STAT3 Serine phosphorylation is required for TLR4 metabolic reprogramming and IL-1β expression

Abstract

Detection of microbial components such as lipopolysaccharide (LPS) by Toll-like receptor (TLR)-4 expressed on macrophages induces a robust pro-inflammatory response which has recently been shown to be dependent on metabolic reprogramming ^{1, 2, 3, 4} . These innate metabolic changes have been compared to the Warburg effect (also known as aerobic glycolysis) described in tumour cells ^{5, 6} . However, the mechanisms by which TLR4 activation leads to mitochondrial and glycolytic reprogramming remain unknown. Here we show that TLR4 activation induces a signalling cascade recruiting TRAF6 and TBK-1, while TBK-1 phosphorylates STAT3 on S727. Using a genetically engineered mouse model incapable of undergoing STAT3 Ser727 phosphorylation, we show both ex vivo and in vivo that STAT3 Ser727 phosphorylation is critical for LPS-induced glycolytic reprogramming, the production of the central immune-metabolite succinate and inflammatory cytokine production in a model of LPS-induced inflammation. Our study identifies non-canonical STAT3 activation as the crucial signalling intermediary for TLR4-induced glycolysis, macrophage metabolic reprogramming and inflammation.