Regulation Of Potassium Channels Research Articles

Biallelic variants in POPDC2 cause a novel autosomal recessive syndrome presenting with cardiac conduction defects and variable hypertrophic cardiomyopathy.

ABSTRACTPOPDC2encodes for the Popeye domain-containing protein 2 which has an important role in cardiac pacemaking and conduction, due in part to its cAMP-dependent binding and regulation of TREK-1 potassium channels. Loss ofPopdc2in mice results in sinus pauses and bradycardia and morpholino knockdown ofpopdc2 inzebrafish results in atrioventricular (AV) block. We identified bi-allelic variants inPOPDC2in 4 families that presented with a phenotypic spectrum consisting of sinus node dysfunction, AV conduction defects and hypertrophic cardiomyopathy. Using homology modelling we show that the identifiedPOPDC2variants are predicted to diminish the ability of POPDC2 to bind cAMP. Inin vitroelectrophysiological studies we demonstrated that, while co-expression of wild-type POPDC2 with TREK-1 increased TREK-1 current density, POPDC2 variants found in the patients failed to increase TREK-1 current density. While patient muscle biopsy did not show clear myopathic disease, it showed significant reduction of the expression of both POPDC1 and POPDC2, suggesting that stability and/or membrane trafficking of the POPDC1–POPDC2 complex is impaired by pathogenic variants in any of the two proteins. Single-cell RNA sequencing from human hearts demonstrated that co-expression of POPDC1 and 2 was most prevalent in AV node, AV node pacemaker and AV bundle cells. Sinoatrial node cells expressed POPDC2 abundantly, but expression of POPDC1 was sparse. Together, these results concur with predisposition to AV node disease in humans with loss-of-function variants inPOPDC1and POPDC2 and presence of sinus node disease inPOPDC2,but not inPOPDC1related disease in human. Using population-level genetic data of more than 1 million individuals we showed that none of the familial variants were associated with clinical outcomes in heterozygous state, suggesting that heterozygous family members are unlikely to develop clinical manifestations and therefore might not necessitate clinical follow-up. Our findings provide evidence forPOPDC2as the cause of a novel Mendelian autosomal recessive cardiac syndrome, consistent with previous work showing that mice and zebrafish deficient in functionalPOPDC2display sinus and AV node dysfunction.GRAPHICAL ABSTRACT

Genome-wide association study of copy number variations with shank traits in a F2 crossbred chicken population.

Copy number variations (CNVs) are large-scale changes in the DNA sequence that can affect the genetic structure and phenotype of an organism. The purpose of this study was to investigate the existing CNVs and their associations with the shank diameter (ShD) and shank length (ShL) traits using data from an F2 crossbred chicken population. To carry out the study, 312 chickens were genotyped using the Illumina 60k SNP Beadchip. The shank traits of the birds were measured from day 1 to 12 weeks of age. penncnv and cnvruler tools were used to find copy numbers and regions with copy number changes (CNVR), respectively. The CNVRanger package was used to perform a genome-wide association study between shank traits and CNVs. Gene ontology research in CNVRs was carried out using the david database. In this investigation, 966 CNVs and 606 regions with copy number changes were discovered. The copy number states and variations were randomly distributed along the length of the autosomal chromosomes. Weeks 1-4, 9 and 12 of growth revealed a significant association of copy number variations with shank traits, false discovery rate (FDR-corrected p-value < 0.01), and the majority of CNVs that were statistically significant were found on chromosomes 1-3. These CNV segments are nearby genes such as KCNJ12, FGF6 and MYF5, which are fundamental to growth and development. In addition, gene set analyses revealed terms related to muscle physiology, regulation of cellular processes and potassium channels.

The complex regulation of Slo1 potassium channels from a structural perspective.

