The role of proteasome dysfunction in the mechanisms of motor neuron degeneration in a mouse model of familial amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the loss of the motor neurons. One consistent neuropathological feature of ALS patients and models of the disease is the formation of proteinaceous inclusion bodies; for this reason, alterations in the proteolytic ubiquitin-proteasome pathway (UPP) have been suggested to be implicated. The purpose of this thesis was to analyze the role of the UPP in ALS pathogenesis studying the G93A mouse model. The activity of UPP was evaluated in G93A mice carrying the UbG76V-GFP reporter protein for proteasomal functionality. Furthermore, the expression of different constitutive proteasome and immunoproteasome subunits was measured during disease progression. In symptomatic G93A lumbar spinal cord, a mild increase of UbG76V-GFP protein, but not of its transcript, was found in the motor neuronal population and was partly associated with high levels of ubiquitin and perikarial presence of phosphorylated neurofilaments. At the end stage, the increase of the reporter protein was prevalent in other neurons besides motor neurons, but also the mRNA levels were augmented. Constitutive catalytic subunits of the 20S proteasome were reduced in end stage G93A lumbar spinal cord, while an increase of their inducible counterparts and a decrease of the non-catalytic as subunit were evident at the symptomatic phase. Components of 19S and 11S complexes were significantly reduced prior to symptom onset. The changes in proteasome composition were accompanied by a substantial increase of glial markers and TNFα. Altogether, these data suggest that a subtle dysfunction of the ubiquitin-proteasome pathway occurs in the spinal cord of a mouse model of ALS in a phase in which the first signs of motor impairment are detectable. This pairs with alterations in the transcriptional rate of various proteasome subunits, resulting in a decrease of constitutive proteasome and an increase of immunoproteasome

Clinical Study Cirrhosis and Rapid Virological Response to Peginterferon Plus Ribavirin Determine Treatment Outcome in HCV-1 IL28B rs12979860 CC Patients

Background. The rs12979860 CC genotype of the interleukin 28B (IL28B) polymorphism is associated with high rates of sustained virological response (SVR) to peginterferon (PegIFN) and ribavirin (Rbv) in hepatitis C virus genotype-1 (HCV-1) patients. The impact of baseline predictors of treatment outcome and their interplay with viral kinetics in HCV-1 CC patients has not been fully evaluated. Aim. To identify baseline and on-therapy predictors of treatment failure in HCV-1 IL28B CC patients. Methods. Treatment-naïve HCV-1 patients, compliant to PegIFN and Rbv who did not discontinue treatment for nonvirological reasons, were analyzed. Results. 109 HCV-1 IL28B CC were studied. Sixty were males, 39 with BMI >25, 69 with >600,000 IU/mL HCV RNA, 15 with HCV1a, and 30 with cirrhosis. Overall, 75 (69%) achieved an SVR; cirrhosis was the only baseline predictor of treatment failure (OR: 2.58, 95% CI: 1.07-6.21) as SVR rates were 53% in cirrhotics versus 75% in noncirrhotics ( = 0.03). HCV RNA undetectability (<50 IU/mL) at week 4 (RVR) was achieved by 58 patients (53%). The SVR rates were independent of RVR in noncirrhotics, 76% (34/45) RVR (+) and 74% (25/34) RVR (−) ( = 0.9). In cirrhotic patients, SVR rates were significantly higher in RVR (+) compared to RVR (−) (10/13 (77%) versus 6/17 (35%) = 0.03). Conclusions. In HCV-1 IL28B CC patients, cirrhosis is the only clinical baseline predictor of PegIFN and Rbv treatment failure. However, in IL28B CC cirrhotics, the achievement of RVR identifies those patients who still have high rates of SVR to Peg-IFN/Rbv therapy

Characterization of Detergent-Insoluble Proteins in ALS Indicates a Causal Link between Nitrative Stress and Aggregation in Pathogenesis

BACKGROUND:Amyotrophic lateral sclerosis (ALS) is a progressive and fatal motor neuron disease, and protein aggregation has been proposed as a possible pathogenetic mechanism. However, the aggregate protein constituents are poorly characterized so knowledge on the role of aggregation in pathogenesis is limited. METHODOLOGY/PRINCIPAL FINDINGS:We carried out a proteomic analysis of the protein composition of the insoluble fraction, as a model of protein aggregates, from familial ALS (fALS) mouse model at different disease stages. We identified several proteins enriched in the detergent-insoluble fraction already at a preclinical stage, including intermediate filaments, chaperones and mitochondrial proteins. Aconitase, HSC70 and cyclophilin A were also significantly enriched in the insoluble fraction of spinal cords of ALS patients. Moreover, we found that the majority of proteins in mice and HSP90 in patients were tyrosine-nitrated. We therefore investigated the role of nitrative stress in aggregate formation in fALS-like murine motor neuron-neuroblastoma (NSC-34) cell lines. By inhibiting nitric oxide synthesis the amount of insoluble proteins, particularly aconitase, HSC70, cyclophilin A and SOD1 can be substantially reduced. CONCLUSION/SIGNIFICANCE:Analysis of the insoluble fractions from cellular/mouse models and human tissues revealed novel aggregation-prone proteins and suggests that nitrative stress contribute to protein aggregate formation in ALS

