Regulation of mTORC2 Signaling

Potential mechanism of dietary palm kernel meal effect on muscle tenderness in Tibetan sheep revealed by proteomics and phosphorylated proteomics

The labe free proteomics technology and 4D labe free phosphorylation proteomics technology was used to systematically analyse the protein expression regulatory mechanisms of muscle tenderness. 59 differentially expressed proteins were screened by proteomic data analysis. Phosphorylated proteomic analysis showed 681 modified peptide levels were changed, of which 235 modified peptide levels corresponded to 132 proteins up-regulated and 446 modified peptide levels corresponded to 253 proteins down-regulated. Then, the two-omics analysis further predicted that the regulatory mechanism of tenderness was mainly based on glycolysis, regulating mitochondrial autophagy, apoptosis, AMPK and HIF-1 signaling pathway to regulate muscle tenderness, which was specifically manifested in the modulation of Ca2+ release to promote the degradation of myofibrillar fibrillar proteins by the relevant proteins, shortening of post-slaughter muscle glycolysis and reducing the degree of muscle glycolysis. Which was verified by WB, P53, ENO5, ALDOA, ENDOG and PINK1 were identified as potential factors for tenderness regulation.

Strategic advancements in targeting the PI3K/AKT/mTOR pathway for Breast cancer therapy

Breast cancer (BC) is a complex disease that affects millions of women worldwide. Its growing impact calls for advanced treatment strategies to improve patient outcomes. The PI3K/AKT/mTOR pathway is a key focus in BC therapy because it plays a major role in important processes like tumor growth, survival, and resistance to treatment. Targeting this pathway could lead to better treatment options and outcomes. The present review explores how the PI3K/AKT/mTOR pathway becomes dysregulated in BC, focusing on the genetic changes like PIK3CA mutations and PTEN loss that leads to its aggravation. Current treatment options include the use of inhibitors targeting PI3K, AKT, and mTOR with combination therapies showing promise in overcoming drug resistance and improving effectiveness. Looking ahead, next-generation inhibitors and personalized treatment plans guided by biomarker analysis may provide more accurate and effective options for patients. Integrating these pathway inhibitors with immunotherapy offers an exciting opportunity to boost anti-tumor responses and improve survival rates. This review offers a comprehensive summary of the current progress in targeting the PI3K/AKT/mTOR pathway in BC. It highlights future research directions and therapeutic strategies aimed at enhancing patient outcomes and quality of life.

mTOR inhibitors in targeting autophagy and autophagy-associated signaling for cancer cell death and therapy

The mechanistic target of rapamycin (mTOR) is a protein kinase that plays a central regulatory switch to control multifaceted cellular processes, including autophagy. As a nutrient sensor, mTOR inhibits autophagy by phosphorylating and inactivating key regulators, including ULK1, Beclin-1, UVRAG, and TFEB, preventing autophagy initiation and lysosomal biogenesis. It also suppresses autophagy-related protein expression, prioritizing growth over cellular recycling. Under nutrient deprivation, mTORC1 activity decreases, allowing autophagy to restore cellular homeostasis. Hyperautophagic activities lead to autophagic cell death; sometime after the point of no return, the cell goes for non-apoptotic, non-necrotic cell death i.e., Autosis. In cancer, the crosstalk between autophagy and mTOR is context-dependent, driving either cell survival or autophagy-dependent cell death. Using mTOR inhibitors, autophagic cell death can be induced to regulate cell growth, and proliferation is a potential therapeutic option for cancer treatment. mTOR inhibitors are broadly categorized into two types, i.e., natural and synthetic mTOR inhibitors. Although several studies in preclinical and clinical trials of various synthetic mTOR inhibitors are now in focus for cancer therapies, limited work has been done to explore autophagic cell death-inducing mTOR inhibitors. In addition, many natural mTOR inhibitors display better efficacy over synthetic mTOR inhibitors due to their lower toxicity, biocompatibility, and potential to overcome drug resistance, highlighting the current status of mTOR inhibitors in inducing autophagic cell death for cancer treatment.

Targeting of AMPK/MTOR signaling in the management of atherosclerosis: Outmost leveraging

Atherosclerosis (AS) is a chronic vascular disorder that is characterized by the thickening and narrowing of arteries due to the development of atherosclerotic plaques. The traditional risk factors involved in AS are obesity, type 2 diabetes (T2D), dyslipidemia, hypertension, and smoking. Furthermore, non-traditional risk factors for AS, such as inflammation, sleep disturbances, physical inactivity, air pollution, and alterations of gut microbiota, gained attention in relation to the pathogenesis of AS. Interestingly, the pathogenesis of AS, is complex and related to different abnormalities of cellular and sub-cellular signaling pathways. It has been illustrated that AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (MTOR) pathways are involved in AS pathogenesis. Mounting evidence indicated that AMPK plays a critical role in attenuating the development of AS by activating autophagy, which is impaired during atherogenesis. AMPK has a vasculoprotective effect by reducing lipid accumulation, inflammatory cell proliferation, and the release of pro-inflammatory cytokines, as well as decreasing inflammatory cell adhesion to the vascular endothelium. AMPK activation by metformin inhibits the migration of vascular smooth muscle cells (VSMCs) and AS development. However, the MTOR pathway contributes to AS by inhibiting autophagy, highlighting autophagy as a crucial link between the AMPK and MTOR pathways in AS pathogenesis. The MTOR is a key inducer of endothelial dysfunction and is involved in the development of AS. Therefore, both the AMPK and MTOR pathways play a crucial role in the pathogenesis of AS. However, the exact role of AMPK and MTOR pathways in the pathogenesis of AS is not fully clarified. Therefore, this review aims to discuss the potential role of the AMPK/MTOR signaling pathway in AS, and how AMPK activators and MTOR inhibitors influence the development and progression of AS. In conclusion, AMPK activators and MTOR inhibitors have vasculoprotective effects against the development and progression of AS.

LL37 promotes angiogenesis: a potential therapeutic strategy for lower limb ischemic diseases

Purpose

To study the angiogenic capacity of antimicrobial peptide LL37 (cathelicidin antimicrobial peptide), explore its molecular mechanisms, and provide new ideas for treating lower limb ischemic diseases.

Methods

LL37 was applied exogenously to human umbilical vein endothelial cells (HUVECs), and its effects on cell proliferation, migration, and angiogenesis were assessed using Cell Counting Kit-8 (CCK-8), plate cloning, scratch, and angiogenesis assays. A mouse lower limb ischemia model was established, with LL37 injected intramuscularly on days 0, 4, and 8. Blood flow recovery was evaluated by laser Doppler flowmetry. Immunofluorescence staining detected cluster of differentiation 31 (CD31) and cluster of differentiation 34 (CD34) expression, while Hematoxylin and Eosin (H&E) staining assessed muscle cell morphology. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting analyzed gene and protein expression changes in HUVECs.

Results

LL37 enhanced the proliferative, migratory, and pro-angiogenic abilities of HUVECs. It significantly improved blood flow recovery in ischemic limbs, with higher CD31/CD34 expression and more intact muscle morphology. qRT-PCR analysis demonstrated elevated expression of angiogenesis-related genes in LL37-treated HUVECs. Western blotting revealed increased vascular endothelial growth factor A (VEGFA) expression and enhanced phosphorylation levels of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) pathway in LL37-treated cells.

Conclusion

LL37 promotes angiogenesis via the VEGFA-PI3K/AKT/mTOR pathway, showing potential for treating lower limb ischemia by improving perfusion.

The transcription factor XBP1 regulates mitochondrial remodel and autophagy in spontaneous abortion

PURPOSE

Spontaneous abortion (SA) remains a clinical challenge in early pregnancy. It has been reported that endoplasmic reticulum stress (ERS) is implicated in pregnancy-related complications. However, the precise mechanistic role of ERS in SA pathogenesis remains elusive. This study aims to explore the therapeutic potential of targeting ERS-related decidual dysfunction in SA.

METHODS

An ERS model was established in both decidualized stromal cells (DSCs) and pregnant mice through tunicamycin (Tu) administration. Chromatin immunoprecipitation (ChIP) and dual-luciferase reporter assays were performed to determine the interaction between XBP1s and the transcription factor binding site (TFBS) of tumor necrosis factor receptor-associated factor 6 (TRAF6). Mitochondrial membrane potential (MMP) and mitochondrial function were assessed using JC-1 and TMRM staining following ERS induction in DSCs. The effects of XBP1s inhibitors on mitochondrial metabolism and autophagy were evaluated through RT-qPCR, Western blotting, RNA-Seq, TUNEL assays, ROS and MitoSOX detection, and histological analyses in Tu-treated DSCs and SA patients. STF-083010 (STF) or shXBP1 was utilized to assess the inhibitory effects of X-box binding protein 1 (XBP1s) on DSC function both in vitro and in vivo.

