LAMP-2C regulation of MHC class II antigen presentation (P5020)

Abstract

Abstract Chaperone-mediated autophagy (CMA) is a selective autophagy pathway, which relies on the lysosome-associated membrane protein (LAMP)-2A to translocate proteins from the cytoplasm into lysosomes. Alternative splicing of the LAMP-2 gene generates 3 highly conserved isoforms LAMP-2A, LAMP-2B and LAMP-2C. LAMP-2A overexpression increases MHC class II (MHCII) presentation of the cytoplasmic autoantigen, GAD, demonstrating a role for CMA in antigen presentation. Overexpression of LAMP-2B did not alter cytoplasmic GAD presentation, however, remarkably ectopic expression of LAMP-2C in B cells inhibited T cell responses to cytoplasmic GAD. Studies were undertaken here to understand the role of LAMP-2C in MHCII antigen presentation. The presentation of several exogenous proteins was not affected by LAMP-2C expression in B cells. Similar results were observed for the presentation of endogenous self and viral membrane proteins. These results suggest that LAMP-2C may be a specific inhibitor of antigen presentation via autophagy. Ectopic expression of LAMP-2C also failed to perturb MHCII presentation of the MP1-LC3 antigen via macroautophagy. Thus LAMP-2C appears to inhibit the presentation of cytoplasmic proteins that are processed through CMA and may not affect other autophagy pathways. Future studies are underway to determine mechanistically how LAMP-2C controls antigen presentation.