scholarly journals Structures of wild-type and H451N mutant human lymphocyte potassium channel KV1.3

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Sanling Liu ◽  
Yue Zhao ◽  
Hao Dong ◽  
Liang Xiao ◽  
Yong Zhang ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Human Lymphocyte ◽  
Wild Type

scholarly journals Disease-Linked Super-Trafficking of a Mutant Potassium Channel

2020 ◽  
Author(s):  
Hui Huang ◽  
Laura M. Chamness ◽  
Carlos G. Vanoye ◽  
Georg Kuenze ◽  
Jens Meiler ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Potassium Channel ◽  
Single Channel ◽  
Channel Activity ◽  
Wild Type ◽  
Channel Activation ◽  
Voltage Gated ◽  
Disease Mutations ◽  
Single Channel Activity

ABSTRACTGain-of-function (GOF) mutations in the KCNQ1 voltage-gated potassium channel can induce cardiac arrhythmia. We tested whether any of the known GOF disease mutations in KCNQ1 act by increasing the amount of KCNQ1 that reaches the cell surface—“super-trafficking”. We found that levels of R231C KCNQ1 in the plasma membrane are 5-fold higher than wild type KCNQ1. This arises from both enhanced translocon-mediated membrane integration of the S4 voltage-sensor helix and an energetic linkage of C231 with the V129 and F166 side chains. Whole-cell electrophysiology recordings confirmed that R231C KCNQ1 in complex with KCNE1 is constitutively active, but also revealed the single channel activity of this mutant to be only 20% that of WT. The GOF phenotype associated with R231C therefore reflects the net effects of super-trafficking, reduced single channel activity, and constitutive channel activation. These investigations document membrane protein super-trafficking as a contributing mechanism to human disease.

scholarly journals Integrated K+ channel and K+-Cl− cotransporter functions regulate fin proportionality in zebrafish

2019 ◽  
Author(s):  
Jennifer S. Lanni ◽  
David Peal ◽  
Laura Ekstrom ◽  
Haining Chen ◽  
Caroline Stanclift ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Missense Mutation ◽  
Signaling Pathway ◽  
Normal Development ◽  
Growth Restriction ◽  
K Channel ◽  
Loss Of Function ◽  
Wild Type ◽  
Original Size ◽  
Dose Dependent

SummaryThe coordination of growth during development establishes proportionality within and among the different anatomic structures of organisms. Innate memory of this proportionality is preserved, as shown in the ability of regenerating structures to return to their original size. Although the regulation of this coordination is incompletely understood, mutant analyses of zebrafish with long-finned phenotypes have uncovered important roles for bioelectric signaling in modulating growth and size of the fins and barbs. To date, long-finned mutants identified are caused by hypermorphic mutations, leaving unresolved whether such signaling is required for normal development. We isolated a new zebrafish mutant, schleier, with proportional overgrowth phenotypes caused by a missense mutation and loss of function in the K+-Cl− cotransporter Kcc4a. Genetic depletion of Kcc4a in wild-type fish leads to a dose-dependent loss of growth restriction in fins and barbs, supporting a requirement for Kcc4a in regulation of proportion. Epistasis experiments suggest that Kcc4a and the two-pore potassium channel Kcnk5b both contribute to a common bioelectrical signaling response in the fin. These data suggest that an integrated bioelectric signaling pathway is required for the coordination of size and proportion during development.Graphical Abstract

scholarly journals Cooperative endocytosis of the endosomal SNARE protein syntaxin-8 and the potassium channel TASK-1

2014 ◽  
Vol 25 (12) ◽  
pp. 1877-1891 ◽  
Author(s):  
Vijay Renigunta ◽  
Thomas Fischer ◽  
Marylou Zuzarte ◽  
Stefan Kling ◽  
Xinle Zou ◽  
...  
Keyword(s):  
Fluorescence Microscopy ◽  
Cell Surface ◽  
Potassium Channel ◽  
Total Internal Reflection ◽  
Xenopus Oocytes ◽  
Snare Proteins ◽  
Snare Protein ◽  
Wild Type ◽  
Mammalian Cell Lines ◽  
Functional Relevance

The endosomal SNARE protein syntaxin-8 interacts with the acid-sensitive potassium channel TASK-1. The functional relevance of this interaction was studied by heterologous expression of these proteins (and mutants thereof) in Xenopus oocytes and in mammalian cell lines. Coexpression of syntaxin-8 caused a fourfold reduction in TASK-1 current, a corresponding reduction in the expression of TASK-1 at the cell surface, and a marked increase in the rate of endocytosis of the channel. TASK-1 and syntaxin-8 colocalized in the early endosomal compartment, as indicated by the endosomal markers 2xFYVE and rab5. The stimulatory effect of the SNARE protein on the endocytosis of the channel was abolished when both an endocytosis signal in TASK-1 and an endocytosis signal in syntaxin-8 were mutated. A syntaxin-8 mutant that cannot assemble with other SNARE proteins had virtually the same effect as wild-type syntaxin-8. Total internal reflection fluorescence microscopy showed formation and endocytosis of vesicles containing fluorescence-tagged clathrin, TASK-1, and/or syntaxin-8. Our results suggest that the unassembled form of syntaxin-8 and the potassium channel TASK-1 are internalized via clathrin-mediated endocytosis in a cooperative manner. This implies that syntaxin-8 regulates the endocytosis of TASK-1. Our study supports the idea that endosomal SNARE proteins can have functions unrelated to membrane fusion.

scholarly journals Deletion of Kir5.1 Impairs Renal Ability to Excrete Potassium during Increased Dietary Potassium Intake

2019 ◽  
Vol 30 (8) ◽  
pp. 1425-1438 ◽  
Author(s):  
Peng Wu ◽  
Zhong-Xiuzi Gao ◽  
Dan-Dan Zhang ◽  
Xiao-Tong Su ◽  
Wen-Hui Wang ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Potassium Channel ◽  
Basolateral Membrane ◽  
Potassium Conductance ◽  
Plasma Potassium ◽  
Wild Type ◽  
High Potassium ◽  
Potassium Intake ◽  
Dietary Potassium ◽  
Low Potassium

BackgroundThe basolateral potassium channel in the distal convoluted tubule (DCT), comprising the inwardly rectifying potassium channel Kir4.1/Kir5.1 heterotetramer, plays a key role in mediating the effect of dietary potassium intake on the thiazide-sensitive NaCl cotransporter (NCC). The role of Kir5.1 (encoded by Kcnj16) in mediating effects of dietary potassium intake on the NCC and renal potassium excretion is unknown.MethodsWe used electrophysiology, renal clearance, and immunoblotting to study Kir4.1 in the DCT and NCC in Kir5.1 knockout (Kcnj16−/−) and wild-type (Kcnj16+/+) mice fed with normal, high, or low potassium diets.ResultsWe detected a 40-pS and 20-pS potassium channel in the basolateral membrane of the DCT in wild-type and knockout mice, respectively. Compared with wild-type, Kcnj16−/− mice fed a normal potassium diet had higher basolateral potassium conductance, a more negative DCT membrane potential, higher expression of phosphorylated NCC (pNCC) and total NCC (tNCC), and augmented thiazide-induced natriuresis. Neither high- nor low-potassium diets affected the basolateral DCT’s potassium conductance and membrane potential in Kcnj16−/− mice. Although high potassium reduced and low potassium increased the expression of pNCC and tNCC in wild-type mice, these effects were absent in Kcnj16−/− mice. High potassium intake inhibited and low intake augmented thiazide-induced natriuresis in wild-type but not in Kcnj16−/− mice. Compared with wild-type, Kcnj16−/− mice with normal potassium intake had slightly lower plasma potassium but were more hyperkalemic with prolonged high potassium intake and more hypokalemic during potassium restriction.ConclusionsKir5.1 is essential for dietary potassium’s effect on NCC and for maintaining potassium homeostasis.

