TRK-fused gene (TFG) regulates ULK1 stability via TRAF3-mediated ubiquitination and protects macrophages from LPS-induced pyroptosis

Abstract

TRK-fused gene (TFG) is known to be involved in protein secretion and plays essential roles in an antiviral innate immune response. However, its function in LPS-induced inflammation and pyroptotic cell death is still unknown. Here, we reported that TFG promotes the stabilization of Unc-51 like autophagy activating kinase (ULK1) and participates in LPS plus nigericin (Ng) induced pyroptotic cell death. Our results showed that TFG-deficient THP-1 macrophages exhibit higher mitochondrial ROS production. LPS/Ng stimulation triggers a much higher level of ROS and induces pyroptotic cell death. ULK1 undergoes a rapid turnover in TFG-deficient THP-1 cells. TFG forms complex with an E3 ligase, tumor necrosis factor receptor-associated factor 3 (TRAF3), and stabilizes ULK1 via disturbing ULK1-TRAF3 interaction. Knockdown of TFG facilitates the interaction of ULK1 with TRAF3 and subsequent K48-linked ULK1 ubiquitination and proteasome degradation. Rescue of ULK1 expression blocks LPS/Ng-induced cell death in TFG-deficient THP-1 macrophages. Taken together, TFG plays an essential role in LPS/Ng-induced pyroptotic cell death via regulating K48-linked ULK1 ubiquitination in macrophages.

Platelet-Rich Fibrin Reduces IL-1β Release from Macrophages Undergoing Pyroptosis

“…While ATP is related to the strong increase in the IL-1β release in the LPS-primed macrophages [ 18 , 32 ], other compounds were indicated to play important roles in the pyroptosis pathway, such as α-hemolysin [ 37 , 38 , 39 ] and nigericin [ 40 , 41 ], either alone or in combination with other pathogen-associated molecular patterns (PAMPs). Alpha-hemolysin is a bacterial pore-forming toxin produced by Staphylococcus , which activates inflammasome activity and caspase-1, thus inducing pyroptosis [ 38 , 42 ].…”

“…Nigericin is a microbial toxin produced by Streptomyces hygroscopicus that decreases intracellular potassium, which causes caspase-1 activation and induces the release of IL-1β, leading to pyroptosis [ 30 , 43 ]. Studies on macrophages have been trying to find molecules to reduce pyroptosis in LPS-primed ATP/α-hemolysin/nigericin-stimulated cells [ 41 ] or even exacerbate pyroptosis cell death due to the potential application in anti-infection or anti-tumour immunity [ 40 ]. Nevertheless, this topic is relatively new in periodontal research.…”

Comprehensive analysis of pyroptotic gene prognostic signatures associated with tumor immune microenvironment and genomic mutation in breast cancer

“…A review in 2021 summarizes that ubiquitination can dynamically regulate inflammation and programmed cell death, which is deemed as the crucial components of TNF-stimulated cell death and NLRP3 inflammasome–mediated signaling ( 55 ). Besides, a distinct connection between TRAF3 (tumor necrosis factor receptor-associated factor 3)-mediated ULK1 (Unc-51 like autophagy activating kinase) ubiquitination in macrophages and pyroptosis was found ( 56 , 57 ). Reportedly, human papillomavirus E7 can recruit E3 ligase TRIM21 to induce degradation and ubiquitination of IFI16 inflammasome, resulting in suppression of cell pyroptosis and occurrence of immune escape ( 58 ).…”

Degradation Mechanism of Autophagy-Related Proteins and Research Progress

“…Tumor necrosis factor receptor-associated factor 3 (TRAF3) is a member of the TRAF family with E3 ligase activity. In macrophages, TRAF3 mediates K48-linked ULK1 ubiquitination and proteasomal degradation, and the TRK-fused gene (TFG)-TRAF3 complex is able to interfere with TRAF3-ULK1 interaction to stabilize ULK1 in response to lipopolysaccharide (LPS)-induced pyroptosis [58]. Neural precursor cell expressed developmentally downregulated 4-like (NEDD4L) is an E3 ubiquitin ligase containing a HECT domain.…”