TSC2 integrates Wnt and energy signals via a coordinated phosphorylation by AMPK and GSK3 to regulate cell growth

Deciphering the Mechanistic Impact of Acupuncture on the Neurovascular Unit in Acute Ischemic Stroke: Insights From Basic Research in a Narrative Review

Ischemic stroke(IS), a severe acute cerebrovascular disease, not only imposes a heavy economic burden on society but also presents numerous challenges in treatment. During the acute phase, while thrombolysis and thrombectomy serve as primary treatments, these approaches are restricted by a narrow therapeutic window. During rehabilitation, commonly used neuroprotective agents struggle with their low drug delivery efficiency and inadequate preclinical testing, and the long-term pharmacological and toxicity effects of nanomedicines remain undefined. Meanwhile, acupuncture as a therapeutic approach is widely acknowledged for its effectiveness in treating IS and has been recommended by the World Health Organization (WHO) as an alternative and complementary therapy, even though its exact mechanisms remain unclear. This review aims to summarize the known mechanisms of acupuncture and electroacupuncture (EA) in the treatment of IS. Research shows that acupuncture treatment mainly protects the neurovascular unit through five mechanisms: 1) reducing neuronal apoptosis and promoting neuronal repair and proliferation; 2) maintaining the integrity of the blood-brain barrier (BBB); 3) inhibiting the overactivation and polarization imbalance of microglia; 4) regulating the movement of vascular smooth muscle (VSM) cells; 5) promoting the proliferation of oligodendrocyte precursors. Through an in-depth analysis, this review reveals the multi-level, multi-dimensional impact of acupuncture treatment on the neurovascular unit (NVU) following IS, providing stronger evidence and a theoretical basis for its clinical application.

Fat body glycolysis defects inhibit mTOR and promote distant muscle disorganization through TNF-α/egr and ImpL2 signaling in Drosophila larvae

The fat body in Drosophila larvae functions as a reserve tissue and participates in the regulation of organismal growth and homeostasis through its endocrine activity. To better understand its role in growth coordination, we induced fat body atrophy by knocking down several key enzymes of the glycolytic pathway in adipose cells. Our results show that impairing the last steps of glycolysis leads to a drastic drop in adipose cell size and lipid droplet content, and downregulation of the mTOR pathway and REPTOR transcriptional activity. Strikingly, fat body atrophy results in the distant disorganization of body wall muscles and the release of muscle-specific proteins in the hemolymph. Furthermore, we showed that REPTOR activity is required for fat body atrophy downstream of glycolysis inhibition, and that the effect of fat body atrophy on muscles depends on the production of TNF-α/egr and of the insulin pathway inhibitor ImpL2.

Wnt3a-induced LRP6 phosphorylation enhances osteoblast differentiation to alleviate osteoporosis through activation of mTORC1/β-catenin signaling

OBJECTIVE

Osteoporosis (OP) is a common cause of morbidity and mortality in older individuals. The importance of Wnt3a in osteogenic activity and bone tissue homeostasis is well known. Here, we explored the possible molecular mechanism by which Wnt3a mediates the LRP6/mTORC1/β-catenin axis to regulate osteoblast differentiation in OP.

METHODS

OP-related key genes were identified through a bioinformatics analysis. A ROS17/2.8 cell differentiation system for rat osteogenic progenitors and a rat model of senile OP were constructed for in vitro and in vivo mechanism verification.

RESULTS

Bioinformatics analysis revealed that LRP6 was poorly expressed in OP and may play a key role in the occurrence of OP by affecting osteoblast differentiation. LRP6 knockdown inhibited osteoblast differentiation in an in vitro model. In addition, Wnt3a promoted osteoblast differentiation by inducing LRP6 phosphorylation. Moreover, LRP6 promoted mTORC1 expression, which indirectly promoted β-catenin expression, thus promoting osteoblast differentiation. Finally, an in vivo assay revealed that LRP6 inhibition improved OP.

CONCLUSION

Our study provides evidence that Wnt3a induces phosphorylation of LRP6 to activate the mTORC1/β-catenin axis, thus promoting osteoblast differentiation and ultimately improving OP in aged rats.

AKT-mediated phosphorylation of TSC2 controls stimulus- and tissue-specific mTORC1 signaling and organ growth

Mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) integrates diverse intracellular and extracellular growth signals to regulate cell and tissue growth. How the molecular mechanisms regulating mTORC1 signaling established through biochemical and cell biological studies function under physiological states in specific mammalian tissues are unknown. Here, we characterize a genetic mouse model lacking the 5 phosphorylation sites on the tuberous sclerosis complex 2 (TSC2) protein through which the growth factor-stimulated protein kinase AKT can active mTORC1 signaling in cell culture models. These phospho-mutant mice (TSC2-5A) are developmentally normal but exhibit reduced body weight and the weight of specific organs, such as brain and skeletal muscle, associated with cell intrinsic decreases in growth factor-stimulated mTORC1 signaling. The TSC2-5A mouse model demonstrates that TSC2 phosphorylation is a primary mechanism of mTORC1 activation in some, but not all, tissues and provides a genetic tool to facilitate studies on the physiological regulation of mTORC1.

β-hydroxybutyrate recapitulates the beneficial effects of ketogenic metabolic therapy in polycystic kidney disease

Autosomal-dominant polycystic kidney disease (ADPKD) is a common monogenic disease characterized by the formation of fluid-filled renal cysts, loss of mitochondrial function, decreased fatty acid oxidation, increased glycolysis, and likely renal failure. We previously demonstrated that inducing a state of ketosis ameliorates or reverses PKD progression in multiple animal models. In this study, we compare time-restricted feeding and 48-h periodic fasting regimens in both juvenile and adult Cy/+ rats. Both fasting regimens potently prevent juvenile disease progression and partially reverse PKD in adults. To explore the mechanism of fasting, we administered β-hydroxybutyrate (BHB) to Cy/+ rats and orthologous mouse models of PKD (Pkd1 RC/RC , Pkd1-Ksp:Cre). BHB recapitulated the effects of fasting in these models independent of stereoisomer, suggesting the effects of BHB are largely due to its signaling functions. These findings implicate the use of ketogenic metabolic therapy and BHB supplementation as potential disease modifiers of PKD and point toward underlying mechanisms.

The convergence of mTOR signaling and ethanol teratogenesis

Ethanol is one of the most common teratogens and causes of human developmental disabilities. Fetal alcohol spectrum disorders (FASD), which describes the wide range of deficits due to prenatal ethanol exposure, are estimated to affect between 1.1 % and 5.0 % of births in the United States. Ethanol dysregulates numerous cellular mechanisms such as programmed cell death (apoptosis), protein synthesis, autophagy, and various aspects of cell signaling, all of which contribute to FASD. The mechanistic target of rapamycin (mTOR) regulates these cellular mechanisms via sensing of nutrients like amino acids and glucose, DNA damage, and growth factor signaling. Despite an extensive literature on ethanol teratogenesis and mTOR signaling, there has been less attention paid to their interaction. Here, we discuss the impact of ethanol teratogenesis on mTORC1's ability to coordinate growth factor and amino acid sensing with protein synthesis, autophagy, and apoptosis. Notably, the effect of ethanol exposure on mTOR signaling depends on the timing and dose of ethanol as well as the system studied. Overall, the overlap between the functions of mTORC1 and the phenotypes observed in FASD suggest a mechanistic interaction. However, more work is required to fully understand the impact of ethanol teratogenesis on mTOR signaling.

