Xylosylated-proteoglycan-induced Golgi alterations

The effect of p-nitrophenyl β-D-xylopyranoside on the Golgi apparatus and proteoglycans (PG) of the renal glomerulus was investigated in an isolated kidney organ perfusion system and monitored by utilizing [³⁵S]sulfate as the PG precursor. By electron microscopy, a selective intracytoplasmic vesiculization of Golgi apparatus of visceral epithelium was observed in the β-xyloside-treated kidneys. Electron microscopic autoradiography revealed most grains localized to the intracytoplasmic Golgi-derived vesicles, while very few grains were associated with the extracellular matrix membranes. Biochemically, a 2.3-fold increase in cellular matrix and a reduction by a factor of 1.7 in extracellular matrix of [³⁵S]sulfate incorporation was observed. Besides a larger macromolecular form (K(avg) = 0.25; M(r) = 130,000), lower molecular weight PGs were recovered in the cellular (K(avg) = 0.46, M(r) = 30,000) and matrical (K(avg) = 0.42, M(r) = 45,000) compartments after xyloside treatment. The xyloside treatment increased the incorporated radioactivity, mostly included in free glycosaminoglycans and small PGs, in the media fraction by 3.8-fold. These data indicate that xyloside induces a dramatic imbalance in the de novo-synthesized PGs of cellular and extracellular compartments and that cellular accumulation of xylosylated (sulfated) PGs selectively alters the Golgi apparatus of the glomerular epithelial cell, the cell that actively synthesizes PGs.