Tti1 and Tel2 are critical factors in mammalian target of rapamycin complex assembly

5-HT6 receptors: Contemporary views on their neurobiological and pharmacological relevance in neuropsychiatric disorders

Despite the relatively limited number of serotonergic neurons in humans, serotonin plays a key role in neurophysiological functions, including sleep, pain perception, learning, memory, cognition, emotion, reward, and mood regulation. Altered serotonergic neurotransmission is linked to conditions such as anxiety, depression, anorexia, migraine, insomnia, schizophrenia, Alzheimer's disease (AD), and cognitive impairments. The 5-HT6 receptor (5-HT6R), mainly found in brain regions involved in cognition, is a promising therapeutic target for cognitive deficits in neuropsychiatric disorders, particularly AD and schizophrenia. Preclinical studies have shown that 5-HT6R antagonists improve cognitive function. 5-HT6R interacts dynamically with an extensive intracellular protein network, regulating the localisation, trafficking, and signalling of these proteins. Proteomic and genetic studies have revealed interactions with mTOR kinase and neurofibromin, both of which are crucial for synaptic plasticity, learning, and memory. Fyn kinase is also associated with 5-HT6Rs, reinforcing receptor expression and G-protein coupling. Notably, the G protein-regulated inducer of neurite outgrowth 1 (GPRIN1) interacts with 5-HT6Rs independently of agonists, enhancing receptor activity. This review highlights the clinical testing of 5-HT6R ligands as regulators of these complex signalling properties, underscoring their therapeutic potential in addressing cognitive impairments associated with neuropsychiatric disorders.

Direct sensing of dietary ω-6 linoleic acid through FABP5-mTORC1 signaling

Diet influences macronutrient availability to cells, and although mechanisms of sensing dietary glucose and amino acids are well characterized, less is known about sensing lipids. We defined a nutrient signaling mechanism involving fatty acid-binding protein 5 (FABP5) and mechanistic target of rapamycin complex 1 (mTORC1) that is activated by the essential polyunsaturated fatty acid (PUFA) ω-6 linoleic acid (LA). FABP5 directly bound to the regulatory-associated protein of mTOR (Raptor) to enhance formation of functional mTORC1 and substrate binding, ultimately converging on increased mTOR signaling and proliferation. The amounts of FABP5 protein were increased in tumors and serum from triple-negative compared with those from receptor-positive breast cancer patients, which highlights its potential role as a biomarker that mediates cellular responses to ω-6 LA intake in this disease subtype.

Targeting mTOR Kinase with Natural Compounds: Potent ATP-Competitive Inhibition Through Enhanced Binding Mechanisms

Background/Objectives: The mammalian target of the rapamycin (mTOR) signaling pathway is a central regulator of cell growth, proliferation, metabolism, and survival. Dysregulation of mTOR signaling contributes to many human diseases, including cancer, diabetes, and obesity. Therefore, inhibitors against mTOR's catalytic kinase domain (KD) have been developed and have shown significant antitumor activities, making it a promising therapeutic target. The ATP-KD interaction is particularly important for mTOR to exert its cellular functions, and such inhibitors have demonstrated efficient attenuation of overall mTOR activity. Methods: In this study, we screened the Traditional Chinese Medicine (TCM) database, which enlists natural products that capture the relationships between drugs targets and diseases. Our aim was to identify potential ATP-competitive agonists that target the mTOR-KD and compete with ATP to bind the mTOR-KD serving as potential potent mTOR inhibitors. Results: We identified two compounds that demonstrated interatomic interactions similar to those of ATP-mTOR. The conformational stability and dynamic features of the mTOR-KD bound to the selected compounds were tested by subjecting each complex to 200 ns molecular dynamic (MD) simulations and molecular mechanics/generalized Born surface area (MM/GBSA) to extract free binding energies. We show the effectiveness of both compounds in forming stable complexes with the mTOR-KD, which is more effective than the mTOR-KD-ATP complex with more robust binding affinities. Conclusions: This study implies that both compounds could serve as potential therapeutic inhibitors of mTOR, regulating its function and, therefore, mitigating human disease progression.

Beclin-1: a therapeutic target at the intersection of autophagy, immunotherapy, and cancer treatment

The significant identification of Beclin-1's function in regulating autophagy flow signified a significant progression in our understanding of cellular operations. Beclin-1 acts as a scaffold for forming the PI3KC3 complex, controlling autophagy and cellular trafficking processes in a complicated way. This intricate protein has garnered considerable attention due to its substantial impact on the development of tumors. Strong evidence indicates Beclin-1 plays a critical role in controlling autophagy in various human cancer types and its intricate connection with apoptosis and ferroptosis. The potential of Beclin-1 as a viable target for cancer therapy is highlighted by its associations with key autophagy regulators such as AMPK, mTOR, and ATGs. Beclin-1 controls the growth and dissemination of tumors by autophagy. It also affects how tumors react to therapies such as chemotherapy and radiation therapy. The role of Beclin-1 in autophagy can influence apoptosis, depending on whether it supports cell survival or leads to cell death. Beclin-1 plays a crucial role in ferroptosis by increasing ATG5 levels, which in turn promotes autophagy-triggered ferroptosis. Finally, we analyzed the possible function of Beclin-1 in tumor immunology and drug sensitivity in cancers. In general, Beclin-1 has a significant impact on regulating autophagy, offering various potentials for medical intervention and altering our understanding of cancer biology.

