Molecular Cloning, Characterization, Expression Analysis and Chromosomal Localization of the Gene Coding for the Porcine αIIb Subunit of the αIIbβ3 Integrin Platelet Receptor

Integrins are a long family of heterodimeric transmembrane glycoproteins consisting of multiple combinations of noncovalently linked α and β chains, which generate different complex receptors with different expression patterns and ligand binding profiles. The integrins bind to extracellular matrix (ECM) or to cell-surface ligands, regulating numerous downstream pathways (Hynes, 2002). Each integrin binds to only a limited series of ligands, ensuring that cell adhesion and migration are precisely regulated. The α subunit mainly determines the substrate specificity with extracellular matrix molecules (ECM) (Yamada, 1991), while the intracytoplasmic tail of the β chain is predominantly responsible for the integrin interaction with the cell cytoskeleton by binding to vinculin, talin and α-actin (Isenberg, 1991). Thus, this heterodimeric association between α and β subunits allows the integrins to act as bidirectional signaling molecules in the different tissues and cell types in which they are widely distributed, mediating a variety of biological processes so diverse as embryogenesis, haemostasis, tissue repair, migration, cell polarity, immune response and metastatic diffusion of tumor cells (Hynes, 1987, 1992; Hemler et al., 1994). Mammalian integrins have been divided into subfamilies according to their β subunit. The most important β integrin subfamilies are β1, β2 and β3. Within a subfamily, the same β subunit can associate with different α subunits. To date, 18 α and 8 β chains -whose combinations provide up to 24 different integrinshave been described in mammal species (Hynes et al., 2002; Alam et al, 2007).