Negative Regulatory Feedback Loop Research Articles

VvMYBA1 and VvMYB3 form an activator–repressor system to regulate anthocyanin biosynthesis in grape

Anthocyanins are important metabolites that provide a red or blue–purple hue to plants. The biosynthesis of these metabolites is mainly activated by the MYB-bHLH-WD40 (MBW) complex and repressed by a wide variety of proteins. Studies have shown that MYB activators activate MYB repressors to balance anthocyanin biosynthesis. However, there is a scarcity of studies investigating this mechanism in grapes. To explore the transcription factors involved in the regulation of anthocyanin biosynthesis, we reanalyzed the RNA-seq database for different developmental stages of ‘Muscat Hamburg’ berries, and the R2R3-MYB gene, annotated as VvMYB3, was screened. Our study revealed the anthocyanin content of the grape cultivar ‘Y73’ was higher than that of its parental cultivar MH, and the putative repressor VvMYB3 was found to be highly expressed in ‘Y73’ by qRT-PCR. The calli transgenic assays demonstrated that the repressive activity of VvMYB3 was conferred by the bHLH-binding motif, as well as by the C1 and C2 motifs. Yeast hybridization and chip-PCR assays revealed that VvMYB3 could repress anthocyanin biosynthesis by competing with VvMYBA1 to bind to VvMYC1 and promoting histone deacetylation of VvUFGT via the C2 motif. However, the expression of VvMYB3 was activated by VvMYBA1, which forms a negative feedback regulatory loop to modulate anthocyanin accumulation. In addition, we found a 408-bp repeat tandem sequence insertion in the VvMYBA1 promoter region of ‘Y73’ by sequencing. The GUS activity analysis showed that this sequence enhanced the expression of VvMYBA1 and led to an excessive accumulation of anthocyanins. Overall, our results provide insights into the anthocyanin activator–repressor system in grapes that prevents overaccumulation of anthocyanins.

Engineered targeting OIP5 sensitizes bladder cancer to chemotherapy resistance via TRIP12-PPP1CB-YBX1 axis.

Chemoresistance is an important cause of treatment failure in bladder cancer, and identifying genes that confer drug resistance is an important step toward developing new therapeutic strategies to improve treatment outcomes. In the present study, we show that gemcitabine plus cisplatin (GEM/DDP) therapy induces NF-κB signaling, which promotes p65-mediated transcriptional activation of OIP5. OIP5 recruits the E3 ubiquitin ligase TRIP12 to bind to and degrade the phosphatase PPP1CB, thereby enhancing the transcription factor activity of YBX1. This in turn upregulates drug-resistance-related genes under the transcriptional control of YBX1, leading to chemoresistance. Moreover, PPP1CB degradation can enhance the phosphorylation activity of IKKβ, triggering the NF-κB signaling cascade, which further stimulates OIP5 gene expression, thus forming a negative feedback regulatory loop. Consistently, elevated OIP5 expression was associated with chemoresistance and poor prognosis in patients with bladder cancer. Furthermore, we used a CRISPR/Cas9-based engineered gene circuit, which can monitor the progression of chemoresistance in real-time, to induce OIP5 knockout upon detection of increased NF-κB signaling. The gene circuit significantly inhibited tumor cell growth in vivo, underscoring the potential for synergy between gene therapy and chemotherapy in the treatment of cancer.

PD-1 controls differentiation, survival, and TCR affinity evolution of stem-like CD8+ T cells.

