Non specific effects of guanine nucleotides and polyanions on cytosolic platelet phospholipase C.
Phospholipase C (PLC) partially purified by electrofocusing from human platelet cytosol was incubated with platelet total lipid vesicles containing [3H] phosphatidylinositol 4,5-bis phosphate ([3H]PIP2). Under optimal assay conditions (pH 4.5), PLC activity was stimulated (1.5 to 7 fold) by GTP gamma S, ATP, ADP, GDP beta S, sodium pyrophosphate and AlF4-. With lipid dispersions containing phosphatidylethanolamine and [3H]PIP2, maximal PLC activity was detected at pH 7.4 and was stimulated by micromolar concentrations of free Ca2+. However, no effect of GTP gamma S could be observed under these conditions. This study demonstrates a possible modulation of cytosolic PLC by polyanionic compounds not involving G-proteins and indicates that in vitro data obtained with guanine nucleotides should be considered with caution.
Rossignol
L
L
INSERM U.326, Phospholipides membranaires, Signalisation cellulaire et Lipoprotéines, CHU Purpan, Toulouse, France.
Plantavid
M
M
Mauco
G
G
Chap
H
H
D001792:Blood Platelets / Q000201:enzymology*; D002118:Calcium / Q000494:pharmacology; D003600:Cytosol / Q000201:enzymology*; D004789:Enzyme Activation / Q000187:drug effects; D019204:GTP-Binding Proteins / Q000378:metabolism; D006150:Guanine Nucleotides / Q000494:pharmacology*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006801:Humans; D008081:Liposomes; D008563:Membrane Lipids / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism; D000071228:Polyelectrolytes; D011108:Polymers / Q000494:pharmacology*; D015290:Second Messenger Systems; D010738:Type C Phospholipases / Q000378:metabolism*
D002118:Calcium; D019204:GTP-Binding Proteins; D006150:Guanine Nucleotides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D008081:Liposomes; D008563:Membrane Lipids; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D000071228:Polyelectrolytes; D011108:Polymers; D010738:Type C Phospholipases