Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Biglycan”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources
PubMed1990

Vascular smooth muscle biglycan represents a highly conserved proteoglycan within the arterial wall.

Two overlapping cDNA clones containing sequences homologous to human bone biglycan were isolated from a rat vascular smooth muscle (VSM) cell cDNA library. Nucleotide sequence analysis demonstrated that these clones encoded the rat VSM biglycan complete core protein sequence. A high degree of genetic conservation was observed for biglycan since nucleotide sequence homology comparisons revealed an 88% homology occurring between rat and human biglycan cDNA coding regions. The deduced core protein for the secreted form of VSM biglycan was found to be composed of ten leucine-rich repeating units whose consensus sequence was similar to that present in human bone and bovine cartilage biglycans. Protein homology comparisons revealed that the mature rat VSM biglycan core protein was 97% homologous to both human bone and bovine cartilage biglycan core proteins. Most of the amino acid substitutions in the secreted form of rat VSM biglycan are of the conservative type thereby maintaining the hydrophobic property of this proteoglycan within the arterial wall. The highest frequency of amino acid substitutions occurring between rat, bovine and human biglycan core proteins was found to reside within a small hypervariable region located near the N-terminus of these proteoglycans. Rat VSM biglycan was found to contain dinucleotide repeat elements located in the 3' untranslated region of its mRNA which may influence the expression of this transcript. Biglycan mRNA levels were not found to vary significantly as a function of VSM cell density. However, biglycan transcript levels did vary significantly as a function of VSM cell growth state. Similar studies revealed that collagen, fibronectin, and laminin were able to influence biglycan mRNA levels in quiescent VSM cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1998

Decorin, biglycan and their endocytosis receptor in rat renal cortex.

BACKGROUND: Among the small proteoglycans, biglycan and decorin have been proposed to be potent modulators of TGF-beta-mediated inflammatory kidney diseases. They were considered to become induced during glomerulonephritis and to subsequently inactivate the cytokine. METHODS: Decorin and biglycan as well as their endocytosis receptor were investigated in normal rat renal cortex, in anti-Thy-1 glomerulonephritis, in polycystic kidneys, in the remnant kidney following 5/6-nephrectomy, and in kidneys from the Milan normotensive strain by immunohistochemistry and in situ hybridization. Northern blots were used for the detection of mRNA expression for decorin and biglycan in isolated glomeruli. Functional aspects of the endocytosis of decorin and biglycan were studied in cultured mesangial cells. RESULTS: In the normal adult rat kidney decorin was expressed preferentially by Bowman's capsule and by interstitial connective tissue cells, but only in trace amounts by mesangial cells. In contrast, biglycan was found in tubular epithelial cells, in association with glomerular capillaries, podocytes and occasionally in the mesangium. In the tubulointerstitium of diseased kidneys (polycystic kidneys, 5/6-nephrectomy, kidneys from the Milan normotensive strain) there was a general up-regulation of decorin expression, while biglycan was localized only in distinct foci of fibrotic lesions. Glomerulosclerosis (5/6-nephrectomy, Milan normotensive strain) was associated with an increased staining for both decorin and biglycan within glomeruli. However, even in the anti-Thy-1 model of an acute mesangioproliferative glomerulonephritis where the greatest accumulation of decorin was found there was only a slight enhancement of decorin mRNA in isolated glomeruli. Decorin and biglycan become degraded upon receptor-mediated endocytosis. Immunohistochemical investigations indicated that the pattern of expression of the receptor protein correlated well with the immunolocalization of both decorin and biglycan. In vitro experiments with cultured mesangial cells provided direct evidence for the expression of the receptor and for the cell's capability to endocytose decorin as well as biglycan. CONCLUSIONS: Decorin and biglycan are characterized by a distinct expression pattern in the normal rat kidney, whereas the presence of their endocytosis receptor protein correlates with the expression of both proteoglycans. Decorin is almost completely absent in the normal mesangium. Both proteoglycans become up-regulated in various models of renal disease. The mesangial accumulation of decorin in the anti-Thy-1 glomerulonephritis that is observed in spite of the only slightly enhanced mRNA expression could result from decreased decorin turnover and/or increased mesangial retention.

