Effect of puromycin aminonucleoside on HSPG core protein content of glomerular epithelial cells

It has been suggested that the glomerular basement membrane heparan sulfate proteoglycan (HSPG) is an important determinant of the glomerular permselectivity barrier. Derangements in the content of basement membrane heparan sulfate have been implicated in alterations in glomerular permselectivity seen in many glomerular diseases such as aminonucleoside nephrosis. The cellular origin and metabolism of the glomerular basement membrane HSPG have not been studied in detail. We have detected the expression of the proteoglycan by cloned glomerular visceral epithelial cells of the rat by employing a specific antibody against the core protein of HSPG isolated from the rat glomerular basement membrane. These findings suggest that in the rat in vivo glomerular visceral epithelial cells are one source of heparan sulfate present in the glomerular basement membrane. The effect of puromycin aminonucleoside (PAN) on the HSPG core protein content of the cloned glomerular epithelial cells was studied. By a quantitative immunoperoxidase method, the aminonucleoside caused a 28% reduction in the core protein content of the epithelial cells (P less than 0.01) following 72 h of incubation. However, the content of Heymann nephritis-related antigen, Fx1A was unchanged. Studies employing [3H]leucine incorporation showed that PAN was a weak inhibitor of de novo protein synthesis at 24 h of incubation, with complete recovery at 48 and 72 h. These data suggest that PAN effect on heparan sulfate core protein cannot be attributed to generalized inhibition of protein synthesis. The precise mechanism underlying the aminonucleoside effect on heparan sulfate core protein remains to be elucidated.