Nephrin is expressed on the surface of insulin vesicles and facilitates glucose-stimulated insulin release

Alessia Fornoni, Jongmin Jeon, Javier Varona Santos, Lorenzo Cobianchi, Alexandra Jauregui, Luca Inverardi, Slavena A. Mandic, Christina Bark, Kevin Johnson, George McNamara, Antonello Pileggi, R. Damaris Molano, Jochen Reiser, Karl Tryggvason, Dontscho Kerjaschki, Per Olof Berggren, Peter Mundel, Camillo Ricordi

Research output: Contribution to journalArticle

Abstract

OBJECTIVE-Nephrin, an immunoglobulin-like protein essential for the function of the glomerular podocyte and regulated in diabetic nephropathy, is also expressed in pancreatic β-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 β-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 vesicleactin interaction and mobilization to the plasma membrane. Development of drugs targeting nephrin may represent a novel approach to treat diabetes.

Original languageEnglish
Pages (from-to)190-199
Number of pages10
JournalDiabetes
Volume59
Issue number1
DOIs
Publication statusPublished - Jan 2010

ASJC Scopus subject areas

  • Internal Medicine
  • Endocrinology, Diabetes and Metabolism

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    Fornoni, A., Jeon, J., Santos, J. V., Cobianchi, L., Jauregui, A., Inverardi, L., Mandic, S. A., Bark, C., Johnson, K., McNamara, G., Pileggi, A., Damaris Molano, R., Reiser, J., Tryggvason, K., Kerjaschki, D., Berggren, P. O., Mundel, P., & Ricordi, C. (2010). Nephrin is expressed on the surface of insulin vesicles and facilitates glucose-stimulated insulin release. Diabetes, 59(1), 190-199. https://doi.org/10.2337/db09-0655