Involvement of Ras and Raf in the Gi-coupled acetylcholine muscarinic m2 receptor activation of mitogen-activated protein (MAP) kinase kinase and MAP kinase.
Stimulation of the acetylcholine muscarinic m2 receptor (m2R) expressed in Rat 1a fibroblasts results in the activation of the cytoplasmic mitogen-activated protein kinase (MAPK). Concomitant with carbachol stimulation of the m2R was the activation of MEK (MAPK kinase) and Raf. MEK is the dual function kinase that phosphorylates and activates MAPK. Raf is a serine/threonine kinase capable of phosphorylating and activating MEK. Carbachol stimulation of the m2R also activated Ras. Pertussis toxin treatment of Rat 1a cells inhibited the m2R-mediated activation of Ras, Raf, MEK and MAPK. In contrast, epidermal growth factor receptor-mediated activation of Ras, Raf, MEK and MAPK was pertussis toxin-insensitive. m2R activation of Ras, Raf, and MAPK was insensitive to inhibition by genistein, while the epidermal growth factor receptor-induced responses were inhibited by genistein. The findings demonstrate that both Ras and Raf can be regulated by seven-membrane-spanning receptors that selectively couple to Gi proteins.
Division of Basic Sciences, National Jewish Center for Immunology and Respiratory Medicine, Denver, Colorado 80206.
S
S
Winitz
M
M
Russell
N X
NX
Qian
A
A
Gardner
L
L
Dwyer
G L
GL
Johnson
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D002217:Carbachol / Q000494:pharmacology; D002460:Cell Line; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism*; D019833:Genistein; D006153:Guanosine Diphosphate / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007529:Isoflavones / Q000494:pharmacology; D020929:Mitogen-Activated Protein Kinase Kinases; D011494:Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf; D016283:Proto-Oncogene Proteins p21(ras) / Q000378:metabolism*; D051381:Rats; D011976:Receptors, Muscarinic / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D012601:Scopolamine / Q000378:metabolism; D014162:Transfection
D007529:Isoflavones; D011518:Proto-Oncogene Proteins; D011976:Receptors, Muscarinic; D011994:Recombinant Proteins; D006153:Guanosine Diphosphate; D004815:Epidermal Growth Factor; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D002217:Carbachol; D019833:Genistein; D012601:Scopolamine; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D019204:GTP-Binding Proteins; D016283:Proto-Oncogene Proteins p21(ras)