Structural insights into the mechanism of nucleotide regulation of pancreatic KATP channel

2021 ◽  
Author(s):  
Mengmeng Wang ◽  
Jing-Xiang Wu ◽  
Dian Ding ◽  
Xinli Duan ◽  
Songling Ma ◽  
...  
Keyword(s):  
Potassium Channels ◽  
Katp Channel ◽  
Katp Channels ◽  
Activation Mechanism ◽  
Fundamental Properties ◽  
Closed State ◽  
Physiological Processes ◽  
Nucleotide Regulation ◽  
Atp Inhibition ◽  
Structural Insights

ATP-sensitive potassium channels (KATP) are metabolic sensors that convert the intracellular ATP/ADP ratio to the excitability of cells. They are involved in many physiological processes and implicated in several human diseases. Here we present the cryo-EM structures of the pancreatic KATP channel in both the closed state and the pre-open state, resolved in the same sample. The nucleotides bind at the inhibitory sites of the Kir6.2 channel in the closed state but not in the pre-open state. Structural comparisons reveal the mechanism for ATP inhibition and Mg-ADP activation, two fundamental properties of KATP channels. Moreover, the structure also uncovers the activation mechanism of diazoxide-type KATP openers.

ATP-sensitive potassium channel subunits in the neuroinflammation: novel drug targets in neurodegenerative disorders

2021 ◽  
Vol 20 ◽  
Author(s):  
Fatima Maqoud ◽  
Rosa Scala ◽  
Malvina Hoxha ◽  
Bruno Zappacosta ◽  
Domenico Tricarico
Keyword(s):  
Potassium Channels ◽  
Neurodegenerative Disorders ◽  
Katp Channel ◽  
Pancreatic Beta Cells ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Amyloid Β ◽  
Katp Channels ◽  
Innovative Strategy ◽  
Arachidonic Acids

: 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, is 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 is 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.

Role of Adenosine Triphosphate-sensitive Potassium Channels in Coronary Vasodilation by Halothane, Isoflurane, and Enflurane

1997 ◽  
Vol 86 (2) ◽  
pp. 448-458 ◽  
Author(s):  
George J. Crystal ◽  
Juozas Gurevicius ◽  
Ramez M. Salem ◽  
Xiping Zhou
Keyword(s):  
Potassium Channels ◽  
Adenosine Triphosphate ◽  
Katp Channel ◽  
Katp Channels ◽  
Volatile Anesthetics ◽  
Coronary Vasodilation ◽  
Flow Transducer ◽  
Cardiac Depression ◽  
Arterial Blood

Background Halothane, isoflurane, and enflurane cause coronary vasodilation and cardiac depression. This study was performed to assess the role of adenosine triphosphate (ATP)-sensitive potassium channels (KATP channels) in these effects. Methods Twenty-five thoracotomized dogs were anesthetized with fentanyl and midazolam. The left anterior descending coronary artery was perfused via either of two pressurized (80 mmHg) reservoirs. One reservoir was supplied with arterial blood free of a volatile anesthetic, and the second reservoir was supplied with arterial blood equilibrated in an oxygenator with a 1 minimum alveolar concentration of either halothane (0.9%, n = 10), isoflurane (1.4%, n = 8), or enflurane (2.2%, n = 7). Coronary blood flow (CBF) was measured using a Doppler flow transducer, and segmental shortening (SS) was measured with ultrasonic crystals. Responses to the volatile anesthetics were assessed under control conditions, during intracoronary infusion of the KATP channel inhibitor glibenclamide (100 micrograms/min), and after cessation of glibenclamide (recovery). The effectiveness of glibenclamide was verified from inhibition of coronary vasodilator responses to the KATP channel opener cromakalim without effect on those to the KATP channel-independent vasodilators, sodium nitroprusside and acetylcholine. Results Under control conditions, the volatile anesthetics caused pronounced increases in CBF (isoflurane > halothane = enflurane), and decreases in SS (enflurane > halothane = isoflurane). Glibenclamide blunted significantly (and reversibly) the increases in CBF, but it had no effect on the decreases in SS. Conclusions The KATP channels play an important role in coronary vasodilation but apparently are not involved in cardiac depression caused by halothane, isoflurane, and enflurane in canine hearts in situ.

