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R U Margolis

Publications and source records attributed to R U Margolis.

At least 37 records · Page 2Linked to original sources
PubMed1996

Neurocan and phosphacan: two major nervous tissue-specific chondroitin sulfate proteoglycans.

Neurocan is a multidomain hyaluronan-binding chondroitin sulfate proteoglycan that is synthesized by neurons, whereas the astroglial proteoglycan phosphacan is an mRNA splice variant representing the entire extracellular portion of a receptor-type protein tyrosine phosphatase. A glycoform of phosphocan (phosphocan-KS) that contains both chondroitin sulfate and keratan sulfate is present in the postnatal rat central nervous system (CNS). The concentration of neurocan in brain increases during late embryonic development but then declines steeply during the early postnatal period together with hyaluronan, and neurocan also undergoes extensive proteolytic processing during the course of brain development. In contrast, the concentrations of both phosphocan and phosphocan-KS rise steadily after embryonic day 20 to reach a plateau at about 2 weeks postnatally. In the embryonic CNS the distribution of neurocan mRNA is more widespread than that of phosphocan, which is primarily present in regions of active cell proliferation. Neurocan mRNA is also present in areas where the proteoglycan is not expressed, and there is evidence that the short open reading frame in its 5'-leader may function as a cis-acting regulatory signal for the modulation of neurocan expression in the developing CNS. Neurocan and phosphocan bind saturably, reversibly, and with high affinity to neural cell adhesion molecules (Ng-CAM/L1, NCAM, TAG-1/axonin-1) and to tenascin-C. The proteoglycans and their ligands have overlapping localizations in the CNS, and binding of phosphocan to Ng-CAM/L1, NCAM, and tenascin-C is mediated by complex-type N-linked oligosaccharides on the proteoglycan. Neurocan and phosphocan also bind to neurons and are potent inhibitors of neuronal and glial adhesion and neurite outgrowth. Through their interactions with neural cell adhesion and extracellular matrix molecules, these proteoglycans may play a major role in modulating cell adhesion, neurite growth, and signal transduction across the plasma membrane during the development of the CNS.

Aging↗
PubMed1995

Complex-type asparagine-linked oligosaccharides on phosphacan and protein-tyrosine phosphatase-zeta/beta mediate their binding to neural cell adhesion molecules and tenascin.

Phosphacan, a soluble nervous tissue-specific chondroitin sulfate proteoglycan, is an alternative splicing product representing the entire extracellular domain of a transmembrane receptor-type protein-tyrosine phosphatase (RPTP zeta/beta) that also occurs as a chondroitin sulfate proteoglycan in brain. We have previously demonstrated that phosphacan binds with high affinity to neural cell adhesion molecules (Ng-CAM/L1 and N-CAM) and to the extracellular matrix protein tenascin and that it is a potent inhibitor of cell adhesion and neurite outgrowth. Tryptic digests of 125I-labeled phosphacan contain two glycopeptides that bind to Ng-CAM/L1, N-CAM, and tenascin. The larger of these (17 kDa) begins at Gln-209 near the end of the carbonic anhydrase-like domain of phosphacan/RPTP zeta/beta, whereas a 13-kDa glycopeptide begins at His-361 located in the middle of the fibronectin type III-like domain. Treatment of phosphacan with peptide N-glycosidase under nondenaturing conditions reduced its binding the neural cell adhesion molecules and tenascin by 65-75%, whereas endo-beta-N-acetylglucosaminidase H had no effect, and peptide N-glycosidase treatment both decreased the molecular sizes of the tryptic peptides to congruent to 11 kDa and abolished their binding. Based on the amino acid sequence of phosphacan, it can be concluded that each of the tryptic peptides contains one potential N-glycosylation site (at Asn-232 and Asn-381), and analyses of the isolated glycopeptides demonstrated the presence of sialylated complex-type oligosaccharides. Our results therefore indicate that the interactions of phosphacan/RPTP zeta/beta with neural cell adhesion molecules and tenascin are mediated by asparagine-linked oligosaccharides present in their carbonic anhydrase- and fibronectin type III-like domains.

Amino Acid Sequence↗
PubMed1995

The Alzheimer amyloid precursor proteoglycan (appican) is present in brain and is produced by astrocytes but not by neurons in primary neural cultures.

Recent studies showed that the Alzheimer amyloid precursor (APP) occurs as the core protein of a chondroitin sulfate proteoglycan (appican) in C6 glioma cells. In the present study we show that appican is present in both human and rat brain tissue. Cortical rat brain cell cultures were used to identify appican-producing cells. Soluble secreted and cell-associated appican was produced by mixed glial cultures but not by primary neuronal cultures. Among the three major glial cell types, astrocytes produced high levels of appican, while oligodendrocytes failed to produce any. Only low levels of this molecule were occasionally detected in microglial cultures. Expression of appican in astrocyte cultures was regulated by the composition of the growth media. N2a neuroblastoma cells also produced appican; however, treatment with dibutyryl cAMP which promotes neuronal differentiation in these cells inhibited its production without inhibiting synthesis of APP. In contrast to the restricted expression of appican, APP was present in all cultures, and its production was independent of appican synthesis. Neuronal cultures produced mainly APP695 while glial cultures produced the Kunitz type protease inhibitor containing APP. The astrocyte-specific expression of appican suggests a function distinct from the function of APP. Brain appicans may play a role in the development of Alzheimer disease neuropathology.

Amyloid beta-Protein Precursor↗
PubMed1995

Chondroitin sulfate and chondroitin/keratan sulfate proteoglycans of nervous tissue: developmental changes of neurocan and phosphacan.

We have studied developmental changes in the structure and concentration of the hyaluronic acid-binding proteoglycan, neurocan, and of phosphacan, another major chondroitin sulfate proteoglycan of nervous tissue that represents the extracellular domain of a receptor-type protein tyrosine phosphatase. A new monoclonal antibody (designated 1F6), which recognizes an epitope in the N-terminal portion of neurocan, has been used for the isolation of proteolytic processing fragments that occur together with link protein in a complex with hyaluronic acid. Both link protein and two of the neurocan fragments were identified by amino acid sequencing. The N-terminal fragments of neurocan are also recognized by monoclonal antibodies (5C4, 8A4, and 3B1) to epitopes in the G1 and G2 domains of aggrecan and/or in the hyaluronic acid-binding domain of link protein. The presence in brain of these N-terminal fragments is consistent with the developmentally regulated appearance of the C-terminal half of neurocan, which we described previously. We have also used a slot-blot radioimmunoassay to determine the concentrations of neurocan and phosphacan in developing brain. The levels of both proteoglycans increased rapidly during early brain development, but whereas neurocan reached a peak at approximately postnatal day 4 and then declined to below embryonic levels in adult brain, the concentration of phosphacan remained essentially unchanged after postnatal day 12. Keratan sulfate on phosphacan-KS (a glycoform that contains both chondroitin sulfate and keratan sulfate chains) was not detectable until just before birth, and its peak concentration (at 3 weeks postnatal) was reached approximately 1 week later than that of the phosphacan core protein. Immunocytochemical studies using monoclonal antibodies to keratan sulfate (3H1 and 5D4) together with specific glycosidases (endo-beta-galactosidase, keratanase, and keratanase II) also showed that with the exception of some very localized areas, keratan sulfate is generally not present in the embryonic rat CNS.

Aging↗
PubMed1995

Nucleotide sequence and molecular variants of rat receptor-type protein tyrosine phosphatase-zeta/beta.

We have previously described the cloning of phosphacan, a chondroitin sulfate proteoglycan of nervous tissue which interacts with neurons, glia, neural cell adhesion molecules, and tenascin, and represents the extracellular domain of a receptor-type protein tyrosine phosphatase. We now report the complete cDNA and deduced amino acid sequences of the rat transmembrane phosphatase, and demonstrate that the phosphatase and the extracellular proteoglycan have different 3'-untranslated regions. Northern analysis showed three probable splice variants, comprising the extracellular proteoglycan (phosphacan) and long and short forms of the transmembrane phosphatase. PCR studies of rat genomic DNA indicated that there are no introns at the putative 5' and 3' splice sites or in the 2.6 kb segment which is deleted in the short transmembrane protein. Using variant-specific riboprobes corresponding to sequences in the 3'-untranslated region of phosphacan and in the first or second phosphatase domains of the transmembrane protein, in situ hybridization histochemistry of embryonic rat brain and spinal cord and early postnatal cerebellum demonstrated identical localizations of phosphacan and phosphatase mRNAs.

Alternative Splicing↗
PubMed1994

Interactions with tenascin and differential effects on cell adhesion of neurocan and phosphacan, two major chondroitin sulfate proteoglycans of nervous tissue.

