Abstract:

Physiological levels of ROS support neurite outgrowth and axonal specification, but the mechanisms by which ROS are able to shape neurons remain unknown. Ca2 +, a broad intracellular second messenger, promotes both Rac1 activation and neurite extension. Ca2 + release from the endoplasmic reticulum, mediated by both the IP3R1 and ryanodine receptor (RyR) channels, requires physiological ROS levels that are mainly sustained by the NADPH oxidase (NOX) complex. In this work, we explore the contribution of the link between NOX and RyR-mediated Ca2 + release toward axonal specification of rat hippocampal neurons. Using genetic approaches, we find thatNOXactivation promotes both axonal development and Rac1 activation through a RyR-mediated mechanism, which in turn activates NOX through Rac1, one of the NOX subunits. Collectively, these data suggest a feedforward mechanism that integrates both NOX activity and RyR-mediated Ca2 + release to support cellular mechanisms involved in axon development.

Author affiliation: Wilson Rodriguez, Carlos. Universidad de Chile; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina

Author affiliation: Munoz-Palma, Ernesto. Universidad de Chile; Chile

Author affiliation: Henriquez, Daniel R.. Universidad de Chile; Chile

Author affiliation: Palmisano, Ilaria. Imperial College London; Reino Unido

Author affiliation: Nuñez, Marco Tulio. Universidad de Chile; Chile

Author affiliation: Di Giovanni, Simone. Imperial College London; Reino Unido. University of Tuebingen; Alemania

Author affiliation: González Billault, Christian. Universidad de Chile; Chile

Abstract:

Actin and its ability to polymerize into dynamic filaments is critical for the form and function of cells throughout the body. While multiple proteins have been characterized as affecting actin dynamics through noncovalent means, actin and its protein regulators are also susceptible to covalent modifications of their amino acid residues. In this regard, oxidation-reduction (Redox) intermediates have emerged as key modulators of the actin cytoskeleton with multiple different effects on cellular form and function. Here, we review work implicating Redox intermediates in post-translationally altering actin and discuss what is known regarding how these alterations affect the properties of actin. We also focus on two of the best characterized enzymatic sources of these Redox intermediates—the NADPH oxidase NOX and the flavoprotein monooxygenase MICAL—and detail how they have both been identified as altering actin, but share little similarity and employ different means to regulate actin dynamics. Finally, we discuss the role of these enzymes and redox signaling in regulating the actin cytoskeleton in vivo and highlight their importance for neuronal form and function in health and disease. © 2016 Wiley Periodicals, Inc.

Author affiliation: Wilson Rodriguez, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Chile; Chile. Center for Geroscience; Chile

Author affiliation: Terman, Jonathan R.. The University of Texas Southwestern; Estados Unidos

Author affiliation: González Billault, Christian. Universidad de Chile; Chile. Center for Geroscience; Chile. The Buck Institute for Research on Aging; Estados Unidos

Author affiliation: Ahmed, Giasuddin. The University of Texas Southwestern; Estados Unidos

Abstract:

The generation of abnormally high levels of reactive oxygen species (ROS) is linked to cellular dysfunction, including neuronal toxicity and neurodegeneration. However, physiological ROS production modulates redox-sensitive roles of several molecules such as transcription factors, signaling proteins, and cytoskeletal components. Changes in the functions of redox-sensitive proteins may be important for defining key aspects of stem cell proliferation and differentiation, neuronal maturation, and neuronal plasticity. In neurons, most of the studies have been focused on the pathological implications of such modifications and only very recently their essential roles in neuronal development and plasticity has been recognized. In this review, we discuss the participation of NADPH oxidases (NOXs) and a family of protein-methionine sulfoxide oxidases, named molecule interacting with CasLs, as regulated enzymatic sources of ROS production in neurons, and describes the contribution of ROS signaling to neurogenesis and differentiation, neurite outgrowth, and neuronal plasticity.

Author affiliation: Bórquez, Daniel A.. Universidad de Chile; Chile. Universidad Diego Portales; Chile

Author affiliation: Urrutia, Pamela J.. Universidad de Chile; Chile

Author affiliation: Wilson Rodriguez, Carlos. Universidad de Chile; Chile

Author affiliation: Van Zundert, Brigitte. Universidad Andrés Bello; Chile

Author affiliation: Nuñez, Marco Tulio. Universidad de Chile; Chile

Author affiliation: González Billault, Christian. Universidad de Chile; Chile. Center For Geroscience, Brain Health And Metabolism; Chile

Abstract:

Historically, ROS have been considered toxic molecules, especially when their intracellular concentration reaches high values. However, physiological levels of ROS support crucial cellular processes, acting as second messengers able to regulate intrinsic signaling pathways. Specifically, both the central and peripheral nervous systems are especially susceptible to changes in the redox state, developing either a defense or adaptive response depending on the concentration, source and duration of the pro-oxidative stimuli. In this review, we summarize classical and modern concepts regarding ROS physiology, with an emphasis on the role of the NADPH oxidase (NOX) complex, the main enzymatic and regulated source of ROS in the nervous system. We discuss how ROS and redox state contribute to neurogenesis, polarization and maturation of neurons, providing a context for the spatio-temporal conditions in which ROS modulate neural fate, discriminating between “oxidative distress” and “oxidative eustress”. Finally, we present a brief discussion about the “physiological range of ROS concentration” and suggest that these values depend on several parameters, including cell type, developmental stage, and the source and type of pro-oxidative molecule.

Author affiliation: Wilson Rodriguez, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina

Author affiliation: Muñoz Palma, Ernesto. Universidad de Chile; Chile

Author affiliation: González Billault, Christian. Universidad de Chile; Chile. The Buck Institute for Research on Aging; Estados Unidos. Geroscience Center for Brain Health and Metabolism; Chile

Abstract:

Axonal growth cone collapse following spinal cord injury (SCI) is promoted by semaphorin3A (Sema3A) signaling via PlexinA4 surface receptor. This interaction triggers intracellular signaling events leading to increased hydrogen peroxide levels which in turn promote filamentous actin (F-actin) destabilization and subsequent inhibition of axonal re-growth. In the current study, we demonstrated that treatment with galectin-1 (Gal-1), in its dimeric form, promotes a decrease in hydrogen peroxide (H2O2) levels and F-actin repolimerization in the growth cone and in the filopodium of neuron surfaces. This effect was dependent on the carbohydrate recognition activity of Gal-1, as it was prevented using a Gal-1 mutant lacking carbohydrate-binding activity. Furthermore, Gal-1 promoted its own active ligand-mediated endocytosis together with the PlexinA4 receptor, through mechanisms involving complex branched N-glycans. In summary, our results suggest that Gal-1, mainly in its dimeric form, promotes re-activation of actin cytoskeleton dynamics via internalization of the PlexinA4/Gal-1 complex. This mechanism could explain, at least in part, critical events in axonal regeneration including the full axonal re-growth process, de novo formation of synapse clustering, axonal re-myelination and functional recovery of coordinated locomotor activities in an in vivo acute and chronic SCI model.

Author affiliation: Quintá, Héctor Ramiro. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Wilson, Carlos. Universidad de Chile; Chile

Author affiliation: Blidner, Ada Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina

Author affiliation: González Billault, Christian. Universidad de Chile; Chile

Author affiliation: Pasquini, Laura Andrea. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Author affiliation: Rabinovich, Gabriel Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental. Fundación de Instituto de Biología y Medicina Experimental. Instituto de Biología y Medicina Experimental; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Author affiliation: Pasquini, Juana Maria. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Departamento de Química Biológica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentina

Abstract:

Neuronal cells are characterized by the presence of two confined domains, which are different in their cellular properties, biochemical functions and molecular identity. The generation of asymmetric domains in neurons should logically require specialized membrane trafficking to both promote neurite outgrowth and differential distribution of components. Members of the Rab family of small GTPases are key regulators of membrane trafficking involved in transport, tethering and docking of vesicles through their effectors. RabGTPases activity is coupled to the activity of guanine nucleotide exchange factors or GEFs, and GTPase-activating proteins known as GAPs. Since the overall spatiotemporal distribution of GEFs, GAPs and Rabs governs trafficking through the secretory and endocytic pathways, affecting exocytosis, endocytosis and endosome recycling, it is likely that RabGTPases could have a major role in neurite outgrowth, elongation and polarization. In this review we summarize the evidence linking the functions of several RabGTPases to axonal and dendritic development in primary neurons, as well as neurite formation in neuronal cell lines. We focused on the role of RabGTPases from the trans-Golgi network, early/late and recycling endosomes, as well as the function of some Rab effectors in neuritogenesis. Finally, we also discuss the participation of the ADP-ribosylation factor 6, a member of the ArfGTPase family, in neurite formation since it seems to have an important cross-talk with RabGTPases.

Author affiliation: Villarroel Campos, David. Universidad de Chile; Chile

Author affiliation: Gastaldi, Laura Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina

Author affiliation: Conde, Cecilia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina

Author affiliation: Caceres, Alfredo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina

Author affiliation: González Billault, Christian. Universidad de Chile; Chile

Abstract:

Neuronal cells are characterized by the presence of two confined domains, which are different in their cellular properties, biochemical functions and molecular identity. The generation of asymmetric domains in neurons should logically require specialized membrane trafficking to both promote neurite outgrowth and differential distribution of components. Members of the Rab family of small GTPases are key regulators of membrane trafficking involved in transport, tethering and docking of vesicles through their effectors. RabGTPases activity is coupled to the activity of guanine nucleotide exchange factors or GEFs, and GTPase-activating proteins known as GAPs. Since the overall spatiotemporal distribution of GEFs, GAPs and Rabs governs trafficking through the secretory and endocytic pathways, affecting exocytosis, endocytosis and endosome recycling, it is likely that RabGTPases could have a major role in neurite outgrowth, elongation and polarization. In this review we summarize the evidence linking the functions of several RabGTPases to axonal and dendritic development in primary neurons, as well as neurite formation in neuronal cell lines. We focused on the role of RabGTPases from the trans-Golgi network, early/late and recycling endosomes, as well as the function of some Rab effectors in neuritogenesis. Finally, we also discuss the participation of the ADP-ribosylation factor 6, a member of the ArfGTPase family, in neurite formation since it seems to have an important cross-talk with RabGTPases.

Author affiliation: Villaroel Campos, David. Universidad de Chile; Chile

Author affiliation: Gastaldi, Laura Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina

Author affiliation: Conde, Cecilia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina

Author affiliation: Caceres, Alfredo Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra. Universidad Nacional de Córdoba. Instituto de Investigación Médica Mercedes y Martín Ferreyra; Argentina

Author affiliation: González Billault, Christian. Universidad de Chile; Chile