The ATP-sensitive potassium (KATP) channel is a member of inward rectifier potassium channel (Kir) that is inhibited by intracellular ATP and functions in close relation to sulfonylurea receptors (SUR). Although the molecular mechanism and physiological function of KATP channels are well understood, the expression pattern during development or treatment with the channel modulators such as glybenclamide is little known. In this work, we determined mRNA levels of a KATP channel (Kir6.2) and a sulfonylurea receptor (SUR2) in rat tissues by RNase protection assay. Levels of Kir6.2 and SUR2 mRNA in the rat brain and skeletal muscle were higher in adult (90-120 days) than in neonate (2-8 days), whereas those in the heart were not much different between neonate (2-8 days) and adult (90-120 days). In addition, none of KATP channel modulators (opener, pinacidil and nicorandil; blocker, glybenclamide) affected the Kir6.2 mRNA levels in the heart, brain and skeletal muscle. The results indicate that the expression of Kir and SUR genes can vary age-dependently, but the expression of Kir is not dependent on the long-term treatment of channel modulators. The effect of the channel modulators on mRNA level of SUR is remained to be studied further.
Adenosine Triphosphate ; Adult* ; Animals ; Brain ; Glyburide ; Heart ; Humans ; Infant, Newborn* ; KATP Channels ; Muscle, Skeletal ; Nicorandil ; Pinacidil ; Potassium Channels* ; Potassium Channels, Inwardly Rectifying ; Potassium* ; Rats* ; Ribonucleases ; RNA, Messenger ; Sulfonylurea Receptors

G protein-coupled inward rectifier K(+) channel 4(GIRK4) is a G protein-coupled inward rectifier potassium channel family member. Encoded by the KCNJ5, it is widely distributed in the mammalian heart, brain, and other tissues and organs. Recent studies have demonstrated that the abnormal expression of GIRK4 gene is associated with atrial fibrillation, and meanwhile may be closely related to obesity, metabolic syndrome, and many other clinical conditions. Further research on the role the GIRK4 gene in the pathophysiology of these clinical conditions will definitely facilitate their clinical diagnosis and treatment.
Atrial Fibrillation ; genetics ; G Protein-Coupled Inwardly-Rectifying Potassium Channels ; genetics ; Humans ; Metabolic Syndrome ; genetics

OBJECTIVETo assess the association between polymorphisms of rs3740835(C/A) and rs2604204(A/C) in KCNJ5 gene with the susceptibility to unilateral and bilateral primary aldosteronism (PA).

METHODSA total of 1043 subjects were studied, which included 83 unilateral PA patients,142 bilateral PA patients and 818 essential hypertensive(EH) patients. The polymorphism of KCNJ5 gene at rs3740835(C/A) and rs2604204(A/C) position were analyzed with a TaqMan genotyping technique.

RESULTSFrequencies of A allele and AA+AC genotype at rs3740835(C/A) in unilateral PA group were significantly higher than EH group (P < 0.05). However, the above frequencies did not show a statistical significance between bilateral PA group and EH group (P > 0.05). No statistical difference was detected in the distribution of alleles or genotypes at rs2604204 (A/C) between unilateral PA and EH group or between bilateral PA and EH group. Haplotypic frequencies of C-A and A-A in unilateral PA group were significantly higher and lower than EH group, respectively. However, there was no statistical difference in the haplotype distribution between bilateral PA and EH groups.

CONCLUSIONRs3740835(C/A) polymorphism may be associated with unilateral PA but not with bilateral PA. rs2604204(A/C) polymorphism is not associated with either unilateral or bilateral PA. Haplotype C-A and A-A may respectively be susceptibility factor and protective factor for unilateral PA. No haplotype has been found to associate with bilateral PA.

Adult ; Female ; G Protein-Coupled Inwardly-Rectifying Potassium Channels ; genetics ; Haplotypes ; Humans ; Hyperaldosteronism ; genetics ; Male ; Middle Aged ; Polymorphism, Genetic

In the therapeutic or the nutritional aspects, Zn2+ has been used as a supplement in a variety of drugs. Most of divalent or trivalent cations affect ion channels in the cell membranes of various organs. In particular, Zn2+ has been regarded as a potassium (K+) channel blocker in the field of electrophysiology. ATP-sensitive K+ (KATP) channel, which is a kind of inward rectifier K+ channel, resides in the cell membrane of pancreatic beta cells and plays an important role in glucose-induced insulin secretion. The glucose increases intracellular ATP concentration, and this inhibits KATP channels. The inhibition of KATP channels activity depolarizes the cell, and subsequently, insulin is released by Ca2+ influx through the voltage- gated Ca2+ channels. Here, we demonstrate that KATP channels in the pancreatic beta cells are also the targets of extracellular Zn2+ blockade and its blockade is dependent on intracellular ATP concentration. This may be a compensatory mechanism preventing the oversecretion of insulin from the Pancreatic beta cells triggered by Zn2+ intake in a physiologically fasting condition.
Adenosine Triphosphate* ; Cations ; Cell Membrane ; Electrophysiology ; Fasting ; Glucose ; Insulin ; Insulin-Secreting Cells* ; Ion Channels ; KATP Channels* ; Potassium ; Potassium Channels, Inwardly Rectifying

AIMTo investigate the action and mechanism of Syn-1A in reversing the activation of K(ATP) channel induced by weak acidic pH.

