Endothelin-stimulated ERK activation in airway smooth-muscle cells requires calcium influx and Raf activation.
Endothelin (ET)-1 is a 21-amino-acid peptide that is a potent vasoconstrictor and mitogen. By binding to its G-protein coupled receptor, ET-1 stimulates the proliferation of airway smooth-muscle (ASM) cells, which may be involved in the pathogenesis of asthma. The ETB receptor stimulates activation of the extracellular regulated kinase 2 (ERK2), which is thought to be required for proliferation of ASM cells. Our findings reveal that ET rapidly activates Raf, and that dominant-negative Raf interferes with ET-induced ERK activation in ASM cells. Expression of the amino-terminal Ras-binding domain of Raf inhibited ET-induced ERK activation, suggesting that ET-stimulated Raf activation is a Ras-dependent process. Furthermore, ET-stimulated ERK and Raf activation in ASM cells require calcium influx; chelating extracellular calcium or preventing calcium influx through calcium channels inhibited ET-stimulated, but not phorbol ester-stimulated, ERK and Raf activation.
Vichi
P
P
Department of Molecular Physiology, College of Medicine, University of Vermont, Burlington, USA.
Whelchel
A
A
Knot
H
H
Nelson
M
M
Kolch
W
W
Posada
J
J
D000818:Animals; D019556:COS Cells; D002118:Calcium / Q000378:metabolism*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D019332:Endothelin-1 / Q000494:pharmacology*; D004789:Enzyme Activation; D019950:Mitogen-Activated Protein Kinase 1; D009130:Muscle, Smooth / Q000201:enzymology*; D019908:Proto-Oncogene Proteins c-raf / Q000235:genetics / Q000502:physiology*; D051381:Rats; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000235:genetics; D012137:Respiratory System / Q000201:enzymology*; D015398:Signal Transduction; D014162:Transfection
D019332:Endothelin-1; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D019908:Proto-Oncogene Proteins c-raf; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D002118:Calcium