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A Oldberg

Publications and source records attributed to A Oldberg.

At least 55 records · Page 3Linked to original sources
PubMed1986

Evolution of the fibronectin gene. Exon structure of cell attachment domain.

Genomic DNA coding for human fibronectin was identified from a human genomic library by screening with a cDNA clone that specifies the cell attachment domain in human fibronectin. Two clones which together provided more than 22 kilobase pairs of the fibronectin gene were isolated. The exons in this region correspond to approximately 40% of the coding region in the fibronectin gene. They code for the middle region of the polypeptide which consists of homologous repeating segments of about 90 amino acids called type III homologies. Nucleotide sequence of the portion of the gene corresponding to the cell attachment domain showed that the Arg-Gly-Asp-Ser cell attachment site is encoded within a 165-base pair exon. This exon, together with a 117-base pair exon codes for a homology unit. Analysis of the exon/intron organization in some of the neighboring homology units indicated a similar 2-exon structure. An exception to this pattern is that a single large exon codes for a type III homology unit that, due to alternative mRNA splicing, exists in some but not all fibronectin polypeptides. The introns separating the coding sequences for the type III homology units are located in conserved positions whereas the introns that interrupt the coding sequence within the units are in a variable position generating variations in the size of the homologous exons. This exon/intron organization suggests that the type III homology region of the fibronectin gene has evolved by a series of gene duplications of a primordial gene consisting of two exons. Specification of one of these homology units to the cell attachment domain has occurred within this exon/intron arrangement.

Base Sequence↗
PubMed1986

Cloning and sequence analysis of rat bone sialoprotein (osteopontin) cDNA reveals an Arg-Gly-Asp cell-binding sequence.

The primary structure of a bone-specific sialoprotein was deduced from cloned cDNA. One of the cDNA clones isolated from a rat osteosarcoma (ROS 17/2.8) phage lambda gt11 library had a 1473-base-pair-long insert that encoded a protein with 317 amino acid residues. This cDNA clone appears to represent the complete coding region of sialoprotein mRNA, including a putative AUG initiation codon and a signal peptide sequence. The amino acid sequence deduced from the cDNA contains several Ser-Xaa-Glu sequences, possibly representing attachment points for O-glycosidically linked oligosaccharides and one Asn-Xaa-Ser sequence representing a likely site for the N-glycosidically linked oligosaccharide. An interesting observation is the Gly-Arg-Gly-Asp-Ser sequence, which is identical to the cell-binding sequence identified in fibronectin. The presence of this sequence prompted us to investigate the cell-binding properties of sialoprotein. The ROS 17/2.8 cells attached and attained a spread morphology on surfaces coated with sialoprotein. We could demonstrate that synthetic Arg-Gly-Asp-containing peptides efficiently inhibited the attachment of cells to sialoprotein-coated substrates. The results show that the Arg-Gly-Asp sequence also confers cell-binding properties on bone-specific sialoprotein. To better reflect the potential function of bone sialoprotein--we propose the name "osteopontin" for this protein.

Amino Acid Sequence↗
PubMed1985

Oligosaccharides generated by an endoglucuronidase are intermediates in the intracellular degradation of heparan sulfate proteoglycans.

An intracellular heparan sulfate oligosaccharide has been identified in rat hepatocytes cultured in the presence of [35S]sulfate. Pulse-chase experiments suggest that [35S]sulfate is first incorporated into heparan sulfate proteoglycans which are subsequently converted to the low molecular weight component. The oligosaccharide (Mr 7000) contains little or no protein and is also present in rat liver homogenates. Subcellular fractionation and density gradient centrifugation in Percoll of liver homogenates demonstrated that the oligosaccharide was present in lysosomes or in particles of similar distribution and buoyant density. Structural analysis of oligosaccharides isolated from a rat liver lysosomal fraction indicate that glucuronic acid is present in the reducing end of the oligosaccharide and that this residue is preferentially linked to an N-acetylated glucosamine unit. These data suggest that the heparan sulfate oligosaccharide is generated through the action of a heparan sulfate-degrading endoglucuronidase previously found in human platelets and rat liver (Oldberg, A., Heldin, C.-H., Wasteson, A., Busch, C., and Hook, M. (1980) Biochemistry 19, 5755-5762).

Animals↗
PubMed1985

Complete amino acid sequence of human vitronectin deduced from cDNA. Similarity of cell attachment sites in vitronectin and fibronectin.

cDNA clones for vitronectin, a cell adhesion-promoting plasma and tissue protein, were isolated from a lambda gt11 library containing cDNA inserts made from human liver mRNA. The library was screened with anti-vitronectin antibodies and the positive clones were further identified with synthetic oligonucleotide probes deduced from the partial amino acid sequence of vitronectin. Nucleotide sequence analysis showed that the largest insert was 1545 bp long and contained the whole sequence corresponding to plasma vitronectin. It showed that vitronectin contains the entire 44-amino acid somatomedin B peptide at its NH2 terminus and, near its COOH terminus, a 34-amino acid glycosaminoglycan binding site in which half of the amino acids are basic residues. Three potential carbohydrate attachment sites are present in the sequence. An Arg-Gly-Asp sequence, which has previously been shown to be the cell attachment site in fibronectin, was found in vitronectin immediately after the NH2-terminal somatomedin B sequence. No other homologies with fibronectin were found. The Arg-Gly-Asp sequence appears to constitute the cell attachment site of vitronectin, since it is in the region where we have previously localized the cell attachment site, its presence correlate with cell attachment activity among the insert-coded polypeptides, and because previous results have shown that synthetic peptides containing the Arg-Gly-Asp sequence inhibit the cell attachment function of vitronectin. The discovery of an Arg-Gly-Asp cell attachment site in a protein with a known cell attachment function emphasizes the general importance of this sequence in cell recognition.

Amino Acid Sequence↗
PubMed1985

Molecular cloning and sequence analysis of a chondroitin sulfate proteoglycan cDNA.

We report the identification and DNA sequence of a chondroitin sulfate proteoglycan core protein cDNA. A cDNA clone, pPG1, was selected from a rat yolk sac tumor poly(A)+RNA-derived cDNA library by using synthetic oligonucleotides predicted from the NH2-terminal peptide sequence of the mature chondroitin sulfate proteoglycan. The resulting sequence analysis demonstrated that the 874-base-pair pPG1 clone contained the complete coding region of the mature proteoglycan core protein as well as 5' and 3' flanking sequences. The 104 amino acid proteoglycan core protein sequence reveals that the core protein is composed of three regions, the most striking of which is the central 49 amino acid region composed of alternating serine and glycine residues. This region clearly functions as the acceptor site for the attachment of chondroitin sulfate side chains. The serine-glycine repeat region is flanked by a 14 amino acid NH2-terminal region identical to the NH2-terminal sequence of the proteoglycan obtained by amino acid sequencing and a 41 amino acid COOH-terminal region. RNA transfer blot hybridizations of poly(A)+ mRNA from rat yolk sac tumor cells with nick-translated pPG1 reveal a single mRNA of approximately equal to 1300 nucleotides. The possibility of detecting mRNAs and genomic sequences for other proteoglycans with a serine-glycine repeat by using this cDNA clone is discussed.

Amino Acid Sequence↗
PubMed1984

Chondroitin/dermatan sulfate proteoglycan in human fetal membranes. Demonstration of an antigenically similar proteoglycan in fibroblasts.

