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M Paulsson

Publications and source records attributed to M Paulsson.

At least 91 records · Page 5Linked to original sources
PubMed1994

The cartilage proteoglycan aggregate: assembly through combined protein-carbohydrate and protein-protein interactions.

In vitro reassembled aggregates of cartilage proteoglycan (aggrecan) were studied by glycerol spraying/rotary shadowing electron microscopy and compared to the corresponding native (i.e. never dissociated) structures. In both cases a tightly packed central filament structure was observed consisting of the hyaluronate binding region (HABR) of the proteoglycan, link protein (LP) and hyaluronate (HA). This differs from earlier results where a discontinuous central filament structure was seen after spreading proteoglycan aggregates at a water/air interphase. Binding of isolated HABR to HA is random but upon addition of link protein a clustering of the HA-binding proteins is observed, indicating a cooperativity. In a fully saturated aggregate the HA is covered by a continuous protein shell consisting of HABR and LP. When added in amounts below saturation HABR and LP bind to the HA in clusters which are interrupted by free strands of HA. The proteoglycan aggregate is thus an example for a structure where a polysaccharide forms a template for a supramolecular assembly largely stabilized by protein-protein interactions.

Aggrecans↗
PubMed1994

A new nomenclature for the laminins.

The authors have adopted a new nomenclature for the laminins. They are numbered with arabic numerals in the order discovered. The previous A, B1 and B2 chains, and their isoforms, are alpha, beta and gamma, respectively, followed by an arabic numeral to identify the isoform. For example, the first laminin identified from the Engelbreth-Holm-Swarm tumor is laminin-1 with the chain composition alpha 1 beta 1 gamma 1. The genes for these chains are LAMA1, LAMB1 and LAMC1, respectively.

Animals↗
PubMed1994

Cell surface hydrophobicity and adherence to extra-cellular matrix proteins in two collections of methicillin-resistant Staphylococcus aureus.

Non-specific and specific mechanisms of adherence have been examined in two collections of methicillin-resistant Staphylococcus aureus (MRSA). Determination of hydrophobicity by salt aggregation, hydrophobicity indices and of adherence to the extra-cellular matrix proteins fibronectin, vitronectin, laminin and collagen type 1 have failed to reveal any correlation with phage-type, plasmid profile or antibiogram. Further, the strain collections, made over a period of years in two countries, differ markedly in their adherence characteristics; MRSA are heterogeneous in this respect. Such heterogeneity may explain the polarization of views on the epidemicity or 'virulence' of MRSA. With the exception of adherence to collagen a small group of methicillin sensitive S. aureus had characteristics intermediate between the two groups of MRSA.

Agglutination Tests↗
PubMed1994

Distinct and overlapping ligand specificities of the alpha 3A beta 1 and alpha 6A beta 1 integrins: recognition of laminin isoforms.

The ligand specificity of the alpha 3A beta 1 integrin was analyzed using K562 cells transfected with full-length alpha 3A cDNA and was compared with that of alpha 6A beta 1 in similarly transfected K562 cells. Clones were obtained that showed comparable surface expression of either alpha 3A beta 1 or alpha 6A beta 1 integrins. Those expressing alpha 3A beta 1 attached to and spread on immunopurified human kalinin and cellular matrices containing human kalinin, which is a particular isoform of laminin. In addition, alpha 3A transfectants adhered to bovine kidney laminins possessing a novel A chain variant. Binding to kalinin was blocked by a monoclonal antibody against the A chain constituent of kalinin and adhesion to both kalinin and kidney laminins by anti-alpha 3 and beta 1 monoclonal antibodies. The alpha 3A transfected cells bound more strongly to kalinin and bovine kidney laminins after treatment with the beta 1 stimulatory antibody TS2/16. A distinctly weaker and activation-dependent adhesion of alpha 3A transfectants was observed on human placental laminins possessing the Am chain variant (merosin), and no adhesion occurred on bovine heart laminins and murine EHS tumor laminin. Further inactive substrates were fibronectin, nidogen, and collagen types IV and VI, indicating that the alpha 3A beta 1 integrin is a much less promiscuous receptor than thought before. By contrast, alpha 6A transfected cells adhered to all laminin isoforms when stimulated with TS2/16. Adhesion also occurred only on bovine kidney laminins in the absence of TS2/16. These results demonstrate that both alpha 3A beta 1 and alpha 6A beta 1 integrins are typical laminin receptors but that their affinity and activation dependence for binding to various laminin isoforms differ considerably.