Targeting the mTOR-Autophagy Axis: Unveiling Therapeutic Potentials in Osteoporosis

Osteoporosis (OP) is a widespread age-related disorder marked by decreased bone density and increased fracture risk, presenting a significant public health challenge. Central to the development and progression of OP is the dysregulation of the mechanistic target of the rapamycin (mTOR)-signaling pathway, which plays a critical role in cellular processes including autophagy, growth, and proliferation. The mTOR-autophagy axis is emerging as a promising therapeutic target due to its regulatory capacity in bone metabolism and homeostasis. This review aims to (1) elucidate the role of mTOR signaling in bone metabolism and its dysregulation in OP, (2) explore the interplay between mTOR and autophagy in the context of bone cell activity, and (3) assess the therapeutic potential of targeting the mTOR pathway with modulators as innovative strategies for OP treatment. By examining the interactions among autophagy, mTOR, and OP, including insights from various types of OP and the impact on different bone cells, this review underscores the complexity of mTOR's role in bone health. Despite advances, significant gaps remain in understanding the detailed mechanisms of mTOR's effects on autophagy and bone cell function, highlighting the need for comprehensive clinical trials to establish the efficacy and safety of mTOR inhibitors in OP management. Future research directions include clarifying mTOR's molecular interactions with bone metabolism and investigating the combined benefits of mTOR modulation with other therapeutic approaches. Addressing these challenges is crucial for developing more effective treatments and improving outcomes for individuals with OP, thereby unveiling the therapeutic potentials of targeting the mTOR-autophagy axis in this prevalent disease.

mTOR in the Development of Hypoxic Pulmonary Hypertension Associated with Cardiometabolic Risk Factors

The pathophysiology of pulmonary hypertension is complex and multifactorial. It is a disease characterized by increased pulmonary vascular resistance at the level due to sustained vasoconstriction and remodeling of the pulmonary arteries, which triggers an increase in the mean pulmonary artery pressure and subsequent right ventricular hypertrophy, which in some cases can cause right heart failure. Hypoxic pulmonary hypertension (HPH) is currently classified into Group 3 of the five different groups of pulmonary hypertensions, which are determined according to the cause of the disease. HPH mainly develops as a product of lung diseases, among the most prevalent causes of obstructive sleep apnea (OSA), chronic obstructive pulmonary disease (COPD), or hypobaric hypoxia due to exposure to high altitudes. Additionally, cardiometabolic risk factors converge on molecular mechanisms involving overactivation of the mammalian target of rapamycin (mTOR), which correspond to a central axis in the development of HPH. The aim of this review is to summarize the role of mTOR in the development of HPH associated with metabolic risk factors and its therapeutic alternatives, which will be discussed in this review.

Prognostic analysis of patients with gastric cancer based on N6-methyladenosine modification patterns and tumor microenvironment characterization

Background

Cancers arise from genetic and epigenetic abnormalities that affect oncogenes and tumor suppressor genes, compounded by gene mutations. The N6-methyladenosine (m6A) RNA modification, regulated by methylation regulators, has been implicated in tumor proliferation, differentiation, tumorigenesis, invasion, and metastasis. However, the role of m6A modification patterns in the tumor microenvironment of gastric cancer (GC) remains poorly understood.

Materials and methods

In this study, we analyzed m6A modification patterns in 267 GC samples utilizing 31 m6A regulators. Using consensus clustering, we identified two unique subgroups of GC. Patients with GC were segregated into high- and low-infiltration cohorts to evaluate the infiltration proportions of the five prognostically significant immune cell types. Leveraging the differential genes in GC, we identified a "green" module via Weighted Gene Co-expression Network Analysis. A risk prediction model was established using the LASSO regression method.

Results

The "green" module was connected to both the m6A RNA methylation cluster and immune infiltration patterns. Based on "Module Membership" and "Gene Significance", 37 hub genes were identified, and a risk prediction model incorporating nine hub genes was established. Furthermore, methylated RNA immunoprecipitation and RNA Immunoprecipitation assays revealed that YTHDF1 elevated the expression of DNMT3B, which synergistically promoted the initiation and development of GC. We elucidated the molecular mechanism underlying the regulation of DNMT3B by YTHDF1 and explored the crosstalk between m6A and 5mC modification.

Conclusion

m6A RNA methylation regulators are instrumental in malignant progression and the dynamics of tumor microenvironment infiltration of GC. Assessing m6A modification patterns and tumor microenvironment infiltration characteristics in patients with GC holds promise as a valuable prognostic biomarker.

The first Iranian patient with You-Hoover-Fong syndrome and a review of the literature on 27 cases: expanding the genotypic and phenotypic spectrum

BACKGROUND

The ultra-rare autosomal recessive genetic disorder, You-Hoover-Fong Syndrome (YHFS), is caused by defects in the TELO2 gene and is characterized by intellectual disability, developmental delay, and ocular impairments. This study aims to contribute to a better understanding of YHFS by reviewing previous cases and introducing a novel variant in a new case.

METHODS

Whole exome sequencing (WES) was conducted on the proband to identify genetic variants, and Sanger sequencing was used to confirm variants within the family. This article presents a comprehensive collection of reported cases of YHFS, incorporating both molecular and clinical data, through an extensive literature search and analysis of English-language studies published until June 2023.

RESULTS

Using WES, a novel homozygous missense variant, c.1799A > G (p. Tyr600Cys), was identified in the TELO2 gene in a 4-year-old Iranian male patient. Novel clinical features, including choanal atresia and clubfoot, were also identified. A comprehensive literature review identified 27 patients with YHFS, with 20 variants in the TELO2 gene. Missense pathogenic variants were the most common type of pathogenic variant, and the most common features were microcephaly and intellectual impairment.

CONCLUSION

This study presents the first case of pathogenic variants in TELO2 gene in Iran, expands the genotypic and phenotypic spectrum of YHFS and contributes to the growing body of literature pertaining to YHFS. Furthermore, our findings highlight the importance of genetic testing for non-consanguineous carrier screening, as compound heterozygosity may be a significant factor in the development of YHFS. Further research is needed to clarify the molecular mechanisms underlying YHFS pathogenesis.

Targeting mTOR signaling pathways in multiple myeloma: biology and implication for therapy

Multiple Myeloma (MM), a cancer of terminally differentiated plasma cells, is the second most prevalent hematological malignancy and is incurable due to the inevitable development of drug resistance. Intense protein synthesis is a distinctive trait of MM cells, supporting the massive production of clonal immunoglobulins or free light chains. The mammalian target of rapamycin (mTOR) kinase is appreciated as a master regulator of vital cellular processes, including regulation of metabolism and protein synthesis, and can be found in two multiprotein complexes, mTORC1 and mTORC2. Dysregulation of these complexes is implicated in several types of cancer, including MM. Since mTOR has been shown to be aberrantly activated in a large portion of MM patients and to play a role in stimulating MM cell survival and resistance to several existing therapies, understanding the regulation and functions of the mTOR complexes is vital for the development of more effective therapeutic strategies. This review provides a general overview of the mTOR pathway, discussing key discoveries and recent insights related to the structure and regulation of mTOR complexes. Additionally, we highlight findings on the mechanisms by which mTOR is involved in protein synthesis and delve into mTOR-mediated processes occurring in MM. Finally, we summarize the progress and current challenges of drugs targeting mTOR complexes in MM.