Mechanistic Target of Rapamycin Kinase is a Common Convergent Pathway to Renal Neoplasia: A Contemporary Review

Mechanistic target of rapamycin kinase (mTOR) is a member of the phosphatidylinositol-3-hydroxide kinase (PI3 K)-related protein kinase family that functions as a central regulator of cell growth, metabolism, proliferation, and survival. The role of the TSC-mTOR signaling pathway in kidney tumors has been implicated in some hamartoma syndromes; however, with the advent and wide utilization of molecular studies, a growing number of kidney tumors have been linked to somatic or germline mutations involving genes that encode for this pathway, including eosinophilic solid and cystic renal cell carcinoma, low-grade oncocytic tumor, eosinophilic vacuolated tumor, renal cell carcinoma with fibromyomatous stroma and angiomyolipoma, among others. Herein, we review the contemporary developments of mTOR pathway-related renal neoplasia, focusing on the clinicopathologic features of the tumor entities.

The treatment landscape of triple-negative breast cancer

Triple-negative breast cancer (TNBC) tumors are biologically aggressive breast cancer. On the molecular level, TNBC is a highly heterogeneous disease; more biotechnologies are gradually being used to advance the understanding of TNBC subtypes and help establish more targeted therapies. Multiple TNBC target-related agents are already approved by the Food and Drug Administration for clinical use, including PI3K/AKT/mTOR inhibitors, PRAP inhibitors, and antibody-drug conjugates. Some innovative approaches, like peptide strategies, also promise to treat TNBC. Currently, the interplay between TNBC tumors and their tumor microenvironment provides a promising prospect for improving the efficacy of immunotherapy. In this review, we summarize the prevalent TNBC subtype methodologies, discuss the evolving therapeutic strategies, and propose new therapeutic possibilities based on existing foundational theories, with the attempt to serve as a reference to further advance tailoring treatment of TNBC.

Nutrient Sensing of mTORC1 signaling in cancer and aging

The mechanistic target of rapamycin complex 1 (mTORC1) is indispensable for preserving cellular and organismal homeostasis by balancing the anabolic and catabolic processes in response to various environmental cues, such as nutrients, growth factors, energy status, oxygen levels, and stress. Dysregulation of mTORC1 signaling is associated with the progression of many types of human disorders including cancer, age-related diseases, neurodegenerative disorders, and metabolic diseases. The way mTORC1 senses various upstream signals and converts them into specific downstream responses remains a crucial question with significant impacts for our perception of the related physiological and pathological process. In this review, we discuss the recent molecular and functional insights into the nutrient sensing of the mTORC1 signaling pathway, along with the emerging role of deregulating nutrient-mTORC1 signaling in cancer and age-related disorders.

Boolean Modeling of Biological Network Applied to Protein-Protein Interaction Network of Autism Patients

Cellular molecules interact with one another in a structured manner, defining a regulatory network topology that describes cellular mechanisms. Genetic mutations alter these networks' pathways, generating complex disorders such as autism spectrum disorder (ASD). Boolean models have assisted in understanding biological system dynamics since Kauffman's 1969 discovery, and various analytical tools for regulatory networks have been developed. This study examined the protein-protein interaction network created in our previous publication of four ASD patients using the SPIDDOR R package, a Boolean model-based method. The aim is to examine how patients' genetic variations in INTS6L, USP9X, RSK4, FGF5, FLNA, SUMF1, and IDS affect mTOR and Wnt cell signaling convergence. The Boolean network analysis revealed abnormal activation levels of essential proteins such as β-catenin, MTORC1, RPS6, eIF4E, Cadherin, and SMAD. These proteins affect gene expression, translation, cell adhesion, shape, and migration. Patients 1 and 2 showed consistent patterns of increased β-catenin activity and decreased MTORC1, RPS6, and eIF4E activity. However, patient 2 had an independent decrease in Cadherin and SMAD activity due to the FLNA mutation. Patients 3 and 4 have an abnormal activation of the mTOR pathway, which includes the MTORC1, RPS6, and eIF4E genes. The shared mTOR pathway behavior in these patients is explained by a shared mutation in two closely related proteins (SUMF1 and IDS). Diverse activities in β-catenin, MTORC1, RPS6, eIF4E, Cadherin, and SMAD contributed to the reported phenotype in these individuals. Furthermore, it unveiled the potential therapeutic options that could be suggested to these individuals.

Intracellular effects of lithium in aging neurons

Lithium therapy received approval during the 1970s, and it has been used for its antidepressant, antimanic, and anti-suicidal effects for acute and long-term prophylaxis and treatment of bipolar disorder (BPD). These properties have been well established; however, the molecular and cellular mechanisms remain controversial. In the past few years, many studies demonstrated that at the cellular level, lithium acts as a regulator of neurogenesis, aging, and Ca2+ homeostasis. At the molecular level, lithium modulates aging by inhibiting glycogen synthase kinase-3β (GSK-3β), and the phosphatidylinositol (PI) cycle; latter, lithium specifically inhibits inositol production, acting as a non-competitive inhibitor of inositol monophosphatase (IMPase). Mitochondria and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α) have been related to lithium activity, and its regulation is mediated by GSK-3β degradation and inhibition. Lithium also impacts Ca2+ homeostasis in the mitochondria modulating the function of the lithium-permeable mitochondrial Na+-Ca2+exchanger (NCLX), affecting Ca2+ efflux from the mitochondrial matrix to the endoplasmic reticulum (ER). A close relationship between the protease Omi, GSK-3β, and PGC-1α has also been established. The purpose of this review is to summarize some of the intracellular mechanisms related to lithium activity and how, through them, neuronal aging could be controlled.

Sch9S6K controls DNA repair and DNA damage response efficiency in aging cells

Survival from UV-induced DNA lesions relies on nucleotide excision repair (NER) and the Mec1ATR DNA damage response (DDR). We study DDR and NER in aging cells and find that old cells struggle to repair DNA and activate Mec1ATR. We employ pharmacological and genetic approaches to rescue DDR and NER during aging. Conditions activating Snf1AMPK rescue DDR functionality, but not NER, while inhibition of the TORC1-Sch9S6K axis restores NER and enhances DDR by tuning PP2A activity, specifically in aging cells. Age-related repair deficiency depends on Snf1AMPK-mediated phosphorylation of Sch9S6K on Ser160 and Ser163. PP2A activity in old cells is detrimental for DDR and influences NER by modulating Snf1AMPK and Sch9S6K. Hence, the DDR and repair pathways in aging cells are influenced by the metabolic tuning of opposing AMPK and TORC1 networks and by PP2A activity. Specific Sch9S6K phospho-isoforms control DDR and NER efficiency, specifically during aging.

Multifaceted effects of LRP6 in cancer: exploring tumor development, immune modulation and targeted therapies

Low-density lipoprotein receptor (LDLR)-related protein 6 (LRP6), a member of the LDLR superfamily of cell surface receptors, is most widely known as a crucial co-receptor in the activation of canonical Wnt/β-catenin signaling. This signaling pathway is implicated in multiple biological processes, such as lipoprotein metabolism, protease regulation, cell differentiation, and migration. LRP6 is frequently overexpressed in a variety of tumors, including liver cancer, colorectal cancer, and prostate cancer, and is generally considered an oncogene that promotes tumor proliferation, migration, and invasion. However, there are exceptions; some studies have reported that LRP6 inhibits lung metastasis of breast cancer through its ectodomain (LRP6N), and patients with low LRP6 expression tend to have a poor prognosis. Thus, the role of LRP6 in tumors remains controversial. Although limited studies have shown that LRP6 is associated with the expression and roles of a variety of immune cells in tumors, the interaction of LRP6 with the tumor microenvironment (TME) is not fully understood. Furthermore, it is crucial to acknowledge that LRP6 can engage with alternative pathways, including the mTORC1, CXCL12/CXCR4, and KRAS signaling pathways mentioned earlier, resulting in the regulation of biological functions independent of canonical Wnt/β-catenin signaling. Due to the potential of LRP6 as a molecular target for cancer therapy, various treatment modalities have been developed to directly or indirectly inhibit LRP6 function, demonstrating promising anti-cancer effects across multiple cancer types. This review will concentrate on exploring the expression, function, and potential therapeutic applications of LRP6 in different cancer types, along with its influence on the TME.

