Discovery and mechanistic studies of a novel BK_Ca channel modulator inducing long openings

The large-conductance Ca2+-activated K+ channel (BKCa channel) plays critical roles in various tissues. In the smooth muscle of the urinary bladder, BKCa channel is highly expressed and regulates the spontaneous action potentials that control muscle contraction. Thus, the chemical activators for BKCa channel have their therapeutic potential against overactive bladder syndrome. Preveiously, we conducted a screening of a chemical library comprising 9,938 compounds in search of novel activators of the BKCa channel and performed structure-activity relationship study through hit compounds by using a cell-based fluorescence assay. Among the optimized compounds, DBTB-1 (N-[4-(2,4-dimethyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazin-6-yl)-1,3-thiazol-2-yl]benzamide) displayed a robust activation of macroscopic BKCa channel currents in Xenopus oocytes. In contrast to other BKCa channel activators, DBTB-1 mainly influenced deactivation kinetics of the channel without affecting channel activation significantly. At the single-channel level, DBTB-1 increased the open-state probability compared to vehicle without affecting its single-channel conductance, indicating the delayed closing of the channel in the presence of the drug. Furthermore, analysis of the open dwell-time showed an additional population of long openings induced by DBTB-1. Thus, these unique characteristics of DBTB-1 can be useful in designing a new class of BKCa channel activators and might be utilized in developing therapuetics targeting specific aspect of the channel function. This research was supported by Korea Drug Development Fund funded by Ministry of Science and ICT, Ministry of Trade, Industry, and Energy, and Ministry of Health and Welfare (RS-2023-00258812). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.