scholarly journals Regulation of KATP Channel Activity by Diazoxide and MgADP

1997 ◽  
Vol 110 (6) ◽  
pp. 643-654 ◽  
Author(s):  
S.-L. Shyng ◽  
T. Ferrigni ◽  
C.G. Nichols
Keyword(s):  
Katp Channel ◽  
Katp Channels ◽  
Nucleotide Binding ◽  
Sulfonylurea Receptor ◽  
Channel Activity ◽  
Nucleotide Hydrolysis ◽  
Inward Rectifier Potassium Channel ◽  
Hydrolysis Rates ◽  
Atp Inhibition

KATP channels were reconstituted in COSm6 cells by coexpression of the sulfonylurea receptor SUR1 and the inward rectifier potassium channel Kir6.2. The role of the two nucleotide binding folds of SUR1 in regulation of KATP channel activity by nucleotides and diazoxide was investigated. Mutations in the linker region and the Walker B motif (Walker, J.E., M.J. Saraste, M.J. Runswick, and N.J. Gay. 1982. EMBO [Eur. Mol. Biol. Organ.] J. 1:945–951) of the second nucleotide binding fold, including G1479D, G1479R, G1485D, G1485R, Q1486H, and D1506A, all abolished stimulation by MgADP and diazoxide, with the exception of G1479R, which showed a small stimulatory response to diazoxide. Analogous mutations in the first nucleotide binding fold, including G827D, G827R, and Q834H, were still stimulated by diazoxide and MgADP, but with altered kinetics compared with the wild-type channel. None of the mutations altered the sensitivity of the channel to inhibition by ATP4−. We propose a model in which SUR1 sensitizes the KATP channel to ATP inhibition, and nucleotide hydrolysis at the nucleotide binding folds blocks this effect. MgADP and diazoxide are proposed to stabilize this desensitized state of the channel, and mutations at the nucleotide binding folds alter the response of channels to MgADP and diazoxide by altering nucleotide hydrolysis rates or the coupling of hydrolysis to channel activation.

scholarly journals Insulin Regulates Islet α-Cell Function by Reducing KATP Channel Sensitivity to Adenosine 5′-Triphosphate Inhibition

Endocrinology ◽  
2006 ◽  
Vol 147 (5) ◽  
pp. 2155-2162 ◽  
Author(s):  
Yuk M. Leung ◽  
Ishtiaq Ahmed ◽  
Laura Sheu ◽  
Xiaodong Gao ◽  
Manami Hara ◽  
...  
Keyword(s):  
Katp Channel ◽  
Cell Function ◽  
Fluorescent Protein ◽  
Glucagon Secretion ◽  
Katp Channels ◽  
Β Cell ◽  
Major Mechanism ◽  
Insulin Promoter ◽  
Atp Inhibition ◽  
Green Fluorescent

Glucose regulates pancreatic islet α-cell glucagon secretion directly by its metabolism to generate ATP in α-cells, and indirectly via stimulation of paracrine release of β-cell secretory products, particularly insulin. How the cellular substrates of these pathways converge in the α-cell is not well known. We recently reported the use of the MIP-GFP (mouse insulin promoter-green fluorescent protein) mouse to reliably identify islet α- (non-green cells) and β-cells (green cells), and characterized their ATP-sensitive K+ (KATP) channel properties, showing that α-cell KATP channels exhibited a 5-fold higher sensitivity to ATP inhibition than β-cell KATP channels. Here, we show that insulin exerted paracrine regulation of α-cells by markedly reducing the sensitivity of α-cell KATP channels to ATP (IC50 = 0.18 and 0.50 mm in absence and presence of insulin, respectively). Insulin also desensitized β-cell KATP channels to ATP inhibition (IC50 = 0.84 and 1.23 mm in absence and presence of insulin, respectively). Insulin effects on both islet cell KATP channels were blocked by wortmannin, indicating that insulin acted on the insulin receptor-phosphatidylinositol 3-kinase signaling pathway. Insulin did not affect α-cell A-type K+ currents. Glutamate, known to also inhibit α-cell glucagon secretion, did not activate α-cell KATP channel opening. We conclude that a major mechanism by which insulin exerts paracrine control on α-cells is by modulating its KATP channel sensitivity to ATP block. This may be an underlying basis for the proposed sequential glucose-insulin regulation of α-cell glucagon secretion, which becomes distorted in diabetes, leading to dysregulated glucagon secretion.

