs, inositol-acylated GPI-APs were exposed on the cell surface. These results indicated that N-glycans participate in quality control and temporal ER retention of GPI-APs, ensuring their correct folding and GPI processing before exiting from the ER. Once the system is disrupted by ER stress, unprocessed GPI-APs become exposed on the cell surface.
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