Neuropathology in tauopathies stem from depolarization-induced alterations in the planar distribution of phosphoinositides

tau蛋白病的神经病理学源于去极化引起的磷酸肌醇平面分布的改变

• 批准号: 10055299
• 负责人: KARTIK VENKATACHALAM
• 金额: $ 178.83万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCI CTR HOUSTON
• 依托单位国家: 美国
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10055299
• 关键词: Acyltransferase; Alzheimer' s Disease; Alzheimer' s disease related dementia; Animals; Attenuated; Autophagocytosis; C9ORF72; Cell membrane; Cells; Chronic; Coupled; Coupling; Data; Data Set; Development; Drosophila genus; Electrophysiology (science); Enzymes; Epigenetic Process; Estrogen receptor positive; Event; Eye; Functional disorder; Genes; Genetic Transcription; Glutamates; Hydrolysis; Inositol; Lead; Lipids; Longevity; Mediating; Membrane Potentials; Modeling; Mus; Mutation; Nerve Degeneration; Neurofibrillary Tangles; Neuronal Dysfunction; Neurons; Outcome; Pathologic; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols; Phospholipase; Population; Potassium Channel; Process; Production; Proteins; RNA analysis; Receptor Activation; Receptor Signaling; Regulation; Rest; Second Messenger Systems; Side; Signal Transduction; Tauopathies; Technology; Testing; Toxic effect; Transgenes; attenuation; base; causal variant; fly; gene repression; insight; knock-down; mitochondrial dysfunction; multidisciplinary; neuroinflammation; neuron loss; neuropathology; neurotoxicity; novel; preference; premature; prevent; receptor; restoration; stem; tau Proteins; tau aggregation; tau mutation; therapeutic target; transcriptome sequencing

Tau tangles are common features of Alzheimer’s disease related dementias (ADRDs) and induce a range of pathological perturbations in neurons including hyperexcitability and Ca2+ dyshomeostasis. In this application, we use Drosophila to demonstrate that progressive neurotoxicity elicited by Tau or hexanucleotide repeat expansion of C9ORF72 involves elevated production of the second messenger, inositol trisphosphate (IP3), and activation of IP3 receptor (IP3R)-mediated ER Ca2+ release. Thus, premature lethality stemming from expression of ADRD-causing transgenes was almost fully suppressed by attenuation of IP3 production or knockdown IP3Rs. Although IP3Rs have been previously implicated in neurodegeneration, we have uncovered a novel mechanism underlying channel hyperactivation. We show expression of ADRD-causing transgenes leads to loss of neuronal membrane potential, and that the resulting depolarization is what increases IP3R activity. Our preliminary findings are consistent with the notion that depolarization increases association of an enzyme responsible for IP3 production, phospholipase Cb (PLCb), with its phosphoinositide substrate, PIP2. Greater PLCb–PIP2 interactions in depolarized cells lead to elevated IP3 production upon stimulation of PLCb-coupled receptors. In Aim 1, we will test the aforementioned hypothesis in fly and mouse neurons expressing mutant tau. We also ask how ADRD neurons lose their ability to maintain membrane potential. Based on electrophysiological recordings and analyses of RNA-seq datasets, we hypothesize that chronic depolarization stems from diminished abundance of neuronal K+ leak channels that are needed for establishing normal resting membrane potential. In Aim 2, we seek to determine how depolarization potentiates PLCb–IP3R signaling. Our findings suggest that membrane potential dependent regulation of PLCb—PIP2 association and hydrolysis depend on the lipids’ acyl side chains. Taken in conjunction with our findings that depolarization promotes IP3 production, we hypothesize that PLCb activity depends on PIP2 side chain identity, and increases in depolarized cells due to the preferential hydrolysis of species with longer and more unsaturated side chains. Successful completion of the proposed studies would demonstrate that IP3R hyperactivation in ADRD neurons is agnostic to the causal mutations — an insight that speaks to the wide applicability of our findings. We also hope to develop strategies that can be leveraged to selectively change the population of PIP2 species at the plasma membrane in order to correct pathological Ca2+ dyshomeostasis that occurs in ADRD.

Tau 蛋白缠结是阿尔茨海默病相关痴呆 (ADRD) 的常见特征，可诱发一系列症状 神经元的病理扰动，包括过度兴奋和 Ca2+ 稳态失调。 我们使用果蝇来证明 Tau 或六核苷酸重复引起的进行性神经毒性 C9ORF72 的扩增涉及第二信使三磷酸肌醇 (IP3) 的产生增加， IP3 受体 (IP3R) 介导的 ER Ca2+ 释放的激活因此，表达导致过早致死。 导致 ADRD 的转基因几乎完全被 IP3 产生减弱或敲低 IP3R 所抑制。 尽管 IP3R 之前被认为与神经退行性疾病有关，但我们发现了一种新机制 我们发现引起 ADRD 的转基因表达会导致神经元损失。 膜电位，以及由此产生的去极化是增加 IP3R 活性的原因。 与去极化增加与 IP3 相关的酶的关联的观点一致 生产磷脂酶 Cb (PLCb) 及其磷酸肌醇底物 PIP2 更大的 PLCb-PIP2 相互作用。 在去极化细胞中，刺激 PLCb 偶联受体后会导致 IP3 产生升高。在目标 1 中，我们。 我们将在表达突变 tau 的果蝇和小鼠神经元中测试上述假设。 根据电生理记录和分析，神经元失去了维持膜电位的能力。 在 RNA-seq 数据集的研究中，我们勇敢地承认，慢性去极化源于神经元丰度的减少 在目标 2 中，我们寻求建立正常静息膜电位所需的 K+ 泄漏通道。 确定去极化如何增强 PLCb-IP3R 信号传导 我们的研究结果表明膜电位。 PLCb-PIP2 结合和水解的依赖性调节取决于脂质的酰基侧链。 结合我们的发现，即去极化促进 IP3 的产生，我们捕获了 PLCb 活动 取决于 PIP2 侧链特性，并且由于优先水解而导致去极化细胞增加 具有更长和更多不饱和侧链的物种将成功完成拟议的研究。 证明 ADRD 神经元中的 IP3R 过度激活与因果突变无关——这一见解 我们还希望制定可用于以下方面的战略。 选择性地改变质膜上 PIP2 的数量，以纠正病理性 Ca2+ ADRD 中发生的体内平衡失调。