Effects of extracellular Ca2+ influx on endothelin-1-induced intracellular mitogenic cascades in C6 glioma cells.
We have recently shown that endothelin-1 activates two types of Ca2+-permeable nonselective cation channels (NSCC-1 and NSCC-2) in C6 glioma cells. These channels can be distinguished by their sensitivity to blockers of the receptor-operated Ca2+ channel, 1-[b-(3-[4-methoxyphenyl]propoxy)-4-methoxyphenethyl]-1H-imidazole hydrochloride (SK&F 96365) and (R,S)-(3,4-dihydro-6,7-dimethoxy-isoquinoline-1-yl)-2-phenyl-N,N-di-[2-(2,3,4-trimethoxyphenyl)ethyl]-acetamide (LOE 908). NSCC-1 is sensitive to LOE 908 and resistant to SK&F 96365, whereas NSCC-2 is sensitive to both LOE 908 and SK&F 96365. Moreover, extracellular Ca2+ influx through these channels plays an essential role in endothelin-1-induced mitogenesis in C6 glioma cells. The purpose of the present study was to investigate the effects of extracellular Ca2+ influx on intracellular pathways of endothelin-1-induced mitogenic responses in C6 glioma cells. We focused on extracellular signal-regulated kinase 1 and 2 (ERK1/2) in this context. An inhibitor of mitogen-activated protein kinase, 2-[2-amino-3-methoxyphenyl]-4H-1-benzopyran-4-one (PD 98059), abolished the endothelin-1-induced increase in ERK1/2 activity, but only partially suppressed the mitogenic response. ERK1/2 activation by endothelin-1 was partially suppressed in the absence of extracellular Ca2+. On the basis of the sensitivity to LOE 908 and SK&F 96365, Ca2+ influx through NSCC-1 and NSCC-2 plays an essential role in the extracellular Ca2+-dependent component of ERK1/2 activity. In contrast, Ca2+ influx through NSCC-2 is involved in the ERK1/2-independent component of endothelin-1-induced mitogenesis. These results indicate that (1) the endothelin-1-induced mitogenic response involves both ERK1/2-dependent and -independent mechanisms, (2) ERK1/2 activation by endothelin-1 involves an extracellular Ca2+ influx-dependent cascade as well as an extracellular Ca2+ influx-independent cascade, (3) because endothelin-1-induced mitogenesis is completely dependent on extracellular Ca2+ influx, extracellular Ca2+ influx also plays an important role in mitogenic pathways downstream of ERK1/2, (4) extracellular Ca2+ influx through NSCC-1 and NSCC-2 has an important role in the extracellular Ca2+ influx-dependent component of ERK1/2-dependent mitogenesis, (5) extracellular Ca2+ influx through NSCC-2 has an important role in ERK1/2-independent mitogenesis, and (6) Ca2+ influx through each Ca2+ channel may play a distinct role in intracellular mitogenic cascades.
Kawanabe
Yoshifumi
Y
Department of Neurosurgery, Kyoto University Faculty of Medicine, Kyoto 606-8397, Sakyo, Japan. kawanabe@kuhp.kyoto-u.ac.jp
Hashimoto
Nobuo
N
Masaki
Tomoh
T
D000081:Acetamides / Q000494:pharmacology; D000818:Animals; D001932:Brain Neoplasms / Q000473:pathology; D002118:Calcium / Q000494:pharmacology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D015220:Calcium Channels / Q000378:metabolism*; D004247:DNA / Q000096:biosynthesis / Q000187:drug effects; D004347:Drug Interactions; D019332:Endothelin-1 / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D005910:Glioma / Q000473:pathology; D007093:Imidazoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008934:Mitogens / Q000494:pharmacology; D051381:Rats; D013936:Thymidine / Q000378:metabolism; D014316:Tritium; D014407:Tumor Cells, Cultured
D000081:Acetamides; D002121:Calcium Channel Blockers; D015220:Calcium Channels; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D007546:Isoquinolines; D008934:Mitogens; D014316:Tritium; C081356:LOE 908; D004247:DNA; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D002118:Calcium; D013936:Thymidine