SBDS-Deficient Cells Have an Altered Homeostatic Equilibrium due to Translational Inefficiency Which Explains their Reduced Fitness and Provides a Logical Framework for Intervention

Ribosomopathies are a family of inherited disorders caused by mutations in genes necessary for ribosomal function. Shwachman-Diamond Bodian Syndrome (SDS) is an autosomal recessive disease caused, in most patients, by mutations of the SBDS gene. SBDS is a protein required for the maturation of 60S ribosomes. SDS patients present exocrine pancreatic insufficiency, neutropenia, chronic infections, and skeletal abnormalities. Later in life, patients are prone to myelodisplastic syndrome and acute myeloid leukemia (AML). It is unknown why patients develop AML and which cellular alterations are directly due to the loss of the SBDS protein. Here we derived mouse embryonic fibroblast lines from an SbdsR126T/R126T mouse model. After their immortalization, we reconstituted them by adding wild type Sbds. We then performed a comprehensive analysis of cellular functions including colony formation, translational and transcriptional RNA-seq, stress and drug sensitivity. We show that: 1. Mutant Sbds causes a reduction in cellular clonogenic capability and oncogene-induced transformation. 2. Mutant Sbds causes a marked increase in immature 60S subunits, limited impact on mRNA specific initiation of translation, but reduced global protein synthesis capability. 3. Chronic loss of SBDS activity leads to a rewiring of gene expression with reduced ribosomal capability, but increased lysosomal and catabolic activity. 4. Consistently with the gene signature, we found that SBDS loss causes a reduction in ATP and lactate levels, and increased susceptibility to DNA damage. Combining our data, we conclude that a cell-specific fragile phenotype occurs when SBDS protein drops below a threshold level, and propose a new interpretation of the disease

GTF2I dosage regulates neuronal differentiation and social behavior in 7q11.23 neurodevelopmental disorders

Copy number variations at 7q11.23 cause neurodevelopmental disorders with shared and opposite manifestations. Deletion causes Williams-Beuren syndrome featuring hypersociability, while duplication causes 7q11.23 microduplication syndrome (7Dup), frequently exhibiting autism spectrum disorder (ASD). Converging evidence indicates GTF2I as key mediator of the cognitive-behavioral phenotypes, yet its role in cortical development and behavioral hallmarks remains largely unknown.We integrated proteomic and transcriptomic profiling of patient-derived cortical organoids, including longitudinally at single-cell resolution, to dissect 7q11.23 dosage–dependent and GTF2I-specific disease mechanisms. We observed dosage-dependent impaired dynamics of neural progenitor proliferation, transcriptional imbalances, and highly specific alterations in neuronal output, leading to precocious excitatory neuron production in 7Dup, which was rescued by restoring physiological GTF2I levels. Transgenic mice with Gtf2i duplication recapitulated progenitor proliferation and neuronal differentiation defects alongside ASD-like behaviors. Consistently, inhibition of lysine demethylase 1 (LSD1), a GTF2I effector, was sufficient to rescue ASD-like phenotypes in transgenic mice, establishing GTF2I-LSD1 axis as a molecular pathway amenable to therapeutic intervention in ASD

Lack of changes in the PI3K/AKT survival pathway in the spinal cord motor neurons of a mouse model of familial amyotrophic lateral sclerosis.

The vulnerability of motor neurons in transgenic SOD1G93A mice, a model of familial amyotrophic lateral sclerosis (ALS), may depend on the failure of these cells to activate survival mechanisms in response to the toxic mutant SOD1. To test this we investigated whether defects in the PI3K/Akt pathway, a survival signal, and of its neuron-specific activator, Rai, were important for motor neuron degeneration in these mice. No substantial changes were found in the levels of Rai, PI3K(p85) or phosphorylated Akt (P-Akt) in the ventral horn of spinal cord of SOD1G93A mice during disease progression. P-Akt immunoreactivity was the same in degenerating and healthy motor neurons. Rai ablation in SOD1G93A mice slightly accelerated the motor dysfunction without affecting their life span. Thus, motor neurons in SOD1G93A mice do not lose the pro-survival PI3K/Akt signal nor increase it in order to suppress the cell death mechanisms

Cirrhosis and Rapid Virological Response to Peginterferon Plus Ribavirin Determine Treatment Outcome in HCV-1 IL28B rs12979860 CC Patients

