Allele-Independent Turnover of Human Leukocyte Antigen (HLA) Class Ia Molecules

• Published in: PloS one Vol. 11; no. 8; p. e0161011
• Main Authors: Prevosto, Claudia, Usmani, M Farooq, McDonald, Sarah, Gumienny, Aleksandra M, Key, Tim, Goodman, Reyna S, Gaston, J S Hill, Deery, Michael J, Busch, Robert
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 16-08-2016; Public Library of Science (PLoS)
• Subjects: Alleles; Antigen presentation; Arthritis; Biology and Life Sciences; Blood & organ donations; CD8 antigen; Cell activation; Cell Line, Tumor; Cell lines; Dendritic cells; Deuterium Oxide - chemistry; Gene expression; Gene mapping; Genetic polymorphisms; Glycoproteins; Half-life; Heavy water; Histocompatibility antigen HLA; HLA antigens; HLA Antigens - chemistry; HLA Antigens - genetics; HLA Antigens - metabolism; Human subjects; Humans; Isotope Labeling; Isotypes; Leukocytes; Lymphocytes; Lymphocytes T; Major histocompatibility complex; Mass spectrometry; Mass spectroscopy; Medicine and Health Sciences; Monocytes; Natural killer cells; Peptides; Polymorphism; Protein turnover; Proteins; Research and Analysis Methods; Viral infections; Viruses
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0161011

Major histocompatibility complex class I (MHCI) glycoproteins present cytosolic peptides to CD8+ T cells and regulate NK cell activity. Their heavy chains (HC) are expressed from up to three MHC gene loci (human leukocyte antigen [HLA]-A, -B, and -C in humans), whose extensive polymorphism maps predominantly to the antigen-binding groove, diversifying the bound peptide repertoire. Codominant expression of MHCI alleles is thus functionally critical, but how it is regulated is not fully understood. Here, we have examined the effect of polymorphism on the turnover rates of MHCI molecules in cell lines with functional MHCI peptide loading pathways and in monocyte-derived dendritic cells (MoDCs). Proteins were labeled biosynthetically with heavy water (2H2O), folded MHCI molecules immunoprecipitated, and tryptic digests analysed by mass spectrometry. MHCI-derived peptides were assigned to specific alleles and isotypes, and turnover rates quantified by 2H incorporation, after correcting for cell growth. MHCI turnover half-lives ranged from undetectable to a few hours, depending on cell type, activation state, donor, and MHCI isotype. However, in all settings, the turnover half-lives of alleles of the same isotype were similar. Thus, MHCI protein turnover rates appear to be allele-independent in normal human cells. We propose that this is an important feature enabling the normal function and codominant expression of MHCI alleles.