Challenging the Dominant Model for ATP Regulation of KATP Channels

挑战 KATP 通道 ATP 调节的主导模型

基本信息

批准号：
9199412
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
项目类别：
财政年份：
2014
资助国家：
美国
起止时间：
2014-01-01 至 2018-12-31
项目状态：
已结题

来源：
https://reporter.nih.gov/project-details/9199412
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 Electrophysiology (science)Equilibrium Genes Genetic Polymorphism Goals Hormones Hydrolysis Hyperactive behavior Hyperinsulinism Hypoglycemic Agents Islets of Langerhans Laboratories Membrane Potentials Metabolic Metabolic Control Metabolism MgADP Modeling Molecular Conformation Mutation Neonatal Neurons Neurosecretory Systems Non-Insulin-Dependent Diabetes Mellitus Nucleotides Orthovanadate Pancreas Pathologic Patients Persistent Hyperinsulinemia Hypoglycemia of Infancy Pharmacology Physiological Play Potassium Channel Potassium Channel Binding Predictive Value Property Proteins Regulation Reporting Research Risk Secondary to Structural Models Sulfonylurea Compounds Testing Time Vanadates Variant Work analog base blood glucose regulation clinical phenotype cofactor diabetes risk dimer enzyme substrate glucose metabolism inorganic phosphate insight insulin secretion mutant neonatal diabetes mellitus novel patch clamp prevent programs public health relevance receptor

项目摘要

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（由适用提供）：该计划的长期目标是了解对ATP敏感的K+，KATP，腺嘌呤核苷酸的调节；短期目标是挑战现行的监管模型。胰腺中的腺嘌呤核苷酸，ATP和ADP的水平随葡萄糖代谢率而变化。 KATP通道应对这些变化，是血糖对胰岛素分泌的正常控制的关键参与者。这些通道是用于治疗2型糖尿病的磺酰氟脲的靶标。 ABCC8/SUR1或KCNJ11/KIR6.2通道成分中的突变是新生儿糖尿病（ND）和新生儿高胰岛素（HI）的原因，而两个亚基的多态性会导致2型2型糖尿病的风险增加。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SUR1时的ATP水解来抵消或拮抗ATP对KIR6.2孔的抑制作用。过度活跃的SUR1通过“过度活化” Kir6.2孔产生ND。 SUR1 ATPase活性的改变是为了基础过度激活和ABCC8多态性所指出的风险增加。我们实验室的最新研究挑战了现行模型（Ortiz等，JBC，2012年）。这项研究使用了没有相关的Kir6.2的两个ND突变Surs来定义ATP和磺酰尿素结合之间与SUR1构象变化之间的变构关系。我们确定ATP水解对于将SUR1切换为刺激会议并不是必不可少的，并提出对ATP的亲和力增加是疾病的根本原因。现在已经扩展了这项研究，以表明SUR1对ATP的亲和力与临床表型之间存在直接关系。与新生儿糖尿病相关的SUR比正常亲和力大于正常亲和力，具有较低亲和力的新生儿糖尿病与先天性高胰岛素相关。 ATP与SUR1相互作用之间的负变构关系是已知的更高剂量的磺酰氟脲的需求，以实现ND患者的代谢控制。提出的工作将使用药理学和电生理学研究将分析扩展到完整的通道，以对其他ND SUR1突变体，多态性以及具有抑制ATPase活性的替代的SUR进行。先前关于ATP类似物对KATP通道函数的作用的研究用于支持现行模型，因此提出了其他工作来定义其对SUR1构象切换的作用。该项目的总体目的是开发修改主要模型所需的数据，以便它可以充分解释在正常生理条件下对KATP通道的调节，并具有预测价值，以了解突变，尤其是ABCC8突变如何影响通道功能。