TIGAR Regulates Intestinal Mucus Barrier Integrity by Inhibiting Lactylation of G6PD/6PGD in Ulcerative Colitis
Oxidative stress and metabolic dysregulation in goblet cells represent significant contributors to the pathogenesis of ulcerative colitis (UC). TIGAR (TP53-induced glycolysis and apoptosis regulator) plays a critical role as a metabolic regulatory enzyme by promoting NADPH synthesis, thereby counteracting oxidative stress. However, the precise mechanisms through which TIGAR regulates NADPH synthesis and its impact on UC remain incompletely understood. Here, we demonstrate that TIGAR inhibits the lactylation of glucose-6-phosphate dehydrogenase (G6PD) and 6-phosphogluconate dehydrogenase (6PGD), both pivotal enzymes in the NADPH biosynthesis pathway, hence preserving their enzymatic activities. We further identify specific lactylation sites at lysine 453 (K453) in G6PD and lysine 38 (K38) in 6PGD. Lactylation modifications impact the formation of G6PD homodimers and the binding of 6PGD with NADP+. In UC mice, persistently low TIGAR expression results in elevated lactic acid levels, which enhance the lactylation of G6PD and 6PGD, inhibit NADPH synthesis, and exacerbate oxidative stress in goblet cells. Consequently, these alterations lead to a reduction in thioredoxin 1 (Trx1) reductase activity, inducing S-nitrosylation of anterior gradient homolog 2 (AGR2), a key enzyme involved in MUC2 modification, thus impeding mature MUC2 production and compromising the integrity of the intestinal mucus barrier. Overall, our study elucidates the critical mechanisms by which TIGAR regulates NADPH synthesis, provides novel insights into how TIGAR maintains cellular redox homeostasis, and offers experimental evidence for considering TIGAR as a potential target for UC therapy.