In contrast to the current model of MHC class I trafficking, which predicts that once a MHC class I molecule leaves the ER, it moves to the cell surface by bulk flow, we show that HLA-G that is loaded with suboptimal peptides is retrieved from post-ER compartments to the ER. Loading of HLA-G with high-affinity peptides abrogates this retrieval due to the lack of binding affinity to coatomer. Moreover, the loss of the endocytosis motif in the truncated cytoplasmic tail results in the prolonged half-life of HLA-G on the cell surface. Our findings reveal that surface expression of HLA-G can be further regulated in post-ER compartments and that the truncated cytoplasmic tail plays a critical role in such quality-control mechanisms.
Bibliographical noteFunding Information:
We are very grateful to Drs. D. Geraghty, Y. Loke, R. Pettersson, K. Moremen, and Y. Yang for providing various reagents. This work was supported by a grant from the 21C Frontier for Functional Genome Analysis of Human Genome.
All Science Journal Classification (ASJC) codes
- Immunology and Allergy
- Infectious Diseases