Gene_locus Report for: ratno-2neur

The molecular mechanisms that drive glia-glial interactions and glia-neuronal interactions during the development of the nervous system are poorly understood. A number of membrane-bound cell adhesion molecules have been shown to play a role, although the precise nature of their involvement is unknown. One class of molecules with cell adhesive properties used in the nervous system is the serine-esterase-like family of transmembrane proteins. A member of this class, a glia-specific protein called gliotactin, has been shown to be necessary for the development of the glial sheath in the peripheral nervous system of Drosophila melanogaster. Gliotactin is essential for the development of septate junctions in the glial sheath of individual and neighboring glia. Mutations that remove this protein result in paralysis and eventually death due to a breakdown in the glial-based blood-nerve barrier. To study the role of gliotactin during vertebrate nervous system development, we have isolated a potential vertebrate gliotactin homologue from mice and rat and found that it corresponds to neuroligin 3. Using a combination of RT-PCR and immunohistochemistry, we have found that neuroligin 3 is expressed during the development of the nervous system in many classes of glia. In particular neuroligin 3 is expressed in the olfactory ensheathing glia, retinal astrocytes, Schwann cells, and spinal cord astrocytes in the developing embryo. This expression is developmentally controlled such that in postnatal and adult stages, neuroligin 3 continues to be expressed at high levels in the olfactory ensheathing glia, a highly plastic class of glia that retain many of their developmental characteristics throughout life.

Neuroligin 1 is a neuronal cell surface protein that binds to a subset of neurexins, polymorphic cell surface proteins that are also localized on neurons (Ichtchenko, K., Hata, Y., Nguyen, T., Ullrich, B., Missler, M., Moomaw, C., and Sudhof, T. C. (1995) Cell 81, 435-443). We now describe two novel neuroligins called neuroligins 2 and 3 that are similar in structure and sequence to neuroligin 1. All neuroligins contain an N-terminal hydrophobic sequence with the characteristics of a cleaved signal peptide followed by a large esterase homology domain, a highly conserved single transmembrane region, and a short cytoplasmic domain. The three neuroligins are alternatively spliced at the same position and are expressed at high levels only in brain. Binding studies demonstrate that all three neuroligins bind to beta-neurexins both as native brain proteins and as recombinant proteins. Tight binding of the three neuroligins to beta-neurexins is observed only for beta-neurexins lacking an insert in splice site 4. Thus, neuroligins constitute a multigene family of brain-specific proteins with distinct isoforms that may have overlapping functions in mediating recognition processes between neurons.

Neurexins are neuronal cell surface proteins with hundreds of isoforms generated by alternative splicing. Here we describe neuroligin 1, a neuronal cell surface protein that is enriched in synaptic plasma membranes and acts as a splice site-specific ligand for beta-neurexins. Neuroligin 1 binds to beta-neurexins only if they lack an insert in the alternatively spliced sequence of the G domain, but not if they contain an insert. The extracellular sequence of neuroligin 1 is composed of a catalytically inactive esterase domain homologous to acetylcholinesterase. In situ hybridization reveals that alternative splicing of neurexins at the site recognized by neuroligin 1 is highly regulated. These findings support a model whereby alternative splicing of neurexins creates a family of cell surface receptors that confers interactive specificity onto their resident neurons.

Neuroligins and neurexins promote synapse development and validation by forming trans-synaptic bridges spanning the synaptic cleft. Select pairs promote excitatory and inhibitory synapses, with neuroligin 2 (NLGN2) limited to inhibitory synapses and neuroligin 1 (NLGN1) dominating at excitatory synapses. The cell-surface molecules, MAM domain-containing glycosylphosphatidylinositol anchor 1 (MDGA1) and 2 (MDGA2), regulate trans-synaptic adhesion between neurexins and neuroligins, impacting NLGN2 and NLGN1, respectively. We have determined the molecular mechanism of MDGA action. MDGA1 Ig1-Ig2 is sufficient to bind NLGN2 with nanomolar affinity; its crystal structure reveals an unusual locked rod-shaped array. In the crystal structure of the complex, two MDGA1 Ig1-Ig2 molecules each span the entire NLGN2 dimer. Site-directed mutagenesis confirms the observed interaction interface. Strikingly, Ig1 from MDGA1 binds to the same region on NLGN2 as neurexins do. Thus, MDGAs regulate the formation of neuroligin-neurexin trans-synaptic bridges by sterically blocking access of neurexins to neuroligins.

Deregulated cellular signalling is a common hallmark of disease, and delineating tissue phosphoproteomes is key to unravelling the underlying mechanisms. Here we present the broadest tissue catalogue of phosphoproteins to date, covering 31,480 phosphorylation sites on 7,280 proteins quantified across 14 rat organs and tissues. We provide the data set as an easily accessible resource via a web-based database, the CPR PTM Resource. A major fraction of the presented phosphorylation sites are tissue-specific and modulate protein interaction networks that are essential for the function of individual organs. For skeletal muscle, we find that phosphotyrosines are over-represented, which is mainly due to proteins involved in glycogenolysis and muscle contraction, a finding we validate in human skeletal muscle biopsies. Tyrosine phosphorylation is involved in both skeletal and cardiac muscle contraction, whereas glycogenolytic enzymes are tyrosine phosphorylated in skeletal muscle but not in the liver. The presented phosphoproteomic method is simple and rapid, making it applicable for screening of diseased tissue samples.

The laboratory rat (Rattus norvegicus) is an indispensable tool in experimental medicine and drug development, having made inestimable contributions to human health. We report here the genome sequence of the Brown Norway (BN) rat strain. The sequence represents a high-quality 'draft' covering over 90% of the genome. The BN rat sequence is the third complete mammalian genome to be deciphered, and three-way comparisons with the human and mouse genomes resolve details of mammalian evolution. This first comprehensive analysis includes genes and proteins and their relation to human disease, repeated sequences, comparative genome-wide studies of mammalian orthologous chromosomal regions and rearrangement breakpoints, reconstruction of ancestral karyotypes and the events leading to existing species, rates of variation, and lineage-specific and lineage-independent evolutionary events such as expansion of gene families, orthology relations and protein evolution.

The molecular mechanisms that drive glia-glial interactions and glia-neuronal interactions during the development of the nervous system are poorly understood. A number of membrane-bound cell adhesion molecules have been shown to play a role, although the precise nature of their involvement is unknown. One class of molecules with cell adhesive properties used in the nervous system is the serine-esterase-like family of transmembrane proteins. A member of this class, a glia-specific protein called gliotactin, has been shown to be necessary for the development of the glial sheath in the peripheral nervous system of Drosophila melanogaster. Gliotactin is essential for the development of septate junctions in the glial sheath of individual and neighboring glia. Mutations that remove this protein result in paralysis and eventually death due to a breakdown in the glial-based blood-nerve barrier. To study the role of gliotactin during vertebrate nervous system development, we have isolated a potential vertebrate gliotactin homologue from mice and rat and found that it corresponds to neuroligin 3. Using a combination of RT-PCR and immunohistochemistry, we have found that neuroligin 3 is expressed during the development of the nervous system in many classes of glia. In particular neuroligin 3 is expressed in the olfactory ensheathing glia, retinal astrocytes, Schwann cells, and spinal cord astrocytes in the developing embryo. This expression is developmentally controlled such that in postnatal and adult stages, neuroligin 3 continues to be expressed at high levels in the olfactory ensheathing glia, a highly plastic class of glia that retain many of their developmental characteristics throughout life.

Neuroligin 1 is a neuronal cell surface protein that binds to a subset of neurexins, polymorphic cell surface proteins that are also localized on neurons (Ichtchenko, K., Hata, Y., Nguyen, T., Ullrich, B., Missler, M., Moomaw, C., and Sudhof, T. C. (1995) Cell 81, 435-443). We now describe two novel neuroligins called neuroligins 2 and 3 that are similar in structure and sequence to neuroligin 1. All neuroligins contain an N-terminal hydrophobic sequence with the characteristics of a cleaved signal peptide followed by a large esterase homology domain, a highly conserved single transmembrane region, and a short cytoplasmic domain. The three neuroligins are alternatively spliced at the same position and are expressed at high levels only in brain. Binding studies demonstrate that all three neuroligins bind to beta-neurexins both as native brain proteins and as recombinant proteins. Tight binding of the three neuroligins to beta-neurexins is observed only for beta-neurexins lacking an insert in splice site 4. Thus, neuroligins constitute a multigene family of brain-specific proteins with distinct isoforms that may have overlapping functions in mediating recognition processes between neurons.

Neurexins are neuronal cell surface proteins with hundreds of isoforms generated by alternative splicing. Here we describe neuroligin 1, a neuronal cell surface protein that is enriched in synaptic plasma membranes and acts as a splice site-specific ligand for beta-neurexins. Neuroligin 1 binds to beta-neurexins only if they lack an insert in the alternatively spliced sequence of the G domain, but not if they contain an insert. The extracellular sequence of neuroligin 1 is composed of a catalytically inactive esterase domain homologous to acetylcholinesterase. In situ hybridization reveals that alternative splicing of neurexins at the site recognized by neuroligin 1 is highly regulated. These findings support a model whereby alternative splicing of neurexins creates a family of cell surface receptors that confers interactive specificity onto their resident neurons.