A proteoglycan was isolated from fetal membranes which had been separated from human postpartum placenta. The glycosaminoglycan side chains (Mr = 55,000) were found to be composed of 75% chondroitin sulfate and 23% dermatan sulfate as determined by chondroitinase ABC or AC II digestion. NH2-terminal microsequencing of the intact proteoglycan revealed a single amino acid sequence of (sequence; see text) A rabbit antiserum raised against the intact proteoglycan reacted in sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblotting with Mr = 45,000 and 43,000 core polypeptides from chondroitinase-treated proteoglycan. Affinity-purified antibodies from this antiserum precipitated from human embryonic fibroblast culture fluid a proteoglycan which has an approximate Mr = 120,000 in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This proteoglycan has on the average two polysaccharide side chains. As defined by chondroitinase digestion, these chains consist of 66% dermatan sulfate and 20% chondroitin sulfate. Digestion of the glycosaminoglycan with chondroitinase ABC converted the proteoglycan to a Mr = 45,000 major and a Mr = 43,000 minor core polypeptide. Tissue immunofluorescence localized the proteoglycan to interstitial matrices, suggesting that it is a product of mesenchymal cells. The methods we have devised for the purification of the fetal membrane proteoglycan in chemical amounts and the antibodies we have prepared against it will allow studies on the structural and functional properties of the proteoglycan and on the expression of immunologically cross-reactive proteoglycans by various cells and tissues.

Amino Acid Sequence↗
PubMed1983

Molecular cloning and nucleotide sequence of a cDNA clone coding for the cell attachment domain in human fibronectin.

A cDNA clone coding for the cell attachment domain in human fibronectin has been isolated using synthetic oligonucleotides. Three sets of mixed tetradecamer oligonucleotides were synthesized based on amino acid sequences in the 108-amino acid cell attachment domain (Pierschbacher, M. D., Ruoslahti, E., Sundelin, J., Lind, P., and Peterson, P. A. (1982) J. Biol. Chem. 257, 9593-9597). One of these sets was made complementary to amino acids located near the COOH terminus of the cell attachment domain and synthesized as a mixture of 24 sequences. This oligonucleotide mixture was used to prime cDNA synthesis with mRNA prepared from a human fibrosarcoma as a template. A cDNA library was constructed with the oligonucleotide-primed sequences in the vector pBR322. Colonies that hybridized with the primer were isolated from the library and further identified by hybridization with oligonucleotides deduced from an amino acid sequence located 45 amino acid residues NH2-terminal of the primer sequence. One clone which hybridized to both probes was characterized in detail. The insert was 380 base pairs long and its nucleotide sequence agreed completely with the corresponding amino acid sequence of human plasma fibronectin, showing that the sequences for this region are identical in plasma fibronectin and fibronectin from a cell line. This clone should be useful for studies on the expression of fibronectins and may also allow for the production of the biologically active cell attachment domain of fibronectin in bacteria.

Amino Acid Sequence↗
PubMed1983

Immunological evidence for two distinct chondroitin sulfate proteoglycan core proteins: differential expression in cartilage matrix deficient mice.

The expression and core protein structure of two proteoglycans, the major cartilage proteoglycan isolated from a rat chondrosarcoma and a small molecular weight chondroitin sulfate proteoglycan isolated from a rat yolk sac tumor, have been compared. The cartilage proteoglycan was not detectable in the cartilage tissue of cartilage matrix deficient (cmd/cmd) neonatal mice by immunofluorescence, but the cmd cartilage did react with antibodies against the core protein of the yolk sac tumor proteoglycan. Radioimmunoassays showed that the core proteins of these proteoglycans are not cross-reactive with each other. Analysis of the core proteins by sodium dodecyl sulfate/polyacrylamide gel electrophoresis after chondroitinase ABC treatment of the proteoglycan revealed a large difference in their sizes. The cartilage proteoglycan core protein had a molecular weight of about 200,000 while the yolk sac tumor proteoglycan core protein migrated with an apparent molecular weight of about 20,000. In addition, the cultured yolk sac tumor cells that make the small proteoglycan did not react with antiserum against the cartilage proteoglycan. These results indicate that the proteoglycan isolated from the yolk sac tumor is similar to the small chondroitin sulfate proteoglycan species found in cartilage and support the existence of at least two dissimilar and genetically independent chondroitin sulfate proteoglycan core proteins.

Animals↗
PubMed1983

Effect of a proteoglycan produced by rat tumor cells on their adhesion to fibronectin-collagen substrata.

In this paper, we demonstrate that a chondroitin sulfate proteoglycan purified from a rat yolk sac tumor alters the adhesion of the tumor cells to substrata containing fibronectin or type I collagen. In the presence of the proteoglycan, these substrata were much less adhesive and did not promote cell spreading. The inhibitory effect of the proteoglycan was reversible and more pronounced during the early stages of cell attachment in vitro. The effect of the proteoglycan was selective in that it depended on the ability of the adhesive substratum to bind the proteoglycan. The proteoglycan did not inhibit the attachment of the cells to type IV collagen, which bound 12 times less proteoglycan than did type I collagen. Similarly, attachment of the cells to fibronectin fragments which did not bind the proteoglycan was not affected by it. The selective effects of the proteoglycan on the adhesion of cells to extracellular matrices suggest that such proteoglycans may promote tumor invasion by reducing interaction of cells with interstitial extracellular matrices while permitting attachment to basement membranes.

Animals↗
PubMed1982

Interactions between chondroitin sulfate proteoglycan, fibronectin, and collagen.

A proteoglycan isolated from a rat yolk sac tumor and characterized as a chondroitin sulfate proteoglycan with a smaller amount of dermatan sulfate was studied with respect to complex formation with collagen and fibronectin. The proteoglycan co-precipitated with native collagen from neutral salt solutions at 6 degrees C and 37 degrees C. Addition of fibronectin in such precipitation mixtures resulted in incorporation of fibronectin to the precipitate. Treatment of the proteoglycan with alkali to separate the glycosaminoglycan chains from the protein part and digestion of the protein part with papain greatly reduced the capacity of the proteoglycan to precipitate collagen and fibronectin. A defined extracellular matrix as represented by the complexes of collagen, proteoglycan, and fibronectin constructed here may be useful for studies on the biological effects of extracellular matrices. The multiple interactions of matrix macromolecules exemplified by these results may play a role in the formation of extracellular matrices and in the maintenance of their integrity.

Animals↗
PubMed1982

Codistribution of heparan sulfate proteoglycan, laminin, and fibronectin in the extracellular matrix of normal rat kidney cells and their coordinate absence in transformed cells.

We used antibodies raised against both a heparan sulfate proteoglycan purified from a mouse sarcoma and a chondroitin sulfate proteoglycan purified from a rat yolk sac carcinoma to study the appearance and distribution of proteoglycans in cultured cells. Normal rat kidney cells displayed a fibrillar network of immunoreactive material at the cell surface when stained with antibodies to heparan sulfate proteoglycan, while virally transformed rat kidney cells lacked such a surface network. Antibodies to chondroitin sulfate proteoglycan revealed a punctate pattern on the surface of both cell types. The distribution of these two proteoglycans was compared to that of fibronectin by double-labeling immunofluorescent staining. The heparan sulfate proteoglycan was found to codistribute with fibronectin, and fibronectin and laminin gave coincidental stainings. The distribution of chondroitin sulfate proteoglycan was not coincidental with that of fibronectin. Distinct fibers containing fibronectin but lacking chondroitin sulfate proteoglycan were observed. When the transformed cells were cultured in the presence of sodium butyrate, their morphology changed, and fibronectin, laminin, and heparan sulfate proteoglycan appeared at the cell surface in a pattern resembling that of normal cells. These results suggest that fibronectin, laminin, and heparan sulfate proteoglycan may be complexed at the cell surface. The proteoglycan may play a central role in assembly of such complexes since heparan sulfate has been shown to interact with both fibronectin and laminin.

Animals↗
PubMed1982

Molecular and biological interactions of fibronectin.

Fibronectin is a high molecular weight glycoprotein present at cell surfaces and in various body fluids. It is involved in cellular adhesion. The frequent absence of fibronectin from the surface of malignant cells may contribute to the invasive growth of tumors. To develop a better understanding of the functions of fibronectin, we have studied its structure by making use of proteolytic fragmentation and monoclonal antibodies. Fragments of plasma fibronectin which retain one or several of the affinities of intact fibronectin have been purified using affinity chromatography on collagen and heparin, and on monoclonal antibodies. These studies reveal a structure in which the different functions are located in separate protease-resistant molecular domains. The NH2-terminal domain contains the binding sites for fibrin, actin, and Staphylococci; this is followed by a collagen-binding domain, the cell attachment domain, and at the COOH-terminal end, the heparin-binding domain. These binding sites allow fibronectin to participate in multiple interactions with collagens and proteoglycans. The insoluble complexes formed by these 3 components that can be generated in vitro may represent a model for the basic structure of extracellular matrices. The role of fibronectin in such a matrix may be to contribute to the stability of the complex and to provide adhesion sites for cells. Disturbances in the interactions involving fibronectin could be potentially important to understanding diseases of connective tissues and in malignancy.

