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Abstract: PO1718

Nephronectin Expression Is Controlled by the Non-Canonical TGF-β Pathway in Podocytes

Session Information

Category: Glomerular Diseases

  • 1204 Podocyte Biology

Authors

  • Sopel, Nina, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
  • Ohs, Alexandra, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
  • Schiffer, Mario, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
  • Müller-Deile, Janina, Universitatsklinikum Erlangen Medizinische Klinik 4 Nephrologie und Hypertensiologie, Erlangen, Bayern, Germany
Background

Within the glomerulus, podocytes, glomerular endothelial cells (GEC) and the glomerular basement membrane (GBM) build the glomerular filtration barrier. Extracellular matrix (ECM) of the GBM is mainly composed of proteins synthesized by GECs and podocytes.
Our interest focuses on nephronectin (NPNT), an ECM protein mainly produced by podocytes. Recently, it has been described that NPNT expression patterns vary in different glomerular diseases. For example, in focal segmental glomerulosclerosis (FSGS) and membranous glomerulonephropathy (MGN) NPNT expression was decreased compared to healthy controls, while it was increased in diabetic nephropathy (DN). In addition, transforming growth factor beta (TGFβ) is able to down-regulate NPNT on both mRNA and protein level.
Our aim is to further analyze this TGFβ-mediated regulation of NPNT in human podocytes.

Methods

Immortalized human podocytes were differentiated for 10 to 12 days at 37°C and pre-incubated with inhibitors for components of the canonical and the non-canonical TGFβ signaling pathway with subsequent culture in the presence or absence of TGFβ. We used cell culture supernatants for ELISA, as well as cell lysates for qPCR and western blot analyses.

Results

While treating differentiated immortalized human podocytes with TGFβ decreased NPNT on both mRNA and protein level, we observed that inhibition of single components of the TGFβ pathway did not alter NPNT mRNA expression and excretion. On protein level, we noted no change after blockade of either Smad2 or Smad3 under baseline conditions. However, TGFβ was still able to decrease NPNT expression when canonical pathway components were inhibited, suggesting a minor role for this pathway in NPNT regulation via TGFβ. If single components of the non-canonical pathway were blocked, we observed an increase in NPNT protein expression, which was not further altered by TGFβ addition.

Conclusion

Taken together, our data suggest that in podocytes NPNT expression is fine-tuned via the non-canonical TGFβ pathway with additional regulation on the post-translational level.

Funding

  • Government Support – Non-U.S.