Ubiquitin ligase MARCH 8 cooperates with CD83 to control surface MHC II expression in thymic epithelium and CD4 T cell selection

Haiyin Liu, Reema Jain, Jing Guan, Vivian Vuong, Satoshi Ishido, Nicole L. La Gruta, Daniel H. Gray, Jose A. Villadangos, Justine D. Mintern

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Major histocompatibility complex class II (MHC II) expression is tightly regulated, being subjected to cell type-specific mechanisms that closely control its levels at the cell surface. Ubiquitination by the E3 ubiquitin ligase MAR CH 1 regulates MHC II expression in dendritic cells and B cells. In this study, we demonstrate that the related ligase MAR CH 8 is responsible for regulating surface MHC II in thymic epithelial cells (TECs). March8-/- mice have elevated MHC II at the surface of cortical TECs and autoimmune regulator (AIRE)- medullary TECs (mTECs), but not AIRE+ mTECs. Despite this, thymic and splenic CD4+ T cell numbers and repertoires remained unaltered in March8-/- mice. Notably, the ubiquitination of MHC II by MAR CH 8 is controlled by CD83. Mice expressing a mutated form of CD83 (Cd83anu/anu mice) have impaired CD4+ T cell selection, but deleting March8 in Cd83anu/anu mice restored CD4+ T cell selection to normal levels. Therefore, orchestrated regulation of MHC II surface expression in TECs by MAR CH 8 and CD83 plays a major role in CD4+ T cell selection. Our results also highlight the specialized use of ubiquitinating machinery in distinct antigen-presenting cell types, with important functional consequences and implications for therapeutic manipulation.

Original languageEnglish
Pages (from-to)1695-1703
Number of pages9
JournalJournal of Experimental Medicine
Issue number9
Publication statusPublished - 8 Aug 2016

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