title: The Hodgkin-associated Ki-1 antigen exists in an intracellular and a membrane-bound form.
abstract: The Hodgkin-associated Ki-1 antigen occurs in two different molecular forms. The 120-kDa membrane-associated form is a phosphorylated glycoprotein, which is derived from a non-phosphorylated intracellular 84-kDa apoprotein that is co-translationally N-glycosylated with a carbohydrate portion of 6 kDa. The other form of the Ki-1 antigen is a non-glycosylated phosphoprotein of 57 kDa which only occurs intracellularly. Both forms of the antigen are phosphorylated at serine residues. Enzymatic cleavage with sialidase reduced the 120-kDa membrane antigen by about 15 kDa, while its 90-kDa precursor and the 57-kDa intracellular form of the Ki-1 antigen remained unaltered. Pulse-chase experiments revealed that the 57-kDa and 90/120-kDa molecules are synthesized independently of each other. Four to eight hours after synthesis, the degradation of the 120-kDa molecule to a 105-kDa membrane-associated intermediate begins. This is further processed and appears in the cell supernate as a 90-kDa molecule. Hodgkin's disease-derived, Epstein-Barr virus-transformed cell lines and the acute T cell leukemia line MOLT-4 contain both forms of the Ki-1 antigen, whereas only the 57-kDa intracellular antigen is expressed in U266/B1 myeloma cells, in the Burkitt lymphoma cell lines Raji and Daudi and in acute promyelocytic HL-60 leukemia cells.
authors.affiliation: Biochemisches Institut der Medizinischen Fakultät der Universität Kiel.
authors.forename: H
authors.initials: H
authors.lastname: Hansen
authors.forename: H
authors.initials: H
authors.lastname: Lemke
authors.forename: G
authors.initials: G
authors.lastname: Bredfeldt
authors.forename: I
authors.initials: I
authors.lastname: Könnecke
authors.forename: B
authors.initials: B
authors.lastname: Havsteen
mesh_terms: D000596:Amino Acids / Q000032:analysis; D000943:Antigens, Differentiation / Q000032:analysis*; D000951:Antigens, Neoplasm / Q000032:analysis*; D002462:Cell Membrane / Q000276:immunology; D006031:Glycosylation; D006689:Hodgkin Disease / Q000276:immunology*; D006801:Humans; D017730:Ki-1 Antigen; D009439:Neuraminidase / Q000378:metabolism; D010766:Phosphorylation; D011233:Precipitin Tests; D014407:Tumor Cells, Cultured / Q000276:immunology
chemical_list: D000596:Amino Acids; D000943:Antigens, Differentiation; D000951:Antigens, Neoplasm; D017730:Ki-1 Antigen; D009439:Neuraminidase