Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive motor neuron death.More than 90 mutations in the copper-zinc superoxide dismutase (SOD1) gene cause a subset of familial ALS. Toxic properties have been proposed for the ALS-linked SOD1 mutants, but the nature of the toxicity has not been clearly specified. Cytoplasmic inclusion bodies containing mutant SOD1 and a number of other proteins are a pathological hallmark of mutant SOD1-mediated familial ALS, but whether such aggregates are toxic to motor neurons remains unclear. In this study, we identified a dynein subunit as a component of the mutant SOD1-containing high molecular weight complexes using proteomic techniques. We further demonstrated interaction and colocalization between dynein and mutant SOD1, but not normal SOD1, in cultured cells and also in G93A and G85R transgenic rodent tissues. Moreover, the interaction occurred early, prior to the onset of symptoms in the ALS animal models and increased over the disease progression. Motor neurons with long axons are particularly susceptible to defects in axonal transport. Our results demonstrate a direct "gain-of-interaction" between mutant SOD1 and dynein, which may provide insights into the mechanism by which mutant SOD1 could contribute to a defect in retrograde axonal transport or other dynein functions. The aberrant interaction is potentially critical to the formation of mutant SOD1 aggregates as well as the toxic cascades leading to motor neuron degeneration in ALS.

Mutations in copper-zinc superoxide dismutase (SOD1) have been linked to a subset of familial amytrophic lateral sclerosis (fALS), a fatal neurodegenerative disease characterized by progressive motor neuron death. An increasing amount of evidence supports that mitochondrial dysfunction and apoptosis activation play a critical role in the fALS etiology, but little is known about the mechanisms by which SOD1 mutants cause the mitochondrial dysfunction and apoptosis. In this study, we use proteomic approaches to identify the mitochondrial proteins that are altered in the presence of a fALS-causing mutant G93A-SOD1. A comprehensive characterization of mitochondrial proteins from NSC34 cells, a motor neuron-like cell line, was achieved by two independent proteomic approaches. Four hundred seventy unique proteins were identified in the mitochondrial fraction collectively, 75 of which are newly discovered proteins that previously had only been reported at the cDNA level. Two-dimensional gel electrophoresis was subsequently used to analyze the differences between the mitochondrial proteomes of NSC34 cells expressing wild-type and G93A-SOD1. Nine and 36 protein spots displayed elevated and suppressed abundance respectively in G93A-SOD1-expressing cells. The 45 spots were identified by MS, and they include proteins involved in mitochondrial membrane transport, apoptosis, the respiratory chain, and molecular chaperones. In particular, alterations in the post-translational modifications of voltage-dependent anion channel 2 (VDAC2) were found, and its relevance to regulating mitochondrial membrane permeability and activation of apoptotic pathways is discussed. The potential role of other proteins in the mutant SOD1-mediated fALS is also discussed. This study has produced a short list of mitochondrial proteins that may hold the key to the mechanisms by which SOD1 mutants cause mitochondrial dysfunction and neuronal death. Amyotrophic lateral sclerosis (ALS)1 is a fatal neurodegenerative disease characterized by progressive motor neuron death. Approximately 10% of ALS patients are familial cases (fALS), and mutations in the gene encoding copper-zinc superoxide dismutase (SOD1) were linked with a subset of fALS (1, 2). To date, more than 90 mutations in SOD1 are known to be responsible for ϳ25% of fALS (3), most of which are point mutations that are scattered throughout the primary sequence and structure of the protein. There has been intensive research focusing on the etiology of SOD1 mutant-mediated fALS (see reviews in . It has been demonstrated that SOD1-null mice did not develop the disease (9). In addition, transgenic mice expressing the ALS-associated mutants G93A-SOD1 (10, 11), G37R-SOD1 (12), and G85R-SOD1 (13, 14) as well as transgenic rats expressing G93A-SOD1 (15, 16) and H46R-SOD1 (16) developed progressive motor neuron disease despite normal or elevated SOD1 activity. Therefore, it is believed that the ALS-linked mutants of SOD1 have acquired unknown toxic properties that eventually lead to the disease. However, ...

A proteomic analysis was pursued to identify new signaling effectors of transforming growth factor B1 (TGF-B1) that serve as potential intracellular effectors of its apoptotic action in human prostate cancer cells. The androgen-sensitive and TGF-B-responsive human prostate cancer cells, LNCaP TBRII, were used as in vitro model. In response to TGF-B, significant posttranslational changes in two proteins temporally preceded apoptotic cell death. TGF-B mediated the nuclear export of prohibitin, a protein involved in androgen-regulated prostate growth, to the cytosol in the LNCaP TBRII cells. Cofilin, a protein involved in actin depolymerization, cell motility, and apoptosis, was found to undergo mitochondrial translocation in response to TGF-B before cytochrome c release. Loss-offunction approaches (small interfering RNA) to silence prohibitin expression revealed a modest decrease in the apoptotic response to TGF-B and a significant suppression in TGF-B-induced cell migration. Silencing Smad4 showed that the cellular localization changes associated with prohibitin and cofilin action in response to TGF-B are independent of

No abstract

Studies on the clinical course of familial ALS suggest that the duration of illness is relatively consistent for each mutation but variable among the different mutations. The authors analyzed the relative amount of mutant compared with normal SOD1 protein in the erythrocytes from 29 patients with ALS with 22 different mutations. Turnover of mutant SOD1 correlated with a shorter disease survival time.