Activated p38MAPK Is a Novel Component of the Intracellular Inclusions Found in Human Amyotrophic Lateral Sclerosis and Mutant SOD1 Transgenic Mice

Bendotti, Caterina; Atzori, Cristiana; Piva, Roberto; Tortarolo, Massimo; Strong, Michael J.; Debiasi, S; Migheli, Antonio

doi:10.1093/jnen/63.2.113

Cited by 86 publications

(77 citation statements)

References 36 publications

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“…Taken together, these findings provide a molecular means for comparing the disease process in these mouse models of familial ALS with that in human patients with sporadic ALS unlinked to SOD1 mutations. Indeed, Bendotti et al (27) report that sporadic ALS cases show the same characteristic skein-like staining pattern for phospho-p38 as that observed in mutant SOD1 G93A mice.…”

Section: Discussionmentioning

confidence: 83%

Chronic activation in presymptomatic amyotrophic lateral sclerosis (ALS) mice of a feedback loop involving Fas, Daxx, and FasL

Raoul

Buhler

Sadeghi

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

100

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The reasons for the cellular specificity and slow progression of motoneuron diseases such as ALS are still poorly understood. We previously described a motoneuron-specific cell death pathway downstream of the Fas death receptor, in which synthesis of nitric oxide (NO) is an obligate step. Motoneurons from ALS model mice expressing mutant SOD1 showed increased susceptibility to exogenous NO as compared with controls. Here, we report a signaling mechanism whereby NO leads to death of mutant, but not control, motoneurons. Unexpectedly, exogenous NO triggers expression of Fas ligand (FasL) in cultured motoneurons. In mutant SOD1 G93A and SOD1 G85R , but not in control motoneurons, this up-regulation results in activation of Fas, leading through Daxx to phosphorylation of p38 and further NO synthesis. This Fas͞NO feedback amplification loop is required for motoneuron death in vitro. In vivo, mutant SOD1 G93A and SOD1 G85R mice show increased numbers of positive motoneurons and Daxx nuclear bodies weeks before disease onset. Moreover, FasL up-regulation is reduced in the presence of transgenic dominant-negative Daxx. We propose that chronic low-level activation of the Fas͞NO feedback loop may underlie the motoneuron loss that characterizes familial ALS and may help to explain its slowly progressive nature.cell death ͉ motoneuron disease ͉ NO ͉ p38 kinase ͉ neurodegeneration A myotrophic lateral sclerosis (ALS) is the most frequent adultonset motoneuron disease in humans. ALS is characterized by the selective degeneration of motoneurons in spinal cord, brainstem, and cerebral cortex leading to muscle atrophy and paralysis and ultimately to death. About 1 to 2% of all human ALS forms are caused by dominantly inherited mutations in the Cu͞Zn superoxide dismutase (SOD1) gene. Mice transgenic for the ALS-linked SOD1 mutations G37R (1), H46R͞H48Q (2), G85R (3), and G93A (4) develop an adult-onset motoneuron disorder that remarkably resembles human ALS.Despite much intensive study, many questions remain concerning the mechanism(s) by which mutant SOD1 triggers specific motoneuron death. One unresolved issue is the cellular site of action of the gain-of-function mutations. Clement et al. (5) generated chimeric mice carrying a mixture of WT and mutant SOD1-expressing cells in the spinal cord. In these mice, WT motoneurons eventually showed stigmata of degeneration, whereas some mutant SOD1 motoneurons were protected from degeneration when surrounded by WT nonneuronal cells. These results suggest that mutant SOD1 in both motoneurons and surrounding cells may play a role in the disease process.Our earlier studies using cultures of purified embryonic motoneurons reached similar conclusions. We found that motoneurons from SOD1 G93A , SOD1 G37R , and SOD1 G85R mice survived normally in the presence of optimal trophic support or when challenged by excitotoxic agonists. In marked contrast, compared with controls, they displayed a 10-to 100-fold increase in sensitivity to extracellular agonists of the Fas receptor or to exogenous nitr...

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Section: Discussionmentioning

confidence: 83%

Chronic activation in presymptomatic amyotrophic lateral sclerosis (ALS) mice of a feedback loop involving Fas, Daxx, and FasL

Raoul

Buhler

Sadeghi

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

100

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“…Thin sections of the ventral horn cut with an ultramicrotome were collected on Formvar-coated nickel grids and processed with a standard postembedding immunogold staining protocol (30). Briefly, the grids were incubated overnight at 4°C with either a monoclonal anti-human SOD1 antiserum (dilution 1:2000) (Medical & Biological Laboratories Co., Nagoya, Japan) or a polyclonal anti-ubiquitin antiserum (UG9510, Biomol; dilution 1:2000) for single labeling or with a mixture of both antisera for double labeling.…”

