Nucleic Acid Sensing Promotes Inflammatory Monocyte Migration Through Biased Coagulation Factor VIIa Signaling

Protease activated receptors (PARs) are cleaved by coagulation proteases and thereby connect hemostasis with innate immune responses. Signaling of the tissue factor (TF) complex with factor VIIa (FVIIa) via PAR2 stimulates extracellular signal -regulated kinase (ERK) activation and cancer cell migration, but functions of cell autonomous TF-FVIIa signaling in immune cells are unknown. Here, we show that myeloid cell expression of FVII but not of FX is crucial for in fl ammatory cell recruitment to the alveolar space after challenge with the double -stranded viral RNA mimic polyinosinic:polycytidylic acid [Poly(I:C)]. In line with these data, genetically modi fi ed mice completely resistant to PAR2 cleavage but not FXa-resistant PAR2-mutant mice are protected from lung in fl ammation. Poly(I:C)-stimulated migration of monocytes/macrophages is dependent on ERK activation and mitochondrial antiviral s ignaling (MAVS) but independent of toll -like receptor 3 (TLR3). Monocyte/macrophage-synthesized FVIIa cleaving PAR2 is required for integrin a M 13 2 -dependent migration on fi brinogen but not for integrin 13 1 -dependent migration on fi bronectin. To further dissect the downstream signaling pathway, we generated PAR2 S365/T368A -mutant mice de fi cient in 13- arrestin recruitment and ERK scaffolding. This mutation reduces cytosolic, but not nuclear ERK phosphorylation by Poly(I:C) stimulation, and prevents macrophage migration on fi brinogen but not fi bronectin after stimulation with Poly(I:C) or CpG-B, a single -stranded DNA TLR9 agonist. In addition, PAR2 S365/T368A -mutant mice display markedly reduced immune cell recruitment to the alveolar space after Poly(I:C) challenge. These results identify TF-FVIIa-PAR2- 13- arrestin-biased signaling as a driver for lung in fi ltration in response to viral nucleic acids and suggest potential therapeutic interventions speci fi cally targeting TFVIIa signaling in thrombo-in fl ammation.