Effect of lovastatin and fluoromevalonate on phosphatidylinositol 3-kinase activity stimulated with PDGF.
1. Phosphatidylinositol 3-kinase (PI3K) appears to have a crucial role in cellular proliferation induced by platelet-derived growth factor (PDGF). However, the mode of activation of the enzyme has been unclear so far. In the present study, we investigated the effects of a cholesterol lowering drug on [3H]-thymidine ([3H]-TdR) incorporation and PI3K activity in cultured vascular smooth muscle cells (VSMC) stimulated with PDGF. 2. PDGF stimulated both [3H]-TdR incorporation and PI3K activity immunoprecipitated with antiphosphotyrosine antibody in a dose dependent manner (ED50 was 4 ng/mL for [3H]-TdR uptake and 3 ng/mL for PI3K activity). Lovastatin inhibited serum-stimulated [3H]-TdR incorporation dose dependently. PI3K activity induced by PDGF was also inhibited in a dose dependent manner; however, its activity was 61% at 10(-6) mol/L, 72% at 10(-5) mol/L and 8% at 10(-4) mol/L of the control value. 3. These inhibitory effects of lovastatin were completely abolished by adding 1 mmol/L mevalonic acid (MVA), suggesting that MVA metabolites had some important role on the PI3K activation and cellular proliferation. 4. Fluoromevalonate (Fmev), a competitive inhibitor of mevalonate diphosphate (MVA-PP) decarboxylase, inhibited [3H]-TdR incorporation at concentrations more than 10(-6) mol/L. Moreover, marked inhibitory effect was observed at concentrations of 10(-7) and 10(-8) mol/L (76% of control). PI3K activity was also reduced by 10(-3) mol/L Fmev (0.2% of control). However, in contrast to [3H]-TdR uptake, there was no inhibitory effect detected at concentrations up to 10(-4) mol/L. 5. These results suggest that PDGF-stimulated PI3K activity as well as cellular proliferation was modified by protein isoprenylation.
Iwama
A
A
Graduate School of Human and Environmental Studies, Kyoto University, Japan.
Sawamura
M
M
Nara
Y
Y
Yamori
Y
Y
D000818:Animals; D000924:Anticholesteremic Agents / Q000494:pharmacology*; D001013:Aorta, Thoracic / Q000187:drug effects; D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors; D002455:Cell Division / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D066298:In Vitro Techniques; D008148:Lovastatin / Q000494:pharmacology*; D008297:Male; D008798:Mevalonic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D013936:Thymidine / Q000378:metabolism
D000924:Anticholesteremic Agents; D004791:Enzyme Inhibitors; D010982:Platelet-Derived Growth Factor; C045174:6-fluoromevalonolactone; D008148:Lovastatin; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D002262:Carboxy-Lyases; C022503:pyrophosphomevalonate decarboxylase; D008798:Mevalonic Acid; D013936:Thymidine