Stromatoxin‐sensitive, heteromultimeric Kv2.1/Kv9.3 channels contribute to myogenic control of cerebral arterial diameter

Abstract

Cerebral vascular smooth muscle contractility plays a crucial role in controlling arterial diameter and, thereby, blood flow regulation in the brain. A number of K + channels have been suggested to contribute to the regulation of diameter by controlling smooth muscle membrane potential (E m ) and Ca 2+ influx. Previous studies indicate that stromatoxin (ScTx1)-sensitive, Kv2-containing channels contribute to the control of cerebral arterial diameter at 80 mmHg, but their precise role and molecular composition were not determined. Here, we tested if Kv2 subunits associate with 'silent' subunits from the Kv5, Kv6, Kv8 or Kv9 subfamilies to form heterotetrameric channels that contribute to control of diameter of rat middle cerebral arteries (RMCAs) over a range of intraluminal pressure from 10 to 100 mmHg. The predominant mRNAs expressed by RMCAs encode Kv2.1 and Kv9.3 subunits. Co-localization of Kv2.1 and Kv9.3 proteins at the plasma membrane of dissociated single RMCA myocytes was detected by proximity ligation assay. ScTx1-sensitive native current of RMCA myocytes and Kv2.1/Kv9.3 currents exhibited functional identity based on the similarity of their deactivation kinetics and voltage dependence of activation that were distinct from those of homomultimeric Kv2.1 channels. ScTx1 treatment enhanced the myogenic response of pressurized RMCAs between 40 and 100 mmHg, but this toxin also caused constriction between 10 and 40 mmHg that was not previously observed following inhibition of large conductance Ca 2+ -activated K + (BK Ca ) and Kv1 channels. Taken together, this study defines the molecular basis of Kv2-containing channels and contributes to our understanding of the functional significance of their expression in cerebral vasculature. Specifically, our findings provide the first evidence of heteromultimeric Kv2.1/Kv9.3 channel expression in RMCA myocytes and their distinct contribution to control of cerebral arterial diameter over a wider range of E m and transmural pressure than Kv1 or BK Ca channels owing to their negative range of voltage-dependent activation.

Contribution of K v 7 Channels to Basal Coronary Flow and Active Response to Ischemia

“…4,6,7,11,14,15 Moreover, evidence is accumulating that activation of K V 7 channels contributes to the vasodilatory response of various endogenous molecules, including β-adrenoceptor agonists 3 and H 2 S. 16 In addition, mesenteric and renal arteries from hypertensive animals exhibit considerable attenuated response to K V 7 activators and marked reduction in K V 7.4 abundance. 6,14 The present study now reveals that coronary arteries express KCNQ1, 4, and 5 transcripts, as well as all members of the KCNE gene family except KCNE1.…”

“…K V 7 channels are important regulators of vascular tone in several arteries, including mesenteric, renal, and cerebral arteries 6,11 where K V 7 blockers promote vasospasm, and K V 7 activators are effective vasorelaxants. 4,6,7,11,14,15 Moreover, evidence is accumulating that activation of K V 7 channels contributes to the vasodilatory response of various endogenous molecules, including β-adrenoceptor agonists 3 and H 2 S. 16 In addition, mesenteric and renal arteries from hypertensive animals exhibit considerable attenuated response to K V 7 activators and marked reduction in K V 7.4 abundance.…”

“…Voltage-gated potassium channels (K V ) have been implicated in the control of the coronary circulation and reactive hyperemia, 1,2 but little is known about the specific molecular components. Kv channels encoded by KCNQ1-5 (K V 7.1-K V 7.5) are important regulators of the smooth muscle resting membrane potential and contractility in several different rodent and human arteries, [3][4][5][6][7][8][9][10][11] which are known to be compromised in animal models of primary and secondary hypertension. 3,6 These channels, in particular K V 7.4, are also functional end points in β-adrenoceptor-mediated relaxations.…”

Contribution of Kv7.4/Kv7.5 Heteromers to Intrinsic and Calcitonin Gene-Related Peptide–Induced Cerebral Reactivity

“…Our PLA studies allowed us to investigate the structural features of Kv7 channels in the MCA similar to previous studies on Kv2.1 and Kv9.3 association in the same artery. 26 With this technique, hybridization of the PLA probes occurs when proteins are <40 nm apart. 27 Because combinations of Kv7.5 antibodies resulted in considerably less PLA signal, the most parsimonious conclusion is that the number of channels containing ≥2 Kv7.5 proteins is low.…”

“…Of course, there are caveats to our findings. We have no insight into how Kv7 channels interplay with Kv1 and Kv2 channels that are also known to shape the myogenic response in these arteries, 16,26,[31][32][33] and there is always the possibility for off-target effects although these have been largely controlled for with different experimental protocols. The present study has advanced our understanding on the impact of Kv7 channels in the regulation of MCA diameter and the contribution of different isoforms to cerebral perfusion.…”