School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, 61005, Republic of Korea; Center for AI-applied High Efficiency Drug Discovery, Gwangju Institute of Science and Technology (GIST), Gwangju, 61005, Republic of Korea.
Department of Chemistry, Gwangju Institute of Science and Technology (GIST), Gwangju, 61005, Republic of Korea.
Eur J Pharmacol. 2022 Jul 15;927:175055. doi: 10.1016/j.ejphar.2022.175055. Epub 2022 May 27.
The large-conductance Ca-activated K channel (BK channel) is involved in repolarizing the membrane potential and has a variety of cellular functions. The BK channel is highly expressed in bladder smooth muscle and mediates muscle relaxation. Compounds that activate the BK channel have therapeutic potential against pathological symptoms associated with the overactivity of bladder smooth muscle. In this regard, we screened a chemical library of 9938 compounds to identify novel BK channel activators. A cell-based fluorescence assay identified a structural family of compounds containing a common tricyclic quinazoline ring that activated the BK channel. The most potent compound TTQC-1 (7-bromo-N-(3-methylphenyl)-5-oxo-1-thioxo-4,5-dihydro[1,3]thiazolo[3,4-a]quinazoline-3-carboxamide) directly and reversibly activated the macroscopic current of BK channels expressed in Xenopus oocytes from both sides of the cellular membrane. TTQC-1 increased the maximum conductance and shifted the half activation voltage to the left. The apparent half-maximal effective concentration and dissociation constant were 2.8 μM and 7.95 μM, respectively. TTQC-1 delayed the kinetics of channel deactivation without affecting channel activation. The activation effects were observed over a wide range of intracellular Ca concentrations and dependent on the co-expression of β1 and β4 auxiliary subunits, which are highly expressed in urinary bladder. In the isolated smooth muscle cells of rat urinary bladder, TTQC-1 increased the K currents which can be blocked by iberiotoxin. Finally, oral administration of TTQC-1 to hypertensive rats decreased the urination frequency. Therefore, TTQC-1 is a BK channel activator with a novel structure that is a potential therapeutic candidate for BK channel-related diseases, such as overactive bladder syndrome.
大电导钙激活钾通道（BK 通道）参与复极化膜电位，具有多种细胞功能。BK 通道在膀胱平滑肌中高度表达，介导肌肉松弛。激活 BK 通道的化合物具有治疗与膀胱平滑肌过度活动相关的病理症状的治疗潜力。在这方面，我们筛选了 9938 种化合物的化学文库，以鉴定新的 BK 通道激活剂。基于细胞的荧光测定法鉴定了一种含有共同三环喹唑啉环的化合物结构家族，该化合物可激活 BK 通道。最有效的化合物 TTQC-1（7-溴-N-（3-甲基苯基）-5-氧代-1-硫代-4,5-二氢[1,3]噻唑并[3,4-a]喹唑啉-3-甲酰胺）直接和可逆地激活了从细胞膜两侧表达的 Xenopus 卵母细胞中 BK 通道的宏观电流。TTQC-1 增加了最大电导率并将半激活电压向左移动。表观半最大有效浓度和离解常数分别为 2.8μM 和 7.95μM。TTQC-1 延迟了通道失活的动力学而不影响通道激活。在广泛的细胞内 Ca 浓度范围内观察到激活作用，并且依赖于高度表达于膀胱的β1 和β4辅助亚基的共表达。在大鼠膀胱平滑肌细胞的分离中，TTQC-1 增加了可以被iberiotoxin 阻断的 K 电流。最后，TTQC-1 的口服给予高血压大鼠可降低排尿频率。因此，TTQC-1 是一种具有新型结构的 BK 通道激活剂，是 BK 通道相关疾病（如膀胱过度活动症）的潜在治疗候选药物。
