Monoclonal antibody EMR1a/212D recognizing site of deposition of extracellular lipid in atherosclerosis. Isolation and characterization of a cDNA clone for the antigen

Regulatory properties of vitronectin and its glycosylation in collagen fibril formation and collagen-degrading enzyme cathepsin K activity

Vitronectin (VN) is a glycoprotein found in extracellular matrix and blood. Collagen, a major extracellular matrix component in mammals, is degraded by cathepsin K (CatK), which is essential for bone resorption under acidic conditions. The relationship between VN and cathepsins has been unclear. We discovered that VN promoted collagen fibril formation and inhibited CatK activity, and observed its activation in vitro. VN accelerated collagen fibril formation at neutral pH. Collagen fibers formed with VN were in close contact with each other and appeared as scattered flat masses in scanning electron microscopy images. VN formed collagen fibers with high acid solubility and significantly inhibited CatK; the IC₅₀ was 8.1–16.6 nM and competitive, almost the same as those of human and porcine VNs. VN inhibited the autoprocessing of inactive pro-CatK from active CatK. DeN-glycosylation of VN attenuated the inhibitory effects of CatK and its autoprocessing by VN, but had little effect on acid solubilization of collagen and VN degradation via CatK. CatK inhibition is an attractive treatment approach for osteoporosis and osteoarthritis. These findings suggest that glycosylated VN is a potential biological candidate for CatK inhibition and may help to understand the molecular mechanisms of tissue re-modeling.

The vitronectin gene in rainbow trout: cloning, expression and phylogenetic analysis

Vitronectin is a major cell adhesion glycoprotein that is found in plasma and the extracellular matrix. Vitronectin consists of an N-terminal somatomedin B domain and two hemopexin-like domains and controls functions including cell adhesion, migration, haemostasis and immune defence. In order to study the molecular evolution of the complement lytic pathway regulation, we have cloned and characterized the vitronectin gene from rainbow trout (Oncorhynchus mykiss). The deduced amino acid sequence of trout vitronectin exhibits 45%, 46%, 47% and 63% identity with human, chicken, Xenopus and zebrafish orthologs, respectively. The domain architecture of the trout vitronectin, consisting of a somatomedin B domain and two hemopexin-like domains, resembles that of mammalian vitronectins. Analysis of partial genomic clones shows that trout vitronectin gene exhibits the same exon-intron organization profile as the human ortholog gene. The trout vitronectin gene is probably present as a single copy in the trout genome, showing a differential expression pattern among tissues investigated.

Identification of human scFvs targeting atherosclerotic lesions: selection by single round in vivo phage display

Our aim was to investigate by in vivo biopanning the lesions developed early in atherosclerosis and identify human antibodies that home to diseased regions. We have designed a two-step approach for a rapid isolation of human Monoclonal phage-display single-chain antibodies (MoPhabs) reactive with proteins found in lesions developed in an animal model of atherosclerosis. After a single round of in vivo biopanning, the MoPhabs were eluted from diseased sections of rabbit aorta identified by histology and NMR microscopy. MoPhabs expressed in situ were selected by subtractive colony filter screening for their capacity to recognize atherosclerotic but not normal aorta. MoPhabs selected by our method predominantly bind atherosclerotic lesions. Two of them, B3.3G and B3.GER, produced as scFv fragments, recognized an epitope present on the surface in early atherosclerotic lesions and within the intimal thickness in more complex plaques. These human MoPhabs homed to atherosclerotic lesions in ApoE(-/-) mice after in vivo injection. A protein of approximately 56 kDa recognized by B3.3G was affinity-purified and identified by mass spectrometry analysis as vitronectin. This is the first time that single round in vivo biopanning has been used to select human antibodies as candidates for diagnostic imaging and for obtaining insight into targets displayed in atherosclerotic plaques.

