title: A mutant cell with a novel defect in MHC class I quality control.
abstract: COS7 (African Green Monkey kidney) cells stably transfected with the mouse MHC class I allele H-2K(b) were mutagenized, selected for low surface expression of endogenous MHC class I products, and subcloned. A mutant cell line, 4S8.12, expressing very low surface MHC class I (approximately 5% of parental levels) was identified. This cell line synthesized normal levels of the MHC class I H chain and beta(2)-microglobulin, as well as normal levels of TAP, tapasin, GRP78, calnexin, calreticulin, ERp57, and protein disulfide isomerase. Full-length OVA was processed to generate presented H-2K(b)-SIINFEKL complexes with equal efficiency in wild-type and mutant cells, demonstrating that proteasomes, as well as TAP and tapasin, functioned normally. Therefore, all the known components of the MHC class I Ag presentation pathway were intact. Nevertheless, primate (human and monkey) MHC class I H chain and beta(2)-microglobulin failed to associate to form the normal peptide-receptive complex. In contrast, mouse H chains associated with beta(2)-microglobulin normally and bound peptide at least as well as in wild-type cells. The 4S8.12 cells provide strong genetic evidence for a novel component in the MHC class I pathway. This as-yet unidentified gene is important in early assembly of primate, but not mouse, MHC class I complexes.
authors.affiliation: Department of Pathology, University of Massachusetts Medical Center, Worcester, 01655, USA. Ian.York@umassmed.edu
authors.forename: Ian A
authors.initials: IA
authors.lastname: York
authors.forename: Ethan P
authors.initials: EP
authors.lastname: Grant
authors.forename: A Maria
authors.initials: AM
authors.lastname: Dahl
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Rock
mesh_terms: D000818:Animals; D019556:COS Cells; D002462:Cell Membrane / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D002522:Chlorocebus aethiops; D015536:Down-Regulation / Q000235:genetics* / Q000276:immunology*; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D006183:H-2 Antigens / Q000096:biosynthesis* / Q000235:genetics*; D006801:Humans; D051379:Mice; D018832:Molecular Chaperones / Q000096:biosynthesis / Q000378:metabolism; D016296:Mutagenesis; D011499:Protein Processing, Post-Translational / Q000235:genetics*; D011786:Quality Control; D001613:beta 2-Microglobulin / Q000235:genetics / Q000378:metabolism
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; D006183:H-2 Antigens; C032876:H-2Kb protein, mouse; C000717247:HSPA5 protein, human; C000717248:Hspa5 protein, mouse; D018832:Molecular Chaperones; D001613:beta 2-Microglobulin