title: The molecular mechanism for human metallothionein-3 to protect against the neuronal cytotoxicity of Aβ(1-42) with Cu ions.
abstract: Aggregation and cytotoxicity of Aβ with redox-active metals in neuronal cells have been implicated in the progression of Alzheimer disease. Human metallothionein (MT) 3 is highly expressed in the normal human brain and is downregulated in Alzheimer disease. Zn(7)MT3 can protect against the neuronal toxicity of Aβ by preventing copper-mediated Aβ aggregation, abolishing the production of reactive oxygen species (ROS) and the related cellular toxicity. In this study, we intended to decipher the roles of single-domain proteins (α/β) and the α-β domain-domain interaction of Zn(7)MT3 to determine the molecular mechanism for protection against the neuronal cytotoxicity of Aβ(1-42) with copper ions. With this in mind, the α and β single-domain proteins, heterozygous β(MT3)-α(MT1), and a linker-truncated mutant ∆31-34 were prepared and characterized. In the presence/absence of various Zn(7)MT3 proteins, the Aβ(1-42)-Cu(2+)-mediated aggregation, the production of ROS, and the cellular toxicity were investigated by transmission electron microscopy, ROS assay by means of a fluorescent probe, and SH-SY5Y cell viability, respectively. The β domain cannot abolish Aβ(1-42)-Cu(2+)-induced aggregation, and neither the β domain nor the α domain can quench the production of ROS because of the redox cycling of Aβ-Cu(2+). Similarly to wild-type Zn(7)MT3, the heterozygous β(MT3)-α(MT1) possesses the characteristic of alleviating Aβ(1-42) aggregation and oxidative stress to neuronal cells. Therefore, the two domains through the linker Lys-Lys-Ser form a cooperative unit, and each of them is indispensable in conducting its bioactivity. The α domain plays an important role in modulating the stability of the metal-thiolate cluster, and the α-β domain-domain interaction through the linker is critical for its protective role in the brain.
authors.affiliation: Institutes of Biomedical Sciences, Fudan University, Shanghai 200433, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Luo
authors.forename: Yuxia
authors.initials: Y
authors.lastname: Xu
authors.forename: Qingui
authors.initials: Q
authors.lastname: Bao
authors.forename: Zhichun
authors.initials: Z
authors.lastname: Ding
authors.forename: Cuiqing
authors.initials: C
authors.lastname: Zhu
authors.forename: Zhong-Xian
authors.initials: ZX
authors.lastname: Huang
authors.forename: Xiangshi
authors.initials: X
authors.lastname: Tan
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D003300:Copper / Q000633:toxicity*; D006801:Humans; D000090023:Metallothionein 3; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000378:metabolism*; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism*; D055503:Protein Multimerization / Q000187:drug effects; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary; D017382:Reactive Oxygen Species / Q000378:metabolism
chemical_list: D016229:Amyloid beta-Peptides; D000090023:Metallothionein 3; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D017382:Reactive Oxygen Species; C075222:amyloid beta-protein (1-42); D003300:Copper