| First Author | Cho KJ | Year | 2015 |
| Journal | Proc Natl Acad Sci U S A | Volume | 112 |
| Issue | 33 | Pages | 10449-54 |
| PubMed ID | 26240324 | Mgi Jnum | J:226568 |
| Mgi Id | MGI:5697768 | Doi | 10.1073/pnas.1507981112 |
| Citation | Cho KJ, et al. (2015) Ubiquitination by March-I prevents MHC class II recycling and promotes MHC class II turnover in antigen-presenting cells. Proc Natl Acad Sci U S A 112(33):10449-54 |
| abstractText | MHC class II (MHC-II)-dependent antigen presentation by antigen-presenting cells (APCs) is carefully controlled to achieve specificity of immune responses; the regulated assembly and degradation of antigenic peptide-MHC-II complexes (pMHC-II) is one aspect of such control. In this study, we have examined the role of ubiquitination in regulating pMHC-II biosynthesis, endocytosis, recycling, and turnover in APCs. By using APCs obtained from MHC-II ubiquitination mutant mice, we find that whereas ubiquitination does not affect pMHC-II formation in dendritic cells (DCs), it does promote the subsequent degradation of newly synthesized pMHC-II. Acute activation of DCs or B cells terminates expression of the MHC-II E3 ubiquitin ligase March-I and prevents pMHC-II ubiquitination. Most importantly, this change results in very efficient pMHC-II recycling from the surface of DCs and B cells, thereby preventing targeting of internalized pMHC-II to lysosomes for degradation. Biochemical and functional assays confirmed that pMHC-II turnover is suppressed in MHC-II ubiquitin mutant DCs or by acute activation of wild-type DCs. These studies demonstrate that acute APC activation blocks the ubiquitin-dependent turnover of pMHC-II by promoting efficient pMHC-II recycling and preventing lysosomal targeting of internalized pMHC-II, thereby enhancing pMHC-II stability for efficient antigen presentation to CD4 T cells. |