Animals↗
PubMed2000

Expression of decorin, biglycan, and collagen type I in human renal fibrosing disease.

BACKGROUND: The extracellular matrix proteoglycans decorin and biglycan may have a pathogenic role in renal fibrosing disease via regulation of the activity of growth factors, such as transforming growth factor-beta, and effects on collagen type I fibrillogenesis. The expression of decorin and biglycan in human glomerular diseases characterized by mesangial sclerosis is unknown. METHODS: Decorin, biglycan, and collagen type I were localized immunohistochemically in human renal biopsy cases of amyloidosis (N = 18), diabetic nephropathy (N = 11), fibrillary glomerulonephritis (N = 5), immunotactoid glomerulopathy (N = 5), light-chain deposition disease (N = 4), idiopathic mesangial sclerosis (N = 4), and nephrosclerosis (N = 6), and in morphologically normal tissues obtained from tumor nephrectomies (N = 8). Decorin and biglycan mRNA synthesis was evaluated by in situ hybridization. RESULTS: Decorin and biglycan protein were not identified in normal glomeruli. Decorin accumulated in amyloid deposits, but not in deposits of fibrillary glomerulonephritis or immunotactoid glomerulopathy. Biglycan weakly accumulated in amyloid deposits, and both decorin and biglycan weakly stained mesangial nodules in cases of morphologically advanced light-chain deposition disease and diabetic nephropathy. In all analyzed cases, irrespective of the underlying disease, decorin and biglycan accumulated in glomeruli in areas of fibrous organization of the urinary space and in areas of tubulointerstitial fibrosis. Biglycan, but not decorin, accumulated in the neointima of arteriosclerotic blood vessels. Decorin and biglycan mRNA synthesis was detected at sites of proteoglycan accumulation in glomeruli, interstitium, and neointima. Collagen type I colocalized with decorin and biglycan deposits. CONCLUSIONS: Differences in extracellular matrix proteoglycan composition may be diagnostically useful in distinguishing morphologically similar diseases. Distinct patterns of proteoglycan expression may be related to modulation of specific growth factor activity in different glomerular diseases.

Amyloidosis↗
PubMed1999

Distinct secondary structures of the leucine-rich repeat proteoglycans decorin and biglycan. Glycosylation-dependent conformational stability.

Biglycan and decorin have been overexpressed in eukaryotic cells and two major glycoforms isolated under native conditions: a proteoglycan substituted with glycosaminoglycan chains; and a core protein form secreted devoid of glycosaminoglycans (Hocking, A. M., Strugnell, R. A., Ramamurthy, P., and McQuillan, D. J. (1996) J. Biol. Chem. 271, 19571-19577; Ramamurthy, P., Hocking, A. M., and McQuillan, D. J. (1996) J. Biol. Chem. 271, 19578-19584). Far-UV CD spectroscopy of decorin and biglycan proteoglycans indicates that, although they are predominantly beta-sheet, biglycan has a significantly higher content of alpha-helical structure. Decorin proteoglycan and core protein are very similar, whereas the biglycan core protein exhibits closer similarity to the decorin glycoforms than to the biglycan proteoglycan form. However, enzymatic removal of the chondroitin sulfate chains from biglycan proteoglycan does not induce a shift to the core protein structure, suggesting that the final form is influenced by polysaccharide addition only during biosynthesis. Fluorescence emission spectroscopy demonstrated that the single tryptophan residue, which is at a conserved position at the C-terminal domain of both biglycan and decorin, is found in similar microenvironments. This indicates that in this specific domain the different glycoforms do exhibit apparent conservation of structure. Exposure of decorin and biglycan to 10 M urea resulted in an increase in fluorescent intensity, which indicates that the emission from tryptophan in the native state is quenched. Comparison of urea-induced protein unfolding curves provide further evidence that decorin and biglycan assume different structures in solution. Decorin proteoglycan and core protein unfold in a manner similar to a classic two-state model, in which there is a steep transition to an unfolded state between 1 and 2 M urea. The biglycan core protein also shows a similar steep transition. However, biglycan proteoglycan shows a broad unfolding transition between 1 and 6 M urea, probably indicating the presence of stable unfolding intermediates.

