TIGAR suppresses ER stress-induced neuronal injury through targeting ATF4-signaling in cerebral ischemia/reperfusion.

Abstract

Endoplasmic reticulum (ER) stress is crucial in cerebral ischemia/reperfusion injury by triggering cellular apoptosis and exacerbating neuronal damage. This study elucidates the dynamics of TP53-induced glycolysis and apoptosis regulator (TIGAR) translocation and its role in regulating neural fate during cerebral ischemia-induced ER stress, specifically in male mice. We found enhanced nuclear localization of TIGAR in neurons after transient middle cerebral artery occlusion/reperfusion (tMCAO/R) in male mice, as well as oxygen glucose deprivation/reperfusion (OGD/R) and treatment with ER stress inducer (tunicamycin and thapsigargin) in neuronal cells. Conditional neuronal knockdown of Tigar aggravated the injury following ischemia-reperfusion, whereas overexpression of Tigar attenuated cerebral ischemic injury and ameliorated intra-neuronal ER stress. Additionally, TIGAR overexpression reduced the elevation of ATF4 target genes and attenuated ER stress-induced cell death. Notably, TIGAR co-localized and interacted with ATF4 in the nucleus, inhibiting its downstream pro-apoptotic gene transcription, consequently protecting against ischemic injury. In vitro and in vivo experiments revealed that ATF4 overexpression reversed the protective effects of TIGAR against cerebral ischemic injury. Intriguingly, our study identified the Q141/K145 residues of TIGAR, crucial for its nuclear translocation and interaction with ATF4, highlighting a novel aspect of TIGAR's function distinct from its known phosphatase activity or mitochondrial localization domains. These findings reveal a novel neuroprotective mechanism of TIGAR in regulating ER stress through ATF4-mediated signaling pathways. These insights may guide targeted therapeutic strategies to protect neuronal function and alleviate the deleterious effects of cerebral ischemic injury.Significance statement TIGAR (TP53-induced glycolysis and apoptosis regulator) is one of the downstream target genes of p53, and its encoded protein exerts Fru-2, 6-BPase activity to promote glucose metabolic flux to pentose phosphate pathway. However, the non-enzymatic function of TIGAR has been gradually discovered. Here, we demonstrate that TIGAR translocates to the nucleus to interact with ATF4 in neurons after cerebral ischemia/reperfusion induced ER stress via its Q141/K145 residues. Then TIGAR inhibits ATF4's downstream pro-apoptotic genes expression, reduces ER stress-dependent apoptosis, consequently alleviating neuronal damage. This study uncovered a novel neuroprotective mechanism of TIGAR by regulating ER stress via ATF4-mediated signaling pathway. The Q141/K145 residues of TIGAR are critical for its interaction with ATF4 and inhibition of ATF4 target genes.