Abstract: TH-OR129

SH3D21 Dysregulation May Cause Disruption of the Actin Cytoskeleton in Diabetic Nephropathy

Session Information

Category: Diabetes

  • 501 Diabetes Mellitus and Obesity: Basic - Experimental

Authors

  • Schenk, Heiko Joachim, Hannover Medical School, Hannover, Germany
  • Schaefer, Irini, Hannover Medical School, Hannover, Germany
  • Bolanos-Palmieri, Patricia, Hannover Medical School, Hannover, Germany
  • Teng, Beina, Hannover Medical School, Hannover, Germany
  • Müller-Deile, Janina, Hannover Medical School, Hannover, Germany
  • Haller, Hermann G., Hannover Medical School, Hannover, Germany
  • Schiffer, Mario, Hannover Medical School, Hannover, Germany
Background

Diabetes is the most common cause of end-stage renal disease. The onset of albuminuria and podocyte damage is associated with disruption of the actin cytoskeleton. We identified SH3D21 as a potential key regulator of the actin cytoskeleton in podocytes which changes its expression in diabetes.

Methods

Cultured murine and human podocytes under glucose- and VEGF-stimulation were used to mimic diabetic conditions and compared to osmolality controls with mannitol. To model type I diabetes, C57BL/6J mice were treated for 5 days either with intraperitoneal injections of streptozotocin (STZ) or sodium citrate buffer as control while blood glucose levels were determined for 16 weeks. WB analysis of STZ-injected mice and buffer-injected mice was carried out. Immunofluorescence (IF) staining on cryosections of STZ- or buffer-injected mice was performed. IF of SH3D21 was performed on kidney cryosections of STZ- or buffer-injected mice as well as human and murine cultured podocytes. To identify protein interaction partners of SH3D21, we performed co-affinity purification mass spectrometry (MS) of murine whole kidneys as well as human cultured podocytes. Knockdown of sh3d21 was performed in zebrafish and proteinuria was measured using transgenic zebrafish line Tg(l-fabp:eGFP-DBP).

Results

Reduction of SH3D21 protein expression was detected in murine kidney and cultured podocytes under diabetic conditions. IF of diabetic murine kidney cryosections showed reduced Sh3d21 expression associated with the absence of Sh3d21-Nephrin co-expression. In murine and human podocytes we could document a shift from a membrane to a perinuclear or cytosolic speckled expression pattern which paralleled actin disruption under glucose- or VEGF-treatment. In murine and human podocytes SH3D21 primarily interacts with cytoskeletal proteins. Knockdown of sh3d21 in zebrafish caused proteinuria and foot process effacement.

Conclusion

SH3D21 is a novel interaction partner of nephrin which appears to be an important regulator of the actin cytoskeleton impacting slit diaphragm functions in diabetes.

Funding

  • Government Support - Non-U.S.