Amino Acid Sequence↗
PubMed1998

Effects of interferon-gamma and tumor necrosis factor alpha on the expression of the genes encoding aggrecan, biglycan, and decorin core proteins in cultured human chondrocytes.

OBJECTIVE: To determine the effects of interferon-gamma (IFN gamma) and tumor necrosis factor alpha (TNF alpha), alone or in combination, on the expression of aggrecan, biglycan, and decorin core protein genes in human chondrocytes. METHODS: Isolated human chondrocytes were cultured on poly(2-hydroxyethyl methacrylate)-coated plastic dishes to prevent the loss of cartilage-specific phenotype, and the effects of IFN gamma and TNF alpha, alone or in combination, on aggrecan, biglycan, and decorin core protein gene transcription and steady-state messenger RNA (mRNA) levels were examined. RESULTS: The addition of IFN gamma (1.5 pM) or TNF alpha (0.3 pM) caused a decrease in the steady-state level of aggrecan mRNA (-25% and -15%, respectively), and the combination of these low-concentration cytokines caused a potent inhibition (-66%). These effects were the result of a decrease (-50%) in the transcription rate of the corresponding gene. At the concentrations used, IFN gamma did not alter the levels of biglycan mRNA or the transcription rates of the biglycan core protein gene. In contrast, TNF alpha decreased biglycan steady-state mRNA levels (-62%) and the biglycan core protein gene transcription rate (-18%). The combination of IFN gamma and TNF alpha resulted in a potentiation of the inhibitory effects of TNF alpha on biglycan mRNA levels (-79%) and transcription rate of the biglycan core protein gene (-46%). IFN gamma produced a modest decrease in decorin mRNA levels (-23%) and decorin core protein gene transcription rate (-17%). In contrast, TNF alpha resulted in a marked increase in decorin mRNA levels (+260%) that was not the result of transcriptional regulation. Notably, the combination of IFN gamma and TNF alpha potentiated the inhibitory effects of IFN gamma on decorin mRNA (-80%) and on the transcription of the corresponding gene (-43%). Similar results were obtained in fetal and adult articular chondrocytes. CONCLUSION: These data demonstrate that 1) the expression of the core protein genes encoding the cartilage proteoglycans aggrecan, biglycan, and decorin is differentially regulated by IFN gamma and TNF alpha; 2) these effects are mediated by transcriptional and posttranscriptional mechanisms; and 3) the combination of the 2 cytokines causes a potent inhibitory effect on the expression of the genes for the core proteins of these 3 proteoglycans, which occurs largely at the transcriptional level. The inhibition of aggrecan, decorin, and biglycan core protein gene expression by the combination of IFN gamma and TNF alpha may contribute to the cartilage destruction that is characteristic of inflammatory joint diseases.

Adult↗
PubMed1997

Effects of bone CS-proteoglycans, DS-decorin, and DS-biglycan on hydroxyapatite formation in a gelatin gel.

The small leucine-rich bone proteoglycans, biglycan and decorin, can be purified by chromatography on hydroxyapatite columns, demonstrating their potential affinities for bone apatite. To determine their effects on in vitro apatite formation and growth, a mixture of the chondroitin-sulfate (CS) bone proteoglycans, or purified fractions of the dermatan sulfate (DS) containing proteoglycans, DS-decorin and DS-biglycan obtained from skin and articular cartilage, respectively, were analyzed in a gelatin gel diffusion system in which apatite formation occurs in the absence of proteins in a 3.5 day period. Low concentrations of the bone CS-proteoglycan mixture and low DS-biglycan concentrations (5-25 microg/ml) increased apatite formation relative to proteoglycan-free controls at 3.5 days. The CS-proteoglycan mixture was less effective at 50 microg/ml than at 10 microg/ml. DS-biglycan was similarly most effective at 5-25 microg/ml. At 5 days, when apatite growth and proliferation were assessed, 10 and 50 microg/ml of both CS-bone proteoglycan and DS-biglycan increased mineral yields. DS-decorin, in contrast, had no significant effect on mineral accumulation at any of these concentrations. In seeded growth experiments, 1 and 10 microg/ml CS-proteoglycan and 10 and 50 microg/ml DS-biglycan were significant effective inhibitors of mineral accretion, whereas DS-decorin showed no tendency to inhibit seeded growth. Using molar extinction coefficients to determine concentrations, the binding of DS-biglycan and DS-decorin to apatite (specific surface 54 m2/g) was determined using a Langmuir adsorption isotherm model. DS-biglycan had a greater affinity for apatite than DS-decorin (0.285 ml/micromol versus 0.0098 ml/micromol). DS-biglycan binding was more specific with fewer binding sites (3.5 micromol/m2 compared with 18. 2 micromol/m2 for DS-decorin). Data suggest that of the small proteoglycans, biglycan may play a more significant role than decorin in the regulation of mineralization.