Panax notoginseng saponins improve oral submucous fibrosis by inhibiting the Wnt/β-catenin signal pathway

OBJECTIVE

Oral submucous fibrosis (OSF) is a chronic, insidious, progressive mucosal disease that may be affected by mutations in the Wnt/β-catenin signaling pathway. Panax notoginseng saponins (PNS) is a powerful anti-fibrosis agent; however, its effect and mechanism in treating OSF remain unclear. This study investigated the effect and mechanism of PNS treatment for OSF.

STUDY DESIGN

Arecoline was used to induce OSF models in vivo and in vitro, which were then treated with PNS. Hematoxylin-eosin (HE) and Masson trichrome staining were used to observe histopathology changes; E-cadherin and β-catenin were detected by Immunohistochemical assay, and type Ⅰ collagen (CollA1) and β-catenin were detected by immunofluorescent staining. The Wnt/β-catenin pathway and fibrosis signs were assessed using Western Blot and real-time quantitative polymerase chain reaction (RT-qPCR).

RESULTS

The expression of CollA1, Wnt1, and β-catenin were increased, and E-cadherin, GSK-3β, and β-catenin expression were decreased in OSF models. PNS and inhibitor intervention increased E-cadherin, Wnt1, and β-catenin and decreased CollA1 and GSK-3β in a dose-dependent manner.

CONCLUSION

PNS can improve OSF by inhibiting the Wnt/β-catenin signal pathway and thus may be used as a potential medicine for the treatment of OSF.

Targeting autophagy in diabetic cardiomyopathy: From molecular mechanisms to pharmacotherapy

Diabetic cardiomyopathy (DCM) is a cardiac microvascular complication caused by metabolic disorders. It is characterized by myocardial remodeling and dysfunction. The pathogenesis of DCM is associated with abnormal cellular metabolism and organelle accumulation. Autophagy is thought to play a key role in the diabetic heart, and a growing body of research suggests that modulating autophagy may be a potential therapeutic strategy for DCM. Here, we have summarized the major signaling pathways involved in the regulation of autophagy in DCM, including Adenosine 5'-monophosphate-activated protein kinase (AMPK), mechanistic target of rapamycin (mTOR), Forkhead box subfamily O proteins (FOXOs), Sirtuins (SIRTs), and PTEN-inducible kinase 1 (PINK1)/Parkin. Given the significant role of autophagy in DCM, we further identified natural products and chemical drugs as regulators of autophagy in the treatment of DCM. This review may help to better understand the autophagy mechanism of drugs for DCM and promote their clinical application.

HDAC10 inhibition represses melanoma cell growth and BRAF inhibitor resistance via upregulating SPARC expression

Secreted protein acidic and rich in cysteine (SPARC), a conserved secreted glycoprotein, plays crucial roles in regulating various biological processes. SPARC is highly expressed and has profound implications in several cancer types, including melanoma. Understanding the mechanisms that govern SPARC expression in cancers has the potential to lead to improved cancer diagnosis, prognosis, treatment strategies, and patient outcomes. Here, we demonstrate that histone deacetylase 10 (HDAC10) is a key regulator of SPARC expression in melanoma cells. Depletion or inhibition of HDAC10 upregulates SPARC expression, whereas overexpression of HDAC10 downregulates it. Mechanistically, HDAC10 coordinates with histone acetyltransferase p300 to modulate the state of acetylation of histone H3 at lysine 27 (H3K27ac) at SPARC regulatory elements and the recruitment of bromodomain-containing protein 4 (BRD4) to these regions, thereby fine-tuning SPARC transcription. HDAC10 depletion and resultant SPARC upregulation repress melanoma cell growth primarily by activating AMPK signaling and inducing autophagy. Moreover, SPARC upregulation due to HDAC10 depletion partly accounts for the resensitization of resistant cells to a BRAF inhibitor. Our work reveals the role of HDAC10 in gene regulation through indirect histone modification and suggests a potential therapeutic strategy for melanoma or other cancers by targeting HDAC10 and SPARC.

Conversion of dendritic cells into tolerogenic or inflammatory cells depends on the activation threshold and kinetics of the mTOR signaling pathway

BACKGROUND

Restoring impaired peripheral immune tolerance is the primary challenge in treating autoimmune diseases. Our previous research demonstrated the effectiveness of small spleen peptides (SSPs), a fraction of low molecular weight proteins, in inhibiting the progression of psoriatic arthritis, even in the presence of high levels of the proinflammatory cytokine TNFα in the bloodstream. When specifically targeting dendritic cells (DCs), SSPs transform them into tolerogenic cells, which efficiently induce the development of regulatory Foxp3+ Treg cells. In this study, we provide further insights into the mechanism of action of SSPs.

RESULTS

We found that SSPs stimulate the activation of the mTOR signaling pathway in dendritic cells, albeit in a different manner than the classical immunogenic stimulus LPS. While LPS-induced activation is rapid, strong, and sustained, the activity induced by SSPs is delayed, less intense, yet still significant. These distinct patterns of activation, as measured by phosphorylation of key components of the pathway are also observed in response to other immunogenic and tolerogenic stimuli such as GM-CSF + IL-4 or IL-10 and TGFβ. The disparity in mTOR activation between immunogenic and tolerogenic stimuli is quantitative rather than qualitative. In both cases, mTOR activation primarily occurs through the PI3K/Akt signaling axis and involves ERK and GSK3β kinases, with minimal involvement of AMPK or NF-kB pathways. Furthermore, in the case of SSPs, mTOR activation seems to involve adenosine receptors. Additionally, we observed that DCs treated with SSPs exhibit an energy metabolism with high plasticity, which is typical of tolerogenic cells rather than immunogenic cells.

CONCLUSION

Hence, the decision whether dendritic cells enter an inflammatory or tolerogenic state seems to rely on varying activation thresholds and kinetics of the mTOR signaling pathway.

Cilia as Wnt signaling organelles

Cilia and Wnt signaling have a complex relationship, wherein Wnt regulates cilia and, conversely, cilia may affect Wnt signaling. Recently, it was shown that Wnt receptors are present in flagella, primary cilia, and multicilia, where they transmit an intraciliary signal that is independent of β-catenin. Intraciliary Wnt signaling promotes ciliogenesis, affecting male fertility, adipogenesis, and mucociliary clearance. Wnt also stimulates the beating of motile cilia, highlighting that these nanomotors, too, are chemosensory. Intraciliary Wnt signaling employs a Wnt-protein phosphatase 1 (PP1) signaling axis, involving the canonical Wnt pathway's inhibition of glycogen synthase kinase 3 (GSK3) to repress PP1 activity. Collectively, these findings support that cilia are Wnt signaling organelles, with implications for ciliopathies and cancer.

Targeting autophagy with natural products as a potential therapeutic approach for diabetic microangiopathy

As the quality of life improves, the incidence of diabetes mellitus and its microvascular complications (DMC) continues to increase, posing a threat to people's health and wellbeing. Given the limitations of existing treatment, there is an urgent need for novel approaches to prevent and treat DMC. Autophagy, a pivotal mechanism governing metabolic regulation in organisms, facilitates the removal of dysfunctional proteins and organelles, thereby sustaining cellular homeostasis and energy generation. Anomalous states in pancreatic β-cells, podocytes, Müller cells, cardiomyocytes, and Schwann cells in DMC are closely linked to autophagic dysregulation. Natural products have the property of being multi-targeted and can affect autophagy and hence DMC progression in terms of nutrient perception, oxidative stress, endoplasmic reticulum stress, inflammation, and apoptosis. This review consolidates recent advancements in understanding DMC pathogenesis via autophagy and proposes novel perspectives on treating DMC by either stimulating or inhibiting autophagy using natural products.

Immune checkpoints between epithelial-mesenchymal transition and autophagy: A conflicting triangle

Inhibitory immune checkpoint (ICP) molecules are pivotal in inhibiting innate and acquired antitumor immune responses, a mechanism frequently exploited by cancer cells to evade host immunity. These evasion strategies contribute to the complexity of cancer progression and therapeutic resistance. For this reason, ICP molecules have become targets for antitumor drugs, particularly monoclonal antibodies, collectively referred to as immune checkpoint inhibitors (ICI), that counteract such cancer-associated immune suppression and restore antitumor immune responses. Over the last decade, however, it has become clear that tumor cell-associated ICPs can also induce tumor cell-intrinsic effects, in particular epithelial-mesenchymal transition (EMT) and macroautophagy (hereafter autophagy). Both of these processes have profound implications for cancer metastasis and drug responsiveness. This article reviews the positive or negative cross-talk that tumor cell-associated ICPs undergo with autophagy and EMT. We discuss that tumor cell-associated ICPs are upregulated in response to the same stimuli that induce EMT. Moreover, ICPs themselves, when overexpressed, become an EMT-inducing stimulus. As regards the cross-talk with autophagy, ICPs have been shown to either stimulate or inhibit autophagy, while autophagy itself can either up- or downregulate the expression of ICPs. This dynamic equilibrium also extends to the autophagy-apoptosis axis, further emphasizing the complexities of cellular responses. Eventually, we delve into the intricate balance between autophagy and apoptosis, elucidating its role in the broader interplay of cellular dynamics influenced by ICPs. In the final part of this article, we speculate about the driving forces underlying the contradictory outcomes of the reciprocal, inhibitory, or stimulatory effects between ICPs, EMT, and autophagy. A conclusive identification of these driving forces may allow to achieve improved antitumor effects when using combinations of ICIs and compounds acting on EMT and/or autophagy. Prospectively, this may translate into increased and/or broadened therapeutic efficacy compared to what is currently achieved with ICI-based clinical protocols.

Post-translational regulation of the mTORC1 pathway: A switch that regulates metabolism-related gene expression

The mechanistic target of rapamycin complex 1 (mTORC1) is a kinase complex that plays a crucial role in coordinating cell growth in response to various signals, including amino acids, growth factors, oxygen, and ATP. Activation of mTORC1 promotes cell growth and anabolism, while its suppression leads to catabolism and inhibition of cell growth, enabling cells to withstand nutrient scarcity and stress. Dysregulation of mTORC1 activity is associated with numerous diseases, such as cancer, metabolic disorders, and neurodegenerative conditions. This review focuses on how post-translational modifications, particularly phosphorylation and ubiquitination, modulate mTORC1 signaling pathway and their consequential implications for pathogenesis. Understanding the impact of phosphorylation and ubiquitination on the mTORC1 signaling pathway provides valuable insights into the regulation of cellular growth and potential therapeutic targets for related diseases.

Low-dose hypomethylating agents cooperate with ferroptosis inducers to enhance ferroptosis by regulating the DNA methylation-mediated MAGEA6-AMPK-SLC7A11-GPX4 signaling pathway in acute myeloid leukemia

BACKGROUND

Ferroptosis is a new form of nonapoptotic and iron-dependent type of cell death. Glutathione peroxidase-4 (GPX4) plays an essential role in anti-ferroptosis by reducing lipid peroxidation. Although acute myeloid leukemia (AML) cells, especially relapsed and refractory (R/R)-AML, present high GPX4 levels and enzyme activities, pharmacological inhibition of GPX4 alone has limited application in AML. Thus, whether inhibition of GPX4 combined with other therapeutic reagents has effective application in AML is largely unknown.

METHODS

Lipid reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH) assays were used to assess ferroptosis in AML cells treated with the hypomethylating agent (HMA) decitabine (DAC), ferroptosis-inducer (FIN) RAS-selective lethal 3 (RSL3), or their combination. Combination index (CI) analysis was used to assess the synergistic activity of DAC + RSL3 against AML cells. Finally, we evaluated the synergistic activity of DAC + RSL3 in murine AML and a human R/R-AML-xenografted NSG model in vivo.

RESULTS

We first assessed GPX4 expression and found that GPX4 levels were higher in AML cells, especially those with MLL rearrangements, than in NCs. Knockdown of GPX4 by shRNA and indirect inhibition of GPX4 enzyme activity by RSL3 robustly induced ferroptosis in AML cells. To reduce the dose of RSL3 and avoid side effects, low doses of DAC (0.5 µM) and RSL3 (0.05 µM) synergistically facilitate ferroptosis by inhibiting the AMP-activated protein kinase (AMPK)-SLC7A11-GPX4 axis. Knockdown of AMPK by shRNA enhanced ferroptosis, and overexpression of SLC7A11 and GPX4 rescued DAC + RSL3-induced anti-leukemogenesis. Mechanistically, DAC increased the expression of MAGEA6 by reducing MAGEA6 promoter hypermethylation. Overexpression of MAGEA6 induced the degradation of AMPK, suggesting that DAC inhibits the AMPK-SLC7A11-GPX4 axis by increasing MAGEA6 expression. In addition, DAC + RSL3 synergistically reduced leukemic burden and extended overall survival compared with either DAC or RSL3 treatment in the MLL-AF9-transformed murine model. Finally, DAC + RSL3 synergistically reduced viability in untreated and R/R-AML cells and extended overall survival in two R/R-AML-xenografted NSG mouse models.

CONCLUSIONS

Our study first identify vulnerability to ferroptosis by regulating MAGEA6-AMPK-SLC7A11-GPX4 signaling pathway. Combined treatment with HMAs and FINs provides a potential therapeutic choice for AML patients, especially for R/R-AML.

mTORC1 Mediates Biphasic Mechano-Response to Orchestrate Adhesion-Dependent Cell Growth and Anoikis Resistance

Cells constantly sense and respond to not only biochemical but also biomechanical changes in their microenvironment, demanding for dynamic metabolic adaptation. ECM stiffening is a hallmark of cancer aggressiveness, while survival under substrate detachment also associates with poor prognosis. Mechanisms underlying this, non-linear mechano-response of tumor cells may reveal potential double-hit targets for cancers. Here, an integrin-GSK3β-FTO-mTOR axis is reported, that can integrate stiffness sensing to ensure both the growth advantage endowed by rigid substrate and cell death resistance under matrix detachment. It is demonstrated that substrate stiffening can activate mTORC1 and elevate mTOR level through integrins and GSK3β-FTO mediated mRNA m6 A modification, promoting anabolic metabolism. Inhibition of this axis upon ECM detachment enhances autophagy, which in turn conveys resilience of tumor cells to anoikis, as it is demonstrated in human breast ductal carcinoma in situ (DCIS) and mice malignant ascites. Collectively, these results highlight the biphasic mechano-regulation of cellular metabolism, with implications in tumor growth under stiffened conditions such as fibrosis, as well as in anoikis-resistance during cancer metastasis.

Transcription Factor EB: A Promising Therapeutic Target for Ischemic Stroke

Transcription factor EB (TFEB) is an important endogenous defensive protein that responds to ischemic stimuli. Acute ischemic stroke is a growing concern due to its high morbidity and mortality. Most survivors suffer from disabilities such as numbness or weakness in an arm or leg, facial droop, difficulty speaking or understanding speech, confusion, impaired balance or coordination, or loss of vision. Although TFEB plays a neuroprotective role, its potential effect on ischemic stroke remains unclear. This article describes the basic structure, regulation of transcriptional activity, and biological roles of TFEB relevant to ischemic stroke. Additionally, we explore the effects of TFEB on the various pathological processes underlying ischemic stroke and current therapeutic approaches. The information compiled here may inform clinical and basic studies on TFEB, which may be an effective therapeutic drug target for ischemic stroke.

