Viral immune evasions differentially impact cell surface presentation of MHC I allomorphs already at the peptide-loading complex

ABSTRACT: The transporter associated with antigen processing (TAP) translocates peptides from the cytosol into the endoplasmic reticulum (ER) where they are loaded onto major histocompatibility class I (MHC I) molecules. Stable peptide-MHC I complexes travel to the cell surface and present their antigenic cargo to cytotoxic T lymphocytes. As central part of the peptide-loading complex (PLC), TAP is targeted by several viral proteins, which inhibit peptide translocation and thereby impact MHC I-mediated immune responses. However, it is still poorly understood whether the MHC I allotypes are differently affected by TAP inhibition. Here, we show that conditional expression of herpes simplex virus (HSV) ICP47 suppresses surface presentation of the MHC I allotypes HLA-A and HLA-C, but not of HLA-B, while expression of cytomegalovirus (CMV) US6 reduces surface levels of all allotypes. This difference is directly reflected in a specific enrichment of HLA-B molecules at US6 arrested PLC. Since ICP47 and US6 inhibit TAP in different transport-incompetent conformations, our data imply that MHC I allomorphs are preferentially recruited or trapped at the PLC leading to selective downregulation of MHC I surface presentation. Our findings suggest that viral immune evasions not only inhibit peptide supply to the ER by TAP, but also modulate the assembly and chaperone activity of the PLC.

INSTRUMENT(S):

ORGANISM(S): Homo Sapiens (human)

TISSUE(S): Cell Culture

SUBMITTER: Marie Alfes  

LAB HEAD: Carla Schmidt

PROVIDER: PXD027408 | Pride | 2022-02-17

REPOSITORIES: Pride