Background. The rs12979860 CC genotype of the interleukin 28B (IL28B) polymorphism is associated with high rates of sustained virological response (SVR) to peginterferon (PegIFN) and ribavirin (Rbv) in hepatitis C virus genotype-1 (HCV-1) patients. The impact of baseline predictors of treatment outcome and their interplay with viral kinetics in HCV-1 CC patients has not been fully evaluated. Aim. To identify baseline and on-therapy predictors of treatment failure in HCV-1 IL28B CC patients. Methods. Treatment-naïve HCV-1 patients, compliant to PegIFN and Rbv who did not discontinue treatment for nonvirological reasons, were analyzed. Results. 109 HCV-1 IL28B CC were studied. Sixty were males, 39 with BMI >25, 69 with >600,000 IU/mL HCV RNA, 15 with HCV1a, and 30 with cirrhosis. Overall, 75 (69%) achieved an SVR; cirrhosis was the only baseline predictor of treatment failure (OR: 2.58, 95% CI: 1.07–6.21) as SVR rates were 53% in cirrhotics versus 75% in noncirrhotics (P=0.03). HCV RNA undetectability (<50 IU/mL) at week 4 (RVR) was achieved by 58 patients (53%). The SVR rates were independent of RVR in noncirrhotics, 76% (34/45) RVR (+) and 74% (25/34) RVR (−) (P=0.9). In cirrhotic patients, SVR rates were significantly higher in RVR (+) compared to RVR (−) (10/13 (77%) versus 6/17 (35%) P=0.03). Conclusions. In HCV-1 IL28B CC patients, cirrhosis is the only clinical baseline predictor of PegIFN and Rbv treatment failure. However, in IL28B CC cirrhotics, the achievement of RVR identifies those patients who still have high rates of SVR to Peg-IFN/Rbv therapy

ADAM10 hyperactivation acts on piccolo to deplete synaptic vesicle stores in Huntington’s disease

Synaptic dysfunction and cognitive decline in Huntington’s disease (HD) involve hyperactive A disintegrin and metalloproteinase domain-containing protein 10 (ADAM10). To identify the molecular mechanisms through which ADAM10 is associated with synaptic dysfunction in HD, we performed an immunoaffinity purification-mass spectrometry (IP-MS) study of endogenous ADAM10 in the brains of wild-type and HD mice. In the normal brain, proteins implicated in synapse organization, synaptic plasticity, and vesicle and organelles trafficking interact with ADAM10, suggesting that it may act as a hub protein at the excitatory synapse. Importantly, the ADAM10 interactome is enriched in presynaptic proteins and ADAM10 coimmunoprecipitates with piccolo (PCLO), a key player in the recycling and maintenance of synaptic vesicles (SVs). In contrast, reduced ADAM10/PCLO immunoprecipitation occurs in the HD brain, with decreased density of SVs in the reserve and docked pool at the HD presynaptic terminal. Conditional heterozygous deletion of ADAM10 in the forebrain of HD mice reduces active ADAM10 to wild-type level, and normalizes ADAM10/PCLO complex formation and SVs density and distribution. The results indicate that presynaptic ADAM10 and PCLO are a relevant component of HD pathogenesis

DEPDC5 variants increase fibrosis progression in Europeans with chronic HCV infection

Chronic hepatitis C virus (HCV) infection may progress to cirrhosis and hepatocellular carcinoma (HCC). Recently, two genetic variants, DEPDC5 rs1012068 and MICA rs2596542, were associated with the onset of HCC in Asian subjects with chronic HCV infection. The aim of the present study was to analyze whether DEPDC5 and MICA genetic variants were associated with liver disease progression in Europeans with chronic HCV infection. In a Northern Italian discovery cohort (n=477), neither DEPDC5 rs1012068 nor MICA rs2596542 were associated with HCC (n=150). However, DEPDC5 rs1012068 was independently associated with cirrhosis (n=300; p=0.049). The association of rs1012068 with moderate-severe fibrosis was confirmed in an independent cross-sectional German cohort (n=415; p=0.006). Furthermore, DEPDC5 rs1012068 predicted faster fibrosis progression in a prospective cohort (n=247; p=0.027). Next, we examined the distribution of non-synonymous DEPDC5 variants in the overall cross-sectional cohort (n=912). The presence of at least one variant increased the risk of moderate/severe fibrosis by 54% (p=0.040). To understand the molecular mechanism underlying the genetic association of DEPDC5 variants with fibrosis progression, we performed in vitro studies on immortalized hepatic stellate cells (LX-2). In these cells, down-regulation of DEPDC5 resulted in increased expression of β-catenin and production of its target matrix metallopeptidase 2 (MMP2), a secreted enzyme involved in fibrosis progression. CONCLUSION: DEPDC5 variants increase fibrosis progression in Europeans with chronic HCV infection. Our findings suggest that DEPDC5 down-regulation may contribute to HCV-related fibrosis by increasing MMP2 synthesis through the β-catenin pathway