Stem-like progenitors are a critical subset of cytotoxic T cells that self-renew and give rise to expanded populations of effector cells critical for successful checkpoint blockade immunotherapy. Emerging evidence suggests that the tumor-draining lymph nodes can support the continuous generation of these stem-like cells that replenish the tumor sites and act as a critical source of expanded effector populations, underlining the importance of understanding what factors promote and maintain activated T cells in the stem-like state. Using advanced 3D multiplex immunofluorescence imaging, here we identified antigen-presentation niches in tumor-draining lymph nodes that support the expansion, maintenance, and affinity evolution of a unique population of TCF-1+PD-1+SLAMF6 hi stem-like CD8+ T cells. Our results show that contrary to the prevailing view that persistent TCR signaling drives terminal effector differentiation, prolonged antigen engagement well beyond the initial priming phase sustained the proliferation and self-renewal of these stem-like T cells in vivo . The inhibitory PD-1 pathway plays a central role in this process by mediating the fine-tuning of TCR and co-stimulatory signal input that enables selective expansion of high affinity TCR stem-like clones, enabling them to act as a renewable source of high affinity effector cells. PD-1 checkpoint blockade disrupts this fine tuning of input signaling, leading to terminal differentiation to the effector state or death of the most avid anti-tumor stem-like cells. Our results thus reveal an unexpected relationship between TCR ligand affinity recognition, a key negative feedback regulatory loop, and T cell stemness programming. Furthermore, these findings raise questions about whether anti-PD-1 checkpoint blockade during cancer immunotherapy provides a short-term anti-tumor effect that comes at the cost of diminishing efficacy due to progressive loss of these critical high affinity stem-like precursors.

Circ6834 suppresses non-small cell lung cancer progression by destabilizing ANHAK and regulating miR-873-5p/TXNIP axis

BackgroundCircular RNAs (circRNAs) play important roles in cancer progression and metastasis. However, the expression profiles and biological roles of circRNAs in non-small cell lung cancer (NSCLC) remain unclear.MethodsIn this study, we identified a novel circRNA, hsa_circ_0006834 (termed circ6834), in NSCLC by RNA-seq and investigated the biological role of circ6834 in NSCLC progression in vitro and in vivo. Finally, the molecular mechanism of circ6834 was revealed by tagged RNA affinity purification (TRAP), western blot, RNA immunoprecipitation, dual luciferase reporter gene assays and rescue experiments.ResultsOur results showed that circ6834 was downregulated in NSCLC tumor tissues and cell lines. Circ6834 overexpression inhibited NSCLC cell growth and metastasis both in vitro and in vivo, while circ6834 knockdown had the opposite effect. We found that TGF-β treatment decreased circ6834 expression, which was associated with the QKI reduction in NSCLC cells and circ6834 antagonized TGF-β-induced EMT and metastasis in NSCLC cells. Mechanistically, circ6834 bound to AHNAK protein, a key regulator of TGF-β/Smad signaling, and inhibited its stability by enhancing TRIM25-mediated ubiquitination and degradation. In addition, circ6834 acted as a miRNA sponge for miR-873-5p and upregulated TXNIP gene expression, which together inactivated the TGF-β/Smad signaling pathway in NSCLC cells.ConclusionIn conclusion, circ6834 is a tumor-suppressive circRNA that inhibits NSCLC progression by forming a negative regulatory feedback loop with the TGF-β/Smad signaling pathway and represents a novel therapeutic target for NSCLC.

A Negative Regulatory Feedback Loop within the JAK-STAT Pathway Mediated by the Protein Tyrosine Phosphatase DUSP14 in Shrimp.

The JAK-STAT pathway is a central communication node for various biological processes. Its activation is characterized by phosphorylation and nuclear translocation of the transcription factor STAT. The regulatory balance of JAK-STAT signaling is important for maintenance of immune homeostasis. Protein tyrosine phosphatases (PTPs) induce dephosphorylation of tyrosine residues in intracellular proteins and generally function as negative regulators in cell signaling. However, the roles of PTPs in JAK-STAT signaling, especially in invertebrates, remain largely unknown. Pacific white shrimp Penaeus vannamei is currently an important model for studying invertebrate immunity. This study identified a novel member of the dual-specificity phosphatase (DUSP) subclass of the PTP superfamily in P. vannamei, named PvDUSP14. By interacting with and dephosphorylating STAT, PvDUSP14 inhibits the excessive activation of the JAK-STAT pathway, and silencing of PvDUSP14 significantly enhances humoral and cellular immunity in shrimp. The promoter of PvDUSP14 contains a STAT-binding motif and can be directly activated by STAT, suggesting that PvDUSP14 is a regulatory target gene of the JAK-STAT pathway and mediates a negative feedback regulatory loop. This feedback loop plays a role in maintaining homeostasis of JAK-STAT signaling and is involved in antibacterial and antiviral immune responses in shrimp. Therefore, the current study revealed a novel inhibitory mechanism of JAK-STAT signaling, which is of significance for studying the regulatory mechanisms of immune homeostasis in invertebrates.

