RELL1 inhibits autophagy pathway and regulates Mycobacterium tuberculosis survival in macrophages

Sparassis latifolia polysaccharide alleviated lipid metabolism abnormalities in kidney of lead-exposed mice by regulating oxidative stress-mediated inflammation and autophagy based on multi-omics

Lead is a common environmental pollutant which can accumulate in the kidney and cause renal injury. However, regulatory effects and mechanisms of Sparassis latifolia polysaccharide (SLP) on lipid metabolism abnormality in kidney exposed to lead are not clarified. In this study, mice were used to construct an animal model to observe the histopathological changes in kidney, measure lead content, damage indicators, differentially expressed metabolites (DEMs) and genes (DEGs) in key signaling pathways that cause lipid metabolism abnormalities based on lipidomics and transcriptomics, which were later validated using qPCR and western blotting. Co-treatment of Pb and N-acetylcysteine (NAC) were used to verify the link between SLP and oxidative stress. Our results indicated that treatment with SLP identified 276 DEMs (including metabolism of glycerophospholipid, sphingolipid, glycerolipid and fatty acid) and 177 DEGs (including genes related to oxidative stress, inflammation, autophagy and lipid metabolism). Notably, regulatory effects of SLP on abnormal lipid metabolism in kidney were mainly associated with oxidative stress, inflammation and autophagy; SLP could regulate abnormal lipid metabolism in kidney by reducing oxidative stress and affecting its downstream-regulated autophagy and inflammatory to alleviate renal injury caused by lead exposure. This study provides a theoretical basis for SLP intervention in lead injury.

Functional Analysis of Genes in Mycobacterium tuberculosis Action Against Autophagosome-Lysosome Fusion

Tuberculosis is a lethal disease that is one of the world's top ten death-associated infections in humans; Mycobacterium tuberculosis causes tuberculosis, and this bacterium is linked to the lysis of autophagolysosomal fusion action, a self-defense mechanism of its own. Thus, Cytoplasmic bacilli are sequestered by autophagy and transported to lysosomes to be inactivated to destroy intracellular bacteria. Besides this, a macrophage can limit intracellular Mycobacterium by using a type of autophagy, selective autophagy, a cell that marks undesirable ubiquitin existence in cytosolic cargo, acting as a "eat me" sensor in conjunction with cellular homeostasis. Mycobacterium tuberculosis genes of the PE_PGRS protein family inhibit autophagy, increase mycobacterial survival, and lead to latent tuberculosis infection associated with miRNAs. In addition, the family of autophagy-regulated (ATG) gene members are involved in autophagy and controls the initiation, expansion, maturation, and fusion of autophagosomes with lysosomes, among other signaling events that control autophagy flux and reduce inflammatory responses and forward to promote cellular proliferation. In line with the formation of caseous necrosis in macrophages by Mycobacterium tuberculosis and their action on the lysis of autophagosome fusion, it leads to latent tuberculosis infection. Therefore, we aimed to comprehensively analyses the autophagy and self-defense mechanism of Mycobacterium tuberculosis, which is to be gratified future research on novel therapeutic tools and diagnostic markers against tuberculosis.

The Dual Roles of Activating Transcription Factor 3 (ATF3) in Inflammation, Apoptosis, Ferroptosis, and Pathogen Infection Responses

Transcription factors are pivotal regulators in the cellular life process. Activating transcription factor 3 (ATF3), a member of the ATF/CREB (cAMP response element-binding protein) family, plays a crucial role as cells respond to various stresses and damage. As a transcription factor, ATF3 significantly influences signal transduction regulation, orchestrating a variety of signaling pathways, including apoptosis, ferroptosis, and cellular differentiation. In addition, ATF3 serves as an essential link between inflammation, oxidative stress, and immune responses. This review summarizes the recent advances in research on ATF3 activation and its role in regulating inflammatory responses, cell apoptosis, and ferroptosis while exploring the dual functions of ATF3 in these processes. Additionally, this article discusses the role of ATF3 in diseases related to pathogenic microbial infections. Our review may be helpful to better understand the role of ATF3 in cellular responses and disease progression, thus promoting advancements in clinical treatments for inflammation and oxidative stress-related diseases.