RESULTS

We observed significant upregulation of XBP1s in decidual tissues from SA patients and Tu-exposed DSCs. Tu exposure significantly increased the proportion of TUNEL-positive cells and upregulated pro-inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-18) in DSCs. XBP1s inhibition via shXBP1 or pharmacological inhibitor STF attenuated Tu-induced apoptosis and inflammatory cytokine expression. Notably, STF or shXBP1 treatment enhanced MMP and upregulated LC3-II expression in Tu-treated DSCs, indicating autophagy activation.Intriguingly, chloroquine (CQ)-mediated autophagy suppression exacerbated apoptosis in STF/Tu-co-treated DSCs, suggesting that XBP1s inhibition confers cytoprotection through autophagy induction. Mechanistically, XBP1s directly bound to the TFBS of TRAF6, a ubiquitin E3 ligase. TRAF6 overexpression exacerbated mitochondrial dysfunction and apoptosis while suppressing autophagy via inhibition of mTORC2/Akt pathway in Tu-treated DSCs.

CONCLUSION

XBP1s inhibition restored mitochondrial homeostasis and promoted autophagy by modulating the TRAF6/mTORC2 axis under ERS conditions, providing novel mechanistic insights into SA pathogenesis and potential therapeutic targets.

Mechanisms coupling the mTOR pathway to chronic obstructive pulmonary disease (COPD) pathogenesis

Chronic Obstructive Pulmonary Disease (COPD) is a poorly reversible respiratory disorder distinguished by dyspnea, cough, expectoration and exacerbations due to abnormality of airways or emphysema. In this review, we consider the therapeutic potential of targeting Mammalian target of Rapamycin (mTOR) for treating COPD. The mTOR is a highly conserved serine-threonine protein kinase that integrates signals from growth factors and nutrients to control protein synthesis, lipid biogenesis and metabolism. Dysregulated mTOR pathway signaling due to genetic factors or cigarette smoking impairs autophagy, driving the buildup of abnormal cells and damaged proteins, resulting in inflammation and oxidative stress. Persistent mTOR activation also contributes to pulmonary vascular cell proliferation, facilitating the development of pulmonary resistance in COPD. Rapamycin, an inhibitor of mTOR, prevents the buildup of senescent cells in the lungs of COPD patients and inhibits the release of lung tissue-damaging proteases. mTOR also impacts the corticosteroid sensitivity in COPD patients by regulating the levels of histone deacetylases. The emerging role of gut-lung axis dysbiosis in the progression of COPD and its influence on mTOR further highlights the relevance of the mTOR pathway in COPD pathophysiology.

The Central FacilitaTOR: Coordinating Transcription and Translation in Eukaryotes

One of the biggest challenges to eukaryotic gene expression is coordinating transcription in the nucleus and protein synthesis in the cytoplasm. However, little is known about how these major steps in gene expression are connected. The Target of Rapamycin (TOR) signaling pathway is crucial in connecting these critical phases of gene expression. Highly conserved among eukaryotic cells, TOR regulates growth, metabolism, and cellular equilibrium in response to changes in nutrients, energy levels, and stress conditions. This review examines the extensive role of TOR in gene expression regulation. We highlight how TOR is involved in phosphorylation, remodeling chromatin structure, and managing the factors that facilitate transcription and translation. Furthermore, the critical functions of TOR extend to processing RNA, assembling RNA-protein complexes, and managing their export from the nucleus, demonstrating its wide-reaching impact throughout the cell. Our discussion emphasizes the integral roles of TOR in bridging the processes of transcription and translation and explores how it orchestrates these complex cellular processes.

The mechanopathology of the tumor microenvironment: detection techniques, molecular mechanisms and therapeutic opportunities

The mechanical properties of the tumor microenvironment (TME) undergo significant changes during tumor growth, primarily driven by alterations in extracellular (ECM) stiffness and tumor viscoelasticity. These mechanical changes not only promote tumor progression but also hinder therapeutic efficacy by impairing drug delivery and activating mechanotransduction pathways that regulate crucial cellular processes such as migration, proliferation, and resistance to therapy. In this review, we examine the mechanisms through which tumor cells sense and transmit mechanical signals to maintain homeostasis in the biomechanically altered TME. We explore current computational modelling strategies for mechanotransduction pathways, highlighting the need for developing models that incorporate additional components of the mechanosignaling machinery. Furthermore, we review available methods for measuring the mechanical properties of tumors in clinical settings and strategies aiming at restoring the TME and blocking deregulated mechanotransduction pathways. Finally, we propose that proper characterization and a deeper understanding of the mechanical landscape of the TME, both at the tissue and cellular levels, are essential for developing therapeutic strategies that account for the influence of mechanical forces on treatment efficacy.

Genetic Diversity Estimation and Genome-Wide Selective Sweep Analysis of the Bazhou Yak

The Bazhou yak, a major native meat yak breed in Xinjiang, China, is renowned for its fast growth rate, strong adaptability, and particularly high intramuscular fat (IMF) content. However, limited knowledge regarding its phylogenetic history and genomic composition has hindered its long-term conservation and utilization. This study evaluated the genetic diversity, population phylogenetics, and genome-wide selective sweep analysis (GWSA) of 100 newly obtained Bazhou yaks through genome resequencing, as well as 340 public yak genomes from nine other populations on the Qinghai-Tibet Plateau. The results revealed moderate diversity, lower genomic inbreeding levels, and rapid linkage disequilibrium (LD) decay in Bazhou yaks. Principal component analysis (PCA) and phylogenetic analysis showed a clear separation of Bazhou yaks from other yak populations, indicating the Bazhou yak as an independent genetic population. Furthermore, less genetic differentiation was found between the Bazhou yak and the Huanhu yak, while ADMIXTURE analysis revealed a common ancestral lineage between Bazhou yaks and Huanhu yaks, indicating an important genetic contribution of the Qinghai yak population to Bazhou yaks. The GWSA identified a total of 833 selected genes in Bazhou yaks using the top 5% interaction windows of both parameters (FST, Pi ratio, and XP-EHH). A significant number of these genes are related to fat synthesis and deposition, such as MTOR, APOA1, and GPAT4. In summary, this study sheds light on the phylogenetic status and distinctive genomic features of Bazhou yaks, which facilitates our understanding of the genetic basis of the IMF phenotype in Bazhou yaks.

Lipid Transfer Proteins and PI4KIIα Initiate Nuclear p53-Phosphoinositide Signaling

Phosphoinositide (PIP n ) messengers are present in non-membranous regions of nuclei where they are assembled into a phosphatidylinositol (PI) 3-kinase (PI3K)/Akt pathway that is distinct from the cytosolic membrane-localized pathway. In the nuclear pathway, PI kinases/phosphatases bind the p53 tumor suppressor protein (wild-type and mutant) to generate p53-PIP n complexes (p53-PIP n signalosome) that activate Akt by a PI3,4,5P 3 -dependent mechanism in non-membranous regions of the nucleus. This pathway is dependent on a source of nuclear PIP n s that is poorly characterized. Here we report that a subset of PI transfer proteins (PITPs), which transport PI between membranes to enable membrane-localized PIP n synthesis, also interact with p53 in the nucleus upon genotoxic stress. Class I PITPs (PITPα/β) specifically supply the PI required for the generation of p53-PIP n complexes and subsequent signaling in the nucleus. Additionally, the PI 4-kinase PI4KIIα binds to p53 and the PITPs to catalyze the formation of p53-PI4P. p53-PI4P is then sequentially phosphorylated to synthesize p53-PIP n complexes that regulate p53 stability, nuclear Akt activation and genotoxic stress resistance. In this way, PITPα/β and PI4KIIα bind p53 and collaborate to initiate p53-PIP n signaling by mechanisms that require PI transfer by PITPα/β and the catalytic activity of PI4KIIα. Moreover, the identification of these critical upstream regulators of p53-PIP n signaling point to PITPα/β and PI4KIIα as novel therapeutic targets in this pathway for diseases like cancer.