M2 Muscarinic Receptor Stimulation Induces Autophagy in Human Glioblastoma Cancer Stem Cells via mTOR Complex-1 Inhibition

BACKGROUND

Although autophagy is a pro-survival process of tumor cells, it can stimulate cell death in particular conditions and when differently regulated by specific signals. We previously demonstrated that the selective stimulation of the M2 muscarinic receptor subtype (mAChR) negatively controls cell proliferation and survival and causes oxidative stress and cytotoxic and genotoxic effects in both GBM cell lines and GBM stem cells (GSCs). In this work, we have evaluated whether autophagy was induced as a downstream mechanism of the observed cytotoxic processes induced by M2 mAChR activation by the orthosteric agonist APE or the dualsteric agonist N8-Iper (N8).

METHODS

To assess the activation of autophagy, we analyzed the expression of LC3B using Western blot analysis and in LC3B-EGFP transfected cell lines. Apoptosis was assessed by measuring the protein expression of Caspases 3 and 9.

RESULTS

Our data indicate that activation of M2 mAChR by N8 promotes autophagy in both U251 and GB7 cell lines as suggested by the LC3B-II expression level and analysis of the transfected cells by fluorescence microscopy. Autophagy induction by M2 mAChRs is regulated by the decreased activity of the PI3K/AKT/mTORC1 pathway and upregulated by pAMPK expression. Downstream of autophagy activation, an increase in apoptosis was also observed in both cell lines after treatment with the two M2 agonists.

CONCLUSIONS

N8 treatment causes autophagy via pAMPK upregulation, followed by apoptosis in both investigated cell lines. In contrast, the absence of autophagy in APE-treated GSC cells seems to indicate that cell death could be triggered by mechanisms alternative to those observed for N8.

Activation of mTOR signaling in adult lung microvascular progenitor cells accelerates lung aging

Reactivation and dysregulation of the mTOR signaling pathway are a hallmark of aging and chronic lung disease; however, the impact on microvascular progenitor cells (MVPCs), capillary angiostasis, and tissue homeostasis is unknown. While the existence of an adult lung vascular progenitor has long been hypothesized, these studies show that Abcg2 enriches for a population of angiogenic tissue-resident MVPCs present in both adult mouse and human lungs using functional, lineage, and transcriptomic analyses. These studies link human and mouse MVPC-specific mTORC1 activation to decreased stemness, angiogenic potential, and disruption of p53 and Wnt pathways, with consequent loss of alveolar-capillary structure and function. Following mTOR activation, these MVPCs adapt a unique transcriptome signature and emerge as a venous subpopulation in the angiodiverse microvascular endothelial subclusters. Thus, our findings support a significant role for mTOR in the maintenance of MVPC function and microvascular niche homeostasis as well as a cell-based mechanism driving loss of tissue structure underlying lung aging and the development of emphysema.

HDAC10 blockade upregulates SPARC expression thereby repressing melanoma cell growth and BRAF inhibitor resistance

Secreted Protein Acidic and Rich in Cysteine (SPARC), a highly conserved secreted glycoprotein, is crucial for various bioprocesses. Here we demonstrate that histone deacetylase 10 (HDAC10) is a key regulator of SPARC expression. HDAC10 depletion or inhibition upregulates, while overexpression of HDAC10 downregulates, SPARC expression. Mechanistically, HDAC10 coordinates with histone acetyltransferase p300 to modulate the acetylation state of histone H3 lysine 27 (H3K27ac) at SPARC regulatory elements and the recruitment of bromodomain-containing protein 4 (BRD4) to these regions, thereby tuning SPARC transcription. HDAC10 depletion and resultant SPARC upregulation repress melanoma cell growth, primarily by induction of autophagy via activation of AMPK signaling. Moreover, SPARC upregulation due to HDAC10 depletion partly accounts for the resensitivity of resistant cells to a BRAF inhibitor. Our work reveals the role of HDAC10 in gene regulation through epigenetic modification and suggests a potential therapeutic strategy for melanoma or other cancers by targeting HDAC10 and SPARC.

Highlights

HDAC10 is the primary HDAC member that tightly controls SPARC expression. HDAC10 coordinates with p300 in modulating the H3K27ac state at SPARC regulatory elements and the recruitment of BRD4 to these regions. HDAC10 depletion and resultant SPARC upregulation inhibit melanoma cell growth by inducing autophagy via activation of AMPK signaling.SPARC upregulation as a result of HDAC10 depletion resensitizes resistant cells to BRAF inhibitors.

The molecular basis of nutrient sensing and signalling by mTORC1 in metabolism regulation and disease

The Ser/Thr kinase mechanistic target of rapamycin (mTOR) is a central regulator of cellular metabolism. As part of mTOR complex 1 (mTORC1), mTOR integrates signals such as the levels of nutrients, growth factors, energy sources and oxygen, and triggers responses that either boost anabolism or suppress catabolism. mTORC1 signalling has wide-ranging consequences for the growth and homeostasis of key tissues and organs, and its dysregulated activity promotes cancer, type 2 diabetes, neurodegeneration and other age-related disorders. How mTORC1 integrates numerous upstream cues and translates them into specific downstream responses is an outstanding question with major implications for our understanding of physiology and disease mechanisms. In this Review, we discuss recent structural and functional insights into the molecular architecture of mTORC1 and its lysosomal partners, which have greatly increased our mechanistic understanding of nutrient-dependent mTORC1 regulation. We also discuss the emerging involvement of aberrant nutrient-mTORC1 signalling in multiple diseases.

New insights into glycogen synthase kinase-3: A common target for neurodegenerative diseases

Glycogen synthase kinase 3 (GSK-3) is a highly conserved protein serine/threonine kinase that plays a central role in a wide variety of cellular processes to coordinate catabolic and anabolic pathways and regulate cell growth and fate. There is increasing evidence showing that abnormal glycogen synthase kinase 3 (GSK-3) is associated with the pathogenesis and progression of many disorders, such as cancer, diabetes, psychiatric diseases, and neurodegenerative diseases. In this review, we summarize recent findings about the regulatory role of GSK-3 in the occurrence and development of multiple neurodegenerative diseases, mainly focusing on Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis. The aim of this study is to provide new insight into the shared working mechanism of GSK-3 as a therapeutic target of multiple neurodegenerative diseases.

Propionate promotes gluconeogenesis by regulating mechanistic target of rapamycin (mTOR) pathway in calf hepatocytes

Enhancing hepatic gluconeogenesis is one of the main modes of meeting the glucose requirement of dairy cows. This study attempted to determine whether the gluconeogenesis precursor propionate had an effect on the expression of the main genes involved in gluconeogenesis in calf hepatocytes and elucidate the associated mechanisms. Calf hepatocytes were obtained from 5 healthy calves (1 d old; 30 to 40 kg) and exposed to 0-, 1-, 2.5-, or 5-mM sodium propionate (NaP), which is known to promote the expression of genes involved in the gluconeogenesis pathway, including fructose 1,6-bisphosphatase, phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase. With regard to the underlying mechanism, propionate promoted the expression of peroxisome proliferator-activated receptor gamma coactivator 1-alpha, hepatocyte nuclear factor 4, and forkhead box O1 (transcription factors that regulate the expression of hepatic gluconeogenic genes) by promoting mammalian target of rapamycin complex 1 (mTORC1), but inhibiting mTORC2 activity (P < 0.01). We also established a model of palmitic acid (PA)-induced hepatic injury in calf hepatocytes and found that PA could inhibit the gluconeogenic capacity of calf hepatocytes by suppressing the expression of gluconeogenic genes, inhibiting mTORC1, and promoting the activity of mTORC2 (P < 0.01). In contrast, NaP provided protection to calf hepatocytes by counteracting the inhibitory effect of PA on the gluconeogenic capacity of calf hepatocytes (P < 0.05). Collectively, these findings indicate that NaP enhances the gluconeogenic capacity of calf hepatocytes by regulating the mTOR pathway activity. Thus, in addition to improving the glucose production potential, propionate may have therapeutic potential for the treatment of hepatic injury in dairy cows.

