Functional analysis of a novel E3 ubiquitin ligase family.

在生理条件下，MHC II类（MHC II）的翻译后调控最近在树突状细胞（dc）中得到证实，树突状细胞具有抗原呈递细胞（apc）的潜在功能。在这里，我们报道了E3泛素连接酶march - 1在B细胞MHC H的翻译后调控中起关键作用。在B细胞中，MARCH-I的表达特别高，强制表达MARCH-I诱导MHC II泛素化。在MARCH-I缺陷小鼠（MARCH-I KO）的B细胞中，表面MHC II的半衰期延长，泛素化形式的MHC II完全消失。此外，march - i缺陷B细胞在其表面高度表达外源抗原装载MHC II，并表现出高的外源抗原呈递能力。这些结果表明，MHC II在B细胞中的功能是通过MARCH-I的泛素化调节的

The presence of post-translational regulation of MHC class II (MHC II) under physiological conditions has been demonstrated recently in dendritic cells (DCs) that potently function as antigen-presenting cells (APCs). Here, we report that MARCH-I, an E3 ubiquitin ligase, plays a pivotal role in the post-translational regulation of MHC H in B cells. MARCH-I expression was particularly high in B cells, and the forced expression of MARCH-I induced the ubiquitination of MHC II. In B cells from MARCH-I-deficient mice (MARCH-I KO), the half-life of surface MHC II was prolonged and the ubiquitinated form of MHC II completely disappeared. In addition, MARCH-I-deficient B cells highly expressed exogenous-antigen-loaded MHC II on their surface and showed high ability to present exogenous antigens. These results suggest that the function of MHC II in B cells is regulated through ubiquitination by MARCH-I