USP25 attenuates anti-GBM nephritis in mice by negative feedback regulation of Th17 cell differentiation

Purpose This study aimed to elucidate the role of USP25 in a mouse model of anti-glomerular basement membrane glomerulonephritis (anti-GBM GN). Methods USP25-deficient anti-GBM GN mice were generated, and their nephritis progression was monitored. Naïve CD4+ T cells were isolated from spleen lymphocytes and stimulated to differentiate into Th1, Th2, and Th17 cells. This approach was used to investigate the impact of USP25 on CD4+ T lymphocyte differentiation in vitro. Furthermore, changes in USP25 expression were monitored during Th17 differentiation, both in vivo and in vitro. Results USP25−/− mice with anti-GBM GN exhibited accelerated renal function deterioration, increased infiltration of Th1 and Th17 cells, and elevated RORγt transcription. In vitro experiments demonstrated that USP25−/− CD4+ T lymphocytes had a higher proportion for Th17 cell differentiation and exhibited higher RORγt levels upon stimulation. Wild-type mice with anti-GBM GN showed higher USP25 levels compared to healthy mice, and a positive correlation was observed between USP25 levels and Th17 cell counts. Similar trends were observed in vitro. Conclusion USP25 plays a crucial role in mitigating renal histopathological and functional damage during anti-GBM GN in mice. This protective effect is primarily attributed to USP25’s ability to inhibit the differentiation of naïve CD4+ T cells into Th17 cells. The underlying mechanism may involve the downregulation of RORγt. Additionally, during increased inflammatory responses or Th17 cell differentiation, USP25 expression is activated, forming a negative feedback regulatory loop that attenuates immune activation.

RND3 Potentiates Proinflammatory Activation through NOTCH Signaling in Activated Macrophages.

Macrophage activation is a complex process with multiple control elements that ensures an adequate response to the aggressor pathogens and, on the other hand, avoids an excess of inflammatory activity that could cause tissue damage. In this study, we have identified RND3, a small GTP-binding protein, as a new element in the complex signaling process that leads to macrophage activation. We show that RND3 expression is transiently induced in macrophages activated through Toll receptors and potentiated by IFN-γ. We also demonstrate that RND3 increases NOTCH signaling in macrophages by favoring NOTCH1 expression and its nuclear activity; however, Rnd3 expression seems to be inhibited by NOTCH signaling, setting up a negative regulatory feedback loop. Moreover, increased RND3 protein levels seem to potentiate NFκB and STAT1 transcriptional activity resulting in increased expression of proinflammatory genes, such as Tnf-α, Irf-1, or Cxcl-10. Altogether, our results indicate that RND3 seems to be a new regulatory element which could control the activation of macrophages, able to fine tune the inflammatory response through NOTCH.

Arabidopsis G-protein β subunit AGB1 represses abscisic acid signaling via attenuation of the MPK3-VIP1 phosphorylation cascade.

Heterotrimeric G proteins play key roles in cellular processes. Although phenotypic analyses of Arabidopsis Gβ (AGB1) mutants have implicated G proteins in abscisic acid (ABA) signaling, the AGB1-mediated modules involved in ABA responses remain unclear. We found that a partial AGB1 protein was localized to the nucleus where it interacted with ABA-activated VirE2-interacting protein 1 (VIP1) and mitogen-activated protein kinase 3 (MPK3). AGB1 acts as an upstream negative regulator of VIP1 activity by initiating responses to ABA and drought stress, and VIP1 regulates the ABA signaling pathway in an MPK3-dependent manner in Arabidopsis. AGB1 outcompeted VIP1 for interaction with the C-terminus of MPK3, and prevented phosphorylation of VIP1 by MPK3. Importantly, ABA treatment reduced AGB1 expression in the wild type, but increased in vip1 and mpk3 mutants. VIP1 associates with ABA response elements present in the AGB1 promoter, forming a negative feedback regulatory loop. Thus, our study defines a new mechanism for fine-tuning ABA signaling through the interplay between AGB1 and MPK3-VIP1. Furthermore, it suggests a common G protein mechanism to receive and transduce signals from the external environment.

