Biomedical subjects

A Faissner

Publications and source records attributed to A Faissner.

At least 19 recordsLinked to original sources

PubMed2004

Differential upregulation of extracellular matrix molecules associated with the appearance of granule cell dispersion and mossy fiber sprouting during epileptogenesis in a murine model of temporal lobe epilepsy.

We have investigated changes in the extracellular matrix of the hippocampus associated with the early progression of epileptogenesis in a murine model of temporal lobe epilepsy using immunohistochemistry. In the first week following intrahippocampal injection of the glutamate agonist, domoate, there is a latent period at the end of which begins a sequential upregulation of extracellular matrix (ECM) molecules in the granule cell layer of the dentate gyrus, beginning with neurocan and tenascin-C. This expression precedes the characteristic dispersion of the granule cell layer which is evident at 14 days post-injection when the first recurrent seizures can be recorded. At this stage, an upregulation of the chondroitin sulfate proteoglycan, phosphacan, the DSD-1 chondroitin sulfate motif, and the HNK-1 oligosaccharide are also observed. The expression of these molecules is localized differentially in the epileptogenic dentate gyrus, especially in the sprouting molecular layer, where a strong upregulation of phosphacan, tenascin-C, and HNK-1 is observed but there is no expression of the proteoglycan, neurocan, nor of the DSD-1 chondroitin sulfate motif. Hence, it appears that granule cell layer dispersion is accompanied by a general increase in the ECM, while mossy fiber sprouting in the molecular layer is associated with a more restricted repertoire. In contrast to these changes, the expression of the ECM glycoproteins, laminin and fibronectin, both of which are frequently implicated in tissue remodelling events, showed no changes associated with either granule cell dispersion or mossy fiber sprouting, indicating that the epileptogenic plasticity of the hippocampus is accompanied by ECM interactions that are characteristic of the CNS.

Animals↗

PubMed2001

Glial tumor cell adhesion is mediated by binding of the FNIII domain of receptor protein tyrosine phosphatase beta (RPTPbeta) to tenascin C.

The extracellular domain of receptor protein tyrosine phosphatase beta (RPTPbeta) is composed of several domains which mediate its interactions with distinct ligands present on the surface of either neurons or glial cells. Here, we demonstrate that the fibronectin type III domain (FNIII) of RPTPbeta binds to glial tumor-derived cell lines and primary astrocytes. We used affinity purification to isolate several proteins that specifically bind to the FNIII domain of RPTPbeta. One of these, a 240 kDa protein that was purified from U118MG glioblastoma cell, was identified as tenascin C based on the amino acid sequence of several tryptic peptides. The interaction of RPTPbeta with tenascin C was found to mediate cell adhesion. Adhesion and spreading of SF763T astrocytoma cells expressing RPTPbeta on tenascin C was specifically abolished by the addition of a soluble fragment containing the FNIII domain of the receptor. RPTPbeta-dependent cell adhesion was mediated by binding to the alternatively spliced FNIII repeats A1,2,4 (TnfnA1,2,4) of tenascin C. Furthermore, COS cells expressing RPTPbeta adhere to TnfnA1,2,4, while the parental cells did not. These results demonstrate that the FNIII domain of RPTPbeta binds to tenascin C and suggest that RPTPbeta present on glial tumor cells is a primary adhesion receptor system to the extracellular matrix.

Animals↗

PubMed2001

Serum tenascin-C is an indicator of inflammatory bowel disease activity.

