Interaction between a Novel Oligopeptide Fragment of the Human Neurotrophin Receptor TrkB Ectodomain D5 and the C-Terminal Fragment of Tetanus Neurotoxin

This article presents experimental evidence and computed molecular models of a potential interaction between receptor domain D5 of TrkB with the carboxyl-terminal domain of tetanus neurotoxin (Hc-TeNT). Computational simulations of a novel small cyclic oligopeptide are designed, synthesized, and tested for possible tetanus neurotoxin-D5 interaction. A hot spot of this protein-protein interaction is identified in analogy to the hitherto known crystal structures of the complex between neurotrophin and D5. Hc-TeNT activates the neurotrophin receptors, as well as its downstream signaling pathways, inducing neuroprotection in different stress cellular models. Based on these premises, we propose the Trk receptor family as potential proteic affinity receptors for TeNT. In vitro, Hc-TeNT binds to a synthetic TrkB-derived peptide and acts similar to an agonist ligand for TrkB, resulting in phosphorylation of the receptor. These properties are weakened by the mutagenesis of three residues of the predicted interaction region in Hc-TeNT. It also competes with Brain-derived neurotrophic factor, a native binder to human TrkB, for the binding to neural membranes, and for uptake in TrkB-positive vesicles. In addition, both molecules are located together in vivo at neuromuscular junctions and in motor neurons

Interacción de las neurotoxinas clostridiales con los receptores de neurotrofinas : identificación de TrkB como receptor proteico de la toxina tetánica /

