Erythrocyte transglutaminase-2 combats hypoxia and chronic kidney disease by promoting oxygen delivery and carnitine homeostasis

Due to lack of nuclei and de novo protein synthesis, post-translational modification (PTM) is imperative for erythrocytes to regulate oxygen (O-2) delivery and combat tissue hypoxia. Here, we report that erythrocyte transglutminase-2 (eTG2)-mediated PTM is essential to trigger O-2 delivery by promoting bisphosphoglycerate mutase proteostasis and the Rapoport-Luebering glycolytic shunt for adaptation to hypoxia, in healthy humans ascending to high altitude and in two distinct murine models of hypoxia. In a pathological hypoxia model with chronic kidney disease (CKD), eTG2 is critical to combat renal hypoxia-induced reduction of Slc22a5 transcription and OCNT2 protein levels via HIF-1 alpha-PPAR alpha signaling to maintain carnitine homeostasis. Carnitine supplementation is an effective and safe therapeutic approach to counteract hypertension and progression of CKD by enhancing erythrocyte O-2 delivery. Altogether, we reveal eTG2 as an erythrocyte protein stabilizer orchestrating O-2 delivery and tissue adaptive metabolic reprogramming and identify carnitine-based therapy to mitigate hypoxia and CKD progression.