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Mutation of KCNE3 alters activation of KCNQ1 but not channel block by Ba 2+
Author(s) -
Duffey Michael,
Beahm Derek,
Goldstein Andrea,
Dlugos Cynthia,
Morales Michael,
Rasmusson Randall
Publication year - 2006
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.20.4.a799-d
Subject(s) - xenopus , gating , protein subunit , mutation , extracellular , biophysics , chemistry , biology , biochemistry , gene
In secretory epithelial cells, KCNQ1 associates with the KCNE3 subunit to form a constitutively active, voltage‐insensitive channel. We demonstrate by RT‐PCR the presence of KCNQ1 and KCNE3 mRNAs in the human liver secretory cell line, Mz‐ChA1, and show using immunofluorescence that KCNQ1 is expressed in rat liver secretory ducts. In the heart KCNQ1 interacts with the KCNE1 subunit to form a voltage‐gated K + channel. To determine mechanisms of subunit interaction, we expressed KCNQ1 in Xenopus oocytes and determined the effects of the blocker Ba 2+ on current‐voltage relationships. Bath Ba 2+ (5 mM) slows activation and reduces (24%) KCNQ1 currents. Ba 2+ causes the constitutively active K + currents of KCNQ1 co‐expressed with KCNE3 to become slowly‐activating and dramatically reduced (42%). KCNQ1+KCNE1 currents are very slowly activated and Ba 2+ has little (16%) effect. The dose‐inhibition curve for Ba 2+ on KCNQ1 shows two binding components with affinities at 10 μM and 20 mM. The curve for KCNQ1+KCNE1 shows only one component (20 μM) and KCNQ1+KCNE3 shows one component (100 μM). We also determined the effects of a V72T mutation in KCNE3. KCNQ1+KCNE3(V72T) currents are slowly‐activating, like KCNQ1+KCNE1, while near steady‐state current‐voltage relationships are similar to KCNQ1 alone and inhibition by Ba 2+ (2 mM) is identical to that of KCNQ1+KCNE3. These results suggest that the site of regulation of KCNQ1 by KCNE1 or KCNE3 involves both the voltage‐sensitive gating mechanism and extracellular pore region of KCNQ1. (NIH 62465)