scholarly journals Molecular structure of human KATP in complex with ATP and ADP

2017 ◽  
Author(s):  
Kenneth Pak Kin Lee ◽  
Jue Chen ◽  
Roderick MacKinnon
Keyword(s):  
Katp Channel ◽  
Regulatory Element ◽  
Katp Channels ◽  
Inward Rectifier ◽  
Excitable Cells ◽  
Binding Domains ◽  
Inhibitory Site ◽  
Atp Inhibition ◽  
Adenosine Nucleotides

ABSTRACTIn many excitable cells KATP channels respond to intracellular adenosine nucleotides: ATP inhibits while ADP activates. We present two structures of the human pancreatic KATP channel, containing the ABC transporter SUR1 and the inward-rectifier K+ channel Kir6.2, in the presence of Mg2+ and nucleotides. These structures, referred to as quatrefoil and propeller forms, were determined by single-particle cryo-EM at 3.9 Å and 5.6 Å, respectively. In both forms ATP occupies the inhibitory site in Kir6.2. The nucleotide-binding domains of SUR1 are dimerized with Mg2+-ATP in the degenerate site and Mg2+-ADP in the consensus site. A lasso extension forms an interface between SUR1 and Kir6.2 adjacent to the ATP site in the propeller form, and is disrupted in the quatrefoil form. These structures support the role of SUR1 as an ADP sensor and highlight the lasso extension as a key regulatory element in ADP’s ability to override ATP inhibition.

scholarly journals The dynamic interplay of PIP2 and ATP in the regulation of the KATP channel

2021 ◽  
Author(s):  
Tanadet Pipatpolkai ◽  
Samuel Usher ◽  
Natascia Vedovato ◽  
Frances Ashcroft ◽  
Phillip Stansfeld
Keyword(s):  
Katp Channel ◽  
Md Simulation ◽  
Neonatal Diabetes ◽  
Katp Channels ◽  
Single Amino Acid ◽  
Channel Activity ◽  
Single Amino Acid Residue ◽  
Binding Pockets ◽  
Atp Inhibition ◽  
Dynamic Interplay

Abstract ATP-sensitive potassium (KATP) channels couple the intracellular ATP concentration to insulin secretion. KATP channel activity is inhibited by ATP binding to the Kir6.2 tetramer and activated by phosphatidylinositol-4,5-bisphosphate (PIP2). Here, we use molecular dynamics (MD) simulation, electrophysiology and fluorescence spectroscopy to show that ATP and PIP2 occupy different binding pockets that share a single amino acid residue, K39. When both ligands are present, K39 shows a greater preference to co-ordinate with PIP2 than ATP. A neonatal diabetes mutation at K39 (K39R) increases the number of hydrogen bonds formed between K39 and PIP2, reducing ATP inhibition. We also find direct effects on nucleotide binding from mutating E179, a residue proposed to interact with PIP2. Our work suggests PIP2 and ATP interact allosterically to regulate KATP channel activity.

