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 ( approximately 100-fold) K(+)/Na(+) selectivity. Depending on the background K(+) channels density, from few per cell up to approximately 1 open channel per mum(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 muM), high-affinity blockers of the lymphocyte Kv1.3, SKCa2, and IKCa1 channels. The current depended weakly on external pH. Arachidonic acid (20 muM) and Hg(2+) (0.3-10 muM) suppressed background K(+) current in Jurkat cells by 75-90%. Background K(+) current was weakly sensitive to TEA(+) (IC(50) = 14 mM), and was efficiently suppressed by externally applied bupivacaine (IC(50) = 5 muM), quinine (IC(50) = 16 muM), and Ba(2+) (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.