Expression profile and characterisation of a truncated KCNQ5 splice variant.

Ion channels encoded by KCNQ genes (1-5) are key regulators of membrane properties in many cell types. The KCNQ5 gene was the last to be identified and has three splice variants that are expressed in human brain and skeletal muscle. The KCNQ5 encoded channel possesses M-current properties and so far no channelopathy has been associated with any of the three variants. We now show that only the shortest KCNQ5 variant, which has exon 9 deleted, was expressed in a variety of murine vascular smooth muscle. In Xenopus oocytes, this variant generated currents with amplitudes, activation kinetics and biophysical properties similar to the full-length variant normally expressed in neuronal tissue. Furthermore sensitivity to block by XE991 and activation by retigabine were also similar between both variants. These data represent an exhaustive characterisation of a truncated KCNQ5 splice variant that may contribute to the native XE991-sensitive channel in murine vasculature.