Nuclear signalling by rac GTPase: essential role of phospholipase A2.
Rac, one member of Rho family GTPases, stimulates c-fos serum response element (SRE)-luciferase reporter gene in Rat-2 fibroblast cells. By transient transfection analysis, we demonstrated that the activation of phospholipase A2 (PLA2) and the subsequent production of arachidonic acid (AA) are essential for Rac-induced c-fos SRE activation, implying a critical role for PLA2 in the Rac-signalling pathway to the nucleus. Either pretreatment with mepacrine, a specific inhibitor of PLA2, or co-transfection with the expression plasmid of lipocortin-1, a proposed inhibitory protein of PLA2, selectively abolished RacV12-induced SRE activation. Further, we demonstrated that subsequent metabolism of AA, a major product of Rac-activated PLA2, by lipoxygenase (LO) is essential for Rac-induced c-fos SRE activation. In agreement with the role of the PLA2-AA-LO cascade as a potential mediator of Rac signalling to the nucleus, the addition of exogenous AA stimulated c-fos SRE-luciferase activity in an LO-dependent manner. Together, our results demonstrate that 'Rac-activated PLA2 and subsequent AA metabolism by LO' constitute a novel and specific pathway in Rac GTPase-induced c-fos SRE activation.
Kim
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BC
Laboratory of Molecular and Cellular Genetics, Institute of Environment and Life Science, Hallym University, Kangwon-do, South Korea.
Kim
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JH
D000818:Animals; D017302:Annexins / Q000235:genetics / Q000502:physiology; D016718:Arachidonic Acid / Q000378:metabolism / Q000494:pharmacology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics; D020558:GTP Phosphohydrolases / Q000502:physiology*; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D005786:Gene Expression Regulation; D016762:Genes, fos; D008084:Lipoxygenase / Q000235:genetics / Q000378:metabolism; D008156:Luciferases / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D016376:Oligonucleotides, Antisense / Q000235:genetics; D010741:Phospholipases A / Q000378:metabolism / Q000502:physiology*; D054467:Phospholipases A2; D011518:Proto-Oncogene Proteins / Q000502:physiology; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid / Q000187:drug effects; D026362:Serum Response Factor; D015398:Signal Transduction; D014157:Transcription Factors; D014162:Transfection; D050807:ets-Domain Protein Elk-1; D020744:rac GTP-Binding Proteins
D017302:Annexins; D004268:DNA-Binding Proteins; C494114:Elk1 protein, rat; D009687:Nuclear Proteins; D016376:Oligonucleotides, Antisense; D011518:Proto-Oncogene Proteins; D026362:Serum Response Factor; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D016718:Arachidonic Acid; D008084:Lipoxygenase; D008156:Luciferases; D010741:Phospholipases A; D054467:Phospholipases A2; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins