Project description:Tapasin acts as the principal MHC-I-specific chaperone for facilitating folding and antigenic peptide loading of nascent MHC class I substrates in the cell. In cells where tapasin has been knocked out, the processing and surface trafficking of the human MHC-I allele HLA-A2 is substantially reduced. Over-expression of tapasin rescues HLA-A2 surface expression. Using this assay as the basis for a fluorescence-based selection, tapasin was deep mutationally scanned at 108 positions in the core, at the interface with MHC-I, and on the ‘backside’ distal from where MHC-I binds. Critical residues of tapasin for rescue of HLA-A2 processing map to sites that contact the underside of the MHC-I alpha-2 domain, to the surface contacting the MHC-1 beta2m and alpha-3 domains, and to the base of a protruding loop that rests above the peptide-binding groove (but not to the tip of the loop itself).
Project description:Oligodendrocytes and their progenitors upregulate MHC pathways in response to inflammation, but the frequency of this phenotypic change is unknown and the features of these immune oligodendroglia are poorly defined. We generated MHC class I and II transgenic reporter mice to define their dynamics in response to inflammatory demyelination, providing a means to monitor MHC activation in diverse cell types in living mice and define their roles in aging, injury and disease.
Project description:Impaired expression of MHC class I constitutes a major mechanism of immune evasion of cancers, leading to poor prognosis and resistance to checkpoint blockade therapies. Existing drugs for MHC class I have limited applicability due to severe side effects. Here we show a novel approach of robust and specific induction of MHC class I by targeting an MHC class I transactivator (CITA), NLRC5, using a CRISPR/Cas9 based gene-specific targeted demethylaion (TDM) system and targeted demethylation and activation (TDMa) system. The TDMa system specifically recruits a demethylating enzyme and transcriptional activators, providing efficient demethylation and transactivation of the NLRC5 promoter. TDMa in mouse and human cancer cells induced MHC class I antigen presentation and accelerated CD8+ T cell activation with tumor suppression effects both in vitro and in vivo. Moreover, enhanced immunogenicity by NLRC5 TDMa boosted efficacy of anti-PD1 therapy. Therefore, NLRC5 targeting by the TDMa system confers an attractive therapeutic approach against cancer.