LAMP-2C Inhibits MHC Class II Presentation of Cytoplasmic Antigens by Disrupting Chaperone-Mediated Autophagy
LAMP-2C Inhibits MHC Class II Presentation of Cytoplasmic Antigens by Disrupting Chaperone-Mediated Autophagy
Abstract Cells use multiple autophagy pathways to sequester macromolecules, senescent organelles, and pathogens. Several conserved isoforms of the lysosome-associated membrane protein-2 (LAMP-2) regulate these pathways influencing immune recognition and responses. LAMP-2A is required for chaperone-mediated autophagy (CMA), which promotes Ag capture and MHC class II (MHCII) presentation in B cells and signaling in T cells. LAMP-2B regulates lysosome maturation to impact macroautophagy and phagocytosis. Yet, far less is known about LAMP-2C function. Whereas LAMP2A and LAMP2B mRNA were broadly detected in human tissues, LAMP2C expression was more limited. Transcripts for the three LAMP2 isoforms increased with B cell activation, although specific gene induction varied depending on TLR versus BCR engagement. To examine LAMP-2C function in human B cells and specifically its role in Ag presentation, we used ectopic gene expression. Increased LAMP-2C expression in B cells did not alter MHCII expression or invariant chain processing, but did perturb cytoplasmic Ag presentation via CMA. MHCII presentation of epitopes from exogenous and membrane Ags was not affected by LAMP-2C expression in B cells. Similarly, changes in B cell LAMP-2C expression did not impact macroautophagy. The gene expression of other LAMP2 isoforms and proteasome and lysosomal proteases activities were unperturbed by LAMP-2C ectopic expression. LAMP-2C levels modulated the steady-state expression of several cytoplasmic proteins that are targeted for degradation by CMA and diminished peptide translocation via this pathway. Thus, LAMP-2C serves as a natural inhibitor of CMA that can selectively skew MHCII presentation of cytoplasmic Ags.
- Indiana University United States
- Purdue University System United States
- Indiana University – Purdue University Indianapolis United States
- University of Utah United States
- Indiana University School of Medicine United States
Cytoplasm, Cell separation, Histocompatibility antigens class II, Immunoblotting, Enzyme-Linked Immunosorbent Assay, Cell Separation, Real-Time Polymerase Chain Reaction, Transfection, Real-time polymerase chain reaction, Enzyme-linked immunosorbent assay, Lysosomal-Associated Membrane Protein 2, Autophagy, Humans, Immunoprecipitation, Protein Isoforms, Flow cytometry, Antigen presentation, Protein isoforms, Reverse transcriptase polymerase chain reaction, Antigen Presentation, B-Lymphocytes, Reverse Transcriptase Polymerase Chain Reaction, Histocompatibility Antigens Class II, Flow Cytometry, Lysosomal-associated membrane protein 2, Electroporation
Cytoplasm, Cell separation, Histocompatibility antigens class II, Immunoblotting, Enzyme-Linked Immunosorbent Assay, Cell Separation, Real-Time Polymerase Chain Reaction, Transfection, Real-time polymerase chain reaction, Enzyme-linked immunosorbent assay, Lysosomal-Associated Membrane Protein 2, Autophagy, Humans, Immunoprecipitation, Protein Isoforms, Flow cytometry, Antigen presentation, Protein isoforms, Reverse transcriptase polymerase chain reaction, Antigen Presentation, B-Lymphocytes, Reverse Transcriptase Polymerase Chain Reaction, Histocompatibility Antigens Class II, Flow Cytometry, Lysosomal-associated membrane protein 2, Electroporation
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