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- Barro-Soria, Rene, et al.
(författare)
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KCNE1 and KCNE3 modulate KCNQ1 channels by affecting different gating transitions
- 2017
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : NATL ACAD SCIENCES. - 0027-8424 .- 1091-6490. ; 114:35, s. E7367-E7376
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Tidskriftsartikel (refereegranskat)abstract
- KCNE beta-subunits assemble with and modulate the properties of voltage-gated K+ channels. In the heart, KCNE1 associates with the alpha-subunit KCNQ1 to generate the slowly activating, voltage-dependent potassium current (IKs) in the heart that controls the repolarization phase of cardiac action potentials. By contrast, in epithelial cells from the colon, stomach, and kidney, KCNE3 coassembles with KCNQ1 to form K+ channels that are voltage-independent K+ channels in the physiological voltage range and important for controlling water and salt secretion and absorption. How KCNE1 and KCNE3 subunits modify KCNQ1 channel gating so differently is largely unknown. Here, we use voltage clamp fluorometry to determine how KCNE1 and KCNE3 affect the voltage sensor and the gate of KCNQ1. By separating S4 movement and gate opening by mutations or phosphatidylinositol 4,5-bisphosphate depletion, we show that KCNE1 affects both the S4 movement and the gate, whereas KCNE3 affects the S4 movement and only affects the gate in KCNQ1 if an intact S4-to-gate coupling is present. Further, we show that a triple mutation in the middle of the transmembrane (TM) segment of KCNE3 introduces KCNE1-like effects on the second S4 movement and the gate. In addition, we show that differences in two residues at the external end of the KCNE TM segments underlie differences in the effects of the different KCNEs on the first S4 movement and the voltage sensor-to-gate coupling.
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| 4. |
- Liin, Sara, et al.
(författare)
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Mechanisms Underlying the Dual Effect of Polyunsaturated Fatty Acid Analogs on Kv7.1
- 2018
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Ingår i: Cell Reports. - : CELL PRESS. - 2211-1247. ; 24:11, s. 2908-2918
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Tidskriftsartikel (refereegranskat)abstract
- Polyunsaturated fatty acid (PUFA) analogs represent a new class of potential anti-arrhythmic K(V)7.1 and K(V)7.1+KCNE1 channel activators. In this study, we describe dual independent activating effects of negatively charged PUFA analogs on K(V)7.1 and K(V)7.1+KCNE1 that are dependent on discrete channel motifs. PUFA analogs are critically dependent on K326 in S6 of K(V)7.1 to increase the maximum conductance and critically dependent on specific S4 arginines in K(V)7.1 to shift the voltage dependence of channel opening toward negative voltages. Our findings provide insights into how K(V)7.1+KCNE1 activators may interact electrostatically both with the pore domain and the voltage-sensing domain to augment channel activity. We believe that the molecular understanding of how PUFA analogs induce dual independent activating effects is an important step toward the development of effective anti-arrhythmic drugs that target K(V)7.1 channels.
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| 5. |
- Liin, Sara, et al.
(författare)
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Polyunsaturated fatty acid analogs act antiarrhythmically on the cardiac I-Ks channel
- 2015
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 112:18, s. 5714-5719
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Tidskriftsartikel (refereegranskat)abstract
- Polyunsaturated fatty acids (PUFAs) affect cardiac excitability. Kv7.1 and the beta-subunit KCNE1 form the cardiac I-Ks channel that is central for cardiac repolarization. In this study, we explore the prospects of PUFAs as I-Ks channel modulators. We report that PUFAs open Kv7.1 via an electrostatic mechanism. Both the polyunsaturated acyl tail and the negatively charged carboxyl head group are required for PUFAs to open Kv7.1. We further show that KCNE1 coexpression abolishes the PUFA effect on Kv7.1 by promoting PUFA protonation. PUFA analogs with a decreased pK(a) value, to preserve their negative charge at neutral pH, restore the sensitivity to open I-Ks channels. PUFA analogs with a positively charged head group inhibit I-Ks channels. These different PUFA analogs could be developed into drugs to treat cardiac arrhythmias. In support of this possibility, we show that PUFA analogs act antiarrhythmically in embryonic rat cardiomyocytes and in isolated perfused hearts from guinea pig.
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