Herpes simplex virus-type1 (HSV-1) impairs DNA repair in cortical neurons

Several findings suggest that Herpes simplex virus-1 (HSV-1) infection plays a role in the neurodegenerative processes that characterize Alzheimer's disease (AD), but the underlying mechanisms have yet to be fully elucidated. Here we show that HSV-1 productive infection in cortical neurons causes the accumulation of DNA lesions that include both single (SSBs) and double strand breaks (DSBs), which are reported to be implicated in the neuronal loss observed in neurodegenerative diseases. We demonstrate that HSV-1 downregulates the expression level of Ku80, one of the main components of non-homologous end joining (NHEJ), a major pathway for the repair of DSBs. We also provide data suggesting that HSV-1 drives Ku80 for proteasomal degradation and impairs NHEJ activity, leading to DSB accumulation. Since HSV-1 usually causes life-long recurrent infections, it is possible to speculate that cumulating damages, including those occurring on DNA, may contribute to virus induced neurotoxicity and neurodegeneration, further suggesting HSV-1 as a risk factor for neurodegenerative conditions

Screening of an endothelial cDNA library identifies the C-terminal region of Nedd5 as a novel autoantigen in systemic lupus erythematosus with psychiatric manifestations

Anti-endothelial-cell antibodies are associated with psychiatric manifestations in systemic lupus erythematosus (SLE). Our primary aim in this study was to seek and characterize molecules that behave as endothelial autoantigens in SLE patients with psychiatric manifestations. By screening a cDNA library from human umbilical artery endothelial cells with serum from an SLE patient with psychosis, we identified one positive strongly reactive clone encoding the C-terminal region (C-ter) of Nedd5, an intracytoplasmatic protein of the septin family. To evaluate anti-Nedd5 serum immunoreactivity, we analyzed by ELISA specific IgG responses in 17 patients with SLE and psychiatric manifestations (group A), 34 patients with SLE without psychiatric manifestations (group B), 20 patients with systemic sclerosis, 20 patients with infectious mononucleosis, and 35 healthy subjects. IgG specific to Nedd5 C-ter was present in 14 (27%) of the 51 SLE patients. The mean optical density value for IgG immunoreactivity to Nedd5 C-ter was significantly higher in patients of group A than in those of group B, those with infectious mononucleosis, or healthy subjects (0.17 ± 0.14 vs, respectively, 0.11 ± 0.07, P = 0.04; 0.11 ± 0.06, P = 0.034; and 0.09 ± 0.045, P = 0.003, on Student's t-test). Moreover, IgG immunoreactivity to Nedd5 C-ter was significantly higher in patients with systemic sclerosis than in patients of group B or healthy subjects (0.18 ± 0.18 vs, respectively, 0.11 ± 0.07, P = 0.046; and 0.09 ± 0.045, P = 0.003). The percentage of patients with anti-Nedd5 C-ter serum IgG was higher in group A than in group B (8 (47%) of 17, vs 6 (17%) of 34, P = 0.045, on Fisher's exact test). In order to clarify a possible mechanism by which Nedd5 might be autoantigenic, we observed that Nedd5 relocated from cytoplasm to the plasma membrane of EAhy926 endothelial cells after apoptotic stimuli. In conclusion, Nedd5 is a novel autoantigen of potential clinical importance that could be successfully used for a more thorough investigation of the pathogenesis of psychiatric manifestations in SLE. Although anti-Nedd5 autoantibodies are not specific to SLE, they are significantly associated with neuropsychiatric SLE and may represent immunological markers of psychiatric manifestations in this pathology

Il complesso della proteina chinasi DNA-PK: modulazione mediata dal peptide beta amiloide e coinvolgimento nella plasticità sinaptica

