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KCNE1‐induced increase in KCNQ1 currents is not mediated through enhanced membrane expression
Author(s) -
Hammami Sofia,
Klaerke Dan A,
Willumsen Niels J
Publication year - 2010
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.24.1_supplement.610.6
Subject(s) - xenopus , chemistry , potassium channel , biophysics , patch clamp , conductance , ion channel , membrane potential , voltage clamp , inward rectifier potassium ion channel , electrophysiology , biochemistry , biology , physics , neuroscience , receptor , condensed matter physics , gene
Association of the voltage‐activated potassium channel KCNQ1 with the accessory protein subunit KCNE1 gives rise to the cardiac IKs delayed rectifier potassium current. Aside from altering the kinetics of the KCNQ1 channel current, KCNE1 also augments the KCNQ1 current. This increase in macroscopic current is due either to an increase in ion channel conductance (γ), the open state probability (P o ) or an increase in the number of channels in the plasma membrane (N). The latter can be quantified by measuring the level of KCNQ1 surface expression by using an enzyme‐linked immunoassay. To do this, we employed a HA‐tagged version of the KCNQ1 channel and expressed it in presence or absence of KCNE1 in Xenopus oocytes. The HA‐tag, which is located at the second extracellular loop of the protein, allowed us to “count” the number of KCNQ1 channels expressed in the cell membrane. In parallel, currents were measured with two electrode voltage clamp. The results show that the KCNQ1 surface expression is ~70% lower when KCNE1 is co‐expressed compared to KCNQ1 alone despite a ~20% higher current for the heteromeric KCNQ1/KCNE1. This indicates that the overall increase of the KCNQ1 current, when co‐expressed with KCNE1, is not due to an increase in ion channel surface expression but rather to an increase in single‐channel conductance or in open state probability.