METHODSThe patches excised from Kir6.2/SUR2A expressing HEK-293 cells were used to establish inside-out configuration. To examine the actions of weak acidic pH in activation of the channel and the reverse action of Syn-1A on it, the inside-out patches were continuously perfused with the solution of pH from 7.4, 7.0, 6.8, 6.5 to 6.0 with or without Syn-1A. In vitro binding was employed to study the influence of different pH to the binding of Syn-1A to SUR2A subunit.

RESULTSSyn-1A blocked pH 6.5, 6.8 and 7.0 induced activation of the channel, and Syn-1A binding to SUR2A were increased by reducing pH from 7.4 to 6.0.

CONCLUSIONSyn-1A would assert some inhibition of the KATP channels, which might temper the fluctuation of acidic pH-induced K(ATP) channel opening that could induce fatal re-entrant arrhythmias.

HEK293 Cells ; Humans ; Hydrogen-Ion Concentration ; KATP Channels ; metabolism ; Patch-Clamp Techniques ; Potassium Channels ; metabolism ; Potassium Channels, Inwardly Rectifying ; metabolism ; Syntaxin 1 ; pharmacology

This paper was aimed to investigate the effects of ATP-sensitive potassium channels on the proliferation and differentiation of rat preadipocytes. We examined the expression of sulphonylurea receptor 2 (SUR2) mRNA in preadipocytes and adipocytes obtained by inducing for 5 d and the effects of the inhibitor (glibenclamide) and opener (diazoxide) of ATP-sensitive potassium channels on the expression of SUR2 mRNA in preadipocytes by real-time PCR. Preadipocyte proliferation and cell cycle were measured by MTT spectrophotometry and flow cytometer. The content of intracellular lipid was measured by oil red O staining, cell diameter was determined by Image-Pro Plus 5.0 software and the expression of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) mRNA was estimated by RT-PCR. SUR2 mRNA was expressed in both preadipocytes and adipocytes obtained by inducing for 5 d, and the expression in adipocytes was obviously higher than that in preadipocytes. Glibenclamide inhibited the expression of SUR2 mRNA in preadipocyte, promoted preadipocyte proliferation in a dose-dependent manner, increased the cell percentages in G(2)/M + S phase, increased lipid content, augmented adipocyte diameter, and promoted the expression of PPAR-gamma mRNA. But the actions of diazoxide were contrary to those of glibenclamide. These results suggest that ATP-sensitive potassium channels regulate the proliferation and differentiation of preadipocytes, and PPAR-gamma is probably involved in the effect of ATP-sensitive potassium channels.
ATP-Binding Cassette Transporters ; genetics ; metabolism ; Adipocytes ; cytology ; Animals ; Cell Differentiation ; physiology ; Cell Proliferation ; Cells, Cultured ; KATP Channels ; physiology ; Male ; Obesity ; pathology ; PPAR gamma ; metabolism ; Potassium Channels, Inwardly Rectifying ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Sprague-Dawley ; Receptors, Drug ; genetics ; metabolism ; Sulfonylurea Receptors

ATP-sensitive potassium (K(ATP)) channels are widely distributed in vasculatures, and play an important role in the vascular tone regulation. The K(ATP) channels consist of 4 pore-forming inward rectifier K(+) channel (Kir) subunits and 4 regulatory sulfonylurea receptors (SUR). The major vascular isoform of K(ATP) channels is composed of Kir6.1/SUR2B, although low levels of other subunits are also present in vascular beds. The observation from transgenic mice and humans carrying Kir6.1/SUR2B channel mutations strongly supports that normal activity of the Kir6.1/SUR2B channel is critical for cardiovascular function. The Kir6.1/SUR2B channel is regulated by intracellular ATP and ADP. The channel is a common target of several vasodilators and vasoconstrictors. Endogenous vasopressors such as arginine vasopressin and α-adrenoceptor agonists stimulate protein kinase C (PKC) and inhibit the K(ATP) channels, while vasodilators such as β-adrenoceptor agonists and vasoactive intestinal polypeptide increase K(ATP) channel activity by activating the adenylate cyclase-cAMP-protein kinase A (PKA) pathway. PKC phosphorylates a cluster of 4 serine residues at C-terminus of Kir6.1, whereas PKA acts on Ser1387 in the nucleotide binding domain 2 of SUR2B. The Kir6.1/SUR2B channel is also inhibited by oxidants including reactive oxygen species allowing vascular regulation in oxidative stress. The molecular basis underlying such a channel inhibition is likely to be mediated by S-glutathionylation at a few cysteine residues, especially Cys176, in Kir6.1. Furthermore, the channel activity is augmented in endotoxemia or septic shock, as a result of the upregulation of Kir6.1/SUR2B expression. Activation of the nuclear factor-κB dependent transcriptional mechanism contributes to the Kir6.1/SUR2B channel upregulation by lipopolysaccharides and perhaps other toll-like receptor ligands as well. In this review, we summarize the vascular K(ATP) channel regulation under physiological and pathophysiological conditions, and discuss the importance of K(ATP) channel as a potentially useful target in the treatment and prevention of cardiovascular diseases.
ATP-Binding Cassette Transporters ; genetics ; physiology ; Animals ; Endotoxemia ; metabolism ; physiopathology ; Humans ; KATP Channels ; genetics ; physiology ; Mice ; Mice, Transgenic ; Muscle, Smooth, Vascular ; metabolism ; physiology ; Potassium Channels, Inwardly Rectifying ; genetics ; physiology ; Receptors, Drug ; genetics ; physiology ; Shock, Septic ; metabolism ; physiopathology ; Sulfonylurea Receptors ; Vasoconstriction ; physiology ; Vasodilation ; physiology ; Vasomotor System ; physiology

