Recombinant Mouse Integrin alpha M beta 2 Protein, CF

Integrin  alphaM beta2, also called MAC‑1 or complement receptor type 3 (CR3), is one of three leukocyte  beta2 integrins. The non‑covalent heterodimer of 170 kDa alphaM/CD11b and 95 kDa beta2/CD18 integrin subunits is expressed mainly on myeloid and natural killer cells (1‑6). The alphaM vWFA or I‑domain, which contains adhesion sites, forms the N‑terminal head region with the alphaM beta‑propeller and the beta2 vWFA domain. Unlike most integrins, the calf domain of alphaM is lectin‑like and binds carbohydrates (7). Each subunit has a transmembrane sequence and a short cytoplasmic tail. The 1089 amino acid (aa) mouse alphaM/CD11b ECD shares 87% aa sequence identity with rat, and 70‑74% with human, equine, bovine, feline, and canine  alphaM ECD. A potential mouse alphaM isoform lacks 117 aa within the beta‑propeller. The 679 aa mouse  beta2/CD18 ECD shares 91% aa sequence identity with rat, and 80‑82% with human, bovine, canine, and porcine beta2 ECD. Like other integrins, alphaM beta2 has multiple activation states (1‑3). In the presence of divalent cations and "inside‑out" signaling, alphaM beta2 is fully active and extended. In the inactive state, the heterodimer flexes in the center at the alphaM thigh and calf domains and beta2 I‑EGF domains, impeding access to adhesion sites. Active alphaM beta2 binds an unusually large number of adhesion partners, including the complement opsonin fragment iC3b, coagulation proteins fibrinogen, plasminogen and factor X, extracellular matrix (ECM) proteins fibronectin, laminin and collagen, and cell surface ICAMs, myelin basic protein and DC-SIGN (3, 4, 7). alphaM beta2 lectin-like adhesion partners include heparin, bacterial lipopolysaccharides, and GPI‑linked glycoproteins such as uPAR and Fc gammaRIIIB (3, 7). Binding of platelet JAM‑C links platelets with myeloid and dendritic cell (DC) alphaM beta2 and recruits these cells to inflamed or injured endothelium, while neutrophil alphaM beta2 adheres to RAGE on inflamed endothelium; both are atherogenic events (3, 8, 9). However, activation of alphaM beta2 inhibits alternative activation of macrophages and atherosclerotic foam cell formation (3, 10). alphaM beta2 can either suppress or allow constitutive neutrophil apoptosis, depending on its ligand and activation state (3, 11, 12). Deletion of mouse  alphaM causes defects in neutrophil adhesion and degranulation, while mutations of human or mouse  beta2 cause leukocyte adhesion deficiency (LAD‑1) and susceptibility to bacterial infections (3, 12, 13).