Significance statement

PI transfer proteins and a PI 4-kinase initiate nuclear p53-phosphoinositide signaling in membrane-free regions to promote stress resistance.

mTORC2 Regulates Actin Polymerization in Auditory Cells

Mammalian target of rapamycin complex 2 (mTORC2) is essential for hearing by regulating auditory hair cell structure and function. However, mechanistic details of how mTORC2 regulates intracellular processes in sensory hair cells have not yet been clarified. To further elucidate the role of mTORC2 in auditory cells, we generated a Rictor knockout cell line from HEI-OC1 auditory cells. mTORC2-deficient auditory cells exhibited significant alterations in actin cytoskeleton morphology and decreased proliferation rates. Additionally, we observed a reduction in phosphorylation of protein kinase C alpha (PKCα) and disrupted actin polymerization in mTORC2-deficient cells. Using proteomics, we found that mTORC2 disruption altered expression of cytoskeleton-related proteins in auditory cells. These findings provide valuable mechanistic insights into the functional role of mTORC2 in auditory cells, potentially opening new perspectives to address sensorineural hearing loss.

mTORC1 regulates the proliferation of SOX9+ porcine skin-derived stem cells (pSDSCs) by promoting S6K phosphorylation

Skin-derived stem cells (SDSCs) are a subtype of adult stem cells (ASCs) that are widely harvested and exempt from ethical restrictions in clinical applications. These cells possess capabilities for self-renewal, proliferation, and multi-lineage differentiation. Compared to model animals like rats and mice, pigs exhibit greater physiological similarity to humans. Porcine skin has very similar histological and physiological characteristics to human skin. Therefore, porcine skin is becoming increasingly significant as an in vitro model for research. In this study, porcine skin-derived stem cells (pSDSCs) were isolated and cultured in vitro for experiments. The expression of stemness-related gene SOX9 was detected. RNA sequencing (RNA-seq) results found that the mammalian target of rapamycin (mTOR) signaling pathway was significantly enriched in SOX9+ pSDSCs. To investigate the role of the mTOR signaling pathway, we added rapamycin (RAPA), an inhibitor of the mTOR complex 1 (mTORC1), and found that the proliferation rate of SOX9+ pSDSCs decreased significantly during culture. In addition, western blotting (WB) results demonstrated that mTORC1 promoted proliferation by phosphorylating S6 kinase (S6K) and then activating cyclin D1(CCND1) in SOX9+ pSDSCs. These findings provide insights into the mechanisms of adult stem cell proliferation.

RICTOR-mediated activation of AKT/mTOR signaling and autophagy inhibition promote osteoarthritis

The most common joint disease in the elderly is osteoarthritis (OA), which is characterized by synovitis, cartilage degeneration, and osteophytes, for which there are currently no effective therapies. Chondrocytes, responsible for extracellular matrix (ECM) synthesis and degradation, undergo changes in OA, leading to ECM disruption and disease progression. There is no clear role for the Mechanistic target of rapamycin complex 2 (mTORC2) in OA, but it is known to regulate cellular functions, such as proliferation, metabolism, motility, and apoptosis. The purpose of this study was to determine the molecular mechanism by which Rapamycin-insensitive companion of mTOR (RICTOR), a component of mTORC2, contributes to OA progression. The results demonstrate that IL-1β induces high expression of RICTOR in chondrocytes, promoting downregulation of collagen II expression and impairing autophagy. Silencing RICTOR reverses IL-1β-induced downregulating of collagen II expression and mitochondrial dysfunction. RICTOR inhibits chondrocyte autophagy by inhibiting autophagosome formation and preventing autophagosome-lysosome fusion. Additionally, RICTOR promotes oxidative stress in chondrocytes, leading to disruption of normal mitochondrial structure and disturbance of the articular cartilage microenvironment. This study reveals the potential of RICTOR to treat OA. Specifically, blocking mTORC2 might be an effective treatment strategy.

Making PI3K superfamily enzymes run faster

The phosphoinositide 3-kinase (PI3K) superfamily includes lipid kinases (PI3Ks and type III PI4Ks) and a group of PI3K-like Ser/Thr protein kinases (PIKKs: mTOR, ATM, ATR, DNA-PKcs, SMG1 and TRRAP) that have a conserved C-terminal kinase domain. A common feature of the superfamily is that they have very low basal activity that can be greatly increased by a range of regulatory factors. Activators reconfigure the active site, causing a subtle realignment of the N-lobe of the kinase domain relative to the C-lobe. This realignment brings the ATP-binding loop in the N-lobe closer to the catalytic residues in the C-lobe. In addition, a conserved C-lobe feature known as the PIKK regulatory domain (PRD) also can change conformation, and PI3K activators can alter an analogous PRD-like region. Recent structures have shown that diverse activating influences can trigger these conformational changes, and a helical region clamping onto the kinase domain transmits regulatory interactions to bring about the active site realignment for more efficient catalysis. A recent report of a small-molecule activator of PI3Kα for application in nerve regeneration suggests that flexibility of these regulatory elements might be exploited to develop specific activators of all PI3K superfamily members. These activators could have roles in wound healing, anti-stroke therapy and treating neurodegeneration. We review common structural features of the PI3K superfamily that may make them amenable to activation.

High-density lipoprotein protects normotensive and hypertensive rats against ischemia-reperfusion injury through differential regulation of mTORC1 and mTORC2 signaling

Background

High-density lipoprotein (HDL) protects against myocardial ischemia-reperfusion (I/R) injury. Mammalian target of rapamycin complexes 1 and 2 (mTORC1 and mTORC2) play opposing roles in protecting against I/R injury, whereby mTORC1 appears to be detrimental while mTORC2 is protective. However, the role of HDL and mTORC signaling in protecting against I/R in hypertensive rodents is not clearly understood. In this study, we investigated the involvement of mTORC1 and mTORC2 in HDL-mediated protection against myocardial I/R injury in normotensive Wistar Kyoto (WKY) rats and spontaneously hypertensive rats (SHR).

Methods

Hearts from WKY and SHR were subjected to I/R injury using a modified Langendorff system. Hemodynamics data were collected, and infarct size was measured. Rapamycin and JR-AB2-011 were used to test the role of mTORC1 and mTORC2, respectively. MK-2206 was used to test the role of Akt in HDL-mediated cardiac protection. The expression levels and the activation states of mediators of mTORC1 and mTORC2 signaling and myocardial apoptosis were measured by immunoblotting and/or enzyme-linked immunosorbent assay (ELISA).

Results

HDL protected hearts from WKY and SHR against I/R injury as indicated by significant improvements in cardiac hemodynamics and reduction in infarct size. HDL induced greater protection in WKY compared to SHR. HDL treatment attenuated mTORC1 signaling in WKY by reducing the phosphorylation of P70S6K (mTORC1 substrate). In SHR however, HDL attenuated mTORC1 signaling by reducing the levels of phospho-mTORC1, Rag C (mTORC1 activator), and phospho-PRAS40 (mTORC1 inhibitor). HDL increased the phosphorylation of mTORC2 substrate Akt, specifically the Akt2 isoform in SHR and to a greater extent in WKY. HDL-induced protection was abolished in the presence of Akt antagonist and involved attenuation of GSK, caspases 7 and 8 activation, and cytochrome C release.

Conclusion

HDL mediates cardiac protection via attenuation of mTORC1, activation of mTORC2-Akt2, and inhibition of myocardial apoptosis. HDL regulates mTORC1 and mTORC2 signaling via distinct mechanisms in normotensive and hypertensive rats. HDL attenuation of mTORC1 and activation of mTORC2-Akt2 signaling could be a mechanism by which HDL protects against myocardial I/R injury in hypertension.

mTORC2: A neglected player in aging regulation

Mammalian target of rapamycin (mTOR) is a serine/threonine kinase that plays a pivotal role in various biological processes, through integrating external and internal signals, facilitating gene transcription and protein translation, as well as by regulating mitochondria and autophagy functions. mTOR kinase operates within two distinct protein complexes known as mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), which engage separate downstream signaling pathways impacting diverse cellular processes. Although mTORC1 has been extensively studied as a pro-proliferative factor and a pro-aging hub if activated aberrantly, mTORC2 received less attention, particularly regarding its implication in aging regulation. However, recent studies brought increasing evidence or clues for us, which implies the associations of mTORC2 with aging, as the genetic elimination of unique subunits of mTORC2, such as RICTOR, has been shown to alleviate aging progression in comparison to mTORC1 inhibition. In this review, we first summarized the basic characteristics of mTORC2, including its protein architecture and signaling network. We then focused on reviewing the molecular signaling regulation of mTORC2 in cellular senescence and organismal aging, and proposed the multifaceted regulatory characteristics under senescent and nonsenescent contexts. Next, we outlined the research progress of mTOR inhibitors in the field of antiaging and discussed future prospects and challenges. It is our pleasure if this review article could provide meaningful information for our readers and call forth more investigations working on this topic.

