Mutant Cu/Zn-superoxide dismutase proteins have altered solubility and interact with heat shock/stress proteins in models of amyotrophic lateral sclerosis
Ga. Shinder et al., Mutant Cu/Zn-superoxide dismutase proteins have altered solubility and interact with heat shock/stress proteins in models of amyotrophic lateral sclerosis, J BIOL CHEM, 276(16), 2001, pp. 12791-12796
Mutations in the Cu/Zn-superoxide dismutase (SOD-I) gene are responsible fo
r a familial form of amyotrophic lateral sclerosis, In humans and experimen
tal models, death of motor neurons is preceded by formation of cytoplasmic
aggregates containing mutant SOD-l protein. In our previous studies, heat s
hock protein 70 (HSP70) prolonged viability of cultured motor neurons expre
ssing mutant human SOD-l and reduced formation of aggregates. in this paper
, we report that mutant SOD-l proteins have altered solubility in cells rel
ative to wild-type SOD-l and can form a direct association with HSP70 and o
ther stress proteins. Whereas wild-type human and endogenous mouse SOD-1 we
re detergent-soluble, a portion of mutant SOD-l was detergent-insoluble in
protein extracts of NIH3T3 transfected with SOD-l gene constructs, spinal c
ord cultures established from G93A SOD-1 transgenic mouse embryos, and lumb
ar spinal cord from adult G93A transgenic mice. A direct association of HSP
70, HSP40, and alphaB-crystallin with mutant SOD-1 (G93A or G41S), but not
wild-type or endogenous mouse SOD-1, was demonstrated by coimmunoprecipitat
ion, Mutant SOD-1 HSP70 complexes were predominantly in the detergent-insol
uble fraction. However, only a small percentage of total cellular mutant SO
D-l was detergent-insoluble, suggesting that mutation-induced alteration of
protein conformation may not in itself be sufficient for direct interactio
n with heat shock proteins.