{-}{-}{-}{-}{-}Polyglutamine-related aggregates serve as a potent antigen source for cross presentation by dendritic cells

Protective MHC-I dependent immune responses require an overlap between repertoires of proteins directly presented on target cells and cross-presented by professional antigen presenting cells (APC), specifically dendritic cells (DCs). How stable proteins that rely on DRiPs for direct presentation are captured for cell-to-cell transfer remains enigmatic. Here we address this issue using a combination of in vitro and in vivo approaches involving stable and unstable versions of ovalbumin model antigens displaying DRiP-dependent and -independent antigen presentation, respectively. Apoptosis, but not necrosis of donor cells was found associated with robust p62-dependent global protein aggregate formation and captured stable proteins permissive for DC cross-presentation. Potency of aggregates to serve as antigen source was directly demonstrated using polyglutamine-equipped model substrates. Collectively, our data implicate global protein aggregation in apoptotic cells as a mechanism that ensures the overlap between MHC-I epitopes presented directly or cross-presented by APC and demonstrate the unusual ability of DC to process stable protein aggregates.\n\nSummaryProtective T cell immunity relies on the overlap of the antigen repertoire expressed by cells and the repertoire presented by dendritic cells that are required to trigger naive T cells. We suggest a mechanism that contributes to ensure this antigenic overlap. Our findings demonstrate that upon apoptosis stable proteins are aggregated in p62-dependent pathway and that dendritic cells are capable to efficiently process these aggregates to retrieve antigens for T cell stimulation.