Selective Death Of Motor Neurons Research Articles

Increased levels of phosphoinositides cause neurodegeneration in a Drosophila model of amyotrophic lateral sclerosis

The Vesicle-associated membrane protein (VAMP)-Associated Protein B (VAPB) is the causative gene of amyotrophic lateral sclerosis 8 (ALS8) in humans. Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by selective death of motor neurons leading to spasticity, muscle atrophy and paralysis. VAP proteins have been implicated in various cellular processes, including intercellular signalling, synaptic remodelling, lipid transport and membrane trafficking and yet, the molecular mechanisms underlying ALS8 pathogenesis remain poorly understood. We identified the conserved phosphoinositide phosphatase Sac1 as a Drosophila VAP (DVAP)-binding partner and showed that DVAP is required to maintain normal levels of phosphoinositides. Downregulating either Sac1 or DVAP disrupts axonal transport, synaptic growth, synaptic microtubule integrity and the localization of several postsynaptic components. Expression of the disease-causing allele (DVAP-P58S) in a fly model for ALS8 induces neurodegeneration, elicits synaptic defects similar to those of DVAP or Sac1 downregulation and increases phosphoinositide levels. Consistent with a role for Sac1-mediated increase of phosphoinositide levels in ALS8 pathogenesis, we found that Sac1 downregulation induces neurodegeneration in a dosage-dependent manner. In addition, we report that Sac1 is sequestered into the DVAP-P58S-induced aggregates and that reducing phosphoinositide levels rescues the neurodegeneration and suppresses the synaptic phenotypes associated with DVAP-P58S transgenic expression. These data underscore the importance of DVAP–Sac1 interaction in controlling phosphoinositide metabolism and provide mechanistic evidence for a crucial role of phosphoinositide levels in VAP-induced ALS.

158 A molecular dynamics simulation-based prediction of deleterious angiogenin mutations causing amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder characterized by the selective death of motor neurons leading to paralysis and death between 3–5 years of diagnosis. Through whole genome association studies, several single nucleotide polymorphisms (SNPs) encoding missense mutations in angiogenin (ANG) protein have been identified as one of the primary factors causing ALS. Structural studies of ANG show that catalytic triad comprising His13, Lys40, and His114 residues imparts ribonucleolytic activity while nuclear localization signal residues 31RRR33 are responsible for nuclear translocation activity. Loss of either ribonucleolytic activity or nuclear translocation activity or both of these functions due to mutations cause ALS. However, the mechanisms of loss-of-functions of ANG mutants are not completely understood. Here, we present a cohesive and comprehensive picture of functional loss mechanisms of all known ALS-associated ANG mutants by extensive molecular dynamics (MD) simulations (Padhi, Kumar, Vasaikar, Jayaram, & Gomes, 2012; AK, 2013). Our studies show that conformational switching of catalytic residue His114 is responsible for the loss of ribonucleolytic activity while reduction in solvent-accessible surface area (SASA) of 31RRR33 as a result of local folding is responsible for the loss of nuclear translocation activity (Padhi et al., 2012; AK, 2013). Our prediction of loss-of-functions of 17 ANG mutants correlated positively with the reported experimental results. We have subsequently developed a fast molecular dynamics method based on certain global attributes / dynamic markers that can be used to determine whether a mutation is deleterious or benign. To make our method accessible to researchers and clinicians, we created a web server-based tool, ANGDelMut, freely available at http://bioschool.iitd.ernet.in/research.htm, where a user can submit new mutations to ascertain whether they cause ALS. We hope that our method will benefit the community at large and will pave the way for the development of a successful therapy for patients suffering from ALS.

Stem Cell Transplantation in Amyotrophic Lateral Sclerosis Patients: Methodological Approach, Safety, and Feasibility

Amyotrophic lateral sclerosis is characterized by the selective death of motor neurons. Stem cells have been proposed as a potential therapeutic strategy. The safety of stem cell transplantation into the frontal motor cortex to improve upper motor neuron function is described. Sixty-seven patients with definite amyotrophic lateral sclerosis were included. After giving their informed consent, the patients underwent magnetic resonance imaging, functional rating, pulmonary function test, and laboratory tests. Their bone marrow was stimulated with daily filgrastim (300 µg) given subcutaneously for 3 days. Peripheral blood mononuclear cells were obtained by leukapheresis. Isolated CD133(+) stem cells were suspended in 300 µl of the patient's cerebrospinal fluid and implanted into the motor cortex. Adverse events were recorded at each step of the procedure and were classified according to the Common Terminology Criteria for Adverse Events v3.0. The survival at 1 year was 90% after transplantation. with a mean long-term survival rate of 40.17 months from diagnosis. The most common adverse events were in grades I-II and involved transient skin pain (19.5% of patients) attributed to the insertion of the Mahurkar catheter into the subclavian vein, minor scalp pain (15.9%), and headache (12.2%) from the surgical procedure. Several patients (1.5 - 4.5%) reported diverse grade I adverse events. There were two deaths, one considered to be associated with the procedure (1.5%) and the other associated with the disease. Autologous stem cell transplantation into the frontal motor cortex is safe and tolerated well by patients. Further controlled studies are required to define the efficacy of this procedure.

Dantrolene is neuroprotective in vitro, but does not affect survival in SOD1G93A mice

Amyotrophic Lateral Sclerosis (ALS) is a devastating progressive neurodegenerative disease. One of the proposed disease mechanisms is excitotoxicity, in which excessive cytosolic calcium causes neuronal death. Although most calcium may originate from the extracellular space through activation of calcium-permeable AMPA receptors, we investigated in this study the contribution of endoplasmic reticulum calcium release by blocking the ryanodine receptor (RyR) using dantrolene. In vitro, dantrolene provides a significant protection to motor neurons exposed to a brief excitotoxic insult. However, daily administration of dantrolene to mice overexpressing superoxide dismutase 1 glycine to alanine at position 93 (SOD1G93A) does affect neither survival nor the number of motor neurons and ubiquitin aggregates indicating that calcium release through RyRs does not contribute to the selective motor neuron death in this animal model for ALS.

Novel deletion mutations of OPTN in amyotrophic lateral sclerosis in Japanese

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by selective motor neuron death in the brain and spinal cord. Many disease genes for ALS have been identified; however, each disease gene is responsible for very small fractions of ALS. Recently, mutations of the gene encoding optineurin (OPTN) are reported in familial and sporadic ALS. OPTN is also responsible for a small number of ALS, 3.8% of familial and 0.29% of sporadic ALS in Japanese. The low prevalence may be an underestimation due to incomplete screening of the mutation. To examine OPTN mutations more extensively, we screened the OPTN deletions using a quantitative PCR system. We examined 710 Japanese ALS subjects who had previously been found to have no OPTN mutations by a screening using a PCR-direct sequence strategy. We identified 3 kinds of deletions in 5 patients; one was homozygous, and the remaining were heterozygous. All deletions occurred due to the Alu-mediated recombination and are expected to result in null alleles. Our results suggest that the OPTN deletion mutation in ALS is not infrequent and the prevalence of the OPTN mutation in Japanese sporadic ALS is considerably high.

Commentary ( Two Hits with One Shot – A Possibility of Simultaneous Targeting Motor Neuron Loss and Depression in ALS by Upregulating ADAR2 )

Commentary ( Two Hits with One Shot – A Possibility of Simultaneous Targeting Motor Neuron Loss and Depression in ALS by Upregulating ADAR2 ) pp.863-863 (1) Author: Laszlo Siklos Abstract: A leading hypothesis for the selective death of motor neurons in sporadic amyotrophic lateral sclerosis (ALS) is excitotoxicity mediated by Ca2+-permeable α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors. The AMPA receptors are assembled from 4 subunits and their permeability for Ca2+ is determined by the absence of the glutamate receptor subunit type 2 (GluR2), associated with an increased portion of unedited GluR2 mRNA at the glutamine/arginine (Q/R) site. RNA editing at this location is predominantly catalyzed by adenosine deaminase acting on RNA 2 (ADAR2). Thus, the observation that a substantial portion of Q/R site unedited GluR2 mRNA is present in postmortem spinal cord tissue of sporadic ALS patients suggests inefficiency of ADAR2 to be a disease-specific molecular dysfunction in ALS. To decide whether this malfunction could be a cause of motor neuron death in vivo, Hideyama and colleagues developed a conditional ADAR2 knock-out mouse line (designated as AR2), which carries gene-targeted floxed ADAR2 alleles that become functionally ablated by Cre recombinase expressed from a transgene (VAChT-Cre.Fast) in approximately 50% of motor neurons. They demonstrated that only the ADAR2-lacking spinal motor neurons degenerated in these animals, and this could be prevented by generating Q/R site edited GluR2 in the absence of ADAR2 by a point mutation in the endogenous GluR2 alleles. These results convincingly demonstrate that the inefficient GluR2 Q/R site editing found in the spinal cords of patients with sporadic ALS proposes the decreased level of ADAR2 mRNA to be a direct cause of death of motor neurons in mice, which accentuates the detrimental role of elevated Ca2+ influx in motor neurons as a consequence of increased Ca2+-permeability of AMPA receptors. From therapeutic point of view, an interesting aspect of the Ca2+-mediated cell death in ALS is connected with certain emotional reactions of the patients such as depression and anxiety, which has received particular attention in ALS. Although many researchers with experience with ALS challenge the lay opinion of an increased risk of developing major depressive disorder in ALS, studies using standardized methodology assessing nonphysical symptoms reported an occurrence exceeding the prevalence of that in the general population. There is growing evidence that besides the monoaminergic system the glutamatergic system, particularly N-methyl-D-aspartate receptor mediated Ca2+-entry plays an important role in the pathobiology of major depressive disorder. It is thus intriguing that conventional tricyclic antidepressants, specific serotonin reuptake inhibitors and serotonin/norepinephrine reuptake inhibitors not only down-regulate N-methyl-D-aspartate receptors but – at least in an in vitro model system – have the potency to enhance GluR2 Q/R site-editing either by up-regulating ADAR2 mRNA expression level, or through other unidentified mechanisms. It will now be important to determine whether these drugs exert a similar protective effect on motor neurons in in vivo models of ALS, and thus constitute a new therapeutic approach for this disease.

Early and progressive impairment of spinal blood flow-glucose metabolism coupling in motor neuron degeneration of ALS model mice.

The exact mechanism of selective motor neuron death in amyotrophic lateral sclerosis (ALS) remains still unclear. In the present study, we performed in vivo capillary imaging, directly measured spinal blood flow (SBF) and glucose metabolism, and analyzed whether if a possible flow-metabolism coupling is disturbed in motor neuron degeneration of ALS model mice. In vivo capillary imaging showed progressive decrease of capillary diameter, capillary density, and red blood cell speed during the disease course. Spinal blood flow was progressively decreased in the anterior gray matter (GM) from presymptomatic stage to 0.80-fold of wild-type (WT) mice, 0.61 at early-symptomatic, and 0.49 at end stage of the disease. Local spinal glucose utilization (LSGU) was transiently increased to 1.19-fold in anterior GM at presymptomatic stage, which in turn progressively decreased to 0.84 and 0.60 at early-symptomatic and end stage of the disease. The LSGU/SBF ratio representing flow-metabolism uncoupling (FMU) preceded the sequential pathological changes in the spinal cord of ALS mice and was preferentially found in the affected region of ALS. The present study suggests that this early and progressive FMU could profoundly involve in the whole disease process as a vascular factor of ALS pathology, and could also be a potential target for therapeutic intervention of ALS.