Tenascin-C is a multifunctional matrix protein that is induced in inflammation and neoplasia. In the colonic mucosa of ulcerative colitis patients tenascin-C indicates tissue repair, and mucosal concentrations are correlated with local disease activity. We prospectively examined the relationship between serum concentrations of tenascin-C parameters of disease activity in surgically treated patients with ulcerative colitis and patients with inflammatory bowel disease (IBD). Perioperative serum concentrations were quantified by ELISA in 58 patients admitted for restorative proctocolectomy; controls were 37 patients with familial adenomatous polyposis receiving the same treatment. We also measured tenascin-C serum levels in 47 patients with ulcerative colitis and Crohn's disease who were receiving nonsurgical treatment. Preoperative serum tenascin-C levels were significantly higher in ulcerative colitis patients than in controls (17.2 +/- 14.6 microg/ml vs. 3.2 +/- 1.7 microg/ml) and were significantly correlated with clinical and histological parameters of disease activity; levels decreased significantly after restorative proctocolectomy. Serum tenascin-C levels were also correlated with the course of disease activity in conservatively treated IBD patients. Tenascin-C is thus not disease-specific. However, it does indicate the activity of IBD and may reflect the degree of tissue remodeling. The tenascin-C levels therefore offers a novel serum parameter for assessing disease activity and monitoring therapy in patients with IBD.

Adolescent↗

PubMed2001

The structure and function of tenascins in the nervous system.

The tenascins are a family of large extracellular matrix glycoproteins that comprise five known members. Three of these, tenascin-C (TN-C) tenascin-R (TN-R) and tenascin-Y (TN-Y) are expressed in specific patterns during nervous system development and are down-regulated after maturation. The expression of TN-C, the best studied member of the family, persists in restricted areas of the nervous system that exhibit neuronal plasticity and is reexpressed after lesion. Numerous studies in vitro suggest specific roles for tenascins in the nervous system involving precursor cell migration, axon growth and guidance. TN-C has been shown to occur in a large number of isoform variants generated by combinatorial variation of alternatively spliced fibronectin type III (FNIII) repeats. This finding indicates that TN-C might specify neural microenvironments, a hypothesis supported by recent analysis of TN-C knockout animals, which has begun to reveal subtle nervous system dysfunctions.

Alternative Splicing↗

PubMed2001

Knockout mice reveal a contribution of the extracellular matrix molecule tenascin-C to neural precursor proliferation and migration.

The extracellular matrix glycoprotein tenascin-C is widely expressed in the vertebrate central nervous system (CNS) during development and repair. Despite multiple effects of tenascin-C on cell behaviour in culture, no structural abnormalities of the CNS and other organs have been found in adult tenascin-C-null mice, raising the question of whether this glycoprotein has a significant role in vivo. Using a transgenic approach, we have demonstrated that tenascin-C regulates both cell proliferation and migration in oligodendrocyte precursors during development. Knockout mice show increased rates of oligodendrocyte precursor migration along the optic nerve and reduced rates of oligodendrocyte precursor proliferation in different regions of the CNS. Levels of programmed cell death were reduced in areas of myelination at later developmental stages, providing a potential corrective mechanism for any reduction in cell numbers that resulted from the proliferation phenotype. The effects on cell proliferation are mediated via the alphavbeta3 integrin and an interaction with the platelet-derived growth factor-stimulated mitogenic pathway, emphasising the importance of both CNS extracellular matrix and integrin growth factor interactions in the regulation of neural precursor behaviour.

Animals↗

PubMed2001

Tenascin glycoproteins and the complementary ligand DSD-1-PG/ phosphacan--structuring the neural extracellular matrix during development and repair.

The differentiation and morphogenesis of neural tissues involves a diversity of interactions between neural cells and their environment. Many potentially important interactions occur with the extracellular matrix (ECM), a complex association of extracellular molecules organised into aggregates and polymers. The large modular glycoprotein, Tenascin-C, and the chondroitin sulphate proteoglycan, DSD-1-PG/Phosphacan, have complex and frequently overlapping expression patterns in the developing CNS. Their presence in zones of cell proliferation, migration, and differentiation, as well as in boundary structures, suggest that they may be involved in the modulation of an extensive range of cellular processes. They are both strongly up-regulated in a range of CNS lesions and pathologies, being components of the glial scar, and expressed by gliomas. Functional roles in many cellular processes are possible through their extensive molecular interaction sites, both with each other, and with many of the same cell surface receptors, adhesion molecules, growth factors and other matrix proteins. These multiple interactions involve sites on both their protein domains and on the heterogeneous carbohydrate groups with which they are post-translationally modified. In vitro assays demonstrate cell-type specific effects on adhesion, migration and the formation and extension of cellular processes, including neurites and axons.