Veratridine, a plant-derived alkaloid, suppresses the hyperactive Rictor-mTORC2 pathway: a new targeted therapy for primary and metastatic colorectal cancer

Despite considerable advances to improve colorectal cancer (CRC) survival over the last decade, therapeutic challenges remain due to the rapid metastatic dissemination of primary tumors and screening limitations. Meanwhile, the rise of CRC in younger adults (Early-onset CRC), commonly diagnosed with a metastatic form of the disease, shows the pressing need to develop more effective targeted therapies to decrease the high mortality rates associated with metastatic disease. Hyperactivation of the Rictor-mTORC2-AKT signaling pathway drives key metastatic players in diverse malignant tumors, including early- and late-onset colorectal cancer. Selective mTORC2 inhibitors are becoming a potential treatment strategy for CRC due to the therapeutic limitations of mTORC1 inhibitors. Veratridine (VTD), a lipid-soluble alkaloid extracted from Liliaceae plants, can transcriptionally increase UBXN2A, which induces 26S proteasomal degradation of the Rictor protein, a key member in the mTORC2 complex. Destabilization of Rictor protein by VTD decreases Akt phosphorylation on Ser473, which is responsible for metastatic signaling downstream of the mTORC2 pathway in diverse malignant tumors. VTD decreases the population of metastatic colon cancer stem cells and functions as an angiogenesis inhibitor. VTD effectively reduces the spheroid growth rate and restricts cell migration. Live cell migration and invasion assays alongside biomechanical-force-based experiments revealed that VTD suppresses colon cancer cell invasiveness and the ensuing risk of tumor metastasis. A CRC mouse model that mimics the natural stages of human sporadic CRC revealed that VTD treatment significantly decreases tumor growth in a UBXN2A-dependent manner. This study showed a novel mechanistic connection between a ubiquitin-like protein and mTORC2-dependent migration and invasion in CRC tumors. This study revealed the therapeutic benefit of selective inhibition of Rictor in CRC, particularly in tumors with a hyperactive Rictor-mTORC2 signaling pathway. Finally, this study opened a new platform for repurposing VTD, a supplemental anti-hypertension molecule, into an effective targeted therapy in CRC tumors.

The Impact of Pdcd4, a Translation Inhibitor, on Drug Resistance

Programmed cell death 4 (Pdcd4) is a tumor suppressor, which has been demonstrated to efficiently suppress tumorigenesis. Biochemically, Pdcd4 binds with translation initiation factor 4A and represses protein translation. Beyond its role in tumor suppression, growing evidence suggests that Pdcd4 enhances the chemosensitivity of several anticancer drugs. To date, numerous translational targets of Pdcd4 have been identified. These targets govern important signal transduction pathways, and their attenuation may improve chemosensitivity or overcome drug resistance. This review will discuss the signal transduction pathways regulated by Pdcd4 and the potential mechanisms through which Pdcd4 enhances chemosensitivity or counteracts drug resistance.

Nup358 restricts ER-mitochondria connectivity by modulating mTORC2/Akt/GSK3β signalling

ER-mitochondria contact sites (ERMCSs) regulate processes, including calcium homoeostasis, energy metabolism and autophagy. Previously, it was shown that during growth factor signalling, mTORC2/Akt gets recruited to and stabilizes ERMCSs. Independent studies showed that GSK3β, a well-known Akt substrate, reduces ER-mitochondria connectivity by disrupting the VAPB-PTPIP51 tethering complex. However, the mechanisms that regulate ERMCSs are incompletely understood. Here we find that annulate lamellae (AL), relatively unexplored subdomains of ER enriched with a subset of nucleoporins, are present at ERMCSs. Depletion of Nup358, an AL-resident nucleoporin, results in enhanced mTORC2/Akt activation, GSK3β inhibition and increased ERMCSs. Depletion of Rictor, a mTORC2-specific subunit, or exogenous expression of GSK3β, was sufficient to reverse the ERMCS-phenotype in Nup358-deficient cells. We show that growth factor-mediated activation of mTORC2 requires the VAPB-PTPIP51 complex, whereas, Nup358's association with this tether restricts mTORC2/Akt signalling and ER-mitochondria connectivity. Expression of a Nup358 fragment that is sufficient for interaction with the VAPB-PTPIP51 complex suppresses mTORC2/Akt activation and disrupts ERMCSs. Collectively, our study uncovers a novel role for Nup358 in controlling ERMCSs by modulating the mTORC2/Akt/GSK3β axis.

A multiprotein signaling complex sustains AKT and mTOR/S6K activity necessary for the survival of cancer cells undergoing stress

The ability of cancer cells to survive microenvironmental stresses is critical for tumor progression and metastasis; however, how they survive these challenges is not fully understood. Here, we describe a novel multiprotein complex (DockTOR) essential for the survival of cancer cells under stress, triggered by the GTPase Cdc42 and a signaling partner Dock7, which includes AKT, mTOR, and the mTOR regulators TSC1, TSC2, and Rheb. DockTOR enables cancer cells to maintain a low but critical mTORC2-dependent phosphorylation of AKT during serum deprivation by preventing AKT dephosphorylation through an interaction between phospho-AKT and the Dock7 DHR1 domain. This activity stimulates a Raptor-independent but Rapamycin-sensitive mTOR/S6K activity necessary for survival. These findings address long-standing questions of how Cdc42 signals result in mTOR activation and demonstrate how cancer cells survive conditions when growth factor-dependent activation of mTORC1 is off. Determining how cancer cells survive stress conditions could identify vulnerabilities that lead to new therapeutic strategies.

The mTOR pathway controls phosphorylation of BRAF at T401

BRAF serves as a gatekeeper of the RAS/RAF/MEK/ERK pathway, which plays a crucial role in homeostasis. Since aberrant signalling of this axis contributes to cancer and other diseases, it is tightly regulated by crosstalk with the PI3K/AKT/mTOR pathway and ERK mediated feedback loops. For example, ERK limits BRAF signalling through phosphorylation of multiple residues. One of these, T401, is widely considered as an ERK substrate following acute pathway activation by growth factors. Here, we demonstrate that prominent T401 phosphorylation (pT401) of endogenous BRAF is already observed in the absence of acute stimulation in various cell lines of murine and human origin. Importantly, the BRAF/RAF1 inhibitor naporafenib, the MEK inhibitor trametinib and the ERK inhibitor ulixertinib failed to reduce pT401 levels in these settings, supporting an alternative ERK-independent pathway to T401 phosphorylation. In contrast, the mTOR inhibitor torin1 and the dual-specific PI3K/mTOR inhibitor dactolisib significantly suppressed pT401 levels in all investigated cell types, in both a time and concentration dependent manner. Conversely, genetic mTOR pathway activation by oncogenic RHEB (Q64L) and mTOR (S2215Y and R2505P) mutants substantially increased pT401, an effect that was reverted by dactolisib and torin1 but not by trametinib. We also show that shRNAmir mediated depletion of the mTORC1 complex subunit Raptor significantly enhanced the suppression of T401 phosphorylation by a low torin1 dose, while knockdown of the mTORC2 complex subunit Rictor was less effective. Using mass spectrometry, we provide further evidence that torin1 suppresses the phosphorylation of T401, S405 and S409 but not of other important regulatory phosphorylation sites such as S446, S729 and S750. In summary, our data identify the mTOR axis and its inhibitors of (pre)clinical relevance as novel modulators of BRAF phosphorylation at T401.

Inhibition of mTORC2 promotes natriuresis in Dahl salt-sensitive rats via the decrease of NCC and ENaC activity

We have previously observed that prolonged administration of rapamycin, an inhibitor targeting the mammalian target of rapamycin complex (mTORC)1, partially reduced hypertension and alleviated kidney inflammation in Dahl salt-sensitive (SS) rats. In contrast, treatment with PP242, an inhibitor affecting both mTORC1/mTORC2, not only completely prevented hypertension but also provided substantial protection against kidney injury. Notably, PP242 exhibited potent natriuretic effects that were not evident with rapamycin. The primary objective of this study was to pinpoint the specific tubular sites responsible for the natriuretic effect of PP242 in SS rats subjected to either 0.4% NaCl (normal salt) or 4.0% NaCl (high salt) diet. Acute effects of PP242 on natriuretic, diuretic, and kaliuretic responses were determined in unanesthetized SS rats utilizing benzamil, furosemide, or hydrochlorothiazide [inhibitors of epithelial Na+ channel (ENaC), Na-K-2Cl cotransporter (NKCC2), or Na-Cl cotransporter (NCC), respectively] either administered alone or in combination. The findings indicate that the natriuretic effects of PP242 in SS rats stem predominantly from the inhibition of NCC and a reduction of ENaC open probability. Molecular analysis revealed that mTORC2 regulates NCC activity through protein phosphorylation and ENaC activity through proteolytic cleavage in vivo. Evidence also indicated that PP242 also prevents the loss of K+ associated with the inhibition of NCC. These findings suggest that PP242 may represent an improved therapeutic approach for antihypertensive intervention, potentially controlling blood pressure and mitigating kidney injury in salt-sensitive human subjects.NEW & NOTEWORTHY This study explored mechanisms underlying the natriuretic effects of mammalian target of rapamycin protein complex 2 inhibition using PP242 and revealed both epithelial Na+ channel and Na-Cl cotransporter in the distal tubular segments were potentially inhibited. These observations, with prior lab evidence, indicate that PP242 prevents hypertension via its potent inhibitory effects on these specific sodium transporters and by reducing renal immune responses. This dual action, coupled with potassium sparing effects, suggests an improved approach for managing hypertension and associated kidney damage.

