The neuronal cell adhesion molecule axonin‐1 is composed of six immunoglobulin and four fibronectin type III domains. Axonin‐1 promotes neurite outgrowth, when presented as a substratum for neurons ...in vitro, via a neuronal receptor that has been identified as the neuron‐glia cell adhesion molecule, NgCAM, based on the blocking effect of polyclonal antibodies directed to NgCAM. Here we report the identification of axonin‐1 domains involved in NgCAM binding. NgCAM‐conjugated microspheres were tested for binding to COS cells expressing domain deletion mutants of axonin‐1. In addition, monoclonal antibodies directed to axonin‐1 were assessed for their ability to block the axonin‐1‐NgCAM interaction, and their epitopes were mapped using the domain deletion mutants. The results suggest that the four amino‐terminal immunoglobulin domains of axonin‐1 form a domain conglomerate which is necessary and sufficient for NgCAM binding. Surprisingly, NgCAM binding to membrane‐bound axonin‐1 was increased strongly by deletion of the fifth or sixth immunoglobulin domains of axonin‐1. Based on these results and on negative staining electron microscopy, we propose a horseshoe‐shaped domain arrangement of axonin‐1 that obscures the NgCAM binding site. Neurite outgrowth studies with truncated forms of axonin‐1 show that axonin‐1 is a neurite outgrowth‐promoting substratum in the absence of the NgCAM binding site.
NA60 is an experiment at the CERN-SPS devoted to the study of dimuon production in heavy-ion and proton-nucleus collisions. The main topics under study are low mass vector meson production, ...J/\(\psi\) production and suppression, and the sources of the dimuon continuum in the mass range 1.2-2.7 GeV/c2. In 2003, NA60 collected \(\sim 230\) million dimuon events from Indium-Indium collisions. We present preliminary results of the analysis of this data sample in view of measuring the open charm contribution to the dimuon spectrum. Although we are still working on the final background subtraction procedure, we can already demonstrate that the detector performance is good enough to allow the separation of prompt dimuons from muon pairs originating in distant D \(\overline{\rm D}\) decays.
Neuroserpin Galliciotti, Giovanna; Sonderegger, Peter
Frontiers in bioscience,
2006-Jan-01, Letnik:
11
Journal Article
Recenzirano
Odprti dostop
Neuroserpin is a member of the serpin family of serine protease inhibitors. Tissue distribution analysis reveals a predominantly neuronal expression during the late stages of neurogenesis and, in the ...adult brain, in areas where synaptic changes are associated with learning and memory (synaptic plasticity). In vitro studies revealed complex formation between neuroserpin and different serine proteases, i.e. tPA, uPA, and plasmin. The neuroserpin-target complex has so far not been characterized in vivo. However, some investigations help to understand the functional role of this serpin. Neuroserpin was shown to be involved in the regulation of the morphology of neuroendocrine cells in culture, possibly by modulating the degradation of the extracellular matrix by proteolytic enzymes such as tPA. Moreover, a role of neuroserpin in mood regulation has been deduced from the over- and underexpression of neuroserpin in genetically modified mice, which showed increased anxiety and novelty-induced hypo-locomotion. In pathological conditions of the central nervous system (i.e. stroke and seizures), neuroserpin plays a neuroprotective role, probably by blocking the deleterious effects of tPA. A familial form of a neurodegenerative disease, termed familial encephalopathy with neuroserpin inclusion bodies, is caused by point mutations in the neuroserpin gene. This condition is characterized by the intracellular polymerization and accumulation of mutated neuroserpin, leading to neuronal death and dementia.
The synaptic serine protease neurotrypsin is thought to be important for adaptive synaptic processes required for cognitive functions, because humans deficient in neurotrypsin suffer from severe ...mental retardation. In the present study, we describe the biochemical characterization of neurotrypsin and its so far unique substrate agrin. In cell culture experiment as well as in neurotrypsin-deficient mice, we showed that agrin cleavage depends on neurotrypsin and occurs at two conserved sites. Neurotrypsin and agrin were expressed recombinantly, purified, and assayed in vitro. A catalytic efficiency of 1.3 x 10⁴ M⁻¹ · s⁻¹ was determined. Neurotrypsin activity was shown to depend on calcium with an optimal activity in the pH range of 7-8.5. Mutagenesis analysis of the amino acids flanking the scissile bonds showed that cleavage is highly specific due to the unique substrate recognition pocket of neurotrypsin at the active site. The C-terminal agrin fragment released after cleavage has recently been identified as an inactivating ligand of the Na⁺/K⁺-ATPase at CNS synapses, and its binding has been demonstrated to regulate presynaptic excitability. Therefore, dysregulation of agrin processing is a good candidate for a pathogenetic mechanism underlying mental retardation. In turn, these results may also shed light on mechanisms involved in cognitive functions.--Reif, R., Sales, S., Hettwer, S., Dreier, B., Gisler, C., Wölfel, J., Lüscher, D., Zurlinden, A., Stephan, A., Ahmed, S., Baici, A., Ledermann, B., Kunz, B., Sonderegger, P. Specific cleavage of agrin by neurotrypsin, a synaptic protease linked to mental retardation.
Synaptosomes are isolated synapses produced by subcellular fractionation of brain tissue. They contain the complete presynaptic terminal, including mitochondria and synaptic vesicles, and portions of ...the postsynaptic side, including the postsynaptic membrane and the postsynaptic density (PSyD). A proteomic characterisation of synaptosomes isolated from mouse brain was performed employing the isotope‐coded affinity tag (ICAT) method and tandem mass spectrometry (MS/MS). After isotopic labelling and tryptic digestion, peptides were fractionated by cation exchange chromatography and cysteine‐containing peptides were isolated by affinity chromatography. The peptides were identified by microcapillary liquid chromatography‐electrospray ionisation MS/MS (μLC‐ESI MS/MS). In two experiments, peptides representing a total of 1131 database entries were identified. They are involved in different presynaptic and postsynaptic functions, including synaptic vesicle exocytosis for neurotransmitter release, vesicle endocytosis for synaptic vesicle recycling, as well as postsynaptic receptors and proteins constituting the PSyD. Moreover, a large number of soluble and membrane‐bound molecules serving functions in synaptic signal transduction and metabolism were detected. The results provide an inventory of the synaptic proteome and confirm the suitability of the ICAT method for the assessment of synaptic structure, function and plasticity.
NA60 results on thermal dimuons Arnaldi, R.; Banicz, K.; Borer, K. ...
European physical journal. C, Particles and fields (Print),
06/2009, Letnik:
61, Številka:
4
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The NA60 experiment at the CERN SPS has measured muon pairs with unprecedented precision in 158
A
GeV In–In collisions. A strong excess of pairs above the known sources is observed in the whole ...mass region 0.2<
M
<2.6 GeV. The mass spectrum for
M
<1 GeV is consistent with a dominant contribution from
π
+
π
−
→
ρ
→
μ
+
μ
−
annihilation. The associated
ρ
spectral function shows a strong broadening, but essentially no shift in mass. For
M
>1 GeV, the excess is found to be prompt, not due to enhanced charm production, with pronounced differences to Drell–Yan pairs. The slope parameter
T
eff
associated with the transverse momentum spectra rises with mass up to the
ρ
, followed by a sudden decline above. The rise for
M
<1 GeV is consistent with radial flow of a hadronic emission source. The seeming absence of significant flow for
M
>1 GeV and its relation to parton–hadron duality is discussed in detail, suggesting a dominantly partonic emission source in this region. A comparison of the data to the present status of theoretical modeling is also contained. The accumulated empirical evidence, including also a Planck-like shape of the mass spectra at low
p
T
and the lack of polarization, is consistent with a global interpretation of the excess dimuons as thermal radiation. We conclude with first results on
ω
in-medium effects.
φ meson production in NA60 Arnaldi, R.; Averbeck, R.; Banicz, K. ...
European Physical Journal C: Particles and Fields,
01/2007, Letnik:
49, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
NA60 is a fixed-target experiment at the CERN SPS which measured dimuon production in nucleus–nucleus and proton–nucleus collisions. The experiment collected muon pair samples of unprecedented ...quality in heavy-ion experiments. This paper presents a high quality measurement of the pT distribution of the φ meson, covering a broad pT window. The data were collected in 2003 in In-In collisions at 158 GeV per nucleon. The results, presented as a function of centrality, were studied against several possible sources of systematic effects and proved to be fairly stable. We show that the inverse mT slope measured in In-In collisions, in the φ→μμ decay channel, depends significantly on the range used to perform the fit. When the fit is performed at low transverse momentum, the effective inverse slope increases from peripheral to central collisions, as measured by other experiments. We finally show that our measurement for In-In is compatible with the overall systematics of T slope versus mass, measured in different collision systems by the NA49 experiment
The balance between tissue-type plasminogen activator (tPA) and one of its inhibitors, neuroserpin, has crucial roles in the central nervous system, including the control of neuronal migration, ...neuronal plasticity and neuronal death. In the present study, we demonstrate that the activation of the transforming growth factor-β (TGFβ)-related BMPR-IB (also known as BMPR1B and Alk6)- and Smad5-dependent signalling pathways controls neuroserpin transcription. Accordingly, we demonstrate for the first time that anti-Mullerian hormone (AMH), a member of the TGFβ family, promotes the expression of neuroserpin in cultured neurons but not in astrocytes. The relevance of these findings is confirmed by the presence of both AMH and AMH type-II receptor (AMHR-II) in brain tissues, and is supported by the observation of reduced levels of neuroserpin in the brain of AMHR-II-deficient mice. Interestingly, as previously demonstrated for neuroserpin, AMH protects neurons against N-methyl-D-aspartate (NMDA)-mediated excitotoxicity both in vitro and in vivo. This study demonstrates the existence of an AMH-dependent signalling pathway in the brain leading to an overexpression of the serine-protease inhibitor, neuroserpin, and neuronal survival.
Neural cell adhesion molecules of the immunoglobulin superfamily mediate cellular interactions via homophilic binding to identical molecules and heterophilic binding to other family members or ...structurally unrelated cell-surface glycoproteins. Here we report on an interaction between axonin-1 and Nr-CAM/Bravo. In search for novel ligands of axonin-1, fluorescent polystyrene microspheres conjugated with axonin-1 were found to bind to peripheral glial cells from dorsal root ganglia. By antibody blockage experiments an axonin-1 receptor on the glial cells was identified as Nr-CAM. The specificity of the interaction was confirmed with binding studies using purified axonin-1 and Nr-CAM. In cultures of dissociated dorsal root ganglia antibodies against axonin-1 and Nr-CAM perturbed the formation of contacts between neurites and peripheral glial cells. Together, these results implicate a binding between axonin-1 of the neuritic and Nr-CAM of the glial cell membrane in the early phase of axon ensheathment in the peripheral nervous system.
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