Relini Annalisa, Canale Claudio, De Stefano Silvia, Rolandi Ranieri, Giorgetti Sofia, Stoppini Monica, Rossi Antonio, Fogolari Federico, Corazza Alessandra, Esposito Gennaro, Gliozzi Alessandra, Bellotti Vittorio
Department of Physics, University of Genoa, Via Dodecaneso 33, I-16146 Genoa, Italy.
J Biol Chem. 2006 Jun 16;281(24):16521-9. doi: 10.1074/jbc.M513827200. Epub 2006 Apr 6.
Dialysis-related amyloidosis is characterized by the deposition of insoluble fibrils of beta(2)-microglobulin (beta(2)-m) in the musculoskeletal system. Atomic force microscopy inspection of ex vivo amyloid material reveals the presence of bundles of fibrils often associated to collagen fibrils. Aggregation experiments were undertaken in vitro with the aim of reproducing the physiopathological fibrillation process. To this purpose, atomic force microscopy, fluorescence techniques, and NMR were employed. We found that in temperature and pH conditions similar to those occurring in periarticular tissues in the presence of flogistic processes, beta(2)-m fibrillogenesis takes place in the presence of fibrillar collagen, whereas no fibrils are obtained without collagen. Moreover, the morphology of beta(2)-m fibrils obtained in vitro in the presence of collagen is extremely similar to that observed in the ex vivo sample. This result indicates that collagen plays a crucial role in beta(2)-m amyloid deposition under physiopathological conditions and suggests an explanation for the strict specificity of dialysis-related amyloidosis for the tissues of the skeletal system. We hypothesize that positively charged regions along the collagen fiber could play a direct role in beta(2)-m fibrillogenesis. This hypothesis is sustained by aggregation experiments performed by replacing collagen with a poly-L-lysine-coated mica surface. As shown by NMR measurements, no similar process occurs when poly-L-lysine is dissolved in solution with beta(2)-m. Overall, the findings are consistent with the estimates resulting from a simplified collagen model whereby electrostatic effects can lead to high local concentrations of oppositely charged species, such as beta(2)-m, that decay on moving away from the fiber surface.
透析相关淀粉样变性的特征是β2-微球蛋白（β2-m）的不溶性纤维在肌肉骨骼系统中沉积。对体外淀粉样物质进行原子力显微镜检查发现存在通常与胶原纤维相关的纤维束。为了重现生理病理纤维化过程，进行了体外聚集实验。为此，采用了原子力显微镜、荧光技术和核磁共振。我们发现，在与炎症过程中关节周围组织相似的温度和pH条件下，β2-m在纤维状胶原蛋白存在的情况下发生纤维形成，而没有胶原蛋白则无法获得纤维。此外，在体外有胶原蛋白存在的情况下获得的β2-m纤维的形态与在体外样品中观察到的极其相似。这一结果表明，胶原蛋白在生理病理条件下β2-m淀粉样沉积中起关键作用，并为透析相关淀粉样变性对骨骼系统组织的严格特异性提供了解释。我们假设沿胶原纤维的带正电区域可能在β2-m纤维形成中起直接作用。用聚-L-赖氨酸包被的云母表面替代胶原蛋白进行的聚集实验支持了这一假设。如核磁共振测量所示，当聚-L-赖氨酸与β2-m溶解在溶液中时，不会发生类似过程。总体而言，这些发现与简化胶原模型得出的估计结果一致，即静电效应可导致带相反电荷的物质（如β2-m）在局部高浓度存在，这些物质在远离纤维表面时会衰减。