Biophysical characteristics of a new mutation on the KCNQ1 potassium channel (L251P) causing long QT syndrome

2003 ◽  
Vol 81 (2) ◽  
pp. 129-134 ◽  
Author(s):  
Dominic Deschênes ◽  
Said Acharfi ◽  
Valerie Pouliot ◽  
Robert Hegele ◽  
Andrew Krahn ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Long Qt Syndrome ◽  
Potassium Currents ◽  
Regulatory Subunit ◽  
Dominant Negative Effect ◽  
Wild Type ◽  
Patch Clamp Technique ◽  
Long Qt ◽  
New Mutation ◽  
Qt Syndrome

The congenital long QT syndrome (LQTS) is a hereditary cardiac disease characterized by prolonged ventricular repolarization, syncope, and sudden death. Mutations causing LQTS have been identified in various genes that encode for ionic channels or their regulatory subunits. Several of these mutations have been reported on the KCNQ1 gene encoding for a potassium channel or its regulatory subunit (KCNE1). In this study, we report the biophysical characteristics of a new mutation (L251P) in the transmembrane segment 5 (S5) of the KCNQ1 potassium channel. Potassium currents were recorded from CHO cells transfected with either wild type or mutant KCNQ1 in the presence or in the absence of its regulatory subunit (KCNE1), using the whole-cell configuration of the patch clamp technique. Wild-type KCNQ1 current amplitudes are increased particularly by KCNE1 co-expression but no current is observed with the KCNQ1 (L251P) mutant either in the presence or in the absence of KCNE1. Coexpressing KCNE1 with equal amount of cDNAs encoding wild type and mutant KCNQ1 results in an 11-fold reduction in the amplitude of potassium currents. The kinetics of activation and inactivation and the activation curve are minimally affected by this mutation. Our results suggest that the dominant negative effect of the P251L mutation on KCNQ1 channel explains the prolonged repolarization in patients carrying this mutation.Key words: long QT syndrome, ventricular fibrillation, potassium channels, KCNQ1.

scholarly journals Differential robustness to specific potassium channel deletions in midbrain dopaminergic neurons

2019 ◽  
Author(s):  
Alexis Haddjeri-Hopkins ◽  
Béatrice Marqueze-Pouey ◽  
Monica Tapia ◽  
Fabien Tell ◽  
Marianne Amalric ◽  
...  
Keyword(s):  
Multivariate Analysis ◽  
Potassium Channel ◽  
Dopaminergic Neurons ◽  
Substantia Nigra Pars Compacta ◽  
Wild Type ◽  
Current Clamp ◽  
Compensatory Mechanisms ◽  
Knock Out ◽  
Midbrain Dopaminergic Neurons

AbstractQuantifying the level of robustness of neurons in ion channel knock-out (KO) mice depends on how exhaustively electrical phenotype is assessed. We characterized the variations in behavior and electrical phenotype of substantia nigra pars compacta (SNc) dopaminergic neurons in SK3 and Kv4.3 potassium channel KOs. SK3 and Kv4.3 KO mice exhibited a slight increase in exploratory behavior and impaired motor learning, respectively. Combining current-clamp characterization of 16 electrophysiological parameters and multivariate analysis, we found that the electrical phenotype of SK3 KO neurons was not different from wild-type neurons, while that of Kv4.3 KO neurons was significantly altered. Consistently, voltage-clamp recordings of the underlying currents demonstrated that the SK current charge was unchanged in SK3 KO neurons while the Kv4-mediated A-type current was virtually abolished in Kv4.3 KO neurons. We conclude that the robustness of SNc dopaminergic neurons to potassium channel deletions is highly variable, due to channel-specific compensatory mechanisms.