RsaL-driven negative regulation promotes heterogeneity in Pseudomonas aeruginosa quorum sensing.

Single-cell analyses can reveal that despite experiencing identical physico-chemical conditions, individual bacterial cells within a monoclonal population may exhibit variations in gene expression. Such phenotypic heterogeneity has been described for several aspects of bacterial physiology, including QS activation. This study demonstrates that the transition of non-quorate cells to the quorate state is a graded process that does not occur at a specific cell density and that subpopulations of non-quorate cells also persist at high cell density. Here, we provide a mechanistic explanation for this phenomenon, showing that a negative feedback regulatory loop integrated into the las system has a pivotal role in promoting cell-to-cell variation in the QS activation state and in limiting the transition of non-quorate cells to the quorate state in P. aeruginosa.

Human cytomegalovirus attenuates AKT activity by destabilizing insulin receptor substrate proteins.

Human cytomegalovirus (HCMV) requires inactivation of AKT to efficiently replicate, yet how AKT is shut off during HCMV infection has remained unclear. We show that UL38, an HCMV protein that activates mTORC1, is necessary and sufficient to destabilize insulin receptor substrate 1 (IRS1), a model insulin receptor substrate (IRS) protein. Degradation of IRS proteins in settings of excessive mTORC1 activity is an important mechanism for insulin resistance. When IRS proteins are destabilized, PI3K cannot be recruited to growth factor receptor complexes, and hence, AKT membrane recruitment, a rate limiting step in its activation, fails to occur. Despite its penchant for remodeling host cell signaling pathways, our results reveal that HCMV relies upon a cell-intrinsic negative regulatory feedback loop to inactivate AKT. Given that pharmacological inhibition of PI3K/AKT potently induces HCMV reactivation from latency, our findings also imply that the expression of UL38 activity must be tightly regulated within latently infected cells to avoid spontaneous reactivation.

The MYB59 transcription factor negatively regulates salicylic acid- and jasmonic acid-mediated leaf senescence.

Leaf senescence is the final stage of leaf development and is affected by various exogenous and endogenous factors. Transcriptional regulation is essential for leaf senescence, however, the underlying molecular mechanisms remain largely unclear. In this study, we report that the transcription factor MYB59, which was predominantly expressed in early senescent rosette leaves, negatively regulates leaf senescence in Arabidopsis (Arabidopsis thaliana). RNA sequencing revealed a large number of differentially expressed genes involved in several senescence-related biological processes in myb59-1 rosette leaves. Chromatin immunoprecipitation and transient dual-luciferase reporter assays demonstrated that MYB59 directly repressed the expression of SENESCENCE ASSOCIATED GENE 18 and indirectly inhibited the expression of several other senescence-associated genes to delay leaf senescence. Moreover, MYB59 was induced by salicylic acid (SA) and jasmonic acid (JA). MYB59 inhibited SA production by directly repressing the expression of ISOCHORISMATE SYNTHASE 1 and PHENYLALANINE AMMONIA-LYASE 2 and restrained JA biosynthesis by directly suppressing the expression of LIPOXYGENASE 2, thus forming two negative feedback regulatory loops with SA and JA and ultimately delaying leaf senescence. These results help us understand the novel function of MYB59 and provide insights into the regulatory network controlling leaf senescence in Arabidopsis.

