KCNK18 c.1107del frameshift in peripheral neuropathy links TRESK dysfunction to neuropathic pain

Neuropathic pain is commonly accompanied by hyperexcitability of nociceptive neurons, which is driven by regulation of several ion channels, including two-pore domain potassium channels (K2P) that stabilize the resting membrane potential. The TWIK-Related Spinal cord potassium channel (TRESK, K2p18.1) is predominantly expressed in sensory ganglia, where it provides major background K conductance. We describe a heterozygous c.1107del frameshift mutation in KCNK18, encoding TRESK, found in a patient with painful small fiber neuropathy and dysautonomia. This C-terminal c.1107del mutant is predicted to generate an elongated C-terminal domain, with an altered protein sequence. Whole-cell patch calmp recordings showed that the c.1107del variant reduced K current density, while heterozygous-like expression resulted in intermediate currents, consistent with a haploinsufficiency mechanism. Confocal imaging revealed decreased plasma membrane expression, indicating a trafficking-dependent loss of function while oligomerization with TRESK (homomeric channels) or TREK1 remained intact. In silico analysis revealed an altered phosphorylation pattern and reduced C-terminal hydrophobicity in the mutant TRESK. Overall, these findings support c.1107del as a pathogenic KCNK18 variant causing TRESK haploinsufficiency, offering mechanistic insight into the pathophysiology of neuropathic pain.