title: Platelet-activating factor stimulates calcium-dependent activation of protein-tyrosine kinase Syk in a human B cell line.
abstract: In ASK.0 B lymphoblastoid cells, platelet activating factor (PAF) induced a rapid increase in Syk protein-tyrosine kinase activity which was insensitive to pertussis toxin (PTX) but was abolished by the phopholipase C inhibitor, U73122. In parallel, PAF-induced Ca2+ mobilization was also insensitive to PTX and was almost completely inhibited by U73122. Incubation of ASK.0 cells with the compounds that increase intracellular Ca2+ (i.e., the ionophore A23187, thapsigargin which releases Ca2+ from internal store) mimicked the effect of PAF on Syk kinase activity. Loading cells with the intracellular Ca2+ chelator, bis-(O-aminophenoxy)-ethane-N,N,N',N'-tetraacetoxymethyl ester (BAPTAAM), completely inhibited the activation of Syk kinase in response to PAF, thapsigargin and ionophore. These results suggest that intracellular free Ca2+ seems to be critical for PAF-induced activation of Syk kinase in human B lymphoblastoid cells.
authors.affiliation: Department of Biochemistry, Kobe University School of Medicine, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Rezaul
authors.forename: K
authors.initials: K
authors.lastname: Sada
authors.forename: T
authors.initials: T
authors.lastname: Inazu
authors.forename: H
authors.initials: H
authors.lastname: Yamamura
mesh_terms: D001402:B-Lymphocytes / Q000187:drug effects / Q000201:enzymology*; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism*; D004963:Estrenes / Q000494:pharmacology; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007476:Ionophores / Q000494:pharmacology; D037342:Pertussis Toxin; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D010972:Platelet Activating Factor / Q000494:pharmacology*; D010980:Platelet Membrane Glycoproteins / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011760:Pyrrolidinones / Q000494:pharmacology; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D000072377:Syk Kinase; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D002614:Chelating Agents; D004792:Enzyme Precursors; D004963:Estrenes; D047908:Intracellular Signaling Peptides and Proteins; D007476:Ionophores; D010726:Phosphodiesterase Inhibitors; D010972:Platelet Activating Factor; D010980:Platelet Membrane Glycoproteins; D011760:Pyrrolidinones; D011956:Receptors, Cell Surface; D043562:Receptors, G-Protein-Coupled; D010566:Virulence Factors, Bordetella; C039351:platelet activating factor receptor; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C070379:1,2-bis(2-aminophenoxy)ethane N,N,N',N'-tetraacetic acid acetoxymethyl ester; D000001:Calcimycin; D004533:Egtazic Acid; D037342:Pertussis Toxin; D011505:Protein-Tyrosine Kinases; C000606896:SYK protein, human; D000072377:Syk Kinase; D010738:Type C Phospholipases; D002118:Calcium