Lee Narasaem, Kim Subin, Lee Na Young, Jo Heeji, Jeong Pyeonghwa, Pagire Haushabhau S, Pagire Suvarna H, Ahn Jin Hee, Jin Mi Sun, Park Chul-Seung
School of Life Sciences, Gwangju Institute of Science and Technology (GIST), Gwangju, Republic of Korea.
Department of Chemistry, Duke University, Durham, NC, USA.
Life Sci Alliance. 2024 Aug 1;7(10). doi: 10.26508/lsa.202402621. Print 2024 Oct.
The large-conductance calcium-activated potassium (BK) channel, which is crucial for urinary bladder smooth muscle relaxation, is a potential target for overactive bladder treatment. Our prior work unveiled CTIBD as a promising BK channel activator, altering and This study investigates CTIBD's activation mechanism, revealing its independence from the Ca and membrane voltage sensing of the BK channel. Cryo-electron microscopy disclosed that two CTIBD molecules bind to hydrophobic regions on the extracellular side of the lipid bilayer. Key residues (W22, W203, and F266) are important for CTIBD binding, and their replacement with alanine reduces CTIBD-mediated channel activation. The triple-mutant (W22A/W203A/F266A) channel showed the smallest shift with a minimal impact on activation and deactivation kinetics by CTIBD. At the single-channel level, CTIBD treatment was much less effective at increasing in the triple mutant, mainly because of a drastically increased dissociation rate compared with the WT. These findings highlight CTIBD's mechanism, offering crucial insights for developing small-molecule treatments for BK-related pathophysiological conditions.
大电导钙激活钾（BK）通道对膀胱平滑肌舒张至关重要，是治疗膀胱过度活动症的潜在靶点。我们之前的研究表明CTIBD是一种有前景的BK通道激活剂，可改变……本研究探究了CTIBD的激活机制，发现其独立于BK通道的钙和膜电压传感。冷冻电子显微镜显示，两个CTIBD分子与脂质双分子层胞外侧的疏水区域结合。关键残基（W22、W203和F266）对CTIBD结合很重要，用丙氨酸取代它们会降低CTIBD介导的通道激活。三突变体（W22A/W203A/F266A）通道的……位移最小，对CTIBD介导的激活和失活动力学影响最小。在单通道水平，CTIBD处理对增加三突变体中的……效果要差得多，主要是因为与野生型相比，解离速率大幅增加。这些发现突出了CTIBD的作用机制，为开发针对BK相关病理生理状况的小分子治疗方法提供了关键见解。
