RETREG1/FAM134B-mediated ERGICphagy regulates GSDME-dependent dendritic cell pyroptosis during sepsis

During the development of sepsis, aberrant dendritic cell (DC) pyroptosis results in a significant decrease in the numbers of DCs and immune dysfunction. However, the molecular mechanisms regulating DC pyroptosis in sepsis remain unclear. Emerging evidence indicates that RETREG1/FAM134B (reticulophagy regulator 1) is involved in the regulation of programmed cell death to maintain cell viability. Therefore, this study aimed to investigate the potential role and regulatory pathways of RETREG1 in DC death during sepsis. We found that the upregulation of RETREG1 upon septic challenge was intimately associated with the maintenance of immune function. Depletion of RETREG1 in DC significantly aggravated DC pyroptosis and sepsis-induced immune dysfunction by activating the CASP3 (caspase 3)-GSDME (gasdermin E) signaling pathway. Mechanistically, defective RETREG1 expression inhibited autophagic degradation of the endoplasmic reticulum-Golgi intermediate compartment (ERGIC), resulting in abnormal activation of STING1 (stimulator of interferon response cGAMP interactor 1), which further induced CASP3-GSDME-dependent pyroptosis. Genetic downregulation of Tmed9 prevented the activation of STING1 and GSDME-mediated pyroptosis by disturbing ERGIC structure. These results suggest a novel RETREG1-based protective mechanism against DC-mediated immune impairment during sepsis. Genetic or pharmacological modulation of RETREG1 May represent a promising therapeutic strategy for treating sepsis-induced immune suppression.Abbreviations: 7-AAD: 7-aminoactinomycin D; ANXA5/annexin V: annexin A5; ARF1: ARF GTPase 1; ATP: adenosine triphosphate; CALCOCO1: calcium binding and coiled-coil domain 1; CASP1: caspase 1; cC3: cleaved CASP3; CCDC50: coiled-coil domain containing 50; CD274/PD-L1: CD274 molecule; CFSE: carboxyfluorescein diacetate succinimidyl ester; CGAS: cyclic GMP-AMP synthase; CLP: cecal ligation and puncture; DC: dendritic cell; DEGs: differentially expressed genes; DEPs: differently expressed proteins; ER: endoplasmic reticulum; ERGIC: endoplasmic reticulum-Golgi intermediate compartment; GO: Gene Ontology; GOLGA2/GM130: golgin A2; GSDMD: gasdermin D; GSDME: gasdermin E; GSEA: Gene set enrichment analysis; IFN-I: type I interferon; IKK: IκB kinase; IL2: interleukin 2; IRF3: interferon regulatory factor 3; ITGAX/Cd11c: integrin subunit alpha X; KEGG: Kyoto Encyclopedia of Genes and Genomes; LMAN1/ERGIC53: lectin, mannose binding 1; LPS: lipopolysaccharide; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MAP3K7/TAK1: mitogen-activated protein kinase kinase kinase 7; NFKB/NFκB: nuclear factor kappa B; NLRP3: NLR family pyrin domain containing 3; PBMCs: peripheral blood mononuclear cells; PBS: phosphate-buffered saline; PCD: programmed cell death; PINK1: PTEN induced kinase 1; PRKN: parkin RBR E3 ubiquitin protein ligase; PRRs: pattern recognition receptors; PYCARD/ASC: PYD and CARD domain containing; RETREG1/FAM134B: reticulophagy regulator 1; SAMHD1: SAM and HD domain containing deoxynucleoside triphosphate triphosphohydrolase 1; SEC62: SEC62 preprotein translocation factor; SQSTM1/p62: sequestosome 1; STEEP1: STING1 ER exit protein 1; STING1: stimulator of interferon response cGAMP interactor 1; TBK1: TANK binding kinase 1; TGFB/TGFβ: transforming growth factor beta; TMED9: transmembrane p24 trafficking protein 9; TLR4: toll like receptor 4; TNF: tumor necrosis factor; T_regs: regulatory T cells; VAP: VAMP associated protein.