TNIK as a Molecular Switch Regulating Platelet Function in Hemostasis and Hyperlipidemia-Associated Thrombosis

Platelets must balance hemostatic function with pathological thrombosis, particularly under metabolic stress conditions. Mitogen-activated protein kinases (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/f PF4-Cre+) and evaluated platelet function, hemostasis, and thrombosis under normal and hyperlipidemic conditions using chimeric Tnikf/f PF4-Cre+ Apoe-/-mice fed high-fat diets. TNIK-deficient mice exhibited prolonged bleeding times, delayed arterial thrombosis and platelet activation under normal conditions, primarily due to impaired dense granule secretion. Mechanistically, TNIK interacted with JNK-interacting protein 1 (JIP1) to promote MLK3/MKK4/JNK pathway activation during hemostatic responses. Surprisingly, under hyperlipidemic conditions, TNIK deficiency accelerated thrombosis and enhanced platelet responses to oxidized low-density lipoprotein (ox-LDL). In this context, TNIK specifically bound to protein kinase C epsilon (PKCε) and suppressed the NOX2/ROS/ERK5 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.