P4.55 Developing AMPA receptor aptamers as new drug candidates for ALS

Developing aptamer drugs for a new therapy for amyotrophic lateral sclerosis (ALS) is our ultimate goal. The aptamers are nanomolar affinity, water-soluble RNA inhibitors of the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptors, a subtype of glutamate ion channel receptors. Excessive activation of AMPA receptors induces calcium-mediated excitotoxicity, one of the leading causes underlying the selective death of motor neurons in ALS. To date, we have successfully identified aptamers that inhibit every AMPA receptor subunit – these are competitive and noncompetitive type.

Abnormal Changes in NKT Cells, the IGF-1 Axis, and Liver Pathology in an Animal Model of ALS

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing fatal neurodegenerative disorder characterized by the selective death of motor neurons (MN) in the spinal cord, and is associated with local neuroinflammation. Circulating CD4+ T cells are required for controlling the local detrimental inflammation in neurodegenerative diseases, and for supporting neuronal survival, including that of MN. T-cell deficiency increases neuronal loss, while boosting T cell levels reduces it. Here, we show that in the mutant superoxide dismutase 1 G93A (mSOD1) mouse model of ALS, the levels of natural killer T (NKT) cells increased dramatically, and T-cell distribution was altered both in lymphoid organs and in the spinal cord relative to wild-type mice. The most significant elevation of NKT cells was observed in the liver, concomitant with organ atrophy. Hepatic expression levels of insulin-like growth factor (IGF)-1 decreased, while the expression of IGF binding protein (IGFBP)-1 was augmented by more than 20-fold in mSOD1 mice relative to wild-type animals. Moreover, hepatic lymphocytes of pre-symptomatic mSOD1 mice were found to secrete significantly higher levels of cytokines when stimulated with an NKT ligand, ex-vivo. Immunomodulation of NKT cells using an analogue of α-galactosyl ceramide (α-GalCer), in a specific regimen, diminished the number of these cells in the periphery, and induced recruitment of T cells into the affected spinal cord, leading to a modest but significant prolongation of life span of mSOD1 mice. These results identify NKT cells as potential players in ALS, and the liver as an additional site of major pathology in this disease, thereby emphasizing that ALS is not only a non-cell autonomous, but a non-tissue autonomous disease, as well. Moreover, the results suggest potential new therapeutic targets such as the liver for immunomodulatory intervention for modifying the disease, in addition to MN-based neuroprotection and systemic treatments aimed at reducing oxidative stress.

Substance P receptor activation induces downregulation of the AMPA receptor functionality in cortical neurons from a genetic model of Amyotrophic Lateral Sclerosis

Substance P (SP), a neuropeptide member of the tachykinin (TK) family, has a functional role both in physiological and pathological conditions, including Amyotrophic Lateral Sclerosis disease. One hypothesis of the selective motor neuron death in ALS involves the excitatory neurotransmitter glutamate, because these neurons are extremely susceptible to excessive stimulation of AMPA receptors. It has been reported that SP exerts its action against a variety of insults including excitotoxicity, and that altered levels of SP have been observed in the cerebrospinal fluid (CSF) of patients with ALS. Here we have analyzed the interaction between SP and AMPA receptor functionality, both in Control cortical neurons in culture and in those obtained from a genetic mouse model of ALS (G93A). Our studies demonstrate that SP reduces the kainate-activated currents in Control and G93A neurons and that this reduction is significantly higher in the mutated neurons. SP effect is mediated by its receptor NK1 because GR 82334 (5 μM), a NK1 competitive antagonist, is able to suppress the current reduction. Analysis of miniature excitatory postsynaptic currents (mEPSCs) in Control and G93A neurons indicates that SP (200 nM) is able to significantly decrease the mEPSC amplitudes in G93A neurons, whereas it is ineffective on Control mEPSCs. Western blotting experiments in cultures and cortical tissues show a higher NK1 expression level in G93A mice compared to that of Control. This is also confirmed by immunocytochemistry experiments in cultured neurons. In addition, the amount of GluR1 subunit AMPA receptors is not modified following SP exposure, indicating a non internalization of the AMPA receptors. Finally, toxicity experiments have revealed that SP is able to rescue G93A cortical cells whereas it is ineffective on those of Control. These findings provide the first evidence of SP having a physiological and protective role in the G93A mouse model of ALS, and may suggest the possible use of SP as a clinical therapeutic treatment.

