Human Integrin  alpha 2/CD49b Alexa Fluor® 700‑conjugated Antibody

Integrin alpha 2 is one of twelve integrin family alpha subunits that share the beta 1 subunit (1‑3). Integrin alpha 2 beta 1 is the non-covalent heterodimer of 160 kDa alpha 2 (CD49b) and 130 kDa beta 1 (CD29) type I transmembrane glycoprotein subunits and is one of six very late antigens on activated T cells, designated VLA2 (3). The alpha 2 extracellular domain (ECD) contains an I (inserted) domain which includes the ligand binding site (2, 3). The beta 1 ECD contains a vWFA domain, which participates in binding. Each subunit then has a transmembrane sequence and a short cytoplasmic tail. The dimer is folded when it is least active. Divalent cations and intracellular (inside-out) signaling convert it to its most active, extended and open conformation (1, 2). The 1102 amino acid (aa) human alpha 2 extracellular domain (ECD) shares 83‑89% aa sequence identity with mouse, rat, canine, bovine and equine alpha 2. The I domain-containing beta 1 integrins ( alpha 1 beta 1, alpha 2 beta 1, alpha 10 beta 1 and alpha 11 beta 1) all bind collagens, with alpha 2 beta 1 preferring collagens I‑III (4, 5). Platelet alpha 2 beta 1, also called GPIa, cooperates with another adhesion protein, GPVI, to coordinate platelet collagen binding and activation (3, 6, 7). Other alpha 2 beta 1 ligands include laminin, decorin, E-cadherin, and collagen-like regions of collectin molecules such as C1q (4). Adhesion is synergized by crosstalk with syndecan-1 or HGF R/c-Met, and antagonized by crosstalk with Integrin alpha 1 beta 1 (8‑10). In addition to expression on selected hematopoietic cells, alpha 2 beta 1 is present on a wide variety of non-hematopoietic cells (4). Mice deficient in the alpha 2 subunit have defects in innate immune responses, wound mast cell infiltration and angiogenesis, and platelet responses to collagen (6, 11, 12). In innate immunity, alpha 2 beta 1 binding to C1q initiates the complement cascade and costimulates mast cell activation, triggering neutrophil influx (4, 12).