Epidermal growth factor receptor transactivation mediates substance P-induced mitogenic responses in U-373 MG cells.
Ligand-induced activation of G protein-coupled receptors is emerging as an important pathway leading to the activation of certain receptors with intrinsic tyrosine kinase activity, such as the epidermal growth factor receptor (EGFR). Substance P (SP) exerts many effects via activation of its G protein-coupled receptor (neurokinin-1, NK-1). SP participates in acute inflammation and activates key proteins involved in mitogenic pathways, such mitogen-activated protein kinases (MAPKs), stimulating DNA synthesis. We tested the hypothesis that SP-induced MAPK activation and DNA synthesis require activation of the EGFR. In U-373 MG cells, which express functional NK-1, SP induced tyrosine phosphorylation of several proteins including EGFR. SP induced formation of an activated EGFR complex containing the adapter proteins SHC and Grb2, but not c-Src. SP activated the MAPK pathway as shown by increased Erk2 kinase activity. SP induced Erk2 activation, and DNA synthesis was inhibited in cells transfected with a dominant negative EGFR plasmid lacking kinase activity, as well as in cells treated with a specific EGFR inhibitor. In addition, pertussis toxin, an inhibitor of Galpha(iota) protein subunits, prevented SP-induced EGFR transactivation and subsequent DNA synthesis. Our results implicate EGFR as an essential regulator in SP/NK-1-induced activation of the MAPK pathway and cell proliferation in U-373 MG cells, and these events are mediated by a pertussis toxin-sensitive Galpha protein. We suggest that this mechanism by which SP controls cell proliferation is an important pathway in tissue restoration and healing.
Castagliuolo
I
I
Gastroenterology Division, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. icastagl@ux1.unipd.it
Valenick
L
L
Liu
J
J
Pothoulakis
C
C
D002455:Cell Division; D004261:DNA Replication / Q000187:drug effects; D004789:Enzyme Activation; D066246:ErbB Receptors / Q000235:genetics*; D019204:GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008934:Mitogens / Q000378:metabolism*; D037342:Pertussis Toxin; D010766:Phosphorylation; D013373:Substance P / Q000494:pharmacology*; D015533:Transcriptional Activation; D014407:Tumor Cells, Cultured; D014443:Tyrosine / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D008934:Mitogens; D010566:Virulence Factors, Bordetella; D013373:Substance P; D014443:Tyrosine; D037342:Pertussis Toxin; D066246:ErbB Receptors; D020928:Mitogen-Activated Protein Kinases; D019204:GTP-Binding Proteins