Vascular Endothelial Growth Factor Attenuates Neurodegenerative Changes in the NSC-34 Motor Neuron Cell Line Induced by Cerebrospinal Fluid of Sporadic Amyotrophic Lateral Sclerosis Patients

Background: Motor neuron disease or amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the selective death of motor neurons in the spinal cord as well as motor cortex. Recently, vascular endothelial growth factor (VEGF) has been identified as a neurotrophic factor in animal models of familial ALS and other neurological diseases. Objective: The present study was designed to investigate the neuroprotective role of VEGF in the more prevalent sporadic form of ALS. Methods: We studied the effect of VEGF on the NSC-34 cell line exposed to cerebrospinal fluid (CSF) from sporadic ALS patients (ALS-CSF) in terms of lactate dehydrogenase (LDH) assay as well as choline acetyltransferase (ChAT) and phosphorylated neurofilament expression by immunocytochemistry and confocal microscopy. NSC-34 cells were exposed to CSF from patients with definite ALS and compared to controls. LDH activity was assessed in the growth media, prior to and 24 h after the addition of VEGF to the cells. At similar time points, the cells were fixed and processed for immunocytochemistry to evaluate ChAT and phosphorylated neurofilament expression. Results: Exposure to ALS-CSF caused morphological changes of NSC-34 cells like reduced differentiation and aggregation of phosphorylated neurofilaments. Enhanced LDH activity and reduced ChAT immunoreactivity were also observed. Addition of VEGF to NSC-34 cells exposed to ALS-CSF was protective in terms of reduced LDH activity and restoration of ChAT expression. Conclusion: The present study confirms that VEGF exerts a neuroprotective effect on the NSC-34 cell line by attenuating the degenerative changes induced by ALS-CSF. It thus has therapeutic potential in sporadic ALS.

Proteomic assessment of a cell model of spinal muscular atrophy

BackgroundDeletion or mutation(s) of the survival motor neuron 1 (SMN1) gene causes spinal muscular atrophy (SMA), a neuromuscular disease characterized by spinal motor neuron death and muscle paralysis. Complete loss of the SMN protein is embryonically lethal, yet reduced levels of this protein result in selective death of motor neurons. Why motor neurons are specifically targeted by SMN deficiency remains to be determined. In this study, embryonic stem (ES) cells derived from a severe SMA mouse model were differentiated into motor neurons in vitro by addition of retinoic acid and sonic hedgehog agonist. Proteomic and western blot analyses were used to probe protein expression alterations in this cell-culture model of SMA that could be relevant to the disease.ResultsWhen ES cells were primed with Noggin/fibroblast growth factors (bFGF and FGF-8) in a more robust neural differentiation medium for 2 days before differentiation induction, the efficiency of in vitro motor neuron differentiation was improved from ~25% to ~50%. The differentiated ES cells expressed a pan-neuronal marker (neurofilament) and motor neuron markers (Hb9, Islet-1, and ChAT). Even though SMN-deficient ES cells had marked reduced levels of SMN (~20% of that in control ES cells), the morphology and differentiation efficiency for these cells are comparable to those for control samples. However, proteomics in conjunction with western blot analyses revealed 6 down-regulated and 14 up-regulated proteins with most of them involved in energy metabolism, cell stress-response, protein degradation, and cytoskeleton stability. Some of these activated cellular pathways showed specificity for either undifferentiated or differentiated cells. Increased p21 protein expression indicated that SMA ES cells were responding to cellular stress. Up-regulation of p21 was confirmed in spinal cord tissues from the same SMA mouse model from which the ES cells were derived.ConclusionSMN-deficient ES cells provide a cell-culture model for SMA. SMN deficiency activates cellular stress pathways, causing a dysregulation of energy metabolism, protein degradation, and cytoskeleton stability.