Animals↗

PubMed1999

Comparing astrocytic cell lines that are inhibitory or permissive for axon growth: the major axon-inhibitory proteoglycan is NG2.

Astrocytes, oligodendrocytes, and oligodendrocyte/type 2 astrocyte progenitors (O2A cells) can all produce molecules that inhibit axon regeneration. We have shown previously that inhibition of axon growth by astrocytes involves proteoglycans. To identify inhibitory mechanisms, we created astrocyte cell lines that are permissive or nonpermissive and showed that nonpermissive cells produce inhibitory chondroitin sulfate proteoglycans (CS-PGs). We have now tested these cell lines for the production and inhibitory function of known large CS-PGs. The most inhibitory line, Neu7, produces three CS-PGs in much greater amounts than the other cell lines: NG2, versican, and the CS-56 antigen. The contribution of NG2 to inhibition by the cells was tested using a function-blocking antibody. This allowed increased growth of dorsal root ganglion (DRG) axons over Neu7 cells and matrix and greatly increased the proportion of cortical axons able to cross from permissive A7 cells onto inhibitory Neu7 cells; CS-56 antibody had a similar effect. Inhibitory fractions of conditioned medium contained NG2 coupled to CS glycosaminoglycan chains, whereas noninhibitory fractions contained NG2 without CS chains. Enzyme preparations that facilitated axon growth in Neu7 cultures were shown to either degrade the NG2 core protein or remove CS chains. Versican is present as patches on Neu7 monolayers, but DRG axons do not avoid these patches. Therefore, NG2 appears to be the major axon-inhibitory factor made by Neu7 astrocytes. In the CNS, NG2 is expressed by O2A cells, which react rapidly after injury to produce a dense NG2-rich network, and by some reactive astrocytes. Our results suggest that NG2 may be a major obstacle to axon regeneration.

Animals↗

PubMed1999

Detection of tenascin-C isoforms in colorectal mucosa, ulcerative colitis, carcinomas and liver metastases.

The glycoprotein tenascin-C is up-regulated in inflammatory and neoplastic diseases. Most available data on tissue tenascin-C content do not distinguish its various isoforms. We have quantified tissue tenascin-C signals in colorectal mucosa, ulcerative colitis, colorectal carcinomas and liver metastases using 5 monoclonal antibodies (MAbs) with different binding sites. Tenascin-C of tissue extracts was analyzed by a standardized Western blot technique and densitometry. As a reference MAb, K8 displayed tenascin-C tissue concentrations of 4.1 +/- 2.3 microgram/mg total protein in normal mucosa, 13.8 +/- 4.7 microgram/mg in ulcerative colitis, 28.8 +/- 14.5 microgram/mg in colorectal carcinomas and 25.6 +/- 8.9 microgram/mg in liver metastases. The optical density values per microgram protein tissue extract of the 5 MAbs reflect the levels of the corresponding tenascin-C epitopes. Various signal intensities indicate a distinct diagnostic usefulness of the MAbs in detecting colorectal carcinomas. The binding characteristics of MAb J1/tn2 point to an under-representation of the TNfnD domain in metastasizing colorectal carcinomas, while MAb 19H12 showed an increased binding rate on the TNfnA1,2,4 region. Our comparative study of tenascin-C in inflammatory and neoplastic diseases of the colon mucosa substantiates the occurrence of large differences in the diagnostic value of tenascin-C MAbs. The detected alterations of tenascin-C in metastasizing colorectal carcinomas might indicate a prognostic value of specific tenascin-C isoforms.

Antibodies, Monoclonal↗

PubMed1999

Chondroitin sulfate E promotes neurite outgrowth of rat embryonic day 18 hippocampal neurons.

In light of controversial reports concerning the effects of chondroitin sulfates on neurite outgrowth, several glycosaminoglycans belonging to this structural class were compared with regard to their influence on axon formation by embryonic day 18 hippocampal neurons. In these studies, chondroitin sulfate A (CS-A), CS-B and CS-C proved weak or inefficient in the neurite outgrowth promotion assay. As expected, CS-D stimulated both the fraction of neurite bearing neurons and the length of their processes. This effect could be neutralized by the monoclonal antibody (mAb) 473HD. In contrast, CS-E enacted a dramatic promotion of neurite outgrowth. This effect persisted in the presence of mAb 473HD, consistent with the observation that this antibody did not react with CS-E in glycosaminoglycan transfer and blotting techniques. We conclude that CSE contains a novel glycosaminoglycan based neurite outgrowth promoting motif, which is distinct from other known activities.

Animals↗

PubMed1999

Evidence for combinatorial variability of tenascin-C isoforms and developmental regulation in the mouse central nervous system.

The extracellular matrix glycoprotein tenascin-C (TN-C) displays a restricted and developmentally regulated distribution in the mouse central nervous system. Defined modules of the molecule have been shown to mediate specific functions, such as neuron migration, neurite outgrowth, cell adhesion, and cell proliferation. The smallest TN-C form contains a stretch of eight fibronectin type III (FNIII) domains, which are common to all TN-C isoforms. Unrestricted and independent alternative splicing of six consecutive FNIII cassettes between the fifth and sixth constitutive FNIII domain bears the potential to generate 64 different combinations that might code for TN-C proteins with subtly different functions. To explore TN-C isoform variability in mouse brain, the alternatively spliced region of TN-C mRNAs was examined by the reverse transcription-polymerase chain reaction technique. Polymerase chain reaction products of uniform size were subcloned and analyzed using domain-specific probes to reveal the expression of particular combinations of alternatively spliced FNIII domains. 27 TN-C isoforms were identified to be expressed in mouse central nervous system, of which 22 are novel. Furthermore, during development, specific TN-C isoforms were found to occur in distinct relative frequencies, as demonstrated for isoforms containing two alternatively spliced FNIII domains. We conclude that TN-C is expressed in a complex and regulated pattern in mouse central nervous system. These findings highlight the potential role of TN-C in mediating specific neuron glia interactions.

Alternative Splicing↗

PubMed1999

DSD-1-proteoglycan is the mouse homolog of phosphacan and displays opposing effects on neurite outgrowth dependent on neuronal lineage.

DSD-1-PG is a chondroitin sulfate proteoglycan (CSPG) expressed by glial cells that can promote neurite outgrowth from rat embryonic mesencephalic (E14) and hippocampal (E18) neurons, an activity that is associated with the CS glycosaminoglycans (GAGs). Further characterization of DSD-1-PG has included sequencing of peptides from the core protein and the cloning of the corresponding cDNA using polyclonal antisera against DSD-1-PG to screen phage expression libraries. On the basis of these studies we have identified DSD-1-PG as the mouse homolog of phosphacan, a neural rat CSPG. Monoclonal antibodies 3H1 and 3F8 against carbohydrate residues on rat phosphacan recognize these epitopes on DSD-1-PG. The epitopes of the antibodies, L2/HNK-1 and L5/Lewis-X, which have been implicated in functional interactions, are also found on DSD-1-PG. Although DSD-1-PG has previously been shown to promote neurite outgrowth, its upregulation after stab wounding of the CNS and its localization in regions that are considered boundaries to axonal extension suggested that it may also have inhibitory functions. Neonatal dorsal root ganglion (DRG) explants grown on a rich supportive substrate (laminin) with and without DSD-1-PG were strikingly inhibited by the proteoglycan. The inhibitory effects of DSD-1-PG on the DRG explants were not relieved by removal of the CS GAGs, indicating that this activity is associated with the core glycoprotein. The neurite outgrowth from embryonic hippocampal neurons on laminin was not affected by the addition of DSD-1-PG. This indicates that DSD-1-PG/mouse phosphacan can have opposing effects on the process of neurite outgrowth dependent on neuronal lineage.

Amino Acid Sequence↗

PubMed1999

Myelination and behaviour of tenascin-C null transgenic mice.

The extracellular matrix glycoprotein tenascin-C is widely expressed during development and repair, making it surprising that few abnormalities have been found in transgenic mice lacking this molecule. We have therefore re-examined the transgenic mice described by Saga et al. [Saga, Y., Yagi, T., Ikawa, Y., Sakakura, T. & Aizawa, S. (1992) Genes Dev., 6 1821-1831] in which tenascin-C was knocked-out by homologous recombination, focusing on two aspects of the nervous system likely to reveal any abnormalities that might follow the loss of tenascin-C. First, we have determined the pattern of myelin and distribution of oligodendrocyte precursor cells in those areas, such as the optic nerve and retina where local concentrations of tenascin-C have been proposed to act as barriers to oligodendrocyte precursor migration and so prevent inappropriate myelination. Secondly, we have examined the behaviour of the mice in a number of well-characterized tests, e.g. beam-walking, passive avoidance and the Morris water maze. We find no abnormalities of myelination or oligodendrocyte precursor distribution in adult mice, showing that local concentrations of tenascin-C are not the sole mechanism responsible for the pattern of myelination in these regions of CNS. However, we do find a number of behavioural abnormalities in these mice and show that hyperlocomotion and deficits in coordination during beam walking can be ascribed to tenascin-C deficiency. The effects on coordination are, however, not seen on a 129 genetic background. Taken together, these results significantly extend the phenotype associated with tenascin-C deficiency but argue against a role in myelination.

Animals↗

PubMed1998

The DSD-1 carbohydrate epitope depends on sulfation, correlates with chondroitin sulfate D motifs, and is sufficient to promote neurite outgrowth.

The neural chondroitin sulfate (CS) proteoglycan (PG) DSD-1-PG was originally identified with the monoclonal antibody (mAb) 473HD. It promotes neurite outgrowth of hippocampal neurons when coated as a substrate in the presence of polycations. This effect is inhibited by mAb 473HD that specifically recognizes the DSD-1 epitope. The DSD-1 epitope is also detectable in CS-C and CS-D preparations from shark cartilage but not in other chondroitin sulfates that are structurally related and differ in their sulfation patterns. Non-sulfated DSD-1-PG and chemically desulfated CS-D were not recognized by mAb 473HD, suggesting that the DSD-1 epitope depends on sulfation. It was possible to enrich DSD-1 epitope-bearing carbohydrates and D disaccharide units from CS-C and CS-D preparations on a mAb 473HD affinity matrix. This indicates that the DSD-1 epitope represents a distinct glycosaminoglycan structure containing D units. The analysis of glycosaminoglycan digestion products by high pressure liquid chromatography revealed that DSD-1-PG preparations contain a unique D disaccharide unit as well as an A, a C, and a non-sulfated disaccharide unit. In neurite outgrowth assays with hippocampal neurons, substrate-bound CS-D promoted neurite outgrowth, whereas CS-A, CS-B, or CS-C did not. This effect of CS-D was inhibited by mAb 473HD. DSD-1 epitope-enriched fractions obtained from CS-D and CS-C promoted neurite outgrowth, whereas CS-C had no such effect prior to enrichment on the mAb 473HD matrix. Based on these findings we conclude that the DSD-1 epitope by itself is sufficient to promote neurite outgrowth and that this activity is possibly associated with D motifs.

Animals↗

PubMed1998

Differential interactions of MAP2, tau and MAP5 during axogenesis in culture.

