Antibodies to coagulase of crossreact to Efb and reveal different binding of shared fibrinogen binding repeats.

pathology is caused by a plethora of virulence factors able to combat multiple host defence mechanisms. Fibrinogen (Fg), a critical component in the host coagulation cascade, plays an important role in the pathogenesis of this bacterium, as it is the target of numerous staphylococcal virulence proteins. Amongst its secreted virulence factors, coagulase (Coa) and Extracellular fibrinogen-binding protein (Efb) share common Fg binding motives and have been described to form a Fg shield around staphylococcal cells, thereby allowing efficient bacterial spreading, phagocytosis escape and evasion of host immune system responses.

The Complex Fibrinogen Interactions of the Coagulases.

The two coagulases, von Willebrand factor binding protein (vWbp) and Coagulase (Coa), are critical virulence factors in several animal models of invasive () infections. These proteins are part of an intricate system of proteins that uses to assemble a fibrinogen (Fg)/fibrin protective shield surrounding itself. This shield allows the microorganism to evade clearance by the host phagocytic cells.

The Staphylococcus aureus polysaccharide capsule and Efb-dependent fibrinogen shield act in concert to protect against phagocytosis.

Staphylococcus aureus has developed many mechanisms to escape from human immune responses. To resist phagocytic clearance, S. aureus expresses a polysaccharide capsule, which effectively masks the bacterial surface and surface-associated proteins, such as opsonins, from recognition by phagocytic cells.

Fibrinogen Is at the Interface of Host Defense and Pathogen Virulence in Staphylococcus aureus Infection.

Fibrinogen not only plays a pivotal role in hemostasis but also serves key roles in antimicrobial host defense. As a rapidly assembled provisional matrix protein, fibrin(ogen) can function as an early line of host protection by limiting bacterial growth, suppressing dissemination of microbes to distant sites, and mediating host bacterial killing. Fibrinogen-mediated host antimicrobial activity occurs predominantly through two general mechanisms, namely, fibrin matrices functioning as a protective barrier and fibrin(ogen) directly or indirectly driving host protective immune function.

Coagulase and Efb of Staphylococcus aureus Have a Common Fibrinogen Binding Motif.

Unlabelled: Coagulase (Coa) and Efb, secreted Staphylococcus aureus proteins, are important virulence factors in staphylococcal infections. Coa interacts with fibrinogen (Fg) and induces the formation of fibrin(ogen) clots through activation of prothrombin. Efb attracts Fg to the bacterial surface and forms a shield to protect the bacteria from phagocytic clearance.

Mice expressing a mutant form of fibrinogen that cannot support fibrin formation exhibit compromised antimicrobial host defense.

Fibrin(ogen) is central to hemostasis and thrombosis and also contributes to multiple physiologic and pathologic processes beyond coagulation. However, the precise contribution of soluble fibrinogen vs insoluble fibrin matrices to vascular integrity, tissue repair, inflammation, and disease has been undefined and unapproachable. To establish the means to distinguish fibrinogen- and fibrin-dependent processes in vivo, Fib(AEK) mice were generated that carry normal levels of circulating fibrinogen but lack the capacity for fibrin polymer formation due to a germ-line mutation in the Aα chain thrombin cleavage site.

Phagocytosis escape by a Staphylococcus aureus protein that connects complement and coagulation proteins at the bacterial surface.

Upon contact with human plasma, bacteria are rapidly recognized by the complement system that labels their surface for uptake and clearance by phagocytic cells. Staphylococcus aureus secretes the 16 kD Extracellular fibrinogen binding protein (Efb) that binds two different plasma proteins using separate domains: the Efb N-terminus binds to fibrinogen, while the C-terminus binds complement C3. In this study, we show that Efb blocks phagocytosis of S.

Matrilin-1 is essential for zebrafish development by facilitating collagen II secretion.

Matrilin-1 is the prototypical member of the matrilin protein family and is highly expressed in cartilage. However, gene targeting of matrilin-1 in mouse did not lead to pronounced phenotypes. Here we used the zebrafish as an alternative model to study matrilin function in vivo.

Collagen-binding microbial surface components recognizing adhesive matrix molecule (MSCRAMM) of Gram-positive bacteria inhibit complement activation via the classical pathway.

