The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Barbara Ranscht - One of the best experts on this subject based on the ideXlab platform.
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Contactin 1 regulates myelination and nodal paranodal domain organization in the central nervous system
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Gulsen Colakoglu, Erik O. Berglund, Ulrika Bergstromtyrberg, Barbara RanschtAbstract:Myelin, a multilayered membrane sheath formed by oligodendrocytes around axons in the CNS, enables rapid nerve impulse conduction and sustains neuronal health. The signals exchanged between axons and oligodendrocytes in myelin remain to be fully elucidated. Here we provide genetic evidence for multiple and critical functions of Contactin-1 in central myelin. We document dynamic Contactin-1 expression on oligodendrocytes in vivo, and progressive accumulation at nodes of Ranvier and paranodes during postnatal mouse development. Nodal and paranodal expression stabilized in mature myelin, but overall membranous expression diminished. Contactin-1–deficiency disrupted paranodal junction formation as evidenced by loss of Caspr, mislocalized potassium Kv1.2 channels, and abnormal myelin terminal loops. Reduced numbers and impaired maturation of sodium channel clusters accompanied this phenotype. Histological, electron microscopic, and biochemical analyses uncovered significant hypomyelination in Contactin-1–deficient central nerves, with up to 60% myelin loss. Oligodendrocytes were present in normal numbers, albeit a minor population of neuronal/glial antigen 2-positive (NG2+) progenitors lagged in maturation by postnatal day 18, when the mouse null mutation was lethal. Major contributing factors to hypomyelination were defects in the generation and organization of myelin membranes, as judged by electron microscopy and quantitative analysis of oligodendrocyte processes labeled by GFP transgenically expressed from the proteolipid protein promoter. These data reveal that Contactin-1 regulates both myelin formation and organization of nodal and paranodal domains in the CNS. These multiple roles distinguish central Contactin-1 functions from its specific role at paranodes in the periphery, and emphasize mechanistic differences in central and peripheral myelination.
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differential clustering of caspr by oligodendrocytes and schwann cells
Journal of Neuroscience Research, 2009Co-Authors: Menahem Eisenbach, Yael Eshedeisenbach, Trent A Watkins, Susan C Barnett, Barbara Ranscht, Peter J. Brophy, Christine E. Thomson, Elena Kartvelishvily, Annette Sorensen, Elior PelesAbstract:Formation of the paranodal axoglial junction (PNJ) requires the presence of three cell adhesion molecules: the 155-kDa isoform of neurofascin (NF155) on the glial membrane and a complex of Caspr and Contactin found on the axolemma. Here we report that the clustering of Caspr along myelinated axons during development differs fundamentally between the central (CNS) and peripheral (PNS) nervous systems. In cultures of Schwann cells (SC) and dorsal root ganglion (DRG) neurons, membrane accumulation of Caspr was detected only after myelination. In contrast, in oligodendrocytes (OL)/DRG neurons cocultures, Caspr was clustered upon initial glial cell contact already before myelination had begun. Premyelination clustering of Caspr was detected in cultures of oligodendrocytes and retinal ganglion cells, motor neurons, and DRG neurons as well as in mixed cell cultures of rat forebrain and spinal cords. Cocultures of oligodendrocyte precursor cells isolated from Contactin- or neurofascin-deficient mice with wild-type DRG neurons showed that clustering of Caspr at initial contact sites between OL processes and the axon requires glial expression of NF155 but not of Contactin. These results demonstrate that the expression of membrane proteins along the axolemma is determined by the type of the Contacting glial cells and is not an intrinsic characteristic of the axon.
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alterations of arcuate nucleus neuropeptidergic development in Contactin deficient mice comparison with anorexia and food deprived mice
European Journal of Neuroscience, 2005Co-Authors: Serguei O Fetissov, Ulrika Bergstrom, Jeanette E Johansen, Tomas Hokfelt, Martin Schalling, Barbara RanschtAbstract:A mutation in the Contactin-1 gene results in an ataxic and anorectic phenotype that is apparent by postnatal day 10 and lethal by postnatal day 19 [Berglund et al. (1999) Neuron 24, 739-750]. The resemblance of this phenotype with the anorexia (anx/anx) mouse mutation prompted us to investigate the hypothalamic neurochemistry of Contactin knock-out (KO) mice. Contactin was expressed in the hypothalamic neuropil of wild-type (WT) but not Contactin KO mice. In the KO condition, neuropeptide Y (NPY) and agouti-related protein (AgRP) immunoreactivity (IR) accumulated in the somata of arcuate nucleus neurons, whereas IR for these neuropeptides as well as for alpha-melanocyte-stimulating hormone (alpha-MSH) decreased in the corresponding axon projections. These changes in the pattern of neuropeptide expression in the Contactin-deficient hypothalamus were similar but more pronounced than those found in anx/anx mice. Increased levels of NPY and AgRP and decreased concentrations of pro-opiomelanocortin mRNA in arcuate neurons accompanied these changes. In relating these alterations a 24-h food deprivation period, we observed in 3-week-old WT mice an elevation of NPY- and AgRP-IR in the perikarya of arcuate neurons without notable reduction of NPY- or AgRP-IR in nerve fibers, suggesting that the decrease of arcuate projections can be associated with postnatal anorectic phenotype. Our data implicate Contactin in the postnatal development of the NPY/AgRP and alpha-MSH arcuate neurons and suggest that similar to anx/anx mutant mice, compromised orexigenic signaling via NPY/AgRP neurons may contribute to reduced food intake by the Contactin-mutant animals.
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retention of a cell adhesion complex at the paranodal junction requires the cytoplasmic region of caspr
Journal of Cell Biology, 2002Co-Authors: Leora Gollan, Erik O. Berglund, Barbara Ranscht, Sebastian Poliak, Helena Sabanay, Elior PelesAbstract:An axonal complex of cell adhesion molecules consisting of Caspr and Contactin has been found to be essential for the generation of the paranodal axo-glial junctions flanking the nodes of Ranvier. Here we report that although the extracellular region of Caspr was sufficient for directing it to the paranodes in transgenic mice, retention of the Caspr–Contactin complex at the junction depended on the presence of an intact cytoplasmic domain of Caspr. Using immunoelectron microscopy, we found that a Caspr mutant lacking its intracellular domain was often found within the axon instead of the junctional axolemma. We further show that a short sequence in the cytoplasmic domain of Caspr mediated its binding to the cytoskeleton-associated protein 4.1B. Clustering of Contactin on the cell surface induced coclustering of Caspr and immobilized protein 4.1B at the plasma membrane. Furthermore, deletion of the protein 4.1B binding site accelerated the internalization of a Caspr–Contactin chimera from the cell surface. These results suggest that Caspr serves as a “transmembrane scaffold” that stabilizes the Caspr/Contactin adhesion complex at the paranodal junction by connecting it to cytoskeletal components within the axon.
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Contactin supports synaptic plasticity associated with hippocampal long-term depression but not potentiation.
Current Biology, 2002Co-Authors: Keith K. Murai, Dinah Misner, Barbara RanschtAbstract:Background Changes in synaptic efficacy are believed to mediate the processes of learning and memory formation. Accumulating evidence implicates cell adhesion molecules in activity-dependent synaptic modifications associated with long-term potentiation (LTP); however, there is no precedence for the selective role of this molecule class in long-term depression (LTD). The mechanisms that modulate these processes still remain unclear. Results We report a novel role for glycosylphosphatidyl inositol (GPI)-anchored Contactin in hippocampal CA1 synaptic plasticity. Contactin selectively supports paired-pulse facilitation (PPF) and NMDA (N-methyl-D-aspartate) receptor-dependent LTD but is not required for synaptic morphology, basal transmission, or LTP. Molecular analyses indicate that Contactin is essential for the membrane and synaptic targeting of the Contactin-associated protein (Caspr/paranodin) and for the proper distribution of a presumptive ligand, receptor protein tyrosine phosphatase β (RPTPβ)/phosphacan. Conclusions These results indicate that Contactin plays a selective role in synaptic plasticity and identify PPF and LTD, but not LTP, as Contactin-dependent processes. Engagement of the Contactin-Caspr complex with RPTPβ may thus regulate cell-cell interactions contributing to specific synaptic plasticity forms.
Scott A Weed - One of the best experts on this subject based on the ideXlab platform.
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cortactin phosphorylation by casein kinase 2 regulates actin related protein 2 3 complex activity invadopodia function and tumor cell invasion
Molecular Cancer Research, 2019Co-Authors: Steven M Markwell, Dorothy A Schafer, Amanda Gatesman Ammer, Erik T Interval, Jessica L Allen, Brenen W Papenberg, River A Hames, Johnathan E Castano, Scott A WeedAbstract:Malregulation of the actin cytoskeleton enhances tumor cell motility and invasion. The actin-binding protein cortactin facilitates branched actin network formation through activation of the actin-related protein (Arp) 2/3 complex. Increased cortactin expression due to gene amplification is observed in head and neck squamous cell carcinoma (HNSCC) and other cancers, corresponding with elevated tumor progression and poor patient outcome. Arp2/3 complex activation is responsible for driving increased migration and extracellular matrix (ECM) degradation by governing invadopodia formation and activity. Although cortactin-mediated activation of Arp2/3 complex and invadopodia regulation has been well established, signaling pathways responsible for governing cortactin binding to Arp2/3 are unknown and potentially present a new avenue for anti-invasive therapeutic targeting. Here we identify casein kinase (CK) 2α phosphorylation of cortactin as a negative regulator of Arp2/3 binding. CK2α directly phosphorylates cortactin at a conserved threonine (T24) adjacent to the canonical Arp2/3 binding motif. Phosphorylation of cortactin T24 by CK2α impairs the ability of cortactin to bind Arp2/3 and activate actin nucleation. Decreased invadopodia activity is observed in HNSCC cells with expression of CK2α phosphorylation-null cortactin mutants, shRNA-mediated CK2α knockdown, and with the CK2α inhibitor Silmitasertib. Silmitasertib inhibits HNSCC collective invasion in tumor spheroids and orthotopic tongue tumors in mice. Collectively these data suggest that CK2α-mediated cortactin phosphorylation at T24 is critical in regulating cortactin binding to Arp2/3 complex and pro-invasive activity, identifying a potential targetable mechanism for impairing HNSCC invasion. Implications: This study identifies a new signaling pathway that contributes to enhancing cancer cell invasion. Visual Overview:http://mcr.aacrjournals.org/content/molcanres/17/4/987/F1.large.jpg.
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cortactin is a functional target of e cadherin activated src family kinases in mcf7 epithelial monolayers
Journal of Biological Chemistry, 2009Co-Authors: Gang Ren, Scott A Weed, Falak Helwani, Suzie Verma, Robert W Mclachlan, Alpha S YapAbstract:Src family kinases (SFKs) signal in response to E-cadherin to support cadherin adhesion and the integrity of cell-cell contacts (McLachlan, R. W., Kraemer, A., Helwani, F. M., Kovacs, E. M., and Yap, A. S. (2007) Mol. Biol. Cell 18, 3214-3223). We now identify the actin-regulatory protein, cortactin, as a target of E-cadherin-activated SFK signaling. Tyr-phosphorylated cortactin was found at cell-cell contacts in established epithelial monolayers, and cortactin became acutely tyrosine-phosphorylated when E-cadherin adhesion was engaged. In all circumstances, cortactin tyrosine phosphorylation was blocked by inhibiting SFK signaling. Importantly, Tyr-phosphorylated cortactin was necessary to preserve the integrity of cadherin contacts and the perijunctional actin cytoskeleton. Moreover, expression of a phosphomimetic cortactin mutant could prevent SFK blockade from disrupting cadherin organization, thereby placing cortactin functionally downstream of SFK signaling at cadherin adhesions. We conclude that SFK and cortactin constitute an important signaling pathway that functionally links E-cadherin adhesion and the actin cytoskeleton.
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cortactin and crk cooperate to trigger actin polymerization during shigella invasion of epithelial cells
Journal of Cell Biology, 2004Co-Authors: Laurence Bougneres, Scott A Weed, Thomas J Parsons, Andrei V. Karginov, Stephane Girardin, Jean Christophe Olivomarin, Philippe J Sansonetti, Guy Tran Van NhieuAbstract:Shigella, the causative agent of bacillary dysentery, invades epithelial cells in a process involving Src tyrosine kinase signaling. Cortactin, a ubiquitous actin-binding protein present in structures of dynamic actin assembly, is the major protein tyrosine phosphorylated during Shigella invasion. Here, we report that RNA interference silencing of cortactin expression, as does Src inhibition in cells expressing kinase-inactive Src, interferes with actin polymerization required for the formation of cellular extensions engulfing the bacteria. Shigella invasion induced the recruitment of cortactin at plasma membranes in a tyrosine phosphorylation–dependent manner. Overexpression of wild-type forms of cortactin or the adaptor protein Crk favored Shigella uptake, and Arp2/3 binding–deficient cortactin derivatives or an Src homology 2 domain Crk mutant interfered with bacterial-induced actin foci formation. Crk was shown to directly interact with tyrosine-phosphorylated cortactin and to condition cortactin-dependent actin polymerization required for Shigella uptake. These results point at a major role for a Crk–cortactin complex in actin polymerization downstream of tyrosine kinase signaling.
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Actin depolymerization-induced tyrosine phosphorylation of cortactin: the role of Fer kinase.
Biochemical Journal, 2004Co-Authors: Lingzhi Fan, Scott A Weed, Caterina Di Ciano-oliveira, Andrew W. B. Craig, Peter A. Greer, Ori D. Rotstein, Andras KapusAbstract:The F-actin-binding protein cortactin is an important regulator of cytoskeletal dynamics, and a prominent target of various tyrosine kinases. Tyrosine phosphorylation of cortactin has been suggested to reduce its F-actin cross-linking capability. In the present study, we investigated whether a reciprocal relationship exists, i.e. whether the polymerization state of actin impacts on the cortactin tyrosine phosphorylation. Actin depolymerization by LB (latrunculin B) induced robust phosphorylation of C-terminal tyrosine residues of cortactin. In contrast, F-actin stabilization by jasplakinolide, which redistributed cortactin to F-actin-containing patches, prevented cortactin phosphorylation triggered by hypertonic stress or LB. Using cell lines deficient in candidate tyrosine kinases, we found that the F-actin depolymerization-induced cortactin phosphorylation was mediated by the Fyn/Fer kinase pathway, independent of Src and c-Abl. LB caused modest Fer activation and strongly facilitated the association between Fer and cortactin. Interestingly, the F-actin-binding region within the cortactin N-terminus was essential for the efficient phosphorylation of C-terminal tyrosine residues. Investigating the structural requirements for the Fer-cortactin association, we found that (i) phosphorylation-incompetent cortactin still bound to Fer; (ii) the isolated N-terminus associated with Fer; and (iii) the C-terminus alone was insufficient for binding. Thus the cortactin N-terminus participates in the Fer-cortactin interaction, which cannot be fully due to the binding of the Fer Src homology 2 domain to C-terminal tyrosine residues of cortactin. Taken together, F-actin stabilization prevents cortactin tyrosine phosphorylation, whereas depolymerization promotes it. Depolymerization-induced phosphorylation is mediated by Fer, and requires the actin-binding domain of cortactin. These results define a novel F-actin-dependent pathway that may serve as a feedback mechanism during cytoskeleton remodelling.
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cortactin tyrosine phosphorylation requires rac1 activity and association with the cortical actin cytoskeleton
Molecular Biology of the Cell, 2003Co-Authors: Julie A Head, Thomas J Parsons, Dongyan Jiang, Lynda Zorn, Erik Schaefer, Scott A WeedAbstract:Cortactin is an F-actin binding protein that activates actin-related protein 2/3 complex and is localized within lamellipodia. Cortactin is a substrate for Src and other protein tyrosine kinases involved in cell motility, where its phosphorylation on tyrosines 421, 466, and 482 in the carboxy terminus is required for cell movement and metastasis. In spite of the importance of cortactin tyrosine phosphorylation in cell motility, little is known regarding the structural, spatial, or signaling requirements regulating cortactin tyrosine phosphorylation. Herein, we report that phosphorylation of cortactin tyrosine residues in the carboxy terminus requires the aminoterminal domain and Rac1-mediated localization to the cell periphery. Phosphorylation-specific antibodies directed against tyrosine 421 and 466 were produced to study the regulation and localization of tyrosine phosphorylated cortactin. Phosphorylation of cortactin tyrosine 421 and 466 was elevated in response to Src, epidermal growth factor receptor and Rac1 activation, and tyrosine 421 phosphorylated cortactin localized with F-actin in lamellipodia and podosomes. Cortactin tyrosine phosphorylation is progressive, with tyrosine 421 phosphorylation required for phosphorylation of tyrosine 466. These results indicate that cortactin tyrosine phosphorylation requires Rac1-induced cortactin targeting to cortical actin networks, where it is tyrosine phosphorylated in hierarchical manner that is closely coordinated with its ability to regulate actin dynamics.
Elior Peles - One of the best experts on this subject based on the ideXlab platform.
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antibodies to kv1 potassium channel complex proteins leucine rich glioma inactivated 1 protein and Contactin associated protein 2 in limbic encephalitis morvan s syndrome and acquired neuromyotonia
Brain, 2010Co-Authors: Sarosh R Irani, Elior Peles, Sian K Alexander, Patrick Waters, Kleopas A Kleopa, Philippa Pettingill, Luigi Zuliani, Camilla Buckley, Bethan Lang, Angela VincentAbstract:Antibodies that immunoprecipitate (125)I-alpha-dendrotoxin-labelled voltage-gated potassium channels extracted from mammalian brain tissue have been identified in patients with neuromyotonia, Morvan's syndrome, limbic encephalitis and a few cases of adult-onset epilepsy. These conditions often improve following immunomodulatory therapies. However, the proportions of the different syndromes, the numbers with associated tumours and the relationships with potassium channel subunit antibody specificities have been unclear. We documented the clinical phenotype and tumour associations in 96 potassium channel antibody positive patients (titres >400 pM). Five had thymomas and one had an endometrial adenocarcinoma. To define the antibody specificities, we looked for binding of serum antibodies and their effects on potassium channel currents using human embryonic kidney cells expressing the potassium channel subunits. Surprisingly, only three of the patients had antibodies directed against the potassium channel subunits. By contrast, we found antibodies to three proteins that are complexed with (125)I-alpha-dendrotoxin-labelled potassium channels in brain extracts: (i) Contactin-associated protein-2 that is localized at the juxtaparanodes in myelinated axons; (ii) leucine-rich, glioma inactivated 1 protein that is most strongly expressed in the hippocampus; and (iii) Tag-1/Contactin-2 that associates with Contactin-associated protein-2. Antibodies to Kv1 subunits were found in three sera, to Contactin-associated protein-2 in 19 sera, to leucine-rich, glioma inactivated 1 protein in 55 sera and to Contactin-2 in five sera, four of which were also positive for the other antibodies. The remaining 18 sera were negative for potassium channel subunits and associated proteins by the methods employed. Of the 19 patients with Contactin-associated protein-antibody-2, 10 had neuromyotonia or Morvan's syndrome, compared with only 3 of the 55 leucine-rich, glioma inactivated 1 protein-antibody positive patients (P < 0.0001), who predominantly had limbic encephalitis. The responses to immunomodulatory therapies, defined by changes in modified Rankin scores, were good except in the patients with tumours, who all had Contactin-associated-2 protein antibodies. This study confirms that the majority of patients with high potassium channel antibodies have limbic encephalitis without tumours. The identification of leucine-rich, glioma inactivated 1 protein and Contactin-associated protein-2 as the major targets of potassium channel antibodies, and their associations with different clinical features, begins to explain the diversity of these syndromes; furthermore, detection of Contactin-associated protein-2 antibodies should help identify the risk of an underlying tumour and a poor prognosis in future patients.
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differential clustering of caspr by oligodendrocytes and schwann cells
Journal of Neuroscience Research, 2009Co-Authors: Menahem Eisenbach, Yael Eshedeisenbach, Trent A Watkins, Susan C Barnett, Barbara Ranscht, Peter J. Brophy, Christine E. Thomson, Elena Kartvelishvily, Annette Sorensen, Elior PelesAbstract:Formation of the paranodal axoglial junction (PNJ) requires the presence of three cell adhesion molecules: the 155-kDa isoform of neurofascin (NF155) on the glial membrane and a complex of Caspr and Contactin found on the axolemma. Here we report that the clustering of Caspr along myelinated axons during development differs fundamentally between the central (CNS) and peripheral (PNS) nervous systems. In cultures of Schwann cells (SC) and dorsal root ganglion (DRG) neurons, membrane accumulation of Caspr was detected only after myelination. In contrast, in oligodendrocytes (OL)/DRG neurons cocultures, Caspr was clustered upon initial glial cell contact already before myelination had begun. Premyelination clustering of Caspr was detected in cultures of oligodendrocytes and retinal ganglion cells, motor neurons, and DRG neurons as well as in mixed cell cultures of rat forebrain and spinal cords. Cocultures of oligodendrocyte precursor cells isolated from Contactin- or neurofascin-deficient mice with wild-type DRG neurons showed that clustering of Caspr at initial contact sites between OL processes and the axon requires glial expression of NF155 but not of Contactin. These results demonstrate that the expression of membrane proteins along the axolemma is determined by the type of the Contacting glial cells and is not an intrinsic characteristic of the axon.
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caspr regulates the processing of Contactin and inhibits its binding to neurofascin
Journal of Cell Biology, 2003Co-Authors: Leora Gollan, Daniela Salomon, James L. Salzer, Elior PelesAbstract:Three cell adhesion molecules are present at the axoglial junctions that form between the axon and myelinating glia on either side of nodes of Ranvier. These include an axonal complex of contacin-associated protein (Caspr) and Contactin, which was proposed to bind NF155, an isoform of neurofascin located on the glial paranodal loops. Here, we show that NF155 binds directly to Contactin and that surprisingly, coexpression of Caspr inhibits this interaction. This inhibition reflects the association of Caspr with Contactin during biosynthesis and the resulting expression of a low molecular weight (LMw), endoglycosidase H–sensitive isoform of Contactin at the cell membrane, which remains associated with Caspr but is unable to bind NF155. Accordingly, deletion of Caspr in mice by gene targeting results in a shift from the LMw- to a HMw-Contactin glycoform. These results demonstrate that Caspr regulates the intracellular processing and transport of Contactin to the cell surface, thereby affecting its ability to interact with other cell adhesion molecules.
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retention of a cell adhesion complex at the paranodal junction requires the cytoplasmic region of caspr
Journal of Cell Biology, 2002Co-Authors: Leora Gollan, Erik O. Berglund, Barbara Ranscht, Sebastian Poliak, Helena Sabanay, Elior PelesAbstract:An axonal complex of cell adhesion molecules consisting of Caspr and Contactin has been found to be essential for the generation of the paranodal axo-glial junctions flanking the nodes of Ranvier. Here we report that although the extracellular region of Caspr was sufficient for directing it to the paranodes in transgenic mice, retention of the Caspr–Contactin complex at the junction depended on the presence of an intact cytoplasmic domain of Caspr. Using immunoelectron microscopy, we found that a Caspr mutant lacking its intracellular domain was often found within the axon instead of the junctional axolemma. We further show that a short sequence in the cytoplasmic domain of Caspr mediated its binding to the cytoskeleton-associated protein 4.1B. Clustering of Contactin on the cell surface induced coclustering of Caspr and immobilized protein 4.1B at the plasma membrane. Furthermore, deletion of the protein 4.1B binding site accelerated the internalization of a Caspr–Contactin chimera from the cell surface. These results suggest that Caspr serves as a “transmembrane scaffold” that stabilizes the Caspr/Contactin adhesion complex at the paranodal junction by connecting it to cytoskeletal components within the axon.
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Contactin orchestrates assembly of the septate like junctions at the paranode in myelinated peripheral nerve
Neuron, 2001Co-Authors: Mary E T Boyle, Erik O. Berglund, Barbara Ranscht, Elior Peles, Keith K. Murai, Lynne WeberAbstract:Rapid nerve impulse conduction depends on specialized membrane domains in myelinated nerve, the node of Ranvier, the paranode, and the myelinated internodal region. We report that GPI-linked Contactin enables the formation of the paranodal septate-like axo-glial junctions in myelinated peripheral nerve. Contactin clusters at the paranodal axolemma during Schwann cell myelination. Ablation of Contactin in mutant mice disrupts junctional attachment at the paranode and reduces nerve conduction velocity 3-fold. The mutation impedes intracellular transport and surface expression of Caspr and leaves NF155 on apposing paranodal myelin disengaged. The Contactin mutation does not affect sodium channel clustering at the nodes of Ranvier but alters the location of the Shaker-type Kv1.1 and Kv1.2 potassium channels. Thus, Contactin is a crucial part in the machinery that controls junctional attachment at the paranode and ultimately the physiology of myelinated nerve.
Thomas J Parsons - One of the best experts on this subject based on the ideXlab platform.
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hdac6 modulates cell motility by altering the acetylation level of cortactin
Molecular Cell, 2007Co-Authors: Xiaohong Zhang, Thomas J Parsons, Yingtao Zhang, Nancy Olashaw, Zhigang Yua, Sarah Yong, Alexis Salasburgos, Joh M Koome, Xiangjiao Yang, Tsopang YaoAbstract:Histone deacetylase 6 (HDAC6) is a tubulin-specific deacetylase that regulates microtubule-dependent cell movement. In this study, we identify the F-actin-binding protein cortactin as a HDAC6 substrate. We demonstrate that HDAC6 binds cortactin and that overexpression of HDAC6 leads to hypoacetylation of cortactin, whereas inhibition of HDAC6 activity leads to cortactin hyperacetylation. HDAC6 alters the ability of cortactin to bind F-actin by modulating a "charge patch" in its repeat region. Introduction of charge-preserving or charge-neutralizing mutations in this cortactin repeat region correlates with the gain or loss of F-actin binding ability, respectively. Cells expressing a charge-neutralizing cortactin mutant were less motile than control cells or cells expressing a charge-preserving mutant. These findings suggest that, in addition to its role in microtubule-dependent cell motility, HDAC6 influences actin-dependent cell motility by altering the acetylation status of cortactin, which, in turn, changes the F-actin binding activity of cortactin.
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cortactin and crk cooperate to trigger actin polymerization during shigella invasion of epithelial cells
Journal of Cell Biology, 2004Co-Authors: Laurence Bougneres, Scott A Weed, Thomas J Parsons, Andrei V. Karginov, Stephane Girardin, Jean Christophe Olivomarin, Philippe J Sansonetti, Guy Tran Van NhieuAbstract:Shigella, the causative agent of bacillary dysentery, invades epithelial cells in a process involving Src tyrosine kinase signaling. Cortactin, a ubiquitous actin-binding protein present in structures of dynamic actin assembly, is the major protein tyrosine phosphorylated during Shigella invasion. Here, we report that RNA interference silencing of cortactin expression, as does Src inhibition in cells expressing kinase-inactive Src, interferes with actin polymerization required for the formation of cellular extensions engulfing the bacteria. Shigella invasion induced the recruitment of cortactin at plasma membranes in a tyrosine phosphorylation–dependent manner. Overexpression of wild-type forms of cortactin or the adaptor protein Crk favored Shigella uptake, and Arp2/3 binding–deficient cortactin derivatives or an Src homology 2 domain Crk mutant interfered with bacterial-induced actin foci formation. Crk was shown to directly interact with tyrosine-phosphorylated cortactin and to condition cortactin-dependent actin polymerization required for Shigella uptake. These results point at a major role for a Crk–cortactin complex in actin polymerization downstream of tyrosine kinase signaling.
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cortactin tyrosine phosphorylation requires rac1 activity and association with the cortical actin cytoskeleton
Molecular Biology of the Cell, 2003Co-Authors: Julie A Head, Thomas J Parsons, Dongyan Jiang, Lynda Zorn, Erik Schaefer, Scott A WeedAbstract:Cortactin is an F-actin binding protein that activates actin-related protein 2/3 complex and is localized within lamellipodia. Cortactin is a substrate for Src and other protein tyrosine kinases involved in cell motility, where its phosphorylation on tyrosines 421, 466, and 482 in the carboxy terminus is required for cell movement and metastasis. In spite of the importance of cortactin tyrosine phosphorylation in cell motility, little is known regarding the structural, spatial, or signaling requirements regulating cortactin tyrosine phosphorylation. Herein, we report that phosphorylation of cortactin tyrosine residues in the carboxy terminus requires the aminoterminal domain and Rac1-mediated localization to the cell periphery. Phosphorylation-specific antibodies directed against tyrosine 421 and 466 were produced to study the regulation and localization of tyrosine phosphorylated cortactin. Phosphorylation of cortactin tyrosine 421 and 466 was elevated in response to Src, epidermal growth factor receptor and Rac1 activation, and tyrosine 421 phosphorylated cortactin localized with F-actin in lamellipodia and podosomes. Cortactin tyrosine phosphorylation is progressive, with tyrosine 421 phosphorylation required for phosphorylation of tyrosine 466. These results indicate that cortactin tyrosine phosphorylation requires Rac1-induced cortactin targeting to cortical actin networks, where it is tyrosine phosphorylated in hierarchical manner that is closely coordinated with its ability to regulate actin dynamics.
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cortactin interacts with wip in regulating arp2 3 activation and membrane protrusion
Current Biology, 2003Co-Authors: Andrew W. Kinley, Scott A Weed, Andrei V. Karginov, Eric A. Bissonette, Thomas J ParsonsAbstract:Abstract Background: Modulation of actin cytoskeleton assembly is an integral step in many cellular events. A key regulator of actin polymerization is Arp2/3 complex. Cortactin, an F-actin binding protein that localizes to membrane ruffles, is an activator of Arp2/3 complex. Results: A yeast two-hybrid screen revealed the interaction of the cortactin Src homology 3 (SH3) domain with a peptide fragment derived from a cDNA encoding a region of WASp-Interacting Protein (WIP). GST-cortactin interacted with WIP in an SH3-dependent manner. The subcellular localization of cortactin and WIP coincided at the cell periphery. WIP increased the efficiency of cortactin-mediated Arp2/3 complex activation of actin polymerization in a concentration-dependent manner. Lastly, coexpression of cortactin and WIP stimulated membrane protrusions. Conclusions: WIP, a protein involved in filopodia formation, binds to both actin monomers and cortactin. Thus, recruitment of actin monomers to a cortactin-activated Arp2/3 complex likely leads to the observed increase in cortactin activation of Arp2/3 complex by WIP. These data suggest that a cortactin-WIP complex functions in regulating actin-based structures at the cell periphery.
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interaction of cortactin and n wasp with arp2 3 complex
Current Biology, 2002Co-Authors: John E. Heuser, Andrei V. Karginov, Wei Lih Lee, Thomas J ParsonsAbstract:Abstract Background: Dynamic actin assembly is required for diverse cellular processes and often involves activation of Arp2/3 complex. Cortactin and N-WASp activate Arp2/3 complex, alone or in concert. Both cortactin and N-WASp contain an acidic (A) domain that is required for Arp2/3 complex binding. Results: We investigated how cortactin and the constitutively active VCA domain of N-WASp interact with Arp2/3 complex. Structural studies showed that cortactin is a thin, elongated monomer. Chemical crosslinking studies demonstrated selective interaction of the Arp2/3 binding NTA domain of cortactin (cortactin NTA) with the Arp3 subunit and VCA with Arp3, Arp2, and ARPC1/p40. Cortactin NTA and VCA crosslinking to the Arp3 subunit were mutually exclusive; however, cortactin NTA did not inhibit VCA crosslinking to Arp2 or ARPC1/p40, nor did it inhibit activation of Arp2/3 complex by VCA. We conducted an experiment in which a saturating concentration of cortactin NTA modestly lowered the binding affinity of VCA for Arp2/3; the results of this experiment provided further evidence for ternary complex formation. Consistent with a common binding site on Arp3, a saturating concentration of VCA abolished binding of cortactin to Arp2/3 complex. Conclusions: Under certain circumstances, cortactin and N-WASp can bind simultaneously to Arp2/3 complex, accounting for their synergy in activation of actin assembly. The interaction of cortactin NTA with Arp2/3 complex does not inhibit Arp2/3 activation by N-WASp, despite competition for a common binding site located on the Arp3 subunit. These results suggest a model in which cortactin may bridge Arp2/3 complex to actin filaments via Arp3 and N-WASp activates Arp2/3 complex by binding Arp2 and/or ARPC1/p40.
Kathrin Doppler - One of the best experts on this subject based on the ideXlab platform.
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complement deposition induced by binding of anti Contactin 1 auto antibodies is modified by immunoglobulins
Experimental Neurology, 2017Co-Authors: Luise Appeltshauser, Andreas Weishaupt, Claudia Sommer, Kathrin DopplerAbstract:Inflammatory neuropathies associated with auto-antibodies against paranodal proteins like Contactin-1 are reported to respond poorly to treatment with intravenous immunoglobulins (IVIG). A reason might be that IVIG interacts with the complement pathway and these auto-antibodies often belong to the IgG4 subclass that does not activate complement. However, some patients do show a response to IVIG, especially at the beginning of the disease. This corresponds with the finding of coexisting IgG subclasses IgG1, IgG2 and IgG3. We therefore aimed to investigate complement deposition and activation by samples of three patients with anti-Contactin-1 IgG auto-antibodies of different subclasses as a potential predictor for response to IVIG. Complement deposition and activation was measured by cell binding and ELISA based assays, and the effect of IVIG on complement deposition was assessed by addition of different concentrations of IVIG. Binding of anti-Contactin-1 auto-antibodies of all three patients induced complement deposition and activation with the strongest effect shown by the serum of a patient with predominance of IgG3 auto-antibodies. IVIG led to a reduction of complement deposition in a dose-dependent manner, but did not reduce binding of auto-antibodies to Contactin-1. We conclude that complement deposition may contribute to the pathophysiology of anti-Contactin-1 associated neuropathy, particularly in patients with predominance of the IgG3 subclass. The proportion of different auto-antibody subclasses may be a predictor for the response to IVIG in patients with auto-antibodies against paranodal proteins.
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Contactin 1 and neurofascin 155 186 are not targets of auto antibodies in multifocal motor neuropathy
PLOS ONE, 2015Co-Authors: Kathrin Doppler, Judy King Man Ng, Luise Appeltshauser, Heidrun H Kramer, Edgar Meinl, Sulayman D Dibhajj, Stephen G Waxman, Peter J. Brophy, Carmen Villmann, Andreas WeishauptAbstract:Multifocal motor neuropathy is an immune mediated disease presenting with multifocal muscle weakness and conduction block. IgM auto-antibodies against the ganglioside GM1 are detectable in about 50% of the patients. Auto-antibodies against the paranodal proteins Contactin-1 and neurofascin-155 and the nodal protein neurofascin-186 have been detected in subgroups of patients with chronic inflammatory demyelinating polyneuropathy. Recently, auto-antibodies against neurofascin-186 and gliomedin were described in more than 60% of patients with multifocal motor neuropathy. In the current study, we aimed to validate this finding, using a combination of different assays for auto-antibody detection. In addition we intended to detect further auto-antibodies against paranodal proteins, specifically Contactin-1 and neurofascin-155 in multifocal motor neuropathy patients’ sera. We analyzed sera of 33 patients with well-characterized multifocal motor neuropathy for IgM or IgG anti-Contactin-1, anti-neurofascin-155 or -186 antibodies using enzyme-linked immunosorbent assay, binding assays with transfected human embryonic kidney 293 cells and murine teased fibers. We did not detect any IgM or IgG auto-antibodies against Contactin-1, neurofascin-155 or -186 in any of our multifocal motor neuropathy patients. We conclude that auto-antibodies against Contactin-1, neurofascin-155 and -186 do not play a relevant role in the pathogenesis in this cohort with multifocal motor neuropathy.
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destruction of paranodal architecture in inflammatory neuropathy with anti Contactin 1 autoantibodies
Journal of Neurology Neurosurgery and Psychiatry, 2015Co-Authors: Kathrin Doppler, Andreas Weishaupt, Luise Appeltshauser, Sulayman D Dibhajj, Stephen G Waxman, Carmen Villmann, Kai Wilhelmi, Mathias Maurer, Claudia SommerAbstract:Objective Autoantibodies against paranodal proteins have been described in patients with inflammatory neuropathies, but their association with pathology of nodes of Ranvier is unclear. We describe the clinical phenotype and histopathological changes of paranodal architecture of patients with autoantibodies against Contactin-1, identified from a cohort with chronic inflammatory demyelinating polyradiculoneuropathy (n=53) and Guillain-Barre syndrome (n=21). Methods We used ELISA to detect autoantibodies against Contactin-1. Specificity of the autoantibodies was confirmed by immunoblot assay, binding to Contactin-1-transfected human embryonic kidney cells, binding to paranodes of murine teased fibres and preabsorption experiments. Paranodal pathology was investigated by immunofluorescence labelling of dermal myelinated fibres. Results High reactivity to Contactin-1 by ELISA was found in four patients with chronic inflammatory demyelinating polyradiculoneuropathy and in none of the patients with Guillain-Barre syndrome, which was confirmed by cell binding assays in all four patients. The four patients presented with a typical clinical picture, namely acute onset of disease and severe motor symptoms, with three patients manifesting action tremor. Immunofluorescence-labelling of paranodal proteins of dermal myelinated fibres revealed disruption of paranodal architecture. Semithin sections showed axonal damage but no classical signs of demyelination. Interpretation We conclude that anti-Contactin-1-related neuropathy constitutes a presumably autoantibody-mediated form of inflammatory neuropathy with distinct clinical symptoms and disruption of paranodal architecture as a pathological correlate. Anti-Contactin-1-associated neuropathy does not meet morphological criteria of demyelinating neuropathy and therefore, might rather be termed a ‘paranodopathy’ rather than a subtype of demyelinating inflammatory neuropathy.