Search Results (273)

Alpha-1 antitrypsin (AAT) is a serine protease inhibitor with potent anti-inflammatory and immunomodulatory properties, but its role in cancer is context-dependent across tumor types. We integrated transcriptomic analyses of human melanoma cohorts, in vivo studies using AAT-transgenic (hAAT-TG) mice, and in vitro assays in murine and human melanoma cells to define the biological functions of AAT in melanoma. SERPINA1 expression increased progressively from normal skin to nevi and metastatic melanoma, yet higher intratumoral levels correlated with improved overall survival in metastatic disease. In hAAT-TG mice, melanoma growth was markedly inhibited compared with wild-type controls, and the inhibitory effect required CD8⁺ T cells and was enhanced by CD4⁺ T-cell depletion, demonstrating that AAT promotes cytotoxic T-cell activity while attenuating regulatory T-cell suppression. Histologic analysis showed heavily pigmented tumors in hAAT-TG mice. In vitro, hAAT upregulated melanocytic differentiation markers (MITF, TYR, PMEL, MART-1) and increased melanin production in murine and human melanoma lines, suggesting enhanced tumor immunogenicity. In conclusion, hAAT exerts antitumor effects in melanoma indirectly by reprogramming the tumor microenvironment toward differentiation and immune activation. These findings highlight a previously unrecognized role for AAT as a dual immunoregulatory and differentiation-promoting factor and support AAT as a potential immunoregulatory adjuvant in melanoma. Full article

Background/Objectives: Radiolabeled fibroblast activation protein inhibitors (FAPIs) are emerging as promising imaging agents assessing fibrotic diseases. This study evaluates [⁶⁸Ga]Ga-DATA^5m.SA.FAPi for imaging pulmonary fibrosis in two mouse models, bleomycin-induced (BLM) and a transgenic (fra-2^tg) model, both displaying characteristics of human pulmonary fibrotic diseases. Methods: In the BLM model, C57BL/6 mice were treated with bleomycin or isotonic sodium chloride (controls) for 4, 5, and 6 weeks, followed by [⁶⁸Ga]Ga-DATA^5m.SA.FAPi PET/CT scans. Fra-2^tg mice and wildtype (WT) littermates underwent at 7, 11, and 18/19 weeks of age a PET/CT scan. The selected timepoints correspond to early, middle, and late disease stages for each model. Imaging was complemented by ex vivo quantification, histological, and immunohistochemical (IHC) analyses. Results: In BLM mice, pulmonary [⁶⁸Ga]Ga-DATA^5m.SA.FAPi uptake showed a trend toward increase as early as 5 weeks of treatment compared with the controls, which was confirmed by ex vivo analysis (BLM: 3.31 ± 0.29%ID/g, n = 5; control: 1.61 ± 0.29%ID/g, n = 4; p = 0.0035). In fra-2^tg mice, no significant differences could be detected. IHC revealed elevated pulmonary FAP expression specifically at early (BLM) and mild (fra-2^tg) disease stages, whereas for BLM, tracer uptake was more pronounced at later stages. Conclusions: Our findings complement and extend observations from previous studies and support the potential of FAPI tracers as molecular imaging agents for pulmonary fibrosis. Full article

Colorectal cancer (CRC) incidence is a significant cancer globally, and radiotherapy resistance is a serious problem. Cucurbitacin D (CBD), extracted from many plants such as the tubers of Trichosanthes kirilowii and the fruits of Ecballium elaterium (squirting cucumber), has various therapeutic effects, such as anti-cancer, -inflammation, -diabetes, and -viral infection effects. Since reports have indicated that CBD exhibits effective anti-cancer activity across various cancer types, our hypothesis is that CBD will overcome radioresistance in CRC radiotherapy. In the present study, we identified that CBD, a triterpenoid compound isolated from Trichosanthes kirilowii and Ecballium elaterium, has an anti-cancer and anti-inflammatory effect in vivo and in vitro. In LPS-induced murine models, CBD suppresses LPS-mediated cytokines, including TNFα, IL-6, IL-1β, and COX-2. In CRC xenograft mouse models, CBD treatment results in significantly smaller tumor volumes than the control. In HCT116 and HT29 cells, CBD treatment suppresses cell viability and increases LDH cytotoxicity and caspase-3 activity and cleavage. However, combined treatment of CBD and Z-VAD-FMK inhibits caspase-dependent apoptosis and cell death. Since CBD induces intracellular calcium (Ca²⁺) and reactive oxygen species (ROS) generation, it mediates ER stress-induced apoptotic cell death through the PERK-ATF4-CHOP axis. Moreover, ER stress inducer thapsigargin (TG) mediates synergistic apoptotic cell death in CBD-treated HCT116 and HT29 cells. However, PERK or CHOP knockdown suppresses ER stress-mediated apoptosis in CBD-treated HCT116 and HT29 cells. CBD treatment induces oxidative stress through the NADPH Oxidase 4 (NOX4) and also increases ROS generation. However, NOX4 knockdown and ROS inhibitor NAC or DPI block ER stress-induced apoptotic cell death by inhibiting the suppression of cell viability and the elevation of caspase-3 activity, LDH cytotoxicity, and intracellular ROS activity in CBD-mediated HCT116 and HT29 cells. We established radioresistant CRC models (HCT116R and HT29R); subsequently, radiation (2 Gy) in combination with CBD treatment overcame radioresistance via the modulation of the epithelial–mesenchymal transition (EMT) phenomenon, including the increase in N-cadherin and vimentin and the reduction in E-cadherin. Thus, these results show that CBD may be a new powerful therapeutic approach for CRC radiotherapy. Full article

