Abstract
The two-pore potassium channel, TRESK has been implicated in nociception and pain disorders. We have for the first time investigated TRESK function in human nociceptive neurons using induced pluripotent stem cell-based models. Nociceptors from migraine patients with the F139WfsX2 mutation show loss of functional TRESK at the membrane, with a corresponding significant increase in neuronal excitability. Furthermore, using CRISPR-Cas9 engineering to correct the F139WfsX2 mutation, we show a reversal of the heightened neuronal excitability, linking the phenotype to the mutation. In contrast we find no change in excitability in induced pluripotent stem cell derived nociceptors with the C110R mutation and preserved TRESK current; thereby confirming that only the frameshift mutation is associated with loss of function and a migraine relevant cellular phenotype. We then demonstrate the importance of TRESK to pain states by showing that the TRESK activator, cloxyquin, can reduce the spontaneous firing of nociceptors in an in vitro human pain model. Using the chronic nitroglycerine rodent migraine model, we demonstrate that mice lacking TRESK develop exaggerated nitroglycerine-induced mechanical and thermal hyperalgesia, and furthermore, show that cloxyquin conversely is able to prevent sensitization. Collectively, our findings provide evidence for a role of TRESK in migraine pathogenesis and its suitability as a therapeutic target.
Highlights
The two-pore domain K+ channel (K2P) family mediate ‘leak’ potassium current, which is a major contributor to neuronal resting membrane potential and serves to counter depolarizing stimuli
We find that TRESK is expressed in human non-peptidergic nociceptive neurons differentiated from induced pluripotent stem cell (iPSC) and that the F139WfsX24 mutation leads to complete loss of TRESK current with resulting heightened neuronal excitability
The original finding of a KCNK18 frameshift mutation in a migraine pedigree supported by genome-wide significant linkage for the region containing KCNK18, held promise that a rare variant cause of typical migraine had been identified
Summary
The two-pore domain K+ channel (K2P) family mediate ‘leak’ potassium current, which is a major contributor to neuronal resting membrane potential and serves to counter depolarizing stimuli. In the context of pathological pain, KCNK18 (TRESK) mRNA is downregulated following nerve injury and delivery of exogenous TRESK ameliorates pain hypersensitivity following nerve injury, consistent with a crucial role in neuropathic pain development/maintenance (Tulleuda et al, 2011; Zhou et al, 2013). This has prompted several drug discovery efforts, with TRESK activators seen as a promising strategy for analgesic drug development (Wright et al, 2013; Bruner et al, 2014). A confound of pursuing drug discovery based on these studies is that human and mouse TRESK demonstrate significant differences, including low sequence homology and differing pH sensitivity (Keshavaprasad et al, 2005)
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