We have studied interactions of tenascin with two chondroitin sulfate proteoglycans, neurocan and phosphacan. Neurocan is a multi-domain proteoglycan with a 136-kDa core protein that is synthesized by neurons and binds to hyaluronic acid, whereas the 173-kDa core protein of phosphacan, which is synthesized by glia, represents an extracellular variant of the receptor-type protein tyrosine phosphatase RPTP zeta/beta. Keratan sulfate-containing glycoforms of phosphacan (designated phosphacan-KS) are also present in brain. Immunocytochemical studies of early postnatal rat cerebellum demonstrated that the localization of neurocan, phosphacan, and phosphacan-KS all overlap extensively with that of tenascin, an extracellular matrix protein that modulates cell adhesion and migration. Binding studies using purified proteins covalently attached to fluorescent microbeads demonstrated that proteoglycan-coated beads co-aggregated with differently fluorescing beads coated with tenascin. The co-aggregation was specifically inhibited by Fab' fragments of antibodies against tenascin or the proteoglycans and by soluble neurocan, phosphacan, and tenascin. A solid phase radioligand binding assay confirmed that neurocan, phosphacan, and phosphacan-KS bind to tenascin but not to laminin and fibronectin. Chondroitinase treatment of the proteoglycans or addition of free chondroitin sulfate had no significant effect, indicating that the binding activity is mediated largely via the core glycoproteins. Scatchard analysis demonstrated high affinity binding of 125I-phosphacan, phosphacan-KS, and neurocan to a single site in tenascin, and neurocan and various glycoforms of phosphacan all inhibited binding of 125I-phosphacan to tenascin. In studies of cell adhesion to proteins adsorbed to Petri dishes, phosphacan inhibited adhesion of C6 glioma cells to tenascin whereas neurocan had no effect. Our results suggest that tenascin binds phosphacan and neurocan in vivo and that interactions between chondroitin sulfate proteoglycans and tenascin may play important roles in nervous tissue histogenesis, possibly by modulating signal transduction across the plasma membrane.

Animals↗
PubMed1994

Phosphacan, a chondroitin sulfate proteoglycan of brain that interacts with neurons and neural cell-adhesion molecules, is an extracellular variant of a receptor-type protein tyrosine phosphatase.

We have identified cDNA clones encoding a chondroitin sulfate proteoglycan of rat brain (previously designated 3F8 and now named phosphacan) that binds to neurons and neural cell-adhesion molecules. A sequence of 1616 amino acids deduced from a 4.8-kb open reading frame contains the N-terminal amino acid sequence of the 3F8 core glycoprotein as well as four internal CNBr, tryptic, and endoproteinase Lys-C peptide sequences from the proteoglycan. The deduced amino acid sequence, beginning with a 24-amino acid signal peptide, reveals an N-terminal domain of 255 amino acids homologous to carbonic anhydrases. The entire amino acid sequence deduced from our cDNA clones corresponds to the extracellular portion of a human receptor-type protein tyrosine phosphatase (RPTP zeta/beta) with which it has 76% identity, and the proteoglycan may represent an mRNA splicing variant of the larger transmembrane protein. RNA analysis demonstrated that a probe to the N-terminal carbonic anhydrase domain of the proteoglycan hybridizes with rat brain mRNA of 9.5, 8.4, and 6.4 kb, whereas probes to the phosphatase domains hybridize with only the 9.5-kb message and with the 6.4-kb message (which corresponds to a previously identified variant of the transmembrane protein in which half of the extracellular domain is deleted). The 30 N-terminal amino acids of the 3H1 chondroitin/keratan sulfate proteoglycan of brain are identical to those of the 3F8 proteoglycan, and six internal tryptic peptide sequences also matched those found in sequenced peptides of the 3F8 proteoglycan and/or amino acid sequences deduced from the cDNA clones. We therefore conclude that the 3H1 chondroitin/keratan sulfate proteoglycan and the 3F8 chondroitin sulfate proteoglycan represent glycosylation and possible extracellular splicing variants of a receptor-type protein tyrosine phosphatase. These proteoglycans may modulate cell interactions and other developmental processes in nervous tissue through heterophilic binding to cell-surface and extracellular matrix molecules, and by competition with ligands of the transmembrane phosphatase.

Alternative Splicing↗
PubMed1994

Nervous tissue proteoglycans.

