scholarly journals A novel role for the integrin-binding III-10 module in fibronectin matrix assembly.

1996 ◽  
Vol 133 (2) ◽  
pp. 431-444 ◽  
Author(s):  
D C Hocking ◽  
R K Smith ◽  
P J McKeown-Longo
Keyword(s):  
Binding Site ◽  
Wound Repair ◽  
Solid Phase ◽  
Focal Adhesions ◽  
Amino Terminus ◽  
Matrix Assembly ◽  
Amino Terminal ◽  
Fibronectin Matrix ◽  
Beta 1 Integrin ◽  
Rgd Site

Fibronectin matrix assembly is a cell-dependent process which is upregulated in tissues at various times during development and wound repair to support the functions of cell adhesion, migration, and differentiation. Previous studies have demonstrated that the alpha 5 beta 1 integrin and fibronectin's amino terminus and III-1 module are important in fibronectin polymerization. We have recently shown that fibronectin's III-1 module contains a conformationally sensitive binding site for fibronectin's amino terminus (Hocking, D.C., J. Sottile, and P.J. McKeown-Longo. 1994. J. Biol. Chem. 269: 19183-19191). The present study was undertaken to define the relationship between the alpha 5 beta 1 integrin and fibronectin polymerization. Solid phase binding assays using recombinant III-10 and III-1 modules of human plasma fibronectin indicated that the III-10 module contains a conformation-dependent binding site for the III-1 module of fibronectin. Unfolded III-10 could support the formation of a ternary complex containing both III-1 and the amino-terminal 70-kD fragment, suggesting that the III-1 module can support the simultaneous binding of III-10 and 70 kD. Both unfolded III-10 and unfolded III-1 could support fibronectin binding, but only III-10 could promote the formation of disulfide-bonded multimers of fibronectin in the absence of cells. III-10-dependent multimer formation was inhibited by both the anti-III-1 monoclonal antibody, 9D2, and amino-terminal fragments of fibronectin. A fragment of III-10, termed III-10/A, was able to block matrix assembly in fibroblast monolayers. Similar results were obtained using the III-10A/RGE fragment, in which the RGD site had been mutated to RGE, indicating that III-I0/A was blocking matrix assembly by a mechanism distinct from disruption of integrin binding. Texas red-conjugated recombinant III-1,2 localized to beta 1-containing sites of focal adhesions on cells plated on fibronectin or the III-9,10 modules of fibronectin. Monoclonal antibodies against the III-1 or the III-9,10 modules of fibronectin blocked binding of III-1,2 to cells without disrupting focal adhesions. These data suggest that a role of the alpha 5 beta 1 integrin in matrix assembly is to regulate a series of sequential self-interactions which result in the polymerization of fibronectin.

Fibronectin matrix assembly enhances adhesion-dependent cell growth

1998 ◽  
Vol 111 (19) ◽  
pp. 2933-2943 ◽  
Author(s):  
J. Sottile ◽  
D.C. Hocking ◽  
P.J. Swiatek
Keyword(s):  
Extracellular Matrix ◽  
Cell Growth ◽  
Wound Repair ◽  
Focal Adhesions ◽  
Specific Cell ◽  
Embryonic Cells ◽  
Matrix Assembly ◽  
Cell Functions ◽  
Fibronectin Matrix ◽  
Adhesive Interactions

Cell growth control in non-transformed cells depends, in part, on adhesive interactions with the extracellular matrix. Following injury, excess or altered fibronectin deposition into the extracellular matrix may contribute to the pathogenesis of fibrosis and atherosclerosis by triggering changes in specific cell functions associated with wound repair, including cell proliferation and migration. To assess the role of fibronectin polymerization on cell growth, we isolated mouse embryonic cells that lack endogenous fibronectin (fibronectin-null cells) and established them in culture under serum-free conditions. These fibronectin-null cells do not produce any detectable fibronectin, but are capable of assembling a fibronectin matrix when cultured in the presence of exogenously added fibronectin. Our data indicate that adhesion-dependent growth in fibronectin-null cells is dramatically increased (>2-5x) by culturing cells in the presence of fibronectin. This fibronectin-induced cell growth was blocked by inhibiting fibronectin matrix assembly. Arg-Gly-Asp peptides or fragments of fibronectin that contain the Arg-Gly-Asp cell binding site promoted clustering of the (α)5beta1 integrin in focal adhesions, but did not enhance cell growth. These data indicate that the polymerization of fibronectin into the extracellular matrix positively regulates cell growth, and that occupancy and clustering of fibronectin-binding integrins alone are not sufficient to trigger increased cell growth.

