Search Results (146)

Rosacea is a chronic inflammatory skin disorder driven by dysregulated cathelicidin processing and excessive LL-37, which triggers a circuit involving Toll-like receptor 2 (TLR2)/kallikrein-5 (KLK5)-dependent amplification and downstream mechanistic target of rapamycin complex 1 (mTORC1), NF-κB, and NLR family pyrin domain containing 3 (NLRP3) inflammasome pathways. We hypothesized that poly-D,L-lactic acid (PDLLA) could attenuate this inflammatory cascade by inducing macrophage-derived interleukin (IL)-10. PDLLA increased IL-10 secretion from THP-1-derived macrophages in a dose-dependent manner. In LL-37-stimulated HaCaT keratinocytes, LL-37 decreased phosphorylated signal transducer and activator of transcription (pSTAT3)/STAT3, DNA damage-inducible transcript 4 (DDIT4), and phosphorylated AMP-activated protein kinase (pAMPK)/AMPK while increasing phosphorylated protein kinase B (pAKT)/AKT and mTORC1 activation; conditioned media from PDLLA-treated macrophages (CM_PDLLA) restored pSTAT3/STAT3, DDIT4, and pAMPK/AMPK, reduced pAKT/AKT, and suppressed pmTOR/mTOR. CM_PDLLA attenuated downstream inflammatory responses, including NF-κB nuclear translocation, VEGF production, and NLRP3-inflammasome-mediated IL-18 secretion. These findings were validated using an intradermal LL-37-injected mouse model. Compared with the normal control/saline group, LL-37/saline decreased IL-10, pSTAT3/STAT3, DDIT4, and pAMPK/AMPK while increasing pAKT/AKT, pmTOR/mTOR, pS6K/S6K, TLR2/KLK5/LL-37, NF-κB, VEGF, and NLRP3 inflammasome/IL-18 signaling; PDLLA partially restored the STAT3/DDIT4–AMPK regulatory pattern and suppressed these disease-associated signals. Consequently, PDLLA treatment led to a pronounced reduction in clinical lesion area. Overall, PDLLA may attenuate LL-37-driven cutaneous inflammation by promoting an IL-10-linked STAT3/DDIT4–AKT/AMPK program that suppresses mTORC1 and disrupts cathelicidin amplification, supporting its potential as an injectable immunomodulatory approach for rosacea-like skin inflammation. Full article

Background: The mechanistic target of rapamycin (mTOR) is a highly conserved serine/threonine protein kinase that integrates inputs on nutrient status, energy levels, and growth factor stimulation to accordingly regulate cell growth and metabolism. It does this by activating or repressing target proteins covering a broad array of cellular processes. mTOR nucleates two structurally and functionally distinct protein complexes, mTORC1 and mTORC2. Because of their wide-ranging effects in the cell, both mTOR complexes are presumed to have a large number of targets. However, only a relatively small number have been conclusively identified. Methods: With emphasis on mammalian mTOR, we previously reviewed the extensive mTOR literature (1991–2021) and compiled a list of all reported substrates of mTORC1 and mTORC2. We have updated this list for the period 2022–2025. Results/Conclusions: Many of the targets are involved in autophagy, underscoring the major role of mTOR in the regulation of this process. From the perspective of this Special Issue, targets linked to cancer may be responsible for executing an mTOR-driven pro-oncogenic program and merit future study. Full article

Cigarette smoking contributes to vascular aging through oxidative stress, inflammation, and extracellular matrix (ECM) remodeling. Cellular senescence has been recognized as an important mechanism linking tobacco exposure to vascular dysfunction, but effective pharmacological strategies targeting this process remain scarce. In this study, we examined whether Rapalink-1, a dual inhibitor of mechanistic target of rapamycin complex 1 and complex 2 (mTORC1 and mTORC2), modulates smoke condensate (SC)-induced senescence in vascular cells. Human umbilical vein endothelial cells (HUVECs) and vascular smooth muscle cells (SMCs) were exposed to SC with or without Rapalink-1. SC increased intracellular reactive oxygen species, induced DNA damage, and promoted senescence-associated changes, including increased senescence-associated β-galactosidase (SA-β-gal) activity, reduced Lamin B1, and elevated p21 expression. These effects were accompanied by increased expression of inflammatory and matrix-remodeling genes associated with the senescence-associated secretory phenotype (SASP). Rapalink-1 co-treatment reduced oxidative stress and DNA damage, attenuated senescence markers, and partially normalized SASP-related and ECM-associated gene expression. Mechanistically, SC activated nuclear factor kappa B (NF-κB) and mitogen-activated protein kinase (MAPK) signaling and increased downstream mTOR pathway activity, whereas Rapalink-1 dampened these signaling responses. Together, these findings indicate that dual mTORC1/2 inhibition by Rapalink-1 mitigates smoke condensate-induced senescence and inflammatory responses in vascular cells. Full article

MDM4 (Murine Double Minute 4), also known as MDMX, is a crucial negative regulator of the tumor suppressor p53. MDM4 heterodimerizes with MDM2 to enhance MDM2-mediated ubiquitination and degradation of p53, thereby promoting tumorigenesis. Beyond its canonical role in inhibiting p53 activity, recent studies have revealed diverse p53-independent functions. MDM4 interacts with various proteins, including p73, E2F1, casein kinase 1α, PPARα, and TRIM21 to regulate cell cycle progression, β-catenin-mediated pre-leukemic progression, and ferroptosis independent of p53. In addition, MDM4 functions independently of both p53 and MDM2 by interacting with proteins, such as SMAD family members 3/4, retinoblastoma protein (pRB), p21, Nbs1 (also known as Nibrin), mTOR complex 1 (mTORC1), and the Polycomb Repressive Complexes (PRCs) complex, to control cell proliferation and survival, as well as protein degradation, double-strand break (DSB) repair, and replication fork progression. Intriguingly, multiple studies suggest that MDM4 exhibits oncogenic activity independent of p53; however, other reports highlight a potential tumor-suppressive role for MDM4 in the absence of p53. Thus, MDM4’s functions extend well beyond the canonical p53–MDM2 axis. A deeper understanding of MDM4 biology may facilitate the development of novel targeted therapies for various cancers. Full article

Introduction and Background: High-grade serous ovarian carcinoma (HGSOC) is notorious for its poor prognosis owing to its inherent biological aggressiveness and development of chemoresistance. The mechanistic target of rapamycin (mTOR) pathway is dysregulated in 55% of epithelial ovarian cancers, representing an appealing therapeutic target. To date, the clinical trials of mTOR inhibitors have shown modest response. In this study, we investigated the mTOR pathway in a clinical cohort of primary, chemo-naive, high-grade ovarian cancer samples, along with its regulatory post-transcriptional miRNA regulation. Methodology: We performed differential gene expression analysis on 100 HGSOC patients from TCGA and 80 healthy controls (i.e., normal ovarian tissue) from GTEx. The differentially expressed genes (DEGs) were overlaid onto the KEGG mTOR signalling pathway, followed by functional enrichment analysis. Next, we conducted differential miRNA expression analysis on the same cohort and identified regulatory miRNA–mTOR gene pairs involved in cancer pathogenesis. Finally, we constructed an interaction network and identified key hub genes and miRNAs with potential prognostic significance. Results: We identified 95 mTOR pathway genes that were significantly differentially expressed, involving upstream regulators, core components, and downstream effectors. Functional pathway analysis revealed a prominent shift toward mTORC1 activation, accompanied by paradoxical activation of autophagy. The let-7 miRNA family was identified as a key regulator of the mTOR pathway, potentially facilitating disease progression. RICTOR downregulation, a key component of the mTORC2 complex, appears to play a critical role in this histotype. In addition, FNIP1, a tumour suppressor gene implicated in mTOR dysregulation, was found to correlate with survival outcomes. Conclusions: We propose a model of dual activation of mTORC1 and autophagy in HGSOC as the metabolic rewiring enabling cancer progression under nutrient and cellular stress. Full article

Tuberous Sclerosis Complex (TSC) is a genetic disorder caused by mutations that inactivate TSC1 or TSC2 genes. TSC1 or TSC2 mutations activate the mammalian target of rapamycin complex 1 (mTORC1) protein kinase pathway. Although many patients inherit a single copy of a mutant TSC gene, somatic mutations that cause loss of heterozygosity in inhibitory neuroprogenitor cells are hypothesized to be one cause of abnormal development. This may lead to cortical malformations or benign growths along the ventricular-subventricular zone (V-SVZ), cortex, olfactory tract, and olfactory bulbs (OB). This idea is supported by focal single-cell knockout experiments that induce CRE-mediated recombination following neonatal electroporation of conditional Tsc2 or Tsc1 mice. Loss of Tsc2 causes mTORC1 pathway activation and the formation of striatal hamartomas composed of ectopic clusters of abnormal cells and cytomegalic neurons, including within the OB. Neural phenotypes in this model can be partially rescued with Rapalink-1, a bisteric mTOR inhibitor, demonstrating the importance of mTOR in pathogenesis. We previously demonstrated that global V-SVZ neural stem cell (NSC) Tsc2 mutation induced by nestin-CRE-ER^T2 causes mTORC1 pathway activation, which is accompanied by transcriptional and translational errors. While we previously described cultured NSCs and OB granule cells from these mice, we did not thoroughly describe changes outside this region. Here, we provide evidence that removal of Tsc2 from neonatal V-SVZ NSCs causes subtle and rare brain malformations. This is exemplified by ectopic clusters of cytomegalic neurons and mTORC1 activation. This data supports that loss of Tsc2 in NSCs during neonatal development leads to heterotopic clusters in the adult brain. This model may be useful to study TSC, but the rarity and stochastic nature of lesions make the use challenging for identifying mechanisms and testing therapies. Full article

