TRESK-like potassium channels in leukemic T cells

In this study, we present patch-clamp characterization of the background potassium current in human lymphoma (Jurkat cells), generated by voltage-independent 16 pS channels with a high (similar to 100-fold) K+/Na+ selectivity. Depending on the background K+ channels density, from few per cell up to similar to 1 open channel per mu m(2), resting membrane potential was in the range of - 40 to - 83 mV, approaching E-K= - 88 mV. The background K+ channels were insensitive to margotoxin (3 nM), apamine (3 nM), and clotrimazole (1 mu M), high-affinity blockers of the lymphocyte Kv1.3, SKCa2, and IKCa1 channels. The current depended weakly on external pH. Arachidonic acid (20 mu M) and Hg2+ (0.3 - 10 mu M) suppressed background K+ current in Jurkat cells by 75 - 90%. Background K+ current was weakly sensitive to TEA(+) (IC50 = 14 mM), and was efficiently suppressed by externally applied bupivacaine (IC50 = 5 mu M), quinine (IC50 = 16 mu M), and Ba2+ (2 mM). Our data, in particular strong inhibition by mercuric ions, suggest that background K+ currents expressed in Jurkat cells are mediated by TWIK-related spinal cord K+ (TRESK) channels belonging to the double-pore domain K+ channel family. The presence of human TRESK in the membrane protein fraction was confirmed by Western blot analysis.