Platelet-activating factor stimulation of tyrosine kinase and its relationship to phospholipase C in rabbit platelets: Studies with genistein and monoclonal antibody to phosphotyrosine

Journal Article · Sat Mar 31 23:00:00 EST 1990 · Molecular Pharmacology; (USA)

OSTI ID:6896839

Dhar, A; Paul, A K; Shukla, S D ^[1]

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1. Univ. of Missouri-Columbia (USA)

Platelet-activating factor (PAF) is a proinflammatory lipid that has platelet-stimulating property. PAF receptor-coupled activation of phosphoinositide-specific phospholipase C (PLC) and phosphorylation of several proteins has already been established in our laboratory. To investigate further the molecular mechanism and relationship between activation of PLC and protein phosphorylation, we have used Genistein (a putative inhibitor of tyrosine-specific protein kinases), phosphotyrosine antibody, and phosphoamino acid analysis to probe the involvement of tyrosine kinase in this process. Washed rabbit platelets were loaded with myo-(2-3H)inositol and challenged with PAF (100 nM) after pretreatment with Genistein. PLC-mediated production of radioactive inositol monophosphate, inositol diphosphate, and inositol triphosphate was monitored. PAF alone caused stimulation of PLC activity (( 3H)inositol triphosphate production), whereas pretreatment with Genistein (0.5 mM) diminished PAF-stimulated PLC activity to basal level. Genistein also blocked PAF-stimulated platelet aggregation at this dose. In contrast to Genistein, staurosporine which inhibits protein kinase C, potentiated PAF-stimulated (3H)inositol triphosphate production. Genistein substantially inhibited the combined effects of staurosporine and PAF on inositol triphosphate production. Genistein also reduced PAF-induced phosphorylation of Mr 20,000 and 50,000 proteins. Phorbol 12-myristate 13-acetate-induced Mr 40,000 protein phosphorylation was also affected by Genistein. The above results suggested that Genistein inhibited tyrosine kinase at an early stage of signal transduction by inhibiting PLC. This, in turn, decreased the activation of protein kinase C and, therefore, caused a reduction in Mr 40,000 protein phosphorylation.

• OSTI ID: 6896839
• Journal Information: Molecular Pharmacology; (USA), Journal Name: Molecular Pharmacology; (USA) Vol. 37:4; ISSN 0026-895X; ISSN MOPMA
• Country of Publication: United States
• Language: English

Related Subjects

550201* -- Biochemistry-- Tracer Techniques
560300 -- Chemicals Metabolism & Toxicology
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINO ACIDS
ANIMALS
ANTIBODIES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BLOOD COAGULATION FACTORS
BLOOD PLATELETS
BODY FLUIDS
CARBOXYLESTERASES
CARBOXYLIC ACIDS
CARCINOGENS
CHEMICAL REACTIONS
COAGULANTS
DRUGS
ENZYME ACTIVITY
ENZYME INHIBITORS
ENZYMES
ESTERASES
ESTERS
HEMATOLOGIC AGENTS
HYDROGEN COMPOUNDS
HYDROLASES
HYDROXY ACIDS
INHIBITION
ISOTOPE APPLICATIONS
KINETICS
LIPASES
MAMMALS
MATERIALS
MEMBRANE PROTEINS
MONOCLONAL ANTIBODIES
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHORBOL ESTERS
PHOSPHORUS-GROUP TRANSFERASES
PHOSPHORYLATION
PHOSPHOTRANSFERASES
PROTEINS
RABBITS
REACTION KINETICS
RECEPTORS
TRACER TECHNIQUES
TRANSFERASES
TRITIUM COMPOUNDS
TYROSINE
VERTEBRATES