Investigate the trafficking and function of polycystins in primary cilia and their implications for polycystic kidney disease - PROJECT SUMMARY Autosomal dominant polycystic kidney disease (ADPKD) is the most common monogenetic cause of kidney failure. It affects ~1 in 500 to 1,000 live births, with ~50% of patients needing dialysis or renal transplantation by age 60 years of age. Mutations in PKD1 and PKD2 genes account for >90% of ADPKD cases, and involves reduction/loss of functional ADPKD proteins, polycystins (PCs), in the sensory organelle, primary cilium. Growing evidence suggests that enhancing the ciliary dosage and/or function of PCs could slow down ADPKD progression. Thus, understanding mechanisms regulating the compartmentalized availability and functionality of PCs in primary cilia is vital for developing more effective and safer treatments, as the current FDA-approved drug, Tolvaptan, has limited benefits and significant side effects. The long-term goal of our research is to understand how the anti-cystogenesis function of PCs is compartmentalized in primary cilia and how it is specifically regulated. We have identified novel players involved in the ciliary trafficking and function of PCs. The current proposal addresses three questions: Aim 1, Investigate how the HYLS1-PIPKIg axis regulates the ciliary base docking of vesicles carrying PCs. Aim 2, Delineate how the NEK8-centered inversin compartment enables the ciliary entry of PCs. Aim 3, Determine the pathogenic impact of GPR161-mediated cAMP synthesis and PKA activation in primary cilia when PCs are depleted. We will employ gain-of-function, loss-of-function, and suppression-rescue approaches by applying gene editing tools in renal epithelial cell models carrying ADPKD-related mutations. Fluorescence microscopy including super- resolution and live-cell imaging will be used to analyze protein and lipid localization, level, and dynamics in primary cilia. We will determine whether changing the ciliary functional level of PCs can affect renal cystogenesis in Pkd1RC/RC mice that mimic the adult onset ADPKD condition. With this proposal, we aim to identify key molecules that regulate the functional level of PCs in cilia and their roles in ADPKD pathogenesis. These results may uncover novel molecules or pathways that can be targeted for PKD treatment. In the long term, our studies will inspire future research on enhancing the functionality of PCs in cilia to counteract the pathogenic defects in ADPKD.
