Malate initiates a proton-sensing pathway essential for pH regulation of inflammation
Yujianan Chen, Ruihua Shi, Yuan-cai Xiang, Fan Li, Hong Tang, Gang He, Mei Zhou, Feng Xu, Jindong Tan, Pan Huang, Xiao Ye, Kun Zhao, Wen-yu Fu, Liuli Li, Xuting Bian, Huan Chen, Feng Wang, Teng Wang, Chenke Zhang, Binghua Zhou, Wan Chen, Taotao Liang, Jing-tong Lv, Xia Kang, Youxing Shi, E.-A. Kim, Yin-hua Qin, Aubryanna Hettinghouse, Kaidi Wang, Xiangli Zhao, Mingyu Yang, Yunqing Tang, Hai‐long Piao, Lin Guo, Liu C, Hongming Miao, Kanglai Tang
Abstract
Metabolites can double as a signaling modality that initiates physiological adaptations. Metabolism, a chemical language encoding biological information, has been recognized as a powerful principle directing inflammatory responses. Cytosolic pH is a regulator of inflammatory response in macrophages. Here, we found that L-malate exerts anti-inflammatory effect via BiP-IRF2BP2 signaling, which is a sensor of cytosolic pH in macrophages. First, L-malate, a TCA intermediate upregulated in pro-inflammatory macrophages, was identified as a potent anti-inflammatory metabolite through initial screening. Subsequent screening with DARTS and MS led to the isolation of L-malate-BiP binding. Further screening through protein‒protein interaction microarrays identified a L-malate-restrained coupling of BiP with IRF2BP2, a known anti-inflammatory protein. Interestingly, pH reduction, which promotes carboxyl protonation of L-malate, facilitates L-malate and carboxylate analogues such as succinate to bind BiP, and disrupt BiP-IRF2BP2 interaction in a carboxyl-dependent manner. Both L-malate and acidification inhibit BiP-IRF2BP2 interaction, and protect IRF2BP2 from BiP-driven degradation in macrophages. Furthermore, both in vitro and in vivo, BiP-IRF2BP2 signal is required for effects of both L-malate and pH on inflammatory responses. These findings reveal a previously unrecognized, proton/carboxylate dual sensing pathway wherein pH and L-malate regulate inflammatory responses, indicating the role of certain carboxylate metabolites as adaptors in the proton biosensing by interactions between macromolecules.