Genetic and functional validation of two pore domain potassium channels as analgesic targets

Drug discovery programmes for pain suffer from poor clinical translation, despite many drugs gaining in-vivo efficacy. Subsequently, patient populations are poorly served by existing, often ineffective, and sometimes harmful, analgesics. One way to address poor clinical translation and ameliorate clinical trial failure rates, is to use human genetic data to validate molecular targets in a translational context, whilst stratifying patient groups using genetic variants. Ion channels highly expressed along nociceptive pathways are rapidly emerging as important molecular components in the mechanisms of pain, of which the two-pore domain potassium (K2P) family are one group of unexploited therapeutic targets with good in-vitro/vivo pre-clinical validation and existing genetic linkage in small scale studies. To understand the role of K2Ps in pain within large scale populations, a functional genomic target validation approach was applied using genome-wide association study (GWAS) results. The association of >135,0000 K2P gene loci variants with pain subtypes was investigated in the UK and Finnish Biobanks, and in-silico characterisation undertaken to predict their epidemiological and molecular penetrance, in stratified populations. Select variants were characterised using patch clamp electrophysiology, thallium flux, RT-qPCR, and live-cell imaging to support cellular phenotype prediction in patients. Altogether, 18 variants were strongly associated with distinct pain subtypes within the gene-loci for KCNK18, KCNK5/16/17, KCNK13, KCNK10, KCNK7, KCNK3 and KCNK1, amongst many suggestive signals of weaker effect. These results benchmarked particularly well against, and in some cases surpassed the genetic association data of other reputed ion channel pain-associated gene targets (TRP and SCNA). An investigation into the pleiotropic effect of these K2P variants in patients with pain who also dose regularly with analgesic medications, identified even stronger links, suggesting complex trait genetics for these variants. Functional characterisation of select KCNK10 variants in translated and untranslated regions of the gene, demonstrated altered functional activity with the potential to modify pain-sensing thresholds in patients by affecting the regulation of the membrane potential in nociceptive neurones or by other mechanistic routes in alternative cell types. The validation of both molecular and clinical data from large patient groups, has shown that pain-association and susceptibility markers exist within select K2P gene loci, some of which cause alterations in ion channel activity, in-vitro. These data combined, suggest an important role for K2P ion channels in pain and represent promising novel analgesic targets that could ameliorate complex pain conditions.