mTOR: Its Critical Role in Metabolic Diseases, Cancer, and the Aging Process

The mammalian target of rapamycin (mTOR) is a pivotal regulator, integrating diverse environmental signals to control fundamental cellular functions, such as protein synthesis, cell growth, survival, and apoptosis. Embedded in a complex network of signaling pathways, mTOR dysregulation is implicated in the onset and progression of a range of human diseases, including metabolic disorders such as diabetes and cardiovascular diseases, as well as various cancers. mTOR also has a notable role in aging. Given its extensive biological impact, mTOR signaling is a prime therapeutic target for addressing these complex conditions. The development of mTOR inhibitors has proven advantageous in numerous research domains. This review delves into the significance of mTOR signaling, highlighting the critical components of this intricate network that contribute to disease. Additionally, it addresses the latest findings on mTOR inhibitors and their clinical implications. The review also emphasizes the importance of developing more effective next-generation mTOR inhibitors with dual functions to efficiently target the mTOR pathways. A comprehensive understanding of mTOR signaling will enable the development of effective therapeutic strategies for managing diseases associated with mTOR dysregulation.

Exercise, mTOR Activation, and Potential Impacts on the Liver in Rodents

The literature offers a consensus on the association between exercise training (ET) protocols based on the adequate parameters of intensity and frequency, and several adaptive alterations in the liver. Indeed, regular ET can reverse glucose and lipid metabolism disorders, especially from aerobic modalities, which can decrease intrahepatic fat formation. In terms of molecular mechanisms, the regulation of hepatic fat formation would be directly related to the modulation of the mechanistic target of rapamycin (mTOR), which would be stimulated by insulin signaling and Akt activation, from the following three different primary signaling pathways: (I) growth factor, (II) energy/ATP-sensitive, and (III) amino acid-sensitive signaling pathways, respectively. Hyperactivation of the Akt/mTORC1 pathway induces lipogenesis by regulating the action of sterol regulatory element binding protein-1 (SREBP-1). Exercise training interventions have been associated with multiple metabolic and tissue benefits. However, it is worth highlighting that the mTOR signaling in the liver in response to exercise interventions remains unclear. Hepatic adaptive alterations seem to be most outstanding when sustained by chronic interventions or high-intensity exercise protocols.

Comparative Analysis of the Growth, Physiological Responses, and Gene Expression of Chinese Soft-Shelled Turtles Cultured in Different Modes

The Chinese soft-shelled turtle (Pelodiscus sinensis) is an important freshwater aquaculture turtle due to its taste and nutritional and medicinal value. More ecological culturing modes, such as rice-turtle co-culture, should be developed to meet the ecological benefit demand. We compared growth, physiological parameters, and transcriptome data to detect the physiological responses and regulatory mechanisms of pond-cultured turtles as compared to co-cultured turtles. The co-cultured turtles grew slower than pond-cultured turtles. The gonadosomatic index of co-cultured male turtles was lower than that of pond-cultured male turtles, and both the mesenteric fat index and limb fat index were lower in co-cultured turtles than in pond-cultured turtles (p < 0.05). The blood GLU of the co-cultured turtles was significantly lower than the GLU of the pond-cultured turtles (p < 0.05), while the values of CRE, UA, BUN, AKP, ACP, GOT, and CAT were higher in the co-cultured turtles than in the pond-cultured turtles (p < 0.05). In total, 246 and 598 differentially expressed genes (DEGs) were identified in the brain and gut from turtles cultured in the two different modes, respectively. More DEGs were related to environmental information processing, metabolism, and human diseases. In the brain, the top enriched pathways of DEGs included the longevity regulating pathway, glycerolipid metabolism, cytokine-cytokine receptor interaction, Toll-like receptor signaling pathway, and PI3K-Akt signaling pathway, while in the gut, the top enriched pathways of DEGs included the cell cycle, DNA replication, cellular senescence, and p53 signaling pathway. The turtles acclimated to the different culturing conditions by adjusting their growth, physiological, and biochemical characteristics and related gene expression during a short culture period.

Effects of low-dose rapamycin on lymphoid organs of mice prone and resistant to accelerated senescence

Aging is a complex, natural, and irreversible phenomenon that subjects the body to numerous changes in the physiological process, characterized by a gradual decline in the organism's homeostatic mechanisms, closely related to immunosenescence. Here, we evaluated the regulation of immunosenescence in lymphoid organs of senescence-accelerated prone 8 (SAM-P8) and senescence-accelerated resistant 1 (SAM-R1) mice treated with a low dose of rapamycin (RAPA). Mice were treated with a dose of 7.1 µg/kg RAPA for 2 months and had body mass and hematological parameters analyzed prior and during treatment. Cellular and humoral parameters of serum, bone marrow, thymus, and spleen samples were evaluated by ELISA, histology, and flow cytometry. Changes in body mass, hematological parameters, cell number, and in the secretion of IL-1β, IL-6, TNF-α, IL-7, and IL-15 cytokines were different between the 2 models used. In histological analyses, we observed that SAM-P8 mice showed faster thymic involution than SAM-R1 mice. Regarding the T lymphocyte subpopulations in the spleen, CD4+ and CD8+ T cell numbers were higher and lower, respectively, in SAM-P8 mice treated with RAPA, with the opposite observed in SAM-R1. Additionally, we found that the low dose of RAPA used did not trigger changes that could compromise the immune response of these mice and the administered dose may have contributed to changes in important lymphocyte populations in the adaptive immune response and the secretion of cytokines that directly collaborate with the maturation and proliferation of these cells.