Plasminogen activator inhibitor type-1 inhibits insulin signaling by competing with alphavbeta3 integrin for vitronectin binding

Functional cooperation between integrins and growth factor receptors has been reported for several systems, one of which is the modulation of insulin signaling by alphavbeta3 integrin. Plasminogen activator inhibitor type-1 (PAI-1), competes with alphavbeta3 integrin for vitronectin (VN) binding. Here we report that PAI-1, in a VN-dependent manner, prevents the cooperation of alphavbeta3 integrin with insulin signaling in NIH3T3 fibroblasts, resulting in a decrease in insulin-induced protein kinase B (PKB) phosphorylation, vascular endothelial growth factor (VEGF) expression and cell migration. Insulin-induced HUVEC migration and angiotube formation was also enhanced in the presence of VN and this enhancement is inhibited by PAI-1. By using specific PAI-1 mutants with either VN binding or plasminogen activator (PA) inhibiting activities ablated, we have shown that the PAI-1-mediated interference with insulin signaling occurs through its direct interaction with VN, and not through its PA neutralizing activity. Moreover, using cells deficient for uPA receptor (uPAR) we have demonstrated that the inhibition of PAI-1 on insulin signaling is independent of uPAR-VN binding. These results constitute the first demonstration of the interaction of PAI-1 with the insulin response.

Vitronectin in the cirrhotic liver: an immunomarker of mature fibrosis

Vitronectin (Vn) is a multifunctional plasma glycoprotein produced by hepatocytes. Vn has been studied extensively as a cell adhesion molecule. However, its localization in the hepatic extracellular matrix has received relatively little attention. Cryosections of 5 normal liver samples and of 20 specimens showing posthepatitic cirrhosis were stained by the avidin-biotin complex method with a well-characterized monoclonal antibody to Vn. The extent and intensity of immunostaining were assessed semiquantitatively (0, no staining; 1+, weak focal staining; 2+, strong focal staining; 3+, strong diffuse staining). Paraffin sections from the same samples were stained with Masson trichrome (MT) and Shikata orcein (Or) methods. Frozen samples from selected cases were analyzed by Western blotting. In the normal liver, 3+ staining was limited to portal vessels. The portal tract connective tissue showed minimal staining (0 to 1+). Cirrhotic septa showed strong staining (2+). Septa lacking significant inflammation and composed of dense connective tissue, as indicated by MT and Or stains, showed the strongest Vn reactions (3+). Immunoblotting data strongly correlated with Vn increase in cirrhotic livers. Vn immunoreactivity is markedly increased in the cirrhotic liver matrix, regardless of the documented decrease in plasma Vn. Binding to collagen, elastin, and proteoglycans is the current favored mechanism of Vn deposition in tissues. Previous studies in cirrhotic patients showed increased affinity of plasma Vn to collagen. Vn is also increased in aged skin, associated with dermal elastic fibers. In other tissues, Vn deposition reflects chronicity of injury. Therefore, Vn immunoreactivity in liver can be considered a marker of fibrosis, especially of chronic/mature fibrosis, paralleling previous observations on enhanced orcein staining of cirrhotic septa. Immunolabeling of biopsy specimens with Vn and tenascin, a marker of ongoing remodeling or recently formed fibrous tissue, could be diagnostically helpful.

Presence of phospholipid-neutral lipid complex structures in atherosclerotic lesions as detected by a novel monoclonal antibody

A novel monoclonal antibody (ASH1a/256C) that recognizes atherosclerotic lesions in human and Watanabe heritable hyperlipidemic (WHHL) rabbit aortae is described. When (123)I-labeled ASH1a/256C antibody is injected intravenously into WHHL rabbits, it associates specifically with fatty streaks on the aorta. The antigen recognized by the antibody is lipid, based on extraction with chloroform and methanol from WHHL rabbit tissues. The antigen, purified by high performance liquid chromatography, was shown to be phosphatidylcholine (PC), which contains unsaturated fatty acyl groups based on analyses utilizing (1)H and (13)C nuclear magnetic resonance, Fourier transfer-infrared spectrum, and mass spectrometry. The antibody did not react with other classes of phospholipids or neutral lipids when tested using an enzyme-linked immunosorbent assay. When PC was mixed with either cholesterol, cholesteryl ester, or triacylglycerol, however, the reactivity of the antibody to PC increased up to 8-fold. Homogenates of aorta tissue obtained from normal and WHHL rabbits were fractionated using sucrose density gradient ultracentrifugation in which neutral lipid droplets, cellular membranes, and proteins are separated. The phospholipid content in cellular membrane fractions from WHHL rabbits was twice as high as that of normal rabbits, and there was an enormous difference in the antigenic activity in these fractions. The content of cholesterol in the cellular membrane fraction of WHHL rabbits was approximately 50 times higher than that of normal rabbits. Addition of neutral lipids to the cellular membrane fraction of normal rabbit markedly increased the antigenic activity. Atheromatous lesions in thickened WHHL rabbit aortic intima that were rich in lipid droplets were stained positively with ASH1a/256C immunohistochemically. These results strongly suggest that PC-neutral lipid complex domains are formed in atherosclerotic lesions.