Animals↗
PubMed1993

Identification and characterization of glycanated and non-glycanated forms of biglycan and decorin in the human intervertebral disc.

Immunological studies revealed the presence of several different forms of biglycan and decorin in human intervertebral-disc tissues (annulus fibrosus, nucleus pulposus and cartilage end-plate). In the young intervertebral disc, glycosaminoglycan-containing (glycanated) forms of both biglycan and decorin represented a greater proportion of the total proteoglycan population present in extracts of annulus fibrosus and cartilage end-plate compared with extracts of nucleus pulposus, in which they were barely detectable. In older discs the glycanated forms of biglycan and decorin represented only a small proportion of the total proteoglycan present. Immunochemical analyses with an antibody to chondroitin/dermatan sulphate isomers indicated differences in the glycosaminoglycans substituted on glycanated forms of small proteoglycans found in different disc tissues. Dermatan sulphate was the predominant glycosaminoglycan present on biglycan and decorin in annulus fibrosus extracts, whereas chondroitin 4-sulphate was present in both small proteoglycans isolated from cartilage end-plate. In addition, immunochemical analyses with antibodies against core protein epitopes identified two non-glycanated forms of both biglycan and decorin. These non-glycanated forms of the small proteoglycans were found in all three regions of the disc. The two nonglycanated forms of biglycan had estimated molecular masses of 37 and 41 kDa and those of decorin were 43 and 45 kDa, respectively. These non-glycanated forms of biglycan and decorin increased in proportion with aging. N-terminal sequence analysis indicated that the larger non-glycanated form of decorin was a degradation product of its glycanated precursor. However, no N-terminal sequence information was obtainable from the other non-glycanated form of decorin or the two non-glycanated forms of biglycan. These data are consistent with the hypothesis that some of the non-glycanated forms of decorin and biglycan are degradation products of native precursors. However, the possibility remains that several different post-translationally modified forms of decorin and biglycan are synthesized by intervertebral-disc tissues.

Adolescent↗
PubMed1993

Interaction of heparin cofactor II with biglycan and decorin.

Two small interstitial dermatan sulfate-containing proteoglycans, biglycan and decorin, are present in extracellular matrices of skin, tendon, ligament, and cartilage. We investigated the effects of biglycan and decorin on the inhibition of alpha-thrombin by the serine proteinase inhibitor heparin cofactor II. In solution, heparin cofactor II inhibition of thrombin is accelerated by intact biglycan or decorin and by the dermatan sulfate-containing glycosaminoglycan (GAG) chains prepared from the proteoglycans, while core protein from cartilage biglycan had no effect. L-Iduronic acid-rich skin decorin and GAG chains had a greater accelerating effect than proteoglycan and GAG chains from cartilage that had lower L-iduronic acid content. Treatment of skin decorin and GAG chains with chondroitinase ABC totally eliminated the ability of these compounds to accelerate thrombin inhibition by heparin cofactor II suggesting that dermatan sulfate was responsible for this action. Both biglycan and decorin bound to type V collagen in a saturable and specific manner. Biglycan, decorin, and core protein from biglycan competed for decorin binding to the type V collagen, while only the intact proteoglycans competed for biglycan binding. When bound to type V collagen, both biglycan and decorin accelerated the heparin cofactor II/thrombin inhibition reaction as efficiently as the proteoglycans in solution. Our results demonstrate that heparin cofactor II in the presence of biglycan or decorin bound to type V collagen provides a "thromboresistant surface," further suggesting a physiological function for these proteins in regulating the extravascular activities of thrombin.

Animals↗
PubMed1996

Eukaryotic expression of recombinant biglycan. Post-translational processing and the importance of secondary structure for biological activity.