The structure, biosynthesis, localization, and possible functional roles of nervous tissue glycosaminoglycans and proteoglycans were last reviewed several years ago. Since that time, there has been an exponential increase in publications on the neurobiology of proteoglycans. This review will therefore focus on reports which have appeared in the period after 1988, and especially on those concerning the properties of individual characterized nervous tissue proteoglycans. Related areas such as the regulation of glycosaminoglycan biosynthesis and the roles of cell surface proteoglycans in adhesion and growth control are covered in other contributions to this special topic issue.

Amyloid beta-Protein Precursor↗
PubMed1994

Disaccharide composition of heparan sulfates: brain, nervous tissue storage organelles, kidney, and lung.

We have characterized the structural properties of heparan sulfates from brain and other tissues after depolymerization with a mixture of three heparin and heparan sulfate lyases from Flavobacterium heparinum. The resulting disaccharides were separated by HPLC and identified by comparison with authentic standards. In rat, rabbit, and bovine brain, 46-69% of the heparan sulfate disaccharides are N-acetylated and unsulfated, and 17-21% contain a single sulfate residue in the form of a sulfoamino group. In rabbit, bovine, and 1-day postnatal rat brain, disaccharides containing both a sulfated uronic acid and N-sulfate account for an additional 10-14%, together with smaller and approximately equal proportions (5-9%) of mono-, di-, and trisulfated disaccharides having sulfate at the 6-position of the glucosamine residue. Kidney and lung heparan sulfates are distinguished by high concentrations of disaccharides containing 6-sulfated N-acetylglucosamine residues. In chromaffin granules, the catecholamine- and peptide-storing organelles of adrenal medulla, where heparan sulfate accounts for a minor portion (5-10%) of the glycosaminoglycans, we have determined that bovine chromaffin granule membranes contain heparan sulfate in which almost all of the disaccharides are either unsulfated (71%) or monosulfated (18%). In sympathetic nerves, norepinephrine is stored in large dense cored vesicles that in biochemical composition and properties closely resemble adrenal chromaffin granules. However, in contrast to chromaffin granules, heparan sulfate accounts for approximately 75% of the total glycosaminoglycans in large dense-cored vesicles and more closely resembles heparin, insofar as it contains only 21% unsulfated disaccharides, 10% mono- and disulfated disaccharides, and 69% trisulfated disaccharides.(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1994

The neuronal chondroitin sulfate proteoglycan neurocan binds to the neural cell adhesion molecules Ng-CAM/L1/NILE and N-CAM, and inhibits neuronal adhesion and neurite outgrowth.

We have previously shown that aggregation of microbeads coated with N-CAM and Ng-CAM is inhibited by incubation with soluble neurocan, a chondroitin sulfate proteoglycan of brain, suggesting that neurocan binds to these cell adhesion molecules (Grumet, M., A. Flaccus, and R. U. Margolis. 1993. J. Cell Biol. 120:815). To investigate these interactions more directly, we have tested binding of soluble 125I-neurocan to microwells coated with different glycoproteins. Neurocan bound at high levels to Ng-CAM and N-CAM, but little or no binding was detected to myelin-associated glycoprotein, EGF receptor, fibronectin, laminin, and collagen IV. The binding to Ng-CAM and N-CAM was saturable and in each case Scatchard plots indicated a high affinity binding site with a dissociation constant of approximately 1 nM. Binding was significantly reduced after treatment of neurocan with chondroitinase, and free chondroitin sulfate inhibited binding of neurocan to Ng-CAM and N-CAM. These results indicate a role for chondroitin sulfate in this process, although the core glycoprotein also has binding activity. The COOH-terminal half of neurocan was shown to have binding properties essentially identical to those of the full-length proteoglycan. To study the potential biological functions of neurocan, its effects on neuronal adhesion and neurite growth were analyzed. When neurons were incubated on dishes coated with different combinations of neurocan and Ng-CAM, neuronal adhesion and neurite extension were inhibited. Experiments using anti-Ng-CAM antibodies as a substrate also indicate that neurocan has a direct inhibitory effect on neuronal adhesion and neurite growth. Immunoperoxidase staining of tissue sections showed that neurocan, Ng-CAM, and N-CAM are all present at highest concentration in the molecular layer and fiber tracts of developing cerebellum. The overlapping localization in vivo, the molecular binding studies, and the striking effects on neuronal adhesion and neurite growth support the view that neurocan may modulate neuronal adhesion and neurite growth during development by binding to neural cell adhesion molecules.

Aggrecans↗
PubMed1994

Interactions of the chondroitin sulfate proteoglycan phosphacan, the extracellular domain of a receptor-type protein tyrosine phosphatase, with neurons, glia, and neural cell adhesion molecules.

