Dibenzoylmethane, a novel β-diketone pore blocker of large-conductance calcium-activated potassium channel

Large-conductance calcium-activated potassium (BKCa) channels are ubiquitously expressed in mammalian cells and regulate electrical activity, intracellular calcium signaling, and cell survival. Although BKCa dysfunction has been linked to multiple diseases, the number of selective channel modulators is limited. In this study, we characterize dibenzoylmethane (DBM), a plant-derived compound isolated from Hottonia palustris, as a novel inhibitor of BKCa channel activity in both plasma membrane and mitochondrial BKCa. Electrophysiological recordings revealed that DBM lowers the open probability of BKCa channels in a concentration-dependent fashion and markedly reduces mean open time, leading to a pronounced flickering behavior - hallmarks of pore-targeted blockade. Competition experiments demonstrated that DBM antagonizes the effect of paxilline, a high-affinity pore-binding inhibitor, suggesting overlapping binding sites. Molecular dynamics simulations further supported this hypothesis, showing that several DBM molecules can block the pore by employing {pi}-{pi} interactions with each other and pore residues. On top of the pore, the carbonyl groups of DBM block the nearest potassium ion in the selectivity filter. The presence of DBM induces the removal of water molecules from the pore. To assess the structural requirements for activity, we tested three DBM analogs: phenyl-1,3-butanedione (PBD), trans-chalcone (T-Ch), and (E)-1,3-diphenylprop-2-en-1-ol (DPE). T-Ch and DPE inhibited BKCa channels with comparable efficacy to DBM, whereas PBD was significantly less potent. These results indicate that diphenyl substitution and structural rigidity are critical determinants of inhibitory activity. Our findings position DBM and its analogs as promising chemical scaffolds for the development of selective BKCa channel modulators with potential pharmacological applications.