Polycystin activators as novel therapeutic approach for ADPKD

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PROJECT SUMMARY Ion channels control such diverse processes as fertilization, proliferation, development, learning and memory. Ion channels are multispan transmembrane proteins that transport ~106 to 107 ions per second across membranes. The primary cilium is an antenna-shaped protrusion from the apical plasma membrane and are enriched in a specific subset of ion channels called polycystins. Mutations in polycystins cause Autosomal Dominant Polycystic Kidney Disease (ADPKD), which manifests in cyst formation in kidney and other organs, such as liver and pancreas. The molecular mechanisms by which polycystin channels are spatially and temporally regulated and thus contribute to ciliary signaling cascades still remains poorly understood. The central goal of this project is to develop small molecule activators of the polycystin channel as novel tools to study the fundamental mechanisms of polycystin signaling at the molecular and cellular level. Such tools are currently unavailable to the research community and are likely to function as novel therapeutics for ADPKD. Recently ion channel agonists have been developed as novel therapeutics to restore dysfunctional ion channel activity in humans. Examples include activators of cystic fibrosis transmembrane conductance regulator (CFTR) ion channels as therapeutics for the treatment of cystic fibrosis. This proposal contains two specific aims: the first aim proposes imaging-based high throughput screens to identify agonists of polycystin channels using novel cellular assays that we have recently developed to interrogate polycystin ion channel activity. In the second aim will test the potency of such agonists to restore activity of polycystin channels with missense mutations in PC1 or PC2. Such missense mutations can likely be revitalized by specific agonists and account for ~35% of all pathogenic ADPKD mutations.