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Results for “Integrin-Binding Sialoprotein”

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At least 55 records · Page 3Linked to original sources
PubMed1991

Repair of intra-membranous bone fractures and defects in rats. Immunolocalization of bone and cartilage proteins and proteoglycans.

Osseous healing of experimental fractures and defects in membranous bone was studied in an animal model and the appearance and localization of selected bone and cartilage proteins and proteoglycans determined by polyclonal antibodies. The bone lesions were made in the parietal bone of young rats and subsequently studied on days 3, 5, 8, 15, 30, and 100 after surgery. The bone matrix proteins investigated (62 kDa, bone sialoprotein I and II, and osteopontin) appeared early, adjacent to the periosteal surfaces (pericranium and dura mater) and the marginal bone. The staining reactions were maximal at days 8 or 15 after trauma. Similar patterns were discerned for some cartilage macromolecules studied (58 kDa, 59 kDa, and chondrocalcin), although others showed no labelling whatsoever (148 kDa, and 400 kDa proteins). The proteoglycans PG-S1, PG-S2, and PG-LA were not identified. No callus or cartilage formation were associated with the bone healing process, and the differences between the regenerative pattern of the fractures and defects were limited. The findings emphasize the importance of rigid fixation in craniomaxillofacial surgery.

Animals↗
PubMed1991

Biosynthesis of bone proteins [SPP-1 (secreted phosphoprotein-1, osteopontin), BSP (bone sialoprotein) and SPARC (osteonectin)] in association with mineralized-tissue formation by fetal-rat calvarial cells in culture.

To determine the relationship between the expression of bone proteins and the formation of mineralized-tissue matrix, the biosynthesis of non-collagenous bone proteins was studied in cultures of fetal-rat calvarial cells, which form mineralized nodules of bone-like tissue in the presence of beta-glycerophosphate. The temporal pattern of protein synthesis in both mineralizing and non-mineralizing cultures was studied by metabolic labelling with [35S]methionine, 35SO4(2-) or 32PO4(3-) over a 5-day period. After a 24 h labelling period, the culture media were harvested and the cell layers extracted sequentially with aq. 0.5 M-NH3, followed by 4 M-guanidinium chloride (GdmCl), 0.5 M-EDTA and a second extraction with 4 M-GdmCl. Protein associated with collagenous bone matrix was analysed after digestion with bacterial collagenase. On the basis of [35S]methionine labelling, the major proteins extracted from the mineralizing matrix were secreted phosphoprotein-1 (SPP-1; osteopontin), bone sialoprotein (BSP) and a 14 kDa phosphoprotein. The presence of SPP-1 and BSP in the conditioned media of both mineralizing and non-mineralizing cultures and their incorporation into the mineralizing nodules indicated that these proteins associate with preformed mineral crystals. However, some BSP was also present in GdmCl extracts and, together with a 35 kDa sulphated protein, was released from a bacterial-collagenase digestion of the tissue residue in both non-mineralizing and mineralizing cultures. Two forms of sulphated SPP-1 were identified, a highly phosphorylated 44 kDa species being the predominant form in the mineralized matrix. The BSP was more highly sulphated but less phosphorylated than SPP-1. Bone SPARC (secreted protein, acid and rich in cysteine) protein (osteonectin) was present almost entirely in the conditioned media and did not incorporate 32PO4(3-) or 35SO4(2-). The SPP-1 and the 14 kDa protein were susceptible to thrombin digestion, the 44 kDa SPP-1 being specifically cleaved into 28 and 26 kDa fragments. The fragments were labelled uniformly with [35S]methionine, but the 28 kDa fragment incorporated more 35SO4(2-), but less 32PO4(3-), than the 26 kDa fragment. These studies demonstrate that SPP-1 and BSP are the major osteoblast-derived bone proteins to bind to the bone mineral. That BSP also binds to the collagenous bone matrix indicates a potential role for this protein in linking the hydroxyapatite with collagen.

Animals↗
PubMed1995

An inverted TATA box directs downstream transcription of the bone sialoprotein gene.