scholarly journals The alpha v beta 1 integrin functions as a fibronectin receptor but does not support fibronectin matrix assembly and cell migration on fibronectin

1993 ◽  
Vol 122 (1) ◽  
pp. 235-242 ◽  
Author(s):  
Z Zhang ◽  
AO Morla ◽  
K Vuori ◽  
JS Bauer ◽  
RL Juliano ◽  
...  
Keyword(s):  
Cell Migration ◽  
Cell Attachment ◽  
Focal Adhesions ◽  
Cho Cell ◽  
Matrix Assembly ◽  
Fibronectin Receptor ◽  
Fibronectin Matrix ◽  
Beta 1 Integrin ◽  
Fibronectin Binding ◽  
Coated Surfaces

The fibronectin receptor, alpha 5 beta 1, has been shown to be required for fibronectin matrix assembly and plays an important role in cell migration on fibronectin. However, it is not clear whether other fibronectin binding integrins can take the place of alpha 5 beta 1 during matrix assembly and cell migration. To test this, we expressed the human alpha v subunit in the CHO cell line CHO-B2 that lacks the alpha 5 subunit. We found that the human alpha v combined with CHO cell beta 1 to form the integrin alpha v beta 1. Cells that expressed alpha v beta 1 attached to and spread well on fibronectin-coated dishes, but did so less well on vitronectin-coated dishes. This, along with other data, indicated that alpha v beta 1 functions as a fibronectin receptor in CHO-B2 cells. The alpha v beta 1-expressing cells failed to produce a fibronectin matrix or to migrate on fibronectin, although the same cells transfected with alpha 5 do produce a matrix and migrate on fibronectin. The affinity of the alpha v beta 1-expressing cells for fibronectin was fourfold lower than that of the alpha 5 beta 1-expressing cells. In addition, alpha v beta 1 was distributed diffusely throughout the cell surface, whereas alpha 5 beta 1 was localized to focal adhesions when cells were seeded onto fibronectin-coated surfaces. Thus, of the two fibronectin receptors, alpha v beta 1 and alpha 5 beta 1, only alpha 5 beta 1 supports fibronectin matrix assembly and promotes cell migration on fibronectin in the CHO-B2 cells. Possible reasons for this difference in the activities of alpha v beta 1 and alpha 5 beta 1 include the lower affinity of alpha v beta 1 for fibronectin and the failure of this integrin to localize in adhesion plaques on a fibronectin substrate. These results show that two integrins with similar ligand specificities and cell attachment functions may be quite different in their ability to support fibronectin matrix assembly and cell motility on fibronectin.

scholarly journals Staphylococcus aureus Protein A Recognizes Platelet gC1qR/p33: a Novel Mechanism for Staphylococcal Interactions with Platelets

2000 ◽  
Vol 68 (4) ◽  
pp. 2061-2068 ◽  
Author(s):  
Truc Nguyen ◽  
Berhane Ghebrehiwet ◽  
Ellinor I. B. Peerschke
Keyword(s):  
Staphylococcus Aureus ◽  
Binding Site ◽  
Soluble Protein ◽  
Molecular Mechanisms ◽  
Solid Phase ◽  
Specific Binding ◽  
Protein A ◽  
Alpha Helix ◽  
Enzyme Linked Immunosorbent Assay ◽  
Amino Terminal

