MHC class II stabilization at the surface of human dendritic cells is the result of maturation-dependent MARCH I down-regulation.

De Gassart A, Camosseto V, Thibodeau J, Ceppi M, Catalan N, Pierre P, Gatti E.
Proc Natl Acad Sci U S A. 2008 Mar 4;105(9):3491-6. Epub 2008 Feb 27.

In response to Toll-like receptor ligands, dendritic cells (DCs) dramatically enhance their antigen presentation capacity by stabilizing at the cell-surface MHC II molecules. We demonstrate here that, in human monocyte-derived DCs, the RING-CH ubiquitin E3 ligase, membrane-associated RING-CH I (MARCH I), promotes the ubiquitination of the HLA-DR beta-chain. Thus, in nonactivated DCs, MARCH I induces the surface internalization of mature HLA-DR complexes, therefore reducing their stability and levels. We further demonstrate that the maturation-dependent down-regulation of MARCH I is a key event in MHC class II up-regulation at the surface of LPS-activated DCs. MARCH I is, therefore, a major regulator of HLA-DR traffic, and its loss contributes to the acquisition of the potent immunostimulatory properties of mature human DCs.

URL: http://www.pnas.org/content/105/9/3491

Pub Med: http://www.ncbi.nlm.nih.gov/pubmed/18305173

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