Porcine CD18 mediates Actinobacillus pleuropneumoniae ApxIII species-specific toxicity.

Actinobacillus pleuropneumoniae, the causative agent of porcine pleuropneumonia, produces Apx toxins that are recognized as major virulence factors. Recently, we showed that ApxIIIA-cytotoxic activity specifically targets Sus scrofa leukocytes. Since both LtxA from Aggregatibacter actinomycetem comitans (aggressive periodontitis in humans) and LktA from Mannheimia haemolytica (pneumonia in ruminants) share this characteristic, respectively towards human and ruminant leukocytes, and because both use the CD18 subunit to interact with their respective LFA-1, we hypothesized that ApxIIIA was likely to bind porcine CD18 to exercise its deleterious effects on pig leukocytes.

Probing of Actinobacillus pleuropneumoniae ApxIIIA toxin-dependent cytotoxicity towards mammalian peripheral blood mononucleated cells.

Background: Actinobacillus pleuropneumoniae, the causative bacterial agent of porcine pleuropneumonia, produces Apx toxins which belong to RTX toxin family and are recognized as the major virulence factors. So far, their target receptor(s) has not been identified and the disease cytopathogenesis remains poorly understood. Production of an active Apx toxin and characterization of its toxic activity constitute the premises necessary to the description of its interaction with a potential receptor.

Mannheimia haemolytica leukotoxin-induced cytolysis of caprine (Capra hircus) leukocytes is mediated by the CD18 subunit of beta2-integrins.

Mannheimiosis is the major respiratory disease among some ruminants, whereas it is not pathogenic for other mammals, an observation that has been attributed to a specific interaction between Mannheimia haemolytica leukotoxin (Lkt) and bovine or ovine CD18 subunit of lymphocyte function-associated antigen-1 (LFA-1) and Mac-1. We therefore hypothesized that Lkt utilizes CD18 as its receptor on caprine leukocytes as well. We have transiently transfected the beta2-integrins-deficient K-562 cell line with cDNAs encoding caprine CD11a and caprine CD18 to determine the susceptibility of the transfectants to Lkt-induced cytolysis.

The wild boar (Sus scrofa) lymphocyte function-associated antigen-1 (CD11a/CD18) receptor: cDNA sequencing, structure analysis and comparison with homologues.

Background: The most predominant beta2-integrin lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alphaLbeta2), expressed on all leukocytes, is essential for many adhesive functions of the immune system. Interestingly, RTX toxin-producing bacteria specifically target this leukocyte beta2-integrin which exacerbates lesions and disease development.

Results: This study reports the sequencing of the wild boar beta2-integrin CD11a and CD18 cDNAs.

Stability domains, substrate-induced conformational changes, and hinge-bending motions in a psychrophilic phosphoglycerate kinase. A microcalorimetric study.

The cold-active phosphoglycerate kinase from the Antarctic bacterium Pseudomonas sp. TACII18 exhibits two distinct stability domains in the free, open conformation. It is shown that these stability domains do not match the structural N- and C-domains as the heat-stable domain corresponds to about 80 residues of the C-domain, including the nucleotide binding site, whereas the remaining of the protein contributes to the main heat-labile domain.

The CD11a partner in Sus scrofa lymphocyte function-associated antigen-1 (LFA-1): mRNA cloning, structure analysis and comparison with mammalian homologues.

Background: Lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alphaLbeta2), the most abundant and widely expressed beta2-integrin, is required for many cellular adhesive interactions during the immune response. Many studies have shown that LFA-1 is centrally involved in the pathogenesis of several diseases caused by Repeats-in-toxin (RTX)-producing bacteria.

Results: The porcine-LFA-1 CD11a (alpha) subunit coding sequence was cloned, sequenced and compared with the available mammalian homologues in this study.

Molecular characterisation of the caprine (Capra hircus) lymphocyte function-associated antigen-1 alpha subunit-encoding cDNA.

Background: Lymphocyte function-associated antigen-1 (LFA-1, CD11a/CD18, alpha L beta 2) is required for many cellular adhesive interactions during the immune response.

Methods: We used SMART RACE technology to obtain caprine CD11a 5'- and 3'-ends and RT-PCR to amplify the full-length CDS.

Results: The Capra hircus CD11a-encoding cDNA was sequenced and compared with its human, murine, rat, bovine and ovine counterparts.

Cloning and characterisation of the primary structure of the sheep lymphocyte function-associated antigen-1 alpha subunit.

The leukocyte integrins play a critical role in a number of cellular adhesive interactions during the immune response. The ovine cDNA encoding CD11a, the predominant alpha subunit of the beta2-integrin family, was sequenced and compared with the human, bovine and murine sequences. Despite some focal differences, it shares all the main characteristics of its known mammalian homologues.

Characterization of the caprine (Capra hircus) beta-2 integrin CD18-encoding cDNA and identification of mutations potentially responsible for the ruminant-specific virulence of Mannheimia haemolytica.

The leukocyte integrins play a critical role in a great number of cellular adhesive interactions during the immune response. We describe here the isolation and characterization of the caprine beta(2) (CD18) sub-unit, common to the leukocyte beta(2)-integrin family. The deduced 770-amino-acid sequence reveals a transmembrane protein with 80, 81, 83, 96 and 99% identity with its canine, murine, human, bovine and ovine homologues respectively.

Molecular cloning and characterisation of the CD18 partner in ovine (Ovis aries) beta2-integrins.

The leukocyte integrins play a critical role in a number of cellular adhesive interactions during the immune response. We describe here the isolation and characterization of the ovine beta(2) (CD18) subunit, common to the leukocyte beta(2)-integrin family. The deduced 770-amino-acid sequence reveals a transmembrane protein with 81%, 83% and 95% identity with its murine, human and bovine homologues, respectively.

The bovine (Bos taurus) CD11a-encoding cDNA: molecular cloning, characterisation and comparison with the human and murine glycoproteins.

The bovine cDNA encoding CD11a, a cell-surface glycoprotein involved in multiple leukocyte functions, was sequenced and compared with the human and murine sequences. Despite some focal differences, it shares all the main characteristics of its known mammalian homologs. Along with the bovine CD18-encoding cDNA, which is available for a long time, the sequence data provided here will allow the successful expression of bovine CD11a, thus giving the first opportunity to express the Bos taurus beta(2)-integrin CD11a/CD18 (LFA-1, alpha(L)beta(2)) in vitro as a tool to examine the specificities of inflammation in the bovine species.

Did psychrophilic enzymes really win the challenge?

Organisms living in permanently cold environments, which actually represent the greatest proportion of our planet, display at low temperatures metabolic fluxes comparable to those exhibited by mesophilic organisms at moderate temperatures. They produce cold-evolved enzymes partially able to cope with the reduction in chemical reaction rates and the increased viscosity of the medium induced by low temperatures. In most cases, the adaptation is achieved through a reduction in the activation energy, leading to a high catalytic efficiency, which possibly originates from an increased flexibility of either a selected area of or the overall protein structure.

Involvement of different transduction pathways in NF-kappa B activation by several inducers.

Double-stimulation was used to demonstrate that, in a T lymphocytic cell line (CEM), phorbol myristate acetate (PMA) rapidly induced NF-kappa B through a signaling pathway which did not involve reactive oxygen species (ROS) and was different from the activation triggered by either H2O2 or tumor necrosis factor-alpha (TNF-alpha). Since these latter compounds were known to activate NF-kappa B translocation in a redox-sensitive way, we have demonstrated that NF-kappa B activation by PMA was resistant to antioxidant N-acetyl-L-cysteine (NAC) and sensitive to kinase inhibitors staurosporine and H7 while activation by H2O2 or TNF-alpha were not.