Abstract
The KCNE proteins (KCNE1-5) are single transmembrane peptides that function as ancillary β-subunits of voltage-gated K+ channels. Functional coupling of KCNE1 (E1) with KCNQ1 (Q1) to form cardiac IKs channel is well documented. However, Q1 is also found to have an affinity for all other members of KCNEs. The present study tested the possibility for the formation of functional channels consisting of Q1, E1 and KCNE2 (E2). We constructed a plasmid encoding a fusion protein in which the N terminus of Q1 was fused to the C terminus of either E1 or E2, and characterized the function of heteromeric channels by measuring whole-cell currents from COS7 cells transiently transfected with the plasmids. It was comfirmed that E1-Q1 fusion channels produced voltage- and time-dependent currents, similar to those obtained by coexpression of E1 together with Q1, while E2-Q1 fusion channels evoked constitutively active time-independent currents, again similar to those induced by coexpression of E2 and Q1. Coexpression of the E1-Q1 with E2 results in time-dependent currents which had a faster deactivation time course and a more depolarized half-activation voltage, compared to the E1-Q1 current. On the other hand, coexpression of E2-Q1 and E1 exclusively produced voltage- and time-dependent current without any constitutively active component, providing a functional evidence to show that all E2-Q1 coassembles with E1. These results suggest that E1 and E2 can be couple to a Q1 channel molecule forming complexes with unique current properties. [J Physiol Sci. 2006;56 Suppl:S128]
