Angiotensin II inhibits native bTREK-1 K+ channels through a PLC-, kinase C-, and PIP2-independent pathway requiring ATP hydrolysis.
Angiotensin II (ANG II) inhibits bTREK-1 (bovine KCNK2) K(+) channels in bovine adrenocortical cells through a Gq-coupled AT(1) receptor by activation of separate Ca(2+)- and ATP hydrolysis-dependent signaling pathways. Whole cell patch-clamp recording from bovine adrenal zona fasciculata (AZF) cells was used to characterize the ATP-dependent signaling mechanism for inhibition of bTREK-1 by ANG II. We discovered that ATP-dependent inhibition of bTREK-1 by ANG II occurred through a novel mechanism that was independent of PLC and its established downstream effectors. The ATP-dependent inhibition of bTREK-1 by ANG II was not reduced by the PLC antagonists edelfosine and U73122, or by the PKC antagonists bisindolylmaleimide I (BIM) or calphostin C. bTREK-1 was partially inhibited ( approximately 25%) by the PKC activator phorbol 12,13 dibutyrate (PDBu) through an ATP-dependent mechanism that was blocked by BIM. Addition of Phosphatidylinositol(4,5) bisphosphate diC8 [DiC(8)PI(4,5)P(2)], a water-soluble derivative of phosphotidyl inositol 4,5 bisphosphate (PIP(2)) to the pipette solution failed to alter inhibition by ANG II. bTREK-1 inhibition by ANG II was also insensitive to antagonists of other protein kinases activated by ANG II in adrenocortical cells but was completely blocked by inorganic polytriphosphate PPPi. DiC(8)PI(4,5)P(2) was a weak activator of bTREK-1 channels, compared with the high-affinity ATP analog N(6)-(2-phenylethyl)adenosine-5'-O-triphosphate (6-PhEt-ATP). These results demonstrate that the modulation of bTREK-1 channels in bovine AZF cells is distinctive with respect to activation by phosphoinositides and nucleotides and inhibition by Gq-coupled receptors. Importantly, ANG II inhibits bTREK-1 channels through a novel pathway that is different from that described for inhibition of native TREK-1 channels in neurons, or cloned channels expressed in cell lines. They also indicate that, under physiological conditions, ANG II inhibits bTREK-1 and depolarizes AZF cells by two, novel, independent pathways that diverge proximal to the activation of PLC.
Liu
Haiyan
H
Dept of Neuroscience, The Ohio State University, College of Medicine and Public Health, 5196 Graves Hall, Columbus, OH 43210-1239, USA.
Enyeart
Judith A
JA
Enyeart
John J
JJ
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D000804:Angiotensin II / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006868:Hydrolysis; D015640:Ion Channel Gating; D008297:Male; D008564:Membrane Potentials; D018408:Patch-Clamp Techniques; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism*; D011122:Polyphosphates / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000378:metabolism* / Q000494:pharmacology; D024683:Potassium Channels, Tandem Pore Domain / Q000187:drug effects / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D044140:Receptor, Angiotensin, Type 1 / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015383:Zona Fasciculata / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D004791:Enzyme Inhibitors; C459592:N(6)-2-phenylethyladenosine triphosphate; D019269:Phosphatidylinositol 4,5-Diphosphate; D011122:Polyphosphates; D026902:Potassium Channel Blockers; D024683:Potassium Channels, Tandem Pore Domain; D044140:Receptor, Angiotensin, Type 1; C103742:potassium channel protein TREK-1; D000804:Angiotensin II; D000255:Adenosine Triphosphate; D011493:Protein Kinase C; D010738:Type C Phospholipases; D011188:Potassium; D002118:Calcium