Molecular mechanisms for the activation of Ca2+-permeable nonselective cation channels by endothelin-1 in C6 glioma cells.
We recently demonstrated that endothelin-1 (ET-1) activates two types of Ca(2+)-permeable nonselective cation channels (NSCC-1 and NSCC-2) in C6 glioma cells. It is possible to discriminate between these channels by using the Ca(2+) channel blockers SK&F 96365 (1-[beta-(3-[4-methoxyphenyl]propoxy)-4-methoxyphenethyl]-1H-imidazole hydrochloride) and LOE 908 [(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 is a blocker for NSCC-1 and NSCC-2, whereas SK&F 96365 is an inhibitor for NSCC-2. The purpose of the present study was to identify the G-proteins that are involved in ET-1-activated Ca(2+) channels in C6 glioma cells. ET-1 activated only NSCC-1 in C6 glioma cells preincubated with U73122 (1-[6-[((17beta)-3-methoxyestra-1,3,5[10]-trien-17-yl)amino]hexyl]-1H-pyrrole-2,5-dione), a phospholipase C (PLC) inhibitor. Microinjection of the dominant negative mutant of G(12)/G(13) (G(12)G228A/G(13)G225A) abolished activation of NSCC-1 and NSCC-2. In contrast, pertussis toxin did not affect any of the Ca(2+) channels in the ET-1-stimulated C6 glioma cells. These results indicate that G(12)/G(13) may couple with endothelin receptors and play an important role in the activation of NSCCs in C6 glioma cells. Moreover, the activation mechanisms of NSCC-1 and NSCC-2 by ET-1 were different. NSCC-1 activation depended upon a G(12)/G(13)-dependent cascade, whereas NSCC-2 activation depended upon both G(q)/PLC- and G(12)/G(13)-dependent cascades.
Department of Neurosurgery, Kyoto University Graduate School of Medicine, 606-8507, Kyoto, Japan. ykawanabe@rics.bwh.harvard.edu
Yoshifumi
Y
Kawanabe
Nobuo
N
Hashimoto
Tomoh
T
Masaki
D000081:Acetamides / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D027682:Cation Transport Proteins / Q000378:metabolism*; D019332:Endothelin-1 / Q000494:pharmacology*; D004963:Estrenes / Q000494:pharmacology; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D019204:GTP-Binding Proteins / Q000502:physiology*; D005910:Glioma / Q000473:pathology; D020962:Heterotrimeric GTP-Binding Proteins / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology; D007546:Isoquinolines / Q000494:pharmacology; D037342:Pertussis Toxin / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D014407:Tumor Cells, Cultured
D000081:Acetamides; D015220:Calcium Channels; D027682:Cation Transport Proteins; D019332:Endothelin-1; D004963:Estrenes; D007093:Imidazoles; D007546:Isoquinolines; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; C081356:LOE 908; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020962:Heterotrimeric GTP-Binding Proteins; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium