title: Characterization of the 50 kDa protein phosphorylated in concanavalin A-stimulated mouse T cells.
abstract: Concanavalin A (Con A) stimulated the phosphorylation of a protein with a molecular mass of 50 kDa and an approximate pI of 4.7 (p50) in mouse spleen T cells. The phosphorylation of p50 was also stimulated by a protein kinase C activator, phorbol myristate acetate (PMA), but not by a calcium ionophore, A23187. This phosphorylation of p50 was limited to serine and threonine residues in both Con A- and PMA-stimulated T cells. Purification and protein sequence analysis of p50 enabled us to identify it as a lymphocyte-specific putative Ca(2+)-binding protein (LSP-1). These results suggest that p50 may have some function, which is regulated through serine/threonine phosphorylation and the intracellular Ca2+ concentration, downstream of the phosphoinositide signaling system in the T cell activation cascade.
authors.affiliation: Department of Chemical Toxicology and Immunochemistry, Faculty of Pharmaceutical Sciences, University of Tokyo.
authors.forename: N
authors.initials: N
authors.lastname: Matsumoto
authors.forename: S
authors.initials: S
authors.lastname: Toyoshima
authors.forename: T
authors.initials: T
authors.lastname: Osawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003208:Concanavalin A / Q000494:pharmacology*; D015180:Electrophoresis, Gel, Two-Dimensional; D005260:Female; D008213:Lymphocyte Activation; D051379:Mice; D008840:Microfilament Proteins; D008969:Molecular Sequence Data; D008970:Molecular Weight; D010766:Phosphorylation; D010768:Phosphoserine / Q000032:analysis; D010769:Phosphothreonine / Q000032:analysis; D016415:Sequence Alignment; D013154:Spleen / Q000166:cytology; D013601:T-Lymphocytes / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D002135:Calcium-Binding Proteins; C057701:Lsp1 protein, mouse; D008840:Microfilament Proteins; D003208:Concanavalin A; D010769:Phosphothreonine; D010768:Phosphoserine; D000001:Calcimycin; D013755:Tetradecanoylphorbol Acetate