Animals↗
PubMed1981

Isolation of a chondroitin sulfate proteoglycan from a rat yolk sac tumor and immunochemical demonstration of its cell surface localization.

A proteoglycan was isolated from ascites fluid produced by a rat yolk sac tumor. The glycosaminoglycan chains of the proteoglycan are all sensitive to digestion with chondroitinase ABC and about 90% are sensitive to chondroitinase AC. The proteoglycan contains 5% protein. Amino acid analysis revealed a high content of serine and glycine which together constitute 37% of the amino acids. Glutamic acid (glutamine) and aspartic acid (asparagine) are also abundant. Galactosamine accounts for 97% of the hexosamine and the remainder is glucosamine. These characteristics indicate that the glycosaminoglycan side chains of this proteoglycan are predominantly chondroitin sulfate with a smaller amount of dermatan sulfate. Antibodies to the proteoglycan were prepared by immunization of a rabbit with purified alkali-treated proteoglycan. Affinity-purified antibodies from the antiserum immunoprecipitated (35S)sulfate-labeled radioactivity from culture media of the yolk sac tumor cells known to contain chondroitin sulfate proteoglycan. This binding was inhibited by the intact purified proteoglycan but not by proteoglycan treated with papain, suggesting dependence of the reactivity of the antibodies on integrity of the protein part of the proteoglycan. Immunofluorescence of the cultured yolk sac tumor cells revealed localization of immune reactive proteoglycans at the cell surface.

Amino Acids↗
PubMed1980

Characterization of a platelet endoglycosidase degrading heparin-like polysaccharides.

An endoglycosidase (heparitinase) acting on heparin and heparan sulfate was partially purified (approximately 300 times) from human platelets by affinity chromatography on heparan sulfate substituted Sepharose. Only heparin-like polysaccharides were degraded by the enzyme. The susceptibility of various biosynthetic heparin intermediates indicated that the platelet heparitinase had a requirement for sulfamino but not ester sulfate groups. No activity toward other uronic acid containing glycosaminoglycans could be demonstrated. Glucuronidic but not glucosaminidic linkages in heparin or heparan sulfate were attacked by the enzyme as shown by analysis of the reducing sugar moiety in oligosaccharide products. The anticoagulant activity of heparin, determined in an antithrombin III activation assay, was markedly reduced after treatment with the heparitinase. The enzyme was released from its storage site in platelets after induction of the platelet release reaction. The physiological function of platelet heparitinase is not known but may be to modify extracellular heparin-like polysaccharides in the vascular system.

Blood Platelets↗
PubMed1979

Cell-surface heparan sulfate. Isolation and characterization of a proteoglycan from rat liver membranes.

Solubilization of heparan sulfate proteoglycans from a rat liver membrane fraction was obtained by the use of the charged detergent deoxycholate or alternatively a combination of NaCl and the nonionic detergent Triton-X 100. Subsequently, proteoglycans solubilized from microsomal and plasma membrane fractions, respectively, were purified by a procedure involving gel chromatography, anion exchange chromatography, and density gradient centrifugation. The purified heparan sulfate proteoglycan had a molecular weight of about 75,000 as determined by sedimentation equilibrium analysis or gel chromatography. Molecular weights of 17,000 to 40,000 were obtained for the 125I-labeled core protein after removal of the heparan sulfate polysaccharide chains by different enzymatic and chemical methods. An average molecular weight of 14,000 was found for the polysaccharide chains released from the core protein by alkali treatment. The data are consistent with a proteoglycan structure containing four polysaccharide chains attached to the core protein. The amino acid composition of native and alkali-treated proteoglycan support the proposed proteoglycan model.

Animals↗