title: A 45-kDa human T-cell membrane glycoprotein functions in the regulation of cell proliferative responses.
abstract: A 45-kDa human T cell surface glycoprotein which is tightly bound in the membrane of the resting T cell is released into the cell medium in soluble form after cell growth activation by phytohemagglutinin or neuraminidase/galactose oxidase treatments. In limited proteolysis by Staphylococcus aureus V8 protease, two major 35-kDa and 27-kDa peptide fragments of the surface-iodinated 45-kDa protein are common to the membrane-bound and the released forms, but a third 18-kDa fragment is observed exclusively with the released protein. The apparent molecular masses of the deglycosylated peptide backbones of the membrane-bound and the released molecule are 30 +/- 1 kDa, although a small size difference cannot be excluded. A polyclonal rabbit anti-(T cell membrane protein) antiserum precipitates the 45-kDa protein. A monoclonal anti-(45-kDa protein) antibody precipitates the membrane-bound 45-kDa protein solubilized with octyl glucoside, but does not precipitate the released protein. In cell culture assays, the monoclonal anti-(45-kDa protein) antibody specifically enhances the cell proliferative responses in phytohemagglutinin-treated and mixed lymphocyte cultures. These observations suggest that the 45-kDa protein has a specific receptor function in the regulation of cell proliferative responses.
mesh_terms: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface / Q000276:immunology*; D002455:Cell Division; D004591:Electrophoresis, Polyacrylamide Gel; D006023:Glycoproteins / Q000032:analysis / Q000276:immunology / Q000502:physiology*; D006801:Humans; D007959:Lymphocyte Culture Test, Mixed; D008565:Membrane Proteins / Q000032:analysis / Q000276:immunology / Q000502:physiology*; D008970:Molecular Weight; D009000:Monocytes / Q000166:cytology* / Q000276:immunology; D017830:Octoxynol; D010455:Peptides / Q000032:analysis; D010835:Phytohemagglutinins / Q000494:pharmacology; D011092:Polyethylene Glycols; D011233:Precipitin Tests; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D000954:Antigens, Surface; D006023:Glycoproteins; D008565:Membrane Proteins; D010455:Peptides; D010835:Phytohemagglutinins; D011092:Polyethylene Glycols; D017830:Octoxynol