Cordycepin (3′-deoxyadenosine, 3′-dA), the flagship nucleoside antibiotic from Cordyceps militaris, exerts potent anti-inflammatory, antimicrobial, and antitumor activity but is rapidly inactivated by human adenosine deaminase (ADA). While prodrugs, ADA inhibitors, and nanocarriers have been pursued to prolong its half-life, the influence of solid form on delivery performance remains unexplored. Here, three polymorphs—anhydrate-I (flake-like), anhydrate-II (rod-like), and a previously unreported monohydrate (fibrillar)—were prepared, characterized (PXRD, TG-DSC, FTIR), and subjected to equilibrium solubility, slurry-conversion, and humidity-sorption mapping. The monohydrate dehydrates at 144 °C and sequentially transforms to anhydrate-I → anhydrate-II (ΔH = −127.5 J g⁻¹), establishing a monotropic relationship between the two anhydrous forms. Solubility displays a bell-shaped profile versus water activity: the monohydrate is stable above aw 0.8, whereas anhydrate-II predominates below aw 0.2. In model immediate-release tablets, anhydrate-II achieves complete dissolution within 10 min, whereas the monohydrate sustains release for 30 min. Hygroscopicity tests show the monohydrate absorbs <6% water up to 75% RH without structural change, whereas anhydrate-I converts to the monohydrate above 63% RH. The quantitative humidity–crystal form–performance correlations provide a rational platform for crystal form selection and the design of stable, efficacious cordycepin solid dosage forms. Full article

Toxin–antitoxin (TA) modules represent sophisticated regulatory networks that have evolved from simple plasmid maintenance factors into multifunctional genetic modules orchestrating bacterial stress responses, pathogenesis, and ecological adaptation. This review highlights a compelling correlation between the abundance of toxin–antitoxin (TA) modules and bacterial pathogenicity, as exemplified by Mycobacterium tuberculosis (M.tb), which encodes 118 TA loci—significantly more than the fewer than 10 found in closely related saprophytic species. The clinical significance of TA modules extends beyond traditional stress response roles to encompass antimicrobial persistence, where systems like VapBC and MazEF facilitate dormant subpopulations that survive antibiotic therapy while maintaining chronic infections. Recent discoveries have revealed TA modules as sophisticated bacterial defense mechanisms against bacteriophage infection, with DarTG and ToxIN systems representing novel antiviral immunity components that complement CRISPR-Cas and restriction–modification systems. The immunomodulatory capacity of TA modules demonstrates their role in host–pathogen interactions, where systems such as VapC12 in M.tb promote macrophage polarization toward permissive M2 phenotypes while inducing anti-inflammatory cytokine production. Large-scale genomic analyses reveal that TA modules function as drivers of horizontal gene transfer networks, with their signatures enabling accurate prediction of plasmid community membership and serving as determinants of microbial community structure. The biotechnological applications of TA modules have expanded to include genetic circuit stabilization, biocontainment device construction, and multi-species microbial community engineering, while therapeutic strategies focus on developing multi-target inhibitors against conserved TA protein families as promising approaches for combating drug-resistant bacterial infections. The evolutionary conservation of TA modules across diverse bacterial lineages underscores their fundamental importance as central organizing principles in bacterial adaptation strategies, where their multifunctional nature reflects complex selective pressures operating across environmental niches and host-associated ecosystems. This review provides an integrated perspective on TA modules as dynamic regulatory elements that support bacterial persistence, immune evasion, and ecological versatility, establishing them as genetic elements with truly “many faces and functions” in prokaryotic biology. Full article

