title: 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.
authors: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202;
authors: Liliana
authors: L
authors: Pérez
authors: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202;
authors: Shawna
authors: http://orcid.org/0000-0002-9853-0688
authors: S
authors: McLetchie
authors: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202;
authors: Gail J
authors: http://orcid.org/0000-0001-5306-572X
authors: GJ
authors: Gardiner
authors: Medical Sciences Program, Indiana University, Bloomington, IN 47405; and.
authors: Sarah N
authors: SN
authors: Deffit
authors: Department of Pathology, University of Utah, Salt Lake City, UT 84112.
authors: Delu
authors: D
authors: Zhou
authors: Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202; jblum@iupui.edu.
authors: Janice S
authors: JS
authors: Blum
mesh_terms: D017951:Antigen Presentation / Q000276:immunology*; D001343:Autophagy / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology; D002469:Cell Separation; D003593:Cytoplasm / Q000276:immunology; D018274:Electroporation; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D052119:Lysosomal-Associated Membrane Protein 2 / Q000276:immunology*; D020033:Protein Isoforms / Q000276:immunology; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: D000949:Histocompatibility Antigens Class II; C497811:LAMP2 protein, human; D052119:Lysosomal-Associated Membrane Protein 2; D020033:Protein Isoforms