GI‐530159, a novel, selective, mechanosensitive two‐pore‐domain potassium (K_2P) channel opener, reduces rat dorsal root ganglion neuron excitability

Abstract

Background and PurposeTREK two‐pore‐domain potassium (K2P) channels play a critical role in regulating the excitability of somatosensory nociceptive neurons and are important mediators of pain perception. An understanding of the roles of TREK channels in pain perception and, indeed, in other pathophysiological conditions, has been severely hampered by the lack of potent and/or selective activators and inhibitors. In this study, we describe a new, selective opener of TREK channels, GI‐530159.Experimental ApproachThe effect of GI‐530159 on TREK channels was demonstrated using 86Rb efflux assays, whole‐cell and single‐channel patch‐clamp recordings from recombinant TREK channels. The expression of K2P2.1 (TREK1), K2P10.1 (TREK2) and K2P4.1 (TRAAK) channels was determined using transcriptome analysis from single dorsal root ganglion (DRG) cells. Current‐clamp recordings from cultured rat DRG neurons were used to measure the effect of GI‐530159 on neuronal excitability.Key ResultsFor recombinant human TREK1 channels, GI‐530159 had similar low EC50 values in Rb efflux experiments and electrophysiological recordings. It activated TREK2 channels, but it had no detectable action on TRAAK channels nor any significant effect on other K channels tested. Current‐clamp recordings from cultured rat DRG neurones showed that application of GI‐530159 at 1 μM resulted in a significant reduction in firing frequency and a small hyperpolarization of resting membrane potential.Conclusions and ImplicationsThis study provides pharmacological evidence for the presence of mechanosensitive TREK K2P channels in sensory neurones and suggests that development of selective K2P channel openers like GI‐530159 could aid in the development of novel analgesic agents.Linked ArticlesThis article is part of a themed section on Recent Advances in Targeting Ion Channels to Treat Chronic Pain. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.12/issuetoc

KCC2 regulates neuronal excitability and hippocampal activity via interaction with Task-3 channels

“…Since both dentate spikes 78 and sharp-wave ripples 79 have been associated with memory consolidation in hippocampal-dependent learning, we predict KCC2 suppression in the pathology may impact cognitive performances through a combination of GABA-dependent and -independent mechanisms. Our results suggest therapeutic strategies aiming to either restore neuronal chloride homeostasis by blocking NKCC1 function 57 and neuronal excitability by targeting leak potassium channels 80 , or to stabilize KCC2 membrane expression 25,32 may best compensate for altered network activity and associated behavioral or cognitive deficits.…”

Molecular determinants of chemical modulation of two‐pore domain potassium channels

“…), which should be investigated further, especially as BL‐1249 activates TRAAK only at high concentrations (Pope et al., ). Interestingly to note, activation resulted more readily by extracellular application of both ML67‐33 and BL‐1249 (Bagriantsev et al., ), a particular aspect that was also observed in testing GI‐530139, which activates TREK‐1 and TREK‐2 but not TRAAK (Loucif et al., ) and caffeic acid derivatives as TREK‐1 activators (Danthi, Enyeart, & Enyeart, ). Whether this hints at binding at different, still to be discovered, positions near the SF, remains to be deciphered.…”

Recent advances in targeting ion channels to treat chronic pain

“…Such model systems, theoretically, allow ion channel pharmacology and/or biophysics to be examined in isolation. These efforts are supported by developments in automated patch clamp technology, predominantly using expression systems, to measure ion channel activity (Bell and Dallas, ; Loucif et al ., ).…”

“…However, there has been recent progress in MEA recordings from DRGs, including from those derived from human embryonic stem cells (Alshawaf et al ., ), which could provide important phenotypic screening platforms as a basis for identifying novel analgesics. It is often useful to support native neuronal studies with work in expression systems such as transiently transfected or stably expressed mammalian cells (Loucif et al ., ; McArthur et al ., ) or oocyte expression (Lee et al ., ; Mourot et al ., ). Such model systems, theoretically, allow ion channel pharmacology and/or biophysics to be examined in isolation.…”