Yingyu Chen

Transmembrane protein 189 (TMEM189), also known as plasmanylethanolamine desaturase 1 (PEDS1), is involved in plasmalogen biosynthesis, phospholipid metabolism, ferroptosis, and autophagy. However, whether TMEM189/PEDS1 regulates macrophages and disease-related inflammatory responses remains unclear. Here, we for the first time investigated the contribution of TMEM189/PEDS1 to macrophage activation and progression of metabolic dysfunction-associated steatohepatitis (MASH). Experimental data demonstrated that TMEM189 is highly expressed in macrophages, and its inactivation promotes M1 macrophage polarization and increases lipid loading in co-cultured hepatocytes. Loss of Tmem189 in myeloid cells results in a selective increase in the population and activation of monocyte-derived macrophages (MDMs) in the liver, which exacerbates hepatic steatosis, inflammatory damage, and fibrosis in diet-induced MASH mice. The restoration of Tmem189 expression in hepatic macrophages significantly attenuates MASH-related phenotypes. Mechanistically, TMEM189 interacts with fatty acid synthase (FASN), negatively regulates its expression and pro-inflammatory response in macrophages. Further studies revealed that TMEM189 deletion enhances FASN-promoted NLRP3 palmitoylation and its activation, leading to increased IL-1β production, which in turn further accelerates MASH progression. Our findings provide important evidence supporting the critical regulatory role of TMEM189-FASN signaling in liver macrophage activation and MASH progression, which may represent a potential therapeutic target for MASH treatment.

Transmembrane protein 166 (TMEM166), an endoplasmic reticulum (ER)-resident membrane protein, exerts anticancer effects by inducing autophagy and apoptosis. Although tissues of various cancers downregulate its expression, the biological function of TMEM166 in hepatocellular carcinoma (HCC) remains unclear. Herein, we report that TMEM166 negatively regulates unfolded protein response (UPR) in HCC. TMEM166 was noted to interact with ACSL3 to maintain ACSL3 stability and facilitate lipid storage. TMEM166 deletion reduced ACSL3 expression and increased lipid utilisation in the mitochondria through fatty acid β-oxidation (FAO), ultimately boosting ATP production. Moreover, TMEM166 -knockout (KO) cells demonstrated accelerated protein synthesis via the AMPK–mTOR axis. These effects induced sublethal ER stress and UPR activation in TMEM166 -KO cells. Furthermore, TMEM166 KO promoted HCC cell proliferation and sorafenib resistance via UPR activity upregulation. We analysed the clinical significance of TMEM166-regulated UPR in human HCC cells and noted that TMEM166 expression was negatively correlated with the activities of UPR-related transcriptional factors such as ATF4, ATF6 and XBP1s in the cells. This study is the first to elucidate the relationship among TMEM166, ER stress, and HCC and may provide and indicate newer avenues for TMEM166 -targeted gene therapy strategies for HCC treatment.

ELMOD3 (encoding ELMO domain containing 3) is a causative gene associated with human autosomal dominant nonsyndromic and progressive hearing loss. However, the role of ELMOD3 in the occurrence and development of tumors remains unknown. Herein, we observed that inactivation of ELMOD3 in gastric cancer cells significantly inhibited their proliferation, migration, and invasion, and altered cell cycle progression. A xenograft tumor model showed that knockout of ELMOD3 suppressed the tumorigenicity of BGC823 gastric cancer cells in nude mice. Further investigation demonstrated that the ELMO domain of ELMOD3 interacts with β‐catenin, which increases the levels of β‐catenin, promoting downstream target gene expression. Deletion of ELMOD3 in gastric cells decreased the β‐catenin signaling, elevated E‐cadherin levels, suppressed RAF/MEK/ERK signal pathway, and disrupted the formation of F‐actin cytoskeleton. These results led us to propose that ELMOD3 may participate in multiple biological processes in promoting the tumorigenesis of gastric cancer. It exerts a positive role in the regulation of gastric cancer cell proliferation and progression. Thus, ELMOD3 was identified as a potential tumor target, which deserves further investigation.

Transmembrane protein 268 (TMEM268) is a novel, tumor growth-related protein first reported by our laboratory. It interacts with the integrin subunit β4 (ITGB4) and plays a positive role in the regulation of the ITGB4/PLEC signaling pathway. Here, we investigated the effects and mechanism of TMEM268 in anti-infectious immune response in mice. Tmem268 knockout in mice aggravated cecal ligation and puncture-induced sepsis, as evidenced by higher bacterial burden in various tissues and organs, congestion, and apoptosis. Moreover, Tmem268 deficiency in mice inhibited phagocyte adhesion and migration, thus decreasing phagocyte infiltration at the site of infection and complement-dependent phagocytosis. Further findings indicated that TMEM268 interacts with CD11b and inhibits its degradation via the endosome–lysosome pathway. Our results reveal a positive regulatory role of TMEM268 in β2 integrin-associated anti-infectious immune responses and signify the potential value of targeting the TMEM268–CD11b signaling axis for the maintenance of immune homeostasis and immunotherapy for sepsis and related immune disorders.