The mTORC2 signaling network: targets and cross-talks

The mechanistic target of rapamycin, mTOR, controls cell metabolism in response to growth signals and stress stimuli. The cellular functions of mTOR are mediated by two distinct protein complexes, mTOR complex 1 (mTORC1) and mTORC2. Rapamycin and its analogs are currently used in the clinic to treat a variety of diseases and have been instrumental in delineating the functions of its direct target, mTORC1. Despite the lack of a specific mTORC2 inhibitor, genetic studies that disrupt mTORC2 expression unravel the functions of this more elusive mTOR complex. Like mTORC1 which responds to growth signals, mTORC2 is also activated by anabolic signals but is additionally triggered by stress. mTORC2 mediates signals from growth factor receptors and G-protein coupled receptors. How stress conditions such as nutrient limitation modulate mTORC2 activation to allow metabolic reprogramming and ensure cell survival remains poorly understood. A variety of downstream effectors of mTORC2 have been identified but the most well-characterized mTORC2 substrates include Akt, PKC, and SGK, which are members of the AGC protein kinase family. Here, we review how mTORC2 is regulated by cellular stimuli including how compartmentalization and modulation of complex components affect mTORC2 signaling. We elaborate on how phosphorylation of its substrates, particularly the AGC kinases, mediates its diverse functions in growth, proliferation, survival, and differentiation. We discuss other signaling and metabolic components that cross-talk with mTORC2 and the cellular output of these signals. Lastly, we consider how to more effectively target the mTORC2 pathway to treat diseases that have deregulated mTOR signaling.

Maturation and Assembly of mTOR Complexes by the HSP90-R2TP-TTT Chaperone System: Molecular Insights and Mechanisms

The mechanistic target of rapamycin (mTOR) is a master regulator of cell growth and metabolism, integrating environmental signals to regulate anabolic and catabolic processes, regulating lipid synthesis, growth factor-induced cell proliferation, cell survival, and migration. These activities are performed as part of two distinct complexes, mTORC1 and mTORC2, each with specific roles. mTORC1 and mTORC2 are elaborated dimeric structures formed by the interaction of mTOR with specific partners. mTOR functions only as part of these large complexes, but their assembly and activation require a dedicated and sophisticated chaperone system. mTOR folding and assembly are temporarily separated with the TELO2-TTI1-TTI2 (TTT) complex assisting the cotranslational folding of mTOR into a native conformation. Matured mTOR is then transferred to the R2TP complex for assembly of active mTORC1 and mTORC2 complexes. R2TP works in concert with the HSP90 chaperone to promote the incorporation of additional subunits to mTOR and dimerization. This review summarizes our current knowledge on how the HSP90-R2TP-TTT chaperone system facilitates the maturation and assembly of active mTORC1 and mTORC2 complexes, discussing interactions, structures, and mechanisms.

Assessing Trans-Inhibition of OATP1B1 and OATP1B3 by Calcineurin and/or PPIase Inhibitors and Global Identification of OATP1B1/3-Associated Proteins

Organic anion transporting polypeptide (OATP) 1B1 and OATP1B3 are key determinants of drug-drug interactions (DDIs). Various drugs including the calcineurin inhibitor (CNI) cyclosporine A (CsA) exert preincubation-induced trans-inhibitory effects upon OATP1B1 and/or OATP1B3 (abbreviated as OATP1B1/3) by unknown mechanism(s). OATP1B1/3 are phosphoproteins; calcineurin, which dephosphorylates and regulates numerous phosphoproteins, has not previously been investigated in the context of preincubation-induced trans-inhibition of OATP1B1/3. Herein, we compare the trans-inhibitory effects exerted on OATP1B1 and OATP1B3 by CsA, the non-analogous CNI tacrolimus, and the non-CNI CsA analogue SCY-635 in transporter-overexpressing human embryonic kidney (HEK) 293 stable cell lines. Preincubation (10-60 min) with tacrolimus (1-10 µM) rapidly and significantly reduces OATP1B1- and OATP1B3-mediated transport up to 0.18 ± 0.03- and 0.20 ± 0.02-fold compared to the control, respectively. Both CsA and SCY-635 can trans-inhibit OATP1B1, with the inhibitory effects progressively increasing over a 60 min preincubation time. At each equivalent preincubation time, CsA has greater trans-inhibitory effects toward OATP1B1 than SCY-635. Preincubation with SCY-635 for 60 min yielded IC50 of 2.2 ± 1.4 µM against OATP1B1, which is ~18 fold greater than that of CsA (0.12 ± 0.04 µM). Furthermore, a proteomics-based screening for protein interactors was used to examine possible proteins and processes contributing to OATP1B1/3 regulation and preincubation-induced inhibition by CNIs and other drugs. A total of 861 and 357 proteins were identified as specifically associated with OATP1B1 and OATP1B3, respectively, including various protein kinases, ubiquitin-related enzymes, the tacrolimus (FK506)-binding proteins FKBP5 and FKBP8, and several known regulatory targets of calcineurin. The current study reports several novel findings that expand our understanding of impaired OATP1B1/3 function; these include preincubation-induced trans-inhibition of OATP1B1/3 by the CNI tacrolimus, greater preincubation-induced inhibition by CsA compared to its non-CNI analogue SCY-635, and association of OATP1B1/3 with various proteins relevant to established and candidate OATP1B1/3 regulatory processes.

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

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

Intergenerational effects of early life-stage temperature modulation on gene expression and DNA methylation in Atlantic cod (Gadus morhua)

After suffering several collapses, the cod farming industry is now in the process of trying to re-establish itself. We have used material from Norway's National Cod Breeding Program to study how different early life-stage temperature regimes affect DNA methylation and gene expression. Long-term effects were detected by sampling fish several weeks after the end of differential treatments, and offspring from the different exposure groups was also sampled. Many overlapping genes were found between the different exposure groups and generations, coupled with genes associated with differential CpG methylation levels. Genes involved in muscle fibre development, general metabolic processes and formation of deformities were significantly affected, and genes relevant for intergenerational transfer of epigenetic marks were also detected. We believe the use of environmental cues can be a useful strategy for improving the production of Atlantic cod.

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.

TTT (Tel2-Tti1-Tti2) Complex, the Co-Chaperone of PIKKs and a Potential Target for Cancer Chemotherapy

The heterotrimeric Tel2-Tti1-Tti2 or TTT complex is essential for cell viability and highly observed in eukaryotes. As the co-chaperone of ATR, ATM, DNA-PKcs, mTOR, SMG1, and TRRAP, the phosphatidylinositol 3-kinase-related kinases (PIKKs) and a group of large proteins of 300-500 kDa, the TTT plays crucial roles in genome stability, cell proliferation, telomere maintenance, and aging. Most of the protein kinases in the kinome are targeted by co-chaperone Cdc37 for proper folding and stability. Like Cdc37, accumulating evidence has established the mechanism by which the TTT interacts with chaperone Hsp90 via R2TP (Rvb1-Rvb2-Tah1-Pih1) complex or other proteins for co-translational maturation of the PIKKs. Recent structural studies have revealed the α-solenoid structure of the TTT and its interactions with the R2TP complex, which shed new light on the co-chaperone mechanism and provide new research opportunities. A series of mutations of the TTT have been identified that cause disease syndrome with neurodevelopmental defects, and misregulation of the TTT has been shown to contribute to myeloma, colorectal, and non-small-cell lung cancers. Surprisingly, Tel2 in the TTT complex has recently been found to be a target of ivermectin, an antiparasitic drug that has been used by millions of patients. This discovery provides mechanistic insight into the anti-cancer effect of ivermectin and thus promotes the repurposing of this Nobel-prize-winning medicine for cancer chemotherapy. Here, we briefly review the discovery of the TTT complex, discuss the recent studies, and describe the perspectives for future investigation.