La toxina tetánica (TeNT) es una potente neurotoxina clostridial causante de la enfermedad del tétanos. Actúa en el sistema nervioso periférico y central bloqueando la neurotransmisión inhibitoria y causando una parálisis espástica del músculo. Su extrema neuroespecificidad viene determinada por la interacción de su dominio carboxilo terminal (Hc TeNT) con las membranas neuronales mediante un mecanismo de receptor dual. Primeramente interacciona con los polisialogangliósidos, presentes en gran cantidad en la membrana plasmática, y en segundo lugar con un receptor proteico de alta afinidad que permite su endocitosis en la neurona. Aunque aún se desconoce cuál es este receptor proteico, se ha descrito que la TeNT comparte la misma ruta endocítica que las neurotrofinas y sus receptores. Las neurotrofinas son una familia de factores de crecimiento que regulan el desarrollo, el mantenimiento y la función del sistema nervioso. La interacción con sus receptores Trk (TrkA, TrkB y TrkC) y p75NTR desencadena la activación de diversas vías de señalización como la vía PI3K/Akt, la Ras/MAPK y la PLCγ/PKC, que derivan en la inducción de la supervivencia neuronal y la diferenciación. El Hc TeNT es capaz de activar a estos receptores de neurotrofinas, así como a las vías de señalización dependientes de ellos, provocando un efecto neuroprotector en distintos modelos celulares sometidos a estrés. Basándonos en estas premisas proponemos que la TeNT podría actuar sobre las neuronas mimetizando a las neurotrofinas, uniéndose a sus receptores y aprovechando su maquinaria de transporte retroaxonal para su proceso infectivo. En este trabajo se presentan evidencias que identifican al receptor TrkB como receptor proteico para la TeNT. El Hc TeNT es capaz de unirse a un péptido derivado de un dominio extracelular de TrkB y de inducir la fosforilación de éste receptor, propiedades que parecen debilitarse al mutar tres residuos de Hc TeNT en la zona de unión teórica. También compite con su agonista nativo por la unión a membranas neuronales y por la internalización junto a TrkB. Ambas moléculas además localizan conjuntamente in vivo en las uniones neuromusculares y en las motoneuronas. Centrándonos en el efecto neuroprotector observado en Hc TeNT, nos proponemos también estudiar la respuesta de la célula frente al tratamiento con neurotrofinas y con Hc TeNT después de un estímulo apoptótico, para determinar qué receptores participan, qué vías de señalización se activan y la implicación de la esfingomielinasa neutra (nSMasa) en el proceso. La nSMasa es activada por el receptor p75NTR e hidroliza la esfingomielina presente en las membranas generando ceramida, que actúa como segundo mensajero interviniendo en procesos tan dispares como la apoptosis o la supervivencia. Se ha observado que las neurotrofinas promueven la viabilidad celular actuando a través de los receptores Trk, de forma dependiente de los niveles basales de nSMasa pero no mediante el incremento de la actividad de ésta. La respuesta de supervivencia inducida por el Hc TeNT también depende de nSMasa, ya que al inhibirla o silenciarla anula este efecto. La capacidad del Hc TeNT de pasar del SNP hasta el SNC mediante saltos transinápticos, así como sus propiedades neuroprotectoras, son características de gran interés que podrían ser aplicadas en el desarrollo y la administración de fármacos al SNCTetanus neurotoxin (TeNT) is a potent clostridial neurotoxin causing tetanus disease. It acts on peripheral and CNS blocking inhibitory neurotransmission and causing spastic paralysis in the muscle. Its extreme neurospecificity is determined by the interaction of the carboxyl-terminal domain (Hc-TeNT) with neuronal membranes via a dual-receptor mechanism. TeNT first binds to polysialogangliosides, and then to a second specific protein receptor that promotes its uptake. Although this protein receptor is not known yet, it has been reported that TeNT shares the same endocytic route with neurotrophins and their receptors. Neurotrophins are a family of growth factors that regulate development, maintenance and function of nervous system. The interaction with their receptors Trk (TrkA, TrkB and TrkC) and p75NTR triggers the activation of various signaling pathways like PI3K/Akt, Ras/MAPK and PLCγ/PKC, promoting neuronal survival and differentiation. Hc TeNT activates the neurotrophin receptors, as well as several signaling pathways dependent on them, inducing a neuroprotector effect in diverse cellular models. Based on these premises, we propose that TeNT acts on neurons mimicking the neurotrophins, binds to its receptors, and uses their machinery of retroaxonal transport in its infective process. In this work we present evidences that identify TrkB as a protein receptor for TeNT. Hc TeNT binds to a TrkB extracellular domain-derived peptide and acts similar to an agonist ligand for TrkB, resulting in phosphorylation of the receptor. These properties are weakened by mutagenesis of three residues of the hypothetical interaction region in Hc TeNT. It also competes with BDNF, a TrkB native ligand, for the binding to neural membranes, and for uptake in TrkB-positive vesicles. Both molecules also are located together in vivo at neuromuscular junctions and in motor neurons. Focusing on the neuroprotective effect observed for Hc TeNT, we also intend to study the cell response to treatment with neurotrophins and Hc TeNT after apoptotic stimulus. The objective is to determine which neurotrophin receptors are involved, which signaling pathways are activated and the involvement of neutral sphingomyelinase (nSMase) in the process. SMase is activated by p75NTR receptor and hydrolyzes sphingomyelin located in the membranes obtaining ceramide, which acts as a second messenger intervening in such diverse processes as apoptosis or cell survival. We find that neurotrophins promote cellular viability through Trk receptors in a manner depending on basal nSMase but not through SMase activity enhancement. Hc TeNT also induces survival in a nSMase dependent manner, since an nSMase inhibitor or siRNA knockdown abrogates its protective effects. Hc TeNT capacity to move from SNP to the CNS as well as its neuroprotective properties are characteristics of great interest that could be applied in the development and delivery of drugs to the CNS

Intra-hippocampal d-cycloserine rescues decreased social memory, spatial learning reversal, and synaptophysin levels in aged rats

Aging is characterized by a decrease in N-methyl-D-aspartate receptors (NMDARs) in the hippocampus, which might be one of the factors involved in the age-dependent cognitive decline. D-Cycloserine (DCS), a partial agonist of the NMDAR glycine recognition site, could improve memory deficits associated to neurodegenerative disorders and cognitive deficits observed in normal aging. Objectives and Methods: The aim of the present study was to explore whether DCS would reverse age-dependent memory deficits and decreases in NMDA receptor subunits (GluN1, GluN2A, and GluN2B) and the presynaptic protein synaptophysin in Wistar rats. We investigated the effects of pre-training infusions of DCS (10 μg/hemisphere) in the ventral hippocampus on two hippocampal-dependent learning tasks, the social transmission of food preference (STFP), and the Morris water maze (MWM). Results: The results revealed that infusions of DCS administered before the acquisition sessions rescued deficits in the STFP retention and MWM reversal learning in old rats. DCS also significantly increased the hippocampal levels of synaptophysin in old rats, which correlated with STFP and MWM performance in all tests. Moreover, although the levels of the GluN1 subunit correlated with the MWM acquisition and reversal, DCS did not enhance the expression of such synaptic protein. Conclusions: The present behavioral results support the role of DCS as a cognitive enhancer and suggest that enhancing the function of NMDARs and synaptic plasticity in the hippocampus may be related to improvement in social memory and spatial learning reversal in aged animals

