- Targeted disruption of the orphan receptor Gpr151 does not alter pain-related behaviour despite a strong induction in dorsal root ganglion expression in a model of neuropathic pain. [Journal Article]
- MCMol Cell Neurosci 2016 Nov 29
- CONCLUSIONS: Our results indicate that despite the very large upregulation in the DRG after a nerve injury model of neuropathic pain, the Gpr151 orphan receptor does not appear to be involved in the modulation of pain-related behaviours. Further, galanin is unlikely to be an endogenous ligand for Gpr151.
- Sequence determinants of the Caenhorhabditis elegansdopamine transporter dictating in vivoaxonal export and synaptic localization. [Journal Article]
- MCMol Cell Neurosci 2016 Nov 29
- The monoamine neurotransmitter dopamine (DA) acts across phylogeny to modulate both simple and complex behaviors. The presynaptic DA transporter (DAT) is a major determinant of DA signaling capacity ...
The monoamine neurotransmitter dopamine (DA) acts across phylogeny to modulate both simple and complex behaviors. The presynaptic DA transporter (DAT) is a major determinant of DA signaling capacity in ensuring efficient extracellular DA clearance. In humans, DAT is also a major target for prescribed and abused psychostimulants. Multiple structural determinants of DAT function and regulation have been defined, though largely these findings have arisen from heterologous expression or ex vivo cell culture studies. Loss of function mutations in the gene encoding the Caenhorhabditis elegans DAT (dat-1) produces rapid immobility when animals are placed in water, a phenotype termed swimming-induced paralysis (Swip). The ability of a DA neuron-expressed, GFP-tagged DAT-1 fusion protein (GFP::DAT-1) to localize to synapses and rescue Swip in these animals provides a facile approach to define sequences supporting DAT somatic export and function in vivo. In prior studies, we found that truncation of the last 25 amino acids of the DAT-1 C-terminus (Δ25) precludes Swip rescue, supported by a deficit in GFP::DAT-1 synaptic localization. Here, we further defined the elements within Δ25 required for DAT-1 export and function in vivo. We identified two conserved motifs ((584)KW(585) and (591)PYRKR(595)) where mutation results in a failure of GFP::DAT-1 to be efficiently exported to synapses and restore DAT-1 function. The (584)KW(585) motif conforms to a sequence proposed to support SEC24 binding, ER export from the endoplasmic reticulum (ER), and surface expression of mammalian DAT proteins, whereas the (591)PYRKR(595) sequence conforms to a 3R motif identified as a SEC24 binding site in vertebrate G-protein coupled receptors. Consistent with a potential role of SEC24 orthologs in DAT-1 export, we demonstrated DA neuron-specific expression of a sec-24.2 transcriptional reporter. Mutations of the orthologous C-terminal sequences in human DAT (hDAT) significantly reduced transporter surface expression and DA uptake, despite normal hDAT protein expression. Although, hDAT mutants retained SEC24 interactions, as defined in co-immunoprecipitation studies. However, these mutations disrupted the ability of SEC24D to enhance hDAT surface expression. Our studies document an essential role of conserved DAT C-terminal sequences in transporter somatic export and synaptic localization in vivo, that add further support for important roles for SEC24 family members in efficient transporter trafficking.
- Cell-cell communication mediated by the CAR subgroup of immunoglobulin cell adhesion molecules in health and disease. [Review]
- MCMol Cell Neurosci 2016 Nov 18
- The immunoglobulin superfamily represents a diverse set of cell-cell contact proteins and includes well-studied members such as NCAM1, DSCAM, L1 or the contactins which are strongly expressed in the ...
The immunoglobulin superfamily represents a diverse set of cell-cell contact proteins and includes well-studied members such as NCAM1, DSCAM, L1 or the contactins which are strongly expressed in the nervous system. In this review we put our focus on the biological function of a less understood subgroup of Ig-like proteins composed of CAR (coxsackievirus and adenovirus receptor), CLMP (CAR-like membrane protein) and BT-IgSF (brain and testis specific immunoglobulin superfamily). The CAR-related proteins are type I transmembrane proteins containing an N-terminal variable (V-type) and a membrane proximal constant (C2-type) Ig domain in their extracellular region which are implicated in homotypic adhesion. They are highly expressed during embryonic development in a variety of tissues including the nervous system whereby in adult stages the protein level of CAR and CLMP decreases, only BT-IgSF expression increases within age. CAR-related proteins are concentrated at specialized cell-cell communication sites such as gap or tight junctions and are present at the plasma membrane in larger protein complexes. Considerable progress has been made on the molecular structure and interactions of CAR while research on CLMP and BT-IgSF is at an early stage. Studies on mouse mutants revealed biological functions of CAR in the heart and for CLMP in the gastrointestinal and urogenital systems. Furthermore, CAR and BT-IgSF appear to regulate synaptic function in the hippocampus.
- The role of Gpi-anchored axonal glycoproteins in neural development and neurological disorders. [Review]
- MCMol Cell Neurosci 2016 Nov 18
- This review article focuses on the Contactin (CNTN) subset of the Immunoglobulin supergene family (IgC2/FNIII molecules), whose components share structural properties (the association of Immunoglobul...
This review article focuses on the Contactin (CNTN) subset of the Immunoglobulin supergene family (IgC2/FNIII molecules), whose components share structural properties (the association of Immunoglobulin type C2 with Fibronectin type III domains), as well as a general role in cell contact formation and axonal growth control. IgC2/FNIII molecules include 6 highly related components (CNTN 1-6), associated with the cell membrane via a Glycosyl Phosphatidyl Inositol (GPI)-containing lipid tail. Contactin 1 and Contactin 2 share ~50 (49.38)% identity at the aminoacid level. They are components of the cell surface, from which they may be released in soluble forms. They bind heterophilically to multiple partners in cis and in trans, including members of the related L1CAM family and of the Neurexin family Contactin-associated proteins (CNTNAPs or Casprs). Such interactions are important for organising the neuronal membrane, as well as for modulating the growth and pathfinding of axon tracts. In addition, they also mediate the functional maturation of axons by promoting their interactions with myelinating cells at the nodal, paranodal and juxtaparanodal regions. Such interactions also mediate differential ionic channels (both Na(+) and K(+)) distribution, which is of critical relevance in the generation of the peak-shaped action potential. Indeed, thanks to their interactions with Ankyrin G, Na(+) channels map within the nodal regions, where they drive axonal depolarization. However, no ionic channels are found in the flanking Contactin1-containing paranodal regions, where CNTN1 interactions with Caspr1 and with the Ig superfamily component Neurofascin 155 in cis and in trans, respectively, build a molecular barrier between the node and the juxtaparanode. In this region K(+) channels are clustered, depending upon molecular interactions with Contactin 2 and with Caspr2. In addition to these functions, the Contactins appear to have also a role in degenerative and inflammatory disorders: indeed Contactin 2 is involved in neurodegenerative disorders with a special reference to the Alzheimer disease, given its ability to work as a ligand of the Alzheimer Precursor Protein (APP), which results in increased Alzheimer Intracellular Domain (AICD) release in a γ-secretase-dependent manner. On the other hand Contactin-1 drives Notch signalling activation via the Hes pathway, which could be consistent with its ability to modulate neuroinflammation events, and with the possibility that Contactin 1-dependent interactions may participate to the pathogenesis of the Multiple Sclerosis and of other inflammatory disorders.
- Regulation of extrasynaptic signaling by polysialylated NCAM: Impact for synaptic plasticity and cognitive functions. [Review]
- MCMol Cell Neurosci 2016 Nov 16
- The activation of synaptic N-methyl-d-aspartate-receptors (NMDARs) is crucial for induction of synaptic plasticity and supports cell survival, whereas activation of extrasynaptic NMDARs inhibits long...
The activation of synaptic N-methyl-d-aspartate-receptors (NMDARs) is crucial for induction of synaptic plasticity and supports cell survival, whereas activation of extrasynaptic NMDARs inhibits long-term potentiation and triggers neurodegeneration. A soluble polysialylated form of the neural cell adhesion molecule (polySia-NCAM) suppresses signaling through peri-/extrasynaptic GluN2B-containing NMDARs. Genetic or enzymatic manipulations blocking this mechanism result in impaired synaptic plasticity and learning, which could be repaired by reintroduction of polySia, or inhibition of either GluN1/GluN2B receptors or downstream signaling through RasGRF1 and p38 MAP kinase. Ectodomain shedding of NCAM, and hence generation of soluble NCAM, is controlled by metalloproteases of a disintegrin and metalloprotease (ADAM) family. As polySia-NCAM is predominantly associated with GABAergic interneurons in the prefrontal cortex, it is noteworthy that EphrinA5/EphA3-induced ADAM10 activity promotes polySia-NCAM shedding in these neurons. Thus, in addition to the well-known regulation of synaptic NMDARs by the secreted molecule Reelin, shed polySia-NCAM may restrain activation of extrasynaptic NMDARs. These data support a concept that GABAergic interneuron-derived extracellular proteins control the balance in synaptic/extrasynaptic NMDAR-mediated signaling in principal cells. Strikingly, dysregulation of Reelin or polySia expression is linked to schizophrenia. Thus, targeting of the GABAergic interneuron-principle cell communication and restoring the balance in synaptic/extrasynaptic NMDARs represent promising strategies for treatment of psychiatric diseases.
- Neural Stem Cells Promote Nerve Regeneration through IL12-induced Schwann cell Differentiation. [Journal Article]
- MCMol Cell Neurosci 2016 Nov 16
- Regeneration of injured peripheral nerves is a slow, complicated process that could be improved by implantation of neural stem cells (NSCs) or nerve conduit. Implantation of NSCs along with conduits ...
Regeneration of injured peripheral nerves is a slow, complicated process that could be improved by implantation of neural stem cells (NSCs) or nerve conduit. Implantation of NSCs along with conduits promotes the regeneration of damaged nerve, likely because (i) conduit supports and guides axonal growth from one nerve stump to the other, while preventing fibrous tissue ingrowth and retaining neurotrophic factors; and (ii) implanted NSCs differentiate into Schwann cells and maintain a growth factor enriched microenvironment, which promotes nerve regeneration. In this study, we identified IL12p80 (homodimer of IL12p40) in the cell extracts of implanted nerve conduit combined with NSCs by using protein antibody array and Western blotting. Levels of IL12p80 in these conduits are 1.6-fold higher than those in conduits without NSCs. In the sciatic nerve injury mouse model, implantation of NSCs combined with nerve conduit and IL12p80 improves motor recovery and increases the diameter up to 4.5-fold, at the medial site of the regenerated nerve. In vitro study further revealed that IL12p80 stimulates the Schwann cell differentiation of mouse NSCs through the phosphorylation of signal transducer and activator of transcription 3 (Stat3). These results suggest that IL12p80 can trigger Schwann cell differentiation of mouse NSCs through Stat3 phosphorylation and enhance the functional recovery and the diameter of regenerated nerves in a mouse sciatic nerve injury model.
- Early monitoring and quantitative evaluation of macrophage infiltration after experimental traumatic brain injury: A magnetic resonance imaging and flow cytometric analysis. [Journal Article]
- MCMol Cell Neurosci 2016 Nov 16; 78:25-34
- The inflammatory response following traumatic brain injury (TBI) is regulated by phagocytic cells. These cells comprising resident microglia and infiltrating macrophages play a pivotal role in the in...
The inflammatory response following traumatic brain injury (TBI) is regulated by phagocytic cells. These cells comprising resident microglia and infiltrating macrophages play a pivotal role in the interface between early detrimental and delayed beneficial effects of inflammation. The aim of the present study was to monitor the early effect of monocyte/phagocytic accumulation and further to explore its kinetics in TBI mice. Localized macrophage population was monitored using ultrasmall superparamagnetic iron oxide (USPIO) nanoparticle enhanced in vivo serial magnetic resonance imaging (MRI). Flow cytometry based gating study was performed to discriminate between resident microglia (Ly6G(-)CD11b(+)CD45(low)) and infiltrating macrophages (Ly6G(-)CD11b(+)CD45(high)) at the injury site. The T2* relaxation analysis revealed that maximum macrophage infiltration occurs between 66 and 72h post injury (42-48h post administration of USPIO) at the site of inflammation. This imaging data was well supported by iron oxide specific Prussian blue staining and macrophage specific F4/80 immunohistochemistry (IHC) analysis. Quantitative real-time PCR analysis found significant expression of monocyte chemoattractant protein-1 (MCP-1) at 72h post injury. Also, we found that flow cytometric analysis demonstrated a 7-fold increase in infiltrating macrophages around 72h post injuries as compared to control. The MR imaging in combination with flow cytometric analysis enabled the dynamic measurement of macrophage infiltration at the injury site. This study may help in setting an optimal time window to intervene and prevent damage due to inflammation and to increase the therapeutic efficacy.
- Neurexin, Neuroligin and Wishful Thinking coordinate synaptic cytoarchitecture and growth at neuromuscular junctions. [Journal Article]
- MCMol Cell Neurosci 2016 Nov 10; 78:9-24
- Trans-synaptic interactions involving Neurexins and Neuroligins are thought to promote adhesive interactions for precise alignment of the pre- and postsynaptic compartments and organize synaptic macr...
Trans-synaptic interactions involving Neurexins and Neuroligins are thought to promote adhesive interactions for precise alignment of the pre- and postsynaptic compartments and organize synaptic macromolecular complexes across species. In Drosophila, while Neurexin (Dnrx) and Neuroligins (Dnlg) are emerging as central organizing molecules at synapses, very little is known of the spectrum of proteins that might be recruited to the Dnrx/Dnlg trans-synaptic interface for organization and growth of the synapses. Using full length and truncated forms of Dnrx and Dnlg1 together with cell biological analyses and genetic interactions, we report novel functions of Dnrx and Dnlg1 in clustering of pre- and postsynaptic proteins, coordination of synaptic growth and ultrastructural organization. We show that Dnrx and Dnlg1 extracellular and intracellular regions are required for proper synaptic growth and localization of Dnlg1 and Dnrx, respectively. dnrx and dnlg1 single and double mutants display altered subcellular distribution of Discs large (Dlg), which is the homolog of mammalian post-synaptic density protein, PSD95. dnrx and dnlg1 mutants also display ultrastructural defects ranging from abnormal active zones, misformed pre- and post-synaptic areas with underdeveloped subsynaptic reticulum. Interestingly, dnrx and dnlg1 mutants have reduced levels of the Bone Morphogenetic Protein (BMP) receptor Wishful thinking (Wit), and Dnrx and Dnlg1 are required for proper localization and stability of Wit. In addition, the synaptic overgrowth phenotype resulting from the overexpression of Dnrx fails to manifest in wit mutants. Phenotypic analyses of dnrx/wit and dnlg1/wit mutants indicate that Dnrx/Dnlg1/Wit coordinate synaptic growth and architecture at the NMJ. Our findings also demonstrate that loss of Dnrx and Dnlg1 leads to decreased levels of the BMP co-receptor, Thickveins and the downstream effector phosphorylated Mad at the Neuromuscular Junction (NMJ) synapses indicating that Dnrx/Dnlg1 regulate components of the BMP signaling pathway. Together our findings reveal that Dnrx/Dnlg are at the core of a highly orchestrated process that combines adhesive and signaling mechanisms to ensure proper synaptic organization and growth during NMJ development.
- Tenascin-C in the matrisome of neural stem and progenitor cells. [Review]
- MCMol Cell Neurosci 2016 Nov 09
- The extracellular matrix consists of glycoproteins, proteoglycans and complex glycan structures that form the matrisome. Increasing evidence points to important functional roles of the ECM during dev...
The extracellular matrix consists of glycoproteins, proteoglycans and complex glycan structures that form the matrisome. Increasing evidence points to important functional roles of the ECM during development, plasticity and regeneration of the CNS. In particular, the ECM is an important constituent of the molecular microenvironment of the neural stem cell niches. While substantial evidence suggests that growth factors, cytokines and morphogens play important regulatory roles in the niche, the biological significance of the ECM has been less well studied. In this regard, the glycoprotein of the extracellular matrix tenascin-C is of interest because it can be considered as a model of the autochthonous ECM of the nervous system. Tenascin-C is expressed by the radial glia stem cells of the CNS and is a pivotal component of the adult stem cell niches. Furthermore, tenascin-C is associated with glial tumors and upregulated in CNS lesions, which may as well involve the stem cell compartment. In this review, we discuss the current state of research suggesting that tenascin-C plays an important modulatory role with regard to neural stem and glial progenitor cell proliferation and differentiation. In light of these results, tenascin-C and/or -derived peptides may be promising tools for the construction of synthetic stem cell environments.
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- Phosphoinositide 3-kinase γ ties chemoattractant- and adrenergic control of microglial motility. [Journal Article]
- MCMol Cell Neurosci 2016 Nov 05; 78:1-8
- Microglial motility is tightly controlled by multitude of agonistic and antagonistic factors. Chemoattractants, released after infection or damage of the brain, provoke directed migration of microgli...
Microglial motility is tightly controlled by multitude of agonistic and antagonistic factors. Chemoattractants, released after infection or damage of the brain, provoke directed migration of microglia to the pathogenic incident. In contrast, noradrenaline and other stress hormones have been shown to suppress microglial movement. Here we asked for the signaling reactions involved in the positive and negative control of microglial motility. Using pharmacological and genetic approaches we identified the lipid kinase activity of phosphoinositide 3-kinase species γ (PI3Kγ) as an essential mediator of microglial migration provoked by the complement component C5a and other chemoattractants. Inhibition of PI3Kγ lipid kinase activity by protein kinase A was disclosed as mechanism causing suppression of microglial migration by noradrenaline. Together these data characterize PI3Kγ as a nodal point in the control of microglial motility.