Biglycan is a small chondroitin sulfate proteoglycan found in many tissues and is structurally related to decorin, fibromodulin, and lumican. The biological function of biglycan is poorly understood, although several studies have indicated interaction with other extracellular matrix components. We have initiated studies of structural and functional domains of biglycan by transient eukaryotic expression using the vaccinia virus/T7 bacteriophage expression system. A recombinant vaccinia virus, vBGN4 encoding the mature biglycan core protein as a polyhistidine fusion protein under control of the T7 phage promoter was expressed in HT-1080 cells and UMR106 cells. The structure of the recombinant biglycan secreted by these cells was defined by analyzing molecules labeled in the presence of [35S]sulfate, [3H]glucosamine, and [35S]methionine. Glycoforms of biglycan were separated by imidazole gradient elution, under non-denaturing conditions, and comprised: a large proteoglycan form substituted with two chondroitin sulfate chains of molecular mass approximately 34 kDa (HT-1080 cells) or approximately 40 kDa (UMR106 cells); a small proteoglycan form substituted with two chondroitin sulfate chains with a median molecular mass approximately 28 kDa; and a core protein form secreted devoid of glycosaminoglycan chains. All the glycoforms were substituted with two N-linked oligosaccharides, and the disaccharide composition of the two glycosaminoglycan populations were identical. Approximately 70% of the recombinant biglycan secreted by HT-1080 cells was substituted with chondroitin sulfate chains, whereas about 50% of the biglycan expressed by UMR106 cells was substituted with chondroitin sulfate chains. Infection with vBGN4 in both HT-1080 and UMR106 cells resulted in the production of approximately 10 mg of biglycan/10(9) cells per 24 h. The native recombinant biglycan was shown to bind to collagen type V and the complement protein, C1q. However, when the secondary structure of recombinant biglycan was disrupted by exposure to 4 M guanidine hydrochloride, the affinity for collagen type V was dramatically reduced. These data demonstrate the importance of secondary structure to the function of this small proteoglycan.

Amino Acid Sequence↗
PubMed1996

Transcriptional regulation of the human biglycan gene.

The small leucine-rich proteoglycan biglycan is involved in several physiological and pathophysiological processes through the ability of its core protein to interact with other extracellular matrix molecules and transforming growth factor-beta (TGF-beta). To learn more about the regulation of biglycan core protein expression, we have cloned and sequenced 1218 base pairs from the 5'-flanking region of the human biglycan gene, demonstrated functional promoter activity, and investigated the molecular mechanisms through which various agents modulate its transcriptional activity. Sequencing revealed the presence of several cis-acting elements including multiple AP-2 sites and interleukin-6 response elements, a NF-kappaB site, a TGF-beta negative element, and an E-box. The TATA and CAAT box-lacking promoter possesses many features of a growth-related gene, e.g. a GC-rich immediate 5' region, many Sp1 sites, and the use of multiple transcriptional start sites. Transient transfections of the tumor cell lines MG-63, SK-UT-1, and T47D with various biglycan 5'-flanking region-luciferase reporter gene constructs showed that the proximal 78 base pairs are sufficient for full promoter activity. Several agents among them interleukin-6, and tumor necrosis factor-alpha. were capable of altering biglycan promoter activity. However, in MG-63 cells, TGF-beta1 failed to increase either activity of the biglycan promoter constructs or specific transcription from the endogenous biglycan gene. Since TGF-beta1 also did not alter the stability of cytoplasmic biglycan mRNA as determined from Northern analysis after inhibition of transcription with 5,6-dichloro-1beta-D-ribofuranosylbenzimidazole, an as yet unidentified nuclear post-transcriptional mechanism was considered responsible for the TGF-beta effect in this cell type. These results might help to elucidate the molecular pathways leading to pathological alterations of biglycan expression observed in atherosclerosis, glomerulonephritis, and fibrosis.

Base Sequence↗
PubMed1998

Comparison of apolipoprotein and proteoglycan deposits in human coronary atherosclerotic plaques: colocalization of biglycan with apolipoproteins.

