ITGB3 (INTEGRIN, BETA-3), also called GP3A, GPIIIa, CD61, is a protein that in humans is encoded by the ITGB3 gene. GP3A is a cluster of differentiation found on thrombocytes.The ITGB3 complex belongs to the integrin class of cell adhesion molecule receptors that share a common heterodimeric structure with alpha and beta subunits. The GP3A gene is mapped to 17q21.32. And the GP3A gene has 14 exons. The 3-prime exon is larger than 1,700 nucleotides and contains the 3-prime untranslated region. The ITGB3 complex mediates platelet aggregation by acting as a receptor for fibrinogen. Although the ITGB3 is expressed on the cell surface at normal levels and is capable of function following extracellular stimulation, it could not be activated via the 'inside-out' signaling pathways.