Octapeptide repeat region and N-terminal half of hydrophobic region of prion protein (PrP) mediate PrP-dependent activation of superoxide dismutase Akikazu Sakudo a,b , Deug-chan Lee a , Takuya Nishimura a , Shuming Li b , Shoutaro Tsuji b , Toyoo Nakamura c , Yoshitsugu Matsumoto a , Keiichi Saeki a , Shigeyoshi Itohara d , Kazuyoshi Ikuta b , Takashi Onodera a, * a Department of Molecular Immunology, School of Agricultural and Life Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-8657, Japan b Department of Virology, Research Institute for Microbial Diseases, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan c Itoham Central Research Institute, Moriya, Kitasoma, Ibaraki 302-01, Japan d Laboratory for Behavioral Genetics, Brain Science Institute, RIKEN, Wako, Saitama 351-0198, Japan Received 9 November 2004 Available online 7 December 2004 Abstract Cellular prion protein PrP C contains two evolutionarily conserved domains among mammals; viz., the octapeptide repeat region (OR; amino acid residue 51–90) and the hydrophobic region (HR; amino acid residue 112–145). Accumulating evidence indicates that PrP C acts as an inhibitor of apoptosis and regulator of superoxide dismutase (SOD) activity. To further understand how PrP C activates SOD and prevents apoptosis, we provide evidence here that OR and N-terminal half of HR mediate PrP C -dependent SOD activation and anti-apoptotic function. Removal of the OR (amino acid residue 53–94) enhances apoptosis and decreases SOD activity. Deletion of the N-terminal half of HR (amino acids residue 95–132) abolishes its ability to activate SOD and to prevent apoptosis, whereas that of the C-terminal half of HR (amino acids residue 124–146) has little if any effect on the anti-apoptotic activ- ity and SOD activation. These data are consistent with a model in which the anti-apoptotic and anti-oxidative function of PrP C is regulated by not only OR but also the N-terminal half of HR. Ó 2004 Elsevier Inc. All rights reserved. Keywords: Prion disease; Prion protein; Apoptosis; PrP-deficient cell line The spongiform encephalopathies (prion diseases) such as Creutzfeldt–Jakob disease and Gerstmann– Stra ¨ussler Scheinker syndrome in humans, scrapie in sheep and goats, and bovine spongiform encephalopa- thy in cattle are fatal neurodegenerative disorders with pathologies including neuronal cell loss, vacuolation, astrocytosis, and amyloid plaques [1]. The expression of a glycosylphosphatidylinositol (GPI)-anchored plas- ma membrane cellular prion protein PrP C is required for the propagation of the prion [2]. Prion infection is attributed to entry of a proteinaceous particle into nor- mal brain, leading to accumulation of an abnormally folded form of the prion protein (PrP Sc ) as a conse- quence of conformational conversion from the endoge- nous PrP C [1]. Although several different theories have been pro- posed, the exact physiological functions of PrP C remain unclear. Aberrant circadian rhythms [3], electrophysio- logical abnormalities [4], and high susceptibility to sei- zure [5] in prion protein (PrP) gene (Prnp)-knockout mice have been reported. Furthermore, although several PrP C binding molecules such as laminin [6], 37-kDa/67- kDa laminin receptor [7], 37-kDa laminin receptor 0006-291X/$ - see front matter Ó 2004 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2004.11.092 * Corresponding author. Fax: +81 3 5841 8020. E-mail address: aonoder@mail.ecc.u-tokyo.ac.jp (T. Onodera). www.elsevier.com/locate/ybbrc Biochemical and Biophysical Research Communications 326 (2005) 600–606 BBRC