Il danno al DNA è stato descritto in diverse condizioni patologiche, incluse le malattie neurodegenerative. La subunità catalitica del complesso della DNA-PK (DNA-PKcs) è una proteina appartenente alla famiglia delle chinasi correlate alla fosfatidilinositolo-3-chinasi ed è un enzima chiave nella riparazione del danno a doppio filamento del DNA, la forma di lesione più pericolosa per l’integrità del genoma. Analisi biochimiche effettuate sulla corteccia cerebrale di individui affetti da malattia di Alzheimer (Alzheimer’s disease, AD) hanno mostrato che i livelli della proteina DNA-PKcs e la capacità di riparazione del DNA sono significativamente ridotti rispetto ai controlli. Il meccanismo molecolare responsabile di questa riduzione non è stato ancora identificato. In questo studio abbiamo dimostrato che concentrazioni subletali del peptide beta-Amiloide(Abeta) il principale fattore responsabile della patogenesi dell’AD, sono in grado di abrogare l’attività chinasica della DNA-PKcs in una linea di cellule PC12, attraverso differenti meccanismi. Questi risultati mostrano l’esistenza di una relazione causale tra l’accumulo del peptide Abeta e la compromissione della riparazione del DNA mediata dalla DNA-PKcs. Anche se la DNA-PKcs è principalmente localiazzata nel nucleo, più recentemente è stato mostrato che essa è anche presente all’interno dei “lipid rafts”, suggerendo che questa proteina possa avere un ruolo alternativo a quello della riparazione delle rotture a doppio filamento del DNA. Come prova a sostegno di questa ipotesi, noi abbiamo trovato che la DNA-PKcs è presente all’interno delle membrane sinaptiche associata alle subunità NR1 ed NR2A dei recettori NMDA e alla proteina delle densità postsinaptiche PSD95. Inoltre abbiamo osservato che la DNA-PKcs presente nelle mebrane sinaptiche mantiene la sua attività chinasica. Abbiamo infine esaminato l’effetto dell’inattivazione della DNA-PKcs sull’espressione della facilitazione sinaptica (paired pulse facilitation, PPF) e del potenziamento a lungo termine (long term potentiation, LTP) nella regione CA1 dell’ippocampo. La stimolazione tetanica (100Hz) in tali fibre ha indotto un LTP che è risultato essere ridotto in modo significativo in fettine derivanti da topi deficitari per la DNA-PKcs (topi SCID) rispetto a topi di controllo, mentre la PPF non ha mostrato differenze significative nei due gruppi di animali. Questi risultati indicano che la DNA-PKcs è coinvolta nella plasticità sinaptica.DNA damage has been documented in different pathological conditions, including neurodegenerative diseases. DNA-dependent protein-kinase catalytic subunit (DNA-PKcs), a member of the family of phosphatidylinositol 3-kinase-like kinases, is one of the key enzymes involved in repairing DNA double-strand breaks (DSBs), the most lethal form of DNA damage. Biochemical analysis on cerebral cortex of individuals affected by Alzheimer’s disease (AD) has showed that DNA-PKcs protein levels are significantly decreased as well as DNA repair activity. The molecular mechanisms responsible for this reduction have yet to be identified. Here we found that sublethal concentrations of exogenous Amyloid-beta(Abeta) peptide, the most important player in the pathogenesis of AD, abrogate DNA-PK activity in PC12 cells through different mechanisms. These data indicate a direct causal relationship between Abeta accumulation and the impairment of DNA-PKcs-mediated DNA repair. DNA-PKcs is mainly found in the nucleus. However, a recent study has showed that a fraction of DNA-PKcs is present in lipid rafts suggesting that DNA-PKcs may play alternative roles besides its main function in DSBs repair. Indeed, we found that DNA-PKcs is localized in synaptosomal fraction where is associated with NR1 and NR2A NMDA receptor subunits and with post synaptic density-95 protein (PSD95). Moreover, we observed that DNA-PKcs maintains its kinase activity in synaptosomal membranes. In addition, we examined the effect of DNA-PKcs inactivation on the expression of paired pulse facilitation (PPF) and on the early phase of long-term potentiation (LTP) at Schaffer collateral/commissural fiber–CA1 hippocampal synapses. Tetanic stimulation (100Hz, 1s) induced LTP with values that were significantly lower in slices from DNA-PKcs-deficient mice (SCID mice) as compared with control animals, whereas PPF was not different in the two group of animals. These findings strongly indicated that DNA-PKcs may be involved in synaptic plasticity

The Response to Oxidative DNA Damage in Neurons: Mechanisms and Disease

There is a growing body of evidence indicating that the mechanisms that control genome stability are of key importance in the development and function of the nervous system. The major threat for neurons is oxidative DNA damage, which is repaired by the base excision repair (BER) pathway. Functional mutations of enzymes that are involved in the processing of single-strand breaks (SSB) that are generated during BER have been causally associated with syndromes that present important neurological alterations and cognitive decline. In this review, the plasticity of BER during neurogenesis and the importance of an efficient BER for correct brain function will be specifically addressed paying particular attention to the brain region and neuron-selectivity in SSB repair-associated neurological syndromes and age-related neurodegenerative diseases

Downregulation of thymosin beta4 in neural progenitor grafts promotes spinal cord regeneration

Thymosin \uce\ub24 (T\uce\ub24) is an actin-binding peptide whose expression in developing brain correlates with migration and neurite extension of neurons. Here, we studied the effects of the downregulation of T\uce\ub24 expression on growth and differentiation of murine neural progenitor cells (NPCs), using an antisense lentiviral vector. In differentiation-promoting medium, we found twice the number of neurons derived from the T\uce\ub24-antisense-transduced NPCs, which showed enhanced neurite outgrowth accompanied by increased expression of the adhesion complex N-cadherin-\uce\ub2-catenin and increased ERK activation. Importantly, when the T\uce\ub24-antisense-transduced NPCs were transplanted in vivo into a mouse model of spinal cord injury, they promoted a significantly greater functional recovery. Locomotory recovery correlated with increased expression of the regeneration-promoting cell adhesion molecule L1 by the grafted T\uce\ub24-antisense-transduced NPCs. This resulted in an increased number of regenerating axons and in sprouting of serotonergic fibers surrounding and contacting the T\uce\ub24-antisense-transduced NPCs grafted into the lesion site. In conclusion, our data identify a new role for T\uce\ub24 in neuronal differentiation of NPCs by regulating fate determination and process outgrowth. Moreover, NPCs with reduced T\uce\ub24 levels generate an L1-enriched environment in the lesioned spinal cord that favors growth and sprouting of spared host axons and enhances the endogenous tissue-repair processes

New ways of initiating translation in eukaryotes.

CommentLetterinfo:eu-repo/semantics/publishe