Posttranslational Neoantigens in Autoimmunity and Metabolism in T1D

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Ongoing analyses from our laboratory and others have identified novel properties of self proteins, namely posttranslational protein modifications (PTMs) that may be identified as early proteomic and immunologic biomarkers of Type 1 diabetes as well as alter metabolic pathways. An emerging number of self proteins acquire PTMs and become targets of B and T cell autoimmune responses leading to inflammation and pathology in the pancreas. Some examples of critical modifications to self proteins include citrullination, oxidation, deamidation reactions, and isoaspartyl modification, all responses of self proteins within cells that undergo inflammatory stress. Key PTM candidates have already been identified from human beta cells and other key candidates will be identified from beta cell derived exosomes, recently identified as a peripheral marker of beta cell health. As importantly, these PTMs within cells may alter the biological properties of proteins within beta cells. In the present proposal, we will define how modified self-proteins may alter enzymatic pathways of glucose sensing and insulin secretion in the pancreatic beta cell. The proposal will utilize MultiOrdinate Spectral Analysis (MIMOSA), a technology pioneered at Yale University. MIMOSA is a major innovation that provides an internally cross-validated as well as NMR-validated, direct, rigorous, comprehensive integrated analysis of metabolic fluxes. The “multi-ordinate” aspect of MIMOSA incorporates the flow of stable isotope from metabolite to metabolite along intersecting metabolic pathways. The “mass isotopomer” aspect uses MS/MS-based ion fragmentation analysis of stable-isotope-labeled metabolites to identify the carbon-specific position of label. The significance and innovation of the present studies is in identifying pathways that may restore beta cell functions, via pharmaceutical correction of the aberrant modification, as well as link autoimmune biomarkers with pathways of beta cell dysfunction.