D-Ribose glycates β2-microglobulin to form aggregates with high cytotoxicity through a ROS-mediated pathway

beta(2)-Microglobulin (beta M-2) modified with advanced glycation end products (AGEs) is a major component of the amyloid deposits in hemodialysis-associated amyloidosis (HAA). However, the effect of glycation on the misfolding and aggregation of beta M-2 has not been studied so far. Here we examine the molecular mechanism of aggregate formation of HAA-related ribosylated beta M-2 in vitro. We find that the glycating agent isribose interacts with human beta M-2 to generate AGEs that form aggregates in a time-dependent manner. Ribosylated beta M-2 molecules are highly oligomerized compared with unglycated beta M-2, and have granular morphology. Furthermore, such ribosylated beta M-2 aggregates show significant cytotoxicity to both human SH-SY5Y neuroblastoma and human foreskin fibroblast FS2 cells and induce intracellular reactive oxygen species (ROS). Presence of the antioxidant N-acetylcysteine (1.0 mM) attenuated intracellular ROS and prevented cell death induction in both SH-SY5Y and FS2 cells, indicating that the cytotoxicity of ribosylated beta M-2 aggregates depends on a ROS-mediated pathway in both cell lines. In other words, D-ribose reacts with beta M-2 and induces the ribosylated protein to form granular aggregates with high cytotoxicity through a ROS-mediated pathway. These findings suggest that ribosylated beta M-2 aggregates could contribute to the dysfunction and death of cells and could play an important role in the pathogenesis of beta M-2-associated diseases such as HAA. (C) 2011 Elsevier Ireland Ltd. All rights reserved.