Challenging the Dominant Model for ATP Regulation of KATP Channels

挑战 KATP 通道 ATP 调节的主导模型

• 批准号: 8788349
• 负责人: Joseph Bryan
• 金额: $ 36.12万
• 依托单位: PACIFIC NORTHWEST RESEARCH INSTITUTE
• 依托单位国家: 美国
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8788349
• 关键词: ATP Hydrolysis; ATP phosphohydrolase; Address; Adenine Nucleotides; Adenylyl Imidodiphosphate; Affect; Affinity; Agonist; Binding; Biological Assay; Blood Glucose; CRSP3 gene; Cells; Consensus; Coupling; Data; Diabetes Mellitus; Diazoxide; Dimerization; Disease; Dose; Drug usage; Equilibrium; Genes; Genetic Polymorphism; Goals; Health; Hormones; Hydrolysis; Hyperactive behavior; Hyperinsulinism; Hypoglycemic Agents; Islets of Langerhans; Kir6.2 channel; Laboratories; Membrane Potentials; Metabolic Control; Metabolism; MgADP; Modeling; Molecular Conformation; Mutation; Neonatal; Neurons; Neurosecretory Systems; Non-Insulin-Dependent Diabetes Mellitus; Nucleotides; Pancreas; Pathologic; Patients; Persistent Hyperinsulinemia Hypoglycemia of Infancy; Physiological; Play; Potassium Channel; Potassium Channel Binding; Predictive Value; Property; Proteins; Regulation; Reporting; Research; Risk; S cerevisiae SWI3 protein; Secondary to; Structural Models; Sulfonylurea Compounds; Testing; Time; Vanadates; Variant; Work; analog; base; blood glucose regulation; clinical phenotype; cofactor; diabetes risk; enzyme substrate; glucose metabolism; inorganic phosphate; insight; insulin secretion; mutant; neonatal diabetes mellitus; novel; patch clamp; prevent; programs; receptor

DESCRIPTION (provided by applicant): The long-term objective of this program is to understand the regulation of ATP-sensitive K+, KATP, channels by adenine nucleotides; the short-term goal is to challenge the prevailing regulatory model. The levels of adenine nucleotides, ATP and ADP, in pancreatic ¿-cells vary with the rate of glucose metabolism. KATP channels respond to these variations and are key players in the normal control of insulin secretion by blood glucose. These channels are the targets for sulfonylureas, hypoglycemic drugs used to treat type 2 diabetes. Mutations in the ABCC8/SUR1 or KCNJ11/Kir6.2 channel components are causes of neonatal diabetes (ND) and neonatal hyperinsulinism (HI) while polymorphisms in both subunits confer increased risk for type 2 diabetes. The prevailing regulatory hypothesis, used to interpret how mutations and polymorphisms alter channel activity, is that ATP hydrolysis at SUR1 is required to counteract or antagonize the inhibitory action of ATP on the Kir6.2 pore. Thus an overactive SUR1 produces ND by 'hyperactivating' the Kir6.2 pore. Altered SUR1 ATPase activity is proposed to underlie hyperactivation and the increased risk posed by ABCC8 polymorphisms. A recent study from our laboratory challenges the prevailing model (Ortiz et al, JBC, 2012). This study used two ND mutant SURs, without an associated Kir6.2, to define the allosteric relations between ATP and sulfonylurea binding with changes in SUR1 conformation. We established that ATP hydrolysis is not essential to switch SUR1 into a stimulatory conformation and proposed that an increased affinity for ATP is the underlying cause of the disorder. This study has now been extended to show there is a direct relation between the affinity of SUR1 for ATP and clinical phenotype; SURs with greater than normal affinity for ATP correlate with neonatal diabetes, those with lower affinity correlate with congenital hyperinsulinism. The negative allosteric relation between ATP and sulfonylurea interactions with SUR1 underlies the known need for higher doses of sulfonylureas to achieve metabolic control in ND patients. The proposed work will extend the analysis to full channels using pharmacologic and electrophysiologic studies on additional ND SUR1 mutants, polymorphisms, and on SURs with substitutions that inhibit ATPase activity. Previous studies on the action of ATP analogs on KATP channel function are used to support the prevailing model, thus additional work is proposed to define their action on conformational switching of SUR1. The overall objective of the project is to develop the data required to modify the prevailing model so that it can adequately explain regulation of KATP channels under normal physiologic conditions and has predictive value for understanding how mutations, particularly ABCC8 mutations, affect channel function.

描述（由申请人提供）：该计划的长期目标是了解腺嘌呤核苷酸对ATP敏感性K+（KATP）通道的调节;短期目标是挑战现行的调节模型。胰腺细胞中腺嘌呤核苷酸、ATP和ADP的水平随葡萄糖代谢速率而变化。KATP通道响应这些变化，并且是血糖对胰岛素分泌的正常控制中的关键参与者。这些通道是磺酰脲类药物的靶点，磺酰脲类药物是用于治疗2型糖尿病的降糖药物。ABCC 8/SUR 1或KCNJ 11/Kir6.2通道成分的突变是新生儿糖尿病（ND）和新生儿高胰岛素血症（HI）的原因，而这两个亚基的多态性增加了2型糖尿病的风险。用于解释突变和多态性如何改变通道活性的流行调节假说是，需要在SUR 1处的ATP水解来抵消或拮抗ATP对Kir6.2孔的抑制作用。因此，过度活跃的SUR 1通过“过度激活”Kir6.2孔产生ND。改变的SUR 1 ATP酶活性被认为是ABCC 8多态性引起的超活化和风险增加的基础。我们实验室最近的一项研究挑战了流行的模型（Ortiz等人，JBC，2012）。本研究使用了两个ND突变的SURs，没有相关的Kir6.2，定义ATP和磺酰脲类药物结合与SUR 1构象变化之间的变构关系。我们确定，ATP水解是不是必不可少的开关SUR 1到一个刺激的构象，并提出了一个增加的ATP亲和力是疾病的根本原因。这项研究现在已经扩展到显示SUR 1对ATP的亲和力与临床表型之间存在直接关系;对ATP亲和力大于正常的SURs与新生儿糖尿病相关，亲和力较低的SURs与先天性高胰岛素血症相关。ATP和磺酰脲类药物与SUR 1相互作用之间的负变构关系是已知需要更高剂量磺酰脲类药物以实现ND患者代谢控制的基础。拟议的工作将扩展到全通道的分析，使用药理学和电生理学研究额外的ND SUR 1突变体，多态性，并对SURs与取代，抑制ATP酶活性。以前的研究ATP类似物对KATP通道功能的作用被用来支持流行的模型，因此提出了额外的工作来定义它们对SUR 1构象转换的作用。该项目的总体目标是开发修改现行模型所需的数据，使其能够充分解释正常生理条件下KATP通道的调节，并对理解突变，特别是ABCC 8突变如何影响通道功能具有预测价值。