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.
Olschewski
Andrea
A
Department of Anaesthesiology, Intensive Care Medicine, Medical University Graz, A-8029 Graz, Austria. andrea.olschewski@physiologie.med.uni-giessen.de
Li
Yingji
Y
Tang
Bi
B
Hanze
Jörg
J
Eul
Bastian
B
Bohle
Rainer M
RM
Wilhelm
Jochen
J
Morty
Rory E
RE
Brau
Michael E
ME
Weir
E Kenneth
EK
Kwapiszewska
Grazyna
G
Klepetko
Walter
W
Seeger
Werner
W
Olschewski
Horst
H
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