Amino Acid Sequence↗
PubMed1993

Expression and function of the cytoplasmic variants of the integrin alpha 6 subunit in transfected K562 cells. Activation-dependent adhesion and interaction with isoforms of laminin.

Two variants of the cytoplasmic domain of the integrin alpha 6 subunit have been identified (alpha 6A and alpha 6B). To determine the role of each variant in mediating cell adhesion to laminin, we have independently expressed the alpha 6A and alpha 6B subunits in K562 cells. Both variants associated with endogenous beta 1 and were present at comparable levels on the surface of transfected K562 cells. After activation with phorbol ester (phorbol 12-myristate 13-acetate; PMA) or the stimulatory anti-beta 1 antibody TS2/16, alpha 6A beta 1 as well as alpha 6B beta 1 mediated cell adhesion to laminin and more specifically to its fragment E8. Furthermore, both integrin variants interacted with the laminin isoforms kalinin and merosin. Cell adhesion to laminin isoforms was inhibited by the alpha 6-specific monoclonal antibody GoH3. PMA was less efficient in stimulating adhesion than TS2/16 and stimulated adhesion of alpha 6B transfectants better than of alpha 6A transfectants. In contrast, TS2/16 stimulated the adhesion of the alpha 6A and alpha 6B transfectants to laminin to a similar extent. These findings indicate that the cells may regulate the activation of the two alpha 6 variants independently. Activation by PMA was associated with the phosphorylation of both alpha 6A and alpha 6B subunits, but there was no relationship between the degree of phosphorylation and the ability of the transfectants to adhere to laminin since alpha 6A became phosphorylated much more strongly by PMA than alpha 6B. Thus, both alpha 6A beta 1 and alpha 6B beta 1 on K562 cells are activation-dependent receptors for different isoforms of laminin.

Cell Adhesion↗
PubMed1993

Multiple interactions between human vitronectin and Staphylococcus aureus.

Multiple interactions between human vitronectin and Staphylococcus aureus strain V8 were observed. An upward-curved Scatchard plot indicated both high-affinity binding (Kd1 = 7.4 x 10(-10) M) with 260 binding sites per bacterial cell and moderate-affinity binding (Kd2 = 7.4 x 10(-8) M) with 5240 copies per cell. Negative cooperativity of this binding was characterized by its Hill coefficient of less than unity (0.70 +/- 0.08). Up to 60% of the vitronectin-bacteria interaction was unaffected by high ionic strength (i.e., 2.4 M NaCl), and was not inhibited by highly-charged heparin oligosaccharides. Various oligosaccharides (4-20 monosaccharide units) generated by partial deaminative cleavage of heparin were found to affect vitronectin binding to S. aureus. Short-chain-length oligosaccharides increase and long oligosaccharides inhibit vitronectin binding, in accordance with direct association of these saccharides with multimeric vitronectin. A protein having a molecular mass of 60 kDa was identified as a putative high-affinity staphylococcal vitronectin-binding protein. These results indicate that interaction of multimeric vitronectin, mostly present at extracellular matrix sites with multiple recognition sites on the S. aureus surface, may contribute to bacterial colonisation.

Binding Sites↗
PubMed1993

Adhesion of staphylococci to chemically modified and native polymers, and the influence of preadsorbed fibronectin, vitronectin and fibrinogen.

A commercially available poly(ether urethane), polyethylene, and modifications of these polymers have been compared with respect to adsorption of fibronectin, fibrinogen and vitronectin. The adhesion of staphylococcal strains (characterized for ability to bind immobilized proteins, cell surface hydrophobicity and charge) was studied by bioluminescence with and without preadsorption of proteins to the surfaces. The least amount of proteins and the fewest bacteria adhered to the amphiphilic surfaces. When polymers were preincubated with plasma or albumin, lower numbers of bacteria adhered, except to Pellethane grafted with PEG 20,000, to which coagulase-negative staphylococci adhered to a higher extent.

Adsorption↗
PubMed1993

Expression of tissue transglutaminase in skeletal tissues correlates with events of terminal differentiation of chondrocytes.

Calcifying cartilages show a restricted expression of tissue transglutaminase. Immunostaining of newborn rat paw bones reveals expression only in the epiphyseal growth plate. Tissue transglutaminase appears first intracellularly in the proliferation/maturation zone and remains until calcification of the tissue in the lower hypertrophic zone. Externalization occurs before mineralization. Subsequently, the enzyme is present in the interterritorial matrix during provisional calcification and in the calcified cartilage cores of bone trabeculae. In trachea, mineralization occurring with maturation in the center of the cartilage is accompanied by expression of tissue transglutaminase at the border of the hydroxyapatite deposits. Transglutaminase activity also shows a restricted distribution in cartilage, similar to the one observed for tissue transglutaminase protein. Analysis of tissue homogenates showed that the enzyme is present in growth plate cartilage, but not in articular cartilage, and recognizes a limited set of substrate proteins. Osteonectin is coexpressed with tissue transglutaminase both in the growth plate and in calcifying tracheal cartilage and is a specific substrate for tissue transglutaminase in vitro. Tissue transglutaminase expression in skeletal tissues is strictly regulated, correlates with chondrocyte differentiation, precedes cartilage calcification, and could lead to cross-linking of the mineralizing matrix.

Animals↗
PubMed1993

Serum and tissue protein binding and cell surface properties of Staphylococcus lugdunensis.

Eleven strains of Staphylococcus lugdunensis from different clinical sources were investigated for their ability to bind 125I-labelled collagen (Cn) type I and IV, fibronectin (Fn), vitronectin (Vn), laminin (Lm), fibrinogen (Fg), thrombospondin, plasminogen (glu- and lys-form) and human IgG. All the strains bound these proteins, although a higher degree of binding was obtained for Cn types I and IV and IgG with mean values of 36%, 32% and 26% binding, respectively. In tests with proteins immobilised on latex beads in a particle agglutination assay, eight of the 11 strains bound Cn type I and seven bound Fg, whereas no strain bound immobilised IgG. Binding to immobilised Cn-I, Fg, Lm and Vn was abolished when the bacterial cells were treated with proteases or heat, indicating cell-surface receptors with protein characteristics. Cell-surface extracts of S. lugdunensis 2342 were able to totally inhibit binding of the homologous strain and S. aureus Cowan 1 to latex-immobilised proteins Cn-I, Lm, Vn, Fn and Fg. The binding of 125I-labelled Cn IV by S. lugdunensis 2342, was heat sensitive, whereas the binding to S. aureus Cowan 1 was heat resistant. The strains gave negative results in tests for the presence of protein A with a S. aureus protein A gene probe and with sensitised red blood cells. No production of heat-stable nuclease (TNase) could be detected by monoclonal antibodies against TNase or by the polymerase chain reaction with an oligonucleotide sequence from S. aureus TNase as primer.(ABSTRACT TRUNCATED AT 250 WORDS)

Agglutination Tests↗
PubMed1993

Molecular mechanisms of neural crest cell attachment and migration on types I and IV collagen.

We have examined the mechanisms involved in the interaction of avian neural crest cells with collagen types I and IV (Col I and IV) during their adhesion and migration in vitro. For this purpose native Col IV was purified from chicken tissues, characterized biochemically and ultrastructurally. Purified chicken Col I and Col IV, and various proteolytic fragments of the collagens, were used in quantitative cell attachment and migration assays in conjunction with domain-specific collagen antibodies and antibodies to avian integrin subunits. Neural crest cells do not distinguish between different macromolecular arrangements of Col I during their initial attachment, but do so during their migration, showing a clear preference for polymeric Col I. Interaction with Col I is mediated by the alpha 1 beta 1 integrin, through binding to a segment of the alpha 1(I) chain composed of fragment CNBr3. Neural crest cell attachment and migration on Col IV involves recognition of conformation-dependent sites within the triple-helical region and the noncollagenous, carboxyl-terminal NC1 domain. This recognition requires integrity of inter- and intrachain disulfide linkages and correct folding of the molecule. Moreover, there also is evidence that interaction sites within the NC1 domain may be cryptic, being exposed during migration of the cells in the intact collagen as a result of the prolonged cell-substratum contact. In contrast to Col I, neural crest cell interaction with Col IV is mediated by beta 1-class integrins other than alpha 1 beta 1.

Animals↗
PubMed1993

Expression of vitronectin and fibronectin binding by Candida albicans yeast cells.

Expression of binding to vitronectin (Vn or S-protein) and fibronectin (Fn) was common among clinical isolates of Candida albicans. Growth at 37 degrees C enhanced expression of both Vn and Fn binding. Some strains expressed higher binding after growth in liquid media and others after growth on solid media. Most strains expressed higher cell surface hydrophobicity after growth on agar media. Vn binding was less influenced by expression of cell surface hydrophobicity than Fn binding. Vn binding to yeast cells was optimal around pH 4 and Fn binding around pH 6. Binding to soluble Vn was inhibited by unlabelled Vn and to a lesser extent by Fn. Fn binding to the same C. albicans strain was inhibited by unlabelled Fn, Vn, fibrinogen and to some extent collagens. C. albicans strain 3248 expressed specific high binding of Vn, and high binding of Fn. Binding of both proteins was sensitive to heat and protease treatment, but in different ways. Vn binding differed significantly from the earlier reported Fn binding and may represent a novel type of tissue adherence.

Blood Proteins↗
PubMed1992

Proteoglycans from the swarm rat chondrosarcoma. Structure of the aggregates extracted with associative and dissociative solvents as revealed by electron microscopy.

Proteoglycan aggregates were extracted from Swarm rat chondrosarcoma tissue in the native state and compared with proteoglycan aggregates isolated dissociatively with 4 M guanidine HCl. Purified aggregates were examined with a variety of electron microscopic techniques. In some cases they showed a structure of the central filament identical to that of the link-stabilized central filament observed in earlier experiments where the separated constituents were allowed to reconstitute (Mörgelin, M., Paulsson, M., Hardingham, T. E., Heinegård, D., and Engel, J. (1988) Biochem. J. 253, 175-185). The tight packing of proteoglycan monomers along the hyaluronate with a minimum distance of 12 nm between adjacent E1 strands also could thus be confirmed for never dissociated aggregates. The results therefore show that the organization of proteoglycan aggregates assembled in vitro from the participating molecules is representative for conditions in situ. An additional structural type of central filament was observed in the preparations. This contained long stretches of free hyaluronate interspaced by short stretches of central filament with condensed arrays of link protein-proteoglycan. Chemical cross-linking in combination with low shear electron microscopical techniques showed that this discontinuous central filament structure is not an artifact of specimen preparation. The addition of suprastoichiometric amounts of exogenous link protein did not affect the central filament structure with the low packing density. Densely and loosely packed types of central filament were isolated in varying relative amounts with different associative and dissociative solvents.

Animals↗
PubMed1992

Identification of Gln726 in nidogen as the amine acceptor in transglutaminase-catalyzed cross-linking of laminin-nidogen complexes.

The laminin-nidogen complex, the most abundant noncollagenous component of basement membranes, was recently shown to be a specific substrate for tissue transglutaminase (Aeschlimann, D., and Paulsson, M. (1991) J. Biol. Chem. 266, 15308-15317). Saturation experiments to determine the number of amine acceptor site(s) indicated a single reactive Gln residue in nidogen and none in laminin. Murine nidogen was labeled with [3H]putrescine in the tissue transglutaminase-catalyzed reaction, and two major radioactively labeled fragments, T70 and T40, were isolated after limited trypsin digestion. NH2-terminal sequencing showed that T40 is contained in T70 and corresponds to the rodlike structure of nidogen, made up of epidermal growth factor-like repeats. Three radioactively labeled peptides, obtained by extensive trypsin digestion of reduced and alkylated T40, were sequenced. In all a single residue, Gln726, was found to contain label. Sequencing of additional peptides, obtained after further treatment of the largest radioactively labeled peptide with endoproteinase Asp-N, gave the same result. Gln726 is located in an exposed loop between the second and the third EGF-like repeat in nidogen. This site is also conserved in the human sequence.

Amino Acid Sequence↗
PubMed1992

Cartilage matrix proteins. An acidic oligomeric protein (COMP) detected only in cartilage.

An Mr = 524,000 oligomeric protein was isolated from bovine cartilage and designated COMP (Cartilage Oligomeric Matrix Protein). The protein is composed of disulfide-bonded subunits with an apparent Mr of 100,000 each. It is markedly anionic, probably due to its high contents of aspartic acid and glutamic acid, as well as to its substitution with negatively charged carbohydrates. COMP was found in all cartilages analyzed, but could not be detected in other tissues by enzyme-linked immunosorbent assay of guanidine HCl extracts. Within a given cartilage, COMP shows a preferential localization to the territorial matrix surrounding the chondrocytes.

Amino Acids↗
PubMed1992

Electron microscopy of native cartilage oligomeric matrix protein purified from the Swarm rat chondrosarcoma reveals a five-armed structure.

Cartilage oligomeric matrix protein was isolated in the native state from the Swarm rat chondrosarcoma. A crucial step was its selective extraction with EDTA-containing buffer. The purified protein was subjected to electron microscopy using rotary shadowing and negative stain. The images allowed the construction of a structural model. The bouquet-like protein consists of five 28-nm-long arms containing a peripheral globular domain, a flexible strand, and a central assembly domain, where the five arms meet in a cylindrical structure.

Animals↗
PubMed1992

The role of laminin in attachment, growth, and differentiation of cultured cells: a brief review.

Laminin, a major structural multidomain protein of basement membranes, has been shown to exert a variety of biological activities. Prominent among those are mediation of cell attachment as well as influences on cellular proliferation, differentiation and motility. Distinct domains of laminin have been identified which carry these activities. The active sites on laminin are recognized by cellular receptors, several of which belong to the integrin class of heterodimeric transmembrane proteins. These are in direct contact with intracellular proteins and mediate signals from the extracellular matrix to the cytoskeleton and possibly to other intracellular regulatory systems. The biological activities of laminin may be used to design optimal conditions for the expression of a differentiated phenotype of cells in culture.

Animals↗
PubMed1992

Merosin promotes cell attachment and neurite outgrowth and is a component of the neurite-promoting factor of RN22 schwannoma cells.

The laminin-like protein merosin was purified from human placenta in intact form and as pepsin fragments and compared to laminin in heparin affinity chromatography and cell binding assays. Intact merosin and a small fragment of merosin comprising the last two repeats of the heavy chain g domain bind to heparin. Intact merosin and large pepsin fragments of merosin, but not the small C-terminal fragment, mediate the attachment and spreading of several types of cells and promote neurite outgrowth from neuronal cells similar to laminin and its corresponding fragments. Cells with various integrin-type receptors for laminin attached equally well to merosin and laminin, suggesting that several of the known laminin binding receptors also bind to merosin. Antibodies to the beta 1 subunit of integrins inhibited neurite outgrowth on merosin as well as on laminin, confirming the involvement of integrin-mediated interaction of cells with both merosin and laminin. Schwannoma cells, which have previously been shown to produce a laminin-like, neurite-promoting factor, synthesize merosin in vivo and in vitro as shown by protein and mRNA analysis. The results suggest that merosin, which is the more abundant basement membrane protein in the laminin family, has properties very similar to laminin despite differences in the structure of the heavy chain. Furthermore, merosin may be identical to or a component of the neurite-promoting factors previously reported from heart, muscle, and Schwann cells.

Base Sequence↗