Src-CrkII-C3G-dependent activation of Rap1 switches growth hormone-stimulated p44/42 MAP kinase and JNK/SAPK activities.
We demonstrate here that growth hormone (GH) stimulates the activation of Rap1 and Rap2 in NIH-3T3 cells. Full activation of Rap1 and Rap2 by GH necessitated the combined activity of both JAK2 and c-Src kinases, although c-Src was predominantly required. GH-stimulated Rap1 and Rap2 activity was also demonstrated to be CrkII-C3G-dependent. GH stimulated the tyrosine phosphorylation of C3G, which again required the combined activity of JAK2 and c-Src. C3G tyrosine residue 504 was required for GH-stimulated Rap activation. Activated Rap1 inhibited GH-stimulated activation of RalA and subsequent GH-stimulated p44/42 MAP kinase activity and Elk-1-mediated transcription. In addition, we demonstrated that C3G-Rap1 mediated CrkII enhancement of GH-stimulated JNK/SAPK activity. We have therefore identified a linear JAK2-independent pathway switching GH-stimulated p44/42 MAP kinase and JNK/SAPK activities.
Ling
Ling
L
Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609.
Zhu
Tao
T
Lobie
Peter E
PE
D016475:3T3 Cells; D000818:Animals; D000081247:CSK Tyrosine-Protein Kinase; D020735:Guanine Nucleotide-Releasing Factor 2 / Q000737:chemistry / Q000378:metabolism*; D019382:Human Growth Hormone / Q000494:pharmacology*; D006801:Humans; D053614:Janus Kinase 2; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D050737:Proto-Oncogene Proteins c-crk; D011994:Recombinant Proteins / Q000494:pharmacology; D014443:Tyrosine / Q000737:chemistry; D020668:rap GTP-Binding Proteins / Q000378:metabolism; D020827:rap1 GTP-Binding Proteins / Q000378:metabolism*; D019061:src-Family Kinases
D020735:Guanine Nucleotide-Releasing Factor 2; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D011994:Recombinant Proteins; D019382:Human Growth Hormone; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; C507924:JAK2 protein, human; C507926:Jak2 protein, mouse; D053614:Janus Kinase 2; D019061:src-Family Kinases; C000631346:CSK protein, human; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C116756:RAP2A protein, human; C492137:Rap2a protein, mouse; D020668:rap GTP-Binding Proteins; D020827:rap1 GTP-Binding Proteins