ABSTRACT
Neuroblastoma is a highly metastatic tumor that emerges from neural crest cell progenitors. Focal Adhesion Kinase (FAK) is a regulator of cell migration that binds to the receptor Neogenin-1 and is upregulated in neuroblastoma. Here, we show that Netrin-1 ligand binding to Neogenin-1 leads to FAK autophosphorylation and integrin ß1 activation in a FAK dependent manner, thus promoting neuroblastoma cell migration. Moreover, Neogenin-1, which was detected in all tumor stages and was required for neuroblastoma cell migration, was found in a complex with integrin ß1, FAK, and Netrin-1. Importantly, Neogenin-1 promoted neuroblastoma metastases in an immunodeficient mouse model. Taken together, these data show that Neogenin-1 is a metastasis-promoting protein that associates with FAK, activates integrin ß1 and promotes neuroblastoma cell migration.
Subject(s)
Integrin beta1 , Neuroblastoma , Animals , Cell Adhesion , Cell Movement , Focal Adhesion Kinase 1/genetics , Focal Adhesion Protein-Tyrosine Kinases , Membrane Proteins , Mice , Netrin-1ABSTRACT
Neuroblastoma (NB) is the most common pediatric extracranial solid tumor. It arises during development of the sympathetic nervous system. Netrin-4 (NTN4), a laminin-related protein, has been proposed as a key factor to target NB metastasis, although there is controversy about its function. Here, we show that NTN4 is broadly expressed in tumor, stroma and blood vessels of NB patient samples. Furthermore, NTN4 was shown to act as a cell adhesion molecule required for the migration induced by Neogenin-1 (NEO1) in SK-N-SH neuroblastoma cells. Therefore, we propose that NTN4, by forming a ternary complex with Laminin γ1 (LMγ1) and NEO1, acts as an essential extracellular matrix component, which induces the migration of SK-N-SH cells.
Subject(s)
Cell Movement , Gene Expression Regulation, Neoplastic , Laminin/metabolism , Nerve Tissue Proteins/metabolism , Netrins/metabolism , Neuroblastoma/pathology , Receptors, Cell Surface/metabolism , Cell Adhesion , Female , Humans , Infant , Male , Neuroblastoma/metabolism , Tumor Cells, CulturedABSTRACT
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.
Subject(s)
Nervous System/metabolism , Neurogenesis/physiology , Neurons/metabolism , Reactive Oxygen Species/metabolism , Animals , Humans , Oxidation-Reduction , Signal Transduction/physiologyABSTRACT
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 that NOX activation 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. SIGNIFICANCE STATEMENT: High levels of ROS are frequently associated with oxidative stress and disease. In contrast, physiological levels of ROS, mainly sustained by the NADPH oxidase (NOX) complex, promote neuronal development and axonal growth. However, the mechanisms by which ROS shape neurons have not been described. Our work suggests that NOX-derived ROS promote axonal growth by regulating Rac1 activity, a molecular determinant of axonal growth, through a ryanodine receptor (RyR)-mediated Ca2+ release mechanism. In addition, Rac1, one of the NOX subunits, was activated after RyR-mediated Ca2+ release, suggesting a feedforward mechanism between NOX and RyR. Collectively, our data suggest a novel mechanism that is instrumental in sustaining physiological levels of ROS required for axonal growth of hippocampal neurons.
