Mechanosensing via a GpIIb/Src/14-3-3ζ axis critically regulates platelet migration in vascular inflammation

Platelets are not only the first responders in thrombosis and hemostasis but also central players in inflammation. Compared with platelets recruited to thrombi, immune-responsive platelets use distinct effector functions including actin-related protein complex 2/3-dependent migration along adhesive substrate gradients (haptotaxis), which prevents inflammatory bleeding and contributes to host defense. How platelet migration in this context is regulated on a cellular level is incompletely understood. Here, we use timeresolved morphodynamic profiling of individual platelets to show that migration, in contrast to clot retraction, requires anisotropic myosin IIa-activity at the platelet rear which is preceded by polarized actin polymerization at the front to initiate and maintain migration. Integrin GPIIb-dependent outside-in signaling via G alpha 13 coordinates polarization of migrating platelets to trigger tyrosine kinase c-Src/14-3-3 zeta-dependent lamellipodium formation and functions independent of soluble agonists or chemotactic signals. Inhibitors of this signaling cascade, including the clinically used ABL/c-Src inhibitor dasatinib, interfere predominantly with the migratory capacity of platelets, without major impairment of classical platelet functions. In murine inflammation models, this translates to reduced migration of platelets visualized by 4D intravital microscopy, resulting in increased inflammation-associated hemorrhage in acute lung injury. Finally, platelets isolated from patients with leukemia treated with dasatinib who are prone to clinically relevant hemorrhage exhibit prominent migration defects, whereas other platelet functions are only partially affected. In summary, we define a distinct signaling pathway essential for migration and provide novel mechanistic insights explaining dasatinib-related platelet dysfunction and bleeding.

Automated summary

Platelets are important in both thrombosis and hemostasis, as well as inflammation. They are involved in migration and host defense, and this migration is regulated by anisotropic myosin IIa-activity and polarized actin polymerization. The signaling pathway involving G alpha 13, c-Src/14-3-3 zeta, and lamellipodium formation plays a key role in platelet migration, and inhibitors of this pathway, such as dasatinib, interfere with platelet migration without affecting other platelet functions. This has implications in inflammation-associated hemorrhage and platelet dysfunction in patients treated with dasatinib.