Dataset Information

?-Synuclein fate is determined by USP9X-regulated monoubiquitination.

ABSTRACT: ?-Synuclein is central to the pathogenesis of Parkinson disease (PD). Mutations as well as accumulation of ?-synuclein promote the death of dopaminergic neurons and the formation of Lewy bodies. ?-Synuclein is monoubiquitinated by SIAH, but the regulation and roles of monoubiquitination in ?-synuclein biology are poorly understood. We now report that the deubiquitinase USP9X interacts in vivo with and deubiquitinates ?-synuclein. USP9X levels are significantly lower in cytosolic fractions of PD substantia nigra and Diffuse Lewy Body disease (DLBD) cortices compared to controls. This was associated to lower deubiquitinase activity toward monoubiquitinated ?-synuclein in DLBD cortical extracts. A fraction of USP9X seems to be aggregated in PD and DLBD, as USP9X immunoreactivity is detected in Lewy bodies. Knockdown of USP9X expression promotes accumulation of monoubiquitinated ?-synuclein species and enhances the formation of toxic ?-synuclein inclusions upon proteolytic inhibition. On the other hand, by manipulating USP9X expression levels in the absence of proteolytic impairment, we demonstrate that monoubiquitination controls the partition of ?-synuclein between different protein degradation systems. Deubiquitinated ?-synuclein is mostly degraded by autophagy, while monoubiquitinated ?-synuclein is preferentially degraded by the proteasome. Moreover, monoubiquitination promotes the degradation of ?-synuclein, whereas deubiquitination leads to its accumulation, suggesting that the degradation of deubiquitinated ?-synuclein by the autophagy pathway is less efficient than the proteasomal one. Lower levels of cytosolic USP9X and deubiquitinase activity in ?-synucleinopathies may contribute to the accumulation and aggregation of monoubiquitinated ?-synuclein in Lewy bodies. Our data indicate that monoubiquitination is a key determinant of ?-synuclein fate.

SUBMITTER: Rott R

PROVIDER: S-EPMC3219120 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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α-Synuclein fate is determined by USP9X-regulated monoubiquitination.

Rott Ruth R Szargel Raymonde R Haskin Joseph J Bandopadhyay Rina R Lees Andrew J AJ Shani Vered V Engelender Simone S

Proceedings of the National Academy of Sciences of the United States of America 20111107 46

α-Synuclein is central to the pathogenesis of Parkinson disease (PD). Mutations as well as accumulation of α-synuclein promote the death of dopaminergic neurons and the formation of Lewy bodies. α-Synuclein is monoubiquitinated by SIAH, but the regulation and roles of monoubiquitination in α-synuclein biology are poorly understood. We now report that the deubiquitinase USP9X interacts in vivo with and deubiquitinates α-synuclein. USP9X levels are significantly lower in cytosolic fractions of PD ...[more]

PMID: 22065755

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Project description:BackgroundRadioresistance is the major obstacle in radiation therapy (RT) for hepatocellular carcinoma (HCC). Dysregulation of DNA damage response (DDR), which includes DNA repair and cell cycle checkpoints activation, leads to radioresistance and limits radiotherapy efficacy in HCC patients. However, the underlying mechanism have not been clearly understood.MethodsWe obtained 7 pairs of HCC tissues and corresponding non-tumor tissues, and UBE2T was identified as one of the most upregulated genes. The radioresistant role of UBE2T was examined by colony formation assays in vitro and xenograft tumor models in vivo. Comet assay, cell cycle flow cytometry and γH2AX foci measurement were used to investigate the mechanism by which UBE2T mediating DDR. Chromatin fractionation and immunofluorescence staining were used to assess cell cycle checkpoint kinase 1(CHK1) activation. Finally, we analyzed clinical data from HCC patients to verify the function of UBE2T.ResultsHere, we found that ubiquitin-conjugating enzyme E2T (UBE2T) was upregulated in HCC tissues, and the HCC patients with higher UBE2T levels exhibited poorer outcomes. Functional studies indicated that UBE2T increased HCC radioresistance in vitro and in vivo. Mechanistically, UBE2T-RNF8, was identified as the E2-E3 pair, physically bonded with and monoubiquitinated histone variant H2AX/γH2AX upon radiation exposure. UBE2T-regulated H2AX/γH2AX monoubiquitination facilitated phosphorylation of CHK1 for activation and CHK1 release from the chromatin to cytosol for degradation. The interruption of UBE2T-mediated monoubiquitination on H2AX/γH2AX, including E2-enzyme-deficient mutation (C86A) of UBE2T and monoubiquitination-site-deficient mutation (K119/120R) of H2AX, cannot effectively activate CHK1. Moreover, genetical and pharmacological inhibition of CHK1 impaired the radioresistant role of UBE2T in HCC. Furthermore, clinical data suggested that the HCC patients with higher UBE2T levels exhibited worse response to radiotherapy.ConclusionOur results revealed a novel role of UBE2T-mediated H2AX/γH2AX monoubiquitination on facilitating cell cycle arrest activation to provide sufficient time for radiation-induced DNA repair, thus conferring HCC radioresistance. This study indicated that disrupting UBE2T-H2AX-CHK1 pathway maybe a promising potential strategy to overcome HCC radioresistance.

Dataset Information

?-Synuclein fate is determined by USP9X-regulated monoubiquitination.

Publications

α-Synuclein fate is determined by USP9X-regulated monoubiquitination.

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