SENP1 (sentrin-specific protease 1) mediates sumoylation, a reversible post-translational modification that attaches the SUMO (small ubiquitin-like modifier) protein to target proteins. These modified proteins are essential in many key cellular processes, including cell cycle regulation, DNA repair, and apoptosis. Disruptions in the balance between sumoylated and desumoylated proteins can lead to various pathological conditions, such as cancer. Experimental data suggest that certain natural compounds, including momordin Ic (Mc), hinokiflavone (HNK), triptolide (TPL), ursolic acid (UA), streptonigrin (SN), vialinin A (VA), thelephantin G (TG), and others, effectively inhibit SENP1 activity, thereby influencing the levels of sumoylated proteins and cellular processes. This article reviews existing knowledge on the structure and function of natural SENP1 inhibitors, particularly their potential application in cancer therapy, including their capacity to overcome resistance to conventional chemotherapies. Some of the natural SENP1 inhibitors tested so far interact directly with the enzyme’s active site. The current understanding of how this interaction occurs is also discussed. Full article

Background: Annona cherimola Miller (A. cherimola) is traditionally used in Mexico to treat diabetes. Objectives: this study aimed to evaluate the antihyperglycemic activity of the aqueous leaf extracts (AEAcL) and stem (AEAcS) of A. cherimola alone and combined with oral antidiabetic drugs (OADs), as well as to determine their effect on % HbA1c, lipid parameters and toxicity. As well, the study aimed to isolate and identify some of its compounds to propose findings about its mode of action. Methods: Antihyperglycemic activity was evaluated using in vivo models with streptozotocin-induced experimental diabetes in Balb/c mice. Computer tools were used to obtain the pharmacokinetic and toxicological properties of the identified flavonoids; to obtain findings on their potential as α-glucosidase and SGLT1 inhibitors, in vivo and in silico studies were carried out using oral sucrose tolerance (OSTT) and glucose (OGTT) tests and molecular coupling studies. Results: ÇAEs and aSAAcS administered alone at 200 mg/kg showed a significant reduction in hyperglycemia. The best combination was AEAcL + Met (100/500 mg/kg), which significantly reduced hyperglycemic values and the % of HbA1c, TG, and LDL. The flavonoids isolated from AEAcL were identified as rutin, nicotiflorin, and narcissin. The molecular coupling assay and OSTT and OGTT tests showed that the flavonoids could inhibit α-glucosidase and SGLT1. Conclusions: AEAcL shows significant antihyperglycemic and antihyperlipidemic activity in murine models of diabetes, both alone (100 mg/kg) and in combination with metformin (100/500 mg/kg). Isolated flavonoids (rutin, nicotiflorin, and narcissine) appear to be partly responsible for these effects, although they have pharmacokinetic limitations. In silico and in vivo studies suggest a possible mechanism of action by inhibition of α-glucosidase and SGLT1. Full article