Fast and regulated potassium efflux by Slo1 channels is crucial in many tissues in animals including neurons, the kidney and smooth muscle. During the last decade, structures have revealed many details about the gating mechanism and regulation of these large and complex molecular machines. This review summarizes these findings and the current knowledge about the intricate regulation of these important channels. Slo1 integrates sensing of the membrane potential via a voltage-sensor domain that undergoes subtle but significant structural rearrangements with a calcium-induced expansion of parts of the intracellular gating ring. Together, these two signals synergistically lead to changes in the conformation and chemical nature of the pore domain, allowing potassium ions to be translocated. In many native tissues, Slo1 channels are assembled with at least three classes of auxiliary subunits that change the gating kinetics or allow the channel to open also in absence of one of the two signals. Finally, Slo1 is inhibited, activated or deregulated by natural toxins and synthetic compounds, underlining the importance of the channel for the organism and as a potential target for drugs and other molecules.

STINGing away the pain: the role of interferon-stimulated genes.

Pain and inflammation are biologically intertwined responses that warn the body of potential danger. In this issue of the JCI, Defaye, Bradaia, and colleagues identified a functional link between inflammation and pain, demonstrating that inflammation-induced activation of stimulator of IFN genes (STING) in dorsal root ganglia nociceptors reduced pain-like behaviors in a rodent model of inflammatory pain. Utilizing mice with a gain-of-function STING mutation, Defaye, Bradaia, and colleagues identified type I IFN regulation of voltage-gated potassium channels as the mechanism of this pain relief. Further investigation into mechanisms by which proinflammatory pathways can reduce pain may reveal druggable targets and insights into new approaches for treating persistent pain.

Overexpressed KCNK1 regulates potassium channels affecting molecular mechanisms and biological pathways in bladder cancer

BackgroundThis study aimed to explore the expression, molecular mechanism and its biological function of potassium two pore domain channel subfamily K member 1 (KCNK1) in bladder cancer (BC).MethodsWe integrated large numbers of external samples (n = 1486) to assess KCNK1 mRNA expression levels and collected in-house samples (n = 245) for immunohistochemistry (IHC) experiments to validate at the KCNK1 protein level. Single-cell RNA sequencing (scRNA-seq) analysis was performed to further assess KCNK1 expression and cellular communication. The transcriptional regulatory mechanisms of KCNK1 expression were explored by ChIP-seq, ATAC-seq and ChIA-PET data. Highly expressed co-expressed genes (HECEGs) of KCNK1 were used to explore potential signalling pathways. Furthermore, the immunoassay, clinical significance and molecular docking of KCNK1 were calculated.ResultsKCNK1 mRNA was significantly overexpressed in BC (SMD = 0.58, 95% CI [0.05; 1.11]), validated at the protein level (p < 0.0001). Upregulated KCNK1 mRNA exhibited highly distinguishing ability between BC and control samples (AUC = 0.82 [0.78–0.85]). Further, scRNA-seq analysis revealed that KCNK1 expression was predominantly clustered in BC epithelial cells and tended to increase with cellular differentiation. BC epithelial cells were involved in cellular communication mainly through the MK signalling pathway. Secondly, the KCNK1 transcription start site (TSS) showed promoter-enhancer interactions in three-dimensional space, while being transcriptionally regulated by GRHL2 and FOXA1. Most of the KCNK1 HECEGs were enriched in cell cycle–related signalling pathways. KCNK1 was mainly involved in cellular metabolism–related pathways and regulated cell membrane potassium channel activity. KCNK1 expression was associated with the level of infiltration of various immune cells. Immunotherapy and chemotherapy (docetaxel, paclitaxel and vinblastine) were more effective in BC patients in the high KCNK1 expression group. KCNK1 expression correlated with age, pathology grade and pathologic_M in BC patients.ConclusionsKCNK1 was significantly overexpressed in BC. A complex and sophisticated three-dimensional spatial transcriptional regulatory network existed in the KCNK1 TSS and promoted the upregulated of KCNK1 expression. The high expression of KCNK1 might be involved in the cell cycle, cellular metabolism, and tumour microenvironment through the regulation of potassium channels, and ultimately contributed to the deterioration of BC.

Satellite glial GPR37L1 and its ligand maresin 1 regulate potassium channel signaling and pain homeostasis.

