Comprehensive data on the relationship between KCNJ11 polymorphisms and gestational diabetes mellitus predisposition: a meta-analysis.

Purpose: The genetic aspect of gestational diabetes mellitus (GDM) is influenced by multiple causal genetic variants, each with different effect sizes. The KCNJ11 gene is particularly noteworthy as a potential contributor to the risk of GDM due to its role in regulating glucose-induced insulin secretion. To evaluate the association between KCNJ11 polymorphisms and GDM, a comprehensive meta-analysis was conducted to review the existing literature and quantitatively assess the correlation. Methods: A thorough search was performed on the PubMed, EMBASE, Scopus, and CNKI databases until December 25, 2023, using precise terms and keywords related to Gestational Diabetes, KCNJ11 gene, and polymorphism. Odds ratios and 95% confidence intervals were used to evaluate the relationships. The statistical analysis was conducted using Comprehensive Meta-Analysis software, and the Cochrane risk of bias assessment tool was used to determine bias presence. Results: The meta-analysis comprised 9 studies with 3108 GDM cases and 5374 controls for the rs5219 polymorphism, and 3 studies with 1209 GDM cases and 1438 controls for the rs5210 polymorphism. The pooled data indicated a noteworthy link between the rs5219 polymorphism and GDM globally and among various ethnic groups, notably in Caucasian and Asian populations. However, no substantial association was observed between the rs5210 polymorphism and GDM. Conclusions: Pooled data showed a correlation between the KCNJ11 rs5219 polymorphism and GDM susceptibility, but no association was found for the rs5210 polymorphism. Future research with larger sample sizes and more diverse populations is needed to improve result generalizability. Supplementary Information: The online version contains supplementary material available at 10.1007/s40200-024-01428-0.

Non-radioactive Rb+ Efflux Assay for Screening KATP Channel Modulators.

ATP-sensitive potassium (KATP) channels function as metabolic sensors that link cell membrane excitability to the cellular energy status by controlling potassium ion (K+) flow across the cell membrane according to intracellular ATP and ADP concentrations. As such, KATP channels influence a broad spectrum of physiological processes, including insulin secretion and cardiovascular functions. KATP channels are hetero-octamers, consisting of four inward rectifier potassium channel subunits, Kir6.1 or Kir6.2, and four sulfonylurea receptors (SURs), SUR1, SUR2A, or SUR2B. Different Kir6 and SUR isoforms assemble into KATP channel subtypes with distinct tissue distributions and physiological functions. Mutations in the genes encoding KATP channel subunits underlie various human diseases. Targeted treatment for these diseases requires subtype-specific KATP channel modulators. Rubidium ions (Rb+) also pass through KATP channels, and Rb+ efflux assays can be used to assess KATP channel function and activity. Flame atomic absorption spectroscopy (Flame-AAS) combined with microsampling can measure Rb+ in small volume, which provides an efficient tool to screen for compounds that alter KATP channel activity in Rb+ efflux assays. In this chapter, we describe a detailed protocol for Rb+ efflux assays designed to identify new KATP channel modulators with potential therapeutic utilities.

Dynamic duo: Kir6 and SUR in KATP channel structure and function.

KATP channels are ligand-gated potassium channels that couple cellular energetics with membrane potential to regulate cell activity. Each channel is an eight subunit complex comprising four central pore-forming Kir6 inward rectifier potassium channel subunits surrounded by four regulatory subunits known as the sulfonylurea receptor, SUR, which confer homeostatic metabolic control of KATP gating. SUR is an ATP binding cassette (ABC) protein family homolog that lacks membrane transport activity but is essential for KATP expression and function. For more than four decades, understanding the structure-function relationship of Kir6 and SUR has remained a central objective of clinical significance. Here, we review progress in correlating the wealth of functional data in the literature with recent KATP cryoEM structures.

Clinical and genetic characteristics of maturity-onset diabetes of the young type 13: A systematic review of the literature.