G37R SOD1 mutant alters mitochondrial complex I activity, Ca2+ uptake and ATP production

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by selective death of motor neurons. Mutations in Cu/Zn superoxide dismutase-1 (SOD1) cause familial ALS but the molecular mechanisms whereby these mutations induce motor neuron death remain controversial. Here, we show that stable overexpression of mutant human SOD1 (G37R) – but not wild-type SOD1 (wt-SOD1) – in mouse neuroblastoma cells (N2a) results in morphological abnormalities of mitochondria accompanied by several dysfunctions. Activity of the oxidative phosphorylation complex I was significantly reduced in G37R cells and correlated with lower mitochondrial membrane potential and reduced levels of cytosolic ATP. Using targeted chimeric aequorin we further analyzed the consequences of mitochondrial dysfunction on cellular Ca2+ handling. Mitochondrial Ca2+ uptake, elicited by IP3-induced Ca2+ release from endoplasmic reticulum (ER) was significantly reduced in G37R cells, while uptake induced by a brief Ca2+ pulse was not affected in permeabilized cells. The decreased mitochondrial Ca2+ uptake resulted in increased cytosolic Ca2+ transients, whereas ER Ca2+ load and resting cytosolic Ca2+ levels were not affected. Together, these findings suggest that the mechanism linking mutant G37R SOD1 and ALS involves mitochondrial respiratory chain deficiency resulting in ATP loss and impairment of mitochondrial and cytosolic Ca2+ homeostasis.

Genetic Rodent Models of Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by the selective death of motor neurons in the motor cortex, brainstem, and spinal cord. A large number of rodent models are available that show motor neuron death and a progressive motor phenotype that is more or less reminiscent of what occurs in patients. These rodent models contain genes with spontaneous or induced mutations or (over) express different (mutant) genes. Some of these models have been of great value to delineate potential pathogenic mechanisms that cause and/or modulate selective motor neuron degeneration. In addition, these genetic rodent models play a crucial role in testing and selecting potential therapeutics that can be used to treat ALS and/or other motor neuron disorders. In this paper, we give a systematic overview of the most important genetic rodent models that show motor neuron degeneration and/or develop a motor phenotype. In addition, we discuss the value and limitations of the different models and conclude that it remains a challenge to find more and better rodent models based on mutations in new genes causing ALS.

Deficits in axonal transport precede ALS symptoms in vivo

ALS is a fatal neurodegenerative disease characterized by selective motor neuron death resulting in muscle paralysis. Mutations in superoxide dismutase 1 (SOD1) are responsible for a subset of familial cases of ALS. Although evidence from transgenic mice expressing human mutant SOD1(G93A) suggests that axonal transport defects may contribute to ALS pathogenesis, our understanding of how these relate to disease progression remains unclear. Using an in vivo assay that allows the characterization of axonal transport in single axons in the intact sciatic nerve, we have identified clear axonal transport deficits in presymptomatic mutant mice. An impairment of axonal retrograde transport may therefore represent one of the earliest axonal pathologies in SOD1(G93A) mice, which worsens at an early symptomatic stage. A deficit in axonal transport may therefore be a key pathogenic event in ALS and an early disease indicator of motor neuron degeneration.

Ultrastructural diversity of inclusions and aggregations in the lumbar spinal cord of SOD1-G93A transgenic mice

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by selective motor neuron death. We report the characteristics of ultrastructural pathological changes of inclusions and aggregations in the neuronal axons, glial cells and ventral roots of lumbar spinal cord in SOD1-G93A transgenic mice using light and electron transmission microscope at different stages of disease. The most noteworthy is that mutant SOD1 accumulations in the cytoplasm of motor neurons precede the numerous inclusions. Inclusions manifested differently according to the specified locations. This study provided further information to the previous reports about pathological changes of ALS.

