Presenilin/γ-Secretase and Inflammation

Presenilins (PS) are the catalytic components of γ-secretase, an aspartyl protease that regulates through proteolytic processing the function of multiple signaling proteins. Specially relevant is the γ-secretase-dependent cleavage of the β-amyloid precursor protein (APP) since generates the β-amyloid (Aβ) peptides that aggregate and accumulate in the brain of Alzheimer's disease (AD) patients. Abnormal processing and/or accumulation of Aβ disrupt synaptic and metabolic processes leading to neuron dysfunction and neurodegeneration. Studies in presenilin conditional knockout mice have revealed that presenilin-1 is essential for age-dependent Aβ accumulation and inflammation. By contrast, mutations in the presenilin genes responsible for early onset familial AD cause rapid disease progression and accentuate clinical and pathological features including inflammation. In addition, a number of loss of function mutations in presenilin-1 have been recently associated to non-Alzheimer's dementias including frontotemporal dementia and dementia with Lewy bodies. In agreement, total loss of presenilin function in the brain results in striking neurodegeneration and inflammation, which includes activation of glial cells and induction of proinflammatory genes, besides altered inflammatory responses in the periphery. Interestingly, some non-steroidal anti-inflammatory drugs that slow cognitive decline and reduce the risk of AD, decrease amyloidogenic Aβ42 levels by modulating allosterically PS/γ-secretase. In this review, I present current evidence supporting a role of presenilin/γ-secretase signaling on gliogenesis and gliosis in normal and pathological conditions. Understanding the cellular mechanisms regulated by presenilin/γ-secretase during chronic inflammatory processes may provide new approaches for the development of effective therapeutic strategies for AD

Conventional and Non-Conventional Roles of Non-Muscle Myosin II-Actin in Neuronal Development and Degeneration

Myosins are motor proteins that use chemical energy to produce mechanical forces driving actin cytoskeletal dynamics. In the brain, the conventional non-muscle myosin II (NMII) regulates actin filament cytoskeletal assembly and contractile forces during structural remodeling of axons and dendrites, contributing to morphology, polarization, and migration of neurons during brain development. NMII isoforms also participate in neurotransmission and synaptic plasticity by driving actin cytoskeletal dynamics during synaptic vesicle release and retrieval, and formation, maturation, and remodeling of dendritic spines. NMIIs are expressed differentially in cerebral non-neuronal cells, such as microglia, astrocytes, and endothelial cells, wherein they play key functions in inflammation, myelination, and repair. Besides major efforts to understand the physiological functions and regulatory mechanisms of NMIIs in the nervous system, their contributions to brain pathologies are still largely unclear. Nonetheless, genetic mutations or deregulation of NMII and its regulatory effectors are linked to autism, schizophrenia, intellectual disability, and neurodegeneration, indicating non-conventional roles of NMIIs in cellular mechanisms underlying neurodevelopmental and neurodegenerative disorders. Here, we summarize the emerging biological roles of NMIIs in the brain, and discuss how actomyosin signaling contributes to dysfunction of neurons and glial cells in the context ofneurological disorders. This knowledge is relevant for a deep understanding of NMIIs on the pathogenesis and therapeutics of neuropsychiatric and neurodegenerative diseases

Interacción funcional entre la adenosina desaminasa y el receptor A1 de adenosina en la superficie celular

[spa] La adenosina deaminasa (ADA) es una enzima del metabolismo purínico que ha sido hallada tanto en el citosol como en la superficie celular. En este estudio se ha demostrado que la ADA interacciona con los receptores A1 de adenosina (A1Rs) en corteza cerebral de cerdo y en la línea celular DDT1MF-2. A través de esta interacción la ADA aumenta la afinidad del receptor A1 por los ligandos agonistas, permite la aparición del estado de alta afinidad del receptor (receptor-proteína G) y es necesaria para la correcta transducción de la señal del receptor A1. Los mecanismos moleculares involucrados en la desensibilización homóloga de los A1Rs se estudiaron en células DDT1MF-2. La exposición crónica de las células con el agonista R- PIA produce una rápida desensibilización funcional, la fosforilación y la agregación en la superficie celular de los receptores A1. La internalización de los A1Rs hacia compartimentos intracelulares es un proceso lento (horas) y conduce a la “down-regulation” de éstos. El antagonista, por el contrario, induce la aparición de nuevos centros de unión en la membrana. Todos los procesos implicados en la desensibilización homóloga del receptor A1 son acelerados y aumentados por la ADA. El agonista induce también la internalización conjunta de la ADA y los A1Rs. Estos resultados muestran una regulación mutua y una vía de endocitosis común de la ADA y el A1R de adenosina durante el proceso de desensibilización. Este es el primer estudio donde se demuestra que un miembro de la familia de receptores acoplados a proteína G requiere una ectoenzima, cuyo sustrato es el ligando del receptor, para una eficiente señalización y regulación funcional