Members of a family of collagen-binding microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) from Gram-positive bacteria are established virulence factors in several infectious diseases models. Here, we report that these adhesins also can bind C1q and act as inhibitors of the classical complement pathway. Molecular analyses of Cna from Staphylococcus aureus suggested that this prototype MSCRAMM bound to the collagenous domain of C1q and interfered with the interactions of C1r with C1q.

Binding of Efb from Staphylococcus aureus to fibrinogen blocks neutrophil adherence.

In addition to its pivotal role in hemostasis, fibrinogen (Fg) and provisional fibrin matrices play important roles in inflammation and regulate innate immune responses by interacting with leukocytes. Efb (the extracellular fibrinogen-binding protein) is a secreted Staphylococcus aureus protein that engages host Fg and complement C3. However, the molecular details underlying the Efb-Fg interaction and the biological relevance of this interaction have not been determined.

A structural model of the Staphylococcus aureus ClfA-fibrinogen interaction opens new avenues for the design of anti-staphylococcal therapeutics.

The fibrinogen (Fg) binding MSCRAMM Clumping factor A (ClfA) from Staphylococcus aureus interacts with the C-terminal region of the fibrinogen (Fg) gamma-chain. ClfA is the major virulence factor responsible for the observed clumping of S. aureus in blood plasma and has been implicated as a virulence factor in a mouse model of septic arthritis and in rabbit and rat models of infective endocarditis.

Abnormal collagen fibrils in cartilage of matrilin-1/matrilin-3-deficient mice.

Matrilins are oligomeric extracellular matrix adaptor proteins mediating interactions between collagen fibrils and other matrix constituents. All four matrilins are expressed in cartilage and mutations in the human gene encoding matrilin-3 (MATN3) are associated with different forms of chondrodysplasia. Surprisingly, however, Matn3-null as well as Matn1- and Matn2-null mice do not show an overt skeletal phenotype, suggesting a dominant negative pathomechanism for the human disorders and redundancy/compensation among the family members in the knock-out situation.

The matrilins--adaptor proteins in the extracellular matrix.

The matrilins form a four-member family of modular, multisubunit matrix proteins, which are expressed in cartilage but also in many other forms of extracellular matrix. They participate in the formation of fibrillar or filamentous structures and are often associated with collagens. It appears that they mediate interactions between collagen-containing fibrils and other matrix constituents, such as aggrecan.

CD13 (aminopeptidase N) can associate with tumor-associated antigen L6 and enhance the motility of human lung cancer cells.

Cancer metastasis is a multiple-step process that involves the regulated interaction of diverse cellular proteins. We recently reported that the expression of tumor-associated antigen L6 (TAL6) promoted the invasiveness of lung cancer cells and was inversely correlated with disease-free survival of squamous lung carcinoma patients. We now report that CD13 (aminopeptidase N) can associate with TAL6 and can enhance cancer cell migration.

Zebrafish (Danio rerio) matrilins: shared and divergent characteristics with their mammalian counterparts.

We have cloned the cDNAs of the zebrafish (Danio rerio) members of the matrilin family of extracellular adaptor proteins. In contrast to mammals, no orthologue of matrilin-2 was found in zebrafish, either by RT (reverse-transcriptase) PCR using degenerated primers or by screening the databases (Ensembl and NCBI); however, two forms of matrilin-3, matrilin-3a and -3b, were present. The identity with the mammalian matrilins is from more than 70% for the VWA (von Willebrand factor A)-like domains to only 28% for the coiled-coil domains of matrilin-3a and -3b.

A simple method for the production of recombinant proteins from mammalian cells.

Expression of recombinant proteins in mammalian cells is useful for obtaining products with normal post-translational modifications. We describe a simple and economical method for the production of milligram levels of proteins in murine fibroblasts. Retroviral or LIPOFECTAMINE (Gibco Laboratories) transduction was employed to generate stable murine-fibroblast producer cells.

Tumor-associated antigen L6 and the invasion of human lung cancer cells.

Metastasis is a coordinated process that depends on the interaction of cancer cells with the tumor microenvironment. Members of the transmembrane-4 superfamily (TM4SF) of surface proteins have been implicated in the regulation of cancer cell metastasis, and the expression of several TM4SF members on tumor cells is inversely correlated with patient prognosis. The tumor-associated antigen L6 (TAL6), a distant member of the TM4SF, is expressed on most epithelial cell carcinomas and is a target for antibody-mediated therapy.