KCNA10: a novel ion channel functionally related to both voltage-gated potassium and CNG cation channels

• DOI: 10.1152/ajprenal.2000.278.6.f1013
• Publication Date: 2017-12-23T08:06:45Z
• Authors: Rainer Lang; George Lee; Weimin Liu; Shulan Tian; Hamid Rafi; Marcelo Orias; Alan S. Segal; Gary V. Desir
• Keywords: 0301 basic medicine; Patch-Clamp Techniques; Potassium Channels; Base Sequence; Cyclic Nucleotide-Gated Cation Channels; In Vitro Techniques; Second Messenger Systems; Ion Channels; Recombinant Proteins; Membrane Potentials; Xenopus laevis; 03 medical and health sciences; Potassium Channels, Voltage-Gated; Oocytes; Potassium Channel Blockers; Shaker Superfamily of Potassium Channels; Animals; Humans; Female; Rabbits; Ion Channel Gating; DNA Primers

Our laboratory previously cloned a novel rabbit gene ( Kcn1), expressed in kidney, heart, and aorta, and predicted to encode a protein with 58% amino acid identity with the K channel Shaker Kv1.3 (Yao X et al. Proc Natl Acad Sci USA 92: 11711–11715, 1995). Because Kcn1 did not express well (peak current in Xenopus laevis oocytes of 0.3 μA at +60 mV), the human homolog (KCNA10) was isolated, and its expression was optimized in oocytes. KCNA10 mediates voltage-gated K+currents that exhibit minimal steady-state inactivation. Ensemble currents of 5–10 μA at +40 mV were consistently recorded from injected oocytes. Channels are closed at the holding potential of −80 mV but are progressively activated by depolarizations more positive than −30 mV, with half-activation at +3.5 ± 2.5 mV. The channel displays an unusual inhibitor profile because, in addition to being blocked by classical K channel blockers (barium tetraethylammonium and 4-aminopyridine), it is also sensitive to inhibitors of cyclic nucleotide-gated (CNG) cation channels (verapamil and pimozide). Tail-current analysis shows a reversal potential shift of 47 mV/decade change in K concentration, indicating a K-to-Na selectivity ratio of at least 15:1. The phorbol ester phorbol 12-myristate 13-acetate, an activator of protein kinase C, inhibited whole cell current by 42%. Analysis of single-channel currents reveals a conductance of ∼11 pS. We conclude KCNA10 is a novel human voltage-gated K channel with features common to both K-selective and CNG cation channels. Given its distribution in renal blood vessels and heart, we speculate that KCNA10 may be involved in regulating the tone of renal vascular smooth muscle and may also participate in the cardiac action potential.