Development of Bioactive Chemical Probes for Calcium-activated Chloride Channel

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DESCRIPTION (provided by applicant): Ion channels are membrane proteins, found in both excitable cells and non-excitable cells. They selectively conduct ions across cellular membranes and play a critical role in cellular physiology, including electrical and cellular signaling, ion homeostasis, and hormone secretion. The objective of this proposal is to find potent and specific small molecule chemical probes for TMEM16A that encodes the calcium-activated chloride channel (CaCC). Abnormality of CaCC is thought to be causal to diseases, such as cystic fibrosis, asthma, chronic bronchitis, and hypertension. Its role is implicated in numerous physiological processes including cardiac and neuronal excitation, sensory transduction, trans-epithelial secretion, smooth muscle contraction, and fertilization. In collaboration with Dr. Lily Jan's laboratory, which first cloned the TMEM16A gene, we have developed several cell lines and a fluorescence-based iodide surrogate flux assay. The protocol for high-throughput screening is being tested for the CaCC target TMEM16A. This proposal outlines a plan to conduct a >300,000-compound screen using the TMEM16A expressing cell line with a genetically encoded Cl-/I- biosensor to search potent inhibitor/activator probes for CaCC. The active compounds will then be evaluated by automated patch-clamp recording. In collaboration with Dr. Lily Jan at University of California at San Francisco, our future plan includes testing of the isolated compounds in native preparations, such as neurons and epithelium, respectively. These active compounds, with further efforts in pharmacology and medicinal chemistry, may be exploited either as tools or as lead compounds for developing therapeutic remedies to the CaCC-associated diseases. PUBLIC HEALTH RELEVANCE: The recent discovery of the calcium-activated chloride channel (CaCC) has paved a new path to identify small molecule probes. Abnormality of CaCC activity is thought to be causal to several major diseases, such as cystic fibrosis, asthma, chronic bronchitis, and hypertension. Its role is implicated in numerous physiological processes including cardiac and neuronal excitation, sensory transduction, trans-epithelial secretion, smooth muscle contraction, and fertilization. Therefore, specific modulation compounds are useful to aid therapeutic development.