Bi-allelic TTI1 variants cause an autosomal-recessive neurodevelopmental disorder with microcephaly

Telomere maintenance 2 (TELO2), Tel2 interacting protein 2 (TTI2), and Tel2 interacting protein 1 (TTI1) are the three components of the conserved Triple T (TTT) complex that modulates activity of phosphatidylinositol 3-kinase-related protein kinases (PIKKs), including mTOR, ATM, and ATR, by regulating the assembly of mTOR complex 1 (mTORC1). The TTT complex is essential for the expression, maturation, and stability of ATM and ATR in response to DNA damage. TELO2- and TTI2-related bi-allelic autosomal-recessive (AR) encephalopathies have been described in individuals with moderate to severe intellectual disability (ID), short stature, postnatal microcephaly, and a movement disorder (in the case of variants within TELO2). We present clinical, genomic, and functional data from 11 individuals in 9 unrelated families with bi-allelic variants in TTI1. All present with ID, and most with microcephaly, short stature, and a movement disorder. Functional studies performed in HEK293T cell lines and fibroblasts and lymphoblastoid cells derived from 4 unrelated individuals showed impairment of the TTT complex and of mTOR pathway activity which is improved by treatment with Rapamycin. Our data delineate a TTI1-related neurodevelopmental disorder and expand the group of disorders related to the TTT complex.

TTI1 promotes non-small-cell lung cancer progression by regulating the mTOR signaling pathway

The role of TELO2-interacting protein 1 (TTI1) in the progression of several types of cancer has been reported recently. The aim of this study was to estimate the expression and potential value of TTI1 in non-small-cell lung cancer (NSCLC) patients. The expression of TTI1 and its prognostic value in NSCLC from The Cancer Genome Atlas (TCGA) database and Gene Expression Omnibus (GEO) database were analyzed. To verify the bioinformatics findings, a tissue microarray containing 160 NSCLC and paired peritumoral tissues from NSCLC patients was analyzed by immunohistochemistry for TTI1. Subsequently, the roles of TTI1 in NSCLC cells were investigated in vivo by establishing xenograft models in nude mice and in vitro by transwell, CCK-8, wound healing, and colony formation assays. In addition, quantitative real-time polymerase chain reaction and western blot were applied to explore the underlying mechanism by which TTI1 promotes tumor progression. Finally, the relationship between TTI1 and Ki67 expression level in NSCLC was probed, and Kaplan-Meier and Cox analyses were performed to assess the prognostic merit of TTI1 and Ki67 in NSCLC patients. We found that the expression of TTI1 was significantly upregulated in NSCLC tissues compared to paired peritumoral tissues, which coincides with the bioinformatics findings from the TCGA and GEO databases. TTI1 was highly expressed in NSCLC patients with large tumors, advanced tumor stage, and lymphatic metastasis. In addition, the prognostic analysis identified TTI1 as an independent indication for poor prognosis of NSCLC patients. In vitro, upregulation of TTI1 in NSCLC cells could facilitate cell invasion, metastasis, viability, and proliferation. Mechanistically, our study verified that TTI1 could regulate mTOR activity, which has a pivotal role in human cancer. Consistently, the expressions of TTI1 and Ki67 had a positive relationship in NSCLC cells and tissues. Notably, patients with overexpression of TTI1 or Ki67 had a shorter overall survival rate and a higher disease-free survival rate compared to patients with low expression of TTI1 or Ki67, and the combination of TTI1 and Ki67 was an independent parameter predicting the prognosis and recurrence of NSCLC patients. We conclude that TTI1 promotes NSCLC cell proliferation, metastasis, and invasion by regulating mTOR activity, and the combination of TTI1 and Ki67 is a valuable molecular biomarker for the survival and recurrence of NSCLC patients.

A virus-induced circular RNA maintains latent infection of Kaposi's sarcoma herpesvirus

Non-coding RNAs (ncRNAs) play important roles in host-pathogen interactions; oncogenic viruses like Kaposi's sarcoma herpesvirus (KSHV) employ ncRNAs to establish a latent reservoir and persist for the life of the host. We previously reported that KSHV infection alters a novel class of RNA, circular RNAs (circRNAs). CircRNAs are alternative splicing isoforms and regulate gene expression, but their importance in infection is largely unknown. Here, we showed that a human circRNA, hsa_circ_0001400, is induced by various pathogenic viruses, namely KSHV, Epstein-Barr virus, and human cytomegalovirus. The induction of circRNAs including circ_0001400 by KSHV is co-transcriptionally regulated, likely at splicing. Consistently, screening for circ_0001400-interacting proteins identified a splicing factor, PNISR. Functional studies using infected primary endothelial cells revealed that circ_0001400 inhibits KSHV lytic transcription and virus production. Simultaneously, the circRNA promoted cell cycle, inhibited apoptosis, and induced immune genes. RNA-pull down assays identified transcripts interacting with circ_0001400, including TTI1, which is a component of the pro-growth mTOR complexes. We thus identified a circRNA that is pro-growth and anti-lytic replication. These results support a model in which KSHV induces circ_0001400 expression to maintain latency. Since circ_0001400 is induced by multiple viruses, this novel viral strategy may be widely employed by other viruses.

The Importance of mTORC1-Autophagy Axis for Skeletal Muscle Diseases

The mechanistic target of rapamycin (mTOR) complex 1, mTORC1, integrates nutrient and growth factor signals with cellular responses and plays critical roles in regulating cell growth, proliferation, and lifespan. mTORC1 signaling has been reported as a central regulator of autophagy by modulating almost all aspects of the autophagic process, including initiation, expansion, and termination. An increasing number of studies suggest that mTORC1 and autophagy are critical for the physiological function of skeletal muscle and are involved in diverse muscle diseases. Here, we review recent insights into the essential roles of mTORC1 and autophagy in skeletal muscles and their implications in human muscle diseases. Multiple inhibitors targeting mTORC1 or autophagy have already been clinically approved, while others are under development. These chemical modulators that target the mTORC1/autophagy pathways represent promising potentials to cure muscle diseases.

Translational Aspects of the Mammalian Target of Rapamycin Complexes in Diabetic Nephropathy

Significance: Despite the many efforts put into understanding diabetic nephropathy (DN), direct treatments for DN have yet to be discovered. Understanding the mechanisms behind DN is an essential step in the development of novel therapeutic regimens. The mammalian target of rapamycin (mTOR) pathway has emerged as an important candidate in the quest for drug discovery because of its role in regulating growth, proliferation, as well as protein and lipid metabolism. Recent Advances: Kidney cells have been found to rely on basal autophagy for survival and for conserving kidney integrity. Recent studies have shown that diabetes induces renal autophagy deregulation, leading to kidney injury. Hyper-activation of the mTOR pathway and oxidative stress have been suggested to play a role in diabetes-induced autophagy imbalance. Critical Issues: A detailed understanding of the role of mTOR signaling in diabetes-associated complications is of major importance in the search for a cure. In this review, we provide evidence that mTOR is heavily implicated in diabetes-induced kidney injury. We suggest possible mechanisms through which mTOR exerts its negative effects by increasing insulin resistance, upregulating oxidative stress, and inhibiting autophagy. Future Directions: Both increased oxidative stress and autophagy deregulation are deeply embedded in DN. However, the mechanisms controlling oxidative stress and autophagy are not well understood. Although Akt/mTOR signaling seems to play an important role in oxidative stress and autophagy, further investigation is required to uncover the details of this signaling pathway. Antioxid. Redox Signal. 37, 802-819.

Transposon-activated POU5F1B promotes colorectal cancer growth and metastasis

The treatment of colorectal cancer (CRC) is an unmet medical need in absence of early diagnosis. Here, upon characterizing cancer-specific transposable element-driven transpochimeric gene transcripts (TcGTs) produced by this tumor in the SYSCOL cohort, we find that expression of the hominid-restricted retrogene POU5F1B through aberrant activation of a primate-specific endogenous retroviral promoter is a strong negative prognostic biomarker. Correlating this observation, we demonstrate that POU5F1B fosters the proliferation and metastatic potential of CRC cells. We further determine that POU5F1B, in spite of its phylogenetic relationship with the POU5F1/OCT4 transcription factor, is a membrane-enriched protein that associates with protein kinases and known targets or interactors as well as with cytoskeleton-related molecules, and induces intracellular signaling events and the release of trans-acting factors involved in cell growth and cell adhesion. As POU5F1B is an apparently non-essential gene only lowly expressed in normal tissues, and as POU5F1B-containing TcGTs are detected in other tumors besides CRC, our data provide interesting leads for the development of cancer therapies.

Prospects of targeting PI3K/AKT/mTOR pathway in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) has one of the worst prognoses among all malignancies. PI3K/AKT/mTOR signaling pathway, a main downstream effector of KRAS is involved in the regulation of key hallmarks of cancer. We here report that whole-genome analyses demonstrate the frequent involvement of aberrant activations of PI3K/AKT/mTOR pathway components in PDAC patients and critically evaluate preclinical and clinical evidence on the application of PI3K/AKT/mTOR pathway targeting agents. Combinations of these agents with chemotherapeutics or other targeted therapies, including the modulators of cyclin-dependent kinases, receptor tyrosine kinases and RAF/MEK/ERK pathway are also examined. Although human genetic studies and preclinical pharmacological investigations have provided strong evidence on the role of PI3K/AKT/mTOR pathway in PDAC, clinical studies in general have not been as promising. Patient stratification seems to be the key missing point and with the advent of biomarker-guided clinical trials, targeting PI3K/AKT/mTOR pathway could provide valuable assets for treatment of pancreatic cancer patients.

The Role of Hsp90-R2TP in Macromolecular Complex Assembly and Stabilization

Hsp90 is a ubiquitous molecular chaperone involved in many cell signaling pathways, and its interactions with specific chaperones and cochaperones determines which client proteins to fold. Hsp90 has been shown to be involved in the promotion and maintenance of proper protein complex assembly either alone or in association with other chaperones such as the R2TP chaperone complex. Hsp90-R2TP acts through several mechanisms, such as by controlling the transcription of protein complex subunits, stabilizing protein subcomplexes before their incorporation into the entire complex, and by recruiting adaptors that facilitate complex assembly. Despite its many roles in protein complex assembly, detailed mechanisms of how Hsp90-R2TP assembles protein complexes have yet to be determined, with most findings restricted to proteomic analyses and in vitro interactions. This review will discuss our current understanding of the function of Hsp90-R2TP in the assembly, stabilization, and activity of the following seven classes of protein complexes: L7Ae snoRNPs, spliceosome snRNPs, RNA polymerases, PIKKs, MRN, TSC, and axonemal dynein arms.

The central role of mTORC1 in amino acid sensing

The mechanistic target of rapamycin (mTOR) is a master regulator of cell growth that controls cell homeostasis in response to nutrients, growth factors, and other environmental cues. Recent studies have emphasized the importance of lysosomes as a hub for nutrient sensing, especially amino acid sensing by mTORC1. This review highlights recent advances in understanding the amino acid-mTORC1 signaling axis and the role of mTORC1 in cancer.

Mechanistic Target of Rapamycin Complex 1: From a Nutrient Sensor to a Key Regulator of Metabolism and Health

Mechanistic target of rapamycin complex 1 (mTORC1) is a multi-protein complex widely found in eukaryotes. It serves as a central signaling node to coordinate cell growth and metabolism by sensing diverse extracellular and intracellular inputs, including amino acid-, growth factor-, glucose-, and nucleotide-related signals. It is well documented that mTORC1 is recruited to the lysosomal surface, where it is activated and, accordingly, modulates downstream effectors involved in regulating protein, lipid, and glucose metabolism. mTORC1 is thus the central node for coordinating the storage and mobilization of nutrients and energy across various tissues. However, emerging evidence indicated that the overactivation of mTORC1 induced by nutritional disorders leads to the occurrence of a variety of metabolic diseases, including obesity and type 2 diabetes, as well as cancer, neurodegenerative disorders, and aging. That the mTORC1 pathway plays a crucial role in regulating the occurrence of metabolic diseases renders it a prime target for the development of effective therapeutic strategies. Here, we focus on recent advances in our understanding of the regulatory mechanisms underlying how mTORC1 integrates metabolic inputs as well as the role of mTORC1 in the regulation of nutritional and metabolic diseases.