The molecular genetics of PI3K/PTEN/AKT/mTOR pathway in the malformations of cortical development

Malformations of cortical development (MCD) are a group of developmental disorders characterized by abnormal cortical structures caused by genetic or harmful environmental factors. Many kinds of MCD are caused by genetic variation. MCD is the common cause of intellectual disability and intractable epilepsy. With rapid advances in imaging and sequencing technologies, the diagnostic rate of MCD has been increasing, and many potential genes causing MCD have been successively identified. However, the high genetic heterogeneity of MCD makes it challenging to understand the molecular pathogenesis of MCD and to identify effective targeted drugs. Thus, in this review, we outline important events of cortical development. Then we illustrate the progress of molecular genetic studies about MCD focusing on the PI3K/PTEN/AKT/mTOR pathway. Finally, we briefly discuss the diagnostic methods, disease models, and therapeutic strategies for MCD. The information will facilitate further research on MCD. Understanding the role of the PI3K/PTEN/AKT/mTOR pathway in MCD could lead to a novel strategy for treating MCD-related diseases.

Pathophysiology in Brain Arteriovenous Malformations: Focus on Endothelial Dysfunctions and Endothelial-to-Mesenchymal Transition

Brain arteriovenous malformations (bAVMs) substantially increase the risk for intracerebral hemorrhage (ICH), which is associated with significant morbidity and mortality. However, the treatment options for bAVMs are severely limited, primarily relying on invasive methods that carry their own risks for intraoperative hemorrhage or even death. Currently, there are no pharmaceutical agents shown to treat this condition, primarily due to a poor understanding of bAVM pathophysiology. For the last decade, bAVM research has made significant advances, including the identification of novel genetic mutations and relevant signaling in bAVM development. However, bAVM pathophysiology is still largely unclear. Further investigation is required to understand the detailed cellular and molecular mechanisms involved, which will enable the development of safer and more effective treatment options. Endothelial cells (ECs), the cells that line the vascular lumen, are integral to the pathogenesis of bAVMs. Understanding the fundamental role of ECs in pathological conditions is crucial to unraveling bAVM pathophysiology. This review focuses on the current knowledge of bAVM-relevant signaling pathways and dysfunctions in ECs, particularly the endothelial-to-mesenchymal transition (EndMT).

The ability of microRNAs to regulate the immune response in ischemia/reperfusion inflammatory pathways

MicroRNAs play a crucial role in regulating the immune responses induced by ischemia/reperfusion injury. Through their ability to modulate gene expression, microRNAs adjust immune responses by targeting specific genes and signaling pathways. This review focuses on the impact of microRNAs on the inflammatory pathways triggered during ischemia/reperfusion injury and highlights their ability to modulate inflammation, playing a critical role in the pathophysiology of ischemia/reperfusion injury. Dysregulated expression of microRNAs contributes to the pathogenesis of ischemia/reperfusion injury, therefore targeting specific microRNAs offers an opportunity to restore immune homeostasis and improve patient outcomes. Understanding the complex network of immunoregulatory microRNAs could provide novel therapeutic interventions aimed at attenuating excessive inflammation and preserving tissue integrity.

Mapping the landscape: A bibliometric perspective on autophagy in spinal cord injury

BACKGROUND

Spinal cord injury (SCI) is a severe condition that often leads to persistent damage of nerve cells and motor dysfunction. Autophagy is an intracellular system that regulates the recycling and degradation of proteins and lipids, primarily through lysosomal-dependent organelle degradation. Numerous publications have highlighted the involvement of autophagy in the secondary injury of SCI. Therefore, gaining a comprehensive understanding of autophagy research is crucial for designing effective therapies for SCI.

METHODS

Dates were obtained from Web of Science, including articles and article reviews published from its inception to October 2023. VOSviewer, Citespace, and SCImago were used to visualized analysis. Bibliometric analysis was conducted using the Web of Science data, focusing on various categories such as publications, authors, journals, countries, organizations, and keywords. This analysis was aimed to summarize the knowledge map of autophagy and SCI.

RESULTS

From 2009 to 2023, the number of annual publications in this field exhibited wave-like growth, with the highest number of publications recorded in 2020 (44 publications). Our analysis identified Mei Xifan as the most prolific author, while Kanno H emerged as the most influential author based on co-citations. Neuroscience Letters was found to have published the largest number of papers in this field. China was the most productive country, contributing 232 publications, and Wenzhou Medical University was the most active organization, publishing 39 papers.

CONCLUSION

We demonstrated a comprehensive overview of the relationship between autophagy and SCI utilizing bibliometric tools. This article could help to enhance the understanding of the field about autophagy and SCI, foster collaboration among researchers and organizations, and identify potential therapeutic targets for treatment.

Low potassium activation of proximal mTOR/AKT signaling is mediated by Kir4.2

The renal epithelium is sensitive to changes in blood potassium (K+). We identify the basolateral K+ channel, Kir4.2, as a mediator of the proximal tubule response to K+ deficiency. Mice lacking Kir4.2 have a compensated baseline phenotype whereby they increase their distal transport burden to maintain homeostasis. Upon dietary K+ depletion, knockout animals decompensate as evidenced by increased urinary K+ excretion and development of a proximal renal tubular acidosis. Potassium wasting is not proximal in origin but is caused by higher ENaC activity and depends upon increased distal sodium delivery. Three-dimensional imaging reveals Kir4.2 knockouts fail to undergo proximal tubule expansion, while the distal convoluted tubule response is exaggerated. AKT signaling mediates the dietary K+ response, which is blunted in Kir4.2 knockouts. Lastly, we demonstrate in isolated tubules that AKT phosphorylation in response to low K+ depends upon mTORC2 activation by secondary changes in Cl- transport. Data support a proximal role for cell Cl- which, as it does along the distal nephron, responds to K+ changes to activate kinase signaling.

The Anthraquinone Derivative C2 Enhances Oxaliplatin-Induced Cell Death and Triggers Autophagy via the PI3K/AKT/mTOR Pathway

Chemotherapy resistance in cancer is an essential factor leading to high mortality rates. Tumor multidrug resistance arises as a result of the autophagy process. Our previous study found that compound 1-nitro-2 acyl anthraquinone-leucine (C2) exhibited excellent anti-colorectal cancer (CRC) activity involving autophagy and apoptosis-related proteins, whereas its underlying mechanism remains unclear. A notable aspect of this study is how C2 overcomes the multidrug susceptibility of HCT116/L-OHP, a colon cancer cell line that is resistant to both in vitro and in vivo oxaliplatin (trans-/-diaminocyclohexane oxalatoplatinum; L-OHP). In a xenograft tumor mouse model, we discovered that the mixture of C2 and L-OHP reversed the resistance of HCT116/L-OHP cells to L-OHP and inhibited tumor growth; furthermore, C2 down-regulated the gene expression levels of P-gp and BCRP and decreased P-gp's drug efflux activity. It is important to note that while C2 re-sensitized the HCT116/L-OHP cells to L-OHP for apoptosis, it also triggered a protective autophagic pathway. The expression levels of cleaved caspase-3 and Beclin 1 steadily rose. Expression of PI3K, phosphorylated AKT, and mTOR were decreased, while p53 increased. We demonstrated that the anthraquinone derivative C2 acts as an L-OHP sensitizer and reverses resistance to L-OHP in HCT116/L-OHP cells. It suggests that C2 can induce autophagy in HCT116/L-OHP cells by mediating p53 and the PI3K/AKT/mTOR signaling pathway.

Octanol alleviates chronic constriction injury of sciatic nerve-induced peripheral neuropathy by regulating AKT/mTOR signaling

OBJECTIVE

Activation of gap junction channels can induce neuropathic pain. Octanol can limit the conductance of gap junctions containing connexin 43 proteins. Thus, this study focused on the roles of octanol in chronic constriction injury (CCI)-induced peripheral neuropathy in mice and its mechanisms of action.

METHODS

Male mice were assigned into control, sham, CCI, CCI + Octanol-20 mg/kg, CCI + Octanol-40 mg/kg and CCI + Octanol-80 mg/kg groups. CCI was performed by applying three loose ligations to mouse sciatic nerve, and the mice with CCI was administered with 20 mg/kg, 40 mg/kg, or 80 mg/kg octanol. The neuropathic pain development was examined by assessing thermal withdrawal latency, paw withdrawal mechanical threshold, and sciatic functional index. Histopathological changes were evaluated by hematoxylin and eosin staining. The phosphorylation of protein kinase B (Akt) and mammalian target of rapamycin (mTOR) was examined by western blotting. The expression of Akt and mTOR was also evaluated by immunofluorescence staining.

RESULTS

Octanol alleviated the CCI-induced mechanical and thermal hyperalgesia and sciatic functional loss. Additionally, octanol relieved the CCI-induced abnormal histopathological changes. Mechanistically, octanol inactivated the Akt/mTOR pathway in the mice with CCI.

CONCLUSION

In conclusion, octanol can alleviate CCI-induced peripheral neuropathic by regulating the Akt/mTOR pathway and might be a novel pharmacological intervention for neuropathic pain.

