GPIb-IX and VWF in thrombosis and thrombocytopenia

项目总结

PROJECT SUMMARY Understanding the interplay between blood, vessel, and shear flow is key to elucidate the pathophysiology of thrombosis and related diseases. Both glycoprotein (GP)Ib-IX-V complex, an abundant receptor complex on the platelet surface, and its ligand von Willebrand factor (VWF) in the plasma critically mediate hemostasis, thrombosis, and thrombo-inflammation by sensing and responding to blood shear flow. Although much is known about this important receptor-ligand pair, significant knowledge gaps, especially the molecular mechanisms underlying their activation and regulation, have remained open. As the continuation of two current R01 grants entitled “Structure and function of platelet glycoprotein Ib-IX-V complex” and “Conformational activation of von Willebrand factor”, this proposed R35 project seeks to fill several long-standing knowledge gaps and address controversial questions in our understanding of GPIb- IX-V, VWF and related disease pathology. Through systematic, multidisciplinary analysis of inter-domain interactions in GPIb-IX and VWF, we have recently identified the mechanosensory domain (MSD) in GPIb- IX and the discontinuous autoinhibitory module (AIM) in VWF, leading to elucidation of their respective activation mechanisms. In addition to significant implications on pathophysiology of many related thrombotic and thrombocytopenic disorders, these mechanisms provide a coherent conceptual framework for future mechanistic investigations and novel therapeutic development. In this project, we seek to determine the structure of the GPIb-IX complex and VWF domains, resolve the current controversy about the activation mechanism of VWF particularly the AIM conformation, and elucidate mechanisms that regulate activities of GPIb-IX and VWF. To accomplish these goals, we will continue to develop new reagents targeting a key domain, new constructs enabling interdisciplinary analysis, and new mouse strains bearing key mutations to specifically modulate their activity. The seven-year funding period will provide additional flexibility and continuity for pursuing difficult-to-get structures and developing key reagents. Overall, completion of the proposed study will elucidate the fundamental activation and regulation mechanisms of GPIb-IX-V and VWF, significantly advance our understanding of pathogenesis of many thrombotic and thrombocytopenic diseases, and potentially identify new strategies to develop treatments for these diseases.