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GDP beta S enhances the activation of phospholipase C caused by thrombin in human platelets: evidence for involvement of an inhibitory GTP-binding protein

Journal Article · · Biochem. Biophys. Res. Commun.; (United States)
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Guanosine 5'-O-thiotriphosphate (GTP gamma S) and thrombin stimulate the activity of phospholipase C in platelets that have been permeabilized with saponin and whose inositol phospholipids have been prelabeled with (/sup 3/H)inositol. Ca/sup 2 +/ has opposite effects on the formation of (/sup 3/H)inositol phosphates induced by thrombin or GTP gamma S. While the action of GTP gamma S on the formation of (/sup 3/H)inositol phosphates is inhibited by Ca/sup 2 +/, action of thrombin is stimulated by Ca/sup 2 +/. Guanosine 5'-O-(2-thiodiphosphate) (GDP beta S), which inhibits the function of GTP-binding proteins, also inhibits the effect of GTP gamma S on phospholipase C stimulation but, surprisingly, increases the effect of thrombin. Ca/sup 2 +/ increases the inhibitory effect of GDP beta S on GTP gamma S activation of phospholipase C, but Ca/sup 2 +/ further enhances the stimulatory effect of GDP beta S on the thrombin activation of phospholipase C. This indicates that two mechanisms are responsible for the activation of phospholipase C in platelets. A GTP-binding protein is responsible for regulation of phospholipase C induced by GTP gamma S, while the effect of thrombin on the stimulation of phospholipase C is independent of GTP-binding proteins. However, the effect of thrombin may be modulated by the action of an inhibitory GTP-binding protein.
Research Organization:
Burroughs Wellcome Co., Research Triangle Park, NC
OSTI ID:
6409542
Journal Information:
Biochem. Biophys. Res. Commun.; (United States), Journal Name: Biochem. Biophys. Res. Commun.; (United States) Vol. 3; ISSN BBRCA
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ALKALINE EARTH METAL COMPOUNDS
AROMATICS
AZAARENES
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BLOOD
BLOOD CELLS
BLOOD PLATELETS
BODY FLUIDS
CALCIUM COMPOUNDS
CARBOHYDRATES
COAGULANTS
DRUGS
ENZYME ACTIVITY
ENZYMES
GLYCOSIDES
GUANOSINE
HEMATOLOGIC AGENTS
HEMOSTATICS
HETEROCYCLIC COMPOUNDS
HYDROLASES
INOSITOL
INOSITOLS
KINETICS
LABELLED COMPOUNDS
MATERIALS
MONOSACCHARIDES
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PEPTIDE HYDROLASES
PURINES
REACTION KINETICS
RIBOSIDES
SACCHARIDES
SAPONINS
SERINE PROTEINASES
THROMBIN
TRITIUM COMPOUNDS