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Zn 2+ has biphasic effects on KCNQ1/KCNE3 K + channels
Author(s) -
Duffey Michael E,
Mongiardo Krystin,
Hallman Jason,
Crane Jokn K
Publication year - 2012
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.26.1_supplement.1152.9
Subject(s) - chemistry , xenopus , patch clamp , zinc , membrane potential , cysteine , glutathione , biophysics , voltage clamp , biochemistry , biology , enzyme , receptor , organic chemistry , gene
Basolateral membrane K + channels composed of KCNQ1 and the KCNE3 ancillary subunit play a critical role in epithelial tissue anion secretion by establishing electrical driving force. We are studying the effects on these channels of an inhibitor of intestinal secretion, Zn 2+ . When we used 8‐(4‐chlorophenylthio)‐cAMP (500 μM) to activate short circuit current (Isc) across human colonic T84 cell monolayers, Zn 2+ (2 mM zinc acetate) in the serosal bath transiently increased Isc from 21±6 to 97±12 μA/cm 2 , followed by inhibition to 9±4 μA/cm 2 (N=4). When cAMP‐mediated K + currents were measured using whole cell voltage clamp in isolated T84 cells exposed to VIP (200 nM), Zn 2+ (2 mM) caused a 487±47 pA increase in current followed by a 568±66 pA decline (N=3). To directly measure the effects of Zn 2+ , we co‐expressed KCNQ1 and KCNE3 in Xenopus oocytes and determined current‐voltage relationships. Zn 2+ (2mM) rapidly increased KCNQ1/KCNE3 currents from 1.9±0.7 to 4.6±1.2 μA (at +30 mV), then slowly inhibited the currents to 0.8±0.3 μA (N=4). To determine mechanism, we exposed oocytes to 5 mM glutathione before Zn 2+ (2mM), and Zn 2+ did not activate KCNQ1/KCNE3 currents (N=3). Rather, currents were inhibited to near zero values. These results suggest that Zn 2+ activates KCNQ1/KCNE3 K + channels via a thiol‐mediated mechanism, possibly at cysteine residues, while the mechanism of inhibition is unknown. (Supported by NIH AI 081528)