Phosphacan is a chondroitin sulfate proteoglycan produced by glial cells in the central nervous system, and represents the extracellular domain of a receptor-type protein tyrosine phosphatase (RPTP zeta/beta). We previously demonstrated that soluble phosphacan inhibited the aggregation of microbeads coated with N-CAM or Ng-CAM, and have now found that soluble 125I-phosphacan bound reversibly to these neural cell adhesion molecules, but not to a number of other cell surface and extracellular matrix proteins. The binding was saturable, and Scatchard plots indicated a single high affinity binding site with a Kd of approximately 0.1 nM. Binding was reduced by approximately 15% after chondroitinase treatment, and free chondroitin sulfate was only moderately inhibitory, indicating that the phosphacan core glycoprotein accounts for most of the binding activity. Immunocytochemical studies of embryonic rat spinal phosphacan, Ng-CAM, and N-CAM have overlapping distributions. When dissociated neurons were incubated on dishes coated with combinations of phosphacan and Ng-CAM, neuronal adhesion and neurite growth were inhibited. 125I-phosphacan bound to neurons, and the binding was inhibited by antibodies against Ng-CAM and N-CAM, suggesting that these CAMs are major receptors for phosphacan on neurons. C6 glioma cells, which express phosphacan, adhered to dishes coated with Ng-CAM, and low concentrations of phosphacan inhibited adhesion to Ng-CAM but not to laminin and fibronectin. Our studies suggest that by binding to neural cell adhesion molecules, and possibly also by competing for ligands of the transmembrane phosphatase, phosphacan may play a major role in modulating neuronal and glial adhesion, neurite growth, and signal transduction during the development of the central nervous system.

Animals↗
PubMed1994

Immunocytochemical and in situ hybridization studies of the heparan sulfate proteoglycan, glypican, in nervous tissue.

Using immunocytochemistry and in situ hybridization histochemistry, we have investigated in embryonic and postnatal rat nervous tissue the localization and cellular sites of synthesis of glypican, a glycosylphosphatidylinositol-anchored heparan sulfate proteoglycan. Glypican immunoreactivity is present in the marginal layer (prospective white matter) and in the dorsal root entry zone of E13-16 spinal cord, as well as in the optic nerve and retina at this stage, but does not appear at significant levels in brain until approximately E19. The proteoglycan shows a wide distribution in grey matter and axonal projections of postnatal brain, including the hippocampal formation, the parallel fibers of cerebellar granule cells, and in the medulla and brainstem. Northern analysis demonstrated high levels of glypican mRNA in brain and skeletal muscle, and in rat PC12 pheochromocytoma cells. In situ hybridization histochemistry showed that glypican mRNA was especially prominent in cerebellar granule cells, large motor neurons in the brainstem, and CA3 pyramidal cells of the hippocampus. Our immunocytochemical and in situ hybridization results indicate that glypican is predominantly a neuronal membrane proteoglycan in the late embryonic and postnatal rat central nervous system.

Amino Acid Sequence↗
PubMed1993

Nervous tissue proteoglycans.

The structure, biosynthesis, localization, and possible functional roles of nervous tissue glycosaminoglycans and proteoglycans were last reviewed several years ago. Since that time, there has been an exponential increase in publications on the neurobiology of proteoglycans. This review will therefore focus on reports which have appeared in the period after 1988, and especially on those concerning the properties of individual characterized nervous tissue proteoglycans. Related areas such as the regulation of glycosaminoglycan biosynthesis and the roles of cell surface proteoglycans in adhesion and growth control are covered in other contributions to this special topic issue.

Amyloid beta-Peptides↗
PubMed1993

Functional characterization of chondroitin sulfate proteoglycans of brain: interactions with neurons and neural cell adhesion molecules.

