title: CalDAG-GEFIII activation of Ras, R-ras, and Rap1.
abstract: We characterized a novel guanine nucleotide exchange factor (GEF) for Ras family G proteins that is highly homologous to CalDAG-GEFI, a GEF for Rap1 and R-Ras, and to RasGRP/CalDAG-GEFII, a GEF for Ras and R-Ras. This novel GEF, referred to as CalDAG-GEFIII, increased the GTP/GDP ratio of Ha-Ras, R-Ras, and Rap1 in 293T cells. CalDAG-GEFIII promoted the guanine nucleotide exchange of Ha-Ras, R-Ras, and Rap1 in vitro also, indicating that CalDAG-GEFIII exhibited the widest substrate specificity among the known GEFs for Ras family G proteins. Expression of CalDAG-GEFIII was detected in the glial cells of the brain and the glomerular mesangial cells of the kidney by in situ hybridization. CalDAG-GEFIII activated ERK/MAPK most efficiently, followed by CalDAG-GEFII and CalDAG-GEFI in 293T cells. JNK activation was most prominent in cells expressing CalDAG-GEFII, followed by CalDAG-GEFIII and CalDAG-GEFI. Expression of CalDAG-GEFIII induced neuronal differentiation of PC12 cells and anchorage-independent growth of Rat1A cells less efficiently than did CalDAG-GEFII. Thus, co-activation of Rap1 by CalDAG-GEFIII apparently attenuated Ras-MAPK-dependent neuronal differentiation and cellular transformation. Altogether, CalDAG-GEFIII activated a broad range of Ras family G proteins and exhibited a biological activity different from that of either CalDAG-GEFI or CalDAG-GEFII.
authors.affiliation: Department of Pathology, Research Institute, International Medical Center of Japan, Tokyo.
authors.forename: S
authors.initials: S
authors.lastname: Yamashita
authors.forename: N
authors.initials: N
authors.lastname: Mochizuki
authors.forename: Y
authors.initials: Y
authors.lastname: Ohba
authors.forename: M
authors.initials: M
authors.lastname: Tobiume
authors.forename: Y
authors.initials: Y
authors.lastname: Okada
authors.forename: H
authors.initials: H
authors.lastname: Sawa
authors.forename: K
authors.initials: K
authors.lastname: Nagashima
authors.forename: M
authors.initials: M
authors.lastname: Matsuda
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002460:Cell Line; D018076:DNA, Complementary / Q000378:metabolism; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D005920:Glomerular Mesangium / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000096:biosynthesis / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D017403:In Situ Hybridization; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008969:Molecular Sequence Data; D009457:Neuroglia / Q000378:metabolism; D009474:Neurons / Q000378:metabolism; D016716:PC12 Cells; D010802:Phylogeny; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013379:Substrate Specificity; D014018:Tissue Distribution; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*; D020663:ras Guanine Nucleotide Exchange Factors; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D020662:Guanine Nucleotide Exchange Factors; C413212:RASGRP3 protein, human; D011994:Recombinant Proteins; D020663:ras Guanine Nucleotide Exchange Factors; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D020558:GTP Phosphohydrolases; D019204:GTP-Binding Proteins; C085929:RRAS protein, human; D020827:rap1 GTP-Binding Proteins; D018631:ras Proteins