Cancer cells can sustain survival independently of exogenous growth factors. To investigate their adaptation to serum deprivation, we analyzed transcriptomic responses in two cancer cell lines. Transcriptome analysis revealed upregulation of mRNAs encoding cholesterol biosynthesis enzymes. This was a critical adaptive response, as a pharmacological inhibition of the pathway with statin triggered a robust apoptotic cell death accompanied by generation of a mitochondrial reactive oxygen species. The mechanistic target of rapamycin complex 1 (mTORC1), a master regulator of cell growth, is known to be engaged in controlling lipid biosynthesis. We detected the high polysomal and preribosomal peaks not only in serum-containing medium but also under serum deprivation, indicating a high rate of protein synthesis and ribosomal biogenesis independent of serum. In addition, the inhibition of mTOR kinase activity substantially reduced polysome abundance, with a more pronounced effect in serum-deprived cancer cells. Notably, the mTOR kinase inhibition also prevented the upregulation of the cholesterol synthesis enzyme that established a direct link between mTOR activity, protein synthesis, and cholesterol biosynthesis. Together, our results show that cancer cells adapt to serum withdrawal by activating the cholesterol synthesis pathway through mTOR-dependent regulation of gene expression and protein synthesis, underscoring a critical mechanism of survival under serum withdrawal. Full article

The mammalian target of rapamycin pathway, mTOR, is a crucial signaling pathway that regulates cell growth, proliferation, metabolism, and survival. Due to its dysregulation it is involved in several ailments such as cancer or age-related diseases. The discovery of mTOR and the understanding of its biological functions were greatly facilitated by the use of rapamycin, an antibiotic of natural origin, which allosterically inhibits mTORC1, effectively blocking its function. In this entirely computational study, we investigated mTOR’s interaction with seven ligands: two clinically established inhibitors (everolimus and rapamycin) and five lignin-derived oligomers, a renewable natural polyphenol recently used for the drug delivery of everolimus. The seven complexes were analyzed through all-atom molecular dynamics simulations in explicit solvent using a high-performance computing platform. Trajectory analyses revealed stable interactions between mTOR and all ligands, with lignin-derived compounds showing comparable or enhanced binding stability relative to reference drugs. To evaluate the stability of the molecular complex and the behavior of the ligand over time, we analyzed key parameters including root mean square deviation, root mean square fluctuation, number of hydrogen bonds, binding free energy, and conformational dynamics assessed through principal component analysis. Our results suggest that lignin fragments are a promising, sustainable scaffold for developing novel mTOR inhibitors. Full article

Epstein-Barr Virus (EBV) is a causative agent of infectious mononucleosis and is strongly associated with Burkitt lymphoma, Hodgkin lymphoma, and nasopharyngeal carcinoma. EBV encodes a deubiquitinating enzyme, BPLF1, which is important for infectious virus production, B-cell immortalization, and tumorigenesis. To elucidate BPLF1’s role, an affinity-based mass spectrometry screen was performed, which suggested that BPLF1 and mTOR interact. mTOR, a critical mediator within cellular signaling cascades and oncogenesis, exists in two distinct complexes: mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2). Here, we show that BPLF1 has direct deubiquitinating (DUB) activity on mTOR, removing both K48- and K63-ubiquitin linkages. Additionally, WT BPLF1 decreased mTORC1 localization to the lysosome and decreased the phosphorylation of mTORC1 downstream effectors, 4E-BP1 and S6K1. BPLF1 also had DUB activity on Raptor and Rictor, which have both been shown to preferentially cause the formation of mTORC2 over mTORC1 when not ubiquitinated. Immunoprecipitation of mTOR shows decreased mTORC1 formation in the presence of WT BPLF1. Importantly, treatment with rapamycin, an mTORC1 inhibitor, increased infectious virus production, while JR-AB2-011, an mTORC2 inhibitor, reduced infectious virus production. Taken together, these data demonstrate that BPLF1’s effect on the mTOR signaling cascade regulates cellular and viral processes during EBV infectivity and replication. Full article