The E3 ubiquitin ligase RING finger protein 115 (RNF115), also known as breast cancer-associated gene 2 (BCA2), has been linked with the growth of some cancers and immune regulation, which is negatively correlated with prognosis. Here, it is demonstrated that the RNF115 deletion can protect mice from acute liver injury (ALI) induced by the treatment of lipopolysaccharide (LPS)/D-galactosamine (D-GalN), as evidenced by decreased levels of alanine aminotransaminase, aspartate transaminase, inflammatory cytokines (e.g., tumor necrosis factor α and interleukin-6), chemokines (e.g., MCP1/CCL2) and inflammatory cell (e.g., monocytes and neutrophils) infiltration. Moreover, it was found that the autophagy activity in Rnf115^−/− livers was increased, which resulted in the removal of damaged mitochondria and hepatocyte apoptosis. However, the administration of adeno-associated virus Rnf115 or autophagy inhibitor 3-MA impaired autophagy and aggravated liver injury in Rnf115^−/− mice with ALI. Further experiments proved that RNF115 interacts with LC3B, downregulates LC3B protein levels and cell autophagy. Additionally, Rnf115 deletion inhibited M1 type macrophage activation via NF-κB and Jnk signaling pathways. Elimination of macrophages narrowed the difference in liver damage between Rnf115^+/+ and Rnf115^−/− mice, indicating that macrophages were linked in the ALI induced by LPS/D-GalN. Collectively, for the first time, we have proved that Rnf115 inactivation ameliorated LPS/D-GalN-induced ALI in mice by promoting autophagy and attenuating inflammatory responses. This study provides new evidence for the involvement of autophagy mechanisms in the protection against acute liver injury.

The E3 ubiquitin ligase RING finger protein 115 (RNF115), also known as breast cancer-associated gene 2 (BCA2), has been linked with the growth of some cancers and immune regulation, which is negatively correlated with prognosis. Here, it is demonstrated that the RNF115 deletion can protect mice from acute liver injury (ALI) induced by the treatment of lipopolysaccharide (LPS)/D-galactosamine (D-GalN), as evidenced by decreased levels of alanine aminotransaminase, aspartate transaminase, inflammatory cytokines (e.g., tumor necrosis factor α and interleukin-6), chemokines (e.g., MCP1/CCL2) and inflammatory cell (e.g., monocytes and neutrophils) infiltration. Moreover, it was found that the autophagy activity in Rnf115^−/− livers were increased, which resulting in the removal of damaged mitochondria and the hepatocyte apoptosis. However, the administration of adeno-associated virus Rnf115 or autophagy inhibitor 3-MA impaired autophagy and aggravated liver injury in Rnf115^−/− mice with ALI. Further experiments proved that RNF115 interacts with LC3B, negatively regulates LC3B protein homeostasis and cell autophagy. Additionally, Rnf115 deletion inhibited M1 type macrophage activation via NF-κB and Jnk signaling pathways. Elimination of macrophages narrowed the difference in liver damage between Rnf115^+/+ and Rnf115^−/− mice, indicating that macrophages were linked in the ALI induced by LPS/D-GalN. Collectively, for the first time, we have proved that Rnf115 inactivation ameliorated LPS/D-GalN-induced ALI in mice by promoting autophagy and attenuating inflammatory responses. This study provides new evidence for the involvement of autophagy mechanisms in the protection against acute liver injury.

E3 ubiquitin ligase Ring finger protein 115 (RNF115), also known as Breast cancer-associated gene 2 (BCA2) has been linked with the proliferation, migration, and invasion of breast cancer. Our study demonstrated that RNF115 is a negative regulator of autophagy in hepatoma cells. Inactivation ofRNF115can promote autophagosome formation, the fusion of autophagosomes with lysosomes, and the degradation of autophagic substrate. These effects may be related to the enhanced binding ability of RAB7 and HOPS complex and enhanced activity of ATG14 inRNF115-silenced cells. High levels of RNF115 were exhibited in most hepatic cancer tissues compared to that of the non-tumor liver tissues. Low levels of RNF115 were associated with significantly longer survival of patients with hepatocellular carcinoma. Furthermore,RNF115silencing inhibited cellular growth and migration, and reduced tumorigenicity in a hepatoma cell xenograft model. In a DEN-induced hepatocellular carcinoma model,Rnf115KO mice developed fewer and smaller liver tumors than the WT littermates, indicating that RNF115-mediated autophagy is negatively correlated with the occurrence and development of hepatocellular carcinoma. These findings provide an experimental foundation for the prevention and treatment of hepatocellular carcinoma by targeting RNF115.

ULK1 is crucial for initiating autophagosome formation and its activity is tightly regulated by post-translational modifications and protein-protein interactions. In the present study, we demonstrate that TMEM189 (Transmembrane protein 189), also known as plasmanylethanolamine desaturase 1 (PEDS1), negatively regulates the proteostasis of ULK1 and autophagy activity. In TMEM189-overexpressed cells, the formation of autophagesome is impaired, whileTMEM189knockdown increases cell autophagy. Further investigation reveals that TMEM189 interacts with and increases the instability of ULK1, as well as decreases its kinase activities. The TMEM189 N-terminal domain is required for the interaction with ULK1. Additionally, TMEM189 overexpression can disrupt the interaction between ULK1 and TRAF6, profoundly impairs K63-linked polyubiquitination of ULK1 and self-association, leading to the decrease of ULK1 stability. Moreover, in vitro and in vivo experiments suggest thatTMEM189deficiency results in the inhibition of tumorigenicity of gastric cancer. Our findings provide a new insight into the molecular regulation of autophagy and laboratory evidence for investigating the physiological and pathological roles of TMEM189.