OBJECTIVE: Maturity-onset diabetes of the young type 13 (MODY13), a rare type of monogenic diabetes, is often misdiagnosed as type 1 or type 2 diabetes. To improve early diagnosis and precise treatment, we performed a systematic review and analysis of the literature about MODY13. METHODS: PubMed, Cochrane, Embase, China National Knowledge Infrastructure (CNKI), Chinese BioMedical (CBM) Literature Database, and Wanfang Database were searched using the following search terms: "MODY13," "KCNJ11 maturity-onset diabetes of the young," "KCNJ11-MODY," "maturity-onset diabetes of the young type 13," and "neonatal diabetes mellitus KCNJ11." The demography, clinical characteristics, and gene mutations of patients were expressed with descriptive statistical methods. RESULTS: A total of 33 reports were included in this study, including 75 patients and 28 types of mutations. Thirty-six patients were male. The mean onset age was 25.20 ± 15.26 years. The averages of recorded body mass index, glycated hemoglobin (HbA1c), and fasting C-peptide were 23.45 ± 4.56kg/m2 , 10.07 ± 1.96%, and 0.31 ± 0.23nmol/L, respectively. Most of the mutation sites were located in the cytosolic region of N- and C-terminal domains of Kir6.2. Seven patients were reported to have diabetic chronic complications. CONCLUSION: MODY13 was diagnosed later than other types of MODY and was associated with low fasting C-peptide. Mutation sites of MODY13 were mostly concentrated in N- and C-terminal intracellular domains. The majority of KCNJ11 gene mutations causing MODY 13 were from G to A. The incidence rates of chronic complications were lower than type 1 and type 2 diabetes.

CL-705G: a novel chemical Kir6.2-specific KATP channel opener.

Background: KATP channels have diverse roles, including regulation of insulin secretion and blood flow, and protection against biological stress responses and are excellent therapeutic targets. Different subclasses of KATP channels exist in various tissue types due to the unique assemblies of specific pore-forming (Kir6.x) and accessory (SURx) subunits. The majority of pharmacological openers and blockers act by binding to SURx and are poorly selective against the various KATP channel subclasses. Methods and Results: We used 3D models of the Kir6.2/SUR homotetramers based on existing cryo-EM structures of channels in both the open and closed states to identify a potential agonist binding pocket in a functionally critical area of the channel. Computational docking screens of this pocket with the Chembridge Core chemical library of 492,000 drug-like compounds yielded 15 top-ranked "hits", which were tested for activity against KATP channels using patch clamping and thallium (Tl+) flux assays with a Kir6.2/SUR2A HEK-293 stable cell line. Several of the compounds increased Tl+ fluxes. One of them (CL-705G) opened Kir6.2/SUR2A channels with a similar potency as pinacidil (EC50 of 9 µM and 11 µM, respectively). Remarkably, compound CL-705G had no or minimal effects on other Kir channels, including Kir6.1/SUR2B, Kir2.1, or Kir3.1/Kir3.4 channels, or Na+ currents of TE671 medulloblastoma cells. CL-705G activated Kir6.2Δ36 in the presence of SUR2A, but not when expressed by itself. CL-705G activated Kir6.2/SUR2A channels even after PIP2 depletion. The compound has cardioprotective effects in a cellular model of pharmacological preconditioning. It also partially rescued activity of the gating-defective Kir6.2-R301C mutant that is associated with congenital hyperinsulinism. Conclusion: CL-705G is a new Kir6.2 opener with little cross-reactivity with other channels tested, including the structurally similar Kir6.1. This, to our knowledge, is the first Kir-specific channel opener.

Corrigendum: Induced expression of kir6.2 in A1 astrocytes propagates inflammatory neurodegeneration via Drp1-dependent mitochondrial fission.

[This corrects the article DOI: 10.3389/fphar.2020.618992.].

KATP channel mutations in congenital hyperinsulinism: Progress and challenges towards mechanism-based therapies.

Congenital hyperinsulinism (CHI) is the most common cause of persistent hypoglycemia in infancy/childhood and is a serious condition associated with severe recurrent attacks of hypoglycemia due to dysregulated insulin secretion. Timely diagnosis and effective treatment are crucial to prevent severe hypoglycemia that may lead to life-long neurological complications. In pancreatic ß-cells, adenosine triphosphate (ATP)-sensitive K+ (KATP) channels are a central regulator of insulin secretion vital for glucose homeostasis. Genetic defects that lead to loss of expression or function of KATP channels are the most common cause of HI (KATP-HI). Much progress has been made in our understanding of the molecular genetics and pathophysiology of KATP-HI in the past decades; however, treatment remains challenging, in particular for patients with diffuse disease who do not respond to the KATP channel activator diazoxide. In this review, we discuss current approaches and limitations on the diagnosis and treatment of KATP-HI, and offer perspectives on alternative therapeutic strategies.

Synthesis and SAR of a novel Kir6.2/SUR1 channel opener scaffold identified by HTS.