Identification and Biochemical Characterization of a Novel Nortriterpene Inhibitor of the Human Lymphocyte Voltage-Gated Potassium Channel, Kv1.3

Biochemistry ◽  
1999 ◽  
Vol 38 (16) ◽  
pp. 4922-4930 ◽  
Author(s):  
John P. Felix ◽  
Randal M. Bugianesi ◽  
William A. Schmalhofer ◽  
Robert Borris ◽  
Michael A. Goetz ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Human Lymphocyte ◽  
Biochemical Characterization ◽  
Voltage Gated

scholarly journals Kir4.1/Kir5.1 Activity Is Essential for Dietary Sodium Intake–Induced Modulation of Na-Cl Cotransporter

2018 ◽  
Vol 30 (2) ◽  
pp. 216-227 ◽  
Author(s):  
Peng Wu ◽  
Zhong-Xiuzi Gao ◽  
Xiao-Tong Su ◽  
Ming-Xiao Wang ◽  
Wen-Hui Wang ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Knockout Mice ◽  
Sodium Intake ◽  
Dietary Sodium ◽  
Wild Type ◽  
High Sodium ◽  
High Sodium Intake ◽  
Low Sodium ◽  
Inwardly Rectifying Potassium Channel ◽  
Urinary Potassium

BackgroundDietary sodium intake regulates the thiazide-sensitive Na-Cl cotransporter (NCC) in the distal convoluted tubule (DCT). Whether the basolateral, inwardly rectifying potassium channel Kir4.1/Kir5.1 (a heterotetramer of Kir4.1/Kir5.1) in the DCT is essential for mediating the effect of dietary sodium intake on NCC activity is unknown.MethodsWe used electrophysiology, renal clearance techniques, and immunoblotting to examine effects of Kir4.1/Kir5.1 in the DCT and NCC in wild-type and kidney-specific Kir4.1 knockout mice.ResultsLow sodium intake stimulated basolateral Kir4.1/Kir5.1 activity, increased basolateral K+ conductance, and hyperpolarized the membrane. Conversely, high sodium intake inhibited the potassium channel, decreased basolateral K+ currents, and depolarized the membrane. Low sodium intake increased total and phosphorylated NCC expression and augmented hydrochlorothiazide-induced natriuresis; high sodium intake had opposite effects. Thus, elevated NCC activity induced by low sodium intake was associated with upregulation of Kir4.1/Kir5.1 activity in the DCT, whereas inhibition of NCC activity by high sodium intake was associated with diminished Kir4.1/Kir5.1 activity. In contrast, dietary sodium intake did not affect NCC activity in knockout mice. Further, Kir4.1 deletion not only abolished basolateral K+ conductance and depolarized the DCT membrane, but also abrogated the stimulating effects induced by low sodium intake on basolateral K+ conductance and hyperpolarization. Finally, dietary sodium intake did not alter urinary potassium excretion rate in hypokalemic knockout and wild-type mice.ConclusionsStimulation of Kir4.1/Kir5.1 by low intake of dietary sodium is essential for NCC upregulation, and inhibition of Kir4.1/Kir5.1 induced by high sodium intake is a key step for downregulation of NCC.

scholarly journals Mechanism of hERG inhibition by gating-modifier toxin, APETx1, deduced by functional characterization

2020 ◽  
Author(s):  
Kazuki Matsumura ◽  
Takushi Shimomura ◽  
Yoshihiro Kubo ◽  
Takayuki Oka ◽  
Naohiro Kobayashi ◽  
...  
Keyword(s):  
Potassium Channel ◽  
Resting State ◽  
Mutational Analysis ◽  
Functional Characterization ◽  
Structural Basis ◽  
Related Gene ◽  
Wild Type ◽  
Hydrophobic Residues ◽  
Gating Modifier ◽  
Voltage Sensing Domain

AbstractHuman ether-à-go-go-related gene potassium channel 1 (hERG) is a voltage-gated potassium channel, the voltage-sensing domain (VSD) of which is targeted by a gating-modifier toxin, APETx1. Although it is known that APETx1 inhibits hERG by stabilizing the resting state, it remains unclear where and how APETx1 interacts with the VSD in the resting state. Here, we prepared a recombinant APETx1, which is structurally and functionally equivalent to the natural product. Electrophysiological analyses using wild type and mutants of APETx1 and hERG revealed that their hydrophobic residues, in addition to a previously reported acidic hERG residue, play key roles in the inhibition of hERG by APETx1. Docking models of the APETx1-VSD complex that satisfy the results of mutational analysis suggest a molecular recognition mode between APETx1 and the resting state of hERG; this would provide a structural basis for designing ligands that control hERG function by binding to the VSD.

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