We recently revealed the mechano-gated two-pore domain potassium (K2P) channel, TREK-1, to be a major regulator of murine intestinal contractility (Ma et al, 2018). However, verification was complicated by a lack of well-defined K2P modulators and species specific pharmacology. Here, using heterologous expression in Xenopus laevis oocytes and electrophysiological analysis using two-electrode voltage clamp in standard bath solutions, we characterised the pharmacological profile of mouse homologues of TREK-1 and TREK-2 using previously documented human K2P activators; arachidonic acid (AA, 10 µM), BL-1249 (1 µM) and cinnamyl-3,4-dihydroxy-α-cyanocinnamate (CDC, 10 µM) and inhibitors; spadin (1 µM) and barium chloride (Ba2+, 1 mM). Values are stated as mean ± S.E.M. and were statistically compared by ANOVA. Mouse (m) TREK-1 and TREK-2 channel currents were significantly increased by AA, BL-1249 and CDC in a voltage-independent manner. At 0 mV, AA increased mTREK-1 currents by 2.5 ± 0.3-fold (n = 7, p = <0.05) and mTREK-2 by 1.6 ± 0.1-fold (n = 7, p <0.05), BL-1249 increased mTREK-1 currents by 2.9 ± 0.3-fold (n = 9, p = <0.05) and mTREK-2 by 1.5 ± 0.1-fold (n = 9, p = <0.05), and CDC increased mTREK-1 currents by 2.1 ± 0.1-fold (n = 8, p <0.05) and mTREK-2 by 2.3 ± 0.2-fold (n = 6, p = <0.05). Under basal conditions, both mTREK-1 and mTREK-2 currents were insensitive to application of spadin at all activating voltages. In contrast Ba2+ induced a significant, voltage-dependent reduction in outward currents of both channels. At 0 mV, mTREK-1 and mTREK-2 currents were inhibited by 56.1 ± 1.4% (n = 7, p <0.05) and 55.4 ± 2.4% (n = 7, p <0.05) respectively. Furthermore, spadin did not significantly inhibit either mTREK-1 or mTREK-2 currents following pre-activation by either AA, BL-1249 or CDC (n = 8-12, p = >0.05). However, we found pre-exposure to spadin significantly perturbed the activation of mTREK-1 currents by AA, voltage-independently. At 0 mV, activation of mTREK-1 by AA was reduced by 42.5 ± 1.8% (n = 12, p <0.05) compared to AA alone. Activation of mTREK-1 channels by either BL-1249 or CDC was not significantly attenuated by pre-exposure to spadin (n = 8-11, p = >0.05). Similarly, pre-exposure to spadin was unable to antagonise mTREK-2 channel current activation by either AA, BL-1249 or CDC (n = 6-8, p = >0.05). These data demonstrate that pharmacological activation of mouse TREK-1 and TREK-2 channels by AA, BL-1249 and CDC is comparable to that observed in their human orthologues. Additionally, our data suggests spadin is not a pore blocker of mTREK-1 or mTREK-2 channels, like Ba2+, but specifically antagonises the activation of mTREK-1 channels by AA, and not other pharmacological activators. Further studies are required to reveal the precise molecular mechanisms of spadin antagonism.
Europhysiology 2018 (London, UK) (2018) Proc Physiol Soc 41, C031
Oral Communications: Spadin selectively antagonises arachidonic acid activation of mTREK-1 channels
R. Ma1, A. Lewis1
1. School of Pharmacy and Biomedical Science, University of Portsmouth, Portsmouth, United Kingdom.
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Where applicable, experiments conform with Society ethical requirements.