title: S-Mercuration of ubiquitin carboxyl-terminal hydrolase L1 through Cys152 by methylmercury causes inhibition of its catalytic activity and reduction of monoubiquitin levels in SH-SY5Y cells.
abstract: Methylmercury (MeHg) is an environmental electrophile that covalently modifies cellular proteins. In this study, we identified proteins that undergo S-mercuration by MeHg. By combining two-dimensional SDS-PAGE, atomic absorption spectrometry and ultra performance liquid chromatography mass spectrometry (UPLC/MS/MS), we revealed that ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) is a target for S-mercuration in human neuroblastoma SH-SY5Y cells exposed to MeHg (1 µM, 9 hr). The modification site of UCH-L1 by MeHg was Cys152, as determined by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. MeHg was shown to inhibit the catalytic activity of recombinant human UCH-L1 in a concentration-dependent manner. Knockdown of UCH-L1 indicated that this enzyme plays a critical role in regulating mono-ubiquitin (monoUb) levels in SH-SY5Y cells and exposure of SH-SY5Y cells to MeHg caused a reduction in the level of monoUb in these cells. These observations suggest that UCH-L1 readily undergoes S-mercuration by MeHg through Cys152 and this covalent modification inhibits UCH-L1, leading to the potential disruption of the maintenance of cellular monoUb levels.
authors.affiliation: Faculty of Medicine, University of Tsukuba.
authors.forename: Takashi
authors.initials: T
authors.lastname: Toyama
authors.forename: Yumi
authors.initials: Y
authors.lastname: Abiko
authors.forename: Yuko
authors.initials: Y
authors.lastname: Katayama
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Kaji
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Kumagai
mesh_terms: D055162:Biocatalysis / Q000187:drug effects*; D003545:Cysteine; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008767:Methylmercury Compounds / Q000633:toxicity*; D009447:Neuroblastoma / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014407:Tumor Cells, Cultured; D025801:Ubiquitin / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase / Q000737:chemistry / Q000378:metabolism*
chemical_list: D008767:Methylmercury Compounds; C482860:UCHL1 protein, human; D025801:Ubiquitin; D043222:Ubiquitin Thiolesterase; D003545:Cysteine