Biochemical and Biophysical Research Communications, Vol.402, No.2, 247-251, 2010
Glycosaminoglycans enhance the fibrillation propensity of the beta(2)-microglobulin cleavage variant - Delta K58-beta(2)m
Dialysis related amyloidosis (DRA) is a serious complication to long-term hemodialysis treatment which causes clinical symptoms such as carpal tunnel syndrome and destructive arthropathies. The disease is characterized by the assembly and deposition of beta(2)-microglobulin (beta(2)m) predominantly in the musculoskeletal system, but the initiating events leading to beta(2)m amyloidogenesis and the molecular mechanisms underlying amyloid fibril formation are still unclear. Glycosaminoglycans (GAGS) and metal ions have been shown to be related to the onset of protein aggregation and to promote de novo fiber formation. In this study, we show that fibrillogenesis of a cleavage variant of beta(2)m, Delta K58-beta(2)m, which can be found in the circulation of hemodialysis patients and is able to fibrillate at near-physiological pH in vitro, is affected by the presence of copper ions and heparan sulfate. It is found that the fibrils generated when heparan sulfate is present have increased length and diameter, and possess enhanced stability and seeding properties. However, when copper ions are present the fibrils are short, thin and less stable, and form at a slower rate. We suggest that heparan sulfate stabilizes the cleaved monomers in the early aggregates, hereby promoting the assembly of these into fibrils, whereas the copper ions appear to have a destabilizing effect on the monomers. This keeps them in a structure forming amorphous aggregates for a longer period of time, leading to the formation of spherical bodies followed by the assembly of fibrils. Hence, the in vivo formation of amyloid fibrils in DRA could be initiated by the generation of Delta K58-beta(2)m which spontaneously aggregate and form fibrils. The fibrillogenesis is enhanced by the involvement of GAGs and/or metal ions, and results in amyloid-like fibrils able to promote the de novo formation of beta(2)m amyloid by a scaffold mechanism. (C) 2010 Elsevier Inc. All rights reserved.