Serine protease inhibitor A3 (SERPINA3), also called α-1-antichymotrypsin, is a serine protease involved in placental dysfunction. This study examines SERPINA3 polymorphisms and haplotypes for associations with maternal hypertensive disorders of pregnancy (HDPs) and preeclampsia with severe features (sPE) or Hemolysis, Elevated Liver Enzymes, and Low Platelet (HELLP) syndrome in mother–baby dyads (HDP) and mother–father–baby triads (sPE/HELLP). This retrospective case–control study examined two patient cohorts, HDPs and severe PE/HELLP syndrome. The HDP population included cases (n = 142) and controls (n = 168) of mother–baby dyads recruited from a large, urban, safety-net hospital in Los Angeles. The sPE/HELLP syndrome population included cases (n = 189) and controls (n = 28) of mother–father–baby triads recruited through HELLP syndrome research websites. Cases were verified by medical chart abstraction when possible. Two SERPINA3 SNPs, rs4934 and rs1884082, were genotyped from saliva samples, mouthwash, or buccal swabs. The Haplin package in R was used to perform genetic association analyses. No evidence of increased risk related to individual SERPINA3 SNPs or haplotypes for the developing HDPs or sPE/HELLP was found in individual nor combined cohorts. In the HDP cohort, the g-a haplotype (relative to T-G haplotype) was borderline significant for increased risk of HDPs when carried by the child (double dose: RR = 1.58, 95% CI: (1.00, 2.52), p = 0.05). We observed significant parent-of-origin (PoO) effects in the combined cohort: specifically, an increased risk of HDPs/sPE/HELLP if the mother carries a double copy for both rs4934 (RR = 3.03, 95% CI (1.50, 6.09), p < 0.01) and rs1884082 (RR = 2.38, 95% CI (1.22, 4.71), p = 0.01). A reduced risk of HDPs/sPE/HELLP was observed for rs4934 (RR = 0.54, 95% CI (0.31, 0.98), p = 0.04) and rs1884082 (RR = 0.52, 95% CI (0.30, 0.91), p = 0.02) with child carriage of the maternally inherited allele. In contrast, child carriage of a paternally inherited copy of the variant allele for rs4934 increased risk of HDPs/sPE/HELLP (RR = 1.54, 95% CI (1.09, 2.20), p = 0.02). There was no evidence that SERPINA3 gene polymorphisms and haplotypes were associated with risk of HDPs or sPE/HELLP. However, significant PoO effects were observed in the combined cohort analysis, with child carriage of rs4934 that is maternally inherited decreasing HDPs/sPE/HELLP risk while a paternally inherited copy increases risk, suggesting a role for maternal–fetal genomic incompatibility. Full article

Background: Severe hypertriglyceridemia (SHTG) is associated with acute pancreatitis, metabolic dysfunction, and increased cardiovascular risk. Its genetic architecture ranges from rare biallelic variants causing familial chylomicronemia syndrome (FCS) to more prevalent polygenic or multifactorial chylomicronemia syndromes (MCS). Methods: We systematically reviewed scientific literature up to 2025 for studies reporting genetic data, clinical features, or therapeutic outcomes in adults with triglycerides (TG) ≥ 500 mg/dL. Extracted data were synthesized for genotype, polygenic risk score (PRS), TG levels, metabolic comorbidities, hepatic steatosis, pancreatitis, and treatment response. Results: Ten studies (n = 2521) were included. FCS due to biallelic LPL, APOC2, GPIHBP1, or LMF1 variants accounted for <5% of cases and showed extreme TG elevations (>2800 mg/dL) with pancreatitis prevalence (>70%). APOA5, APOC3, and APOB variants were associated with intermediate TG levels and high rates of metabolic dysfunction-associated steatotic liver disease (MASLD). Polygenic hypertriglyceridemia represented ~70–80% of cases, with TG ≈ 2200 mg/dL and pancreatitis prevalence 15–20%, largely modulated by metabolic triggers. MASLD was present in >70% of polygenic cases, supporting a “two-hit” model where hepatic overproduction of TG-rich lipoproteins amplifies TG excess. Interventional trials demonstrated TG reductions with APOC3 antisense therapy (70–80%) and ANGPTL3 inhibition (50–55%), while GLP-1RA significantly reduced hepatic fat (30–35%) and resolved NASH in up to 59% of patients. Conclusions: SHTG displays a genotype–phenotype gradient: FCS is linked to recurrent pancreatitis, whereas polygenic/MCS forms are closely associated with MASLD and metabolic dysfunction. These findings support a precision-medicine approach integrating genetic testing and PRS-guided strategies—prioritizing APOC3/ANGPTL3 inhibitors for FCS and combined TG-lowering plus metabolic therapies for MCS—to reduce pancreatitis recurrence and liver disease. Full article

Myotonic Dystrophy type 1 (DM1) is a complex disease affecting multiple tissues, including skeletal and cardiac muscles, the brain and the eyes. DM1 results from an expansion of CTG repeats in the 3′ UTR of the DMPK gene. Previously, we described that the small-molecule inhibitor of GSK3β, tideglusib (TG), reduces DM1 pathology in DM1 cell and mouse models by correcting the GSK3β-CUGBP1 pathway, decreasing the mutant CUG-containing RNA. Respectively, clinical trials using TG showed promising results for patients with congenital DM1 (CDM1). The drug development in DM1 human studies needs specific and noninvasive biomarkers. We examined the blood levels of active GSK3β in different clinical forms of DM1 and found an increase in active GSK3β in the peripheral blood mononuclear cells (PBMCs) in patients with CDM1, juvenile DM1 and adult-onset DM1 vs. unaffected patients. The blood levels of active GSK3β correlate with the length of CTG repeats and severity of muscle weakness. Thrombospondin and TGFβ, linked to the TG-GSK3β pathway in DM1, are also elevated in the DM1 patients’ blood. These findings show that the blood levels of active GSK3β might be developed as a potential noninvasive biomarker of muscle weakness in DM1. Full article

Objective: This study aimed to compare the effects of empagliflozin and dapagliflozin on classical lipid parameters—including total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides (TG)—as well as on atherogenic risk indices, including the atherogenic index of plasma (AIP), Castelli Risk Index I (CRI-I), Castelli Risk Index II (CRI-II), atherogenic coefficient (AC), and triglyceride-glucose index (TyG), in patients with heart failure and a history of coronary artery bypass grafting (CABG). To our knowledge, this is the first study to comprehensively evaluate these parameters in this high-risk population. Methods: This single-center, retrospective study included 484 patients with preserved ejection fraction heart failure and prior CABG who were treated with sodium–glucose cotransporter-2 (SGLT2) inhibitors. Patients were allocated to empagliflozin (n = 201) or dapagliflozin (n = 283) groups. All patients were receiving statin therapy. Lipid parameters and atherogenic indices were evaluated at baseline and after 12 weeks of treatment. Results: Both empagliflozin and dapagliflozin significantly reduced TC and LDL-C at 12 weeks (p < 0.001). No significant changes were observed in HDL-C or TG. Both agents produced significant improvements in CRI-I, CRI-II, AC, and TyG index (all p < 0.001), while AIP remained unchanged. Dapagliflozin achieved a greater reduction in TC (p = 0.044). Conclusions: This study represents the first direct comparison of empagliflozin and dapagliflozin on lipid profiles and atherogenic indices in patients with heart failure and prior CABG. Both agents significantly improved TC, LDL-C, and atherogenic indices. Dapagliflozin achieved a greater reduction in TC compared with empagliflozin, but overall both drugs demonstrated favorable and largely comparable effects. Beyond improvements in absolute values, both agents also contributed to favorable shifts in risk categories of lipid-derived indices. These findings suggest that clinical decision-making between empagliflozin and dapagliflozin may rely on factors other than lipid modulation. Larger multicenter prospective trials are warranted to confirm these results and clarify their long-term cardiovascular implications. Full article

Heat stress induces metabolic adaptations in fish, including the regulation of triglyceride (TG) synthesis/degradation to preserve cellular lipid balance and energy homeostasis. Diacylglycerol acyltransferase (DGAT) catalyzes the final step in TG synthesis. However, the molecular mechanisms by which DGAT regulates TG metabolism in heat-stressed fish remain unexplored. Our previous study suggested that miR-10c regulates dgat2 expression in genetically improved farmed tilapia (GIFT, Oreochromis niloticus) under heat stress. Here, we characterized the GIFT miR-10c precursor as a 65-nucleotide transcript yielding a 22 nt mature miRNA (oni-miR-10c). A phylogenetic analysis revealed a high level of miR-10c sequence conservation across species. A dual-luciferase reporter assay confirmed dgat2 as a direct target of miR-10c. Overexpression of miR-10c in vivo down-regulated dgat2 transcripts and DGAT2 protein. SiRNA-knockdown of dgat2 resulted in upregulation of cpt1α, fas, and lpl and downregulation of hsl, thereby reprogramming lipid metabolism in GIFT hepatocytes. Thus, the miR-10c-dgat2 regulatory axis facilitates TG hydrolysis and promotes fatty acid metabolism under heat stress. Our findings highlight miR-10c’s potential as a dgat2 inhibitor and its function in regulating lipid metabolism in heat-stressed GIFT. Our study reveals a key molecular pathway mediating thermal adaptation of energy metabolism in fish, providing novel targets for preventing heat-induced metabolic disorders. Full article