G protein-coupled receptor 37-like 1 (GPR37L1) is an orphan GPCR with largely unknown functions. Here, we report that Gpr37l1/GRP37L1 ranks among the most highly expressed GPCR transcripts in mouse and human dorsal root ganglia (DRGs) and is selectively expressed in satellite glial cells (SGCs). Peripheral neuropathy induced by streptozotoxin (STZ) and paclitaxel (PTX) led to reduced GPR37L1 expression on the plasma membrane in mouse and human DRGs. Transgenic mice with Gpr37l1 deficiency exhibited impaired resolution of neuropathic pain symptoms following PTX- and STZ-induced pain, whereas overexpression of Gpr37l1 in mouse DRGs reversed pain. GPR37L1 is coexpressed with potassium channels, including KCNJ10 (Kir4.1) in mouse SGCs and both KCNJ3 (Kir3.1) and KCNJ10 in human SGCs. GPR37L1 regulates the surface expression and function of the potassium channels. Notably, the proresolving lipid mediator maresin 1 (MaR1) serves as a ligand of GPR37L1 and enhances KCNJ10- or KCNJ3-mediated potassium influx in SGCs through GPR37L1. Chemotherapy suppressed KCNJ10 expression and function in SGCs, which MaR1 rescued through GPR37L1. Finally, genetic analysis revealed that the GPR37L1-E296K variant increased chronic pain risk by destabilizing the protein and impairing the protein's function. Thus, GPR37L1 in SGCs offers a therapeutic target for the protection of neuropathy and chronic pain.

Role of Protein Kinase C in Metabolic Regulation of Coronary Endothelial Small Conductance Calcium-Activated Potassium Channels.

Small conductance calcium-activated potassium (SK) channels are largely responsible for endothelium-dependent coronary arteriolar relaxation. Endothelial SK channels are downregulated by the reduced form of nicotinamide adenine dinucleotide (NADH), which is increased in the setting of diabetes, yet the mechanisms of these changes are unclear. PKC (protein kinase C) is an important mediator of diabetes-induced coronary endothelial dysfunction. Thus, we aimed to determine whether NADH signaling downregulates endothelial SK channel function via PKC. SK channel currents of human coronary artery endothelial cells were measured by whole cell patch clamp method in the presence/absence of NADH, PKC activator phorbol 12-myristate 13-acetate, PKC inhibitors, or endothelial PKCα/PKCβ knockdown by using small interfering RNA. Human coronary arteriolar reactivity in response to the selective SK activator NS309 was measured by vessel myography in the presence of NADH and PKCβ inhibitor LY333531. NADH (30-300 μmol/L) or PKC activator phorbol 12-myristate 13-acetate (30-300 nmol/L) reduced endothelial SK current density, whereas the selective PKCᵦ inhibitor LY333531 significantly reversed the NADH-induced SK channel inhibition. PKCβ small interfering RNA, but not PKCα small interfering RNA, significantly prevented the NADH- and phorbol 12-myristate 13-acetate-induced SK inhibition. Incubation of human coronary artery endothelial cells with NADH significantly increased endothelial PKC activity and PKCβ expression and activation. Treating vessels with NADH decreased coronary arteriolar relaxation in response to the selective SK activator NS309, and this inhibitive effect was blocked by coadministration with PKCβ inhibitor LY333531. NADH-induced inhibition of endothelial SK channel function is mediated via PKCβ. These findings may provide insight into novel therapeutic strategies to preserve coronary microvascular function in patients with metabolic syndrome and coronary disease.