BACKGROUND: Because the content of specific proteoglycans and apolipoproteins is increased in atherosclerotic plaques and in vitro studies have suggested a role for proteoglycans in mediating plaque apolipoprotein (apo) retention, immunohistochemistry was performed to systematically examine the relative locations of proteoglycans and apolipoproteins in human atherosclerosis. METHODS AND RESULTS: The spatial relationships of versican, biglycan, and apoE were compared on 68 human coronary artery segments; apoA-I and apoB also were evaluated on an additional 20 segments. Nonatherosclerotic intima contained extensive deposits of versican, whereas deposits of apoE, apoB, and apoA-I were much less prevalent. In contrast, nearly all atherosclerotic segments contained substantial deposits of biglycan, apoE, apoA-I, and apoB. There was a high degree of colocalization of apoE and biglycan deposits. ApoA-I, the major apolipoprotein of HDL, and apoB also were detected in regions with apoE and biglycan deposition. Exceptions to the localization of biglycan with apolipoproteins were found in regions that lacked intact extracellular matrix because of necrosis or dense macrophage accumulation. In vitro studies demonstrated that biglycan binds apoE-containing but not apoE-free HDL and that biglycan also binds LDL. CONCLUSIONS: These results suggest that biglycan may bind apoE and apoB in atherosclerotic intima. They also raise the possibility that apoE may act as a "bridging" molecule that traps apoA-I-containing HDL in atherosclerotic intima. Taken together, these findings are consistent with the hypothesis that biglycan may contribute to the pathogenesis of atherosclerosis by trapping lipoproteins in the artery wall.

Apolipoprotein A-I↗
PubMed1992

Differential regulation of biglycan and decorin by retinoic acid in bovine chondrocytes.

The small, leucine-rich proteoglycans, decorin and biglycan, are prominent components of many extracellular matrices and are differentially regulated in various tissues. We have examined the effects of retinoic acid (RA) on the expression of biglycan and decorin at the protein and mRNA levels in cultured bovine articular chondrocytes. Biglycan protein expression is rapidly turned off after 1-2 days of treatment with RA. In contrast, decorin protein expression is increased 12-18-fold following 3 days of RA treatment. The level of biglycan mRNA was also rapidly reduced upon RA treatment, mirroring the protein expression. The reduction was apparent by 6 h, and, by 4 days, the levels were nearly undetectable. In contrast, decorin mRNA was induced upon treatment with RA. The increase in decorin message levels was first apparent by 24 h, reaching maximum by 2 days, and remained constant through 4 days. The repression of biglycan mRNA displayed equal sensitivity to RA concentrations from 10(-5) to 10(-9) M. Decorin mRNA was induced in a dose-dependent fashion by RA. Retinoic acid at a concentration of 10(-5) M, the highest dose examined, resulted in maximal induction of the message, and control levels were obtained with 10(-8) M. The protein synthesis inhibitor cycloheximide inhibited the induction of decorin mRNA, indicating that the induction by RA was a secondary event. In contrast, the repression of biglycan by RA was not significantly altered by cycloheximide, showing that the repression was a direct effect. Actinomycin D inhibited the induction of decorin mRNA, indicating that transcription was required for the induction. Nuclear run-on assays confirmed that RA was regulating biglycan mRNA expression at the transcription level. A 24-h RA treatment decreased the level of transcription of the biglycan gene 5-fold. In contrast, no increase in transcription from the decorin gene could be detected by nuclear run-on assays. Therefore, the elevation in decorin mRNA levels observed after RA treatment was the result of a post-transcriptional event, most likely the consequence of stabilization of the message. This study demonstrates that the genes for these two similar proteoglycans are under very different forms of regulation by RA in chondrocytes. The pattern of differential expression of biglycan and decorin could serve as an additional marker for indicating changes of the cartilage phenotype.

Amino Acid Sequence↗
PubMed1994

The self-association of biglycan from bovine articular cartilage.

