Journal
DIABETES
Volume 59, Issue 1, Pages 190-199Publisher
AMER DIABETES ASSOC
DOI: 10.2337/db09-0655
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Funding
- National Institutes of Health (NIH)/National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) [DK-82636, DK-25802-21]
- NIH/National Center for Research Resources [U42 RR016603, M01RR16587]
- American Diabetes Association [7-09-JF-23]
- Diabetes Research Institute Foundation
- Karasik Foundation
- NATIONAL CENTER FOR RESEARCH RESOURCES [U42RR016603, M01RR016587] Funding Source: NIH RePORTER
- NATIONAL INSTITUTE OF DIABETES AND DIGESTIVE AND KIDNEY DISEASES [R01DK025802, K08DK082636] Funding Source: NIH RePORTER
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OBJECTIVE-Nephrin, an immunoglobulin-like protein essential for the function of the glomerular podocyte and regulated in diabetic nephropathy, is also expressed in pancreatic P-cells, where its function remains unknown. The aim of this study was to investigate whether diabetes modulates nephrin expression in human pancreatic islets and to explore the role of nephrin in P-cell function. RESEARCH DESIGN AND METHODS-Nephrin expression in human pancreas and in MIN6 insulinoma cells was studied by Western blot, PCR, confocal microscopy, subcellular fractionation, and immunogold labeling. Islets from diabetic (n = 5) and nondiabetic (n = 7) patients were compared. Stable transfection and siRNA knockdown in MIN-6 cells/human islets were used to study nephrin function in vitro and in vivo after transplantation in diabetic immunodeficient mice. Live imaging of green fluorescent protein (GFP)-nephrin-transfected cells was used to study nephrin endocytosis. RESULTS-Nephrin was found at the plasma membrane and on insulin vesicles. Nephrin expression was decreased in islets from diabetic patients when compared with nondiabetic control subjects. Nephrin transfection in MIN-6 cells/pseudoislets resulted in higher glucose-stimulated insulin release in Vitro and in vivo after transplantation into immunodeficient diabetic mice. Nephrin gene silencing abolished stimulated insulin release. Confocal imaging of GFP-nephrin-transfected cells revealed nephrin endocytosis upon glucose stimulation. Actin stabilization prevented nephrin trafficking as well as nephrin-positive effect on insulin release. CONCLUSIONS-Our data suggest that nephrin is an active component of insulin vesicle machinery that may affect vesicle-actin interaction and mobilization to the plasma membrane Development of drugs targeting nephrin may represent a novel approach to treat diabetes. Diabetes 59:190-199, 2010
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