KCNAB2 overexpression inhibits human non-small-cell lung cancer cell growth in vitro and in vivo

Non-small-cell lung cancer (NSCLC) accounts for approximately 85% of all lung cancer cases. NSCLC patients often have poor prognosis demanding urgent identification of novel biomarkers and potential therapeutic targets. KCNAB2 (regulatory beta subunit2 of voltage-gated potassium channel), encoding aldosterone reductase, plays a pivotal role in regulating potassium channel activity. In this research, we tested the expression of KCNAB2 as well as its potential functions in human NSCLC. Bioinformatics analysis shows that expression of KCNAB2 mRNA is significantly downregulated in human NSCLC, correlating with poor overall survival. In addition, decreased KCNAB2 expression was detected in different NSCLC cell lines and local human NSCLC tissues. Exogenous overexpression of KCNAB2 potently suppressed growth, proliferation and motility of established human NSCLC cells and promoted NSCLC cells apoptosis. In contrast, CRISPR/Cas9-induced KCNAB2 knockout further promoted the malignant biological behaviors of NSCLC cells. Protein chip analysis in the KCNAB2-overexpressed NSCLC cells revealed that KCNAB2 plays a possible role in AKT-mTOR cascade activation. Indeed, AKT-mTOR signaling activation was potently inhibited following KCNAB2 overexpression in NSCLC cells. It was however augmented by KCNAB2 knockout. In vivo, the growth of subcutaneous KCNAB2-overexpressed A549 xenografts was significantly inhibited. Collectively, KCNAB2 could be a novel effective gene for prognosis prediction of NSCLC. Targeting KCNAB2 may lead to the development of advanced therapies.

Maternal Embryo Effect Arrest 31 (MEE31) is a moonlighting protein involved in GDP-D-mannose biosynthesis and KAT1 potassium channel regulation

Due to anthropogenic global warming, droughts are expected to increase and water availability to decrease in the coming decades. For this reason, research is increasingly focused on developing plant varieties and crop cultivars with reduced water consumption. Transpiration occurs through stomatal pores, resulting in water loss. Potassium plays a significant role in stomatal regulation. KAT1 is an inward-rectifying potassium channel that contributes to stomatal opening. Using a yeast high-throughput screening of an Arabidopsis cDNA library, MEE31 was found to physically interact with KAT1. MEE31 was initially identified in a screen for mutants with delayed embryonic development. The gene encodes a conserved phosphomannose isomerase (PMI). We report here that MEE31 interacts with and increases KAT1 activity in yeast and this interaction was also confirmed in plants. In addition, MEE31 complements the function of the yeast homologue, whereas the truncated version recovered in the screening does not, thus uncoupling the enzymatic activity from KAT1 regulation. We show that MEE31 overexpression leads to increased stomatal opening in Arabidopsis transgenic lines. Our data suggest that MEE31 is a moonlighting protein involved in both GDP-D-mannose biosynthesis and KAT1 regulation.

5-HT1A and 5-HT2B receptor interaction and co-clustering regulate serotonergic neuron excitability

Many psychiatric diseases have been associated with serotonin (5-HT) neuron dysfunction. The firing of 5-HT neurons is known to be under 5-HT1A receptor-mediated autoinhibition, but functional consequences of coexpressed receptors are unknown. Using co-immunoprecipitation, BRET, confocal, and super-resolution microscopy in hippocampal and 5-HT neurons, we present evidence that 5-HT1A and 5-HT2B receptors can form heterodimers and co-cluster at the plasma membrane of dendrites. Selective agonist stimulation of coexpressed 5-HT1A and 5-HT2B receptors prevents 5-HT1A receptor internalization and increases 5-HT2B receptor membrane clustering. Current clamp recordings of 5-HT neurons revealed that 5-HT1A receptor stimulation of acute slices from mice lacking 5-HT2B receptors in 5-HT neurons increased their firing activity trough Ca2+-activated potassium channel inhibition compared to 5-HT neurons from control mice. This work supports the hypothesis that the relative expression of 5-HT1A and 5-HT2B receptors tunes the neuronal excitability of serotonergic neurons through potassium channel regulation.

