title: Hsp27 suppresses the Cu(2+)-induced amyloidogenicity, redox activity, and cytotoxicity of α-synuclein by metal ion stripping.
abstract: Aberrant copper homeostasis and oxidative stress have critical roles in several neurodegenerative diseases. Expression of heat-shock protein 27 (Hsp27) is elevated under oxidative stress as well as upon treatment with Cu(2+), and elevated levels of Hsp27 are found in the brains of patients with Alzheimer and Parkinson diseases. We demonstrate, using steady-state and time-resolved fluorescence spectroscopy as well as isothermal titration calorimetry studies, that Hsp27 binds Cu(2+) with high affinity (Kd ~10(-11) M). Treating IMR-32 human neuroblastoma cells with Cu(2+) leads to upregulation of endogenous Hsp27. Further, overexpression of Hsp27 in IMR-32 human neuroblastoma cells confers cytoprotection against Cu(2+)-induced cell death. Hsp27 prevents the deleterious interaction of Cu(2+) with α-synuclein, the protein involved in Parkinson disease and synucleinopathies. Hsp27 attenuates Cu(2+)- or Cu(2+)-α-synuclein-mediated generation of reactive oxygen species and confers cytoprotection on IMR-32 cells as well as on mouse primary neural precursor cells. Hsp27 prevents Cu(2+)-ascorbate or Cu(2+)-α-synuclein-ascorbate treatment-induced increase in mitochondrial superoxide level and mitochondrial disorganization in IMR-32 cells. Hsp27 dislodges the α-synuclein-bound Cu(2+) and prevents the Cu(2+)-mediated amyloidogenesis of α-synuclein. Our findings that Hsp27 binds Cu(2+) with high affinity leading to beneficial effects and that Hsp27 can dislodge Cu(2+) from α-synuclein, preventing amyloid fibril formation, indicate potential therapeutic strategies for neurodegenerative diseases involving aberrant Cu(2+) homeostasis.
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500 007, India.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Asthana
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500 007, India.
authors.forename: Madhuri
authors.initials: M
authors.lastname: Bollapalli
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500 007, India.
authors.forename: Ramakrishna
authors.initials: R
authors.lastname: Tangirala
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500 007, India. Electronic address: raman@ccmb.res.in.
authors.forename: Raman
authors.initials: R
authors.lastname: Bakthisaran
authors.affiliation: CSIR-Centre for Cellular and Molecular Biology, Hyderabad 500 007, India. Electronic address: mohan@ccmb.res.in.
authors.forename: Ch
authors.initials: Ch
authors.lastname: Mohan Rao
mesh_terms: D016229:Amyloid beta-Peptides / Q000378:metabolism*; D015153:Blotting, Western; D002151:Calorimetry; D045744:Cell Line, Tumor; D003300:Copper / Q000378:metabolism*; D005434:Flow Cytometry; D055551:HSP27 Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D018613:Microscopy, Confocal; D009474:Neurons / Q000378:metabolism / Q000473:pathology*; D010084:Oxidation-Reduction; D018384:Oxidative Stress / Q000502:physiology; D014162:Transfection; D051844:alpha-Synuclein / Q000378:metabolism*
chemical_list: D016229:Amyloid beta-Peptides; D055551:HSP27 Heat-Shock Proteins; D051844:alpha-Synuclein; D003300:Copper
keywords: Amyloid fibril; Cu(2+) binding; Free radicals; Hsp27; Reactive oxygen species; α-Synuclein