Kir6.2/SUR1 is an ATP-regulated potassium channel that acts as an intracellular metabolic sensor, controlling insulin and appetite-stimulatory neuropeptides secretion. In this Letter, we present the SAR around a novel Kir6.2/SUR1 channel opener scaffold derived from an HTS screening campaign. New series of compounds with tractable SAR trends and favorable potencies are reported.

Personalized Therapeutics for KATP-Dependent Pathologies.

Ubiquitously expressed throughout the body, ATP-sensitive potassium (KATP) channels couple cellular metabolism to electrical activity in multiple tissues; their unique assembly as four Kir6 pore-forming subunits and four sulfonylurea receptor (SUR) subunits has resulted in a large armory of selective channel opener and inhibitor drugs. The spectrum of monogenic pathologies that result from gain- or loss-of-function mutations in these channels, and the potential for therapeutic correction of these pathologies, is now clear. However, while available drugs can be effective treatments for specific pathologies, cross-reactivity with the other Kir6 or SUR subfamily members can result in drug-induced versions of each pathology and may limit therapeutic usefulness. This review discusses the background to KATP channel physiology, pathology, and pharmacology and considers the potential for more specific or effective therapeutic agents.

Anti-epileptic effect of 2-deoxy-D-glucose by activation of miR-194/KATP signaling pathway. / 2-脱氧-D-葡萄糖激活miR-194/KATP信号通路发挥抗癫痫作用.

OBJECTIVES: Epilepsy is a syndrome of central nervous system dysfunction caused by many reasons, which is mainly characterized by abnormal discharge of neurons in the brain. Therefore, finding new targets for epilepsy therapy has always been the focus and hotspot in neurological research field. Studies have found that 2-deoxy-D-glucose (2-DG) exerts anti-epileptic effect by up-regulation of KATP channel subunit Kir6.1, Kir6.2 mRNA and protein. By using the database of TargetScan and miRBase to perform complementary pairing analysis on the sequences of miRNA and related target genes, it predicted that miR-194 might be the upstream signaling molecule of KATP channel. This study aims to explore the mechanism by which 2-DG exerts its anti-epileptic effect by regulating KATP channel subunits Kir6.1 and Kir6.2 via miR-194. METHODS: A magnesium-free epilepsy model was established and randomly divided into a control group, an epilepsy group (EP group), an EP+2-DG group, and miR-194 groups (including EP+miR-194 mimic, EP+miR-194 mimic+2-DG, EP+miR-194 mimic control, EP+miR-194 inhibitor, EP+miR-194 inhibitor+2-DG, and EP+miR-194 inhibitor control groups). The 2-DG was used to intervene miR-194 mimics, patch-clamp method was used to detect the spontaneous recurrent epileptiform discharges, real-time PCR was used to detect neuronal miR-194, Kir6.1, and Kir6.2 expressions, and the protein levels of Kir6.1 and Kir6.2were detected by Western blotting. RESULTS: Compared with the control group, there was no significant difference in the amplitude of spontaneous discharge potential in the EP group (P>0.05), but the frequency of spontaneous discharge was increased (P<0.05). Compared with the EP group, the frequency of spontaneous discharge was decreased (P<0.05). Compared with the EP+miR-194 mimic control group, the mRNA and protein expressions of Kir6.1 and Kir6.2 in the EP+miR-194 mimic group were down-regulated (all P<0.05). Compared with the EP+miR-194 inhibitor control group, the mRNA and protein expressions of Kir6.1 and Kir6.2 in the EP+miR-194 inhibitor group were up-regulated (all P<0.05). After pretreatment with miR-194 mimics, the mRNA and protein expression levels of KATP channel subunits Kir6.1 and Kir6.2 were decreased (all P<0.05). Compared with the EP+2-DG group, the mRNA and protein expression levels of Kir6.1 and Kir6.2 in the EP+miR-194 mimic+2-DG group were down-regulated (all P<0.05) and the mRNA and protein expression levels of Kir6.1 and Kir6.2 in the EP+miR-194 inhibitor+2-DG group were up-regulated (all P<0.05). CONCLUSIONS: The 2-DG might play an anti-epilepsy effect by up-regulating KATP channel subunits Kir6.1 and Kir6.2via miR-194.

Clinical presentation and long-term outcome of patients with KCNJ11/ABCC8 variants: Neonatal diabetes or MODY in the DPV registry from Germany and Austria.

