CRK protein binds to two guanine nucleotide-releasing proteins for the Ras family and modulates nerve growth factor-induced activation of Ras in PC12 cells.
It has been reported that growth factors activate Ras through a complex of an adaptor type SH2-containing molecule, Grb2, and a Ras guanine nucleotide-releasing protein (GNRP), mSos. We report on the involvement of another adaptor molecule, CRK, in the activation of Ras. Overexpression of wild-type CRK proteins CRK-I and CRK-II enhanced the nerve growth factor (NGF)-induced activation of Ras in PC12 cells, although the basal level of GTP-bound active Ras was not altered. In contrast, mutants with a single amino acid substitution in either the SH2 or SH3 domain of the CRK-I protein inhibited the NGF-induced activation of Ras. Two GNRPs for the Ras family, mSos and C3G, were coimmunoprecipitated with the endogenous Crk proteins in PC12 cells. The association between C3G and the CRK mutants was dependent upon the presence of intact SH3. The SH2 domain of CRK bound to the SHC protein phosphorylated on tyrosine residues by NGF stimulation. The results demonstrate that, in addition to Grb2, CRK participates in signaling from the NGF receptor and that two GNRPs appear to transmit signals from these adaptor molecules to Ras.
Department of Pathology, National Institute of Health, Tokyo, Japan.
M
M
Matsuda
Y
Y
Hashimoto
K
K
Muroya
H
H
Hasegawa
T
T
Kurata
S
S
Tanaka
S
S
Nakamura
S
S
Hattori
D000818:Animals; D004789:Enzyme Activation; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D066298:In Vitro Techniques; D009414:Nerve Growth Factors / Q000494:pharmacology; D016716:PC12 Cells; D011485:Protein Binding; D011494:Protein Kinases; D011506:Proteins / Q000378:metabolism*; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D015800:Protozoan Proteins / Q000378:metabolism*; D011817:Rabbits; D015398:Signal Transduction; D020663:ras Guanine Nucleotide Exchange Factors
C077833:CRK protein, protozoan; D020662:Guanine Nucleotide Exchange Factors; D009414:Nerve Growth Factors; D011506:Proteins; D015800:Protozoan Proteins; D020663:ras Guanine Nucleotide Exchange Factors; D011494:Protein Kinases; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)