Open AccessAmyotrophic lateral sclerosis: A proposed mechanism
Author(s) -
Ayako Okado-Matsumoto,
Irwin Fridovich
Publication year - 2002
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.132260399
Subject(s) - sod1 , amyotrophic lateral sclerosis , microbiology and biotechnology , mitochondrion , biology , mutant , heat shock protein , motor neuron , programmed cell death , chaperone (clinical) , neurodegeneration , superoxide dismutase , intermembrane space , hsp27 , cytoplasm , hsp70 , biochemistry , apoptosis , neuroscience , oxidative stress , medicine , gene , pathology , bacterial outer membrane , disease , spinal cord , escherichia coli
Missense mutations in Cu,Zn-superoxide dismutase (SOD1) account for approximately 20% of familial amyotrophic lateral sclerosis (FALS) through some, as yet undefined, toxic gain of function that leads to gradual death of motor neurons. Mitochondrial swelling and vacuolization are early signs of incipient motor neuron death in FALS. We previously reported that SOD1 exists in the intermembrane space of mitochondria. Herein, we demonstrate that the entry of SOD1 into mitochondria depends on demetallation and that heat shock proteins (Hsp70, Hsp27, or Hsp25) block the uptake of the FALS-associated mutant SOD1 (G37R, G41D, or G93A), while having no effect on wild-type SOD1. The binding of mutant SOD1 to Hsps in the extract of neuroblastoma cells leads to formation of sedimentable aggregates. Many antiapoptotic effects of Hsps have been reported. We now propose that this binding of Hsps to mutant forms of a protein abundant in motor neurons, such as SOD1, makes Hsps unavailable for their antiapoptotic functions and leads ultimately to motor neuron death. It also appears that the Hsp-SOD1 complex recruits other proteins present in the neuroblastoma cell and presumably in motor neurons to form sedimentable aggregates.