The orientation of the TATA box is thought to direct downstream transcription of eukaryotic genes by RNA polymerase II. However, the putative TATA box in the promoter of the bone sialoprotein (BSP) gene, which codes for a tissue-specific and developmentally regulated bone matrix protein, is inverted (5'-TTTATA-3') relative to the consensus TATA box sequence (5'-TATAAA-3') and is overlapped by a vitamin D3-response element. Here we show that the inverted TATA sequence in the rat BSP gene binds to recombinant TATA-box-binding protein (TBP) with an affinity similar to that observed with the consensus TATA box, and site-directed point mutations in the inverted TATA sequence (mutating TTTATA into TCTCTA) abrogate both TBP binding and BSP promoter activity. However, when the inverted TATA sequence is changed to a canonical TATAAA, the TBP- and vitamin D3 receptor-binding properties together with the BSP promoter activity are retained. In addition, we found that the TBP is required to reconstitute in vitro transcription driven by the BSP promoter. These studies, which have revealed a naturally occurring inverted TATA box that can bind TBP and direct downstream transcription, demonstrate that the orientation of the TATA box does not determine the direction of transcription in higher eukaryotic genes. Consequently, the inverted TATA box that is conserved in the human, rat and mouse BSP gene promoters will provide an excellent in vivo model to investigate the polarity of the transcription factor IID-DNA complex and its relation to downstream transcription.

Animals↗
PubMed1995

Expression of bone-related protein messenger RNA in human meningiomas: possible involvement of osteopontin in development of psammoma bodies.

Meningiomas often contain concentric calcified foci, referred to as psammoma bodies. Since calcium phosphate deposits in both psammoma bodies and bone tissues, we examined whether messenger (m) RNA of bone-related extracellular matrix proteins and bone morphogenetic proteins (BMP) were expressed in human meningioma tissues. Northern blotting demonstrated the expression of osteopontin (OPN), matrix Gla protein (MGP), osteonectin (ON) and BMP-4 mRNA but not bone sialoprotein, osteocalcin and BMP-2 mRNA. In situ hybridization revealed that most OPN mRNA-expressing cells were located around the psammoma bodies in meningothelial whorls. Moreover, combination of in situ hybridization and immunohistochemistry on serial sections showed that the OPN mRNA-expressing cells were CD68-positive, suggesting they were macrophages. Immunohistochemistry with anti-OPN antibody and von Kossa staining on the adjacent section showed that the deposition site of OPN protein was consistent with that of calcium phosphate. Neither MGP nor ON mRNA expression appeared to correlate with the calcification. The present result suggests that OPN produced by CD68-positive macrophages may play a significant role for development of psammoma bodies in meningiomas.

Antibodies, Monoclonal↗
PubMed1989

Specific binding of bone sialoprotein to Staphylococcus aureus isolated from patients with osteomyelitis.

Bone sialoprotein is selectively bound by Staphylococcus aureus cells isolated from patients suffering from infections of bone tissue [Rydén, C., Maxe, I., Franzén, A., Ljungh, A., Heinegård, D. & Rubin, K. (1987) Lancet II, 514]. In the present communication the binding of bone sialoprotein to staphylococcal cells is characterized in more detail. 125I-Labelled bone sialoprotein bound to suspended staphylococcal cells in a time-dependent, saturable and reversible manner. Binding was inhibited by unlabelled bone sialoprotein and by an amino-terminal CNBr fragment of bone sialoprotein that did not contain the eukaryotic cell-binding site. Binding was furthermore inhibited by lysates obtained from Escherichia coli lysogens carrying a lambda gt11 phage-encoding bone sialoprotein. In contrast, binding was not inhibited by a bacterial lysate from an osteopontin lambda gt11 lysogen, nor by N-linked oligosaccharide isolated from bone sialoprotein or by proteoglycan from rat chondrosarcoma containing clustered O-linked oligosaccharides of the same structure as those of bone sialoprotein. These results indicate that the major staphylococcal-binding site resides in the bone sialoprotein core protein and not in the carbohydrate side chains. No inhibition of bone sialoprotein binding could be detected for whole human serum or purified plasma proteins such as fibronectin, fibrinogen and IgG. Likewise, staphylococcal protein A or rat collagen type I did not inhibit the binding of bone sialoprotein. The latter results indicate that the binding site for bone sialoprotein on staphylococcal cells was not any of the hitherto described staphylococcal cell-surface proteins. Binding data indicated an average of 1000 bone-sialoprotein-binding sites/bacterial cell.

Animals↗
PubMed1995

Glucocorticoid regulation of bone sialoprotein (BSP) gene expression. Identification of a glucocorticoid response element in the bone sialoprotein gene promoter.