Biglycan is a small dermatan sulfate proteoglycan present in the extracellular matrix of a variety of connective tissues. Sedimentation velocity and equilibrium studies were carried out to determine the monomer molecular weight of biglycan in denaturing solvents and to define the oligomeric states of biglycan in physiologic solvents in the presence and absence of Zn2+. In 6 M guanidine chloride, biglycan is a monomer with s0(20,w) = 2.9 S and Mz = 93,100 (where Mz is z-average molecular weight). In 0.15 M NaCl, 50 mM Tris, pH 7.5, in the absence of divalent metal ions, and at concentrations above 1 mg/ml, biglycan is predominantly dimer (s0(20,w) = 4.8 S). Under these same conditions in solvent containing 5 mM Zn2+, biglycan exists predominantly as a hexamer, with s0(20,w) = 9.4 S and Mz approximately 600,000. In either case, the oligomers dissociate reversibly. In order to determine whether the glycosaminoglycan chains or the core protein was responsible for self-association, sedimentation velocity and sedimentation equilibrium studies were conducted on the isolated components. Dermatan sulfate chains prepared from biglycan, examined in both denaturing and physiologic solvents, show no significant difference in molecular weight (Mz approximately 22,000), whether or not the solvents contain Zn2+. However, biglycan core protein strongly self-associated in physiologic solvents. Thus, the self-association of biglycan appears to be mediated by the core protein and not by its glycosaminoglycan chains.

Animals↗
PubMed1995

Facilitation of learning following injection of the chondroitin sulfate proteoglycan biglycan into the vicinity of the nucleus basalis magnocellularis.

The aim of this study was to examine the effects of biglycan, a small chondroitin sulfate proteoglycan with neurotrophic activity, on memory and reinforcement upon unilateral injection into the region of the nucleus basalis magnocellularis (NBM). In experiment 1, rats with chronically implanted cannulas were injected with biglycan and tested on the uphill avoidance task, which involves punishment of a high-probability turning response on a tilted platform (negative geotaxis). Immediately after the training trial, that is, after a tail-shock was administered upon performing the response, rats received one microinjection (0.5 microliter) of substance P (SP) in a reference dosage of 0.74 pmol or biglycan (doses ranging from 1.3 to 1300.0 nmol) into the NBM region. When tested 24 h later, rats treated with SP (0.74 pmol) or biglycan (2.1 and 2.6 nmol) had significantly longer uphill latencies than vehicle (PBS) controls, indicative of superior learning of the avoidance response. In experiment 2, a test for possible proactive effects of post-trial biglycan on performance during the retention trial was performed. Furthermore, the uphill avoidance task was combined with a conditioned place preference task to assess possible reinforcing effects of biglycan. Rats were injected with either 2.6 or 130.0 nmol biglycan immediately after the training trial of the uphill task. One control group received 2.6 nmol biglycan 5 h after the trial, a second group was sham-operated. Additional groups were included which received biglycan (2.6 or 130.0 nmol), SP (0.74 pmol) or PBS after the training trial but no tail-shock.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Biglycan gene promoter activity in osteosarcoma cells is regulated by cyclic AMP.

The pericellular proteoglycan biglycan is among the major secretory products of osteoblasts and articular chondrocytes but the regulatory agents and signal transduction pathways that ultimately lead to alterations in biglycan gene expression are poorly defined. We report here on the transcriptional up-regulation of biglycan in MG-63 osteosarcoma cells by agents that increase intracellular cAMP levels. Transfection of these cells with biglycan promoter luciferase reporter fusion genes and subsequent treatment with forskolin or the cAMP analog 8-Bromo-cAMP resulted in an up to 3.8-fold stimulation of biglycan promoter activity. This effect could be prevented with the compound KT5720, a specific inhibitor of the cAMP-dependent protein kinase. Up-regulation of transcription is also reflected at the level of mRNA expression, since biglycan mRNA steady state levels in MG-63 cells increased approximately 2-fold after 24 hours of forskolin treatment. These data suggest that elevated levels of intracellular cAMP increase transcription from the biglycan promoter in bone cells and implicate for the first time the cAMP/protein kinase A signal transduction pathway in the regulation of biglycan gene expression.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1998

Increase in the expression of biglycan mRNA expression Co-localized closely with that of type I collagen mRNA in the infarct zone after experimentally-induced myocardial infarction in rats.