The subcellular interactions of the neuronal microtubule-associated proteins tau, MAP2 and MAP5 were determined in cultured rat hippocampal neurons using differential detergent extraction and laser scanning microscopy. Axon development correlated with a transition from a MAP2-actin filament interaction to a MAP2-microtubule association and binding of tau to the distal axon. Tau and MAP2 binding specifically increased in the axon and the minor neurites, respectively. No compartment-specific association of MAP5 was observed. Tau binding preceded the accumulation of microtubules at the distal axon which represented a characteristic event during axogenesis. The data provide evidence for a role of MAP2 in regulating microfilament-microtubule interactions during neurite formation and of tau in organizing microtubules at the distal axon.

Animals↗

PubMed1998

Characteristic hexasaccharide sequences in octasaccharides derived from shark cartilage chondroitin sulfate D with a neurite outgrowth promoting activity.

A mouse brain chondroitin sulfate (CS) proteoglycan, DSD-1-PG, bears the DSD-1 epitope and has neurite outgrowth promoting properties. Shark cartilage CS-C inhibits the interactions between the DSD-1-specific monoclonal antibody 473HD and the CS chains of the DSD-1-PG, which is expressed on the mouse glial cells (Faissner, A., Clement, A., Lochter, A., Streit, A., Mandl, C., and Schachner, M. (1994) J. Cell Biol. 126, 783-799). On the other hand, several hexasaccharides isolated from commercial shark cartilage CS-D, which contains a higher proportion of characteristic D units (GlcUA(2-sulfate)beta1-3GalNAc(6-sulfate)) as compared with CS-C, has the A-D tetrasaccharide sequence composed of an A disaccharide unit (GlcUAbeta1-3GalNAc(4-sulfate)) and a D disaccharide unit (Nadanaka, S. and Sugahara, K. (1997) Glycobiology 7, 253-263). In this study, the biological activities and the structure of shark cartilage CS-D were investigated. CS-D inhibited the interactions between monoclonal antibody 473HD and DSD-1-PG and also promoted neurite outgrowth of embryonic day 18 hippocampal neurons. Eight octasaccharide fractions were isolated from CS-D after partial digestion with bacterial chondroitinase ABC by means of gel filtration chromatography and anion-exchange high performance liquid chromotography to investigate the frequency and the arrangement of the A-D tetrasaccharide unit in the polymer sequence. Structural analysis performed by a combination of enzymatic digestions with 500-MHz 1H NMR spectroscopy demonstrated that the isolated octasaccharides shared the common core structure DeltaHexAalpha1-3GalNAcbeta1-4(GlcUAbeta1-3GalNAc)3 with four, five, and six sulfate esters at various hydroxyl groups in different combinations. In the structure, DeltaHexA and GlcUA represent 4-deoxy-alpha-L-threo-hex-4-enepyranosyluronic acid and glucuronic acid, respectively. No D-D tetrasaccharide sequence was found, and discrete D disaccharide units were demonstrated exclusively as A-D tetrasaccharide units in either an A-D-A or an A-D-C hexasaccharide sequence in the five octasaccharides that represented about 5.0% (w/w) of the starting polysaccharides (C denotes the disaccharide GlcUAbeta1-3GalNAc(6-sulfate)). It remains to be determined whether such characteristic hexasaccharide sequences present in shark cartilage CS-D serve as functional domain structures recognized by some protein ligands.

Animals↗

PubMed1998

Mucosal tenascin C content in inflammatory and neoplastic diseases of the large bowel.

