Phosphatidic acid induces actin polymerization by activating protein kinases in soybean cells.
Phosphatidic acid (PA) levels rise in response to wounding, stress and elicitors, suggesting that it mediates defense responses in plants. During such responses, actin filaments are altered. Since PA induces actin polymerization in animal cells we examined its effect on actin structures in suspension-cultured soybean cells. PA caused a three to four fold increase in cells containing filamentous actin. Immunoblotting with anti-actin antibody showed that actin polymerized within 30 min of treatment. The effect of PA on actin polymerization appears to be mediated by protein kinases because: 1) the effect was suppressed by staurosporin, a general protein kinase inhibitor, and by the protein kinase C-specific inhibitor, calphostin, 2) calyculin A, an inhibitor of protein phosphatase 1 and 2A, mimicked the effect of PA on actin polymerization, and 3) PA activated protein kinases in soybean cells. We suggest that a 54 kDa Ca2+-dependent protein kinase may transduce the PA signal because EGTA inhibited the 54 kDa kinase and the PA-induced actin polymerization, and similar protein kinases have been reported to co-localize with and regulate actin filaments. Our results support the role of PA as a signal mediator and identify actin as a downstream target of PA.
Lee
Sumin
S
Division of Molecular and Life Science, Pohang University of Science and Technology, Pohang 790-784, Korea.
Park
Jumok
J
Lee
Youngsook
Y
D008841:Actin Cytoskeleton / Q000187:drug effects / Q000378:metabolism; D000199:Actins / Q000378:metabolism* / Q000648:ultrastructure; D002478:Cells, Cultured; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008387:Marine Toxins; D009281:Naphthalenes / Q000494:pharmacology; D010080:Oxazoles / Q000494:pharmacology; D010712:Phosphatidic Acids / Q000378:metabolism / Q000494:pharmacology*; D010940:Plant Proteins; D011108:Polymers / Q000378:metabolism; D047428:Protein Kinase Inhibitors; D011494:Protein Kinases / Q000096:biosynthesis*; D012097:Repressor Proteins / Q000037:antagonists & inhibitors; D013025:Glycine max; D019311:Staurosporine / Q000494:pharmacology
D000199:Actins; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D009281:Naphthalenes; D010080:Oxazoles; C500847:P58IPK protein, plant; D010712:Phosphatidic Acids; D010940:Plant Proteins; D011108:Polymers; D047428:Protein Kinase Inhibitors; D012097:Repressor Proteins; C061465:calphostin complex; D004533:Egtazic Acid; C059041:calyculin A; D011494:Protein Kinases; D019311:Staurosporine