Knockdown of LMNA inhibits Akt/β-catenin-mediated cell invasion and migration in clear cell renal cell carcinoma cells

The LMNA gene encoding lamin A/C is amplified in some clear cell renal cell carcinoma (ccRCC) samples. Our data showed that depletion of the tumor suppressor PBRM1 can upregulate lamin A/C levels, and lamin A/C could interact with PBRM1. However, the role of lamin A/C in ccRCC is not yet fully understood. Our functional assays showed that although the proliferation ability was slightly impaired after LMNA depletion, the migration and invasion of ccRCC cells were significantly inhibited. This suppression was accompanied by a reduction in MMP2, MMP9, AKT/p-AKT, and Wnt/β-catenin protein levels. Our data therefore suggest that lamin A/C, as an interaction partner of the tumor suppressor PBRM1, plays a crucial role in tumor invasion and metastasis in ccRCC.

Modeling unveils sex differences of signaling networks in mouse embryonic stem cells

For a short period during early development of mammalian embryos, both X chromosomes in females are active, before dosage compensation is ensured through X-chromosome inactivation. In female mouse embryonic stem cells (mESCs), which carry two active X chromosomes, increased X-dosage affects cell signaling and impairs differentiation. The underlying mechanisms, however, remain poorly understood. To dissect X-dosage effects on the signaling network in mESCs, we combine systematic perturbation experiments with mathematical modeling. We quantify the response to a variety of inhibitors and growth factors for cells with one (XO) or two X chromosomes (XX). We then build models of the signaling networks in XX and XO cells through a semi-quantitative modeling approach based on modular response analysis. We identify a novel negative feedback in the PI3K/AKT pathway through GSK3. Moreover, the presence of a single active X makes mESCs more sensitive to the differentiation-promoting Activin A signal and leads to a stronger RAF1-mediated negative feedback in the FGF-triggered MAPK pathway. The differential response to these differentiation-promoting pathways can explain the impaired differentiation propensity of female mESCs.

Redox-Mediated Rewiring of Signalling Pathways: The Role of a Cellular Clock in Brain Health and Disease

Metazoan signalling pathways can be rewired to dampen or amplify the rate of events, such as those that occur in development and aging. Given that a linear network topology restricts the capacity to rewire signalling pathways, such scalability of the pace of biological events suggests the existence of programmable non-linear elements in the underlying signalling pathways. Here, we review the network topology of key signalling pathways with a focus on redox-sensitive proteins, including PTEN and Ras GTPase, that reshape the connectivity profile of signalling pathways in response to an altered redox state. While this network-level impact of redox is achieved by the modulation of individual redox-sensitive proteins, it is the population by these proteins of critical nodes in a network topology of signal transduction pathways that amplifies the impact of redox-mediated reprogramming. We propose that redox-mediated rewiring is essential to regulate the rate of transmission of biological signals, giving rise to a programmable cellular clock that orchestrates the pace of biological phenomena such as development and aging. We further review the evidence that an aberrant redox-mediated modulation of output of the cellular clock contributes to the emergence of pathological conditions affecting the human brain.

Insulin-like growth factor receptor / mTOR signaling elevates global translation to accelerate zebrafish fin regenerative outgrowth

Zebrafish robustly regenerate fins, including their characteristic bony ray skeleton. Amputation activates intra-ray fibroblasts and dedifferentiates osteoblasts that migrate under a wound epidermis to establish an organized blastema. Coordinated proliferation and re-differentiation across lineages then sustains progressive outgrowth. We generate a single cell transcriptome dataset to characterize regenerative outgrowth and explore coordinated cell behaviors. We computationally identify sub-clusters representing most regenerative fin cell lineages, and define markers of osteoblasts, intra- and inter-ray fibroblasts and growth-promoting distal blastema cells. A pseudotemporal trajectory and in vivo photoconvertible lineage tracing indicate distal blastemal mesenchyme restores both intra- and inter-ray fibroblasts. Gene expression profiles across this trajectory suggest elevated protein production in the blastemal mesenchyme state. O-propargyl-puromycin incorporation and small molecule inhibition identify insulin growth factor receptor (IGFR)/mechanistic target of rapamycin kinase (mTOR)-dependent elevated bulk translation in blastemal mesenchyme and differentiating osteoblasts. We test candidate cooperating differentiation factors identified from the osteoblast trajectory, finding IGFR/mTOR signaling expedites glucocorticoid-promoted osteoblast differentiation in vitro. Concordantly, mTOR inhibition slows but does not prevent fin regenerative outgrowth in vivo. IGFR/mTOR may elevate translation in both fibroblast- and osteoblast-lineage cells during the outgrowth phase as a tempo-coordinating rheostat.

When You Come to a Fork in the Road, Take It: Wnt Signaling Activates Multiple Pathways through the APC/Axin/GSK-3 Complex

The Wnt signaling pathway is a highly conserved regulator of metazoan development and stem cell maintenance. Activation of Wnt signaling is an early step in diverse malignancies. Work over the past four decades has defined a "canonical" Wnt pathway that is initiated by Wnt proteins, secreted glycoproteins that bind to a surface receptor complex and activate intracellular signal transduction by inhibiting a catalytic complex composed of the classical tumor suppressor Adenomatous Polyposis Coli (APC), Axin, and Glycogen Synthase Kinase-3 (GSK-3). The best characterized effector of this complex is β-catenin, which is stabilized by inhibition of GSK-3, allowing β-catenin entrance to the nucleus and activation of Wnt target gene transcription, leading to multiple cancers when inappropriately activated. However, canonical Wnt signaling through the APC/Axin/GSK-3 complex impinges on other effectors, independently of β-catenin, including the mechanistic Target of Rapamycin (mTOR), regulators of protein stability, mitotic spindle orientation, and Hippo signaling. This review focuses on these alternative effectors of the canonical Wnt pathway and how they may contribute to cancers.

PI3K/AKT/mTOR signaling transduction pathway and targeted therapies in cancer

The PI3K/AKT/mTOR (PAM) signaling pathway is a highly conserved signal transduction network in eukaryotic cells that promotes cell survival, cell growth, and cell cycle progression. Growth factor signalling to transcription factors in the PAM axis is highly regulated by multiple cross-interactions with several other signaling pathways, and dysregulation of signal transduction can predispose to cancer development. The PAM axis is the most frequently activated signaling pathway in human cancer and is often implicated in resistance to anticancer therapies. Dysfunction of components of this pathway such as hyperactivity of PI3K, loss of function of PTEN, and gain-of-function of AKT, are notorious drivers of treatment resistance and disease progression in cancer. In this review we highlight the major dysregulations in the PAM signaling pathway in cancer, and discuss the results of PI3K, AKT and mTOR inhibitors as monotherapy and in co-administation with other antineoplastic agents in clinical trials as a strategy for overcoming treatment resistance. Finally, the major mechanisms of resistance to PAM signaling targeted therapies, including PAM signaling in immunology and immunotherapies are also discussed.

O-GlcNAcylation of Raptor transduces glucose signals to mTORC1

The mechanistic target of rapamycin complex 1 (mTORC1) regulates metabolism and cell growth in response to nutrient levels. Dysregulation of mTORC1 results in a broad spectrum of diseases. Glucose is the primary energy supply of cells, and therefore, glucose levels must be accurately conveyed to mTORC1 through highly responsive signaling mechanisms to control mTORC1 activity. Here, we report that glucose-induced mTORC1 activation is regulated by O-GlcNAcylation of Raptor, a core component of mTORC1, in HEK293T cells. Mechanistically, O-GlcNAcylation of Raptor at threonine 700 facilitates the interactions between Raptor and Rag GTPases and promotes the translocation of mTOR to the lysosomal surface, consequently activating mTORC1. In addition, we show that AMPK-mediated phosphorylation of Raptor suppresses Raptor O-GlcNAcylation and inhibits Raptor-Rags interactions. Our findings reveal an exquisitely controlled mechanism, which suggests how glucose coordinately regulates cellular anabolism and catabolism.

