Arginine vasopressin inhibits Kir6.1/SUR2B channel and constricts the mesenteric artery via V1a receptor and protein kinase C

Abstract

Kir6.1/SUR2B channel is the major isoform of K(ATP) channels in the vascular smooth muscle. Genetic disruption of either subunit leads to dysregulation of vascular tone and regional blood flows. To test the hypothesis that the Kir6.1/SUR2B channel is a target molecule of arginine vasopressin (AVP), we performed studies on the cloned Kir6.1/SUR2B channel and cell-endogenous K(ATP) channel in rat mesenteric arteries. The Kir6.1/SUR2B channel was expressed together with V1a receptor in the HEK-293 cell line. Whole cell currents of the transfected HEK cells were activated by K(ATP) channel opener pinacidil and inhibited by K(ATP) channel inhibitor glibenclamide. AVP produced a concentration-dependent inhibition of the pinacidil-activated currents with IC(50) 2.0 nM. The current inhibition was mediated by a suppression of the open-state probability without effect on single-channel conductance. An exposure to 100 nM PMA, a potent PKC activator, inhibited the pinacidil-activated currents, and abolished the channel inhibition by AVP. Such an effect was not seen with inactive phorbol ester. A pretreatment of the cells with selective PKC blocker significantly diminished the inhibitory effect of AVP. In acutely dissociated vascular smooth myocytes, AVP strongly inhibited the cell-endogenous K(ATP) channel. In isolated mesenteric artery rings, AVP produced concentration-dependent vasoconstrictions with EC(50) 6.5 nM. At the maximum effect, pinacidil completely relaxed vasoconstriction in the continuing exposure to AVP. The magnitude of the AVP-induced vasoconstriction was significantly reduced by calphostin-C. These results therefore indicate that the Kir6.1/SUR2B channel is a target molecule of AVP, and the channel inhibition involves G(q)-coupled V1a receptor and PKC.

Protein Kinase C-ε Induces Caveolin-Dependent Internalization of Vascular Adenosine 5′-Triphosphate–Sensitive K + Channels

“…4 Thus, it is expected that K ATP channel inhibition contributes to the effects of vasoconstrictors in reducing blood flow. 15,45 Our observations reveal an important novel mechanism allowing K ATP channels to be downregulated by PKC-mediated and caveolin-dependent internalization. This mechanism may play a critical role in regulating K ATP channels and, thus, vascular function.…”

“…15,37 However, the mechanism by which PKC inhibits K ATP channels is unknown. Both PKC-and Kir6.1 are localized in the caveolae of arterial smooth muscles, 16,17 which are specialized microdomains in the plasma membrane and serve to compartmentalize and integrate numerous signaling events.…”

“…15 Primary dermal arteriolar VSMCs were cultured from punch biopsies as reported previously. 24,25 These cells were maintained in the same medium as that for HEK293 cells and cultured in serum-free medium for 12 to 24 hours before experiments.…”

“…13 Several vasoconstrictors have also been shown to inhibit K ATP channels via activation of PKC. 14,15 Recent studies have revealed that Kir6.1 is mainly localized in the caveolae of aortic smooth muscle cells. 16 Angiotensin II, a potent physiological vasoconstrictor, was reported to recruit a novel PKC isoform, PKC-, to arterial smooth muscle caveolae, indicating a potential role for caveolae in the regulation of K ATP channel function.…”

S-Glutathionylation of Ion Channels: Insights into the Regulation of Channel Functions, Thiol Modification Crosstalk, and Mechanosensing

“…Post-translational modifications (PTMs) are important mechanisms regulating ion channel functions. One of the classical PTM is protein phosphorylation, and a large number of ion channels are found to be regulated by phosphorylation through PKA, PKC, and other protein kinases (30,57,109,112,113,139). A variety of different types of PTMs (e.g., Ubiquitylation, SUMOylation, O-glycosylation/ O-GlcNAcylation, etc.)…”