Myo1c Participates in Podocyte Junction Formation Through Interaction with Neph1

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DESCRIPTION (provided by applicant): Glomerular diseases that lead to damaging changes in kidney filtration are an increasing cause of ESRD (end stage renal disease) nationwide. Unfortunately, the molecular mechanisms governing the development of ESRD remain poorly understood. Identification of podocyte proteins, including Neph1 and its associated protein complex, that are critical components of kidney filtration was a major advancement in understanding the organization of slit diaphragm. A number of recent studies, including ours, now demonstrate that dynamic interactions between Neph1 and its associated proteins including Grb2, ZO-1, Nephrin and Par3 regulates the actin cytoskeleton at the slit diaphragm. Data also suggest that Neph1 and its complex are frequently found in various sub cellular compartments away from the cell membrane following glomerular injury. Retargeting these proteins back to their membrane filtration slit location is likely to require an active molecular motor-based mechanism. We now have exciting results that identify a novel interaction of Neph1 with Myo1c, a member of the un-conventional Myosin family whose members are ATPase motor proteins that bind to actin and can generate force. Myo1c also has membrane binding and Calmodulin binding domains and has been shown to have a role in membrane cytoskeletal events in diverse cell types. We recently published an article demonstrating that glomerular injury results in mis-localization of the Neph1 complex leading to loss of cell junctions and proteinuria, whereas recovery from injury correlates with the Neph1 complex's return to the cell periphery (Wagner et al., JBC 2008). We believe that the interaction of Neph1 with Myo1c plays a critical role in regulating the organization of the Neph1 complex. In this study we propose to investigate the Neph1 and Myo1c interaction under in-vitro and in- vivo conditions. The specific aims proposed for this study are: 1) Define the physiologic and pathophysiologic organization of Myo1c in podocytes. 2) Determine the significance of Myo1c-Neph1 interaction in the assembly and translocation of Neph1 complex to the filtration slit in response to glomerular injury. 3) Determine the significance of Myo1c and its interaction with Neph1 in maintaining the glomerular function under in-vivo conditions. The results from this study will increase our understanding of how slit diaphragm proteins organize under both physiological and nonphysiological conditions resulting in new avenues of research aimed at improving clinical outcome following glomerular injury.