Glucocorticoids modulate the development and growth of many organs through interactions with a specific intracellular receptor (glucocorticoid receptor) that regulates gene transcription through a cognate element, the glucocorticoid response element (GRE), in the promoter of target genes. In bone formation glucocorticoids stimulate osteoblast differentiation and the formation of bone matrix. Recent studies have demonstrated that the induction of the bone sialoprotein (BSP) gene is associated with osteoblast differentiation and de novo bone formation. To determine the molecular pathways of glucocorticoid regulation of BSP expression, we have analyzed the effects of the synthetic glucocorticoid, dexamethasone, on the expression of the BSP by bone cells in vitro. At 10 nM, dexamethasone induced BSP expression in association with bone tissue formation by confluent fetal rat calvarial cells and adult rat marrow cells and also stimulated BSP expression up to sixfold in osteoblastic cells (UMR 106-6 and ROS 17/2.8 cells). Most of the stimulation was blocked by cycloheximide, indicating direct and indirect mechanisms of BSP gene regulation. Nuclear 'run-on' transcription analysis revealed an up to twofold increase in transcription corresponding to the increase in mRNA that was unaffected by cycloheximide. Analysis of BSP mRNA in the presence of a transcription inhibitor (5,6-dichloro-1-beta-D-ribofuanosyl benzimidazole) by Northern hybridization revealed that the stability of the BSP mRNA was not significantly altered by dexamethasone, indicating that the major, indirect, stimulation of BSP expression involves a nuclear post-transcriptional mechanism. To study the direct effects of dexamethasone, nucleotide sequence analysis of the rat BSP promoter was extended upstream to position -2992 and downstream to +2282 in the first intron. Transient transfection analyses, using various rat BSP promoter constructs linked to a luciferase reporter gene, and gel mobility shift assays were used to identify a putative glucocorticoid response unit comprising three GRE half-sites and a putative AP-1 site, located within positions -906 to -931 upstream from the translation start site of the BSP gene promoter. BSP transcription was stimulated approximately 1.5-fold by dexamethasone through this GRE, indicating that its direct effects are mediated by glucocorticoid receptor binding to this site. These studies, therefore, have identified both indirect and direct pathways of glucocorticoid regulation of BSP gene expression, the direct effects being mediated by a GRE in the rat BSP promoter through which the effects of glucocorticoids on BSP gene transcription appear to be regulated.

Animals↗
PubMed1995

Localization and expression of osteopontin in mineralized and nonmineralized tissues of the periodontium.

To summarize results from various studies focusing on determining the expression/localization of BSP and OPN during tooth root development, there is general agreement that OPN is expressed/localized to the root surface during cementogenesis and is also seen throughout the PDL region. The expression/localization of OPN to odontoblasts and its role in dentinogenesis is less apparent. Recent studies directed at establishing odontoblast cell lines should help to resolve this conflict. Studies on BSP expression during tooth root formation indicate a very precise expression and localization of this molecule during cementogenesis indicating that this molecule may play an important role in the formation of this mineralized tissue. However, as with OPN, the expression of BSP and its role in dentin formation is not clearly defined.

Animals↗
PubMed1995

Cartilage and bone metabolism in rheumatoid arthritis. Differences between rapid and slow progression of disease identified by serum markers of cartilage metabolism.

Serum concentrations of specific cartilage and bone molecules reflecting tissue turnover were measured in two well-defined patient groups with early rheumatoid arthritis with distinctly different disease outcome to see if early differences in their levels are prognostic of the rate of joint destruction. Compared with a matched normal population, increased concentrations of cartilage oligomeric matrix protein (COMP) were found in all patients who developed rapid hip joint destruction. In contrast, levels of a putative marker of cartilage aggrecan synthesis, the chondroitin sulfate epitope 846, were increased only in patients with slow joint destruction. Levels of bone sialoprotein (BSP) were increased in both groups, as were levels of the C-propeptide of type II procollagen (CPII), a marker of collagen II synthesis. The increased concentrations of the 846 epitope in patients with slow joint destruction suggest increased aggrecan synthesis. The low levels of the 846 epitope in patients with rapid joint destruction, concomitant with elevated levels of CPII, suggest a selective increase in collagen synthesis. The elevated BSP levels indicate an increased bone turnover in both groups. Thus elevated serum levels of COMP may indicate an unfavorable prognosis for rapid joint destruction, whereas elevated 846 epitope indicates a more favorable prognosis.

