Recombinant Mouse Glycoprotein V/CD42d Protein, CF

Platelet Glycoprotein V (GPV or GP5, designated CD42d) is an 83 kDa type I transmembrane (TM) glycoprotein of the leucine-rich repeat (LRR) family (1, 2). It is expressed exclusively within the platelet / megakaryocyte lineage, where it noncovalently interacts with other platelet TM LRR proteins, GPIb alpha / beta and GPIX, at a ratio of one GPV to two of each other subunit (2). The GPI-V-IX complex tethers platelets to von Willebrand factor on the surface of injured endothelial cells. Absence of the complex results in Bernard-Soulier syndrome, a rare bleeding disorder (1 - 3). The mouse GPV cDNA encodes 567 amino acids (aa), including a 16 aa signal sequence, a 506 aa extracellular domain (ECD) containing 15 LRR, a 21 aa TM sequence, and a short (24 aa) cytoplasmic tail that binds calmodulin in resting, but not activated platelets. The mouse GPV ECD shares 70%, 87%, 68 and 67% aa identity with human, rat, equine and bovine GPV, respectively. GPV can form soluble fragments of 80 kDa by ADAM10 or ADAM17 cleavage after L508, or 69 kDa by thrombin cleavage after R476 (1, 4, 5). High circulating soluble GPV may be an indicator of platelet activation, but may also be caused by high doses of aspirin (6 - 8). The function of GPV is not entirely clear. Deletion of GPV in mice does not produce any obvious change to surface expression or function of GPIb and GPIX, but surface expression of GPV requires GPIb (9, 10). Deletion studies also indicate that GPV may play a minor role in collagen adhesion, and may modify platelet aggregation in response to thrombin (3, 11 ‑ 15).