Impact of TASK-1 in human pulmonary artery smooth muscle cells.
The excitability of pulmonary artery smooth muscle cells (PASMC) is regulated by potassium (K+) conductances. Although studies suggest that background K+ currents carried by 2-pore domain K+ channels are important regulators of resting membrane potential in PASMC, their role in human PASMC is unknown. Our study tested the hypothesis that TASK-1 leak K+ channels contribute to the K+ current and resting membrane potential in human PASMC. We used the whole-cell patch-clamp technique and TASK-1 small interfering RNA (siRNA). Noninactivating K+ current performed by TASK-1 K+ channels were identified by current characteristics and inhibition by anandamide and acidosis (pH 6.3), each resulting in significant membrane depolarization. Moreover, we showed that TASK-1 is blocked by moderate hypoxia and activated by treprostinil at clinically relevant concentrations. This is mediated via protein kinase A (PKA)-dependent phosphorylation of TASK-1. To further confirm the role of TASK-1 channels in regulation of resting membrane potential, we knocked down TASK-1 expression using TASK-1 siRNA. The knockdown of TASK-1 was reflected by a significant depolarization of resting membrane potential. Treatment of human PASMC with TASK-1 siRNA resulted in loss of sensitivity to anandamide, acidosis, alkalosis, hypoxia, and treprostinil. These results suggest that (1) TASK-1 is expressed in human PASMC; (2) TASK-1 is hypoxia-sensitive and controls the resting membrane potential, thus implicating an important role for TASK-1 K+ channels in the regulation of pulmonary vascular tone; and (3) treprostinil activates TASK-1 at clinically relevant concentrations via PKA, which might represent an important mechanism underlying the vasorelaxing properties of prostanoids and their beneficial effect in vivo.
Department of Anaesthesiology, Intensive Care Medicine, Medical University Graz, A-8029 Graz, Austria. andrea.olschewski@physiologie.med.uni-giessen.de
Andrea
A
Olschewski
Yingji
Y
Li
Bi
B
Tang
Jörg
J
Hanze
Bastian
B
Eul
Rainer M
RM
Bohle
Jochen
J
Wilhelm
Rory E
RE
Morty
Michael E
ME
Brau
E Kenneth
EK
Weir
Grazyna
G
Kwapiszewska
Walter
W
Klepetko
Werner
W
Seeger
Horst
H
Olschewski
D002478:Cells, Cultured; D017931:DNA Primers; D005786:Gene Expression Regulation; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000502:physiology*; D009419:Nerve Tissue Proteins; D018408:Patch-Clamp Techniques; D011188:Potassium / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics / Q000502:physiology*; D011651:Pulmonary Artery / Q000166:cytology / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics
D017931:DNA Primers; D009419:Nerve Tissue Proteins; D015221:Potassium Channels; D024683:Potassium Channels, Tandem Pore Domain; D012333:RNA, Messenger; C420132:potassium channel subfamily K member 3; D011188:Potassium