Heparin strongly enhances the formation of beta2-microglobulin amyloid fibrils in the presence of type I collagen.
The tissue specificity of fibrillar deposition in dialysis-related amyloidosis is most likely associated with the peculiar interaction of beta2-microglobulin (beta2-m) with collagen fibers. However, other co-factors such as glycosaminoglycans might facilitate amyloid formation. In this study we have investigated the role of heparin in the process of collagen-driven amyloidogenesis. In fact, heparin is a well known positive effector of fibrillogenesis, and the elucidation of its potential effect in this type of amyloidosis is particularly relevant because heparin is regularly given to patients subject to hemodialysis to prevent blood clotting. We have monitored by atomic force microscopy the formation of beta2-m amyloid fibrils in the presence of collagen fibers, and we have discovered that heparin strongly accelerates amyloid deposition. The mechanism of this effect is still largely unexplained. Using dynamic light scattering, we have found that heparin promotes beta2-m aggregation in solution at pH 6.4. Morphology and structure of fibrils obtained in the presence of collagen and heparin are highly similar to those of natural fibrils. The fibril surface topology, investigated by limited proteolysis, suggests that the general assembly of amyloid fibrils grown under these conditions and in vitro at low pH is similar. The exposure of these fibrils to trypsin generates a cleavage at the C-terminal of lysine 6 and creates the 7-99 truncated form of beta2-m (DeltaN6beta2-m) that is a ubiquitous constituent of the natural beta2-m fibrils. The formation of this beta2-m species, which has a strong propensity to aggregate, might play an important role in the acceleration of local amyloid deposition.
Department of Physics, University of Genoa, Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia (CNISM), I-16146 Genoa, Italy.
Annalisa
A
Relini
Silvia
S
De Stefano
Silvia
S
Torrassa
Ornella
O
Cavalleri
Ranieri
R
Rolandi
Alessandra
A
Gliozzi
Sofia
S
Giorgetti
Sara
S
Raimondi
Loredana
L
Marchese
Laura
L
Verga
Antonio
A
Rossi
Monica
M
Stoppini
Vittorio
V
Bellotti
D000682:Amyloid / Q000737:chemistry* / Q000378:metabolism / Q000648:ultrastructure; D000686:Amyloidosis / Q000209:etiology / Q000378:metabolism; D000818:Animals; D001777:Blood Coagulation / Q000187:drug effects; D002417:Cattle; D024042:Collagen Type I / Q000737:chemistry* / Q000378:metabolism; D006493:Heparin / Q000008:administration & dosage / Q000009:adverse effects / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008027:Light; D018625:Microscopy, Atomic Force; D006435:Renal Dialysis / Q000009:adverse effects; D012542:Scattering, Radiation; D014357:Trypsin / Q000737:chemistry; D001613:beta 2-Microglobulin / Q000737:chemistry* / Q000378:metabolism
D000682:Amyloid; D024042:Collagen Type I; D001613:beta 2-Microglobulin; D006493:Heparin; D014357:Trypsin