PROJECT SUMMARY Large conductance calcium-activated K channels (SLO-1 or BK channels) play a key physiological role in controlling activity of nerve and smooth muscle, as well as setting the resting membrane potential in epithelial cells. Deletion of BK channel pore-forming (alpha) or modulatory (beta) subunits in gene-targeted animal models can lead to diseases that include arterial hypertension, bladder and erectile dysfunction, and neurological disorders including epilepsy; mutations in human BK channel subunits are linked to generalized epilepsy with paroxysmal dyskinesia (GEPD), asthma, and autism spectrum disorders, and BK channels are upregulated in prostate and other cancers. Selective BK channel activators, as well as inhibitors, could thus become components of treatment regimens for cardiovascular/neurological disease and brain and prostate cancers. To exploit BK channels as a potential medical target, it will be important to expand our molecular arsenal of BK channel activators and inhibitors and learn their mechanisms of action. Doing so will lead to advances in an overall effort to understand BK channel gating mechanisms and ultimately find new treatments for disease. Under this proposal, we will achieve these goals through a combination of 1) cell-based fluorescent screening, which is aimed at discovery of novel gating modulators for BK channels comprised of tissue-specific subunit combinations, and 2) systematic computational and electrophysiological experiments to determine whether these drugs modulate BK channel function through interactions with the Ca2+-sensor, voltage-sensor, or pore domains of the channel. Our proposed research will generate new pharmacological research tools to modulate BK channels, which will be combined with established strengths in quantitative electrophysiological analysis, to gain fundamental insights toward BK channel gating mechanisms that may further lead to new treatments for disease.