Phosphatidylethanol inhibits phosphatidylinositol-phospholipase C activity in a competitive manner with phosphatidylinositol-4,5-bisphosphate.
The effect of phosphatidylethanol (PEth) on phosphatidylinositol-phospholipase C (PLC) activity was investigated in rat cerebral cortex. PEth decreased PLC activity in both the membrane and the cytosol of the cortex in a concentration-dependent manner, varying from 6 to 400 microM, and PLC activity was almost entirely inhibited at concentrations of PEth over 200 microM (90% inhibition). The IC50 of PEth in the cytosol was 25.2 microM and was 22.1 microM in the membrane. Preincubation of the cytosol with anti-PLC-beta 1, anti-PLC-gamma 1 or anti-PLC-delta 1 antibodies did not prevent the decrease in PLC activity. These results suggest that PEth caused the decrease in PLC activity without isozyme specificity. The sensitivity of PLC to Ca2+ in the cytosol and membrane was not changed by PEth, suggesting that PEth may act on PLC at a site different from that of Ca2+ activation. In higher concentrations of the PLC substrate, PEth did not inhibit PLC activity, indicating that PEth inhibited PLC activity in a substrate competitive manner. Neomycin, which binds to negatively charged phospholipids such as phosphatidylinositol-4,5-bisphosphate (PIP2) and thus causes inhibition of PLC activity, attenuated the PEth-induced decrease in PLC activity. This result suggests that the inhibitory action of PEth on PLC may be related to the fact that PEth is a negatively charged phospholipid similar to PIP2.
Nishida
A
A
Department of Psychiatry and Neuroscience, Institute of Clinical Research, Kure National Hospital, Japan. anishida@kure-nh.go.jp
Saito
H
H
Shimizu
M
M
Zensho
H
H
Yamawaki
S
S
D000818:Animals; D003600:Cytosol / Q000187:drug effects / Q000201:enzymology; D004305:Dose-Response Relationship, Drug; D005625:Frontal Lobe / Q000187:drug effects* / Q000201:enzymology; D020404:Glycerophospholipids; D008297:Male; D009355:Neomycin / Q000494:pharmacology; D010712:Phosphatidic Acids / Q000494:pharmacology*; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000494:pharmacology*; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010727:Phosphoric Diester Hydrolases / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity; D013570:Synaptic Membranes / Q000187:drug effects / Q000201:enzymology
D020404:Glycerophospholipids; D010712:Phosphatidic Acids; D019269:Phosphatidylinositol 4,5-Diphosphate; C051521:phosphatidylethanol; D010727:Phosphoric Diester Hydrolases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D009355:Neomycin