Abstract: SA-PO297

Reduced Proteoglycans in the Kidney Causes Both Tubule and Glomerular Abnormalities

Session Information

Category: Cell Biology

  • 204 Extracellular Matrix Biology, Fibrosis, Cell Adhesion

Authors

  • Poudel, Nabin, Oklahoma State University, Stillwater, Oklahoma, United States
  • Munteanu, Maria Cristina, Oklahoma State University, Stillwater, Oklahoma, United States
  • Silasi-Mansat, Robert, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States
  • Lupu, Florea, Oklahoma Medical Research Foundation, Oklahoma City, Oklahoma, United States
  • Hinsdale, Myron, Oklahoma State University, Stillwater, Oklahoma, United States
Background

Most cells produce some form of proteoglycan(s). The initial assembly of glycosaminoglycan (GAG) on the core protein of proteoglycans(PG) requires the transfer of a xylose to a designated serine. The enzyme responsible for this is xylosyltransferase and it exists in two isoforms as xylosyltransferase 1(XylT1) and 2 (XylT2). The latter is ubiquitously expressed in many organs suggesting a significant biochemical role of XylT2 dependent proteoglycans in these organs. In our XylT2 knock-out mice (Xylt2-/- mice), substantial XylT activity remains in the kidney due to the remaining XylT1 activity. However, considerable renal abnormalities still occur including glomerular basement membrane changes, fibrosis, and tubule dilation. Our previous findings in Xylt2-/- mice established that proteoglycans are important in cyst development in the liver. Considering our findings in the Xylt2-/- mice and that reduced proteoglycans occurs in many different diseases affecting the kidney (e.g. polycystic kidney disease, PKD), we hypothesize that GAG levels have a modifying role in kidney function. Notably, PKD patients can develop proteinuria indicating a much poorer long-term prognosis.

Methods

Blood Urea Nitrogen (BUN) was measured from Xylt2-/- mice. Western blotting was performed on urine of Xylt2-/- mice to detect proteinuria. Transmission Electron Microscopy (TEM) was used to evaluate the structural changes in glomerular basement membrane and kidney tubule. In addition, TEM was performed on kidneys from mice injected with polyethylenemine (PEI) to measure anionic sites in the GBM.

Results

Xylt2-/- mice have increased BUN, proteinuria, and, in aged mice, renal failure. Investigations also show that additional changes occur ultrastructurally in the glomerular basement membrane including decreases in anionic charge. Furthermore, tubule structure is also impacted indicating tubule dysfunction.

Conclusion

The findings in the XylT2 deficient kidneys indicates that XylT2-dependent glycosaminoglycan (GAG) assembly onto core proteins is important in nephron homeostasis. Our analyses suggest that one source of the proteinuria could be reduced renal proteoglycans.

Funding

  • NIDDK Support