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 re traction of glomerular epithelial cell foot processes and glomerular epithe lial cell detachment, it was hypothesized that PAN might alter the contacts between these cells and the glomerular basement membrane. The major integr in expressed by glomerular epithelial cells is alpha3 beta1, which mediates attach ment of these cells to extracellular matrix proteins including type IV collagen. T-SV 40 immortalized human glomerular epithelial cells were u sed to study PAN's effects on alpha3 beta1 expression, as well as that of p odocalyxin and the slit diaphragm component ZO-1. Glomerular epithelial cel ls were seeded into plastic flasks and allowed to attach and proliferate fo r 48 h. The cells were then incubated for another 48 h in media containing 0, 0,5, or 5.0 mug/ml PAN. PAN exposure resulted in dose-dependent decrease s 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 g lomerular epithelial cells to type IV collagen. PAN did not affect ZO-1 pro tein expression. Treatment with PAN increased the expression of podocalyxin at the protein and mRNA levels. Reduced glomerular epithelial cell express ion of alpha3 beta1 integrins and impaired adhesion to type IV collagen may contribute to the glomerular epithelial cell detachment from glomerular ba sement membrane seen in the PAN nephrosis model.