Inactivation of potassium channels by ceramide in rat pancreatic β-cells

Lipid regulation of ion channels is a fundamental mechanism in physiological processes as of neurotransmitter release and hormone secretion. Ceramide is a bioactive lipid proposed as a regulator of several voltage-gated ion channels including potassium channels (Kv). It is generated either de novo or by sphingomyelin (SM) hydrolysis in membranes of mammalian cells. In pancreatic β-cells, ceramide is the main sphingolipid associated with lipotoxicity and likely involved in cell dysfunction. Despite of the wealth of information regarding regulation of potassium channels by ceramides, the regulation of Kv channels by accumulated ceramide in native pancreatic β-cells has not been investigated. To do so, we used either the C2-ceramide, a cell-permeable short-chain analogue, or a sphingomyelinase (SMase C), a hydrolase causing ceramide to elevate from an endogenous production, in pancreatic β-cells of rat. C2-ceramide markedly accelerates steady-state current inactivation according to kinetic changes in the channel machinery. Interestingly, only C2-ceramide accelerates current inactivation while SMase C decreases both, peak-current and step-current amplitude supporting differential effects of ceramide derivatives. A specific inhibitor of the Kv2.1 channel (GxTX-1E), readily inhibits a fraction of the Kv channel current while no further inhibition by C2-ceramide superfusion can be observed supporting Kv2.1 channel involvement in the ceramide inhibition. Thus, intramembrane ceramide accumulation, as a lipidic metabolite released under cell-stress conditions, may alter pancreatic β-cell repolarization and secretion. These results may provide a new insight regarding lipid-protein regulation and advance our understanding in ceramide actions on Kv channels in pancreatic β-cells.

Role of protein kinase A and calcium/calmodulin-dependent protein kinase II in beta-adrenergic regulation of potassium channels in canine ventricular cardiomyocytes

Role of protein kinase A and calcium/calmodulin-dependent protein kinase II in beta-adrenergic regulation of potassium channels in canine ventricular cardiomyocytes

Induction of potassium channel regulator KCNE4 in a submandibular lymph node metastasis model

Cancer cells often metastasize to the lymph nodes (LNs) before disseminating throughout the body. Clinically, LN metastasis correlates with poor prognosis and influences treatment options. Many studies have shown that cancer cells communicate with immune and stromal cells to prepare a suitable niche for metastasis. In this study, mice were injected with B16–F10 murine melanoma cells to generate a tongue submandibular lymph node (SLN) metastasis model in which genes of interest could be investigated. Microarray analyses were performed on SLNs, identifying 162 upregulated genes, some of which are known metastasis genes. Among these upregulated genes, Kcne4, Slc7a11, Fscn1, and Gadd45b were not associated with metastasis, and increased expression of Kcne4 and Slc7a11 was confirmed by real-time PCR and immunohistochemistry. The roles of KCNE4 in chemokine production and cell adhesion were examined using primary lymphatic endothelial cells, and demonstrated that Ccl17 and Ccl19, which are involved in melanoma metastasis, were upregulated by KCNE4, as well as Mmp3 matrix metalloproteinase. Expression of KCNE4 was detected in human LNs with metastatic melanoma. In conclusion, we found that LN metastatic melanoma induces KCNE4 expression in the endothelium of LNs.

Flavonoid quercetin abolish paxilline inhibition of the mitochondrial BKCa channel

Large-conductance calcium-regulated potassium channel (BKCa) is known to play an important role in physiological and pathological processes. Despite the BKCa channel being encoded by one gene, this channel has been found to be located not only in the cell membrane but also in the membranes of intracellular compartments, such as in the inner mitochondrial membrane. With some differences, the mitochondrial BKCa (mitoBKCa) channel has been shown to be activated or inhibited by both synthetic and natural compounds. One of them, paxilline, has been considered to be a canonical blocker of this channel.In the previous study, we showed that the natural origin substance quercetin activates the mitoBKCa channel at ten times lower the concentration compared to channel present in the plasma membrane. Here, using the patch-clamp technique, we report that after inhibition of mitoBKCa channels by paxilline, quercetin activates these channels, indicating a paxilline and quercetin binding competition in the regulation of the mitoBKCa channel. To support our hypothesis, we used an analog of quercetin – isorhamnetin, a substance with one substituent changed. Isorhamnetin has no effect on the mitoBKCa channel activity, and after its application, paxilline fully inhibits the channel. Additionally, the molecular modeling studies were used. The results of docking quercetin and paxilline to the BKCa channel suggest that paxilline cannot bind after activation of the channel with quercetin. It seems that the likely mechanism of this phenomenon is the formation of spatial hindrance by quercetin. The results obtained shed a completely new, groundbreaking in the paxilline context, light on the current knowledge about mitochondrial potassium channel regulation.