Bile acid metabolism and signaling in health and disease: molecular mechanisms and therapeutic targets

Bile acids, once considered mere dietary surfactants, now emerge as critical modulators of macronutrient (lipid, carbohydrate, protein) metabolism and the systemic pro-inflammatory/anti-inflammatory balance. Bile acid metabolism and signaling pathways play a crucial role in protecting against, or if aberrant, inducing cardiometabolic, inflammatory, and neoplastic conditions, strongly influencing health and disease. No curative treatment exists for any bile acid influenced disease, while the most promising and well-developed bile acid therapeutic was recently rejected by the FDA. Here, we provide a bottom-up approach on bile acids, mechanistically explaining their biochemistry, physiology, and pharmacology at canonical and non-canonical receptors. Using this mechanistic model of bile acids, we explain how abnormal bile acid physiology drives disease pathogenesis, emphasizing how ceramide synthesis may serve as a unifying pathogenic feature for cardiometabolic diseases. We provide an in-depth summary on pre-existing bile acid receptor modulators, explain their shortcomings, and propose solutions for how they may be remedied. Lastly, we rationalize novel targets for further translational drug discovery and provide future perspectives. Rather than dismissing bile acid therapeutics due to recent setbacks, we believe that there is immense clinical potential and a high likelihood for the future success of bile acid therapeutics.

Dietary restriction and life-history trade-offs: insights into mTOR pathway regulation and reproductive investment in Japanese quail

Resources are needed for growth, reproduction and survival, and organisms must trade off limited resources among competing processes. Nutritional availability in organisms is sensed and monitored by nutrient-sensing pathways that can trigger physiological changes or alter gene expression. Previous studies have proposed that one such signalling pathway, the mechanistic target of rapamycin (mTOR), underpins a form of adaptive plasticity when individuals encounter constraints in their energy budget. Despite the fundamental importance of this process in evolutionary biology, how nutritional limitation is regulated through the expression of genes governing this pathway and its consequential effects on fitness remain understudied, particularly in birds. We used dietary restriction to simulate resource depletion and examined its effects on body mass, reproduction and gene expression in Japanese quails (Coturnix japonica). Quails were subjected to feeding at 20%, 30% and 40% restriction levels or ad libitum for 2 weeks. All restricted groups exhibited reduced body mass, whereas reductions in the number and mass of eggs were observed only under more severe restrictions. Additionally, dietary restriction led to decreased expression of mTOR and insulin-like growth factor 1 (IGF1), whereas the ribosomal protein S6 kinase 1 (RPS6K1) and autophagy-related genes (ATG9A and ATG5) were upregulated. The pattern in which mTOR responded to restriction was similar to that for body mass. Regardless of the treatment, proportionally higher reproductive investment was associated with individual variation in mTOR expression. These findings reveal the connection between dietary intake and the expression of mTOR and related genes in this pathway.

Simultaneous targeting of AMPK and mTOR is a novel therapeutic strategy against prostate cancer

Metastatic colonization by circulating cancer cells is a highly inefficient process. To colonize distant organs, disseminating cancer cells must overcome many obstacles in foreign microenvironments, and only a small fraction of them survives this process. How these disseminating cancer cells cope with stress and initiate metastatic process is not fully understood. In this study, we report that the metastatic onset of prostate cancer cells is associated with the dynamic conversion of metabolism signaling pathways governed by the energy sensors AMPK and mTOR. While in circulation in blood flow, the disseminating cancer cells display decreased mTOR and increased AMPK activities that protect them from stress-induced death. However, after metastatic onset, the mTOR-AMPK activities are reversed, enabling mTOR-dependent tumor growth. Suppression of this dynamic conversion by co-targeting of AMPK and mTOR signaling significantly suppresses prostate cancer cell and tumor organoid growth in vitro and experimental metastasis in vivo, suggesting that this can be a therapeutic approach against metastasizing prostate cancer.

mTOR signaling and Alzheimer's disease: What we know and where we are?

Despite the great body of research done on Alzheimer's disease, the underlying mechanisms have not been vividly investigated. To date, the accumulation of amyloid-beta plaques and tau tangles constitutes the hallmark of the disease; however, dysregulation of the mammalian target of rapamycin (mTOR) seems to be significantly involved in the pathogenesis of the disease as well. mTOR, as a serine-threonine protein kinase, was previously known for controlling many cellular functions such as cell size, autophagy, and metabolism. In this regard, mammalian target of rapamycin complex 1 (mTORC1) may leave anti-aging impacts by robustly inhibiting autophagy, a mechanism that inhibits the accumulation of damaged protein aggregate and dysfunctional organelles. Formation and aggregation of neurofibrillary tangles and amyloid-beta plaques seem to be significantly regulated by mTOR signaling. Understanding the underlying mechanisms and connection between mTOR signaling and AD may suggest conducting clinical trials assessing the efficacy of rapamycin, as an mTOR inhibitor drug, in managing AD or may help develop other medications. In this literature review, we aim to elaborate mTOR signaling network mainly in the brain, point to gaps of knowledge, and define how and in which ways mTOR signaling can be connected with AD pathogenesis and symptoms.

PIK3CA mutation as an acquired resistance driver to EGFR-TKIs in non-small cell lung cancer: Clinical challenges and opportunities

Epithelial growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have significantly enhanced the treatment outcomes in non-small cell lung cancer (NSCLC) patients harboring EGFR mutations. However, the occurrence of acquired resistance to EGFR-TKIs is an unavoidable outcome observed in these patients. Disruption of the PI3K/AKT/mTOR signaling pathway can contribute to the emergence of resistance to EGFR TKIs in lung cancer. The emergence of PIK3CA mutations following treatment with EGFR-TKIs can lead to resistance against EGFR-TKIs. This review provides an overview of the current perspectives regarding the involvement of PI3K/AKT/mTOR signaling in the development of lung cancer. Furthermore, we outline the state-of-the-art therapeutic strategies targeting the PI3K/AKT/mTOR signaling pathway in lung cancer. We highlight the role of PIK3CA mutation as an acquired resistance mechanism against EGFR-TKIs in EGFR-mutant NSCLC. Crucially, we explore therapeutic strategies targeting PIK3CA-mediated resistance to EGFR TKIs in lung cancer, aiming to optimize the effectiveness of treatment.

Regulation of ferroptosis by PI3K/Akt signaling pathway: a promising therapeutic axis in cancer

The global challenge posed by cancer, marked by rising incidence and mortality rates, underscores the urgency for innovative therapeutic approaches. The PI3K/Akt signaling pathway, frequently amplified in various cancers, is central in regulating essential cellular processes. Its dysregulation, often stemming from genetic mutations, significantly contributes to cancer initiation, progression, and resistance to therapy. Concurrently, ferroptosis, a recently discovered form of regulated cell death characterized by iron-dependent processes and lipid reactive oxygen species buildup, holds implications for diseases, including cancer. Exploring the interplay between the dysregulated PI3K/Akt pathway and ferroptosis unveils potential insights into the molecular mechanisms driving or inhibiting ferroptotic processes in cancer cells. Evidence suggests that inhibiting the PI3K/Akt pathway may sensitize cancer cells to ferroptosis induction, offering a promising strategy to overcome drug resistance. This review aims to provide a comprehensive exploration of this interplay, shedding light on the potential for disrupting the PI3K/Akt pathway to enhance ferroptosis as an alternative route for inducing cell death and improving cancer treatment outcomes.

Unexpected roles for AMPK in the suppression of autophagy and the reactivation of mTORC1 signaling during prolonged amino acid deprivation

AMPK promotes catabolic and suppresses anabolic cell metabolism to promote cell survival during energetic stress, in part by inhibiting mTORC1, an anabolic kinase requiring sufficient levels of amino acids. We found that cells lacking AMPK displayed increased apoptotic cell death during nutrient stress caused by prolonged amino acid deprivation. We presumed that impaired autophagy explained this phenotype, as a prevailing view posits that AMPK initiates autophagy (often a pro-survival response) through phosphorylation of ULK1. Unexpectedly, however, autophagy remained unimpaired in cells lacking AMPK, as monitored by several autophagic readouts in several cell lines. More surprisingly, the absence of AMPK increased ULK1 signaling and LC3b lipidation during amino acid deprivation while AMPK-mediated phosphorylation of ULK1 S555 (a site proposed to initiate autophagy) decreased upon amino acid withdrawal or pharmacological mTORC1 inhibition. In addition, activation of AMPK with compound 991, glucose deprivation, or AICAR blunted autophagy induced by amino acid withdrawal. These results demonstrate that AMPK activation and glucose deprivation suppress autophagy. As AMPK controlled autophagy in an unexpected direction, we examined how AMPK controls mTORC1 signaling. Paradoxically, we observed impaired reactivation of mTORC1 in cells lacking AMPK upon prolonged amino acid deprivation. Together these results oppose established views that AMPK promotes autophagy and inhibits mTORC1 universally. Moreover, they reveal unexpected roles for AMPK in the suppression of autophagy and the support of mTORC1 signaling in the context of prolonged amino acid deprivation. These findings prompt a reevaluation of how AMPK and its control of autophagy and mTORC1 impact health and disease.

