Mechanisms of cAMP signaling that drive spontaneous activity in nociceptors

驱动伤害感受器自发活动的 cAMP 信号传导机制

• 批准号: 10266146
• 负责人: Carmen W. Dessauer
• 金额: $ 43.1万
• 依托单位: UNIVERSITY OF TEXAS HLTH SCI CTR HOUSTON
• 依托单位国家: 美国
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-15 至 2025-07-31
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10266146
• 关键词: A kinase anchoring protein; Action Potentials; Acute; Address; Afferent Neurons; Animals; Biochemistry; C Fiber; Cell membrane; Cellular biology; Chronic; Complex; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Data; Drug Combinations; Drug Screening; Effectiveness; Electrophysiology (science); Exposure to; FDA approved; Funding; Goals; Hyperactivity; Image; Imaging Device; In Vitro; Injury; Joints; KRAS2 gene; Laboratories; Life; Link; Lipids; MAP Kinase Gene; Measures; Mediating; Membrane Lipids; Membrane Potentials; Microscopy; Modeling; Neuraxis; Neurons; Nociceptors; Opioid; Opioid Receptor; Pain; Pathway interactions; Peripheral; Persistent pain; Pharmaceutical Preparations; Phosphatidylserines; Phosphorylation; Phosphorylation Site; Proteins; RAS inhibition; Ras/Raf; Rattus; Reflex action; Refractory; Resistance; Rest; Role; Signal Transduction; Spinal Ganglia; Spinal cord injury; Spinal cord injury patients; Stimulus; Testing; base; cannabinoid receptor; chronic pain; drug testing; endogenous opioids; experimental study; in vivo; in vivo evaluation; neurotrophic factor; novel; painful neuropathy; recruit; response; scaffold; severe injury; spontaneous pain

Project Summary: Chronic pain caused by injury to the peripheral or central nervous system (neuropathic pain) is notoriously resistant to treatment, while the mechanisms that drive and/or maintain chronic pain remain unclear. We have shown that chronic nociceptor hyperexcitability after severe injury is maintained by cAMP signaling through multiple cAMP effectors, including PKA, EPAC and HCN channels. These pathways are enhanced by AKAP-mediated complex formation with AC and show significant cross-talk with Ras/MAPK signaling. Activation of cAMP- and Ras-mediated pathways initiate at the plasma membrane (PM) and are uniquely sensitive to clustering of lipids within the PM. We have also shown that spinal cord injury reduces AC inhibition by Gαi, resulting in reduced potency of opioids in DRG neurons. This reduced sensitivity can be mimicked in DRG neurons from naïve animals by overnight exposure to neurotrophic factors or by a 5 min, modest depolarization that approaches the firing threshold of DRG neurons after severe injury. Importantly, nociceptor hyperexcitability and reductions in opioid potency, induced by either injury, neurotrophic factors or acute depolarization, can be reversed by inhibition of Ras-dependent signaling or reorganization of lipids in the plasma membrane. We hypothesize that the sustained depolarization that occurs in many injury models drives alterations in PM lipid organization, leading to increased ERK signaling and decreased opioid responses. Release of neurotrophic factors reinforce these pathways and, in conjunction with cAMP signaling, drives nociceptor hyperexcitability and a chronic pain state. To address these hypotheses, we propose three Aims. 1) Determine the mechanism for reduced MOR-Gαi inhibition of AC by C-Raf, 2) Define the mechanism of Ras activation and nociceptor hyperexcitability by depolarization and SCI, and 3) Define functional consequences of interactions among depolarization and cell signaling by cAMP, C-Raf, and ERK. Importantly, our model identifies multiple FDA-approved drugs that could simultaneously enhance endogenous opioid responses and block nociceptor hyperexcitability after severe injury.

项目摘要： 由周围或中枢神经系统受伤引起的慢性疼痛（神经性疼痛）是 臭名昭著的治疗能力，而驱动和/或保持慢性疼痛的机制仍然存在 不清楚。我们已经表明，在严重伤害后的慢性伤害感受器过度兴奋。 通过多种营地效应（包括PKA，EPAC和HCN通道）发出的cAMP信号。这些 AKAP介导的复合物与AC的复合形成增强了途径，并显示出明显的跨言。 带有RAS/MAPK信号。在血浆中启动的cAMP和RAS介导的途径的激活 膜（PM），对PM内脂质的聚类非常敏感。我们也显示了 脊髓损伤降低了GαI的AC抑制作用，导致DRG中阿片类药物的效力降低 神经元。可以通过一夜之间从幼稚的动物中模仿DRG神经元中这种降低的灵敏度 暴露于神经营养因素，或者在5分钟的临时沉积中接近射击 严重受伤后DRG神经元的阈值。重要的是，伤害感受器过度兴奋和降低 在阿片类药物效力中，由损伤，神经营养因素或急性沉积引起的诱导 通过抑制RAS依赖性信号传导或质膜中脂质的重组而反转。 我们假设在许多伤害模型中发生的持续沉积驱动了改变 在PM脂质组织中，导致ERK信号的增加和阿片类药物反应增加。发布 神经营养因素的增强了这些途径，并与cAMP信号一起驱动 伤害感受器过度兴奋和慢性疼痛状态。为了解决这些假设，我们提出了三个 目标。 1）确定C-RAF降低MOR-GαI抑制AC的机制，2）定义 根据定义和SCI，RAS激活和伤害感受器过度兴奋的机制，以及3）定义 CAMP，C-RAF和CAMP信号传导之间相互作用的功能后果 ERK。重要的是，我们的模型标识了多种FDA批准的药物，这些药物可以简单地增强 内源性阿片类药物反应和严重损伤后的伤害感受器过度症状。