GP5 (glycoprotein V) is a platelet glycoprotein that functions as a critical component of the GPIb-V-IX complex, serving as a von Willebrand factor (vWF) receptor. This complex mediates vWF-dependent platelet adhesion to blood vessels, which is essential for hemostasis, particularly in the arterial circulation where platelet adhesion to injured vascular surfaces represents a critical initiating event in blood coagulation. However, recent evidence indicates GP5 has functions beyond its classical platelet role. In breast cancer, GP5 is aberrantly expressed in malignant epithelial cells and functions as an oncogene 1. High GP5 expression correlates with increased nuclear grade, higher TNM stage, and promotes breast cancer cell proliferation, invasion, and metastasis by activating the PI3K/AKT signaling pathway to upregulate epithelial-mesenchymal transition 1. Additionally, in porcine reproductive and respiratory syndrome virus infection, the viral GP5 protein inhibits chaperone-mediated autophagy by targeting LAMP2A, thereby impairing antiviral immune responses 2. These findings reveal GP5 has context-dependent functions: essential for normal hemostasis in platelets but pathological when dysregulated in cancer and manipulated during viral infections.