Gene expression parallels synaptic excitability and plasticity changes in Alzheimer's disease

Altres ajuts: CIBERNED CB06/05/0042 i BrightFocus Foundation (A2014417S)Alzheimer's disease (AD) is a neurodegenerative disorder characterized by abnormal accumulation of β-amyloid and tau and synapse dysfunction in memory-related neural circuits. Pathological and functional changes in the medial temporal lobe, a region essential for explicit memory encoding, contribute to cognitive decline in AD. Surprisingly, functional imaging studies show increased activity of the hippocampus and associated cortical regions during memory tasks in presymptomatic and early AD stages, whereas brain activity declines as the disease progresses. These findings suggest an emerging scenario where early pathogenic events might increase neuronal excitability leading to enhanced brain activity before clinical manifestations of the disease, a stage that is followed by decreased brain activity as neurodegeneration progresses. The mechanisms linking pathology with synaptic excitability and plasticity changes leading to memory loss in AD remain largely unclear. Recent studies suggest that increased brain activity parallels enhanced expression of genes involved in synaptic transmission and plasticity in preclinical stages, whereas expression of synaptic and activity-dependent genes are reduced by the onset of pathological and cognitive symptoms. Here, we review recent evidences indicating a relationship between transcriptional deregulation of synaptic genes and neuronal activity and memory loss in AD and mouse models. These findings provide the basis for potential clinical applications of memory-related transcriptional programs and their regulatory mechanisms as novel biomarkers and therapeutic targets to restore brain function in AD and other cognitive disorders

Revealing cell vulnerability in Alzheimer's disease by single-cell transcriptomics

Acord transformatiu CRUE-CSICAlzheimer's disease (AD) is a neurodegenerative disorder that by affecting specific brain cell types and regions cause severe pathological and functional changes in memory neural circuits. A comprehensive knowledge of the pathogenic mechanisms underlying AD requires a deeper understanding of the cell-specific pathological responses through integrative molecular analyses. Recent application of high-throughput single-cell transcriptomics to postmortem tissue has proved powerful to unravel cell susceptibility and biological networks responding to amyloid and tau pathologies. Here, we review single-cell transcriptomic studies successfully applied to decipher cell-specific gene expression programs and pathways in the brain of AD patients. Transcriptional information reveals both specific and common gene signatures affecting the major cerebral cell types, including astrocytes, endothelial cells, microglia, neurons, and oligodendrocytes. Cell type-specific transcriptomes associated with AD pathology and clinical symptoms are related to common biological networks affecting, among others pathways, synaptic function, inflammation, proteostasis, cell death, oxidative stress, and myelination. The general picture that emerges from systems-level single-cell transcriptomics is a spatiotemporal pattern of cell diversity and biological pathways, and novel cell subpopulations affected in AD brain. We argue that broader implementation of cell transcriptomics in larger AD human cohorts using standardized protocols is fundamental for reliable assessment of temporal and regional cell-type gene profiling. The possibility of applying this methodology for personalized medicine in clinics is still challenging but opens new roads for future diagnosis and treatment in dementia

Vies de senyalització regulades per les Presenilines en càncer de pell : paper del receptor d'EGF /

Als preliminars: Projecte subvencionat per la Fundació Marató de TV3 (Nº ID: 050710; Regulació de les vies de transducció de senyals depenents de les presenilines en el càncer de pell)...Consultable des del TDXTítol obtingut de la portada digitalitzadaMutacions autosòmiques dominants en els gens de presenilines (PS) són la principal causa d'Alzheimer familiar hereditari. Aquestes mutacions alteren el metabolisme de l'APP i la generació del pèptid -amiloide, el qual s'acumula en forma de plaques en el cervell dels malalts d'Alzheimer. Les PS són les unitats catalítiques del complex enzimàtic -secretasa, responsable de la proteòlisi de proteïnes tipus I, entre elles l'APP i Notch. A més del seu important paper en la patologia de la malaltia d'Alzheimer, les PS regulen processos de proliferació ja que la seva inactivació produeix tumors epitelials en ratolins a través de mecanismes moleculars poc coneguts. Degut a l'important paper del receptor d'EGF (EGFR) en processos oncogènics, varem hipotetitzar que les PS podien alterar la transformació cel·lular en part mitjançant la regulació de la via de senyalització de l'EGFR. Els resultats obtinguts indiquen que la inactivació de les PS en fibroblasts causa transformació cel·lular que és específicament bloquejada amb un inhibidor de l'EGFR. Observarem un increment en l'expressió i senyalització de l'EGFR degut a un retard en la degradació a causa d'alteracions en els processos d'ubiquitinització/deubiquitinització d'aquest receptor. La regulació de PS sobre EGFR depèn de l'activitat de la E3 ubiquitina lligasa Fbw7. En aquest treball hem descrit per primera vegada que la pèrdua de funció de PS ocasiona un excés en la transcripció gènica de Fbw7, el qual regula positivament els nivells d'EGFR. Aquests resultats són innovadors ja que, tot i que Fbw7 actua com gen supressor de tumors en altres teixits, en aquest cas està promovent transformació cel·lular sent la primera vegada que es descriu un increment en els nivells de Fbw7 en un procés tumoral epitelial. Aquests resultats són corroborats en un model de ratolí induïble amb deficiència específica d'ambdues PS en pell (ePS cDKO), que ha estat generat en el desenvolupament d'aquest treball. Els ratolins ePS cDKO desenvolupen espontàniament tumors escatosos (SCC) a la pell del coll i presenten susceptibilitat a desenvolupar tumors en front a l'exposició a agents citotòxics. En aquesta tesi doctoral s'ha descrit que la pèrdua de funció de PS en pell té greus conseqüències en l'homeòstasi epitelial ja que l'absència de PS produeix el desenvolupament de SCC que porta a la mort dels animals a una edat màxima de 2.5-3 mesos d'edat. Aquest fenotip és degut a la desregulació de la via de senyalització de Notch, -catenina i EGFR, tenint aquest últim un paper cabdal segons els resultats obtinguts en aquest treball. El paper central de PS en la regulació de les diferents vies de senyalització esmentades suggereix que PS és un important gen supressor de tumors.Dominant autosomic mutations of presenilin (PS) genes are the most important cause of familiar Alzheimer disease. These mutations modify APP metabolism and -amiloid peptide generation, which is accumulated forming plaques on the brain of Alzheimer disease patients. Presenilins are the catalytic unit of -secretase enzymatic complex, responsible of proteins type I proteolysis, such as APP and Notch. Besides their important role on Alzheimer disease, PS regulate proliferation processes since its inactivation on mice leads to development of epithelial tumor through poor understood molecular mechanisms. Due to the important role of EGF receptor (EGFR) on tumoral processes we hypothesized that presenilin could be involved on cellular transformation in part by regulating EGFR signaling pathway. Results obtained in this work indicate that inactivation of PS in fibroblasts cause cellular transformation that is specifically blocked by using an EGFR inhibitor. We observed an increase of EGFR expression and signaling due to a delayed degradation caused by an alteration of ubiquitination and de-ubiquitination processes. Regulation of EGFR by PS is depending of E3 ubiquitin ligase Fbw7 activity. This work describes for first time that lost of PS function leads to increased transcription of Fbw7, which positively regulates EGFR levels. These results are pioneering since, whereas Fbw7 is a tumor suppressor gene in other tissues, in skin it promotes cellular transformation being the first time that is described an increase of Fbw7 levels in skin tumor. These results are corroborated in a mice model inducible and conditional with PS deletion in skin (ePS cDKO), which has been generated during the development of this study. ePS cDKO mice develop spontaneously squamous cell carcinoma (SCC) in neck skin area and show increased tumor susceptibility in front of cytotoxic agents. This thesis has described that lost of PS function in skin has drastic consequences on epithelial homeostasis since PS deficiency leads to development of SCC and causes death of animals at 2.5-3 moths of age. This phenotype is due to a deregulation of Notch, -catenin and EGFR signaling pathways, where the last one has the most important role in accordance to the results obtained in this study. Key role of PS in regulation of several pathways suggest PS as an important tumor suppressor gene

