Identification of Rap1 as a target for the Crk SH3 domain-binding guanine nucleotide-releasing factor C3G.
C3G, which was identified as a Crk SH3 domain-binding guanine nucleotide-releasing factor, shows sequence similarity to CDC25 and Sos family proteins (S. Tanaka, T. Morishita, Y. Hashimoto, S. Hattori, S. Nakamura, M. Shibuya, K. Matuoka, T. Takenawa, T. Kurata, K. Nagashima, and M. Matsuda, Proc. Natl. Acad. Sci. USA 91:3443-3447, 1994). The substrate specificity of C3G was examined by in vitro and in vivo experiments. C3G markedly stimulated dissociation of bound GDP from Rap1B but marginally affected the same reaction of other Ras family proteins (Ha-Ras, N-Ras, and RalA). C3G also stimulated binding of GTP-gamma S [guanosine 5'-3-O-(thio)triphosphate] to Rap1B. When C3G and Rap1A were expressed in COS7 cells, marked accumulation of the active GTP-bound form of Rap1A was observed, while Sos was not effective in the activation of Rap1A. These results clearly show that C3G is an activator for Rap1. Furthermore, expression of C3G with a membrane localization signal in a v-Ki-ras transformant, DT, induced a reversion of the cells to the flat form, possibly through the activation of endogenous Rap1.
Division of Biochemistry and Cellular Biology, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan.
T
T
Gotoh
S
S
Hattori
S
S
Nakamura
H
H
Kitayama
M
M
Noda
Y
Y
Takai
K
K
Kaibuchi
H
H
Matsui
O
O
Hatase
H
H
Takahashi
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D018797:Cell Cycle Proteins / Q000378:metabolism; D002460:Cell Line; D017931:DNA Primers; D019204:GTP-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D007700:Kinetics; D008565:Membrane Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D050737:Proto-Oncogene Proteins c-crk; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D020664:Son of Sevenless Proteins; D018411:Spodoptera; D013379:Substrate Specificity; D014162:Transfection; D020668:rap GTP-Binding Proteins; D020663:ras Guanine Nucleotide Exchange Factors; D020666:ras-GRF1
D018797:Cell Cycle Proteins; D017931:DNA Primers; D020662:Guanine Nucleotide Exchange Factors; D008565:Membrane Proteins; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D011994:Recombinant Proteins; D020664:Son of Sevenless Proteins; D020663:ras Guanine Nucleotide Exchange Factors; D020666:ras-GRF1; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D010749:Phosphoprotein Phosphatases; D019204:GTP-Binding Proteins; D020668:rap GTP-Binding Proteins