OBJECTIVE: To describe clinical presentation/longterm outcomes of patients with ABCC8/KCNJ11 variants in a large cohort of patients with diabetes. RESEARCH DESIGN AND METHODS: We analyzed patients in the Diabetes Prospective Follow-up (DPV) registry with diabetes and pathogenic variants in the ABCC8/KCNJ11 genes. For patients with available data at three specific time-points-classification as K+ -channel variant, 2-year follow-up and most recent visit-the longitudinal course was evaluated in addition to the cross-sectional examination. RESULTS: We identified 93 cases with ABCC8 (n = 54)/KCNJ11 (n = 39) variants, 63 of them with neonatal diabetes. For 22 patients, follow-up data were available. Of these, 19 were treated with insulin at diagnosis, and the majority of patients was switched to sulfonylurea thereafter. However, insulin was still administered in six patients at the most recent visit. Patients were in good metabolic control with a median (IQR) A1c level of 6.0% (5.5-6.7), that is, 42.1 (36.6-49.7) mmol/mol after 2 years and 6.7% (6.0-8.0), that is, 49.7 (42.1-63.9) mmol/mol at the most recent visit. Five patients were temporarily without medication for a median (IQR) time of 4.0 (3.5-4.4) years, while two other patients continue to be off medication at the last follow-up. CONCLUSIONS: ABCC8/KCNJ11 variants should be suspected in children diagnosed with diabetes below the age of 6 months, as a high percentage can be switched from insulin to oral antidiabetic drugs. Thirty patients with diabetes due to pathogenic variants of ABCC8 or KCNJ11 were diagnosed beyond the neonatal period. Patients maintain good metabolic control even after a diabetes duration of up to 11 years.

Propolis Promotes Memantine-Dependent Rescue of Cognitive Deficits in APP-KI Mice.

Propolis is a complex resinous substance that is relevant as a therapeutic target for Alzheimer's disease (AD) and other neurodegenerative diseases. In this study, we confirmed that propolis (Brazilian green propolis) further enhances the rescue of cognitive deficits by the novel AD drug memantine in APP-KI mice. In memory-related behavior tasks, administration of a single dose of propolis at 1-100 mg/kg p.o. significantly enhanced the rescue of cognitive deficits by memantine at 1 mg/kg p.o. in APP-KI mice. In in vitro studies, propolis significantly increased intracellular Ca2+ concentration and calcium/calmodulin-dependent protein kinase II (CaMKII) autophosphorylation in Kir6.2-overexpressed N2A cells treated with memantine. Propolis also significantly increased adenosine 5'-triphosphate (ATP) contents and CaMKII autophosphorylation, which was impaired in Aß-treated Kir6.2-overexpressed N2A cells. Similarly, repeated administration of propolis at 100 mg/kg p.o. for 8 weeks further enhanced the rescue of cognitive deficits by memantine in APP-KI mice. Consistent with the rescued cognitive deficits in APP-KI mice, repeated administration of propolis markedly ameliorated memantine-dependent rescue of injured long-term potentiation (LTP) in APP-KI mice, concomitant with increased CaMKII autophosphorylation and calcium/calmodulin-dependent protein kinase IV (CaMKIV) phosphorylation in the hippocampal CA1 region. Furthermore, repeated administration of both memantine and propolis significantly restored the decreased ATP contents in the CA1 region of APP-KI mice. Finally, we confirmed that repeated administration of memantine at 1 mg/kg p.o. and propolis at 100 mg/kg p.o. for 8 weeks failed to restore the cognitive deficits in Kir6.2-/- mice. Our study demonstrates that propolis increases ATP contents and promotes the amelioration of cognitive deficits rescued by memantine via Kir6.2 channel inhibition in the CA1 region.

Sulfonylurea-Insensitive Permanent Neonatal Diabetes Caused by a Severe Gain-of-Function Tyr330His Substitution in Kir6.2.

BACKGROUND/AIMS: Mutations in KCNJ11, the gene encoding the Kir6.2 subunit of pancreatic and neuronal KATP channels, are associated with a spectrum of neonatal diabetes diseases. METHODS: Variant screening was used to identify the cause of neonatal diabetes, and continuous glucose monitoring was used to assess effectiveness of sulfonylurea treatment. Electrophysiological analysis of variant KATP channel function was used to determine molecular basis. RESULTS: We identified a previously uncharacterized KCNJ11 mutation, c.988T>C [p.Tyr330His], in an Italian child diagnosed with sulfonylurea-resistant permanent neonatal diabetes and developmental delay (intermediate DEND). Functional analysis of recombinant KATP channels reveals that this mutation causes a drastic gain-of-function, due to a reduction in ATP inhibition. Further, we demonstrate that the Tyr330His substitution causes a significant decrease in sensitivity to the sulfonylurea, glibenclamide. CONCLUSIONS: In this subject, the KCNJ11 (c.988T>C) mutation provoked neonatal diabetes, with mild developmental delay, which was insensitive to correction by sulfonylurea therapy. This is explained by the molecular loss of sulfonylurea sensitivity conferred by the Tyr330His substitution and highlights the need for molecular analysis of such mutations.

