Abstract: SA-PO115

Proteomics of Glomeruli with IgA Nephropathy Reveals the Concomitant Abnormalities of Cytoskeleton in the Podocytes

Session Information

Category: Glomerular

  • 1005 Clinical Glomerular Disorders

Authors

  • Yamaguchi, Hiroki, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
  • Goto, Shin, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
  • Hirao, Yoshitoshi, Niigata University, Niigata, Japan
  • Xu, Bo, Niigata University, Niigata, Japan
  • Yamamoto, Keiko, Niigata University, Niigata, Japan
  • Yamamoto, Suguru, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
  • Kaneko, Yoshikatsu, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
  • Yamamoto, Tadashi, Niigata University, Niigata, Japan
  • Narita, Ichiei, Niigata University Graduate School of Medical and Dental Sciences, Niigata, Japan
Background

Previously, extensive molecular research had been carried out to disclose the mechanism of glomerular injuries in IgAN, however, comprehensive analysis targeted to human glomeruli have been rarely reported. To investigate the molecular network of IgAN, we conducted quantitative proteomic analysis of dissected glomeruli of patients with IgAN.

Methods

We enrolled 12 IgAN patients (mean eGFR, 90.9 ml/min/1.73m2; mean urinary protein, 0.61 g/day; crescentic lesion in kidney biopsy < 10%), and 4 nephrectomized patients due to urological cancers as normal samples (Nor). The glomerular samples were collected by laser microdissection and digested peptides were subjected to LC–MS/MS analysis. Their MS/MS spectral data were searched against Swiss-Prot database. Finally, we performed label-free quantitation using Normalized Spectral Index and extracted proteins which were significantly and distinctively expressed in glomeruli of IgAN or Nor. These proteins were assigned to web-accessible program, DAVID to discover enriched functional related-protein groups.

Results

A total of 3143 proteins were identified with peptide FDR < 1%, and 394 and 563 proteins were selected as expressed differentially in IgAN and Nor respectively. Functional annotation clustering on the glomerular proteins in IgAN ranked several metabolic and biosynthesis pathways as top categories, while that on the glomerular proteins in Nor gave higher enrichment scores to cytoskeletal proteins rich in the podocytes. Especially, the abundance of Actinin-alfa-4, synaptopodin, and RhoA-specific GEF were significantly lower in IgAN. Between the IgAN groups divided by the level of urinary protein (0.5 g/day), the expression of synaptopodin was significantly lower in the group with higher proteinuria.

Conclusion

These results suggest that mesangial inflammation in IgAN could cause the cytoskeletal abnormalities in podocytes, resulting to significant proteinuria and glomerular injury.