title: KCNE3 acts by promoting voltage sensor activation in KCNQ1.
abstract: KCNE β-subunits assemble with and modulate the properties of voltage-gated K(+) channels. In the colon, stomach, and kidney, KCNE3 coassembles with the α-subunit KCNQ1 to form K(+) channels important for K(+) and Cl(-) secretion that appear to be voltage-independent. How KCNE3 subunits turn voltage-gated KCNQ1 channels into apparent voltage-independent KCNQ1/KCNE3 channels is not completely understood. Different mechanisms have been proposed to explain the effect of KCNE3 on KCNQ1 channels. Here, we use voltage clamp fluorometry to determine how KCNE3 affects the voltage sensor S4 and the gate of KCNQ1. We find that S4 moves in KCNQ1/KCNE3 channels, and that inward S4 movement closes the channel gate. However, KCNE3 shifts the voltage dependence of S4 movement to extreme hyperpolarized potentials, such that in the physiological voltage range, the channel is constitutively conducting. By separating S4 movement and gate opening, either by a mutation or PIP2 depletion, we show that KCNE3 directly affects the S4 movement in KCNQ1. Two negatively charged residues of KCNE3 (D54 and D55) are found essential for the effect of KCNE3 on KCNQ1 channels, mainly exerting their effects by an electrostatic interaction with R228 in S4. Our results suggest that KCNE3 primarily affects the voltage-sensing domain and only indirectly affects the gate.
authors.affiliation: Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136 plarsson@med.miami.edu rbarro@med.miami.edu.
authors.forename: Rene
authors.initials: R
authors.lastname: Barro-Soria
authors.affiliation: Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136.
authors.forename: Marta E
authors.initials: ME
authors.lastname: Perez
authors.affiliation: Department of Physiology and Biophysics, Miller School of Medicine, University of Miami, Miami, FL 33136 plarsson@med.miami.edu rbarro@med.miami.edu.
authors.forename: H Peter
authors.initials: HP
authors.lastname: Larsson
mesh_terms: D000818:Animals; D001120:Arginine / Q000235:genetics / Q000378:metabolism; D001224:Aspartic Acid / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites / Q000235:genetics; D005260:Female; D006801:Humans; D015640:Ion Channel Gating / Q000235:genetics / Q000502:physiology*; D051657:KCNQ1 Potassium Channel / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008564:Membrane Potentials; D008954:Models, Biological; D009154:Mutation; D009865:Oocytes / Q000378:metabolism / Q000502:physiology*; D024642:Potassium Channels, Voltage-Gated / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011485:Protein Binding; D014982:Xenopus laevis
chemical_list: C418492:KCNE3 protein, human; D051657:KCNQ1 Potassium Channel; C496909:KCNQ1 protein, human; D024642:Potassium Channels, Voltage-Gated; D001224:Aspartic Acid; D001120:Arginine
keywords: KCNE3; KCNQ1; Kv7.1; voltage clamp fluorometry; voltage sensor