Department of Pharmaceutical Sciences, University of California-Irvine, Irvine, California 92697.
Department of Pharmaceutical Sciences, University of California-Irvine, Irvine, California 92697
J Neurosci. 2023 Oct 25;43(43):7073-7083. doi: 10.1523/JNEUROSCI.2307-22.2023. Epub 2023 Aug 30.
Neuronal Kv7 voltage-gated potassium channels generate the M-current and regulate neuronal excitability. Here, we report that dehydroepiandrosterone sulfate (DHEAS) is an endogenous Kv7 channel modulator that attenuates Gq-coupled receptor-induced M-current suppression. DHEAS reduced muscarinic agonist-induced Kv7-current suppression of Kv7.1, Kv7.2, Kv7.4, or Kv7.5 homomeric currents and endogenous M-currents in rat sympathetic ganglion neurons. However, DHEAS per se did not alter the voltage dependence of these Kv7 homomeric channels or the m1 receptor-induced activation of phospholipase C or protein kinase C. DHEAS-treated Kv7.2 homomeric currents became resistant to depletion of phosphatidylinositol 4,5-bisphosphate (PIP2) induced by voltage-activated phosphatase, Ci-VSP or eVSP. Our computational models predicted a novel binding site for DHEAS in the cytoplasmic domain of Kv7 subunits. A single-point mutation of the predicted key histidine into cysteine in the rat Kv7.2 subunit, rKv7.2(H558C), resulted in a loss of effects of DHEAS on muscarinic Kv7 current suppression. Furthermore, administration of DHEAS in mice of both sexes reduced late phase pain responses in the formalin paw test. However, it did not have effects on early phase responses in the formalin paw test or responses in the hot plate test. Coadministration of a selective Kv7 inhibitor, XE991, and DHEAS eliminated analgesic effects of DHEAS in late phase responses in the formalin paw test. Collectively, these results suggest that DHEAS attenuates M-current suppression by stabilizing PIP2-Kv7 subunit interaction and can mitigate inflammatory pain. M-current suppression induced by stimulation of Gq-coupled receptors is a form of Kv7 current modulation that can reversibly increase neuronal excitability. This study demonstrates that DHEAS, an endogenous steroid hormone, is a novel Kv7 channel modulator that can attenuate M-current suppression without affecting basal Kv7 channel kinetics. Administration of DHEAS alleviated inflammatory pain in rodents. These results suggest that the degree of M-current suppression can be dynamically regulated by small molecules. Therefore, this novel form of Kv7 channel regulation holds promising potential as a therapeutic target for sensitized nervous activities, such as inflammatory pain.
神经元 Kv7 电压门控钾通道产生 M 电流并调节神经元兴奋性。在这里，我们报告脱氢表雄酮硫酸盐 (DHEAS) 是一种内源性 Kv7 通道调节剂，可减轻 Gq 偶联受体诱导的 M 电流抑制。DHEAS 降低了毒蕈碱激动剂诱导的 Kv7.1、Kv7.2、Kv7.4 或 Kv7.5 同源电流以及大鼠交感神经节神经元内源性 M 电流的抑制。然而，DHEAS 本身并没有改变这些 Kv7 同源通道的电压依赖性，也没有改变 m1 受体诱导的磷脂酶 C 或蛋白激酶 C 的激活。用 DHEAS 处理的 Kv7.2 同源电流对电压激活磷酸酶 Ci-VSP 或 eVSP 诱导的磷脂酰肌醇 4,5-二磷酸 (PIP2) 的耗竭变得具有抵抗力。我们的计算模型预测了 DHEAS 在 Kv7 亚基细胞质结构域中的一个新的结合位点。大鼠 Kv7.2 亚基中的预测关键组氨酸突变为半胱氨酸，rKv7.2(H558C)，导致 DHEAS 对毒蕈碱 Kv7 电流抑制的作用丧失。此外，在雌雄小鼠中给予 DHEAS 可减少福尔马林足爪试验中的后期疼痛反应。然而，它对福尔马林足爪试验的早期反应或热板试验的反应没有影响。XE991（一种选择性 Kv7 抑制剂）和 DHEAS 的共同给药消除了 DHEAS 在福尔马林足爪试验后期反应中的镇痛作用。总的来说，这些结果表明 DHEAS 通过稳定 PIP2-Kv7 亚基相互作用来减轻 M 电流抑制，并可以减轻炎症性疼痛。由 Gq 偶联受体刺激诱导的 M 电流抑制是一种可逆增加神经元兴奋性的 Kv7 电流调节形式。这项研究表明，DHEAS，一种内源性类固醇激素，是一种新型 Kv7 通道调节剂，可减轻 M 电流抑制而不影响基础 Kv7 通道动力学。给予 DHEAS 可减轻啮齿动物的炎症性疼痛。这些结果表明，M 电流抑制的程度可以通过小分子动态调节。因此，这种新形式的 Kv7 通道调节具有作为治疗敏化神经活动（如炎症性疼痛）的潜在治疗靶点的潜力。