Mycobacterium tuberculosis PE_PGRS45 (Rv2615c) Promotes Recombinant Mycobacteria Intracellular Survival via Regulation of Innate Immunity, and Inhibition of Cell Apoptosis

Tuberculosis (TB), a bacterial infectious disease caused by Mycobacterium tuberculosis (M. tuberculosis), is a significant global public health problem. Mycobacterium tuberculosis expresses a unique family of PE_PGRS proteins that have been implicated in pathogenesis. Despite numerous studies, the functions of most PE_PGRS proteins in the pathogenesis of mycobacterium infections remain unclear. PE_PGRS45 (Rv2615c) is only found in pathogenic mycobacteria. In this study, we successfully constructed a recombinant Mycobacterium smegmatis (M. smegmatis) strain which heterologously expresses the PE_PGRS45 protein. We found that overexpression of this cell wall-associated protein enhanced bacterial viability under stress in vitro and cell survival in macrophages. MS_PE_PGRS45 decreased the secretion of pro-inflammatory cytokines such as IL-1β, IL-6, IL-12p40, and TNF-α. We also found that MS_PE_PGRS45 increased the expression of the anti-inflammatory cytokine IL-10 and altered macrophage-mediated immune responses. Furthermore, PE_PGRS45 enhanced the survival rate of M. smegmatis in macrophages by inhibiting cell apoptosis. Collectively, our findings show that PE_PGRS45 is a virulent factor actively involved in the interaction with the host macrophage.

The RELT Family of Proteins: An Increasing Awareness of Their Importance for Cancer, the Immune System, and Development

This review highlights Receptor Expressed in Lymphoid Tissues (RELT), a Tumor Necrosis Factor Superfamily member, and its two paralogs, RELL1 and RELL2. Collectively, these three proteins are referred to as RELTfms and have gained much interest in recent years due to their association with cancer and other human diseases. A thorough knowledge of their physiological functions, including the ligand for RELT, is lacking, yet emerging evidence implicates RELTfms in a variety of processes including cytokine signaling and pathways that either promote cell death or survival. T cells from mice lacking RELT exhibit increased responses against tumors and increased inflammatory cytokine production, and multiple lines of evidence indicate that RELT may promote an immunosuppressive environment for tumors. The relationship of individual RELTfms in different cancers is not universal however, as evidence indicates that individual RELTfms may be risk factors in certain cancers yet appear to be protective in other cancers. RELTfms are important for a variety of additional processes related to human health including microbial pathogenesis, inflammation, behavior, reproduction, and development. All three proteins have been strongly conserved in all vertebrates, and this review aims to provide a clearer understanding of the current knowledge regarding these interesting proteins.

Mycobacterium tuberculosis-macrophage interaction: Molecular updates

Mycobacterium tuberculosis (Mtb), the causative agent of Tuberculosis (TB), remains a pathogen of great interest on a global scale. This airborne pathogen affects the lungs, where it interacts with macrophages. Acidic pH, oxidative and nitrosative stressors, and food restrictions make the macrophage's internal milieu unfriendly to foreign bodies. Mtb subverts the host immune system and causes infection due to its genetic arsenal and secreted effector proteins. In vivo and in vitro research have examined Mtb-host macrophage interaction. This interaction is a crucial stage in Mtb infection because lung macrophages are the first immune cells Mtb encounters in the host. This review summarizes Mtb effectors that interact with macrophages. It also examines how macrophages control and eliminate Mtb and how Mtb manipulates macrophage defense mechanisms for its own survival. Understanding these mechanisms is crucial for TB prevention, diagnosis, and treatment.