Adult↗
PubMed1991

Cell attachment activity of cementum proteins and mechanism of endotoxin inhibition.

Cementum occupies a unique anatomical location where soft connective tissues of the periodontium are attached to root surfaces. Cell attachment properties of proteins present in cementum were studied. Human and bovine cementum were extracted with 0.5 mol/L CH3COOH followed by 4 mol/L guanidine, and proteins were separated by ion-exchange chromatography and SDS-polyacrylamide gel electrophoresis. Cells were labeled with radioactive amino acids and added to tissue-culture plastic plates incubated with cementum proteins, and attachment was measured. Results showed that cementum proteins promoted the attachment of smooth muscle cells, endothelial cells, and fibroblasts, but not epithelial cells. Fibroblasts attached more efficiently than other cell types, and they manifested spreading with re-organization of actin filaments. No attachment occurred to plates incubated with endotoxin from A. actinomycetemcomitans. Fewer fibroblasts attached to plates treated with cementum proteins in the presence of endotoxin, but cells pre-treated with endotoxin attached normally. Attachment was not inhibited when plates were incubated first with attachment proteins and then with endotoxin; however, it was decreased when endotoxin or bovine serum albumin preceded cementum proteins. Cementum proteins with Mr 68,000, 61,000, 55,000, and 36,000 (p68, p61, p55, and p36, respectively) manifested attachment activity, while protein(s) with Mr 23,000-24,000 did not. Western blots revealed that guanidine extracts contained three bands cross-reacting with anti-bovine sialoprotein-II antibody, but the p61, p55, and p36 were negative. We conclude that cementum contains bovine sialoprotein-II and at least four other fibroblast attachment proteins, and that they do not support epithelial cell attachment.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinobacillus↗
PubMed1989

Connective tissue-associated proteins in crevicular fluid: potential markers for periodontal diseases.

Tests for periodontal disease that are able to detect both ongoing and future loss of clinical attachment would be valuable assets in determining the diagnosis and treatment of periodontal diseases. We hypothesized that connective tissue-associated proteins could be detected in crevicular fluid and would reflect the biochemical activity of the periodontium in health and disease. To test this hypothesis, crevicular fluid samples obtained from patients with various states of periodontal disease were analyzed for the presence of several connective tissue-associated proteins using a dot blot assay. Two such proteins, osteonectin and N-propeptide alpha I type I collagen, were detected in crevicular fluid samples of patients with periodontal disease. Furthermore, the amount of these proteins detected in crevicular fluid appeared to increase with increased probing depth at the sampled site. These studies indicate that measurements of connective tissue-associated proteins in crevicular fluid may prove to be a valuable tool for diagnosing periodontal diseases.

Biomarkers↗
PubMed1992

Structure, expression, and regulation of the major noncollagenous matrix proteins of bone.

The noncollagenous proteins (NCPs) that predominate the bone matrix have recently been the focus of intense investigation because of their potential influence on cell attachment, Ca2+ and hydroxyapatite binding, and the mineralization of bone tissue. With the advent of molecular biology, all of the major NCPs of bone have been cloned and their amino acid sequences completely determined. While each of the proteins has distinct structural properties, some proteins appear to be part of gene families. Examples include the small proteoglycans, decorin and biglycan, as well as the gamma carboxyglutamic acid proteins, such as matrix gla protein and osteocalcin (bone gla protein). Some of the NCPs that are clearly not members of any known gene family still share several common characteristics. One such example of this "convergent evolution" is bone sialoprotein and osteopontin. Both are highly posttranslationally modified glycoproteins that share the cell attachment amino acid sequence RGD (arginine-glycine-aspartic acid), which facilitates the attachment of bone cells in vitro, yet they are clearly not related genetically. Using cDNAs and antisera as probes, the precise temporal localization of NCP expression has been determined, and it has been shown that NCPs are produced in skeletal, and in most cases, nonskeletal tissue as well. This observation implies that the functions of the NCPs are not necessarily limited to bone tissue. Many of the promoters for these genes have been isolated and functional domains determined by a combination of chloramphenicol acetyltransferase assay, gel shift, and footprint analyses. The most extensively studied promoter in the NCP category is osteocalcin, whose sensitivity to 1,25-dihydroxycholecalciferol has been delineated in detail. Future studies on the individual and cooperative activities of the NCPs in bone are likely to involve site-directed mutagenesis of cloned DNA and a combination of in vitro and in vivo functional analyses.

Biglycan↗
PubMed1991

Molecular mechanisms in dental hard tissue mineralization.

During the period covered by this issue, over 500 papers were published in the area of biology of dental hard tissues. This review is limited to publications that focus on the organic matrix components believed to be important in the formation of dentin, cementum, and enamel. The advances made in this area for the collagen-based dental hard tissues (dentin and cementum) have been primarily in the isolation and partial characterization of the noncollagenous proteins such as proteoglycans, phosphoproteins, and proteins normally found in bone. These proteins are being studied because of their potential role for directing hydroxyapatite nucleation or crystal growth. The progress made in the enamel field has been primarily in the area of molecular biology. Enamel is quite different physically from dentin and cementum because it is formed from a noncollagenous matrix (mostly amelogenin), which is almost completely removed and replaced with hydroxyapatite. Serum proteins have now been found in all dental hard tissues including enamel. Opinions on the clinical significance of these advances are provided.

Amelogenesis↗
PubMed1990

Expression of attachment proteins during cementogenesis.

There is general agreement that during development the extracellular environment plays a critical role in controlling cell differentiation. Data generated from numerous studies support the possibility that cell attachment proteins and their corresponding cell receptors are possible candidates for this role. In particular, our studies are directed at identifying attachment proteins in mature cementum and establishing the function of these proteins during root formation. Fractionation of guanidine HCL/EDTA extracts of cementum revealed the presence of a bone-associated attachment, BSP, as well as fractions containing as of yet undetermined attachment proteins. Immunofluorescent examination of 1st molar tissues during root formation, obtained from 7 day-old mice neonates, for bone-associated attachment proteins indicated that osteopontin is expressed in the area of Hertwig's epithelial root sheath, but not in the region of the dental papillae. However, dental papillae cells, considered to have the capacity to form cementum, attached to osteopontin coated dishes, in vitro. Thus, unique attachment proteins, as well as those previously identified, were found in mature cementum and during root development. Future studies focused on identifying attachment proteins of mature cementum and determining the spatial and temporal localization of these proteins, pre- and post-cementogenesis, will provide important information necessary for establishing the function of these proteins during root development.

Animals↗
PubMed1991

Recognition of osteopontin and related peptides by an alpha v beta 3 integrin stimulates immediate cell signals in osteoclasts.

We have investigated the nature of immediate cell signals produced by occupancy of the chicken osteoclast alpha v beta 3 integrin. Synthetic osteopontin and peptides from the osteopontin and bone sialoprotein sequences containing Arg-Gly-Asp stimulated immediate reductions in osteoclast cytosolic Ca2+. The changes in cytosolic Ca2+ required the Arg-Gly-Asp sequence and were blocked by a monoclonal antibody to the alpha v beta 3 integrin, LM609. Osteoclast stimulation by the proteins through the integrin did not require immobilization since soluble peptides produced changes in cytosolic Ca2+ and inhibited osteoclast binding to bone particles and bone resorption. The decrease in cytosolic Ca2+ stimulated by osteopontin and related peptides appeared to be due to activation of a plasma membrane Ca(2+)-ATPase by calmodulin. Thus, the data suggest that ligand binding to the osteoclast alpha v beta 3 integrin results in calmodulin-dependent reduction in cytosolic Ca2+ which participates in regulation of osteoclast function.

Amino Acid Sequence↗
PubMed1988

The primary structure of a cell-binding bone sialoprotein.

We have determined the amino acid sequence of rat bone sialoprotein (BSP). The sequence deduced from a 1974-base pair cDNA encodes a protein of 320 residues, including a 16-residues long signal peptide. The mature BSP has a molecular mass of 33,600 and contains predominantly glutamic acid and glycine residues, which constitute 32% of all residues. The glutamic acid residues are typically distributed in clusters of up to 10 consecutive residues. The tissue distribution of BSP mRNA suggests that the protein may be a unique product of cells in bone tissue. BSP contains an Arg-Gly-Asp sequence, which presumably is responsible for its cell binding properties (Oldberg, A., Franzén, A., Heinegård, D., Pierschbacher, M., and Ruoslahti, E. (1988) J. Biol. Chem. 263, 19433-19436).

Amino Acid Sequence↗