title: CD43 regulates tyrosine phosphorylation of a 93-kD protein in T lymphocytes.
abstract: The leukocyte sialyloglycoprotein CD43 exhibits features of a signal transducing molecule and is thought to be important for T-cell activation and adhesion. However, cellular biochemical events in which CD43 participates remain poorly understood. Here we provide evidence that CD43 regulates tyrosine phosphorylation of a specific substrate in T cells. A 93-kD tyrosine phosphoprotein was identified specifically in the CD43+ T-cell line CEM, but not in their CD43-deficient counterparts derived by gene targeting. The 93-kD phosphoprotein was detected in the CD43-deficient CEM cells after transfection with CD43 cDNA, and it could be specifically phosphorylated in lysates from the CD43-deficient cells by incubation with a CD43 immunoprecipitate obtained from the CD43+ cells. Expression of CD43 in HeLa cell transfectants was associated with the appearance of novel phosphoproteins including one with a molecular weight of approximately 93 kD, confirming that tyrosine phosphorylation of cellular substrates results specifically from CD43 expression. We conclude that CD43 regulates tyrosine phosphorylation of a 93-kD T-cell substrate.
mesh_terms: D015703:Antigens, CD; D002460:Cell Line; D018390:Gene Targeting; D006367:HeLa Cells; D006801:Humans; D051917:Leukosialin; D008970:Molecular Weight; D010766:Phosphorylation; D011506:Proteins / Q000737:chemistry / Q000378:metabolism*; D012795:Sialoglycoproteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000276:immunology* / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D051917:Leukosialin; D011506:Proteins; C465014:SPN protein, human; D012795:Sialoglycoproteins; D014443:Tyrosine