Vitronectin regulates smooth muscle contractility via alphav and beta1 integrin

Previous work from this laboratory has established a method for maintaining physiological contractility of dissociated avian smooth muscle in a defined medium at low density. The present report emphasizes the dramatic potency of serum to alter smooth muscle phenotype and induce a loss of contractility. Vitronectin, a molecule purified from plasma, mimicked these effects of serum via an integrin that is RGD-sensitive. Studies utilizing blocking antibodies against vitronectin demonstrated that the presence of this specific adhesion molecule was necessary for the serum-induced loss of contractility. Based on the actions of function-blocking antibodies and RGD-containing peptides, the integrin alphavbeta1 appears to be the primary receptor involved in vitronectin's ability to induce phenotypic transformation in amniotic smooth muscle. The influence of vitronectin on smooth muscle contractility is particularly relevant, because this molecule is abundant in whole blood and plasma (approx. 400 microg/ml). The results suggest that smooth muscle needs to be continually protected from normal blood constituents in vivo. The implications of these results for smooth muscle-related diseases like atherosclerosis, restenosis and Kaposi's sarcoma are discussed.

Vitronectin expression and interaction with receptors in smooth muscle cells from human atheromatous plaque

Vitronectin (VN) is a plasma glycoprotein that promotes cell attachment and induces migration of human smooth muscle cells (SMCs) in culture. VN has been observed to accumulate in human atherosclerotic plaques, although its origin and role in atherosclerosis are not yet established. In the present experiments, synthesis of VN by intimal cells and its colocalization with receptors, alphavbeta3 and alphavbeta5, were studied by in situ hybridization and immunohistochemistry on 15 human atherosclerotic plaques from carotid arteries obtained after surgery. Strong VN protein and mRNA expression was observed in the intima and in the media. In the intima, VN mRNA expression was colocalized with SMCs, indicating that these cells produce VN, which may account for its accumulation in atherosclerotic plaques. In SMCs in culture, immunoprecipitation after metabolic labeling demonstrated that human SMCs do synthesize vitronectin. Confocal microscopic examination showed that VN colocalized with its receptors, alphavbeta3 and alphavbeta5, in the atherosclerotic intima. However, the distribution of the VN receptors on SMCs in culture in contact with VN was different. These observations suggest that VN plays various parts in atherogenesis via different SMC membrane receptors.

Vitronectin is expressed in the ventral region of the neural tube and promotes the differentiation of motor neurons

The extracellular matrix protein vitronectin and its mRNA are present in the embryonic chick notochord, floor plate and in the ventral neural tube at the time position of motor neuron generation. When added to cultures of neural tube explants of developmental stage 9, vitronectin promotes the generation of motor neurons in the absence of either notochord or exogenously added Sonic hedgehog. Conversely, the neutralisation of endogenous vitronectin with antibodies inhibits over 90% motor neuron differentiation in co-cultured neural tube/notochord explants, neural tube explants cultured in the presence of Sonic hedgehog, and in committed (stage 13) neural tube explants. Furthermore, treatment of embryos with anti-vitronectin antibodies results in a substantial and specific reduction in the number of motor neurons generated in vivo. These results demonstrate that vitronectin stimulates the differentiation of motor neurons in vitro and in vivo. Since the treatment of stage 9 neural tube explants with Sonic hedgehog resulted in induction of vitronectin mRNA expression before the expression of floor plate markers, we conclude that vitronectin may act either as a downstream effector in the signalling cascade induced by Sonic hedgehog, or as a synergistic factor that increases Shh-induced motor neuron differentiation.

The role of carboxy-terminal glycosaminoglycan-binding domain of vitronectin in cytoskeletal organization and migration of endothelial cells

Vitronectin is a major cell adhesion molecule present in the subendothelial matrix that mediates the attachment and spreading of a variety of cells. The carboxy-terminal end of vitronectin has a consensus sequence for glycosaminoglycan-binding. To define the functional role of this domain, we generated fragments of vitronectin that lack the glycosaminoglycan-binding domain by formic acid cleavage of plasma-derived vitronectin. In addition, we also generated similar recombinant fragments of vitronectin as glutathione S-transferase fusion proteins in E. coli. These fragments were tested for their ability to support the adhesion of human umbilical vein endothelial cells. These fragments promoted endothelial cell adhesion, reaching half maximal activity at 2-5 micrograms/well compared to plasma-derived vitronectin which reached at 0.2 micrograms/well. However, the cells that adhered to these fragments did not develop well-formed focal adhesion plaques and actin stress fibers. In addition, these fragments were poorly chemotactic for endothelial cell migration when compared to intact plasma-derived vitronectin in a modified Boyden chamber assay. The present studies show that carboxy-terminal glycosaminoglycan-binding domain of vitronectin is essential for proper cytoskeletal organization and migration of endothelial cells on vitronectin substratum.

Nectinepsin: a new extracellular matrix protein of the pexin family. Characterization of a novel cDNA encoding a protein with an RGD cell binding motif

We report the isolation and characterization of a novel cDNA from quail neuroretina encoding a putative protein named nectinepsin. The nectinepsin cDNA identifies a major 2.2-kilobase mRNA that is detected from ED 5 in neuroretina and is increasingly abundant during embryonic development. A nectinepsin mRNA is also found in quail liver, brain, and intestine and in mouse retina. The deduced nectinepsin amino acid sequence contains the RGD cell binding motif of integrin ligands. Furthermore, nectinepsin shares substantial homologies with vitronectin and structural protein similarities with most of the matricial metalloproteases. However, the presence of a specific sequence and the lack of heparin and collagen binding domains of the vitronectin indicate that nectinepsin is a new extracellular matrix protein. Furthermore, genomic Southern blot studies suggest that nectinepsin and vitronectin are encoded by different genes. Western blot analysis with an anti-human vitronectin antiserum revealed, in addition to the 65- and 70-kDa vitronectin bands, an immunoreactive protein of about 54 kDa in all tissues containing nectinepsin mRNA. It seems likely that the form of vitronectin found in chick egg yolk plasma by Nagano et al. ((1992) J. Biol. Chem. 267, 24863-24870) is the protein that corresponds to the nectinepsin cDNA. This new protein could be an important molecule involved in the early steps of the development.

Structural and functional analysis of the plasminogen activator inhibitor-1 binding motif in the somatomedin B domain of vitronectin

Plasminogen activator inhibitor 1 (PAI-1) binds to the somatomedin B (SMB) domain of vitronectin (VN), a domain present in at least seven other proteins. In this study, we investigate the PAI-1 binding activity of these SMB homologs and attempt to more specifically localize the PAI-1 binding site within this domain. SMBVN and several of its homologs were expressed in Escherichia coli, purified, and tested for PAI-1 binding activity in a competitive ligand binding assay. Although recombinant SMBVN was fully active in this assay, none of the homologs bound to PAI-1 or competed with VN for PAI-1 binding. These inactive homologs are structurally related to SMBVN, having 33-45% sequence identity and containing all 8 cysteines at conserved positions. Thus, homolog-scanning experiments were conducted by exchanging progressively larger portions of the NH2- or COOH-terminal regions of active SMBVN with the corresponding regions of the inactive homologs. These experiments revealed that the minimum PAI-1-binding sequence was present in the central region (residues 12-30) of SMBVN. Alanine scanning mutagenesis further demonstrated that each of the 8 cysteines as well as Gly12, Asp22, Leu24, Try27, Tyr28, and Asp34 were critical for PAI-1 binding and were required to stabilize PAI-1 activity. These results indicate that the PAI-1 binding motif is localized to residues 12-30 of SMBVN and suggest that this motif is anchored in the active conformation by disulfide bonds.

Structures of the N-linked oligosaccharides on human plasma vitronectin

The structures of N-linked oligosaccharides present on human plasma vitronectin were elucidated. Oligosaccharides were released from the vitronectin by N-glycosidase F digestion and tagged with 2-aminopyridine; the pyridylamino-oligosaccharides were then fractionated by anion-exchange and reverse-phase HPLC. Ten major pyridylamino-oligosaccharides were isolated. The linkages and locations of sialic acid residues were determined by desialylation with Salmonella sialidase in combination with acid. The asialo forms were then analyzed by two-dimensional sugar mapping, component sugar analysis and 400-MHz 1H-NMR spectroscopy. The major oligosaccharides of human vitronectin were of the diantennary N-acetyllactosamine type, with a lesser amount of the tri- and a small amount of the mono-antennary type, to which 1-3 mol sialic acid residues were linked, mostly through alpha 2-6 linkages, although alpha 2-3 linkages were also present. The possibility that several binding activities of vitronectin can be ascribed to its glycan moiety was discussed, based on the specific features of the N-linked oligosaccharides on human vitronectin revealed here.

Constitutive alpha V beta 3 integrin-mediated adhesion of human lymphoid B cells to vitronectin substrate

Adherence to cells and matrices participates in lymphocyte migration and tissue localization and contributes to the regulation of growth and differentiation of the lymphoid cells. The adherence is mainly mediated by three families of cell-surface proteins: integrins, immunoglobulin (Ig)-related molecules, and selectins. Integrins recognize Ig-related molecules such as ICAMs as well as fibronectin (FN), vitronectin (VN), and other matrix proteins. In this study, the in vitro adhesive properties of two Epstein-Barr virus-carrying B lymphoblastoid cell lines, IB-4 and NAD-20, were compared. IB-4 cells grow as a monolayer in contrast to NAD-20 cells, which grow as cell clusters. IB-4 cells were found to adhere to the tissue culture vessel through a component of the fetal bovine serum. By using blocking monoclonal antibodies to cell-surface molecules and serum proteins, IB-4 cells were found to use alpha V beta 3 integrin (CD51/CD61) and serum VN as the adhesive molecules. alpha V beta 3 integrin also mediated adhesion of IB-4 cells to human serum VN and to purified VN and FN. This constitutive adherence was not enhanced by phorbol ester treatment and was inhibited by RGD-containing peptides, in contrast to the homotypic adhesion of NAD-20 cells, which was mediated by beta 2 integrin CD11a/CD18 and its ligand ICAM-1 (CD54). Since VN is a component of both lymphoid tissue matrix and plasma, adhesion to this protein may affect functions and activities of B lymphocytes.

Structures of the N-linked oligosaccharides on porcine plasma vitronectin

The structures of N-linked oligosaccharides, especially the distribution of sialic acid species, present on porcine plasma vitronectin were elucidated. Oligosaccharides were released from the vitronectin by N-glycosidase F digestion and tagged with 2-aminopyridine, and the pyridylamino-oligosaccharides were fractionated by anion-exchange and reverse-phase HPLC. Nine major pyridyl-amino-oligosaccharides were isolated. The linkages and locations of sialic acids were determined by a novel approach involving desialylation with Salmonella sialidase in combination with acid desialylation. After desialylation, the asialo-forms were analyzed by two-dimensional sugar mapping, component sugar analysis and 400-MHz 1H-NMR spectroscopy. The major oligosaccharides of porcine vitronectin were of the fucosylated biantennary type, with a small amount of the triantennary N-acetyllactosamine type, to which 1-3 mol sialic acids was linked. Sialic acids were linked predominantly through alpha 2-6 linkages, although alpha 2-3 linkages were also present, and fucose was linked to the innermost N-acetylglucosamine through an alpha 1-6 linkage. It was found that every pyridylamino-oligosaccharide population contained N-glycolylneuraminic acid and N-acetylneuraminic acid in a molar ratio of 1:2-9, and that N-glycolylneuraminic acids were located predominantly on the Man alpha 1-6 arm.

Organization of the gene encoding mouse vitronectin

The gene (Vn) encoding the mouse vitronectin was isolated and its nucleotide sequence determined. The gene covers approximately 3 kb of genomic DNA. Alignment of the genomic sequence with that of the cDNA revealed that Vn consists of eight exons, interrupted by seven introns ranging in size from 78 to 723 bp.

