Degradation Mechanism of MHC class II Clarified
February 20, 2014
Dendritic cells are antigen-presenting cells in the mammalian immune system. They ingest foreign pathogens such as bacteria or viruses and generate peptide fragments of these pathogens in endosomes and lysosomes. MHC (major histocompatibility complex) class II is the protein that is expressed in dendritic cells to present antigens. Peptide-MHC class II(pMHC-II) complexes are assembled in the endoplasmic reticulum and transported to cell surface for presentation. After presentation, the pMHC-II complexes are degraded. The mechanisms leading to MHC class II degradation are poorly understood. While MHC-II that has not yet loaded antigenic peptides is not degraded at all, it is certain that pMHC-II complexes are ubiquitinated by the enzyme March-I and then degraded. It is not clear how MHC-II without antigenic peptides is distinguished from pMHC-II complexes.
The research group in Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences has shown that Invariant chain bound to MHC-II without antigenic peptides controls the transportation of the MHC-II, the MHC-II is not transported to localized March-I and not ubiquitinated. Therefore MHC-II without peptides is not degraded.
The findings were published on December 10, 2013 in the journal of Proceedings of the National Academy of Sciences.
Mototaka Senda, Ph.D.
Intellectual Property Office, Organization for Research Promotion and Collaboration, Okayama University
Fremont, California USA
Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, Okayama, Japan