Harnessing gating-pore currents to identify novel Nav1.7 modulators

描述（由申请人提供）：疼痛是重大的国家健康问题，每年花费美国公众超过1000亿美元。电压门控钠电流对动作电位的产生至关重要，并有助于伤害神经元的高兴奋性。然而，尽管钠通道阻滞剂对预防急性疼痛有用，但由于缺乏同种异体选择性，它们通常与不良的心脏和中枢神经系统副作用相关，限制了它们的治疗窗口和治疗慢性和神经性疼痛的有效性。几种电压门控钠通道在伤害神经元（Nav1.7、Nav1.8和Nav1.8）中优先表达。特别是Nav1.7在疼痛中发挥着绝对关键的作用，包括慢性神经性疼痛。开发专门针对这些伤害性钠通道的药物可以大大增加对疼痛的治疗手段。大多数已确定的钠通道抑制剂和调节剂与钠通道孔相互作用-由于排列在孔内的氨基酸残基在9个钠通道基因中高度保守，因此很难鉴定具有同种异构体特异性的孔阻滞剂。相比之下，电压传感器

DESCRIPTION (provided by applicant): Pain is significant national health problem, costing the American public more than $100 billion each year. Voltage-gated sodium currents are essential to the generation of action potentials and contribute to the hyperexcitability of nociceptive neurons. However, although sodium channel blockers are useful for preventing acute pain, they are often associated with undesirable cardiac and CNS side effects due to their lack of isoform selectivity, limiting their therapeutic window and their effectiveness in treating chronic and neuropathic pain. Several voltage-gated sodium channels are preferentially expressed in nociceptive neurons (Nav1.7, Nav1.8 and Nav1.8). Nav1.7 in particular has been shown to play an absolutely crucial role in pain, including chronic neuropathic pain. Developing drugs that specifically target these nociceptive sodium channels could substantially increase the therapeutic armamentarium for pain. The majority of sodium channel inhibitors and modulators that have been identified interact with the sodium channel pore - because the amino acid residues lining the pore are highly conserved among the nine sodium channel genes, it has been difficult to identify pore blockers with isoform specificity. By contrast, the voltage-sensors of sodium channels show greater divergence and therefore it should be possible to develop voltage gating modifiers that target specific sodium channel isoforms. We are proposing to harness gating-pore currents to monitor sodium channel voltage-sensor function and enhance our ability to screen for voltage- gating modifiers. These gating-pore currents are currents that selectively flow through the voltage sensor domains of ion channels and provide a direct read-out of the voltage-sensor position. Importantly, they do not reflect pore activity. Two specific aims are proposed: AIM I will determine if gating-pore currents can be used to monitor the activity of voltage-sensor modulators of voltage-gated sodium channels. AIM II will determine if isolated voltage sensors or chimeric bacterial sodium channels containing a single voltage sensor of Nav1.7 can generate gating-pore currents that are sensitive to specific voltage-sensor modulators. Although we initially target Nav1.7 channels because of their importance in pain, this approach should be readily adaptable for identification and characterization of voltage-sensor modulators of other voltage-gated channels and therefore could be used to help identify isoform specific voltage-gated channel modulators that can be used in research and for the development of better therapeutics to treat a multitude of disorders of excitability such as pain, epilepsy and cardiac arrhythmias. PUBLIC HEALTH RELEVANCE: Pain is a serious medical problem that is difficult to treat in many patients. There is exceptionally strong experimental and clinical evidence indicating that drugs targeting a specific protein, Nav1.7, might be especially good at selectively blocking pain sensations. This study develops a new assay for identifying drugs that target the activity of this crucial protein.