Robust Weak Detectability Analysis of Boolean Networks Subject to Function Perturbation

As a class of state estimation issues, detectability is widely used in fault diagnosis, circuit design, and disease status detection. This brief analyzes the robust weak detectability of Boolean networks (BNs) under function perturbation. A simplified parallel system is constructed for BNs. Based on the transition of state pairs in the simplified parallel system, a new criterion is proposed for the weak detectability of BNs. Using the reachability from perturbed state pairs to attractors in indistinguishable pairs, the robust weak detectability of BNs subject to function perturbation is analyzed. A practical example of p53-MDM2 negative feedback regulatory loop is used to illustrate the obtained criteria.

Interactive regulation of DNA demethylase gene TET1 and m6A methyltransferase gene METTL3 in myoblast differentiation

DNA methylation (5mC) and mRNA N6-methyladenosine (m6A) play an essential role in gene transcriptional regulation. DNA methylation has been well established to be involved in skeletal muscle development. Interacting regulatory mechanisms between DNA methylation and mRNA m6A modification have been identified in a variety of biological processes. However, the effect of m6A on skeletal muscle differentiation and the underlying mechanisms are still unclear. It is also unknown whether there is an interaction between DNA methylation and mRNA m6A modification in skeletal myogenesis. In the present study, we used m6A-IP-qPCR, LC–MS/MS and dot blot assays to determine that the DNA demethylase gene, TET1, exhibited increased m6A levels and decreased mRNA expression during bovine skeletal myoblast differentiation. Dual-luciferase reporter assays and RIP experiments demonstrated that METTL3 suppressed TET1 expression by regulating TET1 mRNA stability in a m6A-YTHDF2-dependent manner. Furthermore, TET1 mediated DNA demethylation of itself, MYOD1 and MYOG, thereby stimulating their expression to promote myogenic differentiation. Ectopic expression of TET1 rescued the effect of METTL3 knockdown on reduced myotubes. In contrast, TET1 knockdown impaired the myogenic differentiation promoted by METTL3 overexpression. Moreover, ChIP experiments found that TET1 could bind and demethylate METTL3 DNA, which enhanced METTL3 expression. In addition, TET1 knockdown decreased m6A levels. ChIP assays also showed that TET1 knockdown contributed to the binding of H3K4me3 and H3K27me3 to METTL3 DNA. Our results revealed a negative feedback regulatory loop between TET1 and METTL3 in myoblast differentiation, which unveiled the interplay among DNA methylation, RNA methylation and histone methylation in skeletal myogenesis.

HBP1 inhibits the development of type 2 diabetes mellitus through transcriptional activation of the IGFBP1 gene.

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease that is highly prevalent worldwide and characterized by glucose and lipid metabolism disorders. However, the pathogenic mechanisms have not been fully established. Here, we found that HMG-box transcription factor 1 (HBP1) is involved in T2DM and that its deficiency in mice aggravates the features of diabetes. In addition, we undertook screening by RNA sequencing and found that HBP1 activates the transcription of the insulin-like growth factor binding protein 1 (IGFBP1) gene. Moreover, Insulin and palmitic acid reduced HBP1 protein expression and inhibited its binding to the IGFBP1 promoter. Furthermore, HBP1 reduced the serum free insulin-like growth factor 1 (IGF-1) concentration through IGFBP1 and inhibited the PI3K/AKT signaling pathway. This forms an insulin/HBP1/IGFBP1 negative feedback regulatory loop to dynamically regulate blood glucose and insulin concentrations. These findings have elucidated a mechanism whereby HBP1 and its negative feedback regulatory loop influence the development of T2DM, thereby providing a new theoretical basis and potential therapeutic target for T2DM.

Improving AOX1 promoter efficiency by overexpression of Mit1 transcription factor.

