Inward rectifier potassium channel 18 (KCNJ18 (Kir2.6))

Inward rectifier potassium channel 18 (KCNJ18, Kir2.6) is an ion channel primarily expressed in human skeletal muscle, encoded by the KCNJ18 gene[5][6][3]. It forms part of the Kir2.x subfamily of inwardly rectifying potassium channels, which selectively enhance potassium influx over efflux, thus stabilizing the negative resting membrane potential of muscle cells[4][6]. The channel's function and expression are critically regulated by thyroid hormone, and genetic mutations in KCNJ18 predispose susceptible individuals to thyrotoxic periodic paralysis (TPP), a condition in which sudden episodes of flaccid muscle weakness arise in the context of hyperthyroidism and hypokalemia[5][6][7]. Like other inward rectifier potassium channels, KCNJ18 assembles as a tetramer, with each subunit containing two transmembrane domains and a pore-forming loop[6][7]. Disease-causing mutations typically lead to functional deficits in channel activity, reduced membrane localization, and increased risk of abnormal muscle depolarization and paralysis during thyrotoxic episodes[7][6]. No direct small molecule therapeutic modulators are established, but genetic screening for KCNJ18 mutations provides a biomarker for periodic paralysis risk[7].

Other names

Kir2.6TTPP2Potassium inwardly rectifying channel subfamily J member 18Potassium channel, inwardly rectifying subfamily J member 18Potassium voltage-gated channel subfamily J member 18Thyrotoxic periodic paralysis susceptibility ion channelInwardly rectifying potassium channel 18KCNJ18phKCNJ18

Modulation of potassium flux across the muscle cell membrane; Stabilization of resting membrane potential