Xianjing Li, Duowei Wang, Zhen Chen, Ermei Lu, Zhuo Wang, Jingjing Duan, Wei Tian, Yun Wang, Linjun You, Yulian Zou, Yan Cheng, Qingyi Zhu, Xiaojian Wan, Tao Xi, Meisheng Jiang, Yuyuan Han, Cong Cao, Lutz Birnbaumer, Wen-Ming Chu, and Yong Yang
Heterotrimeric G proteins have been implicated in Toll-like receptor 4 (TLR4) signaling in macrophages and endothelial cells. However, whether guanine nucleotide-binding protein G(i) subunit alpha-1 and alpha-3 (Gαi1/3) are required for LPS responses remains unclear, and if so, the underlying mechanisms need to be studied. In this study, we demonstrated that, in response to LPS, Gαi1/3 form complexes containing the pattern recognition receptor (PRR) CD14 and growth factor receptor binding 2 (Grb2)-associated binding protein (Gab1), which are required for activation of PI3K-Akt signaling. Gαi1/3 deficiency decreased LPS-induced TLR4 endocytosis, which was associated with decreased phosphorylation of IFN regulatory factor 3 (IRF3). Gαi1/3 knockdown in bone marrow-derived macrophage cells (Gαi1/3 KD BMDMs) exhibited an M2-like phenotype with significantly suppressed production of TNF-α, IL-6, IL-12, and NO in response to LPS. The altered polarization coincidedwith decreased Akt activation. Further, Gαi1/3 deficiency caused LPS tolerance in mice. In vitro studies revealed that, in LPS-tolerant macrophages, Gαi1/3 were down-regulated partially by the proteasome pathway. Collectively, the present findings demonstrated that Gαi1/3 can interact with CD14/Gab1, which modulates macrophage polarization in vitro and in vivo. Fil: Li, Xiaolin. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Wang, Duowei. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Chen, Zen. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Lu, Ermei. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Wang, Zhuo. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Duan, Jingjing. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Tian, Wei. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Wang, Yun. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: You, Linjun. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Zou, Yulian. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Cheng, Yan. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Zhu, Qingyi. Jiangsu Province Hospital of Traditional Chinese Medicine. Departament of Urology; China Fil: Wan, Xiaojian. Second Military Medical University. Department of Anesthesiology and Intensive Care Medicine, Changhai Hospita; China Fil: Xia, Tao. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China Fil: Birnbaumer, Lutz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. National Institute of Environmental Health Sciences. Laboratory of Neurobiology, ; Estados Unidos Fil: Yang, Yong. China Pharmaceutical University. Center for New Drug Safety Evaluation and Research; China