ABSTRACT The adhesion of Staphylococcus aureus to platelets is a major determinant of virulence in the pathogenesis of endocarditis. Molecular mechanisms mediating S. aureus interactions with platelets, however, are incompletely understood. The present study describes the interaction between S. aureus protein A and gC1qR/p33, a multifunctional, ubiquitously distributed cellular protein, initially described as a binding site for the globular heads of C1q. Suspensions of fixed S. aureus or purified protein A, chemically cross-linked to agarose support beads, were found to capture native gC1qR from whole platelets. Moreover, biotinylated protein A bound specifically to fixed, adherent, human platelets. This interaction was inhibited by unlabeled protein A, soluble recombinant gC1qR (rgC1qR), or anti-gC1qR antibody F(ab′)2 fragments. The interaction between protein A and platelet gC1qR was underscored by studies illustrating preferential recognition of the protein A-bearing S. aureus Cowan I strain by gC1qR compared to recognition of the protein A-deficient Wood 46 strain, as well as inhibition of S. aureus Cowan I strain adhesion to immobilized platelets by soluble protein A. Further characterization of the protein A-gC1qR interaction by solid-phase enzyme-linked immunosorbent assay techniques measuring biotinylated gC1qR binding to immobilized protein A revealed specific binding that was inhibited by soluble protein A with a 50% inhibitory concentration of (3.3 ± 0.7) × 10−7 M (mean ± standard deviation; n = 3). Rabbit immunoglobulin G (IgG) also prevented gC1qR-protein A interactions, and inactivation of protein A tyrosil residues by hyperiodination, previously reported to prevent the binding of IgG Fc, but not Fab, domains to protein A, abrogated gC1qR binding. These results suggest similar protein A structural requirements for gC1qR and IgG Fc binding. Further studies of structure and function using a truncated gC1qR mutant lacking amino acids 74 to 95 demonstrated that the protein A binding domain lies outside of the gC1qR amino-terminal alpha helix, which contains binding sites for the globular heads of C1q. In conclusion, the data implicate the platelet gC1qR as a novel cellular binding site for staphylococcal protein A and suggest an additional mechanism for bacterial cell adhesion to sites of vascular injury and thrombosis.

A novel role for alpha 3 beta 1 integrins in extracellular matrix assembly

1995 ◽  
Vol 108 (6) ◽  
pp. 2511-2523 ◽  
Author(s):  
C. Wu ◽  
A.E. Chung ◽  
J.A. McDonald
Keyword(s):  
Extracellular Matrix ◽  
Cell Adhesion ◽  
Binding Activity ◽  
Integrin Subunit ◽  
Pericellular Matrix ◽  
Matrix Assembly ◽  
Amino Terminal ◽  
Beta 1 Integrin ◽  
Fibronectin Deposition

To study the biological role of alpha 3 beta 1 integrins in cell adhesion, migration, and in the deposition of extracellular matrix, we stably expressed the human alpha 3 integrin subunit in the alpha 4, alpha 5 integrin deficient CHO cell line B2. The expression of alpha 3 beta 1 integrins enhanced cell adhesion on entactin (also known as nidogen), but not on fibronectin. Using recombinant GST-fusion proteins that span the entire length of the entactin molecule, we located cell adhesive activity to the G2 domain of entactin. These results suggest that the alpha 3 beta 1 integrin functions as an adhesion receptor interacting with the G2 domain of entactin. On the other hand, the expression of alpha 3 beta 1 integrins did not confer the ability to migrate on entactin. Strikingly, the expression of alpha 3 beta 1 dramatically increased the deposition of entactin and fibronectin into the pericellular matrix. This was accompanied by increased binding activity of the 29 kDa amino-terminal domain of fibronectin. Thus, similar to alpha 5 beta 1 integrins, alpha 3 beta 1 integrins can play an important role in modulating the assembly of pericellular matrices. However, unlike fibronectin deposition supported by alpha 5 beta 1, alpha 3 beta 1 supported fibronectin deposition into pericellular matrix was not inhibited by antibodies binding to the RGD containing cell adhesion domain of fibronectin, demonstrating that the two processes are mechanistically distinct. The role of alpha 3 beta 1 in pericellular matrix assembly potentially implicates this receptor in the assembly and/or recognition of entactin-containing pericellular matrices, an observation consistent with its apparent role in the renal glomerulus of the mammalian kidney.

The amino-terminal matrix assembly domain of fibronectin stabilizes cell shape and prevents cell cycle progression

1999 ◽  
Vol 112 (19) ◽  
pp. 3225-3235 ◽  
Author(s):  
R.A. Christopher ◽  
S.R. Judge ◽  
P.A. Vincent ◽  
P.J. Higgins ◽  
P.J. McKeown-Longo
Keyword(s):  
Cell Cycle ◽  
Extracellular Matrix ◽  
Cell Shape ◽  
Cellular Response ◽  
Cell Cycle Progression ◽  
Cytochalasin D ◽  
Matrix Assembly ◽  
Cycle Progression ◽  
Amino Terminal ◽  
Fibronectin Matrix

Adhesion to the extracellular matrix modulates the cellular response to growth factors and is critical for cell cycle progression. The present study was designed to address the relationship between fibronectin matrix assembly and cell shape or shape dependent cellular processes. The binding of fibronectin's amino-terminal matrix assembly domain to adherent cells represents the initial step in the assembly of exogenous fibronectin into the extracellular matrix. When added to monolayers of pulmonary artery endothelial cells, the 70 kDa fragment of fibronectin (which contains the matrix assembly domain) stabilized both the extracellular fibronectin matrix as well as the actin cytoskeleton against cytochalasin D-mediated structural reorganization. This activity appeared to require specific fibronectin sequences as fibronectin fragments containing the cell adhesion domain as well as purified vitronectin were ineffective inhibitors of cytochalasin D-induced cytoarchitectural restructuring. Such pronounced morphologic consequences associated with exposure to the 70 kDa fragment suggested that this region of the fibronectin molecule may affect specific growth traits known to be influenced by cell shape. To assess this possibility, the 70 kDa fragment was added to scrape-wounded monolayers of bovine microvessel endothelium and the effects on two shape-dependent processes (i.e. migration and proliferation) were measured as a function of time after injury and location from the wound. The addition of amino-terminal fragments of fibronectin to the monolayer significantly inhibited (by >50%) wound closure. Staining of wounded monolayers with BrdU, moreover, indicated that either the 70 kDa or 25 kDa amino-terminal fragments of fibronectin, but not the 40 kDa collagen binding fragment, also inhibited cell cycle progression. These results suggest that the binding of fibronectin's amino-terminal region to endothelial cell layers inhibits cell cycle progression by stabilizing cell shape.

The single CH domain of calponin is neither sufficient nor necessary for F-actin binding

1998 ◽  
Vol 111 (13) ◽  
pp. 1813-1821 ◽  
Author(s):  
M. Gimona ◽  
R. Mital
Keyword(s):  
Binding Site ◽  
Tandem Repeats ◽  
Actin Binding ◽  
Carboxyl Terminus ◽  
Amino Terminus ◽  
Binding Motif ◽  
Amino Terminal ◽  
Nonmuscle Cells ◽  
Carboxy Terminal

Calponins have been implicated in the regulation of actomyosin interactions in smooth muscle cells, cytoskeletal organisation in nonmuscle cells, and the control of neurite outgrowth. Domains homologous to the amino-terminal region of calponin have been identified in a variety of actin cross-linking proteins and signal transduction molecules, and by inference these ‘calponin homology (CH) domains’ have been assumed to participate in actin binding. We here report on the actin binding activities of the subdomains of the calponin molecule. All three mammalian isoforms of calponin (basic h1, neutral h2 and acidic) possess a single CH domain at their amino terminus as well as three tandem repeats proximal to the carboxyl terminus. Calponin h2 differs, however, from h1 in lacking a consensus actin-binding motif in the region 142–163, between the CH domain and the tandem repeats, which in h1 calponin can be chemically cross-linked to actin. Despite the absence of this consensus actin-binding motif, recombinant full-length h2 calponin co-sediments in vitro with F-actin, suggesting the presence of another binding site in the molecule. It could be shown that this binding site resides in the C-terminal tandem repeats and not in the CH domain. Thus, constructs of h2 calponin bearing partial or complete deletions of the triple repeated sequences failed to co-localise with actin stress fibres despite the presence of a CH domain. Deletion of the acidic carboxyl terminus, beyond the repeats, increased actin binding, suggesting that the carboxy-terminal tail may modulate actin association. Results obtained from transient transfections of amino- and carboxy-terminal truncations in h1 calponin were consistent with the established location of the actin binding motif outside and carboxy-terminal to the CH domain, and confirm that the presence of a single CH domain alone is neither sufficient nor necessary to mediate actin binding. Instead, the carboxy-terminal tandem repeats of h1 and h2 calponin are shown to harbour a second, independent actin binding motif.

Localization of fibronectin matrix assembly sites on fibroblasts and endothelial cells

1997 ◽  
Vol 110 (5) ◽  
pp. 569-581 ◽  
Author(s):  
R.A. Christopher ◽  
A.P. Kowalczyk ◽  
P.J. McKeown-Longo
Keyword(s):  
Extracellular Matrix ◽  
Binding Sites ◽  
Focal Adhesions ◽  
Cytochalasin D ◽  
Adherent Cells ◽  
Matrix Assembly ◽  
Fibronectin Matrix ◽  
Nucleation Sites ◽  
Beta1 Integrin ◽  
Texas Red

Polymerization of soluble fibronectin into extracellular matrix fibers occurs through the interaction between the amino terminus of fibronectin contained within a 70 kDa fragment and ‘matrix assembly sites’ on the cell surface. The present studies were performed to localize the ‘matrix assembly sites’ (defined by 70 kDa binding sites) on newly adherent cells and on cells containing preformed fibronectin matrix. Matrix nucleation sites on newly spread cells were visualized using Texas Red conjugated 70 kDa fragment and were found to colocalize with vinculin and substrate fibronectin fibrils. Cells plated onto vitronectin coated coverslips did not exhibit any 70 kDa binding sites although these cells were well-spread with fully developed focal adhesions. Time course studies indicated that 70 kDa binding sites could be detected on newly adherent cells within 30–40 minutes following cell plating onto fibronectin coated coverslips, prior to the reorganization of substrate fibronectin into fibrils. Similarly, exogenous fibronectin conjugated with Texas Red was also colocalized with vinculin when added to newly adherent cells. The disruption of actin filaments with cytochalasin D both prevented the expression of 70 kDa binding sites and also resulted in the loss of established 70 kDa binding sites on newly spread cells. After 3 days in culture, cells organized an extensive fibronectin matrix and 70 kDa was colocalized with two distinct types of matrix fibronectin fibers: fine linear cell-associated fibers which co-stained with the beta1 integrin and coarse extracellular fibers which did not stain for the beta1 integrin. There was also a third type of fibronectin fiber which was organized into a meshwork structure. There was no localization of either beta1 or 70 kDa to these structures. Treatment of 3-day cells with cytochalasin D resulted in the disruption of cell-matrix fibers and cell-associated 70 kDa binding sites. In contrast, the coarse extracellular matrix fibers as well as the meshwork fibers were unaffected by cytochalasin. In the presence of cytochalasin D, 70 kDa bound to sites which colocalized with the coarse extracellular matrix fibers. These data suggest that de novo assembly of fibronectin matrix occurs at sites of focal adhesion and as fibronectin polymerization proceeds, matrix nucleation sites colocalize along cell associated fibronectin fibers. At later times 70 kDa is localized to a subset of more mature fibronectin-containing fibers. These results suggest that there are at least three morphologically distinct 70 kDa binding sites on adherent cells: one which colocalizes with beta1 to focal adhesions, a second which colocalizes with beta1 and fibronectin in matrix contacts, and a third which localizes to extracellular matrix fibers.

Characterization of a Monoclonal Antibody Specific to the Amino Terminus of the α-Chain of Human Fibrin

1990 ◽  
Vol 63 (03) ◽  
pp. 445-448 ◽  
Author(s):  
Simon J T Mao ◽  
Ann E Rechtin ◽  
John L Krstenansky ◽  
Richard L Jackson
Keyword(s):  
Monoclonal Antibody ◽  
Monoclonal Antibodies ◽  
Solid Phase ◽  
Solid Phase Peptide Synthesis ◽  
Keyhole Limpet Hemocyanin ◽  
Amino Terminus ◽  
Amino Terminal ◽  
Thrombin Cleavage ◽  
Α Chain ◽  
A Chain

SummaryA peptide, Gly-Pro-Arg-Val-Val-Glu, corresponding to the first six residues of the amino terminus of the a-chain of human fibrin (desAA-fihrin) was prepared by solid-phase peptide synthesis. The peptide was covalently linked to keyhole-limpet hemocyanin (KLH) and used as an immunogen for preparing monoclonal antibodies. A monoclonal antibody specific to the hexapeptide, but not to KLH or fibrinogen, was produced. The antibody did not bind to thrombin-mediated clots prepared from either plasma or purified fibrinogen. However, immunoreactivity was detected when fibrin (prepared from fibrinogen) was solubilized with 8 M urea. In contrast, a monoclonal antibody specific to the amino terminus (Gly-His-Arg-Pro-Leu-Asp-Lys) of the (β-chain of fibrin recognized the epitope in clots. These results indicate that thrombin cleavage of fibrinogen produces a structural change in the amino terminal domain of the α-chain that makes it inaccessible to antibody interaction. In addition, our study suggests that the potential clinical application of monoclonal antibodies to localize fibrin-rich thrombi must take into account the final structure of clots.

scholarly journals Activation of Distinct α5β1-mediated Signaling Pathways by Fibronectin's Cell Adhesion and Matrix Assembly Domains

1998 ◽  
Vol 141 (1) ◽  
pp. 241-253 ◽  
Author(s):  
Denise C. Hocking ◽  
Jane Sottile ◽  
Paula J. McKeown-Longo
Keyword(s):  
Cell Adhesion ◽  
Amino Terminus ◽  
Type I ◽  
New Paradigm ◽  
Matrix Assembly ◽  
Rgd Peptides ◽  
Surface Receptors ◽  
Amino Terminal ◽  
Dynamic Cell ◽  
Α5β1 Integrin

The interaction of cells with fibronectin generates a series of complex signaling events that serve to regulate several aspects of cell behavior, including growth, differentiation, adhesion, and motility. The formation of a fibronectin matrix is a dynamic, cell-mediated process that involves both ligation of the α5β1 integrin with the Arg-Gly-Asp (RGD) sequence in fibronectin and binding of the amino terminus of fibronectin to cell surface receptors, termed “matrix assembly sites,” which mediate the assembly of soluble fibronectin into insoluble fibrils. Our data demonstrate that the amino-terminal type I repeats of fibronectin bind to the α5β1 integrin and support cell adhesion. Furthermore, the amino terminus of fibronectin modulates actin assembly, focal contact formation, tyrosine kinase activity, and cell migration. Amino-terminal fibronectin fragments and RGD peptides were able to cross-compete for binding to the α5β1 integrin, suggesting that these two domains of fibronectin cannot bind to the α5β1 integrin simultaneously. Cell adhesion to the amino-terminal domain of fibronectin was enhanced by cytochalasin D, suggesting that the ligand specificity of the α5β1 integrin is regulated by the cytoskeleton. These data suggest a new paradigm for integrin-mediated signaling, where distinct regions within one ligand can modulate outside-in signaling through the same integrin.

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