ATP-sensitive potassium channels in zebrafish cardiac and vascular smooth muscle.

ATP-sensitive potassium channels (KATP channels) are hetero-octameric nucleotide-gated ion channels that couple cellular metabolism to excitability in various tissues. In the heart, KATP channels are activated during ischaemia and potentially during adrenergic stimulation. In the vasculature, they are normally active at a low level, reducing vascular tone, but the ubiquitous nature of these channels leads to complex and poorly understood channelopathies as a result of gain- or loss-of-function mutations. Zebrafish (ZF) models of these channelopathies may provide insights to the link between molecular dysfunction and complex pathophysiology, but this requires understanding the tissue dependence of channel activity and subunit specificity. Thus far, direct analysis of ZF KATP expression and functional properties has only been performed in pancreatic ß-cells. Using a comprehensive combination of genetically modified fish, electrophysiology and gene expression analysis, we demonstrate that ZF cardiac myocytes (CM) and vascular smooth muscle (VSM) express functional KATP channels of similar subunit composition, structure and metabolic sensitivity to their mammalian counterparts. However, in contrast to mammalian cardiovascular KATP channels, ZF channels are insensitive to potassium channel opener drugs (pinacidil, minoxidil) in both chambers of the heart and in VSM. The results provide a first characterization of the molecular properties of fish KATP channels and validate the use of such genetically modified fish as models of human Cantú syndrome and ABCC9-related Intellectual Disability and Myopathy syndrome. KEY POINTS: Zebrafish cardiac myocytes (CM) and vascular smooth muscle (VSM) express functional KATP channels of similar subunit composition, structure and metabolic sensitivity to their mammalian counterparts. In contrast to mammalian cardiovascular KATP channels, zebrafish channels are insensitive to potassium channel opener drugs (pinacidil, minoxidil) in both chambers of the heart and in VSM. We provide a first characterization of the molecular properties of fish KATP channels and validate the use of such genetically modified fish as models of human Cantú syndrome and ABCC9-related Intellectual Disability and Myopathy syndrome.

Eugenosedin-A improves obesity-related hyperglycemia by regulating ATP-sensitive K+ channels and insulin secretion in pancreatic ß cells.

Eugenosedin-A (Eu-A) has been shown to protect against hyperglycemia- and hyperlipidemia-induced metabolic syndrome. We investigated the relationship of KATP channel activities and insulin secretion by Eu-A in vitro in pancreatic ß-cells, and examined the effect of Eu-A on streptozotocin (STZ)/nicotinamide (NA)-induced type 2 diabetes mellitus (T2DM) in vivo. We isolated pancreatic islets from adult male Wistar rats (250-350 g) and identified pancreatic ß-cells by the cell size, capacitance and membrane potential. Perforated patch-clamp and inside-out recordings were used to monitor the membrane potential (current-clamp mode) and channel activity (voltage-clamp mode) of ß-cells. The membrane potential of ß-cells was raised by Eu-A and reversed by the KATP channel activator diazoxide. Eu-A inhibited the KATP channel activity measured at - 60 mV and increased the intracellular calcium concentration ([Ca2+]i), resulting in enhanced insulin secretion. Eu-A also reduced Kir6.2 protein on the cell membrane and scattered in the cytosol under normal glucose conditions (5.6 mM). In our animal study, rats were divided into normal and STZ/NA-induced T2DM groups. Normal rats fed with regular chow were divided into control and control+Eu-A (5 mg/kg/day, i.p.) groups. The STZ/NA-induced diabetic rats fed with a high-fat diet (HFD) were divided into three groups: T2DM, T2DM+Eu-A (5 mg/kg/day, i.p.), and T2DM+glibenclamide (0.5 mg/kg/day, i.p.; a KATP channel inhibitor). Both Eu-A and glibenclamide decreased the rats' blood glucose, prevented weight gain, and enhanced insulin secretion. We found that Eu-A blocked pancreatic ß-cell KATP channels, caused membrane potential depolarization, and stimulated Ca2+ influx, thus increasing insulin secretion. Furthermore, Eu-A decreased blood glucose and increased insulin levels in T2DM rats. These results suggested that Eu-A might have clinical benefits for the control of T2DM and its complications.