mTOR hyperactivity and RICTOR amplification as targets for personalized treatments in malignancies

The increasing knowledge of molecular alterations in malignancies, including mutations and regulatory failures in the mTOR (mechanistic target of rapamycin) signaling pathway, highlights the importance of mTOR hyperactivity as a validated target in common and rare malignancies. This review summarises recent findings on the characterization and prognostic role of mTOR kinase complexes (mTORC1 and mTORC2) activity regarding differences in their function, structure, regulatory mechanisms, and inhibitor sensitivity. We have recently identified new tumor types with RICTOR (rapamycin-insensitive companion of mTOR) amplification and associated mTORC2 hyperactivity as useful potential targets for developing targeted therapies in lung cancer and other newly described malignancies. The activity of mTOR complexes is recommended to be assessed and considered in cancers before mTOR inhibitor therapy, as current first-generation mTOR inhibitors (rapamycin and analogs) can be ineffective in the presence of mTORC2 hyperactivity. We have introduced and proposed a marker panel to determine tissue characteristics of mTOR activity in biopsy specimens, patient materials, and cell lines. Ongoing phase trials of new inhibitors and combination therapies are promising in advanced-stage patients selected by genetic alterations, molecular markers, and/or protein expression changes in the mTOR signaling pathway. Hopefully, the summarized results, our findings, and the suggested characterization of mTOR activity will support therapeutic decisions.

Perfluorooctane sulfonate (PFOS) induces apoptosis and autophagy by inhibition of PI3K/AKT/mTOR pathway in human granulosa cell line KGN

Perfluorooctane sulfonate (PFOS) is recognized as an environmental endocrine disruptor with widespread use in industrial manufacturing and daily life, contributing to various public health concerns. However, the precise impacts of PFOS on the ovary and its regulatory mechanisms remain unclear. This study aims to delineate the ovarian toxicity of PFOS and scrutinize its effects on apoptosis and autophagy through modulation of the PI3K/AKT/mTOR pathway in the human granulosa cell line (KGN). Cell viability, assessed via the Cell Counting Kit-8 (CCK8), revealed a dose-dependent reduction in cell viability upon PFOS exposure. Flow cytometry analysis demonstrated an elevated proportion of apoptotic cells following PFOS treatment. Western blot analyses unveiled increased expression of Bax, Cyt c, cleaved caspase-9, and LC3-II/I, coupled with decreased expression of Bcl-2 and p62. Transmission electron microscopy (TEM) observations illustrated a heightened number of autophagosomes induced by PFOS. Molecular docking investigations, in conjunction with Western blot experiments, substantiated PFOS's significant inhibition of the PI3K/AKT/mTOR signaling pathway. These findings collectively underscore that PFOS induces apoptosis and autophagy in KGN cells through modulation of the PI3K/AKT/mTOR pathway, providing experimental evidence for PFOS-induced ovarian toxicity and elucidating the underlying regulatory mechanisms in KGN cells.

Manganese induces neuronal apoptosis by activating mTOR signaling pathway in vitro and in vivo

Manganese (Mn) is a well-known environmental pollutant and occupational toxicant that causes neurotoxicity, which present as neurodegenerative-like symptoms. However, the mechanism of Mn-induced neuronal injury remains unclear. In this research, we explored the mechanism of Mn-induced neurotoxicity, focusing on the mTOR signaling pathway. A plasmid expressing a short hairpin RNA (shRNA) targeting mTOR (shRNA-mTOR) was transfected into N27 cells in vitro, and rapamycin was used as an mTOR inhibitor in vivo to block the mTOR signaling pathway. Cells were treated with different concentrations of manganese (II) chloride (MnCl2). We found that Mn induced cell injury and apoptosis and markedly upregulated the expression of mTOR pathway-related proteins. The phosphorylation of 4E-BP1, S6K1, Akt and SGK1 was markedly decreased after blocking mTOR, and cell apoptosis was also reduced. Furthermore, the mTOR-specific inhibitor rapamycin restored learning and memory abilities in vivo. This research highlights that inhibiting mTOR might be useful for preventing Mn-induced neurodegenerative-like disorders.

Discrete Mechanistic Target of Rapamycin Signaling Pathways, Stem Cells, and Therapeutic Targets

The mechanistic target of rapamycin (mTOR) is a serine/threonine kinase that functions via its discrete binding partners to form two multiprotein complexes, mTOR complex 1 and 2 (mTORC1 and mTORC2). Rapamycin-sensitive mTORC1, which regulates protein synthesis and cell growth, is tightly controlled by PI3K/Akt and is nutrient-/growth factor-sensitive. In the brain, mTORC1 is also sensitive to neurotransmitter signaling. mTORC2, which is modulated by growth factor signaling, is associated with ribosomes and is insensitive to rapamycin. mTOR regulates stem cell and cancer stem cell characteristics. Aberrant Akt/mTOR activation is involved in multistep tumorigenesis in a variety of cancers, thereby suggesting that the inhibition of mTOR may have therapeutic potential. Rapamycin and its analogues, known as rapalogues, suppress mTOR activity through an allosteric mechanism that only suppresses mTORC1, albeit incompletely. ATP-catalytic binding site inhibitors are designed to inhibit both complexes. This review describes the regulation of mTOR and the targeting of its complexes in the treatment of cancers, such as glioblastoma, and their stem cells.

mTOR Signaling: Recent Progress

In the intricate landscape of human biology, the mechanistic target of rapamycin (mTOR) emerges as a key regulator, orchestrating a vast array of processes in health and disease [...].

The Role of mTOR in Doxorubicin-Altered Cardiac Metabolism: A Promising Therapeutic Target of Natural Compounds

Doxorubicin (DOX) is commonly used for the treatment of various types of cancer, however can cause serious side effects, including cardiotoxicity. The mechanisms involved in DOX-induced cardiac damage are complex and not yet fully understood. One mechanism is the disruption of cardiac metabolism, which can impair cardiac function. The mammalian target of rapamycin (mTOR) is a key regulator of cardiac energy metabolism, and dysregulation of mTOR signaling has been implicated in DOX-induced cardiac dysfunction. Natural compounds (NCs) have been shown to improve cardiac function in vivo and in vitro models of DOX-induced cardiotoxicity. This review article explores the protective effects of NCs against DOX-induced cardiac injury, with a focus on their regulation of mTOR signaling pathways. Generally, the modulation of mTOR signaling by NCs represents a promising strategy for decreasing the cardiotoxic effects of DOX.

Rictor-A Mediator of Progression and Metastasis in Lung Cancer

Lung carcinoma is one of the most common cancer types for both men and women. Despite recent breakthroughs in targeted therapy and immunotherapy, it is characterized by a high metastatic rate, which can significantly affect quality of life and prognosis. Rictor (encoded by the RICTOR gene) is known as a scaffold protein for the multiprotein complex mTORC2. Among its diverse roles in regulating essential cellular functions, mTORC2 also facilitates epithelial-mesenchymal transition and metastasis formation. Amplification of the RICTOR gene and subsequent overexpression of the Rictor protein can result in the activation of mTORC2, which promotes cell survival and migration. Based on recent studies, RICTOR amplification or Rictor overexpression can serve as a marker for mTORC2 activation, which in turn provides a promising druggable target. Although selective inhibitors of Rictor and the Rictor-mTOR association are only in a preclinical phase, they seem to be potent novel approaches to reduce tumor cell migration and metastasis formation. Here, we summarize recent advances that support an important role for Rictor and mTORC2 as potential therapeutic targets in the treatment of lung cancer. This is a traditional (narrative) review based on Pubmed and Google Scholar searches for the following keywords: Rictor, RICTOR amplification, mTORC2, Rictor complexes, lung cancer, metastasis, progression, mTOR inhibitors.

Extracellular Matrix Cues Regulate Mechanosensing and Mechanotransduction of Cancer Cells

Extracellular biophysical properties have particular implications for a wide spectrum of cellular behaviors and functions, including growth, motility, differentiation, apoptosis, gene expression, cell-matrix and cell-cell adhesion, and signal transduction including mechanotransduction. Cells not only react to unambiguously mechanical cues from the extracellular matrix (ECM), but can occasionally manipulate the mechanical features of the matrix in parallel with biological characteristics, thus interfering with downstream matrix-based cues in both physiological and pathological processes. Bidirectional interactions between cells and (bio)materials in vitro can alter cell phenotype and mechanotransduction, as well as ECM structure, intentionally or unintentionally. Interactions between cell and matrix mechanics in vivo are of particular importance in a variety of diseases, including primarily cancer. Stiffness values between normal and cancerous tissue can range between 500 Pa (soft) and 48 kPa (stiff), respectively. Even the shear flow can increase from 0.1-1 dyn/cm2 (normal tissue) to 1-10 dyn/cm2 (cancerous tissue). There are currently many new areas of activity in tumor research on various biological length scales, which are highlighted in this review. Moreover, the complexity of interactions between ECM and cancer cells is reduced to common features of different tumors and the characteristics are highlighted to identify the main pathways of interaction. This all contributes to the standardization of mechanotransduction models and approaches, which, ultimately, increases the understanding of the complex interaction. Finally, both the in vitro and in vivo effects of this mechanics-biology pairing have key insights and implications for clinical practice in tumor treatment and, consequently, clinical translation.

