title: Mechanistic basis for type 2 long QT syndrome caused by KCNH2 mutations that disrupt conserved arginine residues in the voltage sensor.
abstract: KCNH2 encodes the Kv11.1 channel, which conducts the rapidly activating delayed rectifier K+ current (I Kr) in the heart. KCNH2 mutations cause type 2 long QT syndrome (LQT2), which increases the risk for life-threatening ventricular arrhythmias. LQT2 mutations are predicted to prolong the cardiac action potential (AP) by reducing I Kr during repolarization. Kv11.1 contains several conserved basic amino acids in the fourth transmembrane segment (S4) of the voltage sensor that are important for normal channel trafficking and gating. This study sought to determine the mechanism(s) by which LQT2 mutations at conserved arginine residues in S4 (R531Q, R531W or R534L) alter Kv11.1 function. Western blot analyses of HEK293 cells transiently expressing R531Q, R531W or R534L suggested that only R534L inhibited Kv11.1 trafficking. Voltage-clamping experiments showed that R531Q or R531W dramatically altered Kv11.1 current (I Kv11.1) activation, inactivation, recovery from inactivation and deactivation. Coexpression of wild type (to mimic the patients' genotypes) mostly corrected the changes in I Kv11.1 activation and inactivation, but deactivation kinetics were still faster. Computational simulations using a human ventricular AP model showed that accelerating deactivation rates was sufficient to prolong the AP, but these effects were minimal compared to simply reducing I Kr. These are the first data to demonstrate that coexpressing wild type can correct activation and inactivation dysfunction caused by mutations at a critical voltage-sensing residue in Kv11.1. We conclude that some Kv11.1 mutations might accelerate deactivation to cause LQT2 but that the ventricular AP duration is much more sensitive to mutations that decrease I Kr. This likely explains why most LQT2 mutations are nonsense or trafficking-deficient.
authors.affiliation: Department of Physiology, Center for Muscle Biology, University of Kentucky, 800 Rose St. MS508, Lexington, KY 40536, USA.
authors.forename: Christie M
authors.initials: CM
authors.lastname: McBride
authors.forename: Ashley M
authors.initials: AM
authors.lastname: Smith
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Smith
authors.forename: Allison R
authors.initials: AR
authors.lastname: Reloj
authors.forename: Ellyn J
authors.initials: EJ
authors.lastname: Velasco
authors.forename: Jonathan
authors.initials: J
authors.lastname: Powell
authors.forename: Claude S
authors.initials: CS
authors.lastname: Elayi
authors.forename: Daniel C
authors.initials: DC
authors.lastname: Bartos
authors.forename: Don E
authors.initials: DE
authors.lastname: Burgess
authors.forename: Brian P
authors.initials: BP
authors.lastname: Delisle
mesh_terms: D000200:Action Potentials; D019943:Amino Acid Substitution; D001120:Arginine; D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006352:Heart Ventricles / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D006801:Humans; D015640:Ion Channel Gating; D008133:Long QT Syndrome / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D020125:Mutation, Missense; D021381:Protein Transport / Q000235:genetics
chemical_list: D000072237:ERG1 Potassium Channel; D051638:Ether-A-Go-Go Potassium Channels; C000606913:KCNH2 protein, human; D001120:Arginine
references.citation: J Biol Chem. 1997 Jan 10;272(2):709-12
references.pmid: 8995353
references.citation: Circulation. 2005 Mar 1;111(8):961-8
references.pmid: 15699249
references.citation: J Physiol. 2005 Dec 1;569(Pt 2):367-79
references.pmid: 16166152
references.citation: Cardiovasc Res. 1999 Nov;44(2):283-93
references.pmid: 10690305
references.citation: Science. 1995 Jul 7;269(5220):92-5
references.pmid: 7604285
references.citation: Circulation. 1999 May 4;99(17):2290-4
references.pmid: 10226095
references.citation: J Gen Physiol. 1990 Jul;96(1):195-215
references.pmid: 2170562
references.citation: J Biol Chem. 2002 Feb 15;277(7):4989-98
references.pmid: 11741928
references.citation: J Biol Chem. 1998 Oct 2;273(40):26210-7
references.pmid: 9748304
references.citation: Biophys J. 1998 Jan;74(1):230-41
references.pmid: 9449325
references.citation: PLoS One. 2012;7(3):e32654
references.pmid: 22396785
references.citation: Circ Res. 1998 Aug 24;83(4):415-22
references.pmid: 9721698
references.citation: Circulation. 2009 Nov 3;120(18):1752-60
references.pmid: 19841300
references.citation: Biochem Biophys Res Commun. 2012 Jun 1;422(2):305-10
references.pmid: 22580281
references.citation: Cell Physiol Biochem. 2008;21(1-3):37-46
references.pmid: 18209470
references.citation: Biophys J. 2005 Jan;88(1):566-78
references.pmid: 15475579
references.citation: J Biol Chem. 2010 Jan 29;285(5):3319-29
references.pmid: 19940115
references.citation: J Biol Chem. 2005 Feb 25;280(8):7206-17
references.pmid: 15528201
references.citation: Circulation. 2000 Sep 5;102(10):1178-85
references.pmid: 10973849
references.citation: J Biol Chem. 1998 Aug 14;273(33):21061-6
references.pmid: 9694858
references.citation: J Membr Biol. 2005 Oct;207(3):169-81
references.pmid: 16550488
references.citation: Am J Physiol Heart Circ Physiol. 2004 Jun;286(6):H2434-41
references.pmid: 14975928
references.citation: Circulation. 2006 Jan 24;113(3):365-73
references.pmid: 16432067
references.citation: J Gen Physiol. 2000 Feb;115(2):123-38
references.pmid: 10653892
references.citation: Nature. 1991 Jan 24;349(6307):305-10
references.pmid: 1846229
references.citation: J Gen Physiol. 2004 Dec;124(6):703-18
references.pmid: 15545400
references.citation: JAMA. 2005 Dec 21;294(23):2975-80
references.pmid: 16414944
references.citation: J Physiol. 2004 Jul 15;558(Pt 2):417-31
references.pmid: 15181157
references.citation: J Biol Chem. 2011 Jun 24;286(25):22160-9
references.pmid: 21536673
references.citation: Nature. 2006 Mar 23;440(7083):463-9
references.pmid: 16554806
references.citation: J Biol Chem. 1999 Oct 29;274(44):31123-6
references.pmid: 10531299
references.citation: PLoS Comput Biol. 2011 May;7(5):e1002061
references.pmid: 21637795
references.citation: Proc Natl Acad Sci U S A. 1996 Mar 5;93(5):2208-12
references.pmid: 8700910
references.citation: Am J Physiol Heart Circ Physiol. 2010 Jun;298(6):H1842-9
references.pmid: 20363883
references.citation: J Biol Chem. 1999 Apr 9;274(15):10113-8
references.pmid: 10187793
references.citation: Cell. 1995 Mar 10;80(5):795-803
references.pmid: 7889573
references.citation: Circ Res. 2004 Jun 11;94(11):1418-28
references.pmid: 15192037
references.citation: Cell. 1995 Apr 21;81(2):299-307
references.pmid: 7736582
references.citation: Am J Physiol Cell Physiol. 2011 Jul;301(1):C75-85
references.pmid: 21490315