Biglycan, a small dermatan sulphate proteoglycan, has been postulated to interact with other components of the extracellular matrix (ECM), specifically collagens. We hypothesized that biglycan messenger ribonucleic acid (mRNA) is increased in the myocardial infarct zone. Biglycan mRNA expression after acute myocardial infarction (AMI) in rats was determined with the use of Northern blotting and in situ hybridization, and its expression pattern was compared to that of type I collagen mRNA [alpha1(I) collagen]. The left coronary artery was ligated in male Sprague-Dawley rats, and the hearts were excised on days 2 and 7. The Northern blot analysis demonstrated that expression of biglycan mRNA in the infarct on days 2 and 7 were 4.0- and 6.8-fold higher, respectively, compared to the sham-operated hearts. The in situ hybridization revealed intense signals for both biglycan and alpha1(I) collagen mRNA on day 2 in the spindle-shaped mesenchymal cells located between the surviving myocytes in the infarct peripheral zone. On day 7, biglycan mRNA signals were observed in the interior of the infarct around the infarct granulation tissue, a distribution that was essentially the same as that of alpha1(I) collagen. These results demonstrated that the increases in the infarct biglycan mRNA expression produced by mesenchymal cells (presumably myofibroblasts and fibroblasts) was closely co-localized with that of type I collagen mRNA, indicating that biglycan contributes to the infarct healing processes.

Animals↗
PubMed1996

Presence of pro-forms of decorin and biglycan in human articular cartilage.

The proteoglycans decorin and biglycan in extracts of human articular cartilage were analysed by SDS/PAGE and immunoblotting, using antisera raised to peptide sequences present in the pro-regions and the mature core proteins. In adult cartilage, both pro-forms and mature processed forms of the proteoglycan core protein were observed for both decorin and biglycan. In the case of biglycan, it was also shown that additional proteolytic processing takes place after removal of the propeptide and that this accounts for the presence of non-glycanated forms of the molecule. For both decorin and biglycan, the relative abundance of the pro-forms was much less in the juvenile than the adult. Different adult connective tissues, including meniscus, tendon and intervertebral disc were also examined for the presence of pro-forms of the proteoglycans. While the mature form of decorin was present at a similar level in extracts of all tissues examined, the pro-form was only detected in the articular cartilage. In the case of biglycan, the abundance of the mature form was more varied, with high levels in articular cartilage, intermediate levels in meniscus and the annulus fibrosus of the intervertebral disc, low levels in the nucleus pulposus of the intervertebral disc, and non-detectable levels in the patellar tendon. The pro-form of biglycan was detected in the disc tissue extracts, albeit at a lower level than in articular cartilage, but was not detected in the meniscus or tendon. The proportion of the pro-form relative to the mature form of biglycan was, however, higher in the nucleus pulposus of the intervertebral disc than in articular cartilage. Thus, the persistence of pro-forms of both decorin and biglycan is a feature of the extracellular matrix of some connective tissues, although their abundance is both tissue- and age-dependent, with adult articular cartilage being a particularly rich source.

Adult↗
PubMed1995

Interaction of biglycan with type I collagen.

The small proteoglycan decorin is known to interact with type I collagen fibrils, thereby influencing the kinetics of fibril formation and the distance between adjacent collagen fibrils. The structurally related proteoglycan biglycan has been proposed not to bind to fibrillar collagens. However, when osteosarcoma cells were cultured on reconstituted type I collagen fibrils, both decorin and biglycan were retained by the matrix. Immunogold labeling at the electron microscopic level showed that both proteoglycans were distributed along collagen fibrils not only in osteosarcoma cell-populated collagen lattices but also in human skin. Reconstituted type I collagen fibrils were able to bind in vitro native and N-glycan-free biglycan as well as recombinant biglycan core protein. From Scatchard plots dissociation, constants were obtained that were higher for glycanated biglycan (8.7 x 10(-8) mol/liter) than for glycanated decorin (7 x 10(-10) mol/liter and 3 x 10(-9) mol/liter, respectively). A similar number of binding sites for either proteoglycan was calculated. Recombinant biglycan and decorin were characterized by lower dissociation constants compared with the glycanated forms. Glycanated as well as recombinant decorin competed with glycanated biglycan for collagen binding, suggesting that identical or adjacent binding sites on the fibril are used by both proteoglycans. These data suggest that, because of its trivalency, biglycan could have a special organizing function on the assembly of the extracellular matrix.

Biglycan↗