Central KATP channels modulate glucose effectiveness in humans and rodents

2020 ◽  
Author(s):  
Ada Admin ◽  
Michelle Carey ◽  
Eric Lontchi-Yimagou ◽  
William Mitchell ◽  
Sarah Reda ◽  
...  
Keyword(s):  
Katp Channel ◽  
Glucose Production ◽  
Katp Channels ◽  
Endogenous Glucose Production ◽  
Elevated Plasma ◽  
Sprague Dawley ◽  
Glucose Effectiveness ◽  
Sprague Dawley Rats ◽  
The Central Nervous System

Hyperglycemia is a potent regulator of endogenous glucose production (EGP). Loss of this ‘glucose effectiveness’ is a major contributor to elevated plasma glucose concentrations in type 2 diabetes (T2D). ATP-sensitive potassium channels (K<sub>ATP</sub> channels) in the central nervous system (CNS) have been shown to regulate EGP in humans and rodents. We examined the contribution of central K<sub>ATP</sub> channels to glucose effectiveness. Under fixed hormonal conditions (‘pancreatic clamp’ studies), hyperglycemia suppressed EGP by ~50% in both non-diabetic humans and normal Sprague Dawley rats. By contrast, antagonism of K<sub>ATP</sub> channels with glyburide significantly reduced the EGP-lowering effect of hyperglycemia in both humans and rats. Furthermore, the effects of glyburide on EGP and gluconeogenic enzymes in rats were abolished by intracerebroventricular (ICV) administration of the KATP channel agonist diazoxide. These findings indicate that about half of EGP suppression by hyperglycemia is mediated by central K<sub>ATP</sub> channels. These central mechanisms may offer a novel therapeutic target for improving glycemic control in T2D.

Regulation of ATP-sensitive K+ channels by ATP and nucleotide diphosphate in rabbit portal vein

1994 ◽  
Vol 266 (5) ◽  
pp. H1687-H1698 ◽  
Author(s):  
M. Kamouchi ◽  
K. Kitamura
Keyword(s):  
Portal Vein ◽  
Katp Channel ◽  
Single Channel ◽  
Katp Channels ◽  
K Channel ◽  
Channel Activity ◽  
Rabbit Portal Vein ◽  
Internal Side ◽  
The Right ◽  
Single Channel Currents

The modulation of ATP-sensitive K+ (KATP)-channel activity was investigated by recording single-channel currents in isolated smooth muscle cells from rabbit portal vein. K(+)-channel openers (KCOs; pinacidil, lemakalim, and nicorandil) induced burstlike openings of single KATP channels in the cell-attached configuration. After patch excision, KATP channels showed "run-down" phenomenon in the presence of KCOs, but subsequent application of Mg-ATP (1 mM) restored KATP-channel activity. Removal of Mg-ATP resulted in transient augmentation of KATP currents, which eventually decayed out. Nucleotide diphosphates (NDPs; GDP, ADP, UDP, IDP, and CDP) also induced channel reopening in the presence of KCOs, which was markedly enhanced by addition of Mg2+ in millimolar concentrations at the internal side of the membrane. The dose-response relation between ATP and the UDP-induced KATP-channel activity was shifted to the right in the presence of Mg2+ (2 mM). These results suggest that intracellular ATP, NDPs, and Mg2+ regulate the channel state of KATP channels (operative and inoperative states) and that KCOs open KATP channels only in the operative state.

scholarly journals Distinct subunit contributions to the activation of M-type potassium channels by PI(4,5)P2

2012 ◽  
Vol 140 (1) ◽  
pp. 41-53 ◽  
Author(s):  
Vsevolod Telezhkin ◽  
David A. Brown ◽  
Alasdair J. Gibb
Keyword(s):  
Potassium Channels ◽  
Single Channel ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Water Soluble ◽  
Activation Mechanism ◽  
Quantitative Relation ◽  
Open Probability ◽  
Activation Curve ◽  
M Channels

