Alterations of structure and hydrolase activity of parkinsonism-associated human ubiquitin carboxyl-terminal hydrolase L1 variants |
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Authors: | Nishikawa Kaori Li Hang Kawamura Ryoichi Osaka Hitoshi Wang Yu-Lai Hara Yoko Hirokawa Takatsugu Manago Yoshimasa Amano Taiju Noda Mami Aoki Shunsuke Wada Keiji |
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Affiliation: | Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4-1-1 Ogawahigashi, Kodaira, 187-8502, Tokyo, Japan. |
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Abstract: | Ubiquitin carboxyl-terminal hydrolase L1 (UCH-L1) is a neuron-specific ubiquitin recycling enzyme. A mutation at residue 93 and polymorphism at residue 18 within human UCH-L1 are linked to familial Parkinson's disease and a decreased Parkinson's disease risk, respectively. Thus, we constructed recombinant human UCH-L1 variants and examined their structure (using circular dichroism) and hydrolase activities. We confirmed that an I93M substitution results in a decrease in kcat (45.6%) coincident with an alteration in alpha-helical content. These changes may contribute to the pathogenesis of Parkinson's disease. In contrast, an S18Y substitution results in an increase in kcat (112.6%) without altering the circular dichroistic spectrum. These data suggest that UCH-L1 hydrolase activity may be inversely correlated with Parkinson's disease risk and that the hydrolase activity is protective against the disease. Furthermore, we found that oxidation of UCH-L1 by 4-hydroxynonenal, a candidate for endogenous mediator of oxidative stress-induced neuronal cell death, results in a loss of hydrolase activity. Taken together, these results suggest that further studies of altered UCH-L1 hydrolase function may provide new insights into a possible common pathogenic mechanism between familial and sporadic Parkinson's disease. |
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Keywords: | Ubiquitin Proteasome UCH-L1 Parkinsonism Oxidative stress 4-Hydroxynonenal |
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