Angiotensin II inhibits native bTREK-1 K+ channels through a PLC-, kinase C-, and PIP2-independent pathway requiring ATP hydrolysis

Am J Physiol Cell Physiol. 2007 Aug;293(2):C682-95. doi: 10.1152/ajpcell.00087.2007. Epub 2007 May 9.

Abstract

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.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adenosine Triphosphate / analogs & derivatives
  • Adenosine Triphosphate / metabolism*
  • Adenosine Triphosphate / pharmacology
  • Angiotensin II / metabolism*
  • Angiotensin II / pharmacology
  • Animals
  • Calcium / metabolism
  • Cattle
  • Cells, Cultured
  • Enzyme Inhibitors / pharmacology
  • Hydrolysis
  • Ion Channel Gating
  • Male
  • Membrane Potentials
  • Patch-Clamp Techniques
  • Phosphatidylinositol 4,5-Diphosphate / metabolism*
  • Polyphosphates / pharmacology
  • Potassium / metabolism
  • Potassium Channel Blockers / metabolism*
  • Potassium Channel Blockers / pharmacology
  • Potassium Channels, Tandem Pore Domain / drug effects
  • Potassium Channels, Tandem Pore Domain / metabolism*
  • Protein Kinase C / antagonists & inhibitors
  • Protein Kinase C / metabolism*
  • Receptor, Angiotensin, Type 1 / metabolism
  • Signal Transduction
  • Time Factors
  • Type C Phospholipases / antagonists & inhibitors
  • Type C Phospholipases / metabolism*
  • Zona Fasciculata / cytology
  • Zona Fasciculata / drug effects
  • Zona Fasciculata / metabolism*

Substances

  • Enzyme Inhibitors
  • N(6)-2-phenylethyladenosine triphosphate
  • Phosphatidylinositol 4,5-Diphosphate
  • Polyphosphates
  • Potassium Channel Blockers
  • Potassium Channels, Tandem Pore Domain
  • Receptor, Angiotensin, Type 1
  • potassium channel protein TREK-1
  • Angiotensin II
  • Adenosine Triphosphate
  • Protein Kinase C
  • Type C Phospholipases
  • Potassium
  • Calcium