Comparison of heparan sulfate proteoglycans from equine and human glomerular basement membranes.

This article presents a comparative study of heparan sulfate proteoglycans (proteins that contain a large number of carbohydrate chain) from human and equine glomerular basement membranes. The research shows that while the structures of these proteins from both species are quite similar, there are significant differences in the core proteins.

Methodology

• The researchers extracted proteoglycans from both human and equine glomerular basement membranes (GBM), which were purified using ion-exchange chromatography and gel filtration.
• These glycoconjugates were found to have an apparent molecular mass of 200-400 kDa, composed of 75% protein and 25% glycosaminoglycan.
• The dominant saccharide chain identified in both proteoglycan preparations was heparan sulfate (HS), following glycosidase and HNO2 treatment and the investigation of amino sugar and sulfate compositions.

Results

• The researchers used hydrolysis with trifluoromethanesulfonic acid to yield core proteins that showed similar molecular masses in human and equine samples, with sizes of about 160 and 120 kDa.
• HS chains displayed an apparent molecular mass of 18 kDa. Results gathered from both heparitinase digestion and HNO2-treatment indicated that sulfate groups were clustered in the distal part of HS side chains.
• Peptide mapping conducted after the digestion of human and equine HS proteoglycans, using trypsin, clostripain or V8 protease, revealed large differences between the two.

Immunological Findings

• Antibodies developed against the HSPGs, polyclonal antisera, reacted against the core proteins. Both HSPG preparations and the antibodies against them showed approximately 40% cross-reactivity.
• About 50% of the monoclonal antibodies developed against one HSPG preparation showed a reaction with both HSPG preparations.
• In experiments using indirect immunofluorescence on kidney sections from horses, humans, and various other mammals, the polyclonal antisera demonstrated intense and consistent staining of all basement membranes.

Conclusion

• The biochemical and immunological data gathered indicates that although the HSPGs from equine and human glomerular basement membranes have comparable structures, there are substantial differences in the core proteins of each.