Rac GTPase activity is essential for EGF-induced mitogenesis.
Rac, a member of the Rho family GTPases, has been implicated in the regulation of a wide range of biological processes including actin remodeling, cell transformation, G1 cell cycle progression, and gene expression. To determine whether Rac GTPase activity is required for epidermal growth factor-induced mitogenesis, Rat-2 stable cells expressing a dominant-negative Rac1 mutant, RacN17, were prepared. Exposure to EGF exhibited a significantly restricted growth response in Rat-2-RacN17 cells compared to Rat-2 parental cells, suggesting an essential role of Rac in EGF-induced mitogenesis. In contrast, addition of lysophosphatidic acid exerted the same level of growth in Rat-2 and Rat-2-RacN17 cells. To gain further evidence for the essential role of Rac in EGF-induced mitogenesis, we performed the microinjection experiment. EGF-induced DNA synthesis was significantly blocked by microinjection of recombinant RacN17 protein, and not control IgG. Our further study to analyze the downstream mediator of Rac in EGF-signaling to mitogenesis demonstrated that Rac-activated phospholipase A2 plays a critical role. Taken together, our results suggest that the "Rac and Rac-activated PLA2" cascade is one of the major mitogenic pathways induced by EGF.
Kim
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Institute of Environment & Life Science, Hallym University, Kangwon-do, Korea. jhkim@sun.hallym.ac.kr
Yi
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Yi
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Shin
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Jhun
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Hwang
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Kim
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D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005347:Fibroblasts; D020558:GTP Phosphohydrolases / Q000378:metabolism* / Q000502:physiology; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D006131:Growth Inhibitors / Q000502:physiology; D008845:Microinjections; D008934:Mitogens / Q000494:pharmacology*; D008938:Mitosis / Q000187:drug effects* / Q000235:genetics; D010741:Phospholipases A / Q000378:metabolism / Q000502:physiology; D054467:Phospholipases A2; D051381:Rats; D011994:Recombinant Proteins / Q000494:pharmacology; D020744:rac GTP-Binding Proteins
D006131:Growth Inhibitors; D008934:Mitogens; D011994:Recombinant Proteins; D004815:Epidermal Growth Factor; D004247:DNA; D010741:Phospholipases A; D054467:Phospholipases A2; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins