• Mechanistic target of rapamycin complex 1
• Naked cuticle homolog 2
• Osteoblast
• Osteoclast
• Receptor activator of nuclear factor κB ligand
• Wnt/β-catenin

• CD4 + T cell differentiation
• Dihydroberberine
• Premature ovarian insufficiency
• Rheb/mTOR signaling pathway
• Th17/Treg immune imbalance

• Animals
• Female
• T-Lymphocytes, Regulatory/metabolism
• T-Lymphocytes, Regulatory/immunology
• T-Lymphocytes, Regulatory/drug effects
• Th17 Cells/metabolism
• Th17 Cells/immunology
• Th17 Cells/drug effects
• TOR Serine-Threonine Kinases/metabolism
• Signal Transduction/drug effects
• Mice
• Primary Ovarian Insufficiency/metabolism
• Primary Ovarian Insufficiency/drug therapy
• Primary Ovarian Insufficiency/etiology
• Ras Homolog Enriched in Brain Protein/metabolism
• Disease Models, Animal
• Mice, Inbred BALB C
• Apoptosis/drug effects
• Ovary/metabolism
• Ovary/drug effects
• Ovary/pathology
• Cell Proliferation/drug effects

• 23YY06 Science and technology development fund of the Hospital of Chengdu University of traditional Chinese medicine in 2023
• No. 82405464 the National Natural Science Foundation of China Youth Program
• No.81973684 the National Natural Science Foundation of China
• No.2023NSFSC1760 the Natural Science Foundation of Sichuan Province
• NO. Maternal and Child YCXY 20-10 The Science and Technology Innovation Startup Fund of Fujian Maternity and Child Health Hospital, the introduction of talent supporting scientific research projects

• Animals
• Male
• Mice
• Calcium/metabolism
• Cocaine/pharmacology
• Homeostasis/drug effects
• Illicit Drugs/adverse effects
• Mice, Inbred C57BL
• Nucleus Accumbens/metabolism
• Nucleus Accumbens/drug effects
• Proto-Oncogene Proteins c-fos/metabolism
• Proto-Oncogene Proteins c-fos/genetics
• Ras Homolog Enriched in Brain Protein/metabolism
• Ras Homolog Enriched in Brain Protein/genetics
• Reward
• Signal Transduction
• Single-Cell Analysis
• Substance-Related Disorders
• Dopaminergic Neurons/drug effects
• Dopaminergic Neurons/metabolism

• P01 DA047233 NIDA NIH HHS
• R01 DA007359 NIDA NIH HHS
• U01 NS115530 NINDS NIH HHS
• R01 DA014133 NIDA NIH HHS
• Howard Hughes Medical Institute
• RF1 NS113251 NINDS NIH HHS
• RF1 NS110501 NINDS NIH HHS

• P01 DA047233 NIDA NIH HHS
• U01 NS115530 NINDS NIH HHS
• R01 DA014133 NIDA NIH HHS
• RF1 NS113251 NINDS NIH HHS
• RF1 NS110501 NINDS NIH HHS

• Akt PKB
• PI3K
• S6 kinase
• apoptosis
• cell signaling
• eukaryotic translation initiation factor 4E
• eukaryotic translation initiation factor 4E-binding protein
• pH regulation
• protein synthesis
• target of rapamycin

• Mechanistic Target of Rapamycin Complex 1/metabolism
• Humans
• Signal Transduction
• Hydrogen-Ion Concentration
• Phosphatidylinositol 3-Kinases/metabolism
• Mechanistic Target of Rapamycin Complex 2/metabolism
• Multiprotein Complexes/metabolism
• Multiprotein Complexes/genetics
• TOR Serine-Threonine Kinases/metabolism
• Proto-Oncogene Proteins c-akt/metabolism
• Phosphorylation
• Monomeric GTP-Binding Proteins/metabolism
• Ras Homolog Enriched in Brain Protein/metabolism
• Neuropeptides/metabolism
• Adaptor Proteins, Signal Transducing/metabolism
• Adaptor Proteins, Signal Transducing/genetics
• Tuberous Sclerosis Complex 2 Protein/metabolism
• Tuberous Sclerosis Complex 2 Protein/genetics
• Tumor Suppressor Proteins/metabolism
• Tumor Suppressor Proteins/genetics
• Intercellular Signaling Peptides and Proteins/metabolism
• Phosphoproteins/metabolism
• Cell Cycle Proteins/metabolism
• Cell Cycle Proteins/genetics

• P30 DK020572 NIDDK NIH HHS
• R01 GM137577 NIGMS NIH HHS

• CP: Developmental biology
• CP: Neuroscience
• DLK1
• Raptor
• Rheb
• hypomyelination
• mTORC1
• myelination
• myelination deficit
• neuron-OPC interaction
• neuron-glia interaction
• oligodendrocyte differentiation

• Animals
• Mice
• Cell Differentiation/genetics
• Mechanistic Target of Rapamycin Complex 1/metabolism
• Mice, Transgenic
• Myelin Sheath/metabolism
• Oligodendroglia/metabolism
• Signal Transduction/physiology
• Ras Homolog Enriched in Brain Protein/metabolism

• P50 DA044123 NIDA NIH HHS
• R35 NS097966 NINDS NIH HHS

• anticancer drug resistance
• autophagy
• cisplatin
• mTORC1 pathway

• 2023 Ligue Nationale Contre le Cancer
• No number Chinese Scholarship Council fellowship

• PI3K
• TSC2
• breast cancer
• mTOR
• signaling pathways

• GATOR2
• MIOS
• Oligodendrocyte
• RHEB
• Schwann cell
• lactate
• mTORC1
• mitochondria
• myelination

• Amino Acids
• Myelin Sheath/metabolism
• Schwann Cells/metabolism
• Oligodendroglia/metabolism
• Signal Transduction
• Intercellular Signaling Peptides and Proteins/metabolism

• Ca2+ mobilization
• TSC2
• calmodulin
• mTOR

• Antioxidants
• BCAA
• Horse
• Muscle energy metabolism
• Muscle hypertrophy

• Humans
• Animals
• Mice
• Cystic Fibrosis Transmembrane Conductance Regulator/metabolism
• Chlorides/metabolism
• Tuberous Sclerosis/metabolism
• Polycystic Kidney Diseases
• Kidney/metabolism
• Epithelium/metabolism
• Cysts
• Forkhead Transcription Factors/metabolism

• I01 BX001000 BLRD VA
• P30 CA118100 NCI NIH HHS
• T32 HL007736 NHLBI NIH HHS

• Apoptosis
• Autophagy
• Cellular stress
• Endoplasmic reticulum
• Interferon
• Mitochondria
• Virus entry
• Virus replication

• Swine
• Animals
• African Swine Fever Virus/genetics
• African Swine Fever/metabolism
• Viral Proteins/genetics
• Host-Pathogen Interactions
• Virus Replication

Tuberous sclerosis complex (TSC) is caused by mutations in the hamartin (TSC1) or tuberin (TSC2) genes. Using a mouse model of TSC renal cystogenesis that we have previously described, the current studies delineate the metabolic changes in the kidney and their relation to alterations in renal gene expression. To accomplish this, we compared the metabolome and transcriptome of kidneys from 28-day-old wildtype (Wt) and principal cell-specific Tsc1 KO (Tsc1 KO) mice using targeted ¹H nuclear magnetic resonance targeted metabolomic and RNA-seq analyses. The significant changes in the kidney metabolome of Tsc1 KO mice included reductions in the level of several amino acids and significant decreases in creatine, NADH, inosine, UDP-galactose, GTP and myo-inositol levels. These derangements may affect energy production and storage, signal transduction and synthetic pathways. The pertinent derangement in the transcriptome of Tsc1 KO mice was associated with increased collecting duct acid secretion, active cell division and the up-regulation of signaling pathways (e.g., MAPK and AKT/PI3K) that suppress the TSC2 GTPase-activating function. The combined renal metabolome and transcriptome alterations observed in these studies correlate with the unregulated growth and predominance of genotypically normal A-intercalated cells in the epithelium of renal cysts in Tsc1 KO mice.

Rheb is a small GTPase member of the Ras superfamily and an activator of mTORC1, a protein complex master regulator of cell metabolism, growth, and proliferation. Rheb/mTORC1 pathway is hyperactivated in proliferative diseases, such as Tuberous Sclerosis Complex syndrome and cancer. Therefore, targeting Rheb-dependent signaling is a rational strategy for developing new drug therapies. Rheb activates mTORC1 in the cytosolic surface of lysosomal membranes. Rheb’s farnesylation allows its anchorage on membranes, while its proper localization depends on the prenyl-binding chaperone PDEδ. Recently, the use of PDEδ inhibitors has been proposed as anticancer agents because they interrupted KRas signaling leading to antiproliferative effects in KRas-dependent pancreatic cancer cells. However, the effect of PDEδ inhibition on the Rheb/mTORC1 pathway has been poorly investigated. Here, we evaluated the impact of a new PDEδ inhibitor, called Deltasonamide 1, in Tsc2-null MEFs, a Rheb-dependent overactivated mTORC1 cell line. By using a yeast two-hybrid assay, we first validated that Deltasonamide 1 disrupts Rheb-PDEδ interaction. Accordingly, we found that Deltasonamide 1 reduces mTORC1 targets activation. In addition, our results showed that Deltasonamide 1 has antiproliferative and cytotoxic effects on Tsc2-null MEFs but has less effect on Tsc2-wild type MEFs viability. This work proposes the pharmacological PDEδ inhibition as a new approach to target the abnormal Rheb/mTORC1 activation in Tuberous Sclerosis Complex cells.

• Fondo Nacional de Desarrollo Científico y Tecnológico

• PD-1
• T-cell exhaustion
• chronic viral infection
• glycolysis
• metabolism

• Adaptive Immunity
• CD8-Positive T-Lymphocytes
• Graft vs Host Disease/metabolism
• HIV Infections/metabolism
• Humans
• Virus Diseases

• National Natural Science Foundation of China
• Basic and Applied Basic Research Foundation of Guangdong Province
• Guangzhou Municipal Science and Technology Project
• Natural Science Foundation of Guangdong Province for Distinguished Young Scholars

The tumor suppressor p53 is activated upon multiple cellular stresses, including DNA damage, oncogene activation, ribosomal stress, and hypoxia, to induce cell cycle arrest, apoptosis, and senescence. Mammalian target of rapamycin (mTOR), an evolutionarily conserved serine/threonine protein kinase, serves as a central regulator of cell growth, proliferation, and survival by coordinating nutrients, energy, growth factors, and oxygen levels. p53 dysfunction and mTOR pathway hyperactivation are hallmarks of human cancer. The balance between response to stresses or commitment to cell proliferation and survival is governed by various regulatory loops between the p53 and mTOR pathways. In this review, we first briefly introduce the tumor suppressor p53 and then describe the upstream regulators and downstream effectors of the mTOR pathway. Next, we discuss the role of p53 in regulating the mTOR pathway through its transcriptional and non-transcriptional effects. We further describe the complicated role of the mTOR pathway in modulating p53 activity. Finally, we discuss the current knowledge and future perspectives on the coordinated regulation of the p53 and mTOR pathways.

• MDM2
• mTOR
• miRNA
• p53
• post-translation
• transcription
• tumorigenesis

• Amino acids
• Leucine
• Mammal
• Signaling pathway
• mTORC1

• amino acids
• intrinsically labelled protein
• muscle protein synthesis
• protein turnover
• sex-based differences

• GATOR complex
• SEA complex
• amino acid signaling
• autophagy
• cancer
• epilepsy
• mTORC1 pathway
• neurological disorders

• Animals
• Disease
• Humans
• Multiprotein Complexes/chemistry
• Multiprotein Complexes/metabolism
• Nutrients
• Phenotype
• Signal Transduction
• Terminology as Topic

The mechanistic target of rapamycin (mTOR) complex 2 (mTORC2) signaling controls cell metabolism, promotes cell survival, and contributes to tumorigenesis, yet its upstream regulation remains poorly defined. Although considerable evidence supports the prevailing view that amino acids activate mTOR complex 1 but not mTORC2, several studies reported paradoxical activation of mTORC2 signaling by amino acids. We noted that after amino acid starvation of cells in culture, addition of an amino acid solution increased mTORC2 signaling. Interestingly, we found the pH of the amino acid solution to be alkaline, ∼pH 10. These observations led us to discover and demonstrate here that alkaline intracellular pH (pHi) represents a previously unknown activator of mTORC2. Using a fluorescent pH-sensitive dye (cSNARF1-AM) coupled with live-cell imaging, we demonstrate that culturing cells in media at an alkaline pH induces a rapid rise in the pHi, which increases mTORC2 catalytic activity and downstream signaling to the pro-growth and pro-survival kinase Akt. Alkaline pHi also activates AMPK, a canonical sensor of energetic stress. Functionally, alkaline pHi activates AMPK-mTOR signaling, which attenuates apoptosis caused by growth factor withdrawal. Collectively, these findings reveal that alkaline pHi increases mTORC2- and AMPK-mediated signaling to promote cell survival during conditions of growth factor limitation, analogous to the demonstrated ability of energetic stress to activate AMPK–mTORC2 and promote cell survival. As an elevated pHi represents an underappreciated hallmark of cancer cells, we propose that the alkaline pHi stress sensing by AMPK–mTORC2 may contribute to tumorigenesis by enabling cancer cells at the core of a growing tumor to evade apoptosis and survive.

• AMPK
• Akt
• intracellular pH (pHi)
• mTORC2

The mammalian/mechanistic target of rapamycin complex 1 (mTORC1) is activated by the small G-protein, Ras homolog enriched in brain (RHEB–GTPase). On lysosome, RHEB activates mTORC1 by binding the domains of N-heat, M-heat, and the focal adhesion targeting (FAT) domain, which allosterically regulates ATP binding in the active site for further phosphorylation. The crucial role of RHEB in regulating growth and survival through mTORC1 makes it a targetable site for anti-cancer therapeutics. However, the binding kinetics of RHEB to mTORC1 is still unknown at the molecular level. Therefore, we studied the kinetics by in vitro and in-cell protein–protein interaction (PPI) assays. To this end, we used the split-luciferase system (NanoBiT^®) for in-cell studies and prepared proteins for the in vitro measurements. Consequently, we demonstrated that RHEB binds to the whole mTOR both in the presence or absence of GTPγS, with five-fold weaker affinity in the presence of GTPγS. In addition, RHEB bound to the truncated mTOR fragments of N-heat domain (∆N, aa 60–167) or M-heat domain (∆M, aa 967–1023) with the same affinity in the absence of GTP. The reconstructed binding site of RHEB, ∆N-FAT-M, however, bound to RHEB with the same affinity as ∆N-M, indicating that the FAT domain (∆FAT, aa 1240–1360) is dispensable for RHEB binding. Furthermore, RHEB bound to the truncated kinase domain (∆ATP, aa 2148–2300) with higher affinity than to ∆N-FAT-M. In conclusion, RHEB engages two different binding sites of mTOR, ∆N-FAT-M and ∆ATP, with higher affinity for ∆ATP, which likely regulates the kinase activity of mTOR through multiple different biding modes.

• G-Protein
• RHEB
• allosteric activation
• binding kinetics
• kinase domain
• mTORC1

• Binding Sites
• HEK293 Cells
• Humans
• In Vitro Techniques
• Kinetics
• Mechanistic Target of Rapamycin Complex 1/genetics
• Mechanistic Target of Rapamycin Complex 1/metabolism
• Phosphorylation
• Protein Interaction Domains and Motifs
• Ras Homolog Enriched in Brain Protein/genetics
• Ras Homolog Enriched in Brain Protein/metabolism

• African swine fever
• DNA virus
• host-pathogen interactions
• immune evasion
• transcription

• Amino acids
• Arginine
• Autophagosome
• Autophagy
• Calcium/calmodulin-dependent protein kinase kinase
• Leucine
• Lysosome
• Mammalian target of rapamycin complex 1
• Rag GTPase
• Rheb

Tuberous sclerosis complex (TSC) is caused by mutations in TSC1 or TSC2 gene and affects multiple organs, including the kidney, where it presents with angiomyolipomata and cysts that can result in kidney failure. The factors promoting cyst formation and tumor growth in TSC are incompletely understood. Current studies demonstrate that kidney cyst epithelia in TSC mouse models and in humans with TSC are composed of hyperproliferating intercalated cells, along with activation of H⁺-ATPase and carbonic anhydrase 2. Interfering with intercalated cell proliferation completely inhibited and inactivating carbonic anhydrase 2 significantly protected against cyst formation in TSC. Targeting the acid base and/or electrolyte transporters of intercalated cells may provide a therapeutic approach for the treatment of kidney cysts in TSC.

Tuberous sclerosis complex (TSC) is caused by mutations in either TSC1 or TSC2 genes and affects multiple organs, including kidney, lung, and brain. In the kidney, TSC presents with the enlargement of benign tumors (angiomyolipomata) and cysts, which eventually leads to kidney failure. The factors promoting cyst formation and tumor growth in TSC are incompletely understood. Here, we report that mice with principal cell-specific inactivation of Tsc1 develop numerous cortical cysts, which are overwhelmingly composed of hyperproliferating A-intercalated (A-IC) cells. RNA sequencing and confirmatory expression studies demonstrated robust expression of Forkhead Transcription Factor 1 (Foxi1) and its downstream targets, apical H⁺-ATPase and cytoplasmic carbonic anhydrase 2 (CAII), in cyst epithelia in Tsc1 knockout (KO) mice but not in Pkd1 mutant mice. In addition, the electrogenic 2Cl⁻/H⁺ exchanger (CLC-5) is significantly up-regulated and shows remarkable colocalization with H⁺-ATPase on the apical membrane of cyst epithelia in Tsc1 KO mice. Deletion of Foxi1, which is vital to intercalated cells viability and H⁺-ATPase expression, completely abrogated the cyst burden in Tsc1 KO mice, as indicated by MRI images and histological analysis in kidneys of Foxi1/Tsc1 double-knockout (dKO) mice. Deletion of CAII, which is critical to H⁺-ATPase activation, caused significant reduction in cyst burden and increased life expectancy in CAII/Tsc1 dKO mice vs. Tsc1 KO mice. We propose that intercalated cells and their acid/base/electrolyte transport machinery (H⁺-ATPase/CAII/CLC-5) are critical to cystogenesis, and their inhibition or inactivation is associated with significant protection against cyst generation and/or enlargement in TSC.

• H+-ATPase
• cortical collecting duct
• cysts
• intercalated cells
• prorenin receptor

Skeletal muscle protein synthesis is a highly complex process, influenced by nutritional status, mechanical stimuli, repair programs, hormones, and growth factors. The molecular aspects of protein synthesis are centered around the mTORC1 complex. However, the intricacies of mTORC1 regulation, both up and downstream, have expanded overtime. Moreover, the plastic nature of skeletal muscle makes it a unique tissue, having to coordinate between temporal changes in myofiber metabolism and hypertrophy/atrophy stimuli within a tissue with considerable protein content. Skeletal muscle manages the push and pull between anabolic and catabolic pathways through key regulatory proteins to promote energy production in times of nutrient deprivation or activate anabolic pathways in times of nutrient availability and anabolic stimuli. Branched-chain amino acids (BCAAs) can be used for both energy production and signaling to induce protein synthesis. The metabolism of BCAAs occur in tandem with energetic and anabolic processes, converging at several points along their respective pathways. The fate of intramuscular BCAAs adds another layer of regulation, which has consequences to promote or inhibit muscle fiber protein anabolism. This review will outline the general mechanisms of muscle protein synthesis and describe how metabolic pathways can regulate this process. Lastly, we will discuss how BCAA availability and demand coordinate with synthesis mechanisms and identify key factors involved in intramuscular BCAA trafficking.

• AMPK (5′-AMP activated kinase)
• BCKD
• branch chain amino acids
• branched-chain α-ketoacid dehydrogenase
• mammalian target of rapamycin
• protein synthesis
• skeletal muscle

• Rheb
• breast
• cancer
• mTOR
• mutation
• tumorigenesis

Deposition of amyloid beta plaques in adult rat or human brain is associated with increased production of proinflammatory cytokines by associated glial cells that are responsible for degeneration of the diseased tissue. The expression of these cytokines is usually under check and is controlled at the post-transcriptional level via several microRNAs. Computational analysis of gene expression profiles of cortical regions of Alzheimer’s disease patients’ brain suggests ineffective target cytokine mRNA suppression by existing micro-ribonucleoproteins (miRNPs) in diseased brain. Exploring the mechanism of amyloid beta-induced cytokine expression, we have identified how the inactivation of the repressive miR-146 miRNPs causes increased production of cytokines in amyloid beta-exposed glial cells. In exploration of the cause of miRNP inactivation, we have noted amyloid beta oligomer-induced sequestration of the mTORC1 complex to early endosomes that results in decreased Ago2 phosphorylation, limited Ago2-miRNA uncoupling, and retarded Ago2-cytokine mRNA interaction in rat astrocytes. Interestingly, constitutive activation of mTORC1 by Rheb activator restricts proinflammatory cytokine production by reactivating miR-146 miRNPs in amyloid beta-exposed glial cells to rescue the disease phenotype in the in vivo rat model of Alzheimer’s disease.

• Alzheimer’s disease
• Astrocyte
• Endosome
• Rheb
• amyloid beta
• cognition
• cytokines
• mTORC1 activation
• miRNAs
• neuroinflammation

Caloric restriction (CR), the reduction of caloric intake without inducing malnutrition, is the most reproducible method of extending health and lifespan across numerous organisms, including humans. However, with nearly one-third of the world’s population overweight, it is obvious that caloric restriction approaches are difficult for individuals to achieve. Therefore, identifying compounds that mimic CR is desirable to promote longer, healthier lifespans without the rigors of restricting diet. Many compounds, such as rapamycin (and its derivatives), metformin, or other naturally occurring products in our diets (nutraceuticals), induce CR-like states in laboratory models. An alternative to CR is the removal of specific elements (such as individual amino acids) from the diet. Despite our increasing knowledge of the multitude of CR approaches and CR mimetics, the extent to which these strategies overlap mechanistically remains unclear. Here we provide an update of CR and CR mimetic research, summarizing mechanisms by which these strategies influence genome function required to treat age-related pathologies and identify the molecular fountain of youth.

• amino acid restriction
• caloric restriction
• caloric restriction mimetics
• general control nonderepressible 2 (GCN2)
• healthspan
• lifespan
• mammalian target of rapamycin (mTOR)

• Amino Acids/genetics
• Animals
• Blood-Brain Barrier/metabolism
• Blood-Brain Barrier/pathology
• Electrophysiological Phenomena/genetics
• Embryonic Development/genetics
• Humans
• Large Neutral Amino Acid-Transporter 1/genetics
• Mice
• Microcephaly/genetics
• Microcephaly/pathology
• Neural Stem Cells/metabolism
• Neural Stem Cells/pathology
• Neurons/metabolism
• Neurons/pathology
• Olfactory Bulb/growth & development
• Olfactory Bulb/pathology
• Seizures/genetics
• Seizures/pathology
• Sequence Deletion/genetics
• TOR Serine-Threonine Kinases/antagonists & inhibitors
• TOR Serine-Threonine Kinases/genetics

• R15 NS096562 NINDS NIH HHS
• National Institutes of Health

The mammalian target of rapamycin (mTOR) is an evolutionary conserved Ser/Thr protein kinase that senses multiple upstream stimuli to control cell growth, metabolism, and autophagy. mTOR is the catalytic subunit of mTOR complex 1 (mTORC1). A significant amount of research has uncovered the signaling pathways regulated by mTORC1, and the involvement of these signaling cascades in human diseases like cancer, diabetes, and ageing. Here, we review advances in mTORC1 regulation by upstream stimuli. We specifically focus on how growth factors, amino acids, G-protein coupled receptors (GPCRs), phosphorylation, and small GTPases regulate mTORC1 activity and signaling.

• G-protein coupled receptors
• amino acids
• and autophagy
• cell growth
• kinases
• mTORC1
• metabolism
• phosphorylation
• small GTPases

• Amino Acids/genetics
• Amino Acids/metabolism
• Animals
• Humans
• Mechanistic Target of Rapamycin Complex 1/genetics
• Mechanistic Target of Rapamycin Complex 1/metabolism
• Phosphorylation/genetics
• Receptors, G-Protein-Coupled/genetics
• Receptors, G-Protein-Coupled/metabolism
• Signal Transduction/genetics

• R01 GM129097 NIGMS NIH HHS
• R01GM129097-01 NIH HHS

The mechanistic target of rapamycin complex 1 (mTORC1) is an essential regulator of cell growth and metabolism through the modulation of protein and lipid synthesis, lysosome biogenesis, and autophagy. The activity of mTORC1 is dynamically regulated by several environmental cues, including amino acid availability, growth factors, energy levels, and stresses, to coordinate cellular status with environmental conditions. Dysregulation of mTORC1 activity is closely associated with various diseases, including diabetes, cancer, and neurodegenerative disorders. The discovery of Rag GTPases has greatly expanded our understanding of the regulation of mTORC1 activity by amino acids, especially leucine and arginine. In addition to Rag GTPases, other factors that also contribute to the modulation of mTORC1 activity have been identified. In this review, we discuss the mechanisms of regulation of mTORC1 activity by particular amino acids.

• Amino acids
• Intracellular Ca2+ concentration
• Rag GTPases
• Rheb GTPase
• mTOR
• mTORC1

• Autophagy
• Fetal growth restriction
• Pathological mechanism
• Physiological regulation
• Preeclampsia
• Pregnancy
• Premature birth

A complex molecular machinery converges on the surface of lysosomes to ensure that the growth-promoting signaling mediated by mechanistic target of rapamycin complex 1 (mTORC1) is tightly controlled by the availability of nutrients and growth factors. The final step in this activation process is dependent on Rheb, a small GTPase that binds to mTOR and allosterically activates its kinase activity. Here we review the mechanisms that determine the subcellular localization of Rheb (and the closely related RhebL1 protein) as well as the significance of these mechanisms for controlling mTORC1 activation. In particular, we explore how the relatively weak membrane interactions conferred by C-terminal farnesylation are critical for the ability of Rheb to activate mTORC1. In addition to supporting transient membrane interactions, Rheb C-terminal farnesylation also supports an interaction between Rheb and the δ subunit of phosphodiesterase 6 (PDEδ). This interaction provides a potential mechanism for targeting Rheb to membranes that contain Arl2, a small GTPase that triggers the release of prenylated proteins from PDEδ. The minimal membrane targeting conferred by C-terminal farnesylation of Rheb and RhebL1 distinguishes them from other members of the Ras superfamily that possess additional membrane interaction motifs that work with farnesylation for enrichment on the specific subcellular membranes where they engage key effectors. Finally, we highlight diversity in Rheb membrane targeting mechanisms as well as the potential for alternative mTORC1 activation mechanisms across species.

• Rheb
• cancer
• lysosome
• mTOR
• membranes
• signaling

• MTOR
• MTORC1
• Ral
• RalGAP
• TSC
• Tuberous sclerosis complex

• C. elegans
• dauer
• developmental arrest
• developmental rate
• insulin
• nutrient sensing
• target of rapamycin

• amino acid
• growth
• infant
• nutrient sensing
• protein synthesis

• C. elegans
• diet
• gut microbiota
• metabolites

• Amino acids
• Mammalian target of rapamycin (mTOR)
• Protein synthesis
• eEF2
• eIF2

Knowledge of protein signalling pathways in the working cell is seen as a primary route to identifying and developing targeted medicines. In recent years there has been a growing awareness of the importance of the mTOR pathway, making it an attractive target for therapeutic intervention in several diseases. Within this pathway we have focused on S6 kinase 1 (S6K1), the downstream phosphorylation substrate of mTORC1, and specifically identify its juxtaposition with mTORC1. When S6K1 is co-expressed with raptor we show that S6K1 is translocated from the nucleus to the cytoplasm. By developing a novel biosensor we demonstrate in real-time, that phosphorylation and de-phosphorylation of S6K1 occurs mainly in the cytoplasm of living cells. Furthermore, we show that the scaffold protein raptor, that typically recruits mTOR substrates, is not always involved in S6K1 phosphorylation. Overall, we demonstrate how FRET-FLIM imaging technology can be used to show localisation of S6K1 phosphorylation in living cells and hence a key site of action of inhibitors targeting mTOR phosphorylation.

• Humans
• Mechanistic Target of Rapamycin Complex 1/metabolism
• Metabolism/physiology
• Signal Transduction/physiology

• R35 CA197459 NCI NIH HHS
• P01 CA120964 NCI NIH HHS

• 4E-BP
• AKT1S1
• EIF4EBP1
• MTOR
• PRAS40
• Raptor
• Rheb
• S6K1B
• mLst8
• p70 S6 kinase

• PI3K
• aging
• anticancer
• kinase inhibitors
• mTOR

• translation initiation
• protein synthesis
• redd
• growth
• newborn

• Copepods
• Ectoparasite
• Egg development
• Egg maturation
• RNA interference
• Sea lice

Dysregulation of RNA polymerase I (Pol I)-dependent ribosomal DNA (rDNA) transcription is a consistent feature of malignant transformation that can be targeted to treat cancer. Understanding how rDNA transcription is coupled to the availability of growth factors and nutrients will provide insight into how ribosome biogenesis is maintained in a tumour environment characterised by limiting nutrients. We demonstrate that modulation of rDNA transcription initiation, elongation and rRNA processing is an immediate, co-regulated response to altered amino acid abundance, dependent on both mTORC1 activation of S6K1 and MYC activity. Growth factors regulate rDNA transcription initiation while amino acids modulate growth factor-dependent rDNA transcription by primarily regulating S6K1-dependent rDNA transcription elongation and processing. Thus, we show for the first time amino acids regulate rRNA synthesis by a distinct, post-initiation mechanism, providing a novel model for integrated control of ribosome biogenesis that has implications for understanding how this process is dysregulated in cancer.

• Gerotarget
• MYC
• S6K1
• amino acids
• rDNA transcription

• autophagy
• cancer
• mTOR
• signaling