Potentiation by hypercholesterolemia of the induction of aortic intramural synthesis of plasminogen activator inhibitor type 1 by endothelial injury

Accumulation of plasminogen activator inhibitor type 1 (PAI-1) in the arterial wall may accelerate atherogenesis by inhibiting fibrinolysis, diminishing proteolysis of extracellular matrix proteins, or modifying migration of vascular smooth muscle cells. Increased intramural expression of the PAI-1 gene is induced by thrombosis. To determine whether it occurs also in response to a sustained mechanical insult to endothelium, hypercholesterolemia, or both, rabbits were subjected to sustained aortic injury induced by implantation of indwelling polyethylene tubing, to hyperlipidemia induced by cholesterol and peanut oil feeding over a period of 8 weeks, or both. Sustained vascular injury alone did not increase plasma PAI-1. However, hypercholesterolemia with or without mechanically induced vascular injury increased plasma PAI-1 twofold. The expression of PAI-1 mRNA in aorta (Northern blots) was significantly increased when vascular injury was combined with hyperlipidemia. In situ hybridization showed that the increase with mechanical injury alone occurred in endothelial cells covering the neointima (positive for factor VIII and thrombomodulin), in abnormally differentiated vascular smooth muscle cells (positive for embryonic myosin heavy chain), and in macrophages (positive for the RAM-11 anti-macrophage antibody). Qualitatively similar but much more marked increases in PAI-1 gene expression were seen when arterial injury was accompanied by hypercholesterolemia. Neither vitronectin, known to stabilize PAI-1, nor vitronectin mRNA increased in liver. However, immunocytochemistry and Western blots demonstrated marked aortic accumulation of vitronectin protein with hyperlipidemia, particularly in subendothelial fibrotic regions, accompanied by increased neointimal vitronectin mRNA as shown by in situ hybridization. These results suggest that increased synthesis and stabilization of vascular PAI-1 may potentiate accumulation of extracellular matrix, thereby accelerating atherosclerosis.

Identification of the plasminogen activator inhibitor-1 binding heptapeptide in vitronectin

We have shown that a heptapeptide which resides in the middle part of vitronectin (VN) is responsible for binding to plasminogen activator inhibitor-1 (PAI-1). A single PAI-1 binding peptide was isolated from human VN after limited proteolysis with protease V8. The amino acid sequence of the fragment corresponded to residues Gly-115-Glu-121 of VN. A murine monoclonal antibody (JYV-1) raised against human VN bond to the same fragment and inhibited binding of PAI-1 to VN. A synthetic peptide (V-115), comprising residues Gly-115-Glu-121 of human VN, competed with VN for both PAI-1 and JYV-1 in a dose-dependent manner. Synthetic peptide V-111 (Ser-111-Glu-121) had a stronger inhibitory effect than V-115 on binding of PAI-1 or JYV-1 to VN. V-111 also inhibited the binding of human PAI-1 to mouse and rabbit VN. The functional half-life of PAI-1 activity was prolonged approximately 2-fold in the presence of V-111 (1 mM). This stabilizing effect of V-111 was equivalent to intact VN, although a 1000-fold higher molar concentration of V-111 over VN was required. These data indicated that VN residues Gly-115-Glu-121 contain a PAI-1 binding site.

Heat and autoclave resistance of cell-spreading activity of vitronectin

We have investigated the heat- and autoclave-resistant properties of the cell-spreading activity of vitronectin, a cell-spreading glycoprotein in animal blood plasma. Vitronectin heated at 100 degrees C for 10 min or autoclaved at 121 degrees C at 1.2 kg/cm2 for 20 min retained the same cell-spreading activity as native vitronectin. In contrast, fibronectin and type-I collagen treated in the same way lost their activity almost completely. GRGDSP remarkably inhibited the cell-spreading activity of native, heated and autoclaved vitronectins. GRGESP did not inhibit the activity of native vitronectin, but, unexpectedly, partially inhibited the activity of both heated and autoclaved vitronectins. In SDS-polyacrylamide gel analysis under reducing conditions, vitronectin heated at 100 degrees C migrated mainly as a monomer, but autoclaved vitronectin migrated at both the top and front of the gel instead of at the position of the monomer. The change in molecular size during the heat- and autoclave treatments was partially prevented by adding 10 mM dithiothreitol or 2% 2-mercaptoethanol to the protein solution.

Roles for the extracellular matrix in plant development and pollination: a special case of cell movement in plants

Pattern formation in plants is now thought to be primarily dependent on positional information during development. We discuss the prevalent theories on how position is deciphered by cells in an organism and highlight the recent advances implicating molecules of the cell wall or extracellular matrix (ECM) in this process. We compare the functions of the ECM in plants and animals and describe the various cell and substrate adhesion molecules of the animal ECM which play a role in morphogenesis and cell movement. We propose that analogous molecules may occur in plants and provide evidence for the presence of a substrate adhesion molecule like vitronectin in plants and algae. We provide a model for how substrate adhesion molecules may be involved in a special case of cell movement in plants, pollination.

Accumulation of cholesteryl ester in atherosclerotic lesions

This article reviews aspects of the molecular pathology of cholesteryl ester accumulation in atherosclerotic lesions. 1. Transcytosis of lipoproteins through a cultured endothelial monolayer. 2. Effects of platelets and PGI2 on intercellular transport of endothelial cells. 3. Transformation of macrophages to foam cells. 4. Cholesteryl ester deposition in the extracellular space of atherosclerotic lesions. The development and use of novel monoclonal antibodies recognizing atherosclerotic lesions and peroxidized lipoproteins prepared from then are also discussed.

Activation of the collagen-binding of endogenous serum vitronectin by heating, urea and glycosaminoglycans

The present study describes that the collagen-binding activity of vitronectin in human serum increases by treatment with heparin, heating and urea. Vitronectin purified from human serum was bound to native collagen, whereas endogenous vitronectin in the serum was not. We have examined the conditions to change the collagen-binding activity of endogenous vitronectin. Endogenous vitronectin in human serum became considerably bound to collagen when the serum was boiled in 4-8 M urea for 5 min and mixed with heparin (0.5-5 micrograms/ml). Each treatment of heating, urea or heparin alone, and any combination of the two factors, inefficiently activated the binding. Dextran sulfate could substitute for heparin, but dermatan sulfate, keratan sulfate, chondroitin sulfate A and C, heparan sulfate and hyaluronan could not. Possible explanations for the activation of endogenous vitronectin are discussed.

Vitronectin diversity in evolution but uniformity in ligand binding and size of the core polypeptide

We isolated vitronectins from the plasma or sera of 14 animal species including mouse and rat by heparin affinity chromatography. They cross-reacted with anti-vitronectin antibody and their amino terminal sequences showed strong homology. They also promoted spreading of BHK cells and were bound to heparin and collagen in the same way. Therefore, these properties appear to be essential for vitronectin function. However, the apparent molecular weights of these vitronectins varied considerable from 59 to 78 kDa in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). In addition, the number of bands also varied from 1 to 3. To search for the uniformity of vitronectin polypeptide, vitronectins were deglycosylated and examined by Ferguson plot analysis. The size of the polypeptide portion of vitronectins was estimated to range from 40 to 57 kDa which was 19-26 kDa smaller than original values. Supposing a possible cleavage site at 5-13 kDa far from the carboxyl terminus, all vitronectin polypeptides were speculated to be synthesized de novo in the size range of 50-57 kDa. Proteins reacting with anti-vitronectin antibody were also detected on the immunoblot of 13 more species including Drosophila and Physarum. Almost all of these vitronectin-like proteins showed marked species-specific variations in their apparent molecular weights from 51 to 96 kDa in SDS-PAGE.

Physarum vitronectin-like protein: An ArgGlyAsp-dependent cell-spreading protein with a distinct NH2-terminal sequence

A 70-kDa protein cross-reacted with anti-bovine vitronectin was isolated from slime mold Physarum polycephalum. The NH2-terminal amino acid sequence of the protein, referred to as Physarum vitronectin-like protein, did not share any homology with those of animal vitronectins. It had cell-spreading activity, which was specifically inhibited by an Arg-Gly-Asp (RGD)-containing peptide.

Homology of placental protein 11 and pea seed albumin 2 with vitronectin

Vitronectin (complement S-protein), a plasma and tissue glycoprotein of 75 kDa, shares the amino-terminal somatomedin B domain with the membrane glycoprotein PC1 of plasma cells and several hemopexin-type repeats with hemopexin and the non-catalytic carboxy-terminal domain of collagenases. It serves as a ligand for certain integrin receptors, binds to distinct members of the serpin family and inhibits the pore-forming cytolytic reaction of the terminal complement pathway. Computer-assisted data base searches revealed the presence of a single somatomedin B domain in the recently cloned placental protein 11, and four hemopexin-type repeats in the cytosolic plant protein PA2, the major albumin of pea seeds, whose function is unknown. Our finding shows that hemopexin-type repeats are present in extracellular as well as in cytosolic proteins and most likely originated before the divergence of the animal and plant kindoms.