Reprogramming in transcriptional regulation provides an effective tool for adjusting cellular metabolic activities. The strong methanol-inducible alcohol oxidase-1 promoter (pAOX1) is commonly used for heterologous gene expression in the yeast Pichia pastoris. Here, we present a novel Pichia pastoris strain engineered to co-express methanol-induced transcription factor 1 (Mit1) and the target protein. Mit1 upregulates pAOX1 in response to methanol. Two model proteins (VEGF and eGFP) have been used as the target proteins under the control of pAOX1. The sequence of Mit1 had obtained from the yeast genome and likewise cloned under the control of pAOX1. The results indicated a 1.9 and 2.2 fold increase in the detected VEGF and eGFP, respectively, when co-expressed with Mit1. Furthermore, the double-recombinant cells, containing Mit-1 and eGFP, produced 1.3 fold more eGFP when the methanol feeding concentration was doubled. The real-time PCR indicated a slight increase in the Mit1 expression, probably due to the negative regulatory feedback loop that exists for the intrinsic yeast Mit1. Overexpression of Mit1 also led to duplication of AOX1 enzyme activity, which may enhance the yeast cells' capacity for methanol detoxification. Overexpression of Mit1 could be considered a promising strategy for upregulation of target recombinant proteins in Pichia pastoris. Intracellular overexpression of Mit1 upregulates the heterologous target gene (eGFP) production, which is expressed under the control of pAOX1.

OsDOF11 Promotes Crown Root Formation via Cytokinin in Oryza Sativa.

Crown root is the main part of root system, which performs an important role in rice growth and development, especially in nutrition and water assimilation. Previously, we reported negative feedback regulation loop between Oryza sativa DNA BINDING WITH ONE FINGER 11 (OsDOF11) and cytokinin by Oryza sativa CYTOKININ OXIDASE/DEHYDROGENASE 4 (OsCKX4) in rice development. Reverse transcription quantitative RT-PCR analyses was used to analyze the related gene transcript level. Nitrogen and hormone were measured by CHN-Nitrogen analyser and Liquid chromatography mass spectrometer, respectively. Exogenous application of cytokinin and [13C] sucrose labeled stable isotope uptake experiments help us to explain the relationship between OsDOF11 and cytokinin. We demonstrate the role of OsDOF11 in root development. We note that the loss function of OsDOF11 displays the reduced crown roots number, low activity of nitrogen assimilation and low content of cytokinin and auxin. The expression level of WUSCHEL-related homeobox (OsWOX11), A-type response regulator 2 (OsRR2), OsRR3, and OsCKX4 were decreased in osdof11-1, as well as in OsDOF11 RNA interference 9 mutants (RNAi-9 lines). Through Exogenous application of multiple concentrations of cytokinin as treatment to osdof11-1 mutant, RNAi-9 lines, and wild type (WT). We found that the crown roots number of osdof11-1 plants were rescued as the cytokinin concentration increased gradually from 1 μM to 10 μM, but the effect was weaker in RNAi-9 line. And cytokinin inhibited sucrose uptake activity from Murashige-Skoog medium with 3.0% sucrose (MS30) by OsDOF11 in rice root. OsDOF11 promotes crown root formation via cytokinin in oryza sativa. These results provide a physiological basis for further analysis of the OsDOF11 function of in rice root development.

MiR-218-5p Induces Interleukin-1β and Endovascular Trophoblast Differentiation by Targeting the Transforming Growth Factor β-SMAD2 Pathway.

The acquisition of an endovascular trophoblast (enEVT) phenotype is essential for normal placental development and healthy pregnancy. MicroRNAs (miRNAs) are small noncoding RNAs that play critical roles in regulating gene expression. We have recently reported that miR-218-5p promotes enEVT differentiation and spiral artery remodeling in part by targeting transforming growth factor β2 (TGFβ2). We also identified IL1B, which encodes interleukin 1β (IL1β), as one of the most highly upregulated genes by miR-218-5p. In this study, we investigated how miR-218-5p regulates IL1B expression and IL1β secretion and the potential role of IL1β in enEVT differentiation. Using two cell lines derived from extravillous trophoblasts (EVTs), HTR-8/SVneo and Swan 71, we found that stable overexpression of miR-218-5p precursor, mir-218-1, or transient transfection of miR-218-5p mimic, significantly increased IL1B mRNA and IL1β protein levels in cells and conditioned media. We also showed that miR-218-5p directly interacted with SMAD2 3’UTR and reduced SMAD2 at mRNA and protein levels. Knockdown of SMAD2 induced IL1B expression and attenuated the inhibitory effect of TGFβ2 on IL1B expression. On the other hand, overexpression of SMAD2 reduced IL1β levels and blocked the stimulatory effects of miR-218-5p on IL1B expression, trophoblast migration and endothelial-like network formation. In addition, treatment of trophoblasts with IL1β induced the formation of endothelial-like networks and the expression of enEVT markers in a dose-dependent manner. These results suggest that miR-218-5p inhibits the TGFβ/SMAD2 pathway to induce IL1β and enEVT differentiation. Finally, low doses of IL1β also inhibited the expression of miR-218-5p, suggesting the existence of a negative feedback regulatory loop. Taken together, our findings suggest a novel interactive miR-218-5p/TGFβ/SMAD2/IL1β signaling nexus that regulates enEVT differentiation.

