Dorfin Ameliorates Phenotypes in a Transgenic Mouse Model of Amyotrophic Lateral Sclerosis Jun Sone, 1 Jun-ichi Niwa, 1,2 Kaori Kawai, 1 Shinsuke Ishigaki, 1 Shin-ichi Yamada, 1 Hiroaki Adachi, 1 Masahisa Katsuno, 1 Fumiaki Tanaka, 1 Manabu Doyu, 1,2 and Gen Sobue 1 * 1 Department of Neurology, Nagoya University Graduate School of Medicine, Nagoya, Japan 2 Department of Neurology and Stroke Center, Aichi Medical University, Aichi, Japan Amyotrophic lateral sclerosis (ALS) is a fatal neurode- generative disease that is characterized by progressive motor neuron degeneration and leads to death within a few years of diagnosis. One of the pathogenic mecha- nisms of ALS is proposed to be a dysfunction in the protein quality-control machinery. Dorfin has been iden- tified as a ubiquitin ligase (E3) that recognizes and ubiquitinates mutant SOD1 proteins, thereby accelerat- ing their degradation and reducing their cellular toxicity. We examined the effects of human Dorfin overexpres- sion in G93A mutant SOD1 transgenic mice, a mouse model of familial ALS. In addition to causing a decrease in the amount of mutant SOD1 protein in the spinal cord, Dorfin overexpression ameliorated neurological phenotypes and motor neuron degeneration. Our results indicate that Dorfin overexpression or the acti- vation or induction of E3 may be a therapeutic avenue for mutant SOD1-associated ALS. V V C 2009 Wiley-Liss, Inc. Key words: Dorfin; ALS; G93A mutant SOD1; ubiquitin ligase; neurodegeneration Amyotrophic lateral sclerosis (ALS) is a progressive and fatal neurodegenerative disease characterized by pro- gressive muscle atrophy, paralysis, and death within a few years of diagnosis (Rowland and Shneider, 2001). Several hypotheses for the pathogenesis of ALS have been proposed, including protein quality-control dys- function, mitochondrial damage, oxidative stress, gluta- mate receptor abnormality, inflammation, neurotrophic factor deficiency, and activation of apoptosis (Julien, 2001; Boillee et al., 2006; Kabashi and Durham, 2006; Cassina et al., 2008). However, the pathogenic mecha- nism has not been clarified, and no effective therapy has been developed. Approximately 90% of ALS cases are sporadic (nonhereditary; SALS) and 10% are familial ALS (hereditary; FALS). About 20% of cases of FALS are due to mutations in Cu/Zn superoxide dismutase 1 (SOD1; Rosen et al., 1993; Hirano, 1996; Martin et al., 2007). Mutant SOD1 protein is thought to induce motor neuron degeneration by a gain of toxic function rather than a loss of dismutase function (Bruijn et al., 1998; Boillee et al., 2006; Martin et al., 2007). Sporadic and familial ALS present inclusion bodies composed of aberrant protein aggregates in the cyto- plasm of residual motor neurons (Shibata et al., 1996; Ross and Poirier, 2004; Strong et al., 2005). Inclusions containing mutant SOD1 are found in the motor neu- rons of mutant SOD1-related FALS patients and mutant SOD1 transgenic (Tg) mice (Gurney et al., 1994; Shibata et al., 1996; Watanabe et al., 2001). Aberrant proteins such as mutant SOD1 are ubiquitinated (Alves-Rodrigues et al., 1998; Ardley and Robinson, 2004) and are thought to be degraded by the ubiquitin- proteasome system (Niwa et al., 2002; Urushitani et al., 2002; Goldberg, 2003; Kabuta et al., 2006; Cheroni et al., 2009). However, when the production of aberrant proteins exceeds the cellular degradation capacity, these proteins often form aggregates before they are degraded (Sherman and Goldberg, 2001; Goldberg, 2003). The ubiquitin-proteasome system mediates post- translational modification and degradation of proteins and is essential for many fundamental cellular functions, including cell cycling, DNA repair, cell signaling, gene transcription, and apoptosis (Ardley and Robinson, 2004; Kabashi and Durham, 2006). Protein ubiquitination is an ATP-dependent process during which ubiquitin is sequentially activated by ubiquitin-activating enzymes (E1), transferred to ubiquitin-conjugating enzymes (E2), Contract grant sponsor: 21st Century Center of Excellence (COE) grant and global COE grant from the Ministry of Education, Culture, Sports, Science and Technology of Japan; Contract grant sponsor: Ministry of Health, Welfare and Labor of Japan; Contract grant sponsor: Core Research for Evolutional Science and Technology. *Correspondence to: Gen Sobue, MD, Department of Neurology, Nagoya University Graduate School of Medicine, Nagoya 466-8550, Japan. E-mail: sobueg@med.nagoya-u.ac.jp Received 22 January 2009; Revised 20 May 2009; Accepted 24 May 2009 Published online 16 July 2009 in Wiley InterScience (www. interscience.wiley.com). DOI: 10.1002/jnr.22175 Journal of Neuroscience Research 88:123–135 (2010) ' 2009 Wiley-Liss, Inc.