Gustina AS , Trudeau MC .

T32-GM 008181 NIGMS NIH HHS , R01 HL083121 NHLBI NIH HHS , T32 GM008181 NIGMS NIH HHS

             heart contraction

                long QT syndrome 1

           SHORT QT SYNDROME 1; SQT1

	Fig. 1. Regulation of deactivation gating by a recombinant N-terminal eag domain. (A) Schematic of hERG channel constructs. Two-electrode voltage-clamp recordings of a family of tail currents from (B) hERG YFP (closed squares), (C) hERG ΔN YFP (open squares) and (D) N1–135 CFP + hERG ΔN YFP (closed circles). Currents were elicited by the voltage pulse protocol indicated. Calibration bars, 1 μA and 250 ms. (E) Plots of the time constants (τ) derived from a single exponential fit (see Materials and Methods) to the tail currents in (B–D). Plots also include CFP + hERG ΔN YFP (open circles). Error bars are the SEM and are inside the points when not visible. n ≥ 6 for each. (F) Current traces from N-truncated hERG channels, eag domains: N-truncated hERG channels at the indicated ratios and wild-type hERG scaled to the peak at −100 mV for comparison. Zero current given by dotted line. Scale bar, 100 ms. (G) Box plot of time constants of deactivation, in which the middle line of the box is the mean, the top and bottom are the 75th and 25th percentiles, and the straight lines are the 90th and 10th percentiles. n ≥ 5 for each.
	Fig. 2. Proximity of the soluble hERG N-terminal eag domain and the core of the hERG channel measured using FRET. (A) Spectral method for measuring FRET and determining Ratio A. Spectra (red trace) were measured from cells coexpressing N1–135 CFP + hERG ΔN S620T YFP by excitation at 458 nm. Emission spectra of CFP (cyan) measured in a control experiment from oocytes expressing N1–135 CFP. Extracted spectra (F458, green trace) is the cyan spectra subtracted from the red spectra and contains the emission of YFP. Spectra (F488, black trace) from excitation of YFP by a 488-nm laser line. Ratio A is the F458 spectra normalized to F488 spectra. (B) Plot of Ratio A (red line) versus wavelength. (C) Determination of Ratio A0. As a control, the emission spectra from oocytes expressing hERG ΔN S620T YFP channels was determined with excitation with a 458 laser line (F458, red trace) and with excitation of a 488 laser line (F488, black trace). Ratio A0 is the F458 spectra normalized to F488 spectra. (D) Plot of Ratio A0 (red line) versus emission wavelength. (E) Bar graph of Ratio A − Ratio A0, a value directly related to FRET efficiency, for the indicated channels and bar graph of ratio of CFP intensity to YFP intensity (Fc/Fy). SEM is denoted by error bars; the number of experiments (n) is indicated in parentheses.
	Fig. 3. Reduced regulation of deactivation gating by soluble eag domains containing point mutations. Two-electrode voltage-clamp recordings of ionic current from (A) N1–135 (Y43A) CFP fragment + hERG ΔN YFP channels (inverted, closed triangle) and (B) N1–135 (R56Q) CFP fragment + hERG ΔN YFP channels (closed triangle). Calibration bar is 2 μA and 250 ms. (C) Plot of time constant (τ) of deactivation versus voltage. Time constants for N1–135 CFP + hERG ΔN YFP (closed circles) and hERG ΔN YFP (open squares) included for comparison. Error bars are the SEM and the n ≥ 3 for each point. (D) Bar graph of relative FRET efficiency (Ratio A − Ratio A0) and ratio of CFP to YFP (Fc/Fy) for the indicated channels. SEM is denoted by error bars; the number of experiments (n) is indicated in parentheses.
	Fig. 4. Regulation of deactivation gating in a hERG channel with an LQTS mutation by soluble eag domains. Two-electrode voltage-clamp recordings of ionic currents from (A) hERG Y43A (closed inverted triangle), (B) N1–135 CFP + hERG Y43A (open inverted triangle), (C) hERG R56Q (closed triangle), (D) N1–135 CFP + hERG R56Q (open triangle), and (E) N1–135 CFP + hERG YFP (diamond) elicited with the voltage pulse as indicated. Calibration bars are 2 μA and 250 ms. (F) Plot of deactivation time constant (τ). hERG YFP (closed squares) and hERG ΔN YFP (open squares) are included as a reference. Error bars are the SEM and the n ≥ 3 for each point. (G) Bar graph of relative FRET efficiency (Ratio A − Ratio A0) and ratio of CFP to YFP (Fc/Fy) for the indicated channels. SEM is denoted by error bars; the number of experiments (n) is indicated in parentheses.
	Fig. 5. Schematic for function of eag domain. (A) Interaction of the N-terminal eag domain with other regions of the hERG channel. (B) Interaction of the eag domain with the channel is noncovalent and does not require the proximal N-terminal region. (C) Soluble eag domains do not supplant eag domain in wild-type channels. (D) Soluble eag domains supplant eag domains with point mutations, indicating that the mutation weakened an eag domain–channel interaction.

