CXCR4/CXCR7 molecular involvement in neuronal and neural progenitor migration: Focus in CNS repair

© 2014 Wiley Periodicals, Inc.In the adult brain, neural progenitor cells (NPCs) reside in the subventricular zone (SVZ) of the lateral ventricles, the dentate gyrus and the olfactory bulb. Following CNS insult, NPCs from the SVZ can migrate along the rostral migratory stream (RMS), a migration of NPCs that is directed by proinflammatory cytokines. Cells expressing CXCR4 follow a homing signal that ultimately leads to neuronal integration and CNS repair, although such molecules can also promote NPC quiescence. The ligand, SDF1 alpha (or CXCL12) is one of the chemokines secreted at sites of injury that it is known to attract NSC-derived neuroblasts, cells that express CXCR4. In function of its concentration, CXCL12 can induce different responses, promoting NPC migration at low concentrations while favoring cell adhesion via EGF and the alpha 6 integrin at high CXCL12 concentrations. However, the preclinical effectiveness of chemokines and their relationship with NPC mobilization requires further study, particularly with respect to CNS repair. NPC migration may also be affected by the release of cytokines or chemokines induced by local inflammation, through autocrine or paracrine mechanisms, as well as through erythropoietin (EPO) or nitric oxide (NO) release. CXCL12 activity requires G-coupled proteins and the availability of its ligand may be modulated by its binding to CXCR7, for which it shows a stronger affinity than for CXCR4Comision Interministerial de Ciencia y Tecnologíä (Grant SAF 2012-3127) and the “Ramon y Cajal” programme (RyC 2008-0258 to JJM and RyC 2010-06251 to B.C). We also thank Fundación Ramón Areces for its institutional support of the “Centro de Biología Molecular Severo Ochoa”.Peer Reviewe

Hipótesis glutamatérgica de la esquizofrenia: mecanismos moleculares del transporte de glicina en las sinapsis glutamatérgicas

During the last few years, evidence has been obtained for a relationship between hypofunction of the NMDA type of glutamate receptor and schizophrenia. The glycine binding site on NMDAR and the glycine transporter GLYT1 represent some of the most promising therapeutic targets for developing new anti-schizophrenic drugs. Pharmacological inhibition of GLYT1 increases glycine levels in the surrounding of NMDAR and stimulates its function. Previous studies performed indicated that GLYT1 is physically associated with NMDAR, through the scaffolding protein PSD-95, due to the common interaction of both GLYT1 and NMDAR with PDZ domains of PSD-95. The objective of this research was centred on the study of the interaction of GLYT1 with other PDZ proteins, in special those that also interact with NMDAR. Particularly, we were interested the heteromeric tricomplex Mint-MALS-CASK. We analyzed the structural basis of these interactions and the functional consequence on GLYT1 in aspects such as the intracellular traffic, the turnover on the cell surface and the inclusion in specific microdomains of the membrane. In this way we analyzed the possible existence of common steps in GLYT1 and NMDAR processing. To do that we used molecular and cellular biology techniques, such as cotransfections in cellular systems of DNA constructs obtained by site directed mutagenesis and immunoprecipitations.Durante los últimos años, se han obtenido evidencias que relacionan la hipofunción del receptor de glutamato tipo NMDA (NMDAR) con la esquizofrenia. Los receptores NMDA necesitan para su estimulación la unión conjunta tanto de glutamato como de glicina, ya que ambos poseen en el receptor un sitio de unión específico. Puesto que la inhibición farmacológica de GLYT1 aumenta los niveles de glicina en los alrededores del receptor de glutamato tipo NMDA estimulando su función, el transportador de glicina GLYT1 representa una de las dianas terapéuticas más prometedoras para el desarrollo de nuevos fármacos antipsicóticos. Previamente hemos demostrado que GLYT1 se encuentra físicamente asociado con NMDAR a través de la proteína de adaptadora PSD-95 en neuronas glutamatérgicas. El objetivo de este trabajo se centra en el estudio de la interacción de GLYT1 con otras proteínas, especialmente con aquellas que también interaccionan con el receptor de glutamato tipo NMDA. Hemos encontrado que GLYT1 interacciona con el tricomplejo heterotrimérico Mint-MALS-CASK. Este complejo está implicado en el transporte polarizado del receptor del glutamato tipo NMDA al terminal postsináptico. Puesto que GLYT1 interacciona simultáneamente con NMDAR y con el complejo Mint-MALS-CASK, proponemos que NMDAR y GLYT1 son cotransportados al terminal sináptico, así en todo momento NMDAR puede ser regulado por GLYT1. Estos resultados refuerzan la importancia de GLYT1 en la regulación de NMDAR y su potencial como blanco de acción de fármacos antipsicóticos

R-ras1 and r-ras2 are essential for oligodendrocyte differentiation and survival for correct myelination in the central nervous system

Rapid and effective neural transmission of information requires correct axonal myelination. Modifications in myelination alter axonal capacity to transmit electric impulses and enable pathological conditions. In the CNS, oligodendrocytes (OLs) myelinate axons, a complex process involving various cellular interactions. However, we know little about the mechanisms that orchestrate correct myelination. Here, we demonstrate that OLs express R-Ras1 and R-Ras2. Using female and male mutant mice to delete these proteins, we found that activation of the PI3K/Akt and Erk1/2-MAPK pathways was weaker in mice lacking one or both of these GTPases, suggesting that both proteins coordinate the activity of these two pathways. Loss of R-Ras1 and/or R-Ras2 diminishes the number of OLs in major myelinated CNS tracts and increases the proportion of immature OLs. In R-Ras1-/-and R-Ras2-/--null mice, OLs show aberrant morphologies and fail to differentiate correctly into myelin-forming phenotypes. The smaller OL population and abnormal OL maturation induce severe hypomyelination, with shorter nodes of Ranvier in R-Ras1-/-and/or R-Ras2-/-mice. These defects explain the slower conduction velocity of myelinated axons that we observed in the absence of R-Ras1 and R-Ras2. Together, these results suggest that R-Ras1 and R-Ras2 are upstream elements that regulate the survival and differentiation of progenitors into OLs through the PI3K/Akt and Erk1/2-MAPK pathways for proper myelination.This work was supported by the Spanish Ministry of Economy and Competitiveness (BFU2015-64829-S and SAF2012-31279) to B.C. and (SAF2015-70368-R) to F.W

R-RAS2 overexpression in tumors of the human central nervous system

Malignant tumors of the central nervous system (CNS) are the 10th most frequent cause of cancer mortality. Despite the strong malignancy of some such tumors, oncogenic mutations are rarely found in classic members of the RAS family of small GTPases. This raises the question as to whether other RAS family members may be affected in CNS tumors, excessively activating RAS pathways. The RAS-related subfamily of GTPases is that which is most closely related to classical Ras and it currently contains 3 members: RRAS, RRAS2 and RRAS3. While R-RAS and R-RAS2 are expressed ubiquitously, R-RAS3 expression is restricted to the CNS. Significantly, both wild type and mutated RRAS2 (also known as TC21) are overexpressed in human carcinomas of the oral cavity, esophagus, stomach, skin and breast, as well as in lymphomas. Hence, we analyzed the expression of R-RAS2 mRNA and protein in a wide variety of human CNS tumors and we found the R-RAS2 protein to be overexpressed in all of the 90 CNS cancer samples studied, including glioblastomas, astrocytomas and oligodendrogliomas. However, R-Ras2 was more strongly expressed in low grade (World Health Organization grades I-II) rather than high grade (grades III-IV) tumors, suggesting that R-RAS2 is overexpressed in the early stages of malignancy. Indeed, R-RAS2 overexpression was evident in pre-malignant hyperplasias, both at the mRNA and protein levels. Nevertheless, such dramatic changes in expression were not evident for the other two subfamily members, which implies that RRAS2 is the main factor triggering neural transformation.This work was supported by grants SAF2012-31279 from the ‘Comisión Interministerial de Ciencia y Tecnología’ and the ‘Ramón y Cajal’ program (RYC-2010-06251, to B.C.). We also thank the Fundación Ramón Areces for its institutional support of the ‘Centro de Biología Molecular Severo Ochoa’

Absence of R-Ras1 and R-Ras2 causes mitochondrial alterations that trigger axonal degeneration in a hypomyelinating disease model

Fast synaptic transmission in vertebrates is critically dependent on myelin for insulation and metabolic support. Myelin is produced by oligodendrocytes (OLs) that maintain multilayered membrane compartments that wrap around axonal fibers. Alterations in myelination can therefore lead to severe pathologies such as multiple sclerosis. Given that hypomyelination disorders have complex etiologies, reproducing clinical symptoms of myelin diseases from a neurological perspective in animal models has been difficult. We recently reported that R-Ras1 and/or R-Ras2 mice, which lack GTPases essential for OL survival and differentiation processes, present different degrees of hypomyelination in the central nervous system with a compounded hypomyelination in double knockout (DKO) mice. Here, we discovered that the loss of R-Ras1 and/or R-Ras2 function is associated with aberrant myelinated axons with increased numbers of mitochondria, and a disrupted mitochondrial respiration that leads to increased reactive oxygen species levels. Consequently, aberrant myelinated axons are thinner with cytoskeletal phosphorylation patterns typical of axonal degeneration processes, characteristic of myelin diseases. Although we observed different levels of hypomyelination in a single mutant mouse, the combined loss of function in DKO mice lead to a compromised axonal integrity, triggering the loss of visual function. Our findings demonstrate that the loss of R-Ras function reproduces several characteristics of hypomyelinating diseases, and we therefore propose that R-Ras1 and R-Ras2 neurological models are valuable approaches for the study of these myelin pathologies.Spanish Ministry of Economy and Competitiveness (RTI2018-096303B-C33) to B. C., (RTI2018-096303B-C31) to F. W., and RTI2018-095166B-I00 to C. G. R. and P. L. and Instituto de Salud Carlos III and co-funded by the European Regional Development Fund (ERDF) within the “Plan Estatal de Investigación Científica y Técnica y de Innovación 2017–2020” (RD16/0008/0020; FIS/PI 18-00754

Localización del transportador de Glicina GLYT1 en sinapsis glutamatérgicas y caracterización de su interacción con proteínas con dominios PDZ

Tesis Doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Biología Molecular. Fecha de lectura: 12-05-200

R-Ras GTPases Signaling Role in Myelin Neurodegenerative Diseases

© 2020 by the authors.Myelination is required for fast and efficient synaptic transmission in vertebrates. In the central nervous system, oligodendrocytes are responsible for creating myelin sheaths that isolate and protect axons, even throughout adulthood. However, when myelin is lost, the failure of remyelination mechanisms can cause neurodegenerative myelin-associated pathologies. From oligodendrocyte progenitor cells to mature myelinating oligodendrocytes, myelination is a highly complex process that involves many elements of cellular signaling, yet many of the mechanisms that coordinate it, remain unknown. In this review, we will focus on the three major pathways involved in myelination (PI3K/Akt/mTOR, ERK1/2-MAPK, and Wnt/β-catenin) and recent advances describing the crosstalk elements which help to regulate them. In addition, we will review the tight relation between Ras GTPases and myelination processes and discuss its potential as novel elements of crosstalk between the pathways. A better understanding of the crosstalk elements orchestrating myelination mechanisms is essential to identify new potential targets to mitigate neurodegeneration.This work was supported by the Spanish Ministry of Economy and Competitiveness, Grant: RTI2018-096303B-C33.Peer reviewe

Enrichment of Conserved Synaptic Activity-Responsive Element in Neuronal Genes Predicts a Coordinated Response of MEF2, CREB and SRF

A unique synaptic activity-responsive element (SARE) sequence, composed of the consensus binding sites for SRF, MEF2 and CREB, is necessary for control of transcriptional upregulation of the Arc gene in response to synaptic activity. We hypothesize that this sequence is a broad mechanism that regulates gene expression in response to synaptic activation and during plasticity; and that analysis of SARE-containing genes could identify molecular mechanisms involved in brain disorders. To search for conserved SARE sequences in the mammalian genome, we used the SynoR in silico tool, and found the SARE cluster predominantly in the regulatory regions of genes expressed specifically in the nervous system; most were related to neural development and homeostatic maintenance. Two of these SARE sequences were tested in luciferase assays and proved to promote transcription in response to neuronal activation. Supporting the predictive capacity of our candidate list, up-regulation of several SARE containing genes in response to neuronal activity was validated using external data and also experimentally using primary cortical neurons and quantitative real time RT-PCR. The list of SARE-containing genes includes several linked to mental retardation and cognitive disorders, and is significantly enriched in genes that encode mRNA targeted by FMRP (fragile X mental retardation protein). Our study thus supports the idea that SARE sequences are relevant transcriptional regulatory elements that participate in plasticity. In addition, it offers a comprehensive view of how activity-responsive transcription factors coordinate their actions and increase the selectivity of their targets. Our data suggest that analysis of SARE-containing genes will reveal yet-undescribed pathways of synaptic plasticity and additional candidate genes disrupted in mental disease.This work was funded by the Ministerio de Ciencia e Innovacion (MICINN) grants (SAF2008-00211; PIE- 200820I166), and a grant from the Spanish Comunidad de Madrid CCG08-CSIC/SAL-3464.Peer Reviewe

Mamífero no humano modificado genéticamente, células y métodos para producirlas

Mamífero no humano modificado genéticamente, células y métodos para producirlas. La presente invención se encuentra dentro del campo de la biología molecular y la biotecnología, y se refiere a un mamífero no humano modificado genéticamente cuyas células comprenden una secuencia nucleotídica inactivada funcionalmente o que ha sido suprimida total o parcialmente, donde dicha secuencia corresponde a un gen que codifica para la proteína TC21 (RRas2 o R-Ras2). Asimismo, la invención también se refiere a una célula aislada, procedente de un mamífero, modificada genéticamente para que presente la modificación genética descrita, así como a los métodos para producir tanto los animales como las células modificadas genéticamente y al uso de dichas células y métodos que las comprenden para el cribado y selección de compuestos con capacidad moduladora de la supervivencia y homeostasis de las células B y T. Por otra parte, la presente invención se refiere a una secuencia nucleotídica capaz de generar un siRNA para la silenciación post-transcripcional del producto de expresión de la citada proteína TC21.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universidad de SalamancaA1 Solicitud de patentes con informe sobre el estado de la técnic