ATP-sensitive Potassium Channel Subunits in Neuroinflammation: Novel Drug Targets in Neurodegenerative Disorders.

Arachidonic acids and its metabolites modulate plenty of ligand-gated, voltage-dependent ion channels, and metabolically regulated potassium channels including ATP-sensitive potassium channels (KATP). KATP channels are hetero-multimeric complexes of sulfonylureas receptors (SUR1, SUR2A or SUR2B) and the pore-forming subunits (Kir6.1 and Kir6.2) likewise expressed in the pre-post synapsis of neurons and inflammatory cells, thereby affecting their proliferation and activity. KATP channels are involved in amyloid-β (Aβ)-induced pathology, therefore emerging as therapeutic targets against Alzheimer's and related diseases. The modulation of these channels can represent an innovative strategy for the treatment of neurodegenerative disorders; nevertheless, the currently available drugs are not selective for brain KATP channels and show contrasting effects. This phenomenon can be a consequence of the multiple physiological roles of the different varieties of KATP channels. Openings of cardiac and muscular KATP channel subunits, are protective against caspase-dependent atrophy in these tissues and some neurodegenerative disorders, whereas in some neuroinflammatory diseases, benefits can be obtained through the inhibition of neuronal KATP channel subunits. For example, glibenclamide exerts an anti-inflammatory effect in respiratory, digestive, urological, and central nervous system (CNS) diseases, as well as in ischemia-reperfusion injury associated with abnormal SUR1-Trpm4/TNF-α or SUR1-Trpm4/ Nos2/ROS signaling. Despite this strategy being promising, glibenclamide may have limited clinical efficacy due to its unselective blocking action of SUR2A/B subunits also expressed in cardiovascular apparatus with pro-arrhythmic effects and SUR1 expressed in pancreatic beta cells with hypoglycemic risk. Alternatively, neuronal selective dual modulators showing agonist/antagonist actions on KATP channels can be an option.

