Up-Regulation of Protein Chaperones Preserves Viability of Cells Expressing Toxic Cu/Zn-Superoxide Dismutase Mutants Associated with Amyotrophic Lateral Sclerosis

Authors

  • Wendy Bruening,

  • Josée Roy,

  • Benoit Giasson,

  • Denise A Figlewicz,

  • Walter E Mushynski,

  • Heather D Durham


  • The present address of Dr. W. Bruening is Fox Chase Cancer Center, Philadelphia, PA, U.S.A.

  • The present address of Dr. B. Giasson is Center for Neurodegenerative Research, Department of Pathology and Laboratory Medicine, Univcersity of Pennsylvania School of Medicine, Philadelphia, PA, U.S.A

  • Abbreviations used : FALS, familial amyotrophic lateral sclerosis ; FITC, flourescein isothiocyanate ; HSP, heat shock protein ; SOD-1, Cu/Zn-superoxide dismutase.

Address correspondence and reprint requests to Dr. H. D. Durham at Montreal Neurological Institute, Rm. 649, 3801 University St., Montreal, Quebec, Canada H3A 2B4..

Abstract

Abstract : Mutations in the Cu/Zn-superoxidedismutase (SOD-1) gene underlie some familial cases of amytotrophic lateral sclerosis, a neurodegenerative disorder charactreized by loss of cortical, brainstem, and spinal motor nrurons. We present evidence that SOD-1 mutants alter the activity of molecular chaperones that aid in proper protein folding and targeting of abnormal proteins for degradation. In a cultured cell line (NOH 3T3), resistance to mutant SOD-1 toxicity correlated with increased overall chaperoning activity (measured by the ability of cytosolic extracts to prevent heat denaturation of catalase) as well as with up-regulation of individual chaperones/stress proteins. In transgenic mice expressing human SOD-1 with the G93A mutation, chaperoning activity was decreased in lumbar spinal cord but increased or unchanged in clinically unaffected tissues. Increasing the level of the stress-inducible chaperone 70-kDa heat shock protein by gene transfer reduced formation of mutant SOD-containing proteinaceous aggregates in cultured primary motor neurons expressing G93A SOG-1 and prolonged their survival. We propose that insufficiency of molecular chaperones may be directly involved in loss of motor neurons in this disease.

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