OBJECTIVE: To investigate the clinical characteristics and genetic basis for a child with Keppen-Lubinsky syndrome (KPLBS). METHODS: Trio-whole exome sequencing (Trio-WES) was carried out for the proband and her parents. Candidate variant was verified by Sanger sequencing and bioinformatic analysis. RESULTS: The child has featured peculiar facies including large eyes, alar hypoplasia, microretrognathia, premature aging appearance in addition with growth delay and mental retardation. Trio-WES has identified that she has carried a de novo variant of the KCNJ6 gene, namely c.460G>C (p.Gly154Arg). The variant has not been recorded in the database. Prediction of protein structure indicated that the variant may affect the potassium ion selective filtration structure channel in the transmembrane region of KCNJ6 protein, which may result in up regulation of the function of the channel. CONCLUSION The de novo c.460G>C (p.Gly154Arg) variant of the KCNJ6 gene probably underlay the KPLBS in this child. Above finding has enriched the genotypic and phenotype spectrum of this syndrome.
Cataract ; China ; Female ; G Protein-Coupled Inwardly-Rectifying Potassium Channels/genetics* ; Humans ; Hypogonadism/congenital* ; Intellectual Disability/genetics* ; Mutation ; Whole Exome Sequencing

Renal outer medullary potassium (ROMK) channel is an important K⁺ excretion channel in the body, and K⁺ secreted by the ROMK channels is most or all source of urinary potassium. Previous studies focused on the ROMK channels of thick ascending limb (TAL) and collecting duct (CD), while there were few studies on the involvement of ROMK channels of the late distal convoluted tubule (DCT2) in K⁺ excretion. The purpose of the present study was mainly to record the ROMK channels current in renal DCT2 and observe the effect of high potassium diet on the ROMK channels by using single channel and whole-cell patch-clamp techniques. The results showed that a small conductance channel current with a conductance of 39 pS could be recorded in the apical membrane of renal DCT2, and it could be blocked by Tertiapin-Q (TPNQ), a ROMK channel inhibitor. The high potassium diet significantly increased the probability of ROMK channel current occurrence in the apical membrane of renal DCT2, and enhanced the activity of ROMK channel, compared to normal potassium diet (P < 0.01). Western blot results also demonstrated that the high potassium diet significantly up-regulated the protein expression levels of ROMK channels and epithelial sodium channel (ENaC), and down-regulated the protein expression level of Na⁺-Cl^- cotransporter (NCC). Moreover, the high potassium diet significantly increased urinary potassium excretion. These results suggest that the high potassium diet may activate the ROMK channels in the apical membrane of renal DCT2 and increase the urinary potassium excretion by up-regulating the expression of renal ROMK channels.
Potassium Channels, Inwardly Rectifying/metabolism* ; Kidney Tubules, Distal/metabolism* ; Potassium/metabolism* ; Epithelial Sodium Channels/metabolism* ; Diet

OBJECTIVETo investigate the prevalence of KCNJ5 gene missense mutations and their role in patients with unilateral adrenal hyperplasia (UAH).

METHODSFourteen UAH tissues were collected through surgical resection, and all the tissues were confirmed by pathology. Peripheral blood samples of the same patients were collected as control. The coding regions of the KCNJ5 were detected by direct DNA sequencing. Protein structure and function were predicted with specific software.

RESULTSThree missense mutations were detected among the 14 patients with UAH, which included c.451G>C/A (p.G151R) (2/14), c.503T>G (p.L168R) (1/14), c.830T>A (p.S209T) (9/14). Among these, c.830T>A is a newly identified somatic mutation. Protein structure prediction showed that S209T lied in the second transmembrane domain, a conservation region of KCNJ5. S209 was also the phosphorylation site of PKC that is located in intracellular area.

CONCLUSIONMissense mutations of KCNJ5 gene may be associated with UAH. Protein structure prediction has suggested that KCNJ5 mutations may be associated with UAH.

Adrenal Hyperplasia, Congenital ; genetics ; Adult ; Aged ; Amino Acid Sequence ; Female ; G Protein-Coupled Inwardly-Rectifying Potassium Channels ; genetics ; Humans ; Male ; Middle Aged ; Molecular Sequence Data ; Mutation, Missense ; Sequence Analysis, DNA