Amyotrophic Lateral Sclerosis and Excitotoxicity: From Pathological Mechanism to Therapeutic Target

Glutamate-induced excitotoxicity is responsible for neuronal death in acute neurological conditions as well as in chronic neurodegeneration. In this review, we give an overview of the contribution of excitotoxicity in the pathogenesis of amyotrophic lateral sclerosis (ALS). The selective motor neuron death that is the hallmark of this neurodegenerative disease seems to be related to a number of intrinsic characteristics of these neurons. Most of these characteristics relate to calcium entry and calcium handling in the motor neurons as intracellular free calcium concentrations increase quickly due to a high glutamate-induced calcium influx in combination with a low calcium buffering capacity. The high calcium influx is because of the presence of GluR2 lacking, calcium-permeable AMPA receptors while a low expression of calcium binding proteins explains the low calcium buffering capacity. In the absence of these proteins, mitochondria play an important role to remove calcium from the cytoplasm. While all of these characteristics make at least a subpopulation of motor neurons intrinsically very prone to AMPA receptor mediated excitotoxicity, this vulnerability is further increased by the disease process. Mutated genes as well as unknown factors do not only influence the intrinsic characteristics of the motor neurons, but also the properties of the surrounding astrocytes. In conclusion, excitotoxicity remains an intriguing pathological pathway that could not only explain the selectivity of the motor neuron death but also the role of surrounding non-neuronal cells in ALS. In addition, excitotoxicity is also an interesting drug-able target as indicated by the only FDA-approved drug, riluzole, as well as by a number of ongoing clinical trials.

Induction of parkinsonism‐related proteins in the spinal motor neurons of transgenic mouse carrying a mutant SOD1 gene

Amyotrophic lateral sclerosis is a progressive and fatal disease caused by selective death of motor neurons, and a number of these patients carry mutations in the superoxide dismutase 1 (SOD1) gene involved in ameliorating oxidative stress. Recent studies indicate that oxidative stress and disruption of mitochondrial homeostasis is a common mechanism for motor neuron degeneration in amyotrophic lateral sclerosis and the loss of midbrain dopamine neurons in Parkinson's disease. Therefore, the present study investigated the presence and alterations of familial Parkinson's disease-related proteins, PINK1 and DJ-1, in spinal motor neurons of G93ASOD1 transgenic mouse model of amyotrophic lateral sclerosis. Following onset of disease, PINK1 and DJ-1 protein expression increased in the spinal motor neurons. The activated form of p53 also increased and translocated to the nuclei of spinal motor neurons, followed by increased expression of p53-activated gene 608 (PAG608). This is the first report demonstrating that increased expression of PAG608 correlates with activation of phosphorylated p53 in spinal motor neurons of an amyotrophic lateral sclerosis model. These results provide further evidence of the profound correlations between spinal motor neurons of amyotrophic lateral sclerosis and parkinsonism-related proteins.

Aggregation of copper-zinc superoxide dismutase in familial and sporadic ALS.

Amyotrophic lateral sclerosis (ALS) is a progressive, fatal neurodegenerative disease characterized by the selective death of motor neurons. While the most common form of ALS is sporadic and has no known cause, a small subset of cases is familial because of underlying genetic mutations. The best-studies example of familial ALS is that caused by mutations in the protein copper-zinc superoxide dismutase. The formation of SOD1-rich inclusions in the spinal cord is an early and prominent feature of SOD1-linked familial ALS in human patients and animal models of this disease. These inclusions have been shown to consist of SOD1-rich fibrils, suggesting that the conversion of soluble SOD1 into amyloid fibrils may play an important role in the etiology of familial ALS. SOD1 is also present in inclusions found in spinal cords of sporadic ALS patients, allowing speculations to arise regarding a possible involvement of SOD1 in the sporadic form of this disease. We here review the recent research on the significance, causes, and mechanisms of SOD1 fibril formation from a biophysical perspective.

Microglia in pathogenesis of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a chronic neurodegenerative disorder characterized by selective death of motor neurons and progressive paralysis. Many hypotheses have been proposed to explain its pathogenesis. In recent years,one of the most studied hypotheses was the inflammatory response accompanying the motor neuron death. Microglia and its interactions with motor neurons play important roles in the development and progression of the inflammatory responses and the disease itself,which results in different new and potent therapeutic strategies of great clinical value.