Transcriptional regulation of the mouse EphA4, Ephrin-B2 and Ephrin-A3 genes by the circadian clock machinery

Circadian rhythms originate from molecular feedback loops. In mammals, the transcription factors CLOCK and BMAL1 act on regulatory elements (i.e. E-boxes) to shape biological functions in a rhythmic manner. The EPHA4 receptor and its ligands Ephrins (EFN) are cell adhesion molecules regulating neurotransmission and neuronal morphology. Previous studies showed the presence of E-boxes in the genes of EphA4 and specific Ephrins, and that EphA4 knockout mice have an altered circadian rhythm of locomotor activity. We thus hypothesized that the core clock machinery regulates the gene expression of EphA4, EfnB2 and EfnA3. CLOCK and BMAL1 (or NPAS2 and BMAL2) were found to have transcriptional activity on distal and proximal regions of EphA4, EfnB2 and EfnA3 putative promoters. A constitutively active form of glycogen synthase kinase 3β (GSK3β; a negative regulator of CLOCK and BMAL1) blocked the transcriptional induction. Mutating the E-boxes of EphA4 distal promoter sequence reduced transcriptional induction. EPHA4 and EFNB2 protein levels did not show circadian variations in the mouse suprachiasmatic nucleus or prefrontal cortex. The findings uncover that core circadian transcription factors can regulate the gene expression of elements of the Eph/Ephrin system, which might contribute to circadian rhythmicity in biological processes in the brain or peripheral tissues.

mTOR Signaling Pathway and Gut Microbiota in Various Disorders: Mechanisms and Potential Drugs in Pharmacotherapy

The mammalian or mechanistic target of rapamycin (mTOR) integrates multiple intracellular and extracellular upstream signals involved in the regulation of anabolic and catabolic processes in cells and plays a key regulatory role in cell growth and metabolism. The activation of the mTOR signaling pathway has been reported to be associated with a wide range of human diseases. A growing number of in vivo and in vitro studies have demonstrated that gut microbes and their complex metabolites can regulate host metabolic and immune responses through the mTOR pathway and result in disorders of host physiological functions. In this review, we summarize the regulatory mechanisms of gut microbes and mTOR in different diseases and discuss the crosstalk between gut microbes and their metabolites and mTOR in disorders in the gastrointestinal tract, liver, heart, and other organs. We also discuss the promising application of multiple potential drugs that can adjust the gut microbiota and mTOR signaling pathways. Despite the limited findings between gut microbes and mTOR, elucidating their relationship may provide new clues for the prevention and treatment of various diseases.

Regulation of mTOR Signaling: Emerging Role of Cyclic Nucleotide-Dependent Protein Kinases and Implications for Cardiometabolic Disease

The mechanistic target of rapamycin (mTOR) kinase is a central regulator of cell growth and metabolism. It is the catalytic subunit of two distinct large protein complexes, mTOR complex 1 (mTORC1) and mTORC2. mTOR activity is subjected to tight regulation in response to external nutrition and growth factor stimulation. As an important mechanism of signaling transduction, the 'second messenger' cyclic nucleotides including cAMP and cGMP and their associated cyclic nucleotide-dependent kinases, including protein kinase A (PKA) and protein kinase G (PKG), play essential roles in mediating the intracellular action of a variety of hormones and neurotransmitters. They have also emerged as important regulators of mTOR signaling in various physiological and disease conditions. However, the mechanism by which cAMP and cGMP regulate mTOR activity is not completely understood. In this review, we will summarize the earlier work establishing the ability of cAMP to dampen mTORC1 activation in response to insulin and growth factors and then discuss our recent findings demonstrating the regulation of mTOR signaling by the PKA- and PKG-dependent signaling pathways. This signaling framework represents a new non-canonical regulation of mTOR activity that is independent of AKT and could be a novel mechanism underpinning the action of a variety of G protein-coupled receptors that are linked to the mTOR signaling network. We will further review the implications of these signaling events in the context of cardiometabolic disease, such as obesity, non-alcoholic fatty liver disease, and cardiac remodeling. The metabolic and cardiac phenotypes of mouse models with targeted deletion of Raptor and Rictor, the two essential components for mTORC1 and mTORC2, will be summarized and discussed.

Expression of mTOR in normal and pathological conditions

The mechanistic/mammalian target of rapamycin (mTOR), a protein discovered in 1991, integrates a complex pathway with a key role in maintaining cellular homeostasis. By comprising two functionally distinct complexes, mTOR complex 1 (mTORC1) and mTORC2, it is a central cellular hub that integrates intra- and extracellular signals of energy, nutrient, and hormone availability, modulating the molecular responses to acquire a homeostatic state through the regulation of anabolic and catabolic processes. Accordingly, dysregulation of mTOR pathway has been implicated in a variety of human diseases. While major advances have been made regarding the regulators and effectors of mTOR signaling pathway, insights into the regulation of mTOR gene expression are beginning to emerge. Here, we present the current available data regarding the mTOR expression regulation at the level of transcription, translation and mRNA stability and systematize the current knowledge about the fluctuations of mTOR expression observed in several diseases, both cancerous and non-cancerous. In addition, we discuss whether mTOR expression changes can be used as a biomarker for diagnosis, disease progression, prognosis and/or response to therapeutics. We believe that our study will contribute for the implementation of new disease biomarkers based on mTOR as it gives an exhaustive perspective about the regulation of mTOR gene expression in both normal and pathological conditions.

Exploring the mTOR Signalling Pathway and Its Inhibitory Scope in Cancer

Mechanistic target of rapamycin (mTOR) is a protein kinase that regulates cellular growth, development, survival, and metabolism through integration of diverse extracellular and intracellular stimuli. Additionally, mTOR is involved in interplay of signalling pathways that regulate apoptosis and autophagy. In cells, mTOR is assembled into two complexes, mTORC1 and mTORC2. While mTORC1 is regulated by energy consumption, protein intake, mechanical stimuli, and growth factors, mTORC2 is regulated by insulin-like growth factor-1 receptor (IGF-1R), and epidermal growth factor receptor (EGFR). mTOR signalling pathways are considered the hallmark in cancer due to their dysregulation in approximately 70% of cancers. Through downstream regulators, ribosomal protein S6 kinase β-1 (S6K1) and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1), mTORC1 influences various anabolic and catabolic processes in the cell. In recent years, several mTOR inhibitors have been developed with the aim of treating different cancers. In this review, we will explore the current developments in the mTOR signalling pathway and its importance for being targeted by various inhibitors in anti-cancer therapeutics.

Interaction of lncRNAs with mTOR in colorectal cancer: a systematic review

Colorectal cancer (CRC) is the third most widespread cancer and the fourth leading lethal disease among different societies. It is thought that CRC accounts for about 10% of all newly diagnosed cancer cases with high-rate mortality. lncRNAs, belonging to non-coding RNAs, are involved in varied cell bioactivities. Emerging data have confirmed a significant alteration in lncRNA transcription under anaplastic conditions. This systematic review aimed to assess the possible influence of abnormal mTOR-associated lncRNAs in the tumorigenesis of colorectal tissue. In this study, the PRISMA guideline was utilized based on the systematic investigation of published articles from seven databases. Of the 200 entries, 24 articles met inclusion criteria and were used for subsequent analyses. Of note, 23 lncRNAs were prioritized in association with the mTOR signaling pathway with up-regulation (79.16%) and down-regulation (20.84%) trends. Based on the obtained data, mTOR can be stimulated or inhibited during CRC by the alteration of several lncRNAs. Determining the dynamic activity of mTOR and relevant signaling pathways via lncRNAs can help us progress novel molecular therapeutics and medications.