Ng-CAM and N-CAM are cell adhesion molecules (CAMs), and each CAM can bind homophilically as demonstrated by the ability of CAM-coated beads (Covaspheres) to self-aggregate. We have found that the extent of aggregation of Covaspheres coated with either Ng-CAM or N-CAM was strongly inhibited by the intact 1D1 and 3F8 chondroitin sulfate proteoglycans of rat brain, and by the core glycoproteins resulting from chondroitinase treatment of the proteoglycans. Much higher concentrations of rat chondrosarcoma chondroitin sulfate proteoglycan (aggrecan) core proteins had no significant effect in these assays. The 1D1 and 3F8 proteoglycans also inhibited binding of neurons to Ng-CAM when mixtures of these proteins were adsorbed to polystyrene dishes. Direct binding of neurons to the proteoglycan core glycoproteins from brain but not from chondrosarcoma was demonstrated using an assay in which cell-substrate contact was initiated by centrifugation, and neuronal binding to the 1D1 proteoglycans was specifically inhibited by the 1D1 monoclonal antibody. Different forms of the 1D1 proteoglycan have been identified in developing and adult brain. The early postnatal form (neurocan) was found to bind neurons more effectively than the adult proteoglycan, which represents the C-terminal half of the larger neurocan core protein. Our results therefore indicate that certain brain proteoglycans can bind to neurons, and that Ng-CAM and N-CAM may be heterophilic ligands for neurocan and the 3F8 proteoglycan. The ability of these brain proteoglycans to inhibit adhesion of cells to CAMs may be one mechanism to modulate cell adhesion and migration in the nervous system.

Aging↗
PubMed1992

Cloning of a major heparan sulfate proteoglycan from brain and identification as the rat form of glypican.

We have obtained the complete coding sequence of a highly conserved heparan sulfate proteoglycan which we previously characterized biochemically after isolation from rat brain. An open reading frame of 558 amino acids encodes a protein with a molecular mass of 62 kDa containing three peptide sequences present in the isolated proteoglycan. The total sequence obtained is 3.5 kb long, including 1.6 kb of 3'-untranslated sequence and 0.2 kb of 5'-untranslated sequence. The deduced amino acid sequence and the 3'- and 5'-untranslated sequences have 89% and 66-80% identity, respectively, with those of a phosphatidylinositol-anchored human lung fibroblast heparan sulfate proteoglycan (glypican) for which mRNA is detectable in a large number of human cell lines. Our data therefore demonstrate that this major heparan sulfate proteoglycan of brain is the rat form of glypican.

Amino Acid Sequence↗
PubMed1992

Cloning and primary structure of neurocan, a developmentally regulated, aggregating chondroitin sulfate proteoglycan of brain.

We have obtained the complete coding sequence of neurocan, a chondroitin sulfate proteoglycan of rat brain which is developmentally regulated with respect to its molecular size, concentration, carbohydrate composition, sulfation, and immunocytochemical localization. Two degenerate oligonucleotides, based on amino acid sequence data from the proteoglycan isolated from adult brain by immunoaffinity chromatography with the 1D1 monoclonal antibody, were used as sense and antisense primers in the polymerase chain reaction with a brain cDNA library as template to generate an unambiguous cDNA probe. A second probe for the N-terminal portion of the early postnatal form of the proteoglycan was obtained by reverse transcription/polymerase chain reaction. The composite sequence of overlapping cDNA clones is 5.2-kilobases (kb) long, including 1.3 kb of 3'-untranslated sequence and 76 base pairs of 5'-untranslated sequence. An open reading frame of 1257 amino acids encodes a protein with a molecular mass of 136 kDa containing 10 peptide sequences present in the adult and/or early postnatal brain proteoglycans. The deduced amino acid sequence revealed a 22-amino acid signal peptide followed by an immunoglobulin domain, tandem repeats characteristic of the hyaluronic acid-binding region of aggregating proteoglycans, and an RGDS sequence. The C-terminal portion (amino acids 951-1215) has approximately 60% identity to regions in the C termini of the fibroblast and cartilage proteoglycans, versican and aggrecan, including two epidermal growth factor-like domains, a lectin-like domain, and a complement regulatory protein-like sequence. The central 595-amino acid portion of neurocan has no homology with other reported protein sequences. The proteoglycan contains six potential N-glycosylation sites and 25 potential threonine O-glycosylation sites. In the adult form of the proteoglycan (which represents the C-terminal half of neurocan) a single 32-kDa chondroitin 4-sulfate chain is linked at serin-944, whereas three additional potential chondroitin sulfate attachment sites (only two of which are utilized) are present in the larger proteoglycan species. A probe corresponding to a region of neurocan having no homology with versican or aggrecan hybridized with a single band at approximately 7.5 kb on Northern blots of mRNA from both 4-day and adult rat brain (but not with muscle, kidney, liver, or lung mRNA), indicating that the 1D1 proteoglycan of adult brain, containing a 68-kDa core protein, is generated by a developmentally regulated in vivo proteolytic processing of the 136-kDa species which is predominant in early postnatal brain.(ABSTRACT TRUNCATED AT 400 WORDS)

Aggrecans↗