Integrin alpha V beta 3 together with alpha IIb beta ₃, constitutes the only known beta 3 Integrins (1‑3). The non‑covalent heterodimer of 170 kDa alpha V/CD51 and 93 kDa beta ₃/CD61 subunits shows wide expression, notably by endothelial cells and osteoclasts (2‑4). Each subunit has a transmembrane sequence and a short cytoplasmic tail connected to the cytoskeleton. Active cell surface alpha V beta 3 adheres to matrix proteins including vitronectin, fibronectin, fibrinogen and thrombospondin (2, 3). The ligand binding site of alpha V beta 3 is in the N‑terminal head region, formed by interaction of the beta 3 vWFA domain with the alpha V beta-propeller structure (4). The alpha V subunit contributes a thigh and a calf region, while the beta 3 subunit contains a PSI domain and four cysteine‑rich I‑EGF folds. The alpha V subunit domains termed thigh, calf‑1 and calf‑2 generate a “knee” region that is bent when the alpha V beta 3 is in its constitutively inactive state. Activation, either by “inside out” signaling or by Mg²⁺ or Mn²⁺ binding, extends the Integrin to expose its ligand binding site (1, 4). The 958 aa mouse alpha V ECD shares 92‑95% aa sequence identity with human, rat and bovine  alpha V while the 692 aa mouse beta ₃ ECD shares 95% aa identity with rat and 89‑91% with human, canine, equine, bovine and porcine beta ₃. alpha V beta 3 is essential for the maturation of osteoclasts and their binding and resorption of bone; it also, however, promotes their apoptosis (5, 6). M‑CSF R and alpha V beta 3 share signaling pathways during osteoclastogenesis, and deletion of either molecule causes osteopetrosis (5, 6). alpha V beta 3 is involved in several other signaling pathways by direct interaction with receptor tyrosine kinases and ligands. For example, it cooperates with endothelial cell VEGF R2 in angiogenesis, and with IGF‑1 to promote cancer cell proliferation and invasiveness (7, 8). Also, cell entry of several viruses is mediated by alpha V beta 3 (4, 9).