Mutations in PKD1 are responsible for over 85% of cases in autosomal dominant polycystic kidney disease (ADPKD). A number of studies by us and others have implicated that the ADPKD proteins polycystin-1 and -2 (PC1 and PC2) modulate a number of cellular events and signaling pathways such as Ca2+ signaling, JAK- STAT, mTOR, cyclic AMP (cAMP), and planar cell polarity (PCP). How polycystins modulate these pathways, however, remains elusive. The sequence of these signaling events is unknown. A major challenge is that many experiments have been performed using different model systems, different cell types, and under different conditions. Better understanding of the cystogenic mechanisms and disease progression of ADPKD is a high priority for clinical care. Our long-term goal of this proposal is to identify and modulate the factors controlling cyst formation and enlargement in ADPKD using multidisciplinary approaches. We previously reported a biochemical interaction between PC1 and protein kinase C and casein kinase substrate in neurons 2 (Pacsin 2), a cytoplasmic phosphoprotein that has been implicated in cytoskeletal organization and vesicle trafficking. By in vitro studies, we found that PC1, Pacsin 2 and N-Wasp are in the same protein complex and deficiency of either PC1 or Pacsin 2 leads to defects in actin cytoskeleton and cell migration in cultured cells. Here we propose to extend our study of Pacsin 2 to multiple orthologous mouse models of ADPKD that we have developed to understand mechanisms suppressing cystogenesis. We aim to develop an in vivo imaging protocol of cell migration and to elucidate the role of Pascin 2 in cystogenesis using multidisciplinary approaches including the analysis the cystogenic proteome and phosphoproteome in human and mouse ADPKD models using the latest quantitative proteomics technology, coupled with innovative bioinformatics tools. The proposed studies will likely discover novel therapeutic targets central to the early event(s) in cystogenesis.