PURPOSE: Tenascin C is a glycoprotein of the extracellular matrix. It is upregulated during embryologic development, wound healing, and under conditions of normal and neoplastic growth. Most available data on tenascin C expression in tissues is based on immunohistologic studies. The present study was designed to quantify tissue concentrations in patients with inflammatory and neoplastic diseases of the large bowel. METHODS: Fifty patients with ulcerative colitis, 19 patients suffering from familiar adenomatous polyposis without malignant transformation, and 69 patients with colorectal carcinoma were investigated. Tenascin C concentrations in tissue extracts were determined by semiquantitative Western blotting. RESULTS: The tenascin C tissue concentration of normal mucosa was 2.6 +/- 3.4 microg/mg (n = 55), 2.9 +/- 2.1 microg/mg in colorectal adenomas (n = 19), 7.5 +/- 4.7 microg/mg in ulcerative colitis (n = 50), and 18 +/- 15 microg/mg in colorectal carcinomas (n = 69; mean +/- standard deviation). In ulcerative colitis, the mucosal tenascin C content correlated with histopathologic disease activity. No differences were found between subgroups of adenomas or carcinomas. CONCLUSIONS: Tenascin C tissue concentrations were not altered in adenomas, slightly elevated in ulcerative colitis, and substantially increased in colorectal carcinomas. Although less useful as a diagnostic parameter, tenascin C tissue levels serve as an instrument for assessing the activity of stromal remodeling in large-bowel diseases generally. Specifically, they may reflect disease activity in ulcerative colitis.

Adenomatous Polyposis Coli↗

PubMed1998

Expression of DSD-1-PG in primary neural and glial-derived cell line cultures, upregulation by TGF-beta, and implications for cell-substrate interactions of the glial cell line Oli-neu.

DSD-1-PG is a chondroitin sulfate proteoglycan with neurite-outgrowth promoting properties expressed during development and upon lesion of neural tissues which has been defined with the specific monoclonal antibody 473HD. Double immunofluorescence studies performed on primary cerebellar cultures document that the proteoglycan is expressed on the surface of immature glial cells and the neural cell line Oli-neu, a model of mouse oligodendrocyte progenitors. Biochemical and immunoprecipitation studies performed with biosynthetically labelled Oli-neu and primary neural cells demonstrated that DSD-1-PG is expressed in vitro as a proteoglycan of 1000 kD apparent Mr with two core glycoproteins of 250 kD and 400 kD. In order to study the regulation of DSD-1-PG expression, an in vitro enzyme-linked immunosorbent assay based on Oli-neu and mAb 473HD was established. TGF-beta1-3 induced up-regulation of the proteoglycan, while various growth factors and cytokines did not significantly affect DSD-1-PG expression in both the supernatant and the extract of the culture monolayer. FACSCAN analysis suggested that the proteoglycan is upregulated on the surface of Oli-neu. Cell substrate adhesion assays revealed that this enhanced expression correlates with a selective reduction of adhesion to laminin, but not fibronectin or merosin, which could specifically be neutralized by antibodies to DSD-1-PG. We conclude that the proteoglycan contributes to the regulation of glial precursor interactions with the extracellular matrix.

Aggrecans↗

PubMed1997

Mapping of a defined neurocan binding site to distinct domains of tenascin-C.

Neurocan is a member of the aggrecan family of proteoglycans which are characterized by NH2-terminal domains binding hyaluronan, and COOH-terminal domains containing C-type lectin-like modules. To detect and enhance the affinity for complementary ligands of neurocan, the COOH-terminal neurocan domain was fused with the NH2-terminal region of tenascin-C, which contains the hexamerization domain of this extracellular matrix glycoprotein. The fusion protein was designed to contain the last downstream glycosaminoglycan attachment site and was expressed as a proteoglycan. In ligand overlay blots carried out with brain extracts, it recognized tenascin-C. The interaction was abolished by the addition of EDTA, or TNfn4,5, a bacterially expressed tenascin-C fragment comprising the fourth and fifth fibronectin type III module. The fusion protein directly reacted with this fragment in ligand blot and enzyme-linked immunosorbent assay procedures. Both tenascin-C and TNfn4,5 were retained on Sepharose 4B-linked carboxyl-terminal neurocan domains, which in BIAcore binding studies yielded a KD value of 17 nM for purified tenascin-C. We conclude that a divalent cation-dependent interaction between the COOH-terminal domain of neurocan and those fibronectin type III repeats is substantially involved in the binding of neurocan to tenascin-C.

Amino Acid Sequence↗