Abstract: TH-PO1070

Structural Alteration of Urinary Tamm Horsfall Protein under Hyperoxaluric Conditions in Rats: Role of Calnexin, a Glycoprotein Chaperone

Session Information

Category: Mineral Disease

  • 1204 Mineral Disease: Nephrolithiasis

Authors

  • Bhardwaj, Rishi, Panjab University, Chandigarh, India
  • Bhardwaj, Ankita, Panjab University, Chandigarh, India
  • Tandon, Chanderdeep, Amity University, Noida, Uttar Pradesh, India
  • Dhawan, Devinder Kumar, Panjab University, Chandigarh, India
  • Kaur, Tanzeer, Panjab University, Chandigarh, India
Background

Tamm Horsfall Protein (THP), a urinary glycoprotein has been studied extensively for its involvement in the progression or regression of renal stone formation. Also, some studies have pointed out the abnormality in structural conformation and glycosylation as the root cause for the altered nature of THP. Calnexin, an ER resident chaperone, deals with the proper folding of glycoproteins in order to ensure their structural and functional entity. Therefore, study was carried out to decipher the role of calnexin and THP under hyperoxaluric environment in rat model mimicing renal stone condition, if any.

Methods

Rats were randomly divided into four groups: control, hyperoxaluric groups i.e. ethylene glycol alone, ethylene glycol with ammonium chlroide and hydroxy-l-proline, respectively. After hyperoxaluric induction, urine from the rats was collected for THP isolation. Rats were then sacrificed and kidneys were removed for further investigations. Methods employed to carry out the investigations included protein expression analysis via Western Blot and Immunohistochemistry and gene expression analysis by mRNA studies. Fourier Tranform Infrared Spectroscopy and hydrophobicity analysis of isolated THP were carried out in order to demonstrate any structural changes. Sialic acid content was estimated both in renal tissues and isolated THP.

Results

Studies revealed a significant increase in the expression of calnexin as well as THP in the renal tissue of all the hyperoxaluric groups at both protein and gene level. Moreover, absence of peak at 1462 cm-1 in the FTIR spectrum of THP was also demonstrated by the hyperoxaluric animals with significant alteration in the extent of hydrophobicity. Also, sialic acid content of renal tissues and isolated THP was found to be significantly lowered in the animals subjected to hyperoxaluric insult.

Conclusion

Above mentioned finding suggests a possiblity that alteration in the working environment of glycoprotein chaperone, calnexin can greatly modulate the role of THP by regulating its structural, conformational and functional aspects. This could pave a path towards the development of novel therapeutic approaches targeting chaperone activity as well as stress thus generated under renal stone ailment.

Funding

  • Government Support - Non-U.S.