Section: Methodsmentioning

confidence: 99%

Insoluble Mutant SOD1 Is Partly Oligoubiquitinated in Amyotrophic Lateral Sclerosis Mice

Basso

Massignan

Giuseppina

et al. 2006

Journal of Biological Chemistry

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Mutations in the Cu,Zn-superoxide dismutase (SOD1) gene cause a familial form of amyotrophic lateral sclerosis (ALS) through an unknown gain-of-function mechanism. Mutant SOD1 aggregation may be the toxic property. In fact, proteinaceous inclusions rich in mutant SOD1 have been found in tissues from the familial form of ALS patients and in mutant SOD1 animals, before disease onset. However, very little is known of the constituents and mechanism of formation of aggregates in ALS. We and others have shown that there is a progressive accumulation of detergent-insoluble mutant SOD1 in the spinal cord of G93A SOD1 mice. To investigate the mechanism of SOD1 aggregation, we characterized by proteome technologies SOD1 isoforms in a Triton X-100-insoluble fraction of spinal cord from G93A SOD1 mice at different stages of the disease. This showed that at symptomatic stages of the disease, part of the insoluble SOD1 is unambiguously mono-and oligoubiquitinated, in spinal cord and not in hippocampus, and that ubiquitin branches at Lys 48 , the major signal for proteasome degradation. At presymptomatic stages of the disease, only insoluble unmodified SOD1 is recovered. Partial ubiquitination of SOD1-rich inclusions was also confirmed by immunohistochemical and electron microscopy analysis of lumbar spinal cord sections from symptomatic G93A SOD1 mice. On the basis of these results, we propose that ubiquitination occurs only after SOD1 aggregation and that oligoubiquitination may underline alternative mechanisms in disease pathogenesis.

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“…However, whatever the composition of these nitrated microaggregates, they do not seem to cause massive accumulation and aggregation of nitrated proteins in the motor neurons at a later phase of degeneration. In fact, although there is a steep rise in NT immunoreactivity in the spinal cord sections at the advanced stages of the disease, the signal appears homogeneously distributed in the reactive astrocytes and in shrunken motor neurons, except for some scattered, intensely labeled, round formations reminiscent of axonal spheroids (38). In addition, the pattern of distribution of NT-immunoreactivity is different from that of ubiquitinated protein aggregates, suggesting that nitrated proteins do not accumulate in those aggregates (30).…”

Section: Fig 3 Nt Immunoreactivity In Ventral Horn Of Transverse Sementioning

confidence: 97%

Protein Nitration in a Mouse Model of Familial Amyotrophic Lateral Sclerosis

Casoni

Basso

Massignan

et al. 2005

Journal of Biological Chemistry

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172

119

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Multiple mechanisms have been proposed to contribute to amyotrophic lateral sclerosis (ALS) pathogenesis, including oxidative stress. Early evidence of a role for oxidative damage was based on the finding, in patients and murine models, of high levels of markers, such as free nitrotyrosine (NT). However, no comprehensive study on the protein targets of nitration in ALS has been reported. We found an increased level of NT immunoreactivity in spinal cord protein extracts of a transgenic mouse model of familial ALS (FALS) at a presymptomatic stage of the disease compared with age-matched controls. NT immunoreactivity is increased in the soluble fraction of spinal cord homogenates and is found as a punctate staining in motor neuron perikarya of presymptomatic FALS mice. Using a proteome-based strategy, we identified proteins nitrated in vivo, under physiological or pathological conditions, and compared their level of specific nitration. ␣-and ␥-enolase, ATP synthase ␤ chain, and heat shock cognate 71-kDa protein and actin were overnitrated in presymptomatic FALS mice. We identified by matrix-assisted laser desorption/ionization mass spectrometry 16 sites of nitration in proteins oxidized in vivo. In particular, ␣-enolase nitration at Tyr 43 , target also of phosphorylation, brings additional evidence on the possible interference of nitration with phosphorylation. In conclusion, we propose that protein nitration may have a role in ALS pathogenesis, acting directly by inhibiting the function of specific proteins and indirectly interfering with protein degradation pathways and phosphorylation cascades.

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Activated p38MAPK Is a Novel Component of the Intracellular Inclusions Found in Human Amyotrophic Lateral Sclerosis and Mutant SOD1 Transgenic Mice

Cited by 86 publications

References 36 publications

Chronic activation in presymptomatic amyotrophic lateral sclerosis (ALS) mice of a feedback loop involving Fas, Daxx, and FasL

Chronic activation in presymptomatic amyotrophic lateral sclerosis (ALS) mice of a feedback loop involving Fas, Daxx, and FasL

Insoluble Mutant SOD1 Is Partly Oligoubiquitinated in Amyotrophic Lateral Sclerosis Mice

Protein Nitration in a Mouse Model of Familial Amyotrophic Lateral Sclerosis

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