Expression of nuclear pore complex oxalate binding protein p62 in experimental hyperoxaluria

Proteins are thought to play a major role in stone formation. Oxalate binding protein plays a vital role in the transport of oxalate. This study was aimed at determining whether hyperoxaluria induces the expression of nuclear pore complex oxalate binding protein p62 which has the transport function. Hyperoxaluria was induced in male Wistar rats by feeding 0.75% ethylene glycol in water. The oxalate binding activity of the nuclear pore complex protein increased markedly during experimental hyperoxaluria, whereas nuclear lamina had no binding at all. There was an alteration in the elution profile of the nuclear pore complex oxalate binding protein during the hyperoxaluric condition. The protein was purified and had a molecular weight of 62 kDa (data not shown). The purified protein showed cross-reactivity with the monoclonal antibody (MAb 414) and it showed homogeneity. The expression of this protein (p62) during the hyperoxaluric condition was determined by ELISA and a 3-fold increase was observed when compared to control rats. The increased expression is further confirmed by Western blotting and immunohistochemistry. The increase in p62 protein expression may be either due to increased expression of certain genes or degradation of the cell membrane by oxalate-induced cell injury. Thus, the present study suggests that the increased expression of this protein (p62) may be due to the oxalate induction.