C9orf72-ALS human iPSC microglia are pro-inflammatory and toxic to co-cultured motor neurons via MMP9

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by progressive motor neuron loss, with additional pathophysiological involvement of non-neuronal cells such as microglia. The commonest ALS-associated genetic variant is a hexanucleotide repeat expansion (HRE) mutation in C9orf72. Here, we study its consequences for microglial function using human iPSC-derived microglia. By RNA-sequencing, we identify enrichment of pathways associated with immune cell activation and cyto-/chemokines in C9orf72 HRE mutant microglia versus healthy controls, most prominently after LPS priming. Specifically, LPS-primed C9orf72 HRE mutant microglia show consistently increased expression and release of matrix metalloproteinase-9 (MMP9). LPS-primed C9orf72 HRE mutant microglia are toxic to co-cultured healthy motor neurons, which is ameliorated by concomitant application of an MMP9 inhibitor. Finally, we identify release of dipeptidyl peptidase-4 (DPP4) as a marker for MMP9-dependent microglial dysregulation in co-culture. These results demonstrate cellular dysfunction of C9orf72 HRE mutant microglia, and a non-cell-autonomous role in driving C9orf72-ALS pathophysiology in motor neurons through MMP9 signaling

An ALS-linked mutation in TDP-43 disrupts normal protein interactions in the motor neuron response to oxidative stress

TDP-43 pathology is a key feature of amyotrophic lateral sclerosis (ALS), but the mechanisms linking TDP-43 to altered cellular function and neurodegeneration remain unclear. We have recently described a mouse model in which human wild-type or mutant TDP-43 are expressed at low levels and where altered stress granule formation is a robust phenotype of TDP-43M337V/− expressing cells. In the present study we use this model to investigate the functional connectivity of human TDP-43 in primary motor neurons under resting conditions and in response to oxidative stress. The interactome of human TDP-43WT or TDP-43M337V was compared by mass spectrometry, and gene ontology enrichment analysis identified pathways dysregulated by the M337V mutation. We found that under normal conditions the interactome of human TDP-43WT was enriched for proteins involved in transcription, translation and poly(A)-RNA binding. In response to oxidative stress, TDP-43WT recruits proteins of the endoplasmic reticulum and endosomal-extracellular transport pathways, interactions which are reduced in the presence of the M337V mutation. Specifically, TDP-43M337V impaired protein-protein interactions involved in stress granule formation including reduced binding to the translation initiation factors Poly(A)-binding protein and Eif4a1 and the endoplasmic reticulum chaperone Grp78. The M337V mutation also affected interactions involved in endosomal-extracellular transport and this this was associated with reduced extracellular vesicle secretion in primary motor neurons from TDP-43M337V/− mice and in human iPSCs-derived motor neurons. Taken together, our analysis highlights a TDP-43 interaction network in motor neurons and demonstrates that an ALS associated mutation may alter the interactome to drive aberrant pathways involved in the pathogenesis of ALS.TDP-43 pathology is a key feature of amyotrophic lateral sclerosis (ALS), but the mechanisms linking TDP-43 to altered cellular function and neurodegeneration remain unclear. We have recently described a mouse model in which human wild-type or mutant TDP-43 are expressed at low levels and where altered stress granule formation is a robust phenotype of TDP-43M337V/− expressing cells. In the present study we use this model to investigate the functional connectivity of human TDP-43 in primary motor neurons under resting conditions and in response to oxidative stress. The interactome of human TDP-43WT or TDP-43M337V was compared by mass spectrometry, and gene ontology enrichment analysis identified pathways dysregulated by the M337V mutation. We found that under normal conditions the interactome of human TDP-43WT was enriched for proteins involved in transcription, translation and poly(A)-RNA binding. In response to oxidative stress, TDP-43WT recruits proteins of the endoplasmic reticulum and endosomal-extracellular transport pathways, interactions which are reduced in the presence of the M337V mutation. Specifically, TDP-43M337V impaired protein-protein interactions involved in stress granule formation including reduced binding to the translation initiation factors Poly(A)-binding protein and Eif4a1 and the endoplasmic reticulum chaperone Grp78. The M337V mutation also affected interactions involved in endosomal-extracellular transport and this this was associated with reduced extracellular vesicle secretion in primary motor neurons from TDP-43M337V/− mice and in human iPSCs-derived motor neurons. Taken together, our analysis highlights a TDP-43 interaction network in motor neurons and demonstrates that an ALS associated mutation may alter the interactome to drive aberrant pathways involved in the pathogenesis of ALS

