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Intermolecular transmission of superoxide dismutase 1 misfolding in living cells.

Authors :
Grad LI
Guest WC
Yanai A
Pokrishevsky E
O'Neill MA
Gibbs E
Semenchenko V
Yousefi M
Wishart DS
Plotkin SS
Cashman NR
Source :
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 2011 Sep 27; Vol. 108 (39), pp. 16398-403. Date of Electronic Publication: 2011 Sep 19.
Publication Year :
2011

Abstract

Human wild-type superoxide dismutase-1 (wtSOD1) is known to coaggregate with mutant SOD1 in familial amyotrophic lateral sclerosis (FALS), in double transgenic models of FALS, and in cell culture systems, but the structural determinants of this process are unclear. Here we molecularly dissect the effects of intracellular and cell-free obligately misfolded SOD1 mutant proteins on natively structured wild-type SOD1. Expression of the enzymatically inactive, natural familial ALS SOD1 mutations G127X and G85R in human mesenchymal and neural cell lines induces misfolding of wild-type natively structured SOD1, as indicated by: acquisition of immunoreactivity with SOD1 misfolding-specific monoclonal antibodies; markedly enhanced protease sensitivity suggestive of structural loosening; and nonnative disulfide-linked oligomer and multimer formation. Expression of G127X and G85R in mouse cell lines did not induce misfolding of murine wtSOD1, and a species restriction element for human wtSOD1 conversion was mapped to a region of sequence divergence in loop II and β-strand 3 of the SOD1 β-barrel (residues 24-36), then further refined surprisingly to a single tryptophan residue at codon 32 (W32) in human SOD1. Time course experiments enabled by W32 restriction revealed that G127X and misfolded wtSOD1 can induce misfolding of cell-endogenous wtSOD1. Finally, aggregated recombinant G127X is capable of inducing misfolding and protease sensitivity of recombinant human wtSOD1 in a cell-free system containing reducing and chelating agents; cell-free wtSOD1 conversion was also restricted by W32. These observations demonstrate that misfolded SOD1 can induce misfolding of natively structured wtSOD1 in a physiological intracellular milieu, consistent with a direct protein-protein interaction.

Details

Language :
English
ISSN :
1091-6490
Volume :
108
Issue :
39
Database :
MEDLINE
Journal :
Proceedings of the National Academy of Sciences of the United States of America
Publication Type :
Academic Journal
Accession number :
21930926
Full Text :
https://doi.org/10.1073/pnas.1102645108