Neurotrophic effects of intermittent fasting, calorie restriction and exercise: a review and annotated bibliography

In the last decades, important progress has been achieved in the understanding of the neurotrophic effects of intermittent fasting (IF), calorie restriction (CR) and exercise. Improved neuroprotection, synaptic plasticity and adult neurogenesis (NSPAN) are essential examples of these neurotrophic effects. The importance in this respect of the metabolic switch from glucose to ketone bodies as cellular fuel has been highlighted. More recently, calorie restriction mimetics (CRMs; resveratrol and other polyphenols in particular) have been investigated thoroughly in relation to NSPAN. In the narrative review sections of this manuscript, recent findings on these essential functions are synthesized and the most important molecules involved are presented. The most researched signaling pathways (PI3K, Akt, mTOR, AMPK, GSK3β, ULK, MAPK, PGC-1α, NF-κB, sirtuins, Notch, Sonic hedgehog and Wnt) and processes (e.g., anti-inflammation, autophagy, apoptosis) that support or thwart neuroprotection, synaptic plasticity and neurogenesis are then briefly presented. This provides an accessible entry point to the literature. In the annotated bibliography section of this contribution, brief summaries are provided of about 30 literature reviews relating to the neurotrophic effects of interest in relation to IF, CR, CRMs and exercise. Most of the selected reviews address these essential functions from the perspective of healthier aging (sometimes discussing epigenetic factors) and the reduction of the risk for neurodegenerative diseases (Alzheimer's disease, Huntington's disease, Parkinson's disease) and depression or the improvement of cognitive function.

The role of TSC2 in breast cancer: a literature review

TSC2 is a tumor suppressor gene as well as a disease-causing gene for autosomal dominant disorder tuberous sclerosis complex (TSC). Research has found that some tumor tissues have lower TSC2 expression levels than normal tissues. Furthermore, low expression of TSC2 is associated with poor prognosis in breast cancer. TSC2 acts as a convergence point of a complex network of signaling pathways and receives signals from the PI3K, AMPK, MAPK, and WNT pathways. It also regulates cellular metabolism and autophagy through inhibition of a mechanistic target of rapamycin complex, which are processes relevant to the progression, treatment, and prognosis of breast cancer. In-depth study of TSC2 functions provides significant guidance for clinical applications in breast cancer, including improving the treatment efficacy, overcoming drug resistance, and predicting prognosis. In this review, protein structure and biological functions of TSC2 were described and recent advances in TSC2 research in different molecular subtypes of breast cancer were summarized.

Deciphering the Clinical Significance and Kinase Functions of GSK3α in Colon Cancer by Proteomics and Phosphoproteomics

GSK3α and GSK3β are two GSK3 isoforms with 84% overall identity and 98% identity in their catalytic domains. GSK3β plays important roles in the pathogenesis of cancer, while GSK3α has long been considered a functionally redundant protein of GSK3β. Few studies have specifically investigated the functions of GSK3α. In this study, unexpectedly, we found that the expression of GSK3α, but not GSK3β, was significantly correlated with the overall survival of colon cancer patients in 4 independent cohorts. To decipher the roles of GSK3α in colon cancer, we profiled the phosphorylation substrates of GSK3α and uncovered 156 phosphosites from 130 proteins specifically regulated by GSK3α. A number of these GSK3α-mediated phosphosites have never been reported before or have been incorrectly identified as substrates of GSK3β. Among them, the levels of HSF1S303p, CANXS583p, MCM2S41p, POGZS425p, SRRM2T983p, and PRPF4BS431p were significantly correlated with the overall survival of colon cancer patients. Further pull-down assays identified 23 proteins, such as THRAP3, BCLAF1, and STAU1, showing strong binding affinity to GSK3α. The interaction between THRAP3 and GSK3α was verified by biochemical experiments. Notably, among the 18 phosphosites of THRAP3, phosphorylation at S248, S253, and S682 is specifically mediated by GSK3α. Mutation of S248 to D (S248D), which mimics the effect of phosphorylation, obviously increased cancer cell migration and the binding affinity to proteins related to DNA damage repair. Collectively, this work not only discloses the specific function of GSK3α as a kinase but also suggests GSK3α as a promising therapeutic target for colon cancer.

Lnc-ing epigenetic mechanisms with autophagy and cancer drug resistance

Long noncoding RNAs (lncRNAs) comprise a diverse class of RNA molecules that regulate various physiological processes and have been reported to be involved in several human pathologies ranging from neurodegenerative disease to cancer. Therapeutic resistance is a major hurdle for cancer treatment. Over the past decade, several studies has emerged on the role of lncRNAs in cancer drug resistance and many trials have been conducted employing them. LncRNAs also regulate different cell death pathways thereby maintaining a fine balance of cell survival and death. Autophagy is a complex cell-killing mechanism that has both cytoprotective and cytotoxic roles. Similarly, autophagy can lead to the induction of both chemosensitization and chemoresistance in cancer cells upon therapeutic intervention. Recently the role of lncRNAs in the regulation of autophagy has also surfaced. Thus, lncRNAs can be used in cancer therapeutics to alleviate the challenges of chemoresistance by targeting the autophagosomal axis. In this chapter, we discuss about the role of lncRNAs in autophagy-mediated cancer drug resistance and its implication in targeted cancer therapy.

Role of mammalian target of rapamycin (mTOR) signalling in oncogenesis

The signalling system known as mammalian target of rapamycin (mTOR) is believed to be required for several biological activities involving cell proliferation. The serine-threonine kinase identified as mTOR recognises PI3K-AKT stress signals. It is well established in the scientific literature that the deregulation of the mTOR pathway plays a crucial role in cancer growth and advancement. This review focuses on the normal functions of mTOR as well as its abnormal roles in cancer development.

The role of autophagy in cardiovascular disease: Cross-interference of signaling pathways and underlying therapeutic targets

Autophagy is a conserved lysosomal pathway for the degradation of cytoplasmic proteins and organelles, which realizes the metabolic needs of cells and the renewal of organelles. Autophagy-related genes (ATGs) are the main molecular mechanisms controlling autophagy, and their functions can coordinate the whole autophagic process. Autophagy can also play a role in cardiovascular disease through several key signaling pathways, including PI3K/Akt/mTOR, IGF/EGF, AMPK/mTOR, MAPKs, p53, Nrf2/p62, Wnt/β-catenin and NF-κB pathways. In this paper, we reviewed the signaling pathway of cross-interference between autophagy and cardiovascular diseases, and analyzed the development status of novel cardiovascular disease treatment by targeting the core molecular mechanism of autophagy as well as the critical signaling pathway. Induction or inhibition of autophagy through molecular mechanisms and signaling pathways can provide therapeutic benefits for patients. Meanwhile, we hope to provide a unique insight into cardiovascular treatment strategies by understanding the molecular mechanism and signaling pathway of crosstalk between autophagy and cardiovascular diseases.

Brain insulin resistance linked Alzheimer's and Parkinson's disease pathology: An undying implication of epigenetic and autophagy modulation

In metabolic syndrome, dysregulated signalling activity of the insulin receptor pathway in the brain due to persistent insulin resistance (IR) condition in the periphery may lead to brain IR (BIR) development. BIR causes an upsurge in the activity of glycogen synthase kinase-3 beta, increased amyloid beta (Aβ) accumulation, hyperphosphorylation of tau, aggravated formation of Aβ oligomers and simultaneously neurofibrillary tangle formation, all of which are believed to be direct contributors in Alzheimer's Disease (AD) pathology. Likewise, for Parkinson's Disease (PD), BIR is associated with alpha-synuclein alterations, dopamine loss in brain areas which ultimately succumbs towards the appearance of classical motor symptoms corresponding to the typical PD phenotype. Modulation of the autophagy process for clearing misfolded proteins and alteration in histone proteins to alleviate disease progression in BIR-linked AD and PD have recently evolved as a research hotspot, as the majority of the autophagy-related proteins are believed to be regulated by histone posttranslational modifications. Hence, this review will provide a timely update on the possible mechanism(s) converging towards BIR induce AD and PD. Further, emphasis on the potential epigenetic regulation of autophagy that can be effectively targeted for devising a complete therapeutic cure for BIR-induced AD and PD will also be reviewed.