Nuclear fragile X mental retardation-interacting protein 1-mediated ribophagy protects T lymphocytes against apoptosis in sepsis

BACKGROUND: Ribophagy is a selective autophagic process that specifically degrades dysfunctional or superfluous ribosomes to maintain cellular homeostasis. Whether ribophagy can ameliorate the immunosuppression in sepsis similar to endoplasmic reticulum autophagy (ERphagy) and mitophagy remains unclear. This study was conducted to investigate the activity and regulation of ribophagy in sepsis and to further explore the potential mechanism underlying the involvement of ribophagy in T-lymphocyte apoptosis. METHODS: The activity and regulation of nuclear fragile X mental retardation-interacting protein 1 (NUFIP1)-mediated ribophagy in T lymphocytes during sepsis were first investigated by western blotting, laser confocal microscopy and transmission electron microscopy. Then, we constructed lentivirally transfected cells and gene-defective mouse models to observe the impact of NUFIP1 deletion on T-lymphocyte apoptosis and finally explored the signaling pathway associated with T-cell mediated immune response following septic challenge. RESULTS: Both cecal ligation and perforation-induced sepsis and lipopolysaccharide stimulation significantly induced the occurrence of ribophagy, which peaked at 24 h. When NUFIP1 was knocked down, T-lymphocyte apoptosis was noticeably increased. Conversely, the overexpression of NUFIP1 exerted a significant protective impact on T-lymphocyte apoptosis. Consistently, the apoptosis and immunosuppression of T lymphocytes and 1-week mortality rate in NUFIP1 gene-deficient mice were significantly increased compared with those in wild-type mice. In addition, the protective effect of NUFIP1-mediated ribophagy on T lymphocytes was identified to be closely related to the endoplasmic reticulum stress apoptosis pathway, and PERK–ATF4–CHOP signaling was obviously involved in downregulating T-lymphocyte apoptosis in the setting of sepsis. CONCLUSIONS: NUFIP1-mediated ribophagy can be significantly activated to alleviate T lymphocyte apoptosis through the PERK–ATF4–CHOP pathway in the context of sepsis. Thus, targeting NUFIP1-mediated ribophagy might be of importance in reversing the immunosuppression associated with septic complications.