Spatial Memory Training Counteracts Hippocampal GIRK Channel Decrease in the Transgenic APPSw,Ind J9 Alzheimer's Disease Mouse Model

This work was supported by grants BFU2017-82494-P, PID2020-115823-GB100 funded by MCIN/AEI/10.13039/501100011033, and SBPLY/21/180501/000150 funded by JCCM and ERDF A way of making Europe, to LJD and JDNL; and grant PID2019-106615RB-I00 and Instituto de Salud Carlos III (CIBERNED CB06/05/0042) to CAS. AC held a Margarita Salas Postdoctoral Research Fellow funded by European Union NextGenerationEU/PRTR.G-protein-gated inwardly rectifying potassium (GIRK) channels are critical determinants of neuronal excitability. They have been proposed as potential targets to restore excitatory/inhibitory balance in acute amyloidosis models, where hyperexcitability is a hallmark. However, the role of GIRK signaling in transgenic mice models of Alzheimer's disease (AD) is largely unknown. Here, we study whether progressive amyloid-β (Aβ) accumulation in the hippocampus during aging alters GIRK channel expression in mutant β-amyloid precursor protein (APP J9) transgenic AD mice. Additionally, we examine the impact of spatial memory training in a hippocampal-dependent task, on protein expression of GIRK subunits and Regulator of G-protein signaling 7 (RGS7) in the hippocampus of APP J9 mice. Firstly, we found a reduction in GIRK2 expression (the main neuronal GIRK channels subunit) in the hippocampus of 6-month-old APP J9 mice. Moreover, we found an aging effect on GIRK2 and GIRK3 subunits in both wild type (WT) and APP J9 mice. Finally, when 6-month-old animals were challenged to a spatial memory training, GIRK2 expression in the APP J9 mice were normalized to WT levels. Together, our results support the evidence that GIRK2 could account for the excitatory/inhibitory neurotransmission imbalance found in AD models, and training in a cognitive hippocampal dependent task may have therapeutic benefits of reversing this effect and lessen early AD deficits

Adenosine A2A receptor antagonists affects NMDA glutamate receptor function. Potential to address neurodegeneration in Alzheimer's disease

(1) Background. N-methyl d-aspartate (NMDA) ionotropic glutamate receptor (NMDAR), which is one of the main targets to combat Alzheimer's disease (AD), is expressed in both neurons and glial cells. The aim of this paper was to assess whether the adenosine A2A receptor (A2AR), which is a target in neurodegeneration, may affect NMDAR functionality. (2) Methods. Immuno-histo/cytochemical, biophysical, biochemical and signaling assays were performed in a heterologous cell expression system and in primary cultures of neurons and microglia (resting and activated) from control and the APPSw,Ind transgenic mice. (3) Results. On the one hand, NMDA and A2A receptors were able to physically interact forming complexes, mainly in microglia. Furthermore, the amount of complexes was markedly enhanced in activated microglia. On the other hand, the interaction resulted in a novel functional entity that displayed a cross-antagonism, that could be useful to prevent the exacerbation of NMDAR function by using A2AR antagonists. Interestingly, the amount of complexes was markedly higher in the hippocampal cells from the APPSw,Ind than from the control mice. In neurons, the number of complexes was lesser, probably due to NMDAR not interacting with the A2AR. However, the activation of the A2AR receptors resulted in higher NMDAR functionality in neurons, probably by indirect mechanisms. (4) Conclusions. A2AR antagonists such as istradefylline, which is already approved for Parkinson's disease (Nouriast® in Japan and Nourianz® in the US), have potential to afford neuroprotection in AD in a synergistic-like fashion. i.e., via both neurons and microglia

Crtc1 activates a transcriptional program deregulated at early Alzheimer's disease-related stages

