Characterization of TASK-4, a novel member of the pH-sensitive, two-pore domain potassium channel family

We report the primary sequence of TASK-4, a novel member of the acid-sensitive subfamily of tandem pore K+ channels. TASK-4 transcripts are widely expressed in humans, with highest levels in liver, lung, pancreas, placenta, aorta and heart. In Xenopus oocytes TASK-4 generated K+ currents displaying a marked outward rectification which was lost bg. elevation of extracellular K+. TASK-4 currents were efficiently blocked by barium (83% inhibition at 2 mM), only weakly inhibited by 1 mM concentrations of quinine, bupivacaine and lidocaine, but not blocked by tetraethylammonium, 4-aminopyridine and Cs+. TASK-4 was sensitive to extracellular pH, but in contrast to other TASK channels, pH sensitivity was shifted to more alkaline pH, Thus, TASK-4 in concert with other TASK channels might regulate cellular membrane potential over a wide range of extracellular pH, (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V, All rights reserved.