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

This study reports the sequencing of the wild boar beta2-integrin CD11a and CD18 cDNAs. Predicted CD11a and CD18 subunits share all the main structural characteristics of their mammalian homologues, with a larger interspecies conservation for the CD18 than the CD11a. Besides these strong overall similarities, wild boar and domestic pig LFA-1 differ by 2 (CD18) and 1 or 3 (CD11a) substitutions, of which one is located in the crucial I-domain (CD11a, E168D).As most wild boars are seropositive to the RTX toxin-producing bacterium Actinobacillus pleuropneumoniae and because they have sustained continuous natural selection, future studies addressing the functional impact of these polymorphisms could bring interesting new information on the physiopathology of Actinobacillus pleuropneumoniae-associated pneumonia in domestic pigs.Cell adhesion receptors play crucial roles in multicellular organisms by mediating the direct cell/cell or cells/extracellular matrix proteins interactions. These molecular interactions condition the structural integrity of cells and tissues and contribute to the signalling transduction intervening in the cellular dynamic [1]. Cell adhesion receptors are subdivided in several membrane-associated protein families, including integrins, cadherins, immunoglobulin superfamily cell adhesion molecules, selectins, and syndecans. Integrins are a family of cell surface adhesion and signalling glycoproteins made up of non-covalently associated 120–180 kDa α and 90-110kDa β subunits [2]. There are 19 distinct α subunits and 8 β subunits that are combined to form 25 different heterodimeric receptors [1]. Each subunit possesses (i) a large extracellular N-terminal domain associating with that of the companion subunit to form the integrin headpiece which contains the ligand binding site, (ii) a single transmembrane stretch, and (iii) a short cytoplasmic C-terminal tail which mediates interactions with cytoskeleton and signalling proteins [1,3,4].Within the integr