Biochemical characterization and biosynthesis of the Ki-1 antigen in Hodgkin-derived and virus-transformed human B and T lymphoid cell lines.
The Hodgkin-associated Ki-1 antigen was analyzed in different cell lines. In Hodgkin analogous L428 cells, biosynthetically labeled with radioactive amino acids, the Ki-1 antibody precipitated three glycoproteins with 90, 105, and 120 kDa, respectively. Surface-labeling revealed that the two larger components were membrane-associated forms of the Ki-1 antigen, although the 90-kDa molecule was shown in pulse-chase experiments to be the precursor of the 105- and 120-kDa forms. All three forms of the Ki-1 antigen possess a tunicamycin-sensitive 6-kDa N-linked carbohydrate moiety. O-Linked oligosaccharides could not be detected. Thus, the differences in m.w. are probably not due to glycosylation. The ionophore monensin prevented the appearance of the membrane-associated molecules, which demonstrated that they are assembled between the transcompartment of the Golgi complex and their insertion into the cell membrane. The 90-kDa precursor molecule cannot be generated by disulfide reduction from the two larger forms. After internal labeling with P-32, only the 105- and 120-kDa bands became visible, indicating that the Ki-1 molecule is phosphorylated after its processing into the two larger membrane-associated forms. Analysis of the Ki-1 antigens from other cell lines demonstrated that after external labeling of two other Hodgkin-derived cell lines, six Epstein-Barr virus lymphoblastoid cell lines and one human T leukemia virus I-positive T cell line, both the 105- and the 120-kDa membrane molecules could be detected, regardless of the presence or type of virus integrated.
D000951:Antigens, Neoplasm / Q000032:analysis* / Q000096:biosynthesis; D000954:Antigens, Surface / Q000032:analysis; D001402:B-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D002472:Cell Transformation, Viral; D017977:Deltaretrovirus; D006023:Glycoproteins / Q000032:analysis / Q000378:metabolism; D004854:Herpesvirus 4, Human; D006689:Hodgkin Disease / Q000276:immunology*; D006801:Humans; D008970:Molecular Weight; D008985:Monensin / Q000494:pharmacology; D010447:Peptide Hydrolases; D010750:Phosphoproteins / Q000032:analysis / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D014415:Tunicamycin / Q000494:pharmacology
D000951:Antigens, Neoplasm; D000954:Antigens, Surface; D006023:Glycoproteins; D010750:Phosphoproteins; D014415:Tunicamycin; D008985:Monensin; D010447:Peptide Hydrolases