Electrically silent potassium channel subunits from human lens epithelium

We describe the cloning and characterization of the first human members, hKv9.1 and hKv9.3, of the electrically silent delayed-rectifying-like K+channel subfamily. Their modulatory effects on the electrically active subfamily member hKv2.1 are also quantified. The hKv9 K+channels were isolated from a human lens epithelium cDNA library, but both hKv9.1 mRNA and hKv9.3 mRNA were found to coexist with the mRNA for hKv2.1 in a large number of human tissues. The hKv9.1 gene is composed of a minimum of five exons, with at least two alternatively spliced exons in the 5′-untranslated region (UTR). In contrast, the hKv9.3 gene is intronless across the coding region, 3′-UTR, and all of the analyzed 5′-UTR. Radiation hybrid mapping localized the hKv9.1 gene to 20q12 and the hKv9.3 gene to 2p24. Each electrically silent subunit, when coexpressed with hKv2.l, slows deactivation and inactivation compared with hKv2.1 expressed alone. In addition, each results in an increment in the single channel conductance.