TASK-1 Protein, Human (sf9)

TASK-1 is a K(+) channel that conducts voltage-dependent outward rectifying currents upon membrane depolarization, with voltage sensing coupled to the K(+) electrochemical gradient via an 'ion flux gating' mechanism where outward (but not inward) ion flow opens the gate. Under extracellular acidification, it shifts ion selectivity to become Na(+)-permeable, likely through protonation of pH sensor His-98 stabilizing C-type inactivation conformations that transition the channel from outward K(+) conduction to inward Na(+) conduction and finally nonconductive states. Functional channels formed by homo- or heterodimerization exhibit distinct regulatory properties. Its fast-gating kinetics are critical for action potential repolarization/hyperpolarization phases (By similarity). In cerebellar granule cells, heteromeric KCNK3:KCNK9 channels may hyperpolarize resting membrane potential to suppress intrinsic excitability while enabling high-frequency firing upon depolarization (By similarity). Though dispensable for central chemosensory respiration, it conducts pH-sensitive currents to modulate firing of serotonergic raphe neurons involved in respiratory chemoreflex potentiation. It also confers chemosensitivity to carotid body type 1 cells for initiating ventilatory responses to hypoxia/hypercapnia (By similarity). In adrenal zona glomerulosa, it maintains hyperpolarized resting potential of aldosterone-producing cells to constrain secretion for blood pressure/electrolyte homeostasis (By similarity). In brown adipocytes, its K(+) efflux counters norepinephrine-induced depolarization to attenuate Ca²⁺/cAMP/PKA signaling and thermogenesis (By similarity).