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Inhibitory Act of Selenoprotein P on Cu+/Cu2+-Induced Tau Aggregation and Neurotoxicity

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journal contribution
posted on 20.10.2014, 00:00 by Xiubo Du, Youbiao Zheng, Zhi Wang, Yijing Chen, Rui Zhou, Guoli Song, Jiazuan Ni, Qiong Liu
Alzheimer’s disease (AD) is a neurodegenerative disorder that is characterized by peptide and protein misfolding and aggregation, in part due to the presence of excess metal ions such as copper. Aggregation and cytotoxicity of amyloid-β (Aβ) peptide with copper ion have been investigated extensively; however, the effects of metalation on tau are less known. Here, we presented the effects of Cu+ and Cu2+ on aggregation and neurotoxicity of the second repeat unit of the microtubule-binding domain of tau (tau-R2). Tau-R2 was demonstrated to bind 0.44 Cu2+ and 0.34 Cu+ per monomer with dissociation constants of 1.1 nM and 0.2 pM, respectively. Copper in both oxidation states stimulated the aggregation, ROS production, and neuronal cytotoxicity of tau-R2. We showed that copper-associated tau-R2 aggregates, decreased protein levels of microtubule-associated protein 2 (MAP-2), and synaptophysin in the primarily cultured cortical neurons, reduced mitochondrial density and mobility in the axon and, as a consequence, impaired the growth and probably also the function of neurons. Previously, we reported that the His-rich domain of selenoprotein P (SelP-H) inhibited metal-induced aggregation and toxicity of Aβ, due to its metal chelation ability. Here we demonstrated that SelP-H not only inhibited copper-mediated tau aggregation but also interfered with the ongoing aggregation and reversed the already formed aggregates. More intriguing, SelP-H significantly attenuated Cu2+/Cu+-tau-R2-induced intracellular ROS production and the impairments of synapse and mitochondrial movement in neurons. This work implies that the surface-exposed His-rich domain of SelP makes it capable of modulating Cu+/Cu2+-mediated aggregation and neurotoxicity of both Aß and tau and may play important roles in the prevention of AD progression.