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Oncotarget Apr 2016
Topics: Animals; COS Cells; Humans; Potassium Channels, Voltage-Gated; Stomach Neoplasms
PubMed: 26956055
DOI: 10.18632/oncotarget.7921 -
Journal of Neurophysiology Jul 2022Ion channel complexes typically consist of both pore-forming subunits and auxiliary subunits that do not directly conduct current but can regulate trafficking or alter...
Ion channel complexes typically consist of both pore-forming subunits and auxiliary subunits that do not directly conduct current but can regulate trafficking or alter channel properties. Isolating the role of these auxiliary subunits in neurons has proved difficult due to a lack of specific pharmacological agents and the potential for developmental compensation in constitutive knockout models. Here, we use cell-type-specific viral-mediated CRISPR/Cas9 mutagenesis to target the potassium channel auxiliary subunit Kvβ2 () in dopamine neurons in the adult mouse brain. We find that mutagenesis of reduces surface expression of Kv1.2, the primary Kv1 pore-forming subunit expressed in dopamine neurons, and shifts the voltage dependence of inactivation of potassium channel currents toward more hyperpolarized potentials. Loss of broadens the action potential waveform in spontaneously firing dopamine neurons recorded in slice, reduces the afterhyperpolarization amplitude, and increases spike timing irregularity and excitability, all of which is consistent with a reduction in potassium channel current. Similar effects were observed with mutagenesis of the pore-forming subunit Kv1.2 (). These results identify Kv1 currents as important contributors to dopamine neuron firing and demonstrate a role for Kvβ2 subunits in regulating the trafficking and gating properties of these ion channels. Furthermore, they demonstrate the utility of CRISPR-mediated mutagenesis in the study of previously difficult to isolate ion channel subunits. Here, we utilize CRISPR/Cas9-mediated mutagenesis in dopamine neurons in mice to target the gene encoding Kvβ2, an auxiliary subunit that forms a part of Kv1 channel complexes. We find that the absence of Kvβ2 alters action potential properties by reducing surface expression of pore-forming subunits and shifting the voltage dependence of channel inactivation. This work establishes a new function for Kvβ2 subunits and Kv1 complexes in regulating dopamine neuron activity.
Topics: Animals; Dopaminergic Neurons; Mice; Potassium Channels; Shaker Superfamily of Potassium Channels
PubMed: 35788155
DOI: 10.1152/jn.00194.2022 -
ELife Mar 2017Electron cryo-microscopy has revealed the three-dimensional structure of a potassium channel that has a central role in regulating the release of insulin from the...
Electron cryo-microscopy has revealed the three-dimensional structure of a potassium channel that has a central role in regulating the release of insulin from the pancreas.
Topics: Adenosine Triphosphate; Cryoelectron Microscopy; Insulin; Ions; Potassium Channels, Inwardly Rectifying; Sulfonylurea Receptors
PubMed: 28276322
DOI: 10.7554/eLife.25159 -
Channels (Austin, Tex.) 2016Voltage-gated potassium channels or Kv's are membrane proteins with fundamental physiological roles. They are composed of 2 main functional protein domains, the pore... (Review)
Review
Voltage-gated potassium channels or Kv's are membrane proteins with fundamental physiological roles. They are composed of 2 main functional protein domains, the pore domain, which regulates ion permeation, and the voltage-sensing domain, which is in charge of sensing voltage and undergoing a conformational change that is later transduced into pore opening. The voltage-sensing domain or VSD is a highly conserved structural motif found in all voltage-gated ion channels and can also exist as an independent feature, giving rise to voltage sensitive enzymes and also sustaining proton fluxes in proton-permeable channels. In spite of the structural conservation of VSDs in potassium channels, there are several differences in the details of VSD function found across variants of Kvs. These differences are mainly reflected in variations in the electrostatic energy needed to open different potassium channels. In turn, the differences in detailed VSD functioning among voltage-gated potassium channels might have physiological consequences that have not been explored and which might reflect evolutionary adaptations to the different roles played by Kv channels in cell physiology.
Topics: Electron Transport; Electrophysiological Phenomena; Potassium Channels, Voltage-Gated; Protein Domains
PubMed: 26794852
DOI: 10.1080/19336950.2016.1141842 -
Journal of Cardiovascular Pharmacology... Mar 2018The development of novel drugs specifically directed at the ion channels underlying particular features of cardiac action potential (AP) initiation, recovery, and... (Review)
Review
The development of novel drugs specifically directed at the ion channels underlying particular features of cardiac action potential (AP) initiation, recovery, and refractoriness would contribute to an optimized approach to antiarrhythmic therapy that minimizes potential cardiac and extracardiac toxicity. Of these, K channels contribute numerous and diverse currents with specific actions on different phases in the time course of AP repolarization. These features and their site-specific distribution make particular K channel types attractive therapeutic targets for the development of pharmacological agents attempting antiarrhythmic therapy in conditions such as atrial fibrillation. However, progress in the development of such temporally and spatially selective antiarrhythmic drugs against particular ion channels has been relatively limited, particularly in view of our incomplete understanding of the complex physiological roles and interactions of the various ionic currents. This review summarizes the physiological properties of the main cardiac potassium channels and the way in which they modulate cardiac electrical activity and then critiques a number of available potential antiarrhythmic drugs directed at them.
Topics: Action Potentials; Animals; Anti-Arrhythmia Agents; Drug Development; Heart; Heart Diseases; Heart Rate; Humans; Molecular Targeted Therapy; Myocytes, Cardiac; Potassium Channel Blockers; Potassium Channels
PubMed: 28946759
DOI: 10.1177/1074248417729880 -
Developmental Neuroscience 2021KCNQ2 and KCNQ3 pathogenic channel variants have been associated with a spectrum of developmentally regulated diseases that vary in age of onset, severity, and whether... (Review)
Review
KCNQ2 and KCNQ3 pathogenic channel variants have been associated with a spectrum of developmentally regulated diseases that vary in age of onset, severity, and whether it is transient (i.e., benign familial neonatal seizures) or long-lasting (i.e., developmental and epileptic encephalopathy). KCNQ2 and KCNQ3 channels have also emerged as a target for novel antiepileptic drugs as their activation could reduce epileptic activity. Consequently, a great effort has taken place over the last 2 decades to understand the mechanisms that control the assembly, gating, and modulation of KCNQ2 and KCNQ3 channels. The current view that KCNQ2 and KCNQ3 channels assemble as heteromeric channels (KCNQ2/3) forms the basis of our understanding of KCNQ2 and KCNQ3 channelopathies and drug design. Here, we review the evidence that supports the formation of KCNQ2/3 heteromers in neurons. We also highlight functional and transcriptomic studies that suggest channel composition might not be necessarily fixed in the nervous system, but rather is dynamic and flexible, allowing some neurons to express KCNQ2 and KCNQ3 homomers. We propose that to fully understand KCNQ2 and KCNQ3 channelopathies, we need to adopt a more flexible view of KCNQ2 and KCNQ3 channel stoichiometry, which might differ across development, brain regions, cell types, and disease states.
Topics: Epilepsy; Epilepsy, Benign Neonatal; Humans; KCNQ2 Potassium Channel; KCNQ3 Potassium Channel; Neurodevelopmental Disorders
PubMed: 33794528
DOI: 10.1159/000515495 -
Current Opinion in Nephrology and... Sep 2018Multiple clinical and translational evidence support benefits of high potassium diet; however, there many uncertainties underlying the molecular and cellular mechanisms... (Review)
Review
PURPOSE OF REVIEW
Multiple clinical and translational evidence support benefits of high potassium diet; however, there many uncertainties underlying the molecular and cellular mechanisms determining effects of dietary potassium. Kir4.1 and Kir5.1 proteins form a functional heteromer (Kir4.1/Kir5.1), which is the primary inwardly rectifying potassium channel on the basolateral membrane of both distal convoluted tubule (DCT) and the collecting duct principal cells. The purpose of this mini-review is to summarize latest advances in our understanding of the evolution, physiological relevance and mechanisms controlling these channels.
RECENT FINDINGS
Kir4.1 and Kir5.1 channels play a critical role in determining electrolyte homeostasis in the kidney and blood pressure, respectively. It was reported that Kir4.1/Kir5.1 serves as potassium sensors in the distal nephron responding to variations in dietary intake and hormonal stimuli. Global and kidney specific knockouts of either channel resulted in hypokalemia and severe cardiorenal phenotypes. Furthermore, knock out of Kir5.1 in Dahl salt-sensitive rat background revealed the crucial role of the Kir4.1/Kir5.1 channel in salt-induced hypertension.
SUMMARY
Here, we focus on reviewing novel experimental evidence of the physiological function, expression and hormonal regulation of renal basolateral inwardly rectifying potassium channels. Further investigation of molecular and cellular mechanisms controlling Kir4.1 and Kir4.1/Kir5.1-mediating pathways and development of specific compounds targeting these channels function is essential for proper control of electrolyte homeostasis and blood pressure.
Topics: Animals; Blood Pressure; Humans; Kidney Tubules, Collecting; Kidney Tubules, Distal; Potassium; Potassium Channels; Potassium Channels, Inwardly Rectifying; Potassium, Dietary; Rats; Sodium; Sodium, Dietary; Water-Electrolyte Balance; Kir5.1 Channel
PubMed: 29894319
DOI: 10.1097/MNH.0000000000000437 -
Journal of the Royal Society, Interface Aug 2022Mathematical models of voltage-gated ion channels are used in basic research, industrial and clinical settings. These models range in complexity, but typically contain...
Mathematical models of voltage-gated ion channels are used in basic research, industrial and clinical settings. These models range in complexity, but typically contain numerous variables representing the proportion of channels in a given state, and parameters describing the voltage-dependent rates of transition between states. An open problem is selecting the appropriate degree of complexity and structure for an ion channel model given data availability. Here, we simplify a model of the cardiac human Ether-à-go-go related gene (hERG) potassium ion channel, which carries cardiac , using the manifold boundary approximation method (MBAM). The MBAM approximates high-dimensional model-output manifolds by reduced models describing their boundaries, resulting in models with fewer parameters (and often variables). We produced a series of models of reducing complexity starting from an established five-state hERG model with 15 parameters. Models with up to three fewer states and eight fewer parameters were shown to retain much of the predictive capability of the full model and were validated using experimental hERG1a data collected in HEK293 cells at 37°C. The method provides a way to simplify complex models of ion channels that improves parameter identifiability and will aid in future model development.
Topics: ERG1 Potassium Channel; Ether-A-Go-Go Potassium Channels; HEK293 Cells; Heart; Humans; Ion Channels
PubMed: 35946166
DOI: 10.1098/rsif.2022.0193 -
Scientific Reports Jul 2021The voltage-dependent potassium channel Kv1.3 participates in the immune response. Kv1.3 is essential in different cellular functions, such as proliferation, activation...
The voltage-dependent potassium channel Kv1.3 participates in the immune response. Kv1.3 is essential in different cellular functions, such as proliferation, activation and apoptosis. Because aberrant expression of Kv1.3 is linked to autoimmune diseases, fine-tuning its function is crucial for leukocyte physiology. Regulatory KCNE subunits are expressed in the immune system, and KCNE4 specifically tightly regulates Kv1.3. KCNE4 modulates Kv1.3 currents slowing activation, accelerating inactivation and retaining the channel at the endoplasmic reticulum (ER), thereby altering its membrane localization. In addition, KCNE4 genomic variants are associated with immune pathologies. Therefore, an in-depth knowledge of KCNE4 function is extremely relevant for understanding immune system physiology. We demonstrate that KCNE4 dimerizes, which is unique among KCNE regulatory peptide family members. Furthermore, the juxtamembrane tetraleucine carboxyl-terminal domain of KCNE4 is a structural platform in which Kv1.3, Ca/calmodulin (CaM) and dimerizing KCNE4 compete for multiple interaction partners. CaM-dependent KCNE4 dimerization controls KCNE4 membrane targeting and modulates its interaction with Kv1.3. KCNE4, which is highly retained at the ER, contains an important ER retention motif near the tetraleucine motif. Upon escaping the ER in a CaM-dependent pattern, KCNE4 follows a COP-II-dependent forward trafficking mechanism. Therefore, CaM, an essential signaling molecule that controls the dimerization and membrane targeting of KCNE4, modulates the KCNE4-dependent regulation of Kv1.3, which in turn fine-tunes leukocyte physiology.
Topics: Amino Acid Motifs; Amino Acid Sequence; Animals; Calmodulin; Cell Membrane; Electrophysiological Phenomena; Gene Expression; HEK293 Cells; Humans; Ion Channel Gating; Kv1.3 Potassium Channel; Leukocytes; Models, Biological; Organ Specificity; Potassium Channels, Voltage-Gated; Protein Binding; Protein Conformation; Protein Interaction Domains and Motifs; Protein Multimerization
PubMed: 34234241
DOI: 10.1038/s41598-021-93562-5 -
International Journal of Molecular... Jan 2021Substance use disorders (SUDs) are ubiquitous throughout the world. However, much remains to be done to develop pharmacotherapies that are very efficacious because the... (Review)
Review
Substance use disorders (SUDs) are ubiquitous throughout the world. However, much remains to be done to develop pharmacotherapies that are very efficacious because the focus has been mostly on using dopaminergic agents or opioid agonists. Herein we discuss the potential of using potassium channel activators in SUD treatment because evidence has accumulated to support a role of these channels in the effects of rewarding drugs. Potassium channels regulate neuronal action potential via effects on threshold, burst firing, and firing frequency. They are located in brain regions identified as important for the behavioral responses to rewarding drugs. In addition, their expression profiles are influenced by administration of rewarding substances. Genetic studies have also implicated variants in genes that encode potassium channels. Importantly, administration of potassium agonists have been shown to reduce alcohol intake and to augment the behavioral effects of opioid drugs. Potassium channel expression is also increased in animals with reduced intake of methamphetamine. Together, these results support the idea of further investing in studies that focus on elucidating the role of potassium channels as targets for therapeutic interventions against SUDs.
Topics: Action Potentials; Alcohol Drinking; Humans; Methamphetamine; Potassium Channel Blockers; Potassium Channels; Substance-Related Disorders
PubMed: 33513859
DOI: 10.3390/ijms22031249