Discovery and mechanism study of a novel BK(Ca) channel modulator resulting in slow closing

Abstract

The large-conductance Ca2+-activated K+ channel (BK(Ca) channel) plays critical roles in various tissues. In the smooth muscle of the urinary bladder (UBSM), BK(Ca) channel is highly expressed and regulates the spontaneous action potentials that control muscle contraction. To address the pathological symptoms associated with overactivity of bladder smooth muscle, our lab member previously conducted a screening of a chemical library comprising 9,938 compounds in search of novel activators of the BK(Ca) channel and I performed structure-activity relationship (SAR) study through hit compounds by using a cell-based fluorescence assay. Among these 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 remarkable efficiency and activated the macroscopic tail current of BK(Ca )hannels in Xenopus oocytes. DBTB-1 specifically influenced deactivation kinetics without affecting channel activation. In single channel recording, DBTB-1 increased the open-state probability compared to vehicle without affecting its single-channel conductance. These effects were characterized by more delayed channel close time, in contrast to other BK(Ca) channel activators. Furthermore, Analysis of the open dwell time showed additional population. These findings provide new insights by DBTB-1 in the treatment of BK(Ca) channel-associated disorders.