Puromycin aminonucleoside suppresses integrin expression in cultured glomerular epithelial cells.

Puromycin aminonucleoside (PAN)-induced nephrosis is a well-described model of human idiopathic nephrotic syndrome, but the mechanism of PAN's effect is not completely understood. Because PAN injection into rats results in retraction of glomerular epithelial cell foot processes and glomerular epithelial cell detachment, it was hypothesized that PAN might alter the contacts between these cells and the glomerular basement membrane. The major integrin expressed by glomerular epithelial cells is alpha3beta1, which mediates attachment of these cells to extracellular matrix proteins including type IV collagen. T-SV 40 immortalized human glomerular epithelial cells were used to study PAN's effects on alpha3beta1 expression, as well as that of podocalyxin and the slit diaphragm component ZO-1. Glomerular epithelial cells were seeded into plastic flasks and allowed to attach and proliferate for 48 h. The cells were then incubated for another 48 h in media containing 0, 0.5, or 5.0 microg/ml PAN. PAN exposure resulted in dose-dependent decreases in alpha3 and beta1 expression, both at the protein level and at the mRNA level. This was accompanied by a significant decrease in the adhesion of glomerular epithelial cells to type IV collagen. PAN did not affect ZO-1 protein expression. Treatment with PAN increased the expression of podocalyxin at the protein and mRNA levels. Reduced glomerular epithelial cell expression of alpha3beta1 integrins and impaired adhesion to type IV collagen may contribute to the glomerular epithelial cell detachment from glomerular basement membrane seen in the PAN nephrosis model.