Functional implications of KCNE subunit expression for the Kv7.5 (KCNQ5) channel.

Kv7 (KCNQ) proteins form a family of voltage-gated potassium channels that is comprised of five members, Kv7.1-Kv7.5. While Kv7.1 is crucial in the heart, the Kv7.2, Kv7.3, Kv7.4 and Kv7.5 channels contribute to the M-current in the nervous system. In addition to the brain, Kv7.5 is expressed in skeletal and smooth muscle, where its physiological role is currently under evaluation. Kv7 associations with KCNE accessory subunits (KCNE1-5) enhance channel diversity and their interaction provides mechanisms to respond to a variety of stimuli. KCNE peptides control the surface expression, voltage-dependence, kinetics of gating, unitary conductance, ion selectivity and pharmacology of several channels. KCNE subunits have been primarily studied in the heart; however, their activity in the brain and in many other tissues is being increasingly recognized. Here, we found that Kv7.5 and KCNE subunits are present in myoblasts. Therefore, oligomeric associations may underlie some Kv7.5 functional diversity in skeletal muscle. An extensive study in Xenopus oocytes and HEK-293 cells demonstrates that KCNE1 and KCNE3, but none of the other KCNE subunits, affect Kv7.5 currents. While KCNE1 slows activation and suppresses inward rectification, KCNE3 drastically inhibits Kv7.5 currents. In addition, KCNE1 increases Kv7.5 currents in HEK cells. Changes in gating and amplitude indicate functional interactions. Our results have physiological relevance since Kv7.5 is abundant in skeletal and smooth muscle and its association with KCNE peptides may fine-tune cellular responses.