Systems genetics in the rat HXB/BXH family identifies Tti2 as a pleiotropic quantitative trait gene for adult hippocampal neurogenesis and serum glucose

Neurogenesis in the adult hippocampus contributes to learning and memory in the healthy brain but is dysregulated in metabolic and neurodegenerative diseases. The molecular relationships between neural stem cell activity, adult neurogenesis, and global metabolism are largely unknown. Here we applied unbiased systems genetics methods to quantify genetic covariation among adult neurogenesis and metabolic phenotypes in peripheral tissues of a genetically diverse family of rat strains, derived from a cross between the spontaneously hypertensive (SHR/OlaIpcv) strain and Brown Norway (BN-Lx/Cub). The HXB/BXH family is a very well established model to dissect genetic variants that modulate metabolic and cardiovascular diseases and we have accumulated deep phenome and transcriptome data in a FAIR-compliant resource for systematic and integrative analyses. Here we measured rates of precursor cell proliferation, survival of new neurons, and gene expression in the hippocampus of the entire HXB/BXH family, including both parents. These data were combined with published metabolic phenotypes to detect a neurometabolic quantitative trait locus (QTL) for serum glucose and neuronal survival on Chromosome 16: 62.1-66.3 Mb. We subsequently fine-mapped the key phenotype to a locus that includes the Telo2-interacting protein 2 gene (Tti2)-a chaperone that modulates the activity and stability of PIKK kinases. To verify the hypothesis that differences in neurogenesis and glucose levels are caused by a polymorphism in Tti2, we generated a targeted frameshift mutation on the SHR/OlaIpcv background. Heterozygous SHR-Tti2+/- mutants had lower rates of hippocampal neurogenesis and hallmarks of dysglycemia compared to wild-type littermates. Our findings highlight Tti2 as a causal genetic link between glucose metabolism and structural brain plasticity. In humans, more than 800 genomic variants are linked to TTI2 expression, seven of which have associations to protein and blood stem cell factor concentrations, blood pressure and frontotemporal dementia.

The central moTOR of metabolism

The protein kinase mechanistic target of rapamycin (mTOR) functions as a central regulator of metabolism, integrating diverse nutritional and hormonal cues to control anabolic processes, organismal physiology, and even aging. This review discusses the current state of knowledge regarding the regulation of mTOR signaling and the metabolic regulation of the four macromolecular building blocks of the cell: carbohydrate, nucleic acid, lipid, and protein by mTOR. We review the role of mTOR in the control of organismal physiology and aging through its action in key tissues and discuss the potential for clinical translation of mTOR inhibition for the treatment and prevention of diseases of aging.

The TRRAP transcription cofactor represses interferon-stimulated genes in colorectal cancer cells

Transcription is essential for cells to respond to signaling cues and involves factors with multiple distinct activities. One such factor, TRRAP, functions as part of two large complexes, SAGA and TIP60, which have crucial roles during transcription activation. Structurally, TRRAP belongs to the phosphoinositide 3 kinase-related kinases (PIKK) family but is the only member classified as a pseudokinase. Recent studies established that a dedicated HSP90 co-chaperone, the triple T (TTT) complex, is essential for PIKK stabilization and activity. Here, using endogenous auxin-inducible degron alleles, we show that the TTT subunit TELO2 promotes TRRAP assembly into SAGA and TIP60 in human colorectal cancer cells (CRCs). Transcriptomic analysis revealed that TELO2 contributes to TRRAP regulatory roles in CRC cells, most notably of MYC target genes. Surprisingly, TELO2 and TRRAP depletion also induced the expression of type I interferon genes. Using a combination of nascent RNA, antibody-targeted chromatin profiling (CUT&RUN), ChIP, and kinetic analyses, we propose a model by which TRRAP directly represses the transcription of IRF9, which encodes a master regulator of interferon-stimulated genes. We have therefore uncovered an unexpected transcriptional repressor role for TRRAP, which we propose contributes to its tumorigenic activity.

Ivermectin represses Wnt/β-catenin signaling by binding to TELO2, a regulator of phosphatidylinositol 3-kinase-related kinases

Ivermectin (IVM), an avermectin-derivative anthelmintic, specifically binds to glutamate-gated chloride ion channels (GluCls), causing paralysis in invertebrates. IVM also exhibits other biological activities such as Wnt/β-catenin pathway inhibition in vertebrates that do not possess GluCls. This study showed that affinity purification using immobilized IVM B1a isolated TELO2, a cofactor of phosphatidylinositol 3-kinase-related kinases (PIKKs), as a specific IVM B1a-binding protein. TELO2 knockdown reduced cytoplasmic β-catenin and the transcriptional activation of β-catenin/TCF. IVM B1a bound to TELO2 through the C-terminal α-helix, in which mutations conferred IVM resistance. IVM reduced the TELO2 and PIKK protein levels and the AKT and S6 kinase phosphorylation levels. The inhibition of mTOR kinase reduced the cytoplasmic β-catenin level. Therefore, IVM binds to TELO2, inhibiting PIKKs and reducing the cytoplasmic β-catenin level. In conclusion, our data indicate TELO2 as a druggable target for human diseases involving abnormalities of the Wnt/β-catenin pathway and PIKKs, including mTOR.

