A new function for MAP4K4 inhibitors during platelet aggregation and platelet-mediated clot retraction

Abstract

Mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4) is implicated in type 2 diabetes mellitus, insulin tolerance, inflammation, cancer, and atherosclerosis. We found that GNE 495 and PF 06260933 (both potent and selective MAP4K4 inhibitors) regulated human platelet activation. Immunoblotting revealed human platelets express MAP4K4, and that GNE 495 and PF 06260933 inhibited collagen-, ADP-, and thrombin-induced platelet aggregation and eventually suppressed granule release, TXA₂ generation, integrin α_IIbβ₃ activation, and clot retraction. In addition, both inhibitors elevated intracellular levels of cAMP, and coincubation with GNE 495 and aspirin or dipyridamole (a phosphodiesterase inhibitor) synergistically inhibited collagen-induced platelet aggregation and TXA₂ generation. Moreover, both inhibitors phosphorylated VASP (ser¹⁵⁷), IP3 receptor, and PKA and attenuated MAPK and PI3K/Akt/GSK3β signaling pathways. This study is the first to demonstrate that MAP4K4 inhibitors reduce thrombus formation by inhibiting platelet activation. These findings also suggest MAP4K4 be considered an emerging target protein for the treatment of thrombosis.

Keywords: MAP4K4; Platelet aggregation; TXA(2); Thrombosis; cAMP.