Downstream of Crk adaptor signaling pathway: activation of Jun kinase by v-Crk through the guanine nucleotide exchange protein C3G.
Crk, which belongs to the adaptor family of proteins composed of Src homology 2 (SH2) and SH3 domains, has a putative role in signaling. However, the downstream events of Crk signaling remain unclear. In this study, we found that Jun kinase (JNK) is moderately activated by v-Crk in both NIH 3T3 cells and chicken embryo fibroblasts. Transient expression of v-Crk, c-Crk-I, or c-Crk-II activated JNK1 in human embryo kidney cells, 293T. Coexpression of a guanine nucleotide exchange protein C3G, which specifically binds to Crk's SH3 domain, further enhanced the JNK activity as well as growth rate and anchorage-independent growth of v-Crk NIH 3T3 cells. Furthermore, overexpression of a dominant-negative form of C3G lacking the guanine nucleotide exchange domain abolished both the JNK activity and the colony forming potential of v-Crk NIH 3T3 cells. The requirement for JNK activation in v-Crk induced transformation was demonstrated by the suppression of colony forming activity of v-Crk NIH 3T3 cells when a dominant-negative form of JNK kinase, Sek1/MKK4 is expressed in these cells. These data strongly suggest the existence of a novel signaling cascade involving an adaptor protein v-Crk, which transmits signals through C3G toward JNK activation.
Tanaka
S
S
Laboratory of Molecular Oncology, The Rockefeller University, New York, NY 10021-6399, USA.
Ouchi
T
T
Hanafusa
H
H
D016475:3T3 Cells; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002455:Cell Division; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D002642:Chick Embryo; D004789:Enzyme Activation; D005347:Fibroblasts; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases; D051379:Mice; D020928:Mitogen-Activated Protein Kinases; D008954:Models, Biological; D050736:Oncogene Protein v-crk; D011506:Proteins / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D015682:Retroviridae Proteins, Oncogenic / Q000378:metabolism*; D015398:Signal Transduction; D014162:Transfection; D018909:src Homology Domains
D020662:Guanine Nucleotide Exchange Factors; D050736:Oncogene Protein v-crk; D011506:Proteins; D011994:Recombinant Proteins; D015682:Retroviridae Proteins, Oncogenic; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases