CD61, also known as integrin beta 3 and glycoprotein IIIa (gpIIIa), is a 90 kDa type I integral transmembrane glycoprotein. As a member of the integrin family, it associates with platelet glycoprotein IIb (CD41) to form the CD41/CD61 complex (integrin αIIbβ3), and with integrin alpha V (CD51) to form the αVβ3 integrin (CD51/CD61). The CD41/CD61 complex is expressed on platelets and megakaryocytes, where it mediates platelet activation and aggregation through interactions with fibrinogen, fibronectin, von Willebrand factor (vWF), and other RGD-containing adhesion molecules. The CD51/CD61 integrin is expressed on platelets, osteoclasts, fibroblasts, macrophages, and tumor cells involved in metastasis and adenovirus infection, where it binds to RGD motifs present in extracellular matrix proteins.