Endurance athletes frequently experience muscle damage and inflammation due to prolonged, high-intensity exercise, which can impair recovery and hinder performance. This review examines the role of branched-chain amino acid (BCAA) supplementation in muscle repair, inflammation modulation, and immune regulation. BCAAs—particularly leucine and isoleucine—activate key molecular pathways, including the mechanistic target of rapamycin (mTOR) and AMP-activated protein kinase (AMPK), to promote muscle protein synthesis and enhance energy metabolism. They also attenuate inflammatory responses by modulating the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), mitogen-activated protein kinase (MAPK), and Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathways, reducing levels of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6). In addition, BCAAs influence immune function via mechanistic target of rapamycin complex 1 (mTORC1) signaling, enhance autophagy, and mitigate exercise-induced apoptosis. These molecular effects result in reduced muscle soreness, lower muscle damage biomarker levels (e.g., creatine kinase, lactate dehydrogenase), and improved recovery. Practical considerations such as optimal dosage, timing, and co-supplementation with carbohydrates, proteins, or omega-3s are also addressed. While BCAAs show promise as a nutritional strategy for enhancing recovery and controlling inflammation in endurance athletes, further research is needed to refine personalized protocols and clarify long-term effects. Full article

Antiphospholipid antibody (aPL)-induced activation of the mTOR (mammalian target of rapamycin) signaling pathway in endothelial cells plays a role in the pathogenesis of vascular lesions in antiphospholipid syndrome (APS). However, there are no data on whether this mechanism also contributes to the development of skin ulcers commonly observed in APS. We investigated the activation of mTOR in skin specimens from aPL-positive and aPL-negative patients with leg ulcers. Patients with leg ulcers who had primary or secondary APS or no detectable aPLs were included in the study. Biopsies were taken from the ulcer edges and the adjacent non-ulcerated skin areas. Activation of mTORC1 (mTOR Complex1) and mTORC2 (mTOR Complex2) in endothelial cells was determined by immunohistochemical analysis of phosphorylated ribosomal S6 protein (pS6RP) and phosphorylated protein kinase B (pAKT), respectively. In all aPL-positive patients, regardless of whether they had primary or secondary APS, we found a positive immunohistochemical reaction to pS6RP (mTORC1 activation) in the endothelial cells of the ulcer samples. On the other hand, pS6RP could not be detected in samples from aPL-negative chronic venous ulcers. Furthermore, pS6RP was not present in samples taken from the unaffected skin adjacent to the ulcers in aPL-positive patients. The pAKT reaction (mTORC2) was negative in both aPL-positive and aPL-negative patients, both in the ulcers and in the periulcer skin. Activation of the mTOR pathway may contribute to ulcer development in APS. The mTORC1 may be a target for therapeutic modification in APS-associated skin ulcers. Full article

Mutations in TSC1 or TSC2 in axons induce tuberous sclerosis complex. Neurological manifestations mainly include epilepsy and autism spectrum disorder (ASD). ASD is the presenting symptom (25–50% of patients). ASD was observed at significantly higher frequencies in participants with TSC2 than those with TSC1 mutations. The occurrence of TSC2 mutations is about 50% larger than TSC1. Therefore, ASD may develop due to TSC2 deficiency. TSC2 regulates microRNA biogenesis and Microprocessor activity via GSK3β. Of reference, everolimus has the best treatment target because of the higher potency of interactions with mTORC2 rather than rapamycin. Mutations in the TSC1 and TSC2 genes result in the constitutive hyperactivation of the mammalian target of the rapamycin (mTOR) pathway, contributing to the growth of benign tumors or hamartomas in various organs. TSC2 mutations were associated with a more severe phenotypic spectrum than TSC1 mutations because of the inhibition of the mTOR cascade. There are few studies on the peptide analysis of this disorder in relation to everolimus. Only one study reported that, in ten plasma samples, pre-melanosome protein (PMEL) and S-adenosylmethionine (SAM) were significantly changed as diagnostic prognostic effects. Our study on peptide analysis in Protosera Inc (Osaka, Japan) revealed that three peptides that were related to inflammation in two patients with tuberous sclerosis, who showed a 30% decrease in ASD symptoms following everolimus treatment. TSC2 mutations were associated with a more severe phenotypic spectrum due to the inhibition of the mTOR cascade. PMEL and SAM were significantly changed as diagnostic effects. Full article

