title: TASK1 (K(2P)3.1) K(+) channel inhibition by endothelin-1 is mediated through Rho kinase-dependent phosphorylation.
abstract: OBJECTIVE
  TASK1 (K(2P)3.1) two-pore-domain K(+) channels contribute substantially to the resting membrane potential in human pulmonary artery smooth muscle cells (hPASMC), modulating vascular tone and diameter. The endothelin-1 (ET-1) pathway mediates vasoconstriction and is an established target of pulmonary arterial hypertension (PAH) therapy. ET-1-mediated inhibition of TASK1 currents in hPASMC is implicated in the pathophysiology of PAH. This study was designed to elucidate molecular mechanisms underlying inhibition of TASK1 channels by ET-1.
  
  
  METHODS
  Two-electrode voltage clamp and whole-cell patch clamp electrophysiology was used to record TASK1 currents from hPASMC and Xenopus oocytes.
  
  
  RESULTS
  ET-1 inhibited TASK1-mediated I(KN) currents in hPASMC, an effect attenuated by Rho kinase inhibition with Y-27632. In Xenopus oocytes, TASK1 current reduction by ET-1 was mediated by endothelin receptors ET(A) (IC(50) = 0.08 nM) and ET(B) (IC(50) = 0.23 nM) via Rho kinase signalling. TASK1 channels contain two putative Rho kinase phosphorylation sites, Ser(336) and Ser(393) . Mutation of Ser(393) rendered TASK1 channels insensitive to ET(A) - or ET(B)-mediated current inhibition. In contrast, removal of Ser(336) selectively attenuated ET(A) -dependent TASK1 regulation without affecting the ET(B) pathway.
  
  
  CONCLUSIONS
  ET-1 regulated vascular TASK1 currents through ET(A) and ET(B) receptors mediated by downstream activation of Rho kinase and direct channel phosphorylation. The Rho kinase pathway in PASMC may provide a more specific therapeutic target in pulmonary arterial hypertension treatment.
authors.affiliation: Department of Cardiology, Medical University Hospital Heidelberg, Heidelberg, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Seyler
authors.forename: E
authors.initials: E
authors.lastname: Duthil-Straub
authors.forename: E
authors.initials: E
authors.lastname: Zitron
authors.forename: J
authors.initials: J
authors.lastname: Gierten
authors.forename: E P
authors.initials: EP
authors.lastname: Scholz
authors.forename: R H A
authors.initials: RH
authors.lastname: Fink
authors.forename: C A
authors.initials: CA
authors.lastname: Karle
authors.forename: R
authors.initials: R
authors.lastname: Becker
authors.forename: H A
authors.initials: HA
authors.lastname: Katus
authors.forename: D
authors.initials: D
authors.lastname: Thomas
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D019332:Endothelin-1 / Q000378:metabolism*; D005260:Female; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006801:Humans; D006976:Hypertension, Pulmonary / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D008564:Membrane Potentials / Q000235:genetics / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000378:metabolism / Q000502:physiology; D009154:Mutation; D032389:Myocytes, Smooth Muscle / Q000378:metabolism / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D024683:Potassium Channels, Tandem Pore Domain / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D011651:Pulmonary Artery / Q000378:metabolism / Q000502:physiology; D044022:Receptor, Endothelin A / Q000378:metabolism; D044023:Receptor, Endothelin B / Q000378:metabolism; D015398:Signal Transduction; D014661:Vasoconstriction / Q000235:genetics / Q000502:physiology; D014982:Xenopus laevis; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D019332:Endothelin-1; D009419:Nerve Tissue Proteins; D024683:Potassium Channels, Tandem Pore Domain; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; C420132:potassium channel subfamily K member 3; D054460:rho-Associated Kinases; D020558:GTP Phosphohydrolases