Development and Clinical Applications of PI3K/AKT/mTOR Pathway Inhibitors as a Therapeutic Option for Leukemias

Leukemias are hematological neoplasms characterized by dysregulations in several cellular signaling pathways, prominently including the PI3K/AKT/mTOR pathway. Since this pathway is associated with several important cellular mechanisms, such as proliferation, metabolism, survival, and cell death, its hyperactivation significantly contributes to the development of leukemias. In addition, it is a crucial prognostic factor, often correlated with therapeutic resistance. Changes in the PI3K/AKT/mTOR pathway are identified in more than 50% of cases of acute leukemia, especially in myeloid lineages. Furthermore, these changes are highly frequent in cases of chronic lymphocytic leukemia, especially those with a B cell phenotype, due to the correlation between the hyperactivation of B cell receptors and the abnormal activation of PI3Kδ. Thus, the search for new therapies that inhibit the activity of the PI3K/AKT/mTOR pathway has become the objective of several clinical studies that aim to replace conventional oncological treatments that have high rates of toxicities and low specificity with target-specific therapies offering improved patient quality of life. In this review we describe the PI3K/AKT/mTOR signal transduction pathway and its implications in leukemogenesis. Furthermore, we provide an overview of clinical trials that employed PI3K/AKT/mTOR inhibitors either as monotherapy or in combination with other cytotoxic agents for treating patients with various types of leukemias. The varying degrees of treatment efficacy are also reported.

Ablation of Long Noncoding RNA Hoxb3os Exacerbates Cystogenesis in Mouse Polycystic Kidney Disease

SIGNIFICANCE STATEMENT

Long noncoding RNAs (lncRNAs) are a class of nonprotein coding RNAs with pivotal functions in development and disease. They have emerged as an exciting new drug target category for many common conditions. However, the role of lncRNAs in autosomal dominant polycystic kidney disease (ADPKD) has been understudied. This study provides evidence implicating a lncRNA in the pathogenesis of ADPKD. We report that Hoxb3os is downregulated in ADPKD and regulates mammalian target of rapamycin (mTOR)/Akt pathway in the in vivo mouse kidney. Ablating the expression of Hoxb3os in mouse polycystic kidney disease (PKD) activated mTOR complex 2 (mTORC2) signaling and exacerbated the cystic phenotype. The results from our study provide genetic proof of concept for future studies that focus on targeting lncRNAs as a treatment option in PKD.

BACKGROUND

ADPKD is a monogenic disorder characterized by the formation of kidney cysts and is primarily caused by mutations in two genes, PKD1 and PKD2 .

METHODS

In this study, we investigated the role of lncRNA Hoxb3os in ADPKD by ablating its expression in the mouse.

RESULTS

Hoxb3os -null mice were viable and had grossly normal kidney morphology but displayed activation of mTOR/Akt signaling and subsequent increase in kidney cell proliferation. To determine the role of Hoxb3os in cystogenesis, we crossed the Hoxb3os -null mouse to two orthologous Pkd1 mouse models: Pkhd1/Cre; Pkd1F/F (rapid cyst progression) and Pkd1RC/RC (slow cyst progression). Ablation of Hoxb3os exacerbated cyst growth in both models. To gain insight into the mechanism whereby Hoxb3os inhibition promotes cystogenesis, we performed western blot analysis of mTOR/Akt pathway between Pkd1 single-knockout and Pkd1 - Hoxb3os double-knockout (DKO) mice. Compared with single-knockout, DKO mice presented with enhanced levels of total and phosphorylated Rictor. This was accompanied by increased phosphorylation of Akt at Ser 473 , a known mTORC2 effector site. Physiologically, kidneys from DKO mice displayed between 50% and 60% increase in cell proliferation and cyst number.

CONCLUSIONS

The results from this study indicate that ablation of Hoxb3os in mouse PKD exacerbates cystogenesis and dysregulates mTORC2.

NUAK1 coordinates growth factor-dependent activation of mTORC2 and Akt signaling

BACKGROUND

mTORC2 is a critical regulator of cytoskeleton organization, cell proliferation, and cancer cell survival. Activated mTORC2 induces maximal activation of Akt by phosphorylation of Ser-473, but regulation of Akt activity and signaling crosstalk upon growth factor stimulation are still unclear.

RESULTS

We identified that NUAK1 regulates growth factor-dependent activation of Akt by two mechanisms. NUAK1 interacts with mTORC2 components and regulates mTORC2-dependent activation of Akt by controlling lysosome positioning and mTOR association with this organelle. A second mechanism involves NUAK1 directly phosphorylating Akt at Ser-473. The effect of NUAK1 correlated with a growth factor-dependent activation of specific Akt substrates. NUAK1 induced the Akt-dependent phosphorylation of FOXO1/3a (Thr-24/Thr-32) but not of TSC2 (Thr-1462). According to a subcellular compartmentalization that could explain NUAK1's differential effect on the Akt substrates, we found that NUAK1 is associated with early endosomes but not with plasma membrane, late endosomes, or lysosomes. NUAK1 was required for the Akt/FOXO1/3a axis, regulating p21CIP1, p27KIP1, and FoxM1 expression and cancer cell survival upon EGFR stimulation. Pharmacological inhibition of NUAK1 potentiated the cell death effect induced by Akt or mTOR pharmacological blockage. Analysis of human tissue data revealed that NUAK1 expression positively correlates with EGFR expression and Akt Ser-473 phosphorylation in several human cancers.

CONCLUSIONS

Our results showed that NUAK1 kinase controls mTOR subcellular localization and induces Akt phosphorylation, demonstrating that NUAK1 regulates the growth factor-dependent activation of Akt signaling. Therefore, targeting NUAK1, or co-targeting it with Akt or mTOR inhibitors, may be effective in cancers with hyperactivated Akt signaling.

FilGAP regulates tumor growth in Glioma through the regulation of mTORC1 and mTORC2

The mechanistic target of rapamycin (mTOR) is a serine/threonine protein kinase that forms the two different protein complexes, known as mTORC1 and mTORC2. mTOR signaling is activated in a variety of tumors, including glioma that is one of the malignant brain tumors. FilGAP (ARHGAP24) is a negative regulator of Rac, a member of Rho family small GTPases. In this study, we found that FilGAP interacts with mTORC1/2 and is involved in tumor formation in glioma. FilGAP interacted with mTORC1 via Raptor and with mTORC2 via Rictor and Sin1. Depletion of FilGAP in KINGS-1 glioma cells decreased phosphorylation of S6K and AKT. Furthermore, overexpression of FilGAP increased phosphorylation of S6K and AKT, suggesting that FilGAP activates mTORC1/2. U-87MG, glioblastoma cells, showed higher mTOR activity than KINGS-1, and phosphorylation of S6K and AKT was not affected by suppression of FilGAP expression. However, in the presence of PI3K inhibitors, phosphorylation of S6K and AKT was also decreased in U-87MG by depletion of FilGAP, suggesting that FilGAP may also regulate mTORC2 in U-87MG. Finally, we showed that depletion of FilGAP in KINGS-1 and U-87MG cells significantly reduced spheroid growth. These results suggest that FilGAP may contribute to tumor growth in glioma by regulating mTORC1/2 activities.

Growth or death? Control of cell destiny by mTOR and autophagy pathways

One of the central regulators of cell growth, proliferation, and metabolism is the mammalian target of rapamycin, mTOR, which exists in two structurally and functionally different complexes: mTORC1 and mTORC2; unlike m TORC2, mTORC1 is activated in response to the sufficiency of nutrients and is inhibited by rapamycin. mTOR complexes have critical roles not only in protein synthesis, gene transcription regulation, proliferation, tumor metabolism, but also in the regulation of the programmed cell death mechanisms such as autophagy and apoptosis. Autophagy is a conserved catabolic mechanism in which damaged molecules are recycled in response to nutrient starvation. Emerging evidence indicates that the mTOR signaling pathway is frequently activated in tumors. In addition, dysregulation of autophagy was associated with the development of a variety of human diseases, such as cancer and aging. Since mTOR can inhibit the induction of the autophagic process from the early stages of autophagosome formation to the late stage of lysosome degradation, the use of mTOR inhibitors to regulate autophagy could be considered a potential therapeutic option. The present review sheds light on the mTOR and autophagy signaling pathways and the mechanisms of regulation of mTOR-autophagy.