ER-phagy regulation of immune response: mechanisms and significance - Despite increased clinical awareness, sepsis remains a leading cause of death and high healthcare costs worldwide. Sepsis is a life-threatening condition characterized by an exaggerated immune response to infection, which can lead to organ dysfunction and even death. However, the inflammatory response pathways and molecular mechanisms that underlie the disease remain largely unresolved. Autophagy of endoplasmic reticulum (ER-phagy) serves as a disposal pathway for misfolded proteins and has been implicated in various diseases, including diabetes, cancer, metabolic diseases, and some neurological disorders. Using ER-phagy receptor Fam134b knockout mice, we have identified a novel and essential role of ER-phagy in the host immune response during sepsis. Our findings indicate that depletion of FAM134B entirely abolished NLRP3 (Nucleotide-binding oligomerization domain-Like Receptor containing Pyrin domain 3) inflammasome activation and the generation of IL-1β in macrophages. Additionally, Fam134b knockout mice exhibited higher survival rates, less lung injury, lower bacterial load, and lower levels of proinflammatory cytokines in experimental models of sepsis. Notably, septic patients show upregulation of NLRP3 gene in peripheral blood monocytes and elevated levels of IL-1β and IL-18 in the blood. We propose the central hypothesis that sepsis induces macrophage ER-phagy, driving NLRP3 inflammasome activation, cytokine release, and inflammatory tissue injury. We will use state-of-the-art methods, including intravital microscopy, adoptive macrophage transplantation, and macrophage RNA sequencing, to investigate these hypotheses and validate them in human sepsis samples. Our proposal is organized into three specific aims. 1) To define the role of macrophage ER-phagy in NLRP3 inflammasome activation and lung inflammatory injury during sepsis. 2) To decipher the molecular mechanisms by which ER-phagy drives NLRP3 inflammasome activation. 3) To test the therapeutic potential of targeting macrophage ER-phagy for the treatment of septic injury. The successful completion of our proposed studies has significant potential to impact the future development of novel therapeutic strategies for bacterial sepsis, ultimately improving patient outcomes and decreasing the burden of this life-threatening disease on global healthcare systems.
