BK Channel B4 Subunit in the Dentate Gyrus and Seizures

齿状回中的 BK 通道 B4 亚基和癫痫发作

• 批准号: 7577457
• 负责人: ROBERT BRENNER
• 金额: $ 25.55万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCIENCE CENTER
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-04-01 至 2012-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7577457
• 关键词: Action Potentials; Affect; Agonist; Animal Model; Antibodies; Apamin; Calcium; Cells; Cyclic AMP; Data; Defect; Disease; Down-Regulation; Drug Design; Electroencephalography; Epilepsy; Exhibits; Feeds; Focal Seizure; Frequencies; Genes; Genetic; Genetic Models; Hippocampus (Brain); Human; Immunohistochemistry; Investigation; Ion Channel; Kinetics; Knock-out; Knockout Mice; Measurement; Mediating; Membrane; Metabotropic Glutamate Receptors; Mus; Mutation; Nature; Nerve; Neurons; Output; Pharmaceutical Preparations; Phosphorylation; Potassium; Potassium Channel; Probability; Property; Proteins; Receptor Signaling; Recruitment Activity; Regulation; Research Personnel; Resistance; Role; Seizures; Signal Transduction; Slice; Synaptic Transmission; Techniques; Temporal Lobe; Temporal Lobe Epilepsy; Testing; Work; base; dentate gyrus; design; gain of function; hypertension control; iberiotoxin; interest; large-conductance calcium-activated potassium channels; metabotropic glutamate receptor 3; mossy fiber; neuronal cell body; neurotransmission; novel; patch clamp; paxilline; programs; protein kinase A kinase; research study; voltage

DESCRIPTION (provided by applicant): Potassium channels have the role of reducing excitability and are pivotal in controlling seizures. The large conductance calcium-activated potassium channels (BK-type channels) have the specialized role of regulating membrane excitability that is coincident with calcium influx. Previously, heterologous co- expression of the pore-forming a subunit with the novel ¿4 accessory subunit was found to produce BK currents with properties of so called neuronal "type II BK channels". The ¿4 subunit confers resistance to iberiotoxin block, slow gating kinetics, and a reduced open probability. In addition, the ¿4 subunit may confer sensitivity to pKA dependent phosphorylation in neurons. We have generated ¿4 gene knockout mice. Our preliminary data provides direct evidence that BK channel assembly with the ¿4 subunit underlies type II BK channels. In the dentate gyrus (DG), knockout cells are more excitable and support high frequency firing. Finally, EEG recording demonstrate that the ¿4 knockout mice exhibit non-convulsive partial seizures. The ¿4 knockout mice may be the first genetic model for non-convulsive temporal lobe epilepsy. Investigation of these mice will allow us the unique opportunity to have a biophysical understanding of the changes in ion channel properties that may underlie this class of epilepsy. Our interest is to understand how a/¿4 subunit BK channels regulate the input/output properties of DG cells, and thereby contribute to resistance of synchronized epileptiform activity that is a property of the DG. Our working hypothesis is that beta4 subunits down-regulates BK channels, resulting in increased calcium influx and reduced excitability by recruitment of SK channels. We have 3 aims. 1) Utilizing patch clamp/slice recordings from DG cells, understand the change in membrane properties that result in increased AP firing in the knockout mice. 2) Determine how the (¿4 subunit modulates sensitivity of BK channels to pKA dependent phosphorylation in the DG, and thereby regulates excitability by metabotropic glutamate receptors 3) Utilize immunohistochemistry and electrophysiological recording techniques to determine the subcellular localization of the ¿4 subunit in nerve terminals and its' contribution to neurotransmission in the mossy fiber terminals. These studies will provide the first understanding of a relatively uncharacterized BK channel subtype and further our understanding of this channels' function in the context of a novel genetic model for epilepsy.

描述（由申请人提供）：钾通道具有降低兴奋性的作用，在控制癫痫发作中起关键作用。大电导钙活化钾通道（bk型通道）具有调节膜兴奋性的特殊作用，与钙内流相一致。在此之前，研究人员发现，形成孔的亚基与新的辅助性亚基的异源共表达可以产生具有所谓神经元“II型BK通道”特性的BK电流。¿4亚基赋予对iberitoxin block的抗性，缓慢的门控动力学和降低的打开概率。此外，¿4亚基可能赋予神经元对pKA依赖性磷酸化的敏感性。