Crk protein binds to PDGF receptor and insulin receptor substrate-1 with different modulating effects on PDGF- and insulin-dependent signaling pathways.
We have studied the involvement of murine c-Crk, an SH2/SH3 containing adaptor protein, in signaling pathways stimulated by different receptor tyrosine kinases. We show here that c-Crk is associated with components of insulin- and PDGF-dependent signaling pathways. Insulin treatment of murine myoblast cells induces the formation of stable complex of endogenous c-Crk with insulin receptor substrate-1 (IRS-1) mediated via the SH2 domain of Crk. The ligand dependent physical association of c-Crk with IRS-1 is direct. However IRS-1 is also co-precipitated with c-Crk from quiescent L6 cells. The association of IRS-1 with c-Crk in quiescent cells is probably not direct since Far Western blot analysis did not reveal the binding of neither SH2 domain nor amino-terminal SH3 domain of c-Crk to IRS-1 from unstimulated cells. We also show that PDGF treatment of murine myoblast cells induces association of c-Crk with the PDGF receptor and tyrosine phosphorylation of c-Crk. Overexpression of c-Crk enhanced insulin- but not PDGF-induced activation of MAP kinases when compared to parental cell lines. Thus, the formation of the direct IRS-1/Crk complex appears to be crucial for Crk-mediated insulin-induced activation of MAP kinase, whereas Crk is probably involved in other PDGF-induced responses. These data provide support to the hypothesis that insulin and PDGF employ different mechanisms for activation of MAP kinase cascade.
Sorokin
A
A
Department of Medicine, Medical College of Wisconsin, Milwaukee 53226-0509, USA.
Reed
E
E
Nnkemere
N
N
Dulin
N O
NO
Schlessinger
J
J
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002460:Cell Line; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D055504:Insulin Receptor Substrate Proteins; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010750:Phosphoproteins / Q000378:metabolism*; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D011506:Proteins / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D050737:Proto-Oncogene Proteins c-crk; D051381:Rats; D011972:Receptor, Insulin / Q000378:metabolism*; D017479:Receptors, Platelet-Derived Growth Factor / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000378:metabolism
C493872:Crk protein, rat; D020662:Guanine Nucleotide Exchange Factors; C526292:IRS1 protein, human; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526295:Irs1 protein, mouse; C526296:Irs1 protein, rat; D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; D011506:Proteins; D011518:Proto-Oncogene Proteins; D050737:Proto-Oncogene Proteins c-crk; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D011972:Receptor, Insulin; D017479:Receptors, Platelet-Derived Growth Factor; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases