Abstract
The slow depolarization-activated K+ ion channel formed by the alpha-subunit hKCNQ1 and the beta-subunit hKCNE1 was observed by two-electrode voltage-clamping in a Xenopus oocyte expression system. Channels formed by KCNQ1 alone, KCNQ1 and KCNE1 combined or by a fusion construct of KCNQ1 and KCNE1 (concatamer) were studied over a period of two weeks after injection of coding mRNA with the aim to investigate an apparent time-dependent change in channel characteristics. Analysis of voltage-activation and activation kinetics revealed that the heteromeric channel (KCNQ1+KCNE1) gradually changed its characteristics within a week of expression and ends up appearing similar to the homomeric channel (KCNQ1). In contrast there was no change in either homomeric or fusion construct channel characteristics. Brefeldin A (10ƒÝM) treatment decreased membrane capacitance with no effect on channel currents. We suggest that the KCN1 beta-subunit disappears from the oocyte membrane by time as indicated by the change in channel characteristics, and that it may disassociate from the alpha-subunits in a non-destructive way. This supports a short-term (days) regulatory role of the KNCE1 beta-subunit.
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