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.

Public Health Relevance

Glomerular diseases leading to end stage renal disease are major cause of kidney malfunction in United States. Our previous studies have shown that functional and biochemical changes in the proteins that are central to the maintenance of the kidney filtration system leads to the development of glomerular disorders. In this study we will determine the role of a novel protein Myo1c and identify novel targets for use in the development of novel therapies aimed at restoring the selective filtration function of kidneys during various glomerular disorders.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Pathobiology of Kidney Disease Study Section (PBKD)
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Rys-Sikora, Krystyna E
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University of Pennsylvania
Internal Medicine/Medicine
Schools of Medicine
United States
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Arif, Ehtesham; Rathore, Yogendra S; Kumari, Babita et al. (2014) Slit diaphragm protein Neph1 and its signaling: a novel therapeutic target for protection of podocytes against glomerular injury. J Biol Chem 289:9502-18
Furcht, C M; Munoz Rojas, A R; Nihalani, D et al. (2013) Diminished functional role and altered localization of SHP2 in non-small cell lung cancer cells with EGFR-activating mutations. Oncogene 32:2346-55, 2355.e1-10
Tiwari, Ajit; Jung, Jae-Joon; Inamdar, Shivangi M et al. (2013) The myosin motor Myo1c is required for VEGFR2 delivery to the cell surface and for angiogenic signaling. Am J Physiol Heart Circ Physiol 304:H687-96
Arif, Ehtesham; Kumari, Babita; Wagner, Mark C et al. (2013) Myo1c is an unconventional myosin required for zebrafish glomerular development. Kidney Int 84:1154-65
Mallik, Leena; Arif, Ehtesham; Sharma, Pankaj et al. (2012) Solution structure analysis of cytoplasmic domain of podocyte protein Neph1 using small/wide angle x-ray scattering (SWAXS). J Biol Chem 287:9441-53
Arif, E; Wagner, M C; Johnstone, D B et al. (2011) Motor protein Myo1c is a podocyte protein that facilitates the transport of slit diaphragm protein Neph1 to the podocyte membrane. Mol Cell Biol 31:2134-50
Garg, Renu; Peddada, Nagesh; Sagar, Amin et al. (2011) Visual insight into how low pH alone can induce actin-severing ability in gelsolin under calcium-free conditions. J Biol Chem 286:20387-97