Fig. 5.

Role of GPIbα in platelet formation. GPIbα contributes to megakaryocytopoiesis and localization of megakaryocytes at the sinusoidal vessels. GPIbα regulates Cdc42 and RhoA activity, which is essential for a proper transendothelial proplatelet formation. Subsequently, proplatelets have to separate into platelets under high shear forces and this requires the binding of GPIbα to VWF. Aged and desialylated platelets bind to the hepatic Ashwell-Morell receptor (AMR) which leads to JAK2/STAT3 signaling and finally thrombopoietin generation and secretion from hepatocytes. Thrombopoietin, in turn, expedites megakaryocyte maturation and proplatelet formation