TIGAR suppresses ER stress-induced neuronal injury through targeting
ATF4-signaling in cerebral ischemia/reperfusion
Abstract
Abstract Background and Purpose Previous studies have shown that TIGAR
(TP53-induced glycolysis and apoptosis regulator) protects against
cerebral ischemia/reperfusion injury via the improvement of the redox
and energy homeostasis of neurons. TIGAR is found in the endoplasmic
reticulum (ER) and nucleus but its role in ER stress is unclear. This
study aimed to investigate the ER and nuclear translocation of TIGAR
during ER stress and the influences of the nuclear TIGAR in cerebral
ischemia/reperfusion-induced ER stress. Experimental Approach Mice were
subjected to the middle cerebral artery occlusion/reperfusion. Cultured
neurons were treated with oxygen and glucose deprivation, tunicamycin or
thapsigargin. Key Results The increases in ATF4 target genes and ER
stress-induced neuronal apoptosis were reduced by overexpression of
TIGAR. Furthermore, increases in the localization of TIGAR and ATF4 to
the nucleus were observed after in vitro and in vivo cerebral
ischemia/reperfusion or ER stress models. The nuclear TIGAR interacts
with ATF4 and inhibits the transcription of downstream pro-apoptotic
genes of ATF4, resulting in protection against cerebral
ischemia/reperfusion injury. Intriguingly, the translocation of TIGAR to
the ER and nucleus and inhibition of the transcription of ATF4 is depend
on Q141/K145 of TIGAR instead of its phosphatase activity and
mitochondrial localization domains. Conclusion and Implications These
results suggest that TIGAR translocates to the ER and the nucleus to
interact with ATF4 after cerebral ischemia-reperfusion induced ER stress
via its Q141/K145. The study uncovered a novel neuroprotective mechanism
of TIGAR through regulating ER stress via a ATF4-mediated signaling
pathway.