Biochemical characterization of CD1d expression in the absence of beta2-microglobulin.
CD1d is a major histocompatibility complex class I-like molecule that exhibits a distinct antigen processing pathway that functions in the presentation of hydrophobic antigens to T cells. CD1d has been previously shown to be expressed on the cell surface of human intestinal epithelial cell lines in vivo and a transfected cell line in vitro independently of beta2-microglobulin (beta2m). To define the relationship between CD1d and beta2m and characterize the biochemical structure of CD1d in the absence of beta2m, we have used a newly generated series of CD1d transfectants and CD1d-specific antibodies. These studies show that in the absence of beta2m, CD1d is expressed on the cell surface as a 45-kDa glycoprotein that is sensitive to endoglycosidase-H and is reduced to 37-kDa after N-glycanase digestion. In contrast, in the presence of beta2m, CD1d is expressed on the cell surface as a 48-kDa endoglycosidase-H-resistant glycoprotein. Pulse-chase metabolic labeling studies demonstrate that acquisition of endoglycosidase-H resistance of CD1d is observed in the presence of beta2m but not in the absence of beta2m even after a 24-h chase period. Thus, CD1d is able to be transported to the cell surface independently of beta2m; however, in the absence of beta2m, the glycosylation pattern of CD1d is altered and consistent with an immature glycoprotein.
Kim
H S
HS
Division of Gastroenterology, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
Garcia
J
J
Exley
M
M
Johnson
K W
KW
Balk
S P
SP
Blumberg
R S
RS
D000818:Animals; D018949:Antigens, CD1 / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics; D055610:Antigens, CD1d; D000954:Antigens, Surface / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D015153:Blotting, Western; D016466:CHO Cells; D002469:Cell Separation; D006224:Cricetinae; D004591:Electrophoresis, Polyacrylamide Gel; D005434:Flow Cytometry; D006031:Glycosylation; D006596:Hexosaminidases / Q000378:metabolism; D006801:Humans; D014162:Transfection; D014407:Tumor Cells, Cultured; D001613:beta 2-Microglobulin / Q000096:biosynthesis / Q000737:chemistry / Q000172:deficiency*
D018949:Antigens, CD1; D055610:Antigens, CD1d; D000954:Antigens, Surface; C526877:CD1D protein, human; D001613:beta 2-Microglobulin; D006596:Hexosaminidases