Role of transactivation of the EGF receptor in signalling by G-protein-coupled receptors.
Transduction of a mitogenic signal from the cell membrane to the nucleus involves the adapter proteins SHC and Grb2, which mediate activation of the Ras/mitogen-activated protein (MAP) kinase pathway. In contrast to receptor tyrosine kinases (RTKs), the signalling steps leading to Ras/MAP kinase activation by G-protein-coupled receptors (GPCRs) are still poorly characterized but appear to include beta gamma subunits of heterotrimeric G-proteins and as-yet unidentified tyrosine kinases. We report here that the epidermal growth factor receptor (EGFR) and the neu oncoprotein become rapidly tyrosine-phosphorylated upon stimulation of Rat-1 cells with the GPCR agonists endothelin-1, lysophosphatic acid and thrombin, suggesting that there is an intracellular mechanism for transactivation. Specific inhibition of EGFR function by either the selective tyrphostin AG1478 or a dominant-negative EGFR mutant suppressed MAP kinase activation and strongly inhibited induction of fos gene expression and DNA synthesis. Our results demonstrate a role for RTKs as downstream mediators in GPCR mitogenic signalling and suggest a ligand-independent mechanism of RTK activation through intracellular signal crosstalk.
Daub
H
H
Department of Molecular Biology, Max-Planck-Institut für Biochemie, Martinsried, Germany.
Weiss
F U
FU
Wallasch
C
C
Ullrich
A
A
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D065128:Endothelin Receptor Antagonists; D016232:Endothelins / Q000494:pharmacology; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010456:Peptides, Cyclic / Q000494:pharmacology; D010766:Phosphorylation; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000187:drug effects / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D013917:Thrombin / Q000494:pharmacology; D015533:Transcriptional Activation; D014443:Tyrosine / Q000378:metabolism
D017871:Calcium-Calmodulin-Dependent Protein Kinases; D065128:Endothelin Receptor Antagonists; D016232:Endothelins; D066246:ErbB Receptors; D019204:GTP-Binding Proteins; D008070:Lipopolysaccharides; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D010456:Peptides, Cyclic; D016760:Proto-Oncogene Proteins c-fos; D018719:Erb-b2 Receptor Tyrosine Kinases; D011994:Recombinant Proteins; D013917:Thrombin; D014443:Tyrosine; C072247:cyclo(Trp-Asp-Pro-Val-Leu)