Design of Slack Channel Activators

描述(申请人提供)：钠激活钾(KNA)通道广泛表达于整个中枢神经系统。众所周知，激活这些通道可以保护细胞免受缺氧性损伤。然而，直到最近克隆了这一新的K通道家族的基因后，KNA电流的分子相关性才被发现。SLACK(序列类似于钙激活的K通道)和SLICK，也被称为Slo2.2(KCa4.1)和Slo2.1(KCa4.2)，目前还没有允许调节其功能的药理工具。因此，在这笔赠款的帮助下，我们提议设计有效的、可穿透大脑的Slack通道激活剂，可以用来探索这些有趣的通道的治疗潜力。在正常神经元中，KNA通道有助于重复放电后的缓慢后超极化，调节爆发率，并提高动作电位锁定传入刺激的准确性。进一步的证据表明，当细胞质膜Na-K-ATPase被缺氧抑制导致细胞内钠水平增加时，KNA通道在保护细胞免受缺血条件下的损伤中起着至关重要的作用。在这种情况下，KNA通道的激活可能通过稳定膜电位和保护神经元免受钙超载而阻止钙内流。在这一概念的证明中，线虫Slack的同源基因突变使这些动物对缺氧高度敏感，这表明KNA通道在该物种中提供了抵御缺氧的内源性保护。因此，增加KNA通道活性的化合物在治疗中风和预防全脑缺血的影响方面应该是有用的，例如在脑性瘫痪中。通过增加慢后超极化，KNA通道激活剂也可能有助于降低癫痫和共济失调的神经元兴奋性。通过筛选已知的激活相关大电导钙激活K通道BK(Slo1，Maxi-K)的各种药效团，最近发现联苯硫醚和4-芳基喹诺酮类化合物在低微摩尔范围内激活Slack通道。有趣的是，4-芳基喹诺酮系列中的两个化合物被发现在不影响BK通道的情况下增加了Slack的活性，这表明有可能分离这两种活性。通过结合i)经典药物化学，ii)最近开发的高通量测定质膜质量重分布以确定Slack激活，iii)电生理学和iv)大鼠的药代动力学实验，我们在这里建议提高我们的先导的效力、选择性和脑穿透能力。我们的总体目标是为科学界提供一种适合体内使用的Slack通道激活剂。 公共卫生相关性：基于钠激活钾(KNA)通道在大脑中的丰富表达，它们可能成为治疗中风、脑瘫、癫痫和共济失调的新药物靶点。然而，这些重要的通道目前还没有药理调节剂。在这笔赠款的帮助下，我们将尝试设计可用作科学工具化合物的小分子KNA通道激活剂，以测试KNA通道是否真的构成神经疾病的新靶点。

DESCRIPTION (provided by applicant): Sodium-activated potassium (KNa) channels are widely expressed throughout the central nervous system. Activation of these channels is known to protect cells from hypoxic injury. The molecular correlate of KNa currents, however, was unknown until the genes underlying this new family of K+ channels were cloned relatively recently. Slack (Sequence like a calcium-activated K channel) and Slick, which are also referred to as Slo2.2 (KCa4.1) and Slo2.1 (KCa4.2), currently have no pharmacological tools that allow for modulation of their function. With the help of this grant we are therefore proposing to design potent and brain-penetrant Slack channel activators that could be used to explore the therapeutic potential of these interesting channels. In normal neurons, KNa channels contribute to the slow afterhyperpolarizations that follows repetitive firing, regulate rates of bursting and enhance the accuracy with which action potentials lock to incoming stimuli. Evidence further indicates that KNa channels play a crucial role in protecting cells from injury under ischemic conditions, when inhibition of the plasma membrane Na+-K+-ATPase by the lack of oxygen leads to an increase in intracellular sodium levels. Activation of KNa channels under these circumstances is likely to prevent calcium entry by stabilizing the membrane potential and protecting neurons from overloading with calcium. In proof of this concept, mutation of the ortholog of Slack in the nematode C. elegans renders these animals hypersensitive to hypoxia indicating that KNa channels provide endogenous protection against hypoxia in this species. Compounds that increase the activity of KNa channel therefore should be therapeutically useful for the treatment of stroke and the prevention of the effects of global cerebral ischemia as occurs, for example, in cerebral palsy. By increasing the slow afterhyperpolarizations, KNa channel activators may also be useful for reducing neuronal excitability in epilepsy and ataxia. By screening various pharmacophores known to activate the related large-conductance Ca2+-activated K+ channel BK (Slo1, Maxi-K) it was recently discovered that biphenylthioles and 4-arylquinolinones activate Slack channels in the low micromolar range. Interestingly, two compounds in the 4-arylquinolone series were found to increase Slack activity without exerting effects on BK channels demonstrating that it is possible to separate the two activities. By combining i) classical medicinal chemistry, ii) a recently developed high- throughput assay measuring mass redistribution at the plasma membrane to determine Slack activation, iii) electrophysiology and iv) pharmacokinetic experiments in rats we here propose to improve the potency, selectivity and brain-penetration of our leads. Our overall goal is to provide the scientific community with a Slack channel activator that is suitable for in vivo use. PUBLIC HEALTH RELEVANCE: Based on their abundant expression in the brain sodium-activated potassium (KNa) channels potentially constitute novel drug targets for the treatment of stroke, cerebral palsy, epilepsy and ataxia. However, these important channels currently have no pharmacological modulators. With the help of this grant we will attempt to design small molecule KNa channel activators that could be used as scientific tool compounds to test whether KNa channels indeed constitute novel targets for neurological diseases.