alphaIIbbeta3

alphaIIbbeta3, also known as integrin alphaIIbbeta3 or GPIIb/IIIa, is a cell surface receptor protein that plays a crucial role in blood clot formation. It is a member of the integrin family, which are heterodimeric transmembrane proteins composed of an alpha and a beta subunit. In the case of alphaIIbbeta3, the alpha subunit is designated alphaIIb and the beta subunit is designated beta3.

This receptor is primarily found on the surface of platelets, which are small blood cells essential for hemostasis. The main function of alphaIIbbeta3 is to bind to fibrinogen, a soluble protein in the blood plasma. When platelets are activated, for example, during an injury to a blood vessel, alphaIIbbeta3 undergoes a conformational change that exposes its fibrinogen-binding site. Multiple fibrinogen molecules then bridge between activated platelets, forming a stable platelet aggregate that is the foundation of a blood clot.

The proper functioning of alphaIIbbeta3 is vital for preventing excessive bleeding. Defects in the alphaIIbbeta3 receptor, such as those seen in Glanzmann thrombasthenia, lead to impaired platelet aggregation and a bleeding disorder. Conversely, due to its critical role in platelet aggregation, alphaIIbbeta3 has become a target for antiplatelet drugs used to prevent blood clots in conditions such as heart attacks and strokes. These drugs, like abciximab, block the binding of fibrinogen to alphaIIbbeta3, thereby inhibiting platelet aggregation.