title: Inorganic stressors of ubiquitin.
abstract: Many neurodegenerative proteinopathies are characterized by ubiquitin (Ub)-containing intraneuronal inclusion bodies. Recent reports have shown that Ub is able to bind Cu(II) and Zn(II), the dyshomeostasis of which is a hallmark of neurodegeneration. Here we use complementary techniques like potentiometry, circular dichroism-visible, and electron spin resonance to unveil the Ub/metal species that form, at neutral pH, their binding constants and structural features. Next, we show that both Zn(II) and Cu(II) ions hinder the interactions between Ub and Ub-conjugating E2 enzymes and inhibit significantly both Lys48 and Lys63 self-polyubiquitination reactions in a cell-free medium. The effects of Zn(II) and Cu(II) on Lys63 and Lys48 polyUb chain synthesis are compatible with the hypothesis that metal binding to His68 modifies the Ile44 hydrophobic patch of Ub and makes the protein less available for polyUb. These findings contribute to further arguments for a close relationship between metal dyshomeostasis and abnormal protein degradative pathways in the upstream events, triggering neurodegeneration.
authors.affiliation: Dipartimento di Scienze Chimiche, Università degli Studi di Catania, Viale Andrea Doria 6, 95125 Catania, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Arena
authors.forename: Francesco
authors.initials: F
authors.lastname: Bellia
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Frasca
authors.forename: Giulia
authors.initials: G
authors.lastname: Grasso
authors.forename: Valeria
authors.initials: V
authors.lastname: Lanza
authors.forename: Enrico
authors.initials: E
authors.lastname: Rizzarelli
authors.forename: Giovanni
authors.initials: G
authors.lastname: Tabbì
authors.forename: Valeria
authors.initials: V
authors.lastname: Zito
authors.forename: Danilo
authors.initials: D
authors.lastname: Milardi
mesh_terms: D003300:Copper / Q000737:chemistry / Q000494:pharmacology*; D006706:Homeostasis / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D008239:Lysine / Q000378:metabolism; D008958:Models, Molecular; D019636:Neurodegenerative Diseases / Q000139:chemically induced; D025801:Ubiquitin / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000037:antagonists & inhibitors / Q000378:metabolism; D054875:Ubiquitination / Q000187:drug effects; D015032:Zinc / Q000737:chemistry / Q000494:pharmacology*
chemical_list: D025801:Ubiquitin; D003300:Copper; D044763:Ubiquitin-Conjugating Enzymes; D015032:Zinc; D008239:Lysine