Cognitive decline is associated with gene expression changes in the brain, but the transcriptional mechanisms underlying memory impairments in cognitive disorders, such as Alzheimer's disease (AD), are largely unknown. Here, we aimed to elucidate relevant mechanisms responsible for transcriptional changes underlying early memory loss in AD by examining pathological, behavioral, and transcriptomic changes in control and mutant β-amyloid precursor protein (APPSw,Ind) transgenic mice during aging. Genome-wide transcriptome analysis using mouse microarrays revealed deregulation of a gene network related with neurotransmission, synaptic plasticity, and learning/memory in the hippocampus of APPSw,Ind mice after spatial memory training. Specifically, APPSw,Ind mice show changes on a cAMP-responsive element binding protein (CREB)-regulated transcriptional program dependent on the CREB-regulated transcription coactivator-1 (Crtc1). Interestingly, synaptic activity and spatial memory induces Crtc1 dephosphorylation (Ser151), nuclear translocation, and Crtc1-dependent transcription in the hippocampus, and these events are impaired in APPSw,Ind mice at early pathological and cognitive decline stages. CRTC1-dependent genes and CRTC1 levels are reduced in human hippocampus at intermediate Braak III/IV pathological stages. Importantly, adeno-associated viral-mediated Crtc1 overexpression in the hippocampus efficiently reverses Aβ-induced spatial learning and memory deficits by restoring a specific subset of Crtc1 target genes. Our results reveal a critical role of Crtc1-dependent transcription on spatial memory formation and provide the first evidence that targeting brain transcriptome reverses memory loss in AD

La Directiva Europea sobre el Horario de Trabajo y su impacto sobre la formación quirúrgica. Resultados de una encuesta entre los residentes de Cirugía Cardiovascular en España

ObjetivosLa Directiva Europea del Horario de Trabajo (European Working time Directive [EWTD]) de 1993 debería estar en funcionamiento para cirujanos cardiovasculares y residentes en agosto de 2009, como respuesta a las dudas sobre la calidad del cuidado del paciente y la calidad de vida de los profesionales causadas por el trabajo excesivo y la fatiga laboral. Hay temor al impacto negativo de la fatiga en la calidad de la atención al paciente y de las residencias quirúrgicas, en especial en Cirugía Cardiovascular. Evaluamos el nivel de conocimiento de los residentes españoles sobre la EWTD.MétodosEncuesta individual a los residentes asistentes al XIII Curso de Residentes de la Sociedad Española de Cirugía Torácica y Cardiovascular de mayo de 2008. Incluye un resumen de los objetivos principales de la EWTD.ResultadosAsistieron 58 de 70 residentes posibles. La encuesta fue completada por 26. El 92,3% no había leído la EWTD y el 26,9% no tenía el mínimo conocimiento. El 54,2% estaba de acuerdo con su contenido; 53,8% la considera incompatible con su modelo ideal de formación; 68% cree que tendrá impacto negativo en la misma; 87% cree que discrimina a los residentes quirúrgicos; 65,2% cree que reducirá sus ingresos anuales; 84,6% cree que parte de la plantilla de sus servicios se opondrá.ConclusionesExiste un desconocimiento muy importante sobre la EWTD por los residentes españoles de Cirugía Cardiovascular. Sorprendentemente, la mayoría está de acuerdo con la EWTD a pesar de que pueda tener impacto negativo en su formación y retribución económica. Se requiere una profunda reflexión por parte de las sociedades profesionales sobre este tema para promover y proteger la formación en nuestra especialidad.ObjectivesThe 1993 European Working Time Directive (EWTD) should be implemented to its entirety for cardiovascular surgeons and residents by August 2009 as an answer to the concern about patient care and quality of life of professionals caused by fatigue and excessive continuous work. Great concern rose regarding its negative impact in the quality of surgical residencies, specifically in cardiovascular surgery. Our objective was to assess the knowledge of Spanish Cardiovascular Surgery residents on the EWTD and their level of agreement with its content.MethodsA survey questionnaire was given to all residents attending the XIII Annual Course organized by the Spanish Society of Thoracic-Cardiovascular Surgery in May 2008. It included a brief summary of the key features of the EWTD.ResultsOut of 70 eligible residents, 58 attended. Of these, 26 completed and returned the survey. 92,3% never read and 26,9% knew absolutely nothing about the EWTD. 54,2% agreedwith its content; 53,8% think it is not compatible with their ideal training model; 68% believe it will have a negative impact on their training; 87% think it negatively discriminates surgical residents; 65,2% believe it will decrease their annual stipends; 84,6% think it will find the opposition of part of the staff in their respective departments.ConclusionsKnowledge about the contents of the EWTD among Spanish Cardiovascular Surgery residents is scarce. The majority of them agree with the EWTD even realizing it may have a negative impact on training quality and economic retribution. A deep reflection on this by national and European societies to protect and promote the quality of the training in our specialty is required