[Regulation of a small GTPase Rap2].
Rap2 is a member of Ras-family G proteins and related most closely to Rap1; however little is known about the regulation of Rap2 activity. In this study, I have compared the regulation and function of Rap2 with those of Rap1. In 293T cells, Rap2 was regulated by the same set of guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs) as those which regulated Rap1. Rap2 was localized at both plasma membrane and intracellular membrane compartments, as Rap1 was. Rap2 bound to the Ras-binding domain of Raf and inhibited Ras-dependent activation of Elk1 transcription factor. I have found that the GTP-bound form exceeds 50% of total Rap2 in the cells. This observation suggests that Rap2 suppresses Ras-mediated activation of ERK/MAP kinase cascade in quiescent cells.
Laboratory of Molecular and Cellular Pathology, Department of Neurological Disorder, Division of Neurological Science, Hokkaido University Graduate School of Medicine, Sapporo 060-8638, Japan.
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Ohba
D002478:Cells, Cultured; D020690:GTPase-Activating Proteins / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000502:physiology; D006801:Humans; D020668:rap GTP-Binding Proteins / Q000378:metabolism*; D020827:rap1 GTP-Binding Proteins
D020690:GTPase-Activating Proteins; D020662:Guanine Nucleotide Exchange Factors; C116756:RAP2A protein, human; D020668:rap GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins