| 11. |
- Dours-Zimmermann, Maria T., et al.
(författare)
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Versican V2 Assembles the Extracellular Matrix Surrounding the Nodes of Ranvier in the CNS
- 2009
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Ingår i: The Journal of Neuroscience. - 1529-2401. ; 29:24, s. 7731-7742
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Tidskriftsartikel (refereegranskat)abstract
- The CNS-restricted versican splice-variant V2 is a large chondroitin sulfate proteoglycan incorporated in the extracellular matrix surrounding myelinated fibers and particularly accumulating at nodes of Ranvier. In vitro, it is a potent inhibitor of axonal growth and therefore considered to participate in the reduction of structural plasticity connected to myelination. To study the role of versican V2 during postnatal development, we designed a novel isoform-specific gene inactivation approach circumventing early embryonic lethality of the complete knock-out and preventing compensation by the remaining versican splice variants. These mice are viable and fertile; however, they display major molecular alterations at the nodes of Ranvier. While the clustering of nodal sodium channels and paranodal structures appear in versican V2-deficient mice unaffected, the formation of the extracellular matrix surrounding the nodes is largely impaired. The conjoint loss of tenascin-R and phosphacan from the perinodal matrix provide strong evidence that versican V2, possibly controlled by a nodal receptor, organizes the extracellular matrix assembly in vivo.
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| 12. |
- Feng, Kang, et al.
(författare)
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All four members of the Ten-m/Odz family of transmembrane proteins form dimers.
- 2002
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 277:29, s. 26128-26135
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Tidskriftsartikel (refereegranskat)abstract
- Ten-m/Odz/teneurins are a new family of four distinct type II transmembrane molecules. Their extracellular domains are composed of an array of eight consecutive EGF modules followed by a large globular domain. Two of the eight modules contain only 5 instead of the typical 6 cysteine residues and have the capability to dimerize in a covalent, disulfide-linked fashion. The structural properties of the extracellular domains of all four mouse Ten-m proteins have been analyzed using secreted, recombinant molecules produced by mammalian HEK-293 cells. Electron microscopic analysis supported by analytical ultracentrifugation data revealed that the recombinant extracellular domains of all Ten-m proteins formed homodimers. SDS-PAGE analysis under nonreducing conditions as well as negative staining after partial denaturation of the molecules indicated that the globular COOH-terminal domains of Ten-m1 and -m4 contained subdomains with a pronounced stability against denaturing agents, especially when compared with the homologous domains of Ten-m2 and -m3. Cotransfection experiments of mammalian cells with two different extracellular domains revealed that Ten-m molecules have also the ability to form heterodimers, a property that, combined with alternative splicing events, allows the formation of a multitude of molecules with different characteristics from a limited set of genes.
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| 13. |
- Geissler, Maren, et al.
(författare)
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Primary hippocampal neurons, which lack four crucial extracellular matrix molecules, display abnormalities of synaptic structure and function and severe deficits in perineuronal net formation.
- 2013
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Ingår i: The Journal of Neuroscience. - 1529-2401. ; 33:18, s. 7742-7742
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Tidskriftsartikel (refereegranskat)abstract
- The extracellular matrix (ECM) of the brain plays crucial roles during the development, maturation, and regeneration of the CNS. In a subpopulation of neurons, the ECM condenses to superstructures called perineuronal nets (PNNs) that surround synapses. Camillo Golgi described PNNs a century ago, yet their biological functions remain elusive. Here, we studied a mouse mutant that lacks four ECM components highly enriched in the developing brain: the glycoproteins tenascin-C and tenascin-R and the chondroitin sulfate proteoglycans brevican and neurocan. Primary embryonic hippocampal neurons and astrocytes were cultivated using a cell insert system that allows for co-culture of distinct cell populations in the absence of direct membrane contacts. The wild-type and knock-out cells were combined in the four possible permutations. Using this approach, neurons cultivated in the presence of mutant astrocytes displayed a transient increase of synapses after 2 weeks. However, after a period of 3 weeks or longer, synapse formation and stabilization were compromised when either neuron or astrocyte cell populations or both were of mutant origin. The development of PNN structures was observed, but their size was substantially reduced on knock-out neurons. The synaptic activity of both wild-type and knock-out neurons was monitored using whole-cell patch clamping. The salient observation was a reduced frequency of IPSCs and EPSCs, whereas the amplitudes were not modified. Remarkably, the knock-out neuron phenotypes could not be rescued by wild-type astrocytes. We conclude that the elimination of four ECM genes compromises neuronal function.
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| 14. |
- Kappler, J, et al.
(författare)
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Tenascins are associated with lipid rafts isolated from mouse brain
- 2002
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Ingår i: Biochemical and Biophysical Research Communications. - 1090-2104. ; 294:3, s. 742-747
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Tidskriftsartikel (refereegranskat)abstract
- Lipid rafts are microdomains of the plasma membrane which are enriched in glycosphingolipids and specific proteins. The reported interactions of several raft-associated proteins (such as, e.g., F3) with tenascin C and tenascin R prompted us to consider that these oligomeric multidomain glycoproteins of the extracellular matrix (ECM) could associate with rafts. Here, we show punctate immunocytochemical distributions of tenascin C (TN-C) and tenascin R (TN-R) at the membrane surface of neural cells resembling the pattern reported for raft-associated proteins. Moreover, cholesterol depletion with methyl-beta-cyclodextrin reduced the punctate surface staining of TN-C. Consistently, TN-C was associated with lipid rafts of neonatal mouse brain according to sucrose density gradient centrifugation experiments. Furthermore, TN-R was also found in rafts prepared from myelin of adult mice. Thus, brain-derived tenascins are able to associate with lipid rafts. (C) 2002 Elsevier Science (USA). All rights reserved.
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| 15. |
- Kappler, Joachim, et al.
(författare)
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Transport of a hyaluronan-binding protein in brain tissue
- 2009
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Ingår i: Matrix Biology. - : Elsevier BV. - 1569-1802 .- 0945-053X. ; 28:7, s. 396-405
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Tidskriftsartikel (refereegranskat)abstract
- Hyaluronan is an unsulfated linear glycosaminoglycan with the ability to nucleate extracellular matrices by the formation of aggregates with lecticans. These matrices are essential during development of the central nervous system. In the prospective white matter of the developing brain hyaluronan is organized into fiber-like structures according to confocal microscopy of fixed slices which may guide the migration of neural precursor cells [Baier, C., S.L Baader, J. Jankowski, V. Gieselmann, K. Schilling, U. Rauch, and J. Kappler. 2007. Hyaluronan is organized into fiber-like structures along migratory pathways in the developing mouse cerebellum. Matrix Biol. 26: 348-58]. By using plasmon surface resonance, microinjection into brain slices and fluorescence correlation spectroscopy, we show that the brain-specific lecticans bind to, but also dissociate rather rapidly from hyaluronan. After microinjection into native cerebellar slices a GFP-tagged hyaluronan-binding neurocan fragment was enriched at binding sites in the prospective white matter, which had a directional orientation and formed local stationary concentration gradients in areas where binding sites are abundant. Fluorescence correlation spectroscopy measurements at fixed brain slices revealed that fiber-bound neurocan-GFP was mobile with Dfiber(neurocan-GFP) = 4 x 10(-10) cm(2)/s. Therefore, we propose that hyaluronan-rich fibers in the prospective white matter of the developing mouse cerebellum can guide the diffusion of lecticans. Since lecticans bind a variety of growth and mobility factors, their guided diffusion may contribute to the transport of these polypeptides and to the formation of concentration gradients. This mechanism could serve to encode positional information during development. (C) 2009 Elsevier B.V. All rights reserved.
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| 16. |
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| 17. |
- Murugesan, Vignesh, et al.
(författare)
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β-Sarcoglycan Deficiency Reduces Atherosclerotic Plaque Development in ApoE-Null Mice
- 2017
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Ingår i: Journal of Vascular Research. - : S. Karger AG. - 1423-0135 .- 1018-1172. ; 54, s. 235-245
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Tidskriftsartikel (refereegranskat)abstract
- Background: Smooth muscle cells are important for atheroscleroticplaque stability. Their proper ability to communicatewith the extracellular matrix is crucial for maintainingthe correct tissue integrity. In this study, we have investigatedthe role of β-sarcoglycan within the matrix-binding dystrophin-glycoproteincomplex in the development of atherosclerosis.Results: Atherosclerotic plaque developmentwas significantly reduced in ApoE-deficient mice lackingβ-sarcoglycan, and their plaques contained an increase indifferentiated smooth muscle cells. ApoE-deficient micelacking β-sarcoglycan showed a reduction in ovarian adiposetissue and adipocyte size, while the total weight of theanimals was not significantly different. Western blot analysisof adipose tissues showed a decreased activation of proteinkinase B, while that of AMP-activated kinase was increasedin mice lacking β-sarcoglycan. Analysis of plasma in β-sarcoglycan-deficientmice revealed reduced levels of leptin,adiponectin, insulin, cholesterol, and triglycerides but in-creased levels of IL-6, IL-17, and TNF-α. Conclusions: Our resultsindicate that the dystrophin-glycoprotein complex andβ-sarcoglycan can affect the atherosclerotic process. Furthermore,the results show the effects of β-sarcoglycan deficiencyon adipose tissue and lipid metabolism, which mayalso have contributed to the atherosclerotic plaque reduction.
