Adenylate kinase 4 is critical to the function of classically activated macrophage

Macrophage plays a crucial role in the front line of host defense against pathogens. Classically activated macrophages (M1), induced by IFN-g and LPS, highly express inflammatory cytokines and contribute to inflammatory processes. By contrast, alternatively activated macrophages (M2) are induced by IL-4/IL-13, produce IL-10, and display anti-inflammatory activity. Adenylate kinase 4 (Ak4), an enzyme that transfers phosphate group among ATP/GTP, AMP, and ADP, is a key modulator of ATP. Ak4 is involved in maintaining the homeostasis of cellular nucleotides which is essential for cellular function. We observed Ak4 is preferentially expressed in M1 macrophages compared to M2 macrophages. Whether Ak4 is critical for M1 macrophage function remains elusive. Here we demonstrated that Ak4 maintained ATP homeostasis, and was critical for ROS production, glycolysis, and bactericidal ability in M1 macrophages. Moreover, Ak4 promoted the expression of inflammatory genes, including Il1b, Il6, Tnfa, Nos2, Nox2and Hif1a, in M1 macrophages via Hif1a and AMPK. However, Ak4 deficiency did not affect the development of murine immune cells. Taken together, our data depict a potential mechanism linking nucleotide homeostasis and the function of M1 macrophage. Taiwan Ministry of Science and Technology (111-2320-B-002-068-MY3)