The NAC transcription factor ATAF2 promotes ethylene biosynthesis and response in Arabidopsis thaliana seedlings.

Arabidopsis thaliana activating factor 2 (ATAF2) plays extensive regulatory roles in pathogenesis, seedling development, and stress responses. Here, we performed transcriptome analysis on ATAF2 loss- and gain-of-function mutants to identify differentially expressed genes (DEGs). Gene ontology analyses on DEGs reveal that ATAF2 enhances seedling responses to multiple hormone and stress signals. In particular, our transcriptome analysis suggests that ATAF2 promotes ethylene biosynthesis and responses via activating relevant genes. This novel role of ATAF2 was further demonstrated by using multiple ATAF2-null and overexpression lines for reverse transcription quantitative PCR verification, ethylene production measurements, and assays of seedlings growth responses to the ethylene immediate biosynthetic precursor 1-aminocyclopropane-1-carboxylic acid (ACC). ACC suppresses ATAF2 expression to form a negative feedback regulation loop.

STING orchestrates the crosstalk between polyunsaturated fatty acid metabolism and inflammatory responses

SummaryConcerted alteration of immune and metabolic homeostasis underlies several inflammation-related pathologies, ranging from metabolic syndrome to infectious diseases. Here, we explored the coordination of nucleic acid-dependent inflammatory responses and metabolic homeostasis. We reveal that the STING (stimulator of interferon genes) protein regulates metabolic homeostasis through inhibition of the fatty acid desaturase 2 (FADS2) rate-limiting enzyme in polyunsaturated fatty acid (PUFA) desaturation. STING ablation and agonist-mediated degradation increased FADS2-associated desaturase activity and led to accumulation of PUFA derivatives that drive thermogenesis. STING agonists directly activated FADS2-dependent desaturation, promoting metabolic alterations. PUFAs in turn inhibited STING, thereby regulating antiviral responses and contributing to resolving STING-associated inflammation. Thus, we have unveiled a negative regulatory feedback loop between STING and FADS2 that fine-tunes inflammatory responses. Our results highlight the role of metabolic alterations in human pathologies associated with aberrant STING activation and STING-targeting therapies.

LILRB3 supports acute myeloid leukemia development and regulates T-cell antitumor immune responses through the TRAF2-cFLIP-NF-κB signaling axis.

Leukocyte immunoglobulin-like receptor B (LILRB), a family of immune checkpoint receptors, contribute to acute myeloid leukemia (AML) development, but the specific mechanisms triggered by activation or inhibition of these immune checkpoints in cancer is largely unknown. Here we demonstrated that the intracellular domain of LILRB3 is constitutively associated with the adaptor protein TRAF2. Activated LILRB3 in AML cells leads to recruitment of cFLIP and subsequent NF-κB upregulation, resulting in enhanced leukemic cell survival and inhibition of T cell-mediated anti-tumor activity. Hyperactivation of NF-κB induces a negative regulatory feedback loop mediated by A20, which disrupts the interaction of LILRB3 and TRAF2; consequently the SHP-1/2-mediated inhibitory activity of LILRB3 becomes dominant. Finally, we show that blockade of LILRB3 signaling with antagonizing antibodies hampers AML progression. LILRB3 thus exerts context-dependent activating and inhibitory functions, and targeting LILRB3 may become a potential therapeutic strategy for AML treatment.