Kir6.2 is essential to maintain neurite features by modulating PM20D1-reduced mitochondrial ATP generation.

Kir6.2, a pore-forming subunit of the ATP-sensitive potassium (KATP) channels, regulates the functions of metabolically active tissues and acts as an ideal therapeutic target for multiple diseases. Previous studies have been conducted on peripheral kir6.2, but its precise physiological roles in the central nervous system (CNS) have rarely been revealed. In the current study, we evaluated the neurophenotypes and neuroethology of kir6.2 knockout (kir6.2-/-) mice. We demonstrated the beneficial effects of kir6.2 on maintaining the morphology of mesencephalic neurons and controlling the motor coordination of mice. The mechanisms underlying the abnormal neurological features of kir6.2 deficiency were analyzed by RNA sequencing (RNA-seq). Pm20d1, a gene encoding PM20D1 secretase that promotes the generation of endogenous mitochondria uncouplers in vivo, was dramatically upregulated in the midbrain of kir6.2-/- mice. Further investigations verified that PM20D1-induced increase of N-acyl amino acids (N-AAAs) from circulating fatty acids and amino acids promoted mitochondrial impairments and cut down the ATP generation, which mediated the morphological defects of the mesencephalic neurons and thus led to the behavioral impairments of kir6.2 knockout mice. This study is the first evidence to demonstrate the roles of kir6.2 in the morphological maintenance of neurite and motor coordination control of mice, which extends our understanding of kir6.2/KATP channels in regulating the neurophysiological function.

Simulating PIP2-Induced Gating Transitions in Kir6.2 Channels.

ATP-sensitive potassium (KATP) channels consist of an inwardly rectifying K+ channel (Kir6.2) pore, to which four ATP-sensitive sulfonylurea receptor (SUR) domains are attached, thereby coupling K+ permeation directly to the metabolic state of the cell. Dysfunction is linked to neonatal diabetes and other diseases. K+ flux through these channels is controlled by conformational changes in the helix bundle region, which acts as a physical barrier for K+ permeation. In addition, the G-loop, located in the cytoplasmic domain, and the selectivity filter might contribute to gating, as suggested by different disease-causing mutations. Gating of Kir channels is regulated by different ligands, like Gßγ, H+, Na+, adenosine nucleotides, and the signaling lipid phosphatidyl-inositol 4,5-bisphosphate (PIP2), which is an essential activator for all eukaryotic Kir family members. Although molecular determinants of PIP2 activation of KATP channels have been investigated in functional studies, structural information of the binding site is still lacking as PIP2 could not be resolved in Kir6.2 cryo-EM structures. In this study, we used Molecular Dynamics (MD) simulations to examine the dynamics of residues associated with gating in Kir6.2. By combining this structural information with functional data, we investigated the mechanism underlying Kir6.2 channel regulation by PIP2.

Production and purification of ATP-sensitive potassium channel particles for cryo-electron microscopy.

ATP-sensitive potassium (KATP) channels are multimeric protein complexes made of four inward rectifying potassium channel (Kir6.x) subunits and four ABC protein sulfonylurea receptor (SURx) subunits. Kir6.x subunits form the potassium ion conducting pore of the channel, and SURx functions to regulate Kir6.x. Kir6.x and SURx are uniquely dependent on each other for expression and function. In pancreatic ß-cells, channels comprising SUR1 and Kir6.2 mediate glucose-stimulated insulin secretion and are the targets of antidiabetic sulfonylureas. Mutations in genes encoding SUR1 or Kir6.2 are linked to insulin secretion disorders, with loss- or gain-of-function mutations causing congenital hyperinsulinism or neonatal diabetes mellitus, respectively. Defects in the KATP channel in other tissues underlie human diseases of the cardiovascular and nervous systems. Key to understanding how channels are regulated by physiological and pharmacological ligands and how mutations disrupt channel assembly or gating to cause disease is the ability to observe structural changes associated with subunit interactions and ligand binding. While recent advances in the structural method of single-particle cryo-electron microscopy (cryoEM) offers direct visualization of channel structures, success of obtaining high-resolution structures is dependent on highly concentrated, homogeneous KATP channel particles. In this chapter, we describe a method for expressing KATP channels in mammalian cell culture, solubilizing the channel in detergent micelles and purifying KATP channels using an affinity tag to the SURx subunit for cryoEM structural studies.