title: CD28 T cell costimulatory receptor function is negatively regulated by N-linked carbohydrates.
abstract: CD28 is a cell surface glycoprotein expressed on T cells that modulates immune responses through its ability to transduce costimulatory signals. Even though nearly 50% of the molecular mass of CD28 is N-glycan, the physiological significance of CD28 glycosylation is at present unknown. In this report, we have investigated the function of hypoglycosylated wildtype CD28 and its splice variant, CD28i. When N-glycosylation was prevented through point mutations in N-glycosylation sites in CD28, or reduced by glycosidase inhibitors, the binding of CD28 to CD80 significantly increased. Stimulation of hypoglycosylated CD28 induced IL-2 promoter activity greater than that induced through the stimulation of wildtype CD28. Unlike hypoglycosylated wildtype CD28, hypoglycosylation of CD28i did not alter CD28i functions. Our data indicate that N-glycans of CD28 negatively regulate CD28/CD80 interactions, resulting in diminished CD28 signaling. It is also suggested that N-glycans regulate the density of CD28 clustering upon ligation with CD80/CD86. The results support the hypothesis that the N-glycosylation negatively regulates CD28-mediated T cell adhesion and costimulation.
authors.affiliation: Department of Biological Chemistry, Faculty of Pharmaceutical Sciences, Kyoto University, Sakyo-ku, Kyoto, Japan.
authors.forename: Bruce Y
authors.initials: BY
authors.lastname: Ma
authors.forename: Sebastian A
authors.initials: SA
authors.lastname: Mikolajczak
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yoshida
authors.forename: Ryoko
authors.initials: R
authors.lastname: Yoshida
authors.forename: David J
authors.initials: DJ
authors.lastname: Kelvin
authors.forename: Atsuo
authors.initials: A
authors.lastname: Ochi
mesh_terms: D017485:1-Deoxynojirimycin / Q000494:pharmacology; D017398:Alternative Splicing; D000818:Animals; D018122:B7-1 Antigen / Q000378:metabolism; D001665:Binding Sites; D018106:CD28 Antigens / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D016466:CHO Cells; D002240:Carbohydrate Sequence; D002448:Cell Adhesion / Q000276:immunology; D006224:Cricetinae; D006026:Glycoside Hydrolases / Q000037:antagonists & inhibitors; D006031:Glycosylation / Q000187:drug effects; D006801:Humans; D007376:Interleukin-2 / Q000235:genetics / Q000378:metabolism; D019169:Jurkat Cells; D008213:Lymphocyte Activation / Q000276:immunology; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D017026:Swainsonine / Q000494:pharmacology; D013601:T-Lymphocytes / Q000276:immunology*; D014162:Transfection
chemical_list: D018122:B7-1 Antigen; D018106:CD28 Antigens; D007376:Interleukin-2; D017485:1-Deoxynojirimycin; D006026:Glycoside Hydrolases; D017026:Swainsonine