Sulfated and nonsulfated glycosaminoglycans and glycopeptides are synthesized by kidney in vivo and incorporated into glomerular basement membranes

Abstract

Sulfated and nonsulfated glycosaminoglycans and glycopeptides are synthesized by kidney in vivo and incorporated into glomerular basement membranes ([35S] radioactivity and 10-15% of the total 3H radioactivity incorporated into cortex, glomeruli, or GBM was found in the GAG fraction, and the remainder (--'32% of 35S radioactivity and 85-90% of the 3H radioactivity) was found in glycopeptide fractions. Treatment of GAG fractions isolated from the three sources (cortex, glomeruli, and GBM) with nitrous acid (which degrades heparan sulfates) indicated that the majority (85%, 65%, and 87%) of the 3S radioactivity as well as the majority (60%, 50%, and 91%) of the 3H radioactivity from all three sources was degraded by this treatment. When nitrous acid-resistant GAG from GBM were subjected to digestion with Streptom ces hyaluronidase (which degrades hyaluronic acid), --6% of the H-labeled material was sensitive to this treatment. The remaining 35S-and 3H-labeled GAG isolated from GBM were digested with chondro-

Monoclonal Antibodies to Human Glomerular Cells: A Marker for Glomerular Epithelial Cells

“…However, prolonged digestion with neuraminidase, an enzyme which specifically removes sialoglycoproteins [27,40,43], did not affect label ling with PHM 5, although such treatment is reported to have removed all three otherwise similar antigens recently purified from the glomerular epithelial sialoprotein coat of rats [34]. Similarly, the use of nitrous acid oxidation to re move heparin and heparan sulphate had no effect on label ling, despite the presence of large amounts of heparan sulphate throughout the GBM [10,25] and possibly on glomerular epithelial cells [44], The two other related GAG, chondroitin sulphate and hyaluronic acid, also appear un likely to be involved; absorption with chondroitin sulphate B (dermatan sulphate) had no effect, nor did PHM 5 bind to interstitial cells of kidney papillae or the luminal sur face of Henle's loop and distal tubules which are all sites suggested to contain chondroitin sulphate and hyaluronic acid [27,28,33]. In addition, fibronectin, a glycoprotein present in mesangial areas and within the GBM [11,37], did not absorb PHM 5, nor does PHM 5 appear to be directed against the amyloid P component, since absorp tion with GBM and serum had no effect [12], Finally, the failure of absorption by human milk, and its different renal distribution, namely glomerular but not tubular epithelial cells, indicates PHM 5 is not directed against the recently described epithelial membrane antigen [21].…”

Effect of Lymphokine from Nephrotic Peripheral Blood Mononuclear Cells on Catabolism of Rat Glomerular Basement Membrane Sulfated Compounds

“…It is currently accepted that in experiments in vivo, in vitro and in situ, heparan sulfate is the major glomerular basement membrane pro teoglycan synthesized in the rat [21]. The bulk of sulfate-35 will label this proteoglycan while smaller amounts will be incorporated into chondroitin, dermatan sulfate and less amounts into entactin, a glycoprotein [7,[27][28][29].…”

“…We have previously reported that peripheral blood mononuclear cells (PBMC) from IMLNS patients secrete a lymphokine which alters the metabolism of the glomerular basement membrane (GBM) sulfated compounds [4][5][6], Heparan sulfate, a sulfated glycosaminoglycan, is the most important component of the GBM anionic sites [7], In creased catabolism of the GBM sulfated compound may result in a decreased concentration of heparan sulfate in the GBM which may be the cause of proteinuria in IMLNS.…”

Effect of Prednisone on Nephrotic Peripheral Blood Mononuclear Cell Mediated Increase in ³⁵Sulfate Uptake in Rat Glomerular Basement Membrane

“…The GBM is an extracellular matrix consisting of collagenous and noncollagenous glycoconjugates assem bled to provide filtration barriers and substrata for cell attachment and orientation [9], A number of macromole cules containing sulfate groups have been characterized, including proteoglycans and glycoproteins [5]. Proteo glycans have the greatest negative charge among these known macromolecules [10], In the GBM they are located in the lamina rarae, forming a regular lattice-like network of anionic sites.…”

“…We have observed an increased incorporation o f35sulfate in the rat GBM after glomeruli have been cocultured with PBMC from IMLNS patients in relapse. Sulfate groups are an important source of negative charges in the GBM heparan sulfate (the main component of the lamina rarae interna anionic sites) [5], Because of that, a change in the metabolism of the GBM sulfated compounds may have pathogenic significance.…”