Progressive aggregation despite chaperone associations of a mutant SOD1-YFP in transgenic mice that develop ALS

Jiou Wang, George W. Farr, Caroline J. Zeiss, Diego J. Rodriguez-Gil, Jean H. Wilson, Krystyna Furtak, D. Thomas Rutkowski, Randal J. Kaufman, Cristian I. Ruse, John R. Yates, Steve Perrin, Mel B. Feany, Arthur L. Horwich

Research output: Contribution to journalArticlepeer-review

Abstract

Recent studies suggest that superoxide dismutase 1 (SOD1)-linked amyotrophic lateral sclerosis results from destabilization and mis-folding of mutant forms of this abundant cytosolic enzyme. Here, we have tracked the expression and fate of a misfolding-prone human SOD1, G85R, fused to YFP, in a line of transgenic G85R SOD1-YFP mice. These mice, but not wild-type human SOD1-YFP transgenics, developed lethal paralyzing motor symptoms at 9 months. In situ RNA hybridization of spinal cords revealed predominant expression in motor neurons in spinal cord gray matter in all transgenic animals. Concordantly, G85R SOD-YFP was diffusely fluorescent in motor neurons of animals at 1 and 6 months of age, but at the time of symptoms, punctate aggregates were observed in cell bodies and processes. Biochemical analyses of spinal cord soluble extracts indicated that G85R SOD-YFP behaved as a misfolded monomer at all ages. It became progressively insoluble at 6 and 9 months of age, associated with presence of soluble oligomers observable by gel filtration. Immunoaffinity capture and mass spectrometry revealed association of G85R SOD- YFP, but not WT SOD-YFP, with the cytosolic chaperone Hsc70 at all ages. In addition, 3 Hsp110's, nucleotide exchange factors for Hsp70s, were captured at 6 and 9 months. Despite such chaperone interactions, G85R SOD-YFP formed insoluble inclusions at late times, containing predominantly intermediate filament proteins. We conclude that motor neurons, initially ''compensated'' to maintain the misfolded protein in a soluble state, become progressively unable to do so.

Original languageEnglish (US)
Pages (from-to)1392-1397
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume106
Issue number5
DOIs
StatePublished - Feb 3 2009
Externally publishedYes

Keywords

  • Hsc70
  • Hsp110
  • Motor neuron
  • Neurodegeneration
  • Proteomic

ASJC Scopus subject areas

  • General

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