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| 18. |
- Oohashi, T, et al.
(författare)
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Bral1, a brain-specific link protein, colocalizing with the versican V2 isoform at the nodes of Ranvier in developing and adult, mouse central nervous systems
- 2002
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Ingår i: Molecular and Cellular Neuroscience. - : Elsevier BV. - 1044-7431. ; 19:1, s. 43-57
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Tidskriftsartikel (refereegranskat)abstract
- Bral1, a brain-specific hyaluronan-binding protein, has been cloned recently. To gain insight into the role of Bral1, we generated a specific antibody against this protein. We have examined the detailed localization pattern of Bral1 protein and compared it with that of other members of the lectican proteoglycan family, such as brevican and versican, with which Bral1 is predicted to interact. The immunoreactivity of Bral1 antibody was predominantly observed in myelinated fiber tracts in the adult brain and could be detected at P20 in the white matter of the developing cerebellum, suggesting that expression starts when axonal myelination takes place. Furthermore, immunostaining demonstrated that Bral1 colocalized with the versican V2 isoform at the nodes of Ranvier. The present data suggest that Bral1 may play a pivotal role in the formation of the hyaluronan-associated matrix in the CNS that facilitates neuronal conduction by forming an ion diffusion barrier at the nodes.
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| 19. |
- Oohashi, T, et al.
(författare)
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Mouse ten-m/Odz is a new family of dimeric type II transmembrane proteins expressed in many tissues
- 1999
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Ingår i: Journal of Cell Biology. - 0021-9525. ; 145:3, s. 563-577
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Tidskriftsartikel (refereegranskat)abstract
- The Drosophila gene ten-m/odz is the only pair rule gene identified to date which is not a transcription factor. In an attempt to analyze the structure and the function of ten-m/odz in mouse, we isolated four murine ten-m cDNAs which code for proteins of 2,700-2, 800 amino acids. All four proteins (Ten-m1-4) lack signal peptides at the NH2 terminus, but contain a short hydrophobic domain characteristic of transmembrane proteins, 300-400 amino acids after the NH2 terminus. About 200 amino acids COOH-terminal to this hydrophobic region are eight consecutive EGF-like domains. Cell transfection, biochemical, and electronmicroscopic studies suggest that Ten-m1 is a dimeric type II transmembrane protein. Expression of fusion proteins composed of the NH2-terminal and hydrophobic domain of ten-m1 attached to the alkaline phosphatase reporter gene resulted in membrane-associated staining of the alkaline phosphatase. Electronmicroscopic and electrophoretic analysis of a secreted form of the extracellular domain of Ten-m1 showed that Ten-m1 is a disulfide-linked dimer and that the dimerization is mediated by EGF-like modules 2 and 5 which contain an odd number of cysteines. Northern blot and immunohistochemical analyses revealed widespread expression of mouse ten-m genes, with most prominent expression in brain. All four ten-m genes can be expressed in variously spliced mRNA isoforms. The extracellular domain of Ten-m1 fused to an alkaline phosphatase reporter bound to specific regions in many tissues which were partially overlapping with the Ten-m1 immunostaining. Far Western assays and electronmicroscopy demonstrated that Ten-m1 can bind to itself.
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| 20. |
- Pacharra, Sandra, et al.
(författare)
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The Lecticans of Mammalian Brain Perineural Net Are O-Mannosylated
- 2013
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Ingår i: Journal of Proteome Research. - : American Chemical Society (ACS). - 1535-3893 .- 1535-3907. ; 12:4, s. 1764-1771
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Tidskriftsartikel (refereegranskat)abstract
- O-Mannosylation is an important protein modification in brain. During the last years, a few mammalian proteins have been identified as targets of the protein-O-mannosyltransferases 1 and 2. However, these still cannot explain the high content of O-mannosyl glycans in brain and the strong brain involvement of congenital muscular dystrophies caused by POMT mutations (Walker-Warburg syndrome, dystroglycanopathies). By fractionating and analyzing the glycoproteome of mouse and calf brain lysates, we could show that proteins of the perineural net, the lecticans, are O-mannosylated, indicating that major components of neuronal extracellular matrix are O-mannosylated in mammalian brain. This finding corresponds with the high content of O-mannosyl glycans in brain as well as with the brain involvement of dystroglycanopathies. In contrast, the lectican neurocan is not O-mannosylated when recombinantly expressed in EBNA-293 cells, revealing the possibility of different control mechanisms for the initiation of O-mannosylation in different cell types.
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