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Abstract: TH-PO216

Diabetes Activates Dynein Mediated Trafficking and Degradation of Nephrin via AMPK/SP-1 Regulated Transcription

Session Information

Category: Diabetic Kidney Disease

  • 601 Diabetic Kidney Disease: Basic

Authors

  • Sun, Hua, The University of Iowa, Iowa City, Iowa, United States
  • Weidner, Jillian, The University of Iowa, Iowa City, Iowa, United States
Background

Diabetic podocytopathy is the most prevalent acquired human podocytopathy. Diabetic podocyte injury initiates before the onset of microalbuminuria and eventually leads to 50% of renal failure in the US. We recognized an enhanced dynein-mediated trafficking of nephrin in diabetic podocyte injury, but the mechanism by which diabetes activates the dynein-drive pathogenesis remains unclear. Bioinformatic analysis predicts that dynein genes are under the regulation of specificity protein 1(SP-1), a transcriptional factor that is modulated by AMP-activated protein kinase (AMPK) under diabetic condition. Therefore, we hypothesize that AMPK/SP-1 guided dynein transcription plays a key role in the early stage of diaberic podocytopathy.

Methods

Dynein expression was examined by real time PCR in podocytes growing under hyperglycemic or normoglycemic conditions, with or without manipulations of AMPK activity (by Compound C or AICAR), or knockdown of SP1 (using siRNA). AMPK activity was reflected by measuring Thr 172 phosphorylation. Live cell imaging and trajectory analysis were performed to study the dynein-dependent trafficking of nephrin to lysosomes or recycling endosomes. Dynein expression, as well as its correlations with AMPK activity and nephrin degradation were investigated in glomeruli isolated from Streptozotocin (STZ)-induced diabetic mice.

Results

1. Upregulated expression of dynein was demonstrated in podocytes with prolonged exposure to high glucose, in which AMPK activity was found to be suppressed. This change could be rescued by the activation of AMPK using AICAR, or knockout of SP1.
2. Knockdown of dynein components that were upregulated by hyperglycemia attenuated the sorting of nephrin from recycling endosome to lysosomal system.
3. The increased expression of dynein and dynein-mediated trafficking of nephrin were verified in STZ-induced diabetic glomerulopathy in mice. These changes correlated with the inhibition of AMPK, ubiquitination degradation and depletion of nephrin, especially the surface nephrin.

Conclusion

Hyperglycemia suppresses AMPK, which in turn disinhibits SP-1 guided transcription of dynein. The increased expression of dynein in diabetes promotes the trafficking of nephrin from recycling pathway to lysosomal degradation system, depletes the surface nephrin, impairs the slit diaphragm and causes diabetic podocytopathy.

Funding

  • Other NIH Support