Recombinant Human Integrin alpha V beta 5 Protein, CF

Integrin alphaV beta5 is one of five alphaV integrins and the only known beta5 integrin (1-3). The non-covalent heterodimer of 170 kDa alphaV and 100‑110 kDa beta5 integrin type I transmembrane glycoprotein subunits is expressed on a wide variety of cell types including keratinocytes, fibroblasts, adhesive monocytes, embryonic stem cells, and select endothelium and epithelium (4‑8). alphaV beta5 binds ligands containing an RGD motif, notably vitronectin (1‑10). The 962 aa human alphaV extracellular domain (ECD) shares 92-95% aa sequence identity with mouse, rat and cow alphaV, while the 696 aa human beta5 ECD shares 89%-93% aa identity with mouse, rat, bovine, equine, and canine beta5. The alphaV ECD contains an N-terminal beta- propeller structure, followed by domains termed thigh, calf-1 and calf-2 (1). The 799 aa beta5 contains a vWFA domain within the ECD, which interacts with the alphaV beta-propeller to form a binding domain. Each subunit has a transmembrane sequence and a short cytoplasmic tail. Potential beta5 isoforms include a 691 aa form with an alternate start site at aa 109, a 958 aa form with an alternate N‑terminus, and a 795 aa form with an alternate C‑terminus. Post-translational modifications, such as proteolytic cleavage of the alphaV subunit or phosphorylation of the beta5 cytoplasmic tail, can increase endocytic turnover of the alphaV beta5 protein and/or promote cell migration (7‑10). Growth factors that increase PKC activity, such as VEGF or TGF‑ alpha, promote alphaV beta5-mediated angiogenesis while alphaV beta3, which may be expressed in the same cell, responds to FGF-basic and TNF‑ alpha (11). An inhibitor of both down‑regulates tumor angiogenesis (12). During lung inflammation, up‑regulation of alphaV beta5 on myofibroblasts or infiltrating lymphocytes may contribute to fibrosis by freeing TGF‑ beta from latency (13, 14). On retinal pigment epithelia, alphaV beta5 is important for normal diurnal phagocytosis of outer rod segments, and contributes to adhesion of retinal cells (15).