The mammalian target of rapamycin (mTOR), a serine/threonine kinase, promotes cell growth and inhibits autophagy. The following two complexes contain mTOR: mTORC1 with the regulatory associated protein of mTOR (RAPTOR) and mTORC2 with the rapamycin-insensitive companion of mTOR (RICTOR). The phosphatidylinositol 3-kinase (PI3K)/Akt/mTOR signaling pathway is important in the intervertebral disk, which is the largest avascular, hypoxic, low-nutrient organ in the body. To examine gene-silencing therapeutic approaches targeting PI3K/Akt/mTOR signaling in degenerative disk cells, an in vitro comparative study was designed between small interfering RNA (siRNA)-mediated RNA interference (RNAi) and clustered regularly interspaced short palindromic repeat (CRISPR)–CRISPR-associated protein 9 (Cas9) gene editing. Surgically obtained human disk nucleus pulposus cells were transfected with a siRNA or CRISPR–Cas9 plasmid targeting mTOR, RAPTOR, or RICTOR. Both of the approaches specifically suppressed target protein expression; however, the 24-h transfection efficiency differed by 53.8–60.3% for RNAi and 88.1–89.3% for CRISPR–Cas9 (p < 0.0001). Targeting mTOR, RAPTOR, and RICTOR all induced autophagy and inhibited apoptosis, senescence, pyroptosis, and matrix catabolism, with the most prominent effects observed with RAPTOR CRISPR–Cas9. In the time-course analysis, the 168-h suppression ratio of RAPTOR protein expression was 83.2% by CRISPR–Cas9 but only 8.8% by RNAi. While RNAi facilitates transient gene knockdown, CRISPR–Cas9 provides extensive gene knockout. Our findings suggest that RAPTOR/mTORC1 is a potential therapeutic target for degenerative disk disease. Full article

During development, a 14mer peptide, T14, modulates cell growth via the α-7 nicotinic acetylcholine receptor (α7 nAChR). However, this process could become excitotoxic in the context of the adult brain, leading to pathologies such as Alzheimer’s disease (AD). Recent work shows that T14 acts selectively via the mammalian target of rapamycin complex 1 (mTORC1). This pathway is essential for normal development but is overactive in AD. The triggering of mTORC1 has also been associated with the suppression of autophagy, commonly observed in ageing and neurodegeneration. We therefore investigated the relationship between T14 and autophagic flux in tissue cultures, mouse brain slices, and human Alzheimer’s disease hippocampus. Here, we demonstrate that T14 and p-mTOR s2448 expression significantly increases in AD human hippocampus, which was associated with the gradual decrease in the autophagosome number across Braak stages. During development, the reduction in T14 positively correlated with pTau (Ser202, Thr205) and two selective autophagy receptors: p62 and optineurin. In vitro studies also indicated that T14 increases p-mTOR s2448 expression, resulting in the aggregation of polyubiquinated substances. The effective blockade of T14 via its cyclic variant, NBP14, has been validated in vitro, in vivo, and ex vivo. In this study, NBP14 significantly attenuated p-mTOR s2448 expression and restored normal autophagic flux, as seen with rapamycin. We conclude that T14 acts at the α-7 receptor to selectively activate the mTORC1 pathway and consequently inhibit autophagic flux. Hence, this study describes a further step in the process by which T14 could drive neurodegeneration. Full article

RAPTOR (regulatory-associated protein of mTOR) is a pivotal component of the mammalian target of rapamycin complex 1 (mTORC1), playing a central role in regulating cell growth, metabolism and stress responses. As a scaffold protein, RAPTOR recruits key substrates such as eukaryotic initiation factor 4E-binding protein-1 (4E-BP1) and ribosomal protein S6 kinase (S6K), facilitating their phosphorylation by mTORC1, which in turn drives protein synthesis, lipid metabolism and cellular proliferation. Its regulatory function becomes especially crucial under conditions of nutrient deprivation or stress, where it enhances the stability of the mTORC1 complex, allowing cells to adapt to fluctuating environmental cues. The hyperactivation of mTORC1, largely mediated by RAPTOR, is frequently observed in various cancers, contributing to uncontrolled cell proliferation and tumorigenesis. Moreover, RAPTOR’s modulation of immune responses and metabolic pathways extends its influence beyond oncogenesis, impacting inflammatory diseases and metabolic disorders. This review meticulously elucidates RAPTOR’s structure, post-translational modifications as well as its indispensable role within the mTORC1 complex, emphasizing its regulatory functions in cellular growth, metabolic adaptation, immune response and disease pathology including oncogenesis. Furthermore, it explores emergent therapeutic avenues targeting RAPTOR-mediated mTORC1 signaling, underscoring their potential to revolutionize cancer treatment and the management of related pathophysiological conditions. Full article