RETREG1-Mediated Reticulophagy is Essential for Dendritic Cell Maturation and Function in Sepsis

Dendritic cells (DCs) are crucial antigen-presenting cells that mediate the interplay between innate and adaptive immunity during lethal infections. Here, we report the key role of reticulophagy regulator 1 (RETREG1), a selective autophagy receptor, in maintaining DC maturation and function in the early stage of sepsis. Mechanistically, activating transcription factor 6 (ATF6) acts as a direct transcription factor regulating RETREG1 expression in response to bacterial lipopolysaccharide-induced endoplasmic reticulum (ER) stress. RETREG1-mediated reticulophagy reduces excessive ER stress via the eukaryotic translation initiation factor 2 alpha kinase 3 (EIF2AK3) signaling pathway and inhibits membrane-associated RING-CH-type finger 8 (MARCH8)-dependent major histocompatibility complex class II (MHC-II) ubiquitination to maintain antigen presentation in DCs. Consequently, Cd11c^creRetreg1^fl/fl, Retreg1^-/-, and Atf6^-/- mice exhibit impaired DC function, leading to immunosuppression and multiple organ failure in experimental sepsis. Exploration of samples from septic patients, combined with single-cell bioinformatics analysis, further suggests that a deficit in reticulophagy in DCs is associated with the development of human sepsis.