| J Biol Chem 1997 Feb 28;272(9):5600-5 |
RalGDS functions in Ras- and cAMP-mediated growth stimulation. |
Miller MJ, Prigent S, Kupperman E, Rioux L, Park SH, Feramisco JR, White MA, Rutkowski JL, Meinkoth JLDepartment of PharmacologyUniversity of Pennsylvania School of Medicine Philadelphia PA 19104-6084 |
| Thyroid-stimulating hormone stimulates proliferation through both the cAMP-dependent protein kinase and Ras but not through Raf-1 and mitogen-activated and extracellular signal-related kinase kinase. We now report that thyroid-stimulating hormone represses mitogen-activated protein kinase activity and that microinjection of an effector domain mutant Ha-Ras protein, Ras(12V,37G), defective in Raf-1 binding and mitogen-activated protein kinase activation, stimulates DNA synthesis in quiescent and thyroid-stimulating hormone-treated thyrocytes. A yeast two-hybrid screen identified RalGDS as a Ras(12V,37G) binding protein and therefore a potential effector of Ras in these cells. Associations between Ras and RalGDS were observed in extracts prepared from thyroid cells. Microinjection of a mutant RalA(28N) protein thought to sequester RalGDS family members reduced DNA synthesis stimulated by Ras as well as cAMP-mediated DNA synthesis in two cell lines which respond to cAMP with mitogenesis. These results support the idea that RalGDS may be an effector of Ras in cAMP-mediated growth stimulation. |
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