Al-Owais, Role of intracellular domains in the function of the herg potassium channel. 2009, Pubmed

Al-Owais, Role of intracellular domains in the function of the herg potassium channel. 2009, Pubmed
Aydar, Functional characterization of the C-terminus of the human ether-à-go-go-related gene K(+) channel (HERG). 2001, Pubmed , Xenbase
Chen, Long QT syndrome-associated mutations in the Per-Arnt-Sim (PAS) domain of HERG potassium channels accelerate channel deactivation. 1999, Pubmed , Xenbase
Clancy, Cellular consequences of HERG mutations in the long QT syndrome: precursors to sudden cardiac death. 2001, Pubmed
Craven, Salt bridges and gating in the COOH-terminal region of HCN2 and CNGA1 channels. 2004, Pubmed , Xenbase
Curran, A molecular basis for cardiac arrhythmia: HERG mutations cause long QT syndrome. 1995, Pubmed
Erickson, Preassociation of calmodulin with voltage-gated Ca(2+) channels revealed by FRET in single living cells. 2001, Pubmed
Ferrer, The S4-S5 linker directly couples voltage sensor movement to the activation gate in the human ether-a'-go-go-related gene (hERG) K+ channel. 2006, Pubmed , Xenbase
Ficker, Molecular determinants of dofetilide block of HERG K+ channels. 1998, Pubmed , Xenbase
Herzberg, Transfer of rapid inactivation and sensitivity to the class III antiarrhythmic drug E-4031 from HERG to M-eag channels. 1998, Pubmed
Horrigan, Coupling between voltage sensor activation, Ca2+ binding and channel opening in large conductance (BK) potassium channels. 2002, Pubmed , Xenbase
Li, The human delta1261 mutation of the HERG potassium channel results in a truncated protein that contains a subunit interaction domain and decreases the channel expression. 1997, Pubmed
Liu, Negative charges in the transmembrane domains of the HERG K channel are involved in the activation- and deactivation-gating processes. 2003, Pubmed , Xenbase
Miranda, FRET with multiply labeled HERG K(+) channels as a reporter of the in vivo coarse architecture of the cytoplasmic domains. 2008, Pubmed
Miyawaki, Fluorescent indicators for Ca2+ based on green fluorescent proteins and calmodulin. 1997, Pubmed
Morais Cabral, Crystal structure and functional analysis of the HERG potassium channel N terminus: a eukaryotic PAS domain. 1998, Pubmed , Xenbase
Nakajima, Voltage-shift of the current activation in HERG S4 mutation (R534C) in LQT2. 1999, Pubmed , Xenbase
Patterson, Förster distances between green fluorescent protein pairs. 2000, Pubmed
Piper, Regional specificity of human ether-a'-go-go-related gene channel activation and inactivation gating. 2005, Pubmed
Piper, Gating currents associated with intramembrane charge displacement in HERG potassium channels. 2003, Pubmed , Xenbase
Rizzo, Optimization of pairings and detection conditions for measurement of FRET between cyan and yellow fluorescent proteins. 2006, Pubmed
Roden, Long QT syndrome: reduced repolarization reserve and the genetic link. 2006, Pubmed
Sale, Physiological properties of hERG 1a/1b heteromeric currents and a hERG 1b-specific mutation associated with Long-QT syndrome. 2008, Pubmed
Sanguinetti, Mutations of the S4-S5 linker alter activation properties of HERG potassium channels expressed in Xenopus oocytes. 1999, Pubmed , Xenbase
Sanguinetti, Two components of cardiac delayed rectifier K+ current. Differential sensitivity to block by class III antiarrhythmic agents. 1990, Pubmed
Sanguinetti, A mechanistic link between an inherited and an acquired cardiac arrhythmia: HERG encodes the IKr potassium channel. 1995, Pubmed , Xenbase
Schönherr, Molecular determinants for activation and inactivation of HERG, a human inward rectifier potassium channel. 1996, Pubmed , Xenbase
Selvin, Fluorescence resonance energy transfer. 1995, Pubmed
Shaner, A guide to choosing fluorescent proteins. 2005, Pubmed
Smith, Fast and slow voltage sensor movements in HERG potassium channels. 2002, Pubmed , Xenbase
Spector, Fast inactivation causes rectification of the IKr channel. 1996, Pubmed , Xenbase
Subbiah, Molecular basis of slow activation of the human ether-a-go-go related gene potassium channel. 2004, Pubmed , Xenbase
Tristani-Firouzi, Interactions between S4-S5 linker and S6 transmembrane domain modulate gating of HERG K+ channels. 2002, Pubmed , Xenbase
Trudeau, Functional analysis of a mouse brain Elk-type K+ channel. 1999, Pubmed , Xenbase
Trudeau, Dynamics of Ca2+-calmodulin-dependent inhibition of rod cyclic nucleotide-gated channels measured by patch-clamp fluorometry. 2004, Pubmed , Xenbase
Trudeau, HERG, a human inward rectifier in the voltage-gated potassium channel family. 1995, Pubmed
Viloria, Differential effects of amino-terminal distal and proximal domains in the regulation of human erg K(+) channel gating. 2000, Pubmed , Xenbase
Wang, Regulation of deactivation by an amino terminal domain in human ether-à-go-go-related gene potassium channels. 1998, Pubmed , Xenbase
Warmke, A family of potassium channel genes related to eag in Drosophila and mammals. 1994, Pubmed
Wynia-Smith, hERG gating microdomains defined by S6 mutagenesis and molecular modeling. 2008, Pubmed
Zheng, Rod cyclic nucleotide-gated channels have a stoichiometry of three CNGA1 subunits and one CNGB1 subunit. 2002, Pubmed , Xenbase