Increased hepatic triacylglycerol (TG) storage in lipid droplets (LDs) is a hallmark of metabolic dysfunction-associated steatotic liver disease (MASLD) and metabolic dysfunction-associated steatohepatitis (MASH). Human carboxylesterase 1 (CES1) regulates TG storage and secretion in hepatocytes, but the mechanism remains to be elucidated. We performed studies in rat hepatoma McArdle RH7777 cells stably transfected with CES1 cDNA and in Ces1d-deficient mice using a variety of biochemical, pharmacological and cell biology approaches including the assessment of gene expression, confocal immunofluorescence microscopy, lipid synthesis measurements and quantitative mass spectrometry. CES1-expressing cells accrued more TG compared to cells lacking CES1 when incubated with oleic acid. CES1 increased the expression of Srebf1c, Nr1h3 and Nr1h2 encoding transcription factors (SREBP1c and LXRα and LXRβ, respectively) that regulate the expression of lipogenic genes. Additionally, CES1 increased the expression of Acsl1 encoding an enzyme catalyzing fatty acid activation and the expression of Dgat1 and Dgat2 encoding enzymes catalyzing TG synthesis. Treatment of CES1-expressing cells with PPARγ antagonist (GW9662), LXR antagonist (GSK2033) or CYP27A1 inhibitor Felodipine prevented CES1-mediated fatty acid esterification into TG. Ces1d-deficient mice fed high-fat diet (HFD) presented with decreased expression of Nr1h3, Nr1h2, Srebf1c and reduced hepatic TG content. Felodipine and GSK2033 treatment eliminated the differential effects on TG concentration between wild-type and Ces1d-deficient hepatocytes. The results suggest that CES1/Ces1d activates PPARγ, LXR and SREBP1c pathways, thereby increasing TG synthesis and LD storage by augmenting fatty acid esterification. Full article

Background: Differentiated thyroid cancer (DTC) is commonly treated with radioactive iodine (RAI), but resistance to RAI remains a significant clinical challenge. The molecular mechanisms driving dedifferentiation and RAI refractoriness, particularly in BRAF^V600E-mutated tumors, are not fully understood. Methods: RNA sequencing was conducted on BRAF^V600E-mutated DTC and RAIR-DTC tissue samples to identify differentially expressed genes. Gadd45B was identified as significantly downregulated in RAIR-DTC. Functional studies including overexpression and knockdown experiments were performed in thyroid cancer cell lines and xenograft models. Downstream targets, including MAP3K4 and MYCBP, were evaluated through co-immunoprecipitation, luciferase assays, and Western blot. The therapeutic efficacy of recombinant Gadd45B protein in combination with BRAF^V600E and TERT inhibitors was assessed in patient-derived xenograft (PDX) models. Results: Gadd45B overexpression suppressed MAPK pathway activity by interacting with MAP3K4 and downregulated c-MYC stability through competition with MYCBP. These interactions enhanced the expression of iodine-metabolism genes (NIS, TPO, Tg), increased RAI uptake, and reversed tumor dedifferentiation. In vivo, Gadd45B restoration reduced tumor burden and improved RAI uptake. Combined treatment with Gadd45B protein, PLX4720, and BIBR1532 produced synergistic therapeutic effects in PDX models. Conclusions: Gadd45B plays a pivotal role in regulating the differentiation status and RAI sensitivity of BRAF^V600E-mutated thyroid cancer. These findings identify Gadd45B as a promising therapeutic target for restoring RAI responsiveness in RAIR-DTC patients. Full article

Background: Mycobacterium avium (Mav) is a leading cause of pulmonary disease among non-tuberculous mycobacteria (NTMs) due to its extensive antibiotic resistance profile. The essential Rel protein is a bifunctional enzyme, which is sensitive to environmental stress and regulates cellular guanosine-3′,5′-bispyrophosphate ((p)ppGpp). Increased levels of the alarmone thereby initiate a survival response, contributing to bacterial persistence and virulence. Objectives: MavRel harbors an unusual extension at the N-terminal domain (NTD), which we aim to characterize its possible regulatory role in maintaining (p)ppGpp homeostasis. We also studied whether the TGS domain retains its regulation capacity in MavRel and the binding propensity of the ACT domain to valine. Methods: Molecular dissection of MavRel was performed to generate a series of truncates to quantify the synthetase and hydrolase activities. Binding experiments with tRNA and valine were carried out via tryptophan quenching assay and NMR, respectively. Results: Bi-catalytic regulation of MavRel was found to be predominantly governed by the residues 37–50 at the NTD extension in its free state. The TGS domain was shown to harbor the capacity to bind with deacylated tRNA and represses synthetase activity to a lower degree compared to the NTD extension. We also characterized the dimeric Mav ACT-domain and the interacting residues contributing to its affinity with valine to function as a nutrient sensor. Conclusions: The mapping of the unique NTD regulatory element of MavRel reveals its functional relevance to coordinate the catalytic states of synthetase and hydrolase, hence underscores the prospect to drive inhibitor development targeting this novel site against Mav infections. Full article