Modulation of K_2P2.1 and K_2P10.1 K⁺ channel sensitivity to carvedilol by alternative mRNA translation initiation

Abstract

BACKGROUND AND PURPOSEThe β-receptor antagonist carvedilol blocks a range of ion channels. K2P2.1 (TREK1) and K2P10.1 (TREK2) channels are expressed in the heart and regulated by alternative translation initiation (ATI) of their mRNA, producing functionally distinct channel variants. The first objective was to investigate acute effects of carvedilol on human K2P2.1 and K2P10.1 channels. Second, we sought to study ATI-dependent modulation of K2P K + current sensitivity to carvedilol. EXPERIMENTAL APPROACHUsing standard electrophysiological techniques, we recorded currents from wild-type and mutant K2P2.1 and K2P10.1 channels in Xenopus oocytes and HEK 293 cells. KEY RESULTSCarvedilol concentration-dependently inhibited K2P2.1 channels (IC50,oocytes = 20.3 μM; IC50,HEK = 1.6 μM) and this inhibition was frequency-independent. When K2P2.1 isoforms generated by ATI were studied separately in oocytes, the IC50 value for carvedilol inhibition of full-length channels (16.5 μM) was almost 5-fold less than that for the truncated channel variant (IC50 = 79.0 μM). Similarly, the related K2P10.1 channels were blocked by carvedilol (IC50,oocytes = 24.0 μM; IC50,HEK = 7.6 μM) and subject to ATI-dependent modulation of drug sensitivity.

N-Glycosylation of TREK-1/hK2P2.1 Two-Pore-Domain Potassium (K2P) Channels

“…To evaluate the effects of N -linked carbohydrate modification on the functional properties of hTREK-1 channels, Xenopus laevis oocytes heterologously expressing wild-type (WT) channel subunits were subjected to two-electrode voltage clamp (TEVC) measurements 24 and 48 h after injection. Due to the previous observation that the yolk sac of Xenopus laevis oocytes can sequester lipophilic compounds [19] two different routes of tunicamycin administration were chosen. Oocytes were either maintained in medium containing tunicamycin (incubated with 0.75 mg/L or 1.5 mg/L directly after RNA injection until TEVC measurements were performed) or coinjected with hTREK-1 RNA and 2 ng or 3 ng of tunicamycin per oocyte, respectively.…”

“…Furthermore, dysregulation of cardiac TREK-1 expression has been observed in patients suffering from atrial fibrillation and heart failure [14,15]. Even though the pharmacological [16,17,18,19,20,21,22] and biophysical [23,24,25,26,27,28] characteristics of hTREK-1 channels have been widely studied, relatively little is known about its posttranslational modifications [29].…”

Translating Translation to Mechanisms of Cardiac Hypertrophy

“…Potassium channel genes TREK-1 (K 2P 2.1) and TREK-2 (K 2P 10.1), which are expressed in cardiac tissue, undergo alternative translation yielding n-terminally truncated protein isoforms [118,119]. Interestingly, these shorter K 2P alternative translation products result in functional changes in conductance and display altered drug sensitivity [120,121]. Calcium channel subunits generated from the ORAI transcript are also generated through alternative translation [122,123].…”

Pharmacogenetic diversification by alternative translation initiation: background channels to the fore: Commentary on Kisselbach et al., Br J Pharmacol 171: 5182–5194

“…This brings us back to the findings of Kisselbach et al . (). Previous research led to the observations that ATI influences K 2P ion selectivity (Thomas et al ., ) and block by the antidepressant, fluoxetine (Eckert et al ., ).…”

“…() are a case in point. Building on previous pioneering work demonstrating that neuronal K 2P 2.1 potassium‐selective ‘background’ channels (for nomenclature, see Alexander et al ., ) can become permeable to sodium ions depending on alternative translation initiation (ATI) (Thomas et al ., ), the Thomas laboratory now shows that the ATI of K 2P 2.1 and K 2P 10.1, which are also expressed in the heart, can cause a fivefold shift in sensitivity to block by the β‐adrenoceptor (and potassium channel) antagonist, carvedilol (Kisselbach et al ., ).…”