Biomedical subjects

S Antohi

Publications and source records attributed to S Antohi.

At least 19 recordsLinked to original sources

PubMed1995

Integrin-dependent tyrosine phosphorylation in corneal fibroblasts.

PURPOSE: A major pathway for intracellular signaling from cell surface receptors, such as integrins, involves intracellular phosphorylation. In corneal fibroblasts, the authors have investigated the role of tyrosine phosphorylation in integrin-dependent cell adhesion to extracellular matrix. METHODS: Antibodies were used to detect phosphotyrosine-containing proteins, including focal adhesion kinase in lysates and immunoprecipitates of corneal fibroblasts. The authors used anti-phosphotyrosine antibodies to localize phosphotyrosines in fixed cultured corneal fibroblasts. Similarly, immunocytochemical detection of vinculin was used to identify focal adhesions, the subcellular structures in which integrins organize attachment to matrix extracellularly and to cytoskeletal components intracellularly. RESULTS: Suspension of corneal fibroblasts produced a dramatic decrease in detectable phosphotyrosines. During integrin-dependent fibroblast attachment to exogenously supplied fibronectin, the cytoplasmic phosphotyrosine kinase, focal adhesion kinase (FAK), pp125FAK, became tyrosine phosphorylated. However, FAK was not phosphorylated during fibroblast attachment to vitronectin or polylysine or when cells were kept in suspension. In addition, the treatment of suspended cells with antibody to the extracellular domain of fibronectin receptor caused FAK phosphorylation. Phosphotyrosine was colocalized with vinculin in newly formed focal adhesions. Focal adhesion formation was prevented by herbimycin A, an inhibitor of tyrosine kinases. CONCLUSIONS: In corneal fibroblasts, fibronectin receptor-specific signal transduction from extracellular matrix during the formation of focal adhesions requires tyrosine kinase activation, including phosphorylation of FAK. This underscores a role for the fibronectin receptor in signaling from the extracellular matrix in corneal fibroblasts.

Animals↗

PubMed1993

Identification of integrins in cultured corneal fibroblasts and in isolated keratocytes.

PURPOSE: The integrins are a family of transmembrane glycoproteins that function in attachment of cells to one another and to the extracellular matrix. When cell--cell and cell--matrix interactions are altered, the population of integrins may change. In particular, removing cells from their normal environment may be used as a model of wounding. The current study reports the identification of the integrins expressed at the cell surface of noncultured keratocytes and of cultured corneal fibroblasts, which are derived from keratocytes grown in primary culture. METHODS: For integrin identification, the surface proteins of keratocytes and cultured corneal fibroblasts were labeled with biotin, and the integrins were immunoprecipitated using anti-integrin antibodies. Attachment assays determined (1) the extracellular matrix preference of the cultured corneal fibroblasts and (2) the effects of function-perturbing antibodies against the fibronectin receptor (alpha 5 beta 1) or against other beta 1-containing integrins. RESULTS: The integrins of noncultured keratocytes were present as heterodimeric alpha, beta surface proteins that were immunoprecipitated by anti-beta 1, anti-alpha v, anti-alpha 6, anti-alpha 3, anti-alpha 1, and anti-beta 3. Furthermore, when the keratocytes were placed in culture, the integrin pattern changed. The classic fibronectin receptor, alpha 5 beta 1, is then expressed along with additional integrins that bind to fibronectin. Using attachment assays, we determined that the cultured corneal fibroblasts prefer fibronectin to collagen, vitronectin, or laminin as extracellular matrix substrate. In addition, function-perturbing antibodies against the fibronectin receptor (alpha 5 beta 1) or against beta 1 inhibit attachment of cultured corneal fibroblasts to fibronectin. CONCLUSIONS: Receptors for fibronectin and other extracellular matrix molecules are expressed at the cell surface in cultured corneal fibroblasts, and are in position to play a significant functional role as seen in attachment to extracellular matrix.

Animals↗

PubMed1984

Interaction of influenza and parainfluenza viruses with polycations, organic oligocations and chromosome preparations.

As evaluated by light scattering at 90 degrees, natural organic oligocations such as putrescine, spermidine and spermine interfered with myxovirus aggregates which were induced by the histone H2A and strongly amplified by shaking during incubation. In contrast, the synthetic oligocation 1.7-diamino heptane itself aggregated the virus particles, its action being unmodified by adding polycationic H2A in abundance. When human chromosome preparations treated with protamine solution and shaked during incubation were covered with a stable polycationic molecular layer, the chromosomes had become unstainable by the Giemsa method even if the dye was used in excess. Nevertheless, the affinity of influenza virus particles for protamine was so high that they were able to dissociate the protamine molecules from the preformed complexes reconstituting the affinity of chromosome preparations to Giemsa stain. The virus-caused shift in the staining ability of chromosomes did not occur when bacterial suspension was added instead of the viral one. The model of oligocationic relaxation and of polycation condensation accounting for the modulatory effects of polyamines is discussed.

Cations↗

PubMed1979

Lethal effect of protamine and histone on competent Bacillus subtilis cells. Inhibition of genetic transformation by protamine in sublethal concentration.

Under experimental conditions of genetic transformation, protamine and total histone were bactericidal for Bacillus subtilis cells. The abilities to cause lethality were very similar for both, either protamine or histone, with no antagonistic effects amongst these natural polycations. With both basic proteins acting simultaneously the enhancement was higher than a summation of the separate lethal effects. Sublethal concentration of protamine added at the beginning of transformation time, produced a strong inhibition of transforming efficiency. The same concentration added later than 10 min from the start of transformation had no inhibitory effect. These facts together with the absence of inhibition by simple pretreatment of DNA alone as well as the cell protection by protamine against lytic activity of lysozyme, suggest a protamine-cell surface interaction which impedes DNA uptake events.

Bacillus subtilis↗

PubMed1979

Protamine and polyarginine bacteriolysis. Similarities in its mechanism with chromatin DNA picnosis.

Protamine and polyarginine had bacteriolytic effects indicating their primary sites of action as being wall components and showing bacterial diversity genetically determined. Shake-incubation was required in producing cell-lysis. Studies on Bacillus subtilis revealed a high polycation multiplicity per cell in lytic event displaying multihit lysing kinetics; bacteriolysis was inhibited by trypsin, pronase, purified polyanionic wall polysaccharide, and by dissociative actions of salt hypermolarities used in isolation of nucleic acids. The inactivation of polycation lytic abilities during bacteriolysis was accompanied by modifications in electrophoretic running of protamine and polyarginine. It is suggested as mechanism of cell-lysis, the multiple zonal surface condensations of polyanionic wall components by basic polypeptides, likely similar with chromatin DNA picnosis. This analogy is discussed.

Anti-Bacterial Agents↗

PubMed1973