First Author Spotlight

AnnouncementFirst Author SpotlightPublished Online:18 Jan 2022https://doi.org/10.1152/ajprenal.2022.322.1.AUMoreSectionsPDF (347 KB)Download PDFDownload PDFPlus ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInEmail NICOLAS MONTALBETTIRenal-Electrolyte Division, Department of Medicine, University of Pittsburgh, Pittsburgh, PennsylvaniaFigure 1.Nicolas MontalbettiDownload figureDownload PowerPointNicolas Montalbetti is a Research Instructor in the Renal-Electrolyte Division, Department of Medicine, at the University of Pittsburgh. He obtained his PhD in physiology at the University of Buenos Aires, where he studied transepithelial ion transport. His research interest focuses on basic neurophysiological aspects of the urinary tract system in health and disease [Photo: Fig. 1].https://doi.org/10.1152/ajprenal.00167.2021JAMES VOTAVADepartment of Nutritional Sciences, University of Wisconsin-Madison, Madison, WisconsinFigure 2.James VotavaDownload figureDownload PowerPointJames Votava is a PhD student in the Department of Nutritional Sciences at the University of Wisconsin-Madison, currently mentored by Dr. Brian Parks. He earned his BS in Biological Sciences from the University of Wisconsin-Madison before beginning his graduate studies in the laboratory of Dr. Rick Eisenstein. His research interest focuses on identifying new genetic modifiers of human disease. Outside of the laboratory, James enjoys playing recreational sports and spending time with his dog [Photo: Fig. 2].https://doi.org/10.1152/ajprenal.00537.2020ZHEN WANGDepartment of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MississippiFigure 3.Zhen WangDownload figureDownload PowerPointZhen Wang is an assistant professor of the Department of Physiology and Biophysics at University of Mississippi Medical Center. He received his PhD from the Pharmacology Department of the University of Arkansas for Medical Sciences and completed his postdoctoral training in the Department of Physiology and Biophysics, University of Mississippi Medical Center, under the mentorship of Dr. John Hall. His major research interest is to understand the pathophysiology of diabetic cardiovascular diseases and to determine the molecular mechanisms of target organ injury induced by diabetes, hypertension, and obesity [Photo: Fig. 3].https://doi.org/10.1152/ajprenal.00296.2021DAN-DAN ZHANGGuangdong-Hong-Kong Joint Laboratory on Immunological and Genetic Kidney Diseases, Guangdong Academy of Medical Sciences, Guangdong Provincial People’s Hospital, Guangzhou, ChinaFigure 4.Dan-Dan ZhangDownload figureDownload PowerPointDan-Dan Zhang has received her PhD at the Department of Physiology of Harbin Medical University in 2018, and she has continued her postdoctoral training in Dr. Wang and Dr. Lin’s laboratories in the Department of Pharmacology of New York Medical College. Her research has focused on studying the regulation of renal potassium and sodium channels in the aldosterone-sensitive distal nephron. Since 2021, she has worked in Guangdong Provincial People’s Hospital in China [Photo: Fig. 4].https://doi.org/10.1152/ajprenal.00306.2021This article has no references to display. Back to Top Next FiguresReferencesRelatedInformationRelated articlesBladder infection with uropathogenic Escherichia coli increases the excitability of afferent neurons 15 Dec 2021American Journal of Physiology-Renal PhysiologyDysregulation of the sensory and regulatory pathways controlling cellular iron metabolism in unilateral obstructive nephropathy 05 Jan 2022American Journal of Physiology-Renal PhysiologyTransient receptor potential cation channel 6 contributes to kidney injury induced by diabetes and hypertension 05 Jan 2022American Journal of Physiology-Renal PhysiologyROMK channels are inhibited in the aldosterone-sensitive distal nephron of renal tubule Nedd4-2-deficient mice 23 Dec 2021American Journal of Physiology-Renal Physiology More from this issue > Volume 322Issue 1January 2022Pages i-ii Crossmark Copyright & PermissionsCopyright © 2022 the American Physiological Society.https://doi.org/10.1152/ajprenal.2022.322.1.AUHistory Received 3 August 2021 Accepted 24 November 2021 Published online 18 January 2022 Published in print 1 January 2022 PDF download Metrics Downloaded 184 times

Differential roles of trithorax protein MLL-1 in regulating neuronal Ion channels

Repressive regulation of potassium channel genes by Polycomb group (PcG) proteins contributes to PcG protein-mediated neuroprotection against neuronal ischemic injury, as seen in an ischemic stroke. Here we asked the question whether Trithorax group (TrxG) proteins, the antagonistic partners of PcG proteins (i.e, epigenetic activators targeting the same genes) may also regulate potassium channels. Results of patch-clamp studies on cultured neuronal cells showed that inhibition of TrxG protein MLL-1 led to an increase in potassium channel activity, an unexpected effect for a presumed gene activator. In contrast, decreased sodium currents were observed with MLL-1 inhibition. Increased or decreased levels of potassium channel protein Kv2.1 or sodium channel protein Nav1.2, respectively, were seen with MLL-1 inhibition, as determined by immunocytochemistry. These results, for the first time, demonstrate an involvement of TrxG protein MLL-1 in regulating neuronal ion channels, potentially repressing potassium channel genes.

Deletion of the Wilms' Tumor Suppressor Gene in the Cardiac Troponin-T Lineage Reveals Novel Functions of WT1 in Heart Development.

