TNIK as a molecular switch regulating platelet function in hemostasis and hyperlipidemia-associated thrombosis

ABSTRACT: Platelets must balance hemostatic function with pathological thrombosis, particularly under metabolic stress conditions. MAPKs are central to platelet responses, but how these platelet signals differentially regulate hemostasis remains poorly understood. To investigate the role of Traf2/Nck-interacting kinase (TNIK), we generated megakaryocyte/platelet-specific TNIK knockout mice (Tnikf/fPF4-Cre+) and evaluated platelet function, hemostasis, and thrombosis under normal and hyperlipidemic conditions using chimeric Tnikf/fPF4-Cre+Apoe-/-mice fed high-fat diets. TNIK-deficient mice exhibited prolonged bleeding times, delayed arterial thrombosis and reduced platelet activation under normal conditions, primarily due to impaired dense granule secretion. Mechanistically, TNIK interacted with c-Jun N-terminal kinase interacting protein 1 to promote mixed lineage kinase 3/mitogen-activated protein kinase kinase 4/c-Jun N-terminal kinase pathway activation during hemostatic responses. Surprisingly, under hyperlipidemic conditions, TNIK deficiency accelerated thrombosis and enhanced platelet responses to oxidized low-density lipoprotein. In this context, TNIK specifically bound to protein kinase C ε and suppressed the NADPH oxidase 2/reactive oxygen species/extracellular signal-regulated kinase 5 pathway, thereby inhibiting excessive platelet activation. We conclude that TNIK functions as a molecular switch in platelets, promoting normal hemostasis while simultaneously preventing hyperlipidemia-associated thrombosis through distinct signaling pathways. This dual regulatory mechanism provides insight into how platelets balance hemostatic function with pathological thrombosis risk and identifies TNIK as a potential therapeutic target in metabolic thrombotic disorders.