Activation of actin polymerization by phosphatidic acid derived from phosphatidylcholine in IIC9 fibroblasts.
alpha-Thrombin induced a change in the cell morphology of IIC9 fibroblasts from a semiround to an elongated form, accompanied by an increase in stress fibers. Incubation of the cells with phospholipase D (PLD) from Streptomyces chromofuscus and exogenous phosphatidic acid (PA) caused similar morphological changes, whereas platelet-derived growth factor (PDGF) and phorbol 12-myristate 13-acetate (PMA) induced different changes, e.g., disruption of stress fibers and cell rounding. alpha-Thrombin, PDGF, and exogenous PLD increased PA by 20-40%, and PMA produced a smaller increase. alpha-Thrombin and exogenous PLD produced rapid increases in the amount of filamentous actin (F-actin) that were sustained for at least 60 min. However, PDGF produced a transient increase of F-actin at 1 min and PMA caused no significant change. Dioctanoylglycerol was ineffective except at 50 micrograms/ml. Phospholipase C from Bacillus cereus, which increased diacylglycerol (DAG) but not PA, did not change F-actin content. Down-regulation of protein kinase C (PKC) did not block actin polymerization induced by alpha-thrombin. H-7 was also ineffective. Exogenous PA activated actin polymerization with a significant effect at 0.01 microgram/ml and a maximal increase at 1 microgram/ml. No other phospholipids tested, including polyphosphoinositides, significantly activated actin polymerization. PDGF partially inhibited PA-induced actin polymerization after an initial increase at 1 min. PMA completely or largely blocked actin polymerization induced by PA or PLD. These results show that PC-derived PA, but not DAG or PKC, activates actin polymerization in IIC9 fibroblasts, and indicate that PDGF and PMA have inhibitory effects on PA-induced actin polymerization.
Ha
K S
KS
Howard Hughes Medical Institute, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0295.
Exton
J H
JH
D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D000818:Animals; D001409:Bacillus cereus / Q000201:enzymology; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004075:Diglycerides / Q000494:pharmacology; D004622:Embryo, Mammalian; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D007700:Kinetics; D010712:Phosphatidic Acids / Q000378:metabolism* / Q000494:pharmacology*; D010713:Phosphatidylcholines / Q000378:metabolism*; D010739:Phospholipase D / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C; D013302:Streptomyces / Q000201:enzymology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013917:Thrombin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism / Q000494:pharmacology
D000199:Actins; D004075:Diglycerides; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D010982:Platelet-Derived Growth Factor; C044295:1,2-dioctanoylglycerol; D011493:Protein Kinase C; D010738:Type C Phospholipases; D010739:Phospholipase D; D013917:Thrombin; D013755:Tetradecanoylphorbol Acetate