Epigenetic reader BRD4 supports mycobacterial pathogenesis by co-modulating host lipophagy and angiogenesis

Mycobacterium tuberculosis (Mtb)-driven lipid accumulation is intricately associated with the progression of tuberculosis (TB) disease. Although several studies elucidating the mechanisms for lipid droplet (LD) biosynthesis exist, we provide evidence for the significance of their regulated turnover via macroautophagy/autophagy during Mtb infection. We demonstrate that Mtb utilizes EGFR (epidermal growth factor receptor) signaling to induce the expression of the histone acetylation reader, BRD4 (bromodomain containing 4). The EGFR-BRD4 axis suppresses lipid-specific autophagy, and hence favors cellular lipid accumulation. Specifically, we found that pharmacological inhibition or knockdown of Egfr or Brd4 enhances autophagic flux and concomitantly decreases cellular LDs that is otherwise maintained at a significant level in chloroquine-treated or Atg5 knocked down autophagy-compromised host cells. In line with the enhanced lipophagy, we found that loss of EGFR or BRD4 function restricts mycobacterial burden that is rescued by external replenishment with oleic acid. We also report that the EGFR-BRD4 axis exerts additional effects by modulating pro-angiogenic gene expression and consequently aberrant angiogenesis during mycobacterial infection. This is important in the context of systemic Mtb dissemination as well as for the efficient delivery of anti-mycobacterial therapeutics to the Mtb-rich core of TB granuloma. Finally, utilizing an in vivo mouse model of TB, we show that pharmacological inhibition of EGFR and BRD4 compromises LD buildup via enhanced lipophagy and normalizes angiogenesis, thereby restricting Mtb burden and rescuing mice from severe TB-like pathology. These findings shed light on the novel roles of BRD4 during Mtb infection, and its possible implication in potentiating anti-TB responses.Abbreviations: ATG5: autophagy related 5; BRDs: bromodomain containing; COL18A1: collagen type XVIII alpha 1 chain; EGFR: epidermal growth factor receptor; EP300: E1A binding protein p300; KDR: kinase insert domain receptor; KLF5: Kruppel like factor 5; LDs: lipid droplets; MAP1LC3B: microtubule associated protein 1 light chain 3 beta; Mtb: Mycobacterium tuberculosis; PECAM1: platelet and endothelial cell adhesion molecule 1; SQSTM1/p62: sequestosome 1; TB: tuberculosis; THBS1: thrombospondin 1; VEGF: vascular endothelial growth factor.

RELT stains prominently in B-cell lymphomas and binds the hematopoietic transcription factor MDFIC

Receptor Expressed in Lymphoid Tissues (RELT) is a human tumor necrosis factor receptor superfamily member (TNFRSF) that is expressed most prominently in cells and tissues of the hematopoietic system. RELL1 and RELL2 are two homologs that physically interact with RELT and co-localize with RELT at the plasma membrane. This study sought to further elucidate the function of RELT by identifying novel protein interactions with RELT family members. The transcription factor MyoD family inhibitor domain-containing (MDFIC) was identified in a yeast two-hybrid genetic screen using RELL1 as bait. MDFIC co-localizes with RELT family members at the plasma membrane; this co-localization was most prominently observed with RELL1 and RELL2. In vitro co-immunoprecipitation (Co-IP) was utilized to demonstrate that MDFIC physically interacts with RELT, RELL1, and RELL2. Co-IP using deletion mutants of MDFIC and RELT identified regions important for physical association between MDFIC and RELT family members and a computational analysis revealed that RELT family members are highly disordered proteins. Immunohistochemistry of normal human lymph nodes revealed RELT staining that was most prominent in macrophages. Interestingly, the level of RELT staining significantly increased progressively in low and high-grade B-cell lymphomas versus normal lymph nodes. RELT co-staining with CD20 was observed in B-cell lymphomas, indicating that RELT is expressed in malignant B cells. Collectively, these results further our understanding of RELT-associated signaling pathways, the protein structure of RELT family members, and provide preliminary evidence indicating an association of RELT with B-cell lymphomas.