Experiencias de Innovación docente en los Estudios Jurídicos: una visión práctica

Esta publicación se enmarca dentro de las actividades del Grupo de Investigación de la Universidad de Extremadura Fiscalitas & Iuris.Este trabajo surge con el objetivo principal de dar visibilidad y publicidad a las nuevas técnicas docentes en el seno de la Facultad de Derecho de la UEx. Como se sabe, se ha producido un innegable y significativo avance en el uso de nuevas técnicas docentes y también de las TICs aplicadas a la docencia en la Facultad de Derecho, no obstante, aún es necesario profundizar en el uso de las mismas y extenderlas entre todos los miembros del claustro de profesores, y fundamentalmente entre aquellos que llevan más años ejerciendo la docencia a través de la colaboración y la coordinación con los profesores noveles, que son quienes principalmente se sirven en mayor medida de tales instrumentos docentes. De otra parte, también era necesario que los docentes más experimentados pudieran encontrar un foro en el que transmitir y compartir con los noveles cuales son las técnicas e instrumentos docentes que ellos han venido utilizando durante el ejercicio de su magisterio, de modo que, en el marco de una relación sinalagmática, se produjera una interacción entre uno u otro grupo de docentes, a fin de fomentar el necesario debate y el intercambio de experiencias e instrumentos docentes, y en su caso el desarrollo y perfeccionamiento de los mismos; algo que hemos pretendido realizar con este trabajo, y que en buena medida hemos logrado. Las finalidades y objetivos concretos que perseguíamos, en atención a la situación expuesta eran fundamentalmente tres: • En primer lugar, la implementación de un proyecto de innovación docente integrado por una diversidad de actividades coordinadas, cada uno de ellas bajo la directa coordinación de un profesor o profesora de la UEx, aplicado a una o varias asignaturas impartidas en la Facultad de Derecho. • En segundo lugar, el establecimiento en la Facultad de Derecho de un foro de coordinación e intercambio de buenas prácticas docentes sobre la base de cada uno de las actividades coordinadas, en el que pudieran participar profesores noveles y veteranos. Para ello se desarrolló espacio virtual de innovación docente en estudios jurídicos, a través del Campus Virtual de la UEx, en el que los Profesores noveles y veteranos pudieron y puede compartir recursos e informaciones sobre prácticas de innovación. • Y, en tercer lugar, la difusión y consolidación de instrumentos de innovación docente directamente aplicadas a la docencia de los estudios jurídicos, mediante la transferencia de los resultados y la publicación de los mismos; a fin de que esta transferencia sirva de base a futuras profundizaciones en el campo de la innovación docente en los estudios jurídicos.Proyecto “Desarrollo, profundización e intercambio de buenas prácticas de innovación docente en la Facultad de Derecho” (UEx 2015-2016

Truncated stathmin-2 is a marker of TDP-43 pathology in frontotemporal dementia.

