Fodrin inhibits phospholipases A2, C, and D by decreasing polyphosphoinositide cell content.
Brain fodrin inhibited in a dose dependent manner the GTPgammaS-stimulated cytosolic PLA2 (cPLA2), PLC, and PLD activities in differentiated HL-60 cells permeabilized with streptolysin O. cPLA2 and PLD were inhibited by the same concentrations of fodrin (IC50=1.5-2 nM) but PLC was inhibited by lower concentrations (IC50=0.3 nM). Moreover, the rates of inhibition were different between the phospholipases. Spectrin, which shares 50% homology with fodrin, had similar effects on the three phospholipases. However, using cytosol-depleted cells or recombinant PLD1, we showed that fodrin was not a direct inhibitor. Studying the potential mechanisms of these inhibitions, we demonstrated that a major decrease in membrane phosphatidylinositol 4-monophosphate (PtdIns(4)P) and phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) amounts was induced by fodrin. Exogenous PtdIns(4,5)P2 partly reversed fodrin inhibition of GTPgammaS-stimulated phospholipase C activity. Hence, inhibition of PLC, cPLA2, and PLD activities observed with fodrin could be related to the decrease of PtdIns(4,5)P2, substrate of PLC, a cofactor of PLD and an enhancer of cPLA2 activity.
Unité INSERM 332, ICGM, 22 rue Méchain, Paris, 75014, Paris, France.
S
S
Lukowski
J P
JP
Mira
A
A
Zachowski
B
B
Geny
D002352:Carrier Proteins / Q000494:pharmacology*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006160:Guanosine Triphosphate / Q000494:pharmacology; D018922:HL-60 Cells / Q000201:enzymology; D006801:Humans; D008840:Microfilament Proteins / Q000494:pharmacology*; D009419:Nerve Tissue Proteins / Q000494:pharmacology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism / Q000494:pharmacology; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010739:Phospholipase D / Q000037:antagonists & inhibitors*; D010741:Phospholipases A / Q000037:antagonists & inhibitors*; D054467:Phospholipases A2; D011994:Recombinant Proteins / Q000378:metabolism; D013049:Spectrin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors*
D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D006160:Guanosine Triphosphate; D008840:Microfilament Proteins; D009419:Nerve Tissue Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D010739:Phospholipase D; D010741:Phospholipases A; D054467:Phospholipases A2; D011994:Recombinant Proteins; D013049:Spectrin; D010738:Type C Phospholipases; C037178:phosphatidylinositol 4-phosphate