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Fibronectin fragments in human seminal plasma.

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EN
The study has revealed the presence of fibronectin (FN) fragments and a lack of intact FN in 72 seminal plasma samples. The FN fragmentation was examined by immunoblotting with a monoclonal antibody specific to the central cellular FN domain and was confirmed with a monoclonal antibody directed to the C-terminal domain of FN. Nine FN fragments between 60 and 200 kDa and five fragments of 60-150 kDa were identified in seminal plasma samples of normozoospermic and of terato-, oligoterato-, and oligoasthenoterato-spermic groups, respectively. The relative amounts of the 60, 90 and 100 kDa FN fragments were 2-3 times higher in seminal plasmas with abnormal semen characteristics than in the normozoospermic group. The results suggest that seminal plasma FN fragments may contribute to fertilization and the analysis of FN fragmentation may have a diagnostic value in andrological investigations.
EN
Adherence of pathogens to extracellular matrix proteins and host cells is one of the essential steps in the microbial colonization of the human organism. The adhesion of C. glabrata, i.e. the second major causative agent of human disseminated candidiases after C. albicans, to the host epithelium mainly engages specific fungal cell wall proteins - epithelial adhesins (Epa) - in particular, Epa1, Epa6 and Epa7. The aim of the present study was to identify the major Epa protein involved in the interactions with the human extracellular matrix protein - fibronectin - and to present the kinetic and thermodynamic characteristics of these interactions. A relatively novel gel-free approach, i.e. the "cell surface shaving" that consists in short treatment of fungal cells with trypsin was employed to identify the C. glabrata surfaceome. Epa6 was purified, and the isolated protein was characterized in terms of its affinity to human fibronectin using a microplate ligand-binding assay and surface plasmon resonance measurements. The dissociation constants for the binding of Epa6 to fibronectin were determined to range between 9.03 × 10-9 M and 7.22 × 10-8 M, depending on the method used (surface plasmon resonance measurements versus the microplate ligand-binding assay, respectively). The identified fungal pathogen-human host protein-protein interactions might become a potential target for novel anticandidal therapeutic approaches.
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2001
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vol. 48
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issue 1
175-181
EN
The activities of extracellular signal-regulated kinases (ERK1/ERK2) is required for proliferation of several types of cells. The performed analysis showed stimulation of ERK's by fetal calf serum (FCS) or fibronectin in the C3H 10T1/2 cell cultures at logarithmic phase of growth. The ERKs activity was not stimulated in confluent cells. This could not be accounted for a partial down regulation of ERK since its level was stable in both types of cells regardless of their density and kind of stimulation. Searching for ERK upstream elements we studied the integrin receptor gene transcript by RT-PCR and focal adhesion kinase (FAK) by Western blotting and phosphorylation assays. It was found that FCS and fibronectin stimulated phosphorylating activity of FAK in the cells at the logarithmic phase of growth, but were inefficient in the confluent cells. RT-PCR showed the presence of α5 and β1 integrin transcripts, and p125FAK was at the same level regardless of the type of stimulation. These data indicate that the ability of FAK to be activated plays an important role in ERK regulation and, in consequence in proliferation and growth inhibition during confluence.
EN
Three monoclonal antibodies specific to the central cell-binding and the C- and N-terminal domains of fibronectin (FN) were used to test antigenic epitope accessibility on human plasma and cerebrospinal fibronectins. In the plasma group, the mean N-terminal FN domain immunoreactivity was about one fourth that of the cell-binding and C-terminal domains, whereas in cerebrospinal fluid they were nearly equal. In the presence of 0.5-6 M urea N-terminal domain immunoreactivity in the plasma increased 3-6-fold, but it decreased 0.7-3-fold in the cerebrospinal fluid. Analysis of fibronectin domain immunoreactivities of the cell-binding and N-terminal domains by a panel of specific monoclonal antibodies may reveal N-terminal fibronectin domain accessibility for reaction with biological partner ligand(s) and/or processes in which FN could be implicated. Such determinations may have important clinical implications.
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