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Glycosaminoglycan and proteoglycan inhibit the depolymerization of beta2-microglobulin amyloid fibrils in vitro
Itaru Yamaguchi1, Hironori Suda, Naoki Tsuzuike
1Department of Pathology, Fukui Medical University, Fukui, Japan.
Background:
Although several kinds of evidence suggest that glycosaminoglycans (GAGs) and proteoglycans (PGs) may contribute to the development of beta2-microglobulin-related (Abeta2m) amyloidosis, the precise roles of these molecules for the development of Abeta2m amyloidosis are poorly understood.
Methods:
We investigated the effects of GAGs and PGs on the depolymerization of Abeta2m amyloid fibrils at a neutral pH, as well as on the formation of the fibrils at an acidic pH in vitro, using fluorescence spectroscopy with thioflavin T and electron microscopy.
Results:
Depolymerization of Abeta2m amyloid fibrils at pH 7.5 at 37 degrees C was inhibited dose-dependently by the presence of some GAGs (heparin, dermatan sulfate, or heparan sulfate) or PGs (biglycan, decorin, or keratan sulfate proteoglycan). Electron microscopy revealed that a significant amount of Abeta2m amyloid fibrils remained in the reaction mixture with some lateral aggregation. Second, when monomeric beta2m was incubated with aggrecan, biglycan, decorin, or heparin at pH 2.5 at 37 degrees C for up to 21 days, the thioflavin T fluorescence increased depending on dose and time. Electron microscopy revealed the formation of rigid and straight fibrils similar to Abeta2m amyloid fibrils in beta2m incubated with biglycan for 21 days.
Conclusion:
These results suggest that some GAGs and PGs could enhance the deposition of Abeta2m amyloid fibrils in vivo, possibly by binding directly to the surface of the fibrils and stabilizing the conformation of beta2m in the fibrils, as well as by acting as a scaffold for the polymerization of beta2m into the fibrils.
Insights
Glycosaminoglycans (GAGs) and proteoglycans (PGs) inhibit beta2-microglobulin (Abeta2m) amyloid fibril depolymerization and promote fibril formation. These findings suggest GAGs and PGs may enhance Abeta2m amyloidosis in vivo.
Area of Science:
- Biochemistry
- Molecular Biology
- Medical Research
Background:
- Beta2-microglobulin (Abeta2m) amyloidosis is a growing concern.
- The roles of glycosaminoglycans (GAGs) and proteoglycans (PGs) in Abeta2m amyloidosis are not fully understood.
Purpose of the Study:
- To investigate the effects of GAGs and PGs on Abeta2m amyloid fibril depolymerization and formation.
- To elucidate the molecular mechanisms underlying GAG and PG involvement in Abeta2m amyloidosis.
Main Methods:
- In vitro experiments using fluorescence spectroscopy with thioflavin T.
- Electron microscopy to visualize amyloid fibril structures.
- Investigated fibril depolymerization at neutral pH and formation at acidic pH.
Main Results:
- GAGs (heparin, dermatan sulfate, heparan sulfate) and PGs (biglycan, decorin, keratan sulfate proteoglycan) dose-dependently inhibited Abeta2m amyloid fibril depolymerization.
- Electron microscopy confirmed the presence of remaining Abeta2m fibrils with lateral aggregation.
- Monomeric beta2-microglobulin incubated with aggrecan, biglycan, decorin, or heparin at acidic pH showed increased thioflavin T fluorescence, indicating enhanced fibril formation.
Conclusions:
- GAGs and PGs may enhance Abeta2m amyloid fibril deposition in vivo.
- These molecules might stabilize beta2-microglobulin conformation and act as scaffolds for polymerization.
- Further research is needed to fully understand the therapeutic implications.