No treatment for frontotemporal dementia (FTD), the second most common type of early-onset dementia, is available, but therapeutics are being investigated to target the 2 main proteins associated with FTD pathological subtypes: TDP-43 (FTLD-TDP) and tau (FTLD-tau). Testing potential therapies in clinical trials is hampered by our inability to distinguish between patients with FTLD-TDP and FTLD-tau. Therefore, we evaluated truncated stathmin-2 (STMN2) as a proxy of TDP-43 pathology, given the reports that TDP-43 dysfunction causes truncated STMN2 accumulation. Truncated STMN2 accumulated in human induced pluripotent stem cell-derived neurons depleted of TDP-43, but not in those with pathogenic TARDBP mutations in the absence of TDP-43 aggregation or loss of nuclear protein. In RNA-Seq analyses of human brain samples from the NYGC ALS cohort, truncated STMN2 RNA was confined to tissues and disease subtypes marked by TDP-43 inclusions. Last, we validated that truncated STMN2 RNA was elevated in the frontal cortex of a cohort of patients with FTLD-TDP but not in controls or patients with progressive supranuclear palsy, a type of FTLD-tau. Further, in patients with FTLD-TDP, we observed significant associations of truncated STMN2 RNA with phosphorylated TDP-43 levels and an earlier age of disease onset. Overall, our data uncovered truncated STMN2 as a marker for TDP-43 dysfunction in FTD

Tetanus toxin Hc fragment induces the formation of ceramide platforms and protects neuronal cells against oxidative stress

Tetanus toxin (TeTx) is the protein, synthesized by the anaerobic bacteria Clostridium tetani, which causes tetanus disease. TeTx gains entry into target cells by means of its interaction with lipid rafts, which are membrane domains enriched in sphingomyelin and cholesterol. However, the exact mechanism of host membrane binding remains to be fully established. In the present study we used the recombinant carboxyl terminal fragment from TeTx (Hc-TeTx), the domain responsible for target neuron binding, showing that Hc-TeTx induces a moderate but rapid and sustained increase in the ceramide/sphingomyelin ratio in primary cultures of cerebellar granule neurons and in NGF-differentiated PC12 cells, as well as induces the formation of ceramide platforms in the plasma membrane. The mentioned increase is due to the promotion of neutral sphingomyelinase activity and not to the de novo synthesis, since GW4869, a specific neutral sphingomyelinase inhibitor, prevents neutral sphingomyelinase activity increase and formation of ceramide platforms. Moreover, neutral sphingomyelinase inhibition with GW4869 prevents Hc-TeTx-triggered signaling (Akt phosphorylation), as well as the protective effect of Hc-TeTx on PC12 cells subjected to oxidative stress, while siRNA directed against nSM2 prevents protection by Hc-TeTx of NSC-34 cells against oxidative insult. Finally, neutral sphingomyelinase activity seems not to be related with the internalization of Hc-TeTx into PC12 cells. Thus, the presented data shed light on the mechanisms triggered by TeTx after membrane binding, which could be related with the events leading to the neuroprotective action exerted by the Hc-TeTx fragment

Healthcare workers hospitalized due to COVID-19 have no higher risk of death than general population. Data from the Spanish SEMI-COVID-19 Registry

Aim To determine whether healthcare workers (HCW) hospitalized in Spain due to COVID-19 have a worse prognosis than non-healthcare workers (NHCW). Methods Observational cohort study based on the SEMI-COVID-19 Registry, a nationwide registry that collects sociodemographic, clinical, laboratory, and treatment data on patients hospitalised with COVID-19 in Spain. Patients aged 20-65 years were selected. A multivariate logistic regression model was performed to identify factors associated with mortality. Results As of 22 May 2020, 4393 patients were included, of whom 419 (9.5%) were HCW. Median (interquartile range) age of HCW was 52 (15) years and 62.4% were women. Prevalence of comorbidities and severe radiological findings upon admission were less frequent in HCW. There were no difference in need of respiratory support and admission to intensive care unit, but occurrence of sepsis and in-hospital mortality was lower in HCW (1.7% vs. 3.9%; p = 0.024 and 0.7% vs. 4.8%; p<0.001 respectively). Age, male sex and comorbidity, were independently associated with higher in-hospital mortality and healthcare working with lower mortality (OR 0.211, 95%CI 0.067-0.667, p = 0.008). 30-days survival was higher in HCW (0.968 vs. 0.851 p<0.001). Conclusions Hospitalized COVID-19 HCW had fewer comorbidities and a better prognosis than NHCW. Our results suggest that professional exposure to COVID-19 in HCW does not carry more clinical severity nor mortality

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality