cGMP does not activate two-pore domain K+ channels in cerebrovascular smooth muscle.
Two-pore domain K(+) (K(2P)) channels are a new channel family. The goal of this study was to determine if K(2P) channels are activated by the nitric oxide (NO)/cGMP/PKG pathway in vascular smooth muscle. Relative levels of message for K(2P) channels were assessed in rat middle cerebral arteries (MCAs) using quantitative RT-PCR, and K(+) currents were measured in freshly dispersed vascular smooth muscle cells of the MCA. The rat MCA expresses a number of K(2P) channels. Message for TREK-1 was the most abundant K(2P) channel, followed by TASK-1 and TWIK-2, which were expressed at approximately 10% of the level of TREK-1. Message for other K(2P) channels was 1% or less than that of TREK-1. A number of K(2P) channels, including TREK-1, TWIK-2, and TASK-1, have putative PKG phosphorylation sites in the intracellular domains. The NO donor sodium nitroprusside (100 muM) or the membrane permeable analog of cGMP 8-bromo-cGMP (10 muM) elicited transient increases in whole cell current of vascular smooth muscle from the rat MCA. However, after large-conductance Ca(2+)-activated K(+) channels had been blocked with 10 mM tetraethylammonium (TEA), no increase in whole cell current was observed. Since K(2P) channels are resistant to the blocking effects of TEA, we conclude that K(2P) channels in vascular smooth muscle were not activated by the NO/cGMP/PKG pathway. Although K(2P) channels are highly expressed, K(2P) currents are not activated via the NO/cGMP pathway in rat MCA smooth muscle, despite the presence of numerous putative PKG phosphorylation sites.
Cerebrovascular Research Laboratory, Department of Anesthesiology, Baylor College of Medicine, Houston, TX 77030, USA.
Eric E
EE
Lloyd
Sean P
SP
Marrelli
Robert M
RM
Bryan
D000818:Animals; D002560:Cerebrovascular Circulation / Q000502:physiology*; D006152:Cyclic GMP / Q000378:metabolism*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D008297:Male; D020768:Middle Cerebral Artery / Q000502:physiology*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009419:Nerve Tissue Proteins; D009569:Nitric Oxide / Q000378:metabolism; D010766:Phosphorylation; D024683:Potassium Channels, Tandem Pore Domain / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D051381:Rats; D020318:Rats, Long-Evans
C539081:Kcnk6 protein, rat; D009419:Nerve Tissue Proteins; D024683:Potassium Channels, Tandem Pore Domain; C103742:potassium channel protein TREK-1; C420132:potassium channel subfamily K member 3; D009569:Nitric Oxide; D017869:Cyclic GMP-Dependent Protein Kinases; D006152:Cyclic GMP