Low-threshold voltage-gated M-type potassium channels (M channels) are tetraheteromers, commonly of two Kv7.2 and two Kv7.3 subunits. Though gated by voltage, the channels have an absolute requirement for binding of the membrane phospholipid phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) to open. We have investigated the quantitative relation between the concentration of a water-soluble PI(4,5)P2 analog, dioctanoyl-PI(4,5)P2 (DiC8-PI(4,5)P2), and channel open probability (Popen) by fast application of increasing concentrations of DiC8-PI(4,5)P2 to the inside face of membrane patches excised from Chinese hamster ovary cells expressing M channels as heteromeric Kv7.2/7.3 subunits. The rationale for the experiments is that this will mimic the effect of changes in membrane PI(4,5)P2 concentration. Single-channel conductances from channel current–voltage relations in cell-attached mode were 9.2 ± 0.1 pS with a 2.5-mM pipette [K+]. Plots of Popen against DiC8-PI(4,5)P2 concentration were best fitted using a two-component concentration–Popen relationship with high and low affinity, half-maximal effective concentration (EC50) values of 1.3 ± 0.14 and 75.5 ± 2.5 µM, respectively, and Hill slopes of 1.4 ± 0.06. In contrast, homomeric channels from cells expressing only Kv7.2 or Kv7.3 constructs yielded single-component curves with EC50 values of 76.2 ± 19.9 or 3.6 ± 1.0 µM, respectively. When wild-type (WT) Kv7.2 was coexpressed with a mutated Kv7.3 subunit with &gt;100-fold reduced sensitivity to PI(4,5)P2, the high-affinity component of the activation curve was lost. Fitting the data for WT and mutant channels to an activation mechanism with independent PI(4,5)P2 binding to two Kv7.2 and two Kv7.3 subunits suggests that the two components of the M-channel activation curve correspond to the interaction of PI(4,5)P2 with the Kv7.3 and Kv7.2 subunits, respectively, that channels can open when only the two Kv7.3 subunits have bound DiC8-PI(4,5)P2, and that maximum channel opening requires binding to all four subunits.

Blockade of Adenosine Triphosphate–sensitive Potassium Channels by Thiamylal in Rat Ventricular Myocytes

2000 ◽  
Vol 92 (4) ◽  
pp. 1154-1159 ◽  
Author(s):  
Yasuo Tsutsumi ◽  
Shuzo Oshita ◽  
Hiroshi Kitahata ◽  
Yasuhiro Kuroda ◽  
Takashi Kawano ◽  
...  
Keyword(s):  
Adenosine Triphosphate ◽  
Katp Channel ◽  
Single Channel ◽  
Ventricular Myocytes ◽  
Katp Channels ◽  
Dependent Manner ◽  
Open Probability ◽  
Rat Ventricular Myocytes ◽  
Inside Out ◽  
Cell Attached Configuration

Background The adenosine triphosphate (ATP)-sensitive potassium (KATP) channels protect myocytes during ischemia and reperfusion. This study investigated the effects of thiamylal on the activities of KATP channels in isolated rat ventricular myocytes during simulated ischemia. Methods Male Wistar rats were anesthetized with ether. Single, quiescent ventricular myocytes were dispersed enzymatically. Membrane currents were recorded using patch-clamp techniques. In the cell-attached configuration, KATP channel currents were assessed before and during activation of these channels by 2,4-dinitrophenol and after administration of 25, 50, and 100 mg/l thiamylal. The open probability was determined from current-amplitude histograms. In the inside-out configuration, the current-voltage relation was obtained before and after the application of thiamylal (50 mg/1). Results In the cell-attached configuration, 2,4-dinitrophenol caused frequent channel opening. 2,4-Dinitrophenol-induced channel activities were reduced significantly by glibenclamide, suggesting that the channels studied were KATP channels. Open probability of KATP channels was reduced by thiamylal in a concentration-dependent manner. KATP channels could be activated in the inside-out configuration because of the absence of ATP. Thiamylal inhibited KATP channel activity without changing the single-channel conductance. Conclusions The results obtained in this study indicate that thiamylal inhibits KATP channel activities in cell-attached and inside-out patches, suggesting a direct action of this drug on these channels.

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