Expression of Wilms’ tumor suppressor transcription factor (WT1) in the embryonic epicardium is essential for cardiac development, but its myocardial expression is little known. We have found that WT1 is expressed at low levels in 20–25% of the embryonic cardiomyocytes. Conditional ablation of WT1 using a cardiac troponin T driver (Tnnt2Cre) caused abnormal sinus venosus and atrium development, lack of pectinate muscles, thin ventricular myocardium and, in some cases, interventricular septum and cardiac wall defects, ventricular diverticula and aneurisms. Coronary development was normal and there was not embryonic lethality, although survival of adult mutant mice was reduced probably due to perinatal mortality. Adult mutant mice showed electrocardiographic anomalies, including increased RR and QRS intervals, and decreased PR intervals. RNASeq analysis identified differential expression of 137 genes in the E13.5 mutant heart as compared to controls. GO functional enrichment analysis suggested that both calcium ion regulation and modulation of potassium channels are deeply altered in the mutant myocardium. In summary, together with its essential function in the embryonic epicardium, myocardial WT1 expression is also required for normal cardiac development.

Allisartan ameliorates vascular remodeling through regulation of voltage-gated potassium channels in hypertensive rats

BackgroundThe objective of the present study was to determine the effect of allisartan, a new angiotensin II type 1 receptor antagonist on vascular remodeling through voltage gated potassium channels (Kv7) in hypertensive rats.Methods The study included a total of 47 Sprague Dawley (SD) rats. The animals were randomized to sham operation (n = 14), untreated hypertensive control group (n = 18) and allisartan treatment group (n = 15). Using renal artery stenosis, hypertension was induced in animals. Single dose of allisartan was administered intra-gastrically to animals in the allisartan treatment group and match placebo in the other 2 groups. Wire myography was used to measure the muscle tension in isolated mesenteric arteries from the animals. Real-time polymerase chain reaction was used to quantify the expression of Kv7 channel mRNA subunits.ResultsAfter 4 weeks of treatment, a significant decrease in mean arterial, systolic and diastolic blood pressure (SBP and DBP) was observed in allisartan treatment group compared to hypertension control group. The median arterial wall thickness and area/diameter ratio reduced significantly in treatment group compared to untreated hypertension group (P < 0.05). Wire myography demonstrated increased relaxation of mesenteric artery with increase in concentration of ML213. A significant up-regulation in the expression of all Kv7 mRNA subunits was observed in allisartan group compared to untreated hypertension group.ConclusionsFrom the results, allisartan was found to lower BP and preserve vascular remodeling through Kv7 channels.

Identification of the Large-Conductance Ca2+-Regulated Potassium Channel in Mitochondria of Human Bronchial Epithelial Cells

Mitochondria play a key role in energy metabolism within the cell. Potassium channels such as ATP-sensitive, voltage-gated or large-conductance Ca2+-regulated channels have been described in the inner mitochondrial membrane. Several hypotheses have been proposed to describe the important roles of mitochondrial potassium channels in cell survival and death pathways. In the current study, we identified two populations of mitochondrial large-conductance Ca2+-regulated potassium (mitoBKCa) channels in human bronchial epithelial (HBE) cells. The biophysical properties of the channels were characterized using the patch-clamp technique. We observed the activity of the channel with a mean conductance close to 285 pS in symmetric 150/150 mM KCl solution. Channel activity was increased upon application of the potassium channel opener NS11021 in the micromolar concentration range. The channel activity was completely inhibited by 1 µM paxilline and 300 nM iberiotoxin, selective inhibitors of the BKCa channels. Based on calcium and iberiotoxin modulation, we suggest that the C-terminus of the protein is localized to the mitochondrial matrix. Additionally, using RT-PCR, we confirmed the presence of α pore-forming (Slo1) and auxiliary β3-β4 subunits of BKCa channel in HBE cells. Western blot analysis of cellular fractions confirmed the mitochondrial localization of α pore-forming and predominately β3 subunits. Additionally, the regulation of oxygen consumption and membrane potential of human bronchial epithelial mitochondria in the presence of the potassium channel opener NS11021 and inhibitor paxilline were also studied. In summary, for the first time, the electrophysiological and functional properties of the mitoBKCa channel in a bronchial epithelial cell line were described.