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Ivermectin is a chemical suppressor of the eyeless phenotype in zebrafish embryos

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Ivermectin physically interacts with TELO2

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TELO2 mediates Wnt/β-catenin signaling inhibition by ivermectin

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Ivermectin reduces the PIKK protein levels and downstream signaling

Targeting mTOR Signaling in Type 2 Diabetes Mellitus and Diabetes Complications

The mechanistic target of rapamycin (mTOR) is a pivotal regulator of cell metabolism and growth. In the form of two different multi-protein complexes, mTORC1 and mTORC2, mTOR integrates cellular energy, nutrient and hormonal signals to regulate cellular metabolic homeostasis. In type 2 diabetes mellitus (T2DM) aberrant mTOR signaling underlies its pathological conditions and end-organ complications. Substantial evidence suggests that two mTOR-mediated signaling schemes, mTORC1-p70S6 kinase 1 (S6K1) and mTORC2-protein kinase B (AKT), play a critical role in insulin sensitivity and that their dysfunction contributes to development of T2DM. This review summaries our current understanding of the role of mTOR signaling in T2DM and its associated complications, as well as the potential use of mTOR inhibitors in treatment of T2DM.

Autophagy Modulation and Cancer Combination Therapy: A Smart Approach in Cancer Therapy

The autophagy pathway is the process whereby cells keep cellular homeostasis and respond to stress via recycling their damaged cellular proteins, organelles, and other cellular components. In the context of cancer, autophagy is a dual-edge sword pro- and anti-tumorigenic role depending on the oncogenic context and stage of tumorigenesis. Cancer cells have a higher dependency on autophagy compared with normal cells because of cellular damages and high demands for energy. The carbon, nitrogen, and molecular oxygen are building blocks for highly proliferative cancer cells which extremely depend on glutaminolysis and aerobic glycolysis; when a cancer cell is restricted to glucose and glutamine, it initiates to activate a stress response pathway using autophagy. Oncogenic tyrosine kinases (OncTKs) and receptor tyrosine kinases (RTKs) activation result in autophagy modulation through activation of the PI3K/AKT/mTORC1 and RAS/MAPK signaling pathways. Targeted inhibition of tyrosine kinases (TKs) and RTKs have recently been considered as cancer therapy but drug resistance and cancer relapse continue to be a major limitation of tyrosine kinase inhibitors (TKIs). Manipulation of autophagy pathway along with TKIs may be a promising strategy to circumvent unknown existing drug-resistance mechanisms that may emerge in a treated patient. In this way, clinical trials are ongoing to modulate autophagy to treat cancer. This review aims to summarize the combination therapy of autophagy affecting compounds with anticancer drugs which target cell signaling pathways, metabolism mechanisms, and epigenetics modification to improve therapeutic efficacy against cancers.

Effects of heroin self-administration and forced withdrawal on the expression of genes related to the mTOR network in the basolateral complex of the amygdala of male Lewis rats

RATIONALE

The development of substance use disorders involves long-lasting adaptations in specific brain areas that result in an elevated risk of relapse. Some of these adaptations are regulated by the mTOR network, a signalling system that integrates extracellular and intracellular stimuli and modulates several processes related to plasticity. While the role of the mTOR network in cocaine- and alcohol-related disorders is well established, little is known about its participation in opiate use disorders.

OBJECTIVES

To use a heroin self-administration and a withdrawal protocol that induce incubation of heroin-seeking in male rats and study the associated effects on the expression of several genes related to the mTOR system and, in the specific case of Rictor, its respective translated protein and phosphorylation.

RESULTS

We found that heroin self-administration elicited an increase in the expression of the genes Igf1r, Igf2r, Akt2 and Gsk3a in the basolateral complex of the amygdala, which was not as evident at 30 days of withdrawal. We also found an increase in the expression of Rictor (a protein of the mTOR complex 2) after heroin self-administration compared to the saline group, which was occluded at the 30-day withdrawal period. The activation levels of Rictor, measured by the phosphorylation rate, were also reduced after heroin self-administration, an effect that seemed more apparent in the protracted withdrawal group.

CONCLUSIONS

These results suggest that heroin self-administration under extended access conditions modifies the expression profile of activators and components of the mTOR complexes and show a putative irresponsive mTOR complex 2 after withdrawal from heroin use.

Structure of the Human TELO2-TTI1-TTI2 Complex

Phosphatidylinositol 3-kinase-related protein kinases (PIKKs) play critical roles in various metabolic pathways related to cell proliferation and survival. The TELO2-TTI1-TTI2 (TTT) complex has been proposed to recognize newly synthesized PIKKs and to deliver them to the R2TP complex (RUVBL1-RUVBL2-RPAP3-PIH1D1) and the heat shock protein 90 chaperone, thereby supporting their folding and assembly. Here, we determined the cryo-EM structure of the TTT complex at an average resolution of 4.2 Å. We describe the full-length structures of TTI1 and TELO2, and a partial structure of TTI2. All three proteins form elongated helical repeat structures. TTI1 provides a platform on which TELO2 and TTI2 bind to its central region and C-terminal end, respectively. The TELO2 C-terminal domain (CTD) is required for the interaction with TTI1 and recruitment of Ataxia-telangiectasia mutated (ATM). The N- and C-terminal segments of TTI1 recognize the FRAP-ATM-TRRAP (FAT) domain and the N-terminal HEAT repeats of ATM, respectively. The TELO2 CTD and TTI1 N- and C-terminal segments are required for cell survival in response to ionizing radiation.

The genome of New Zealand trevally (Carangidae: Pseudocaranx georgianus) uncovers a XY sex determination locus

BACKGROUND

The genetic control of sex determination in teleost species is poorly understood. This is partly because of the diversity of mechanisms that determine sex in this large group of vertebrates, including constitutive genes linked to sex chromosomes, polygenic constitutive mechanisms, environmental factors, hermaphroditism, and unisexuality. Here we use a de novo genome assembly of New Zealand silver trevally (Pseudocaranx georgianus) together with sex-specific whole genome sequencing data to detect sexually divergent genomic regions, identify candidate genes and develop molecular makers.

RESULTS

The de novo assembly of an unsexed trevally (Trevally_v1) resulted in a final assembly of 579.4 Mb in length, with a N50 of 25.2 Mb. Of the assembled scaffolds, 24 were of chromosome scale, ranging from 11 to 31 Mb in length. A total of 28,416 genes were annotated after 12.8 % of the assembly was masked with repetitive elements. Whole genome re-sequencing of 13 wild sexed trevally (seven males and six females) identified two sexually divergent regions located on two scaffolds, including a 6 kb region at the proximal end of chromosome 21. Blast analyses revealed similarity between one region and the aromatase genes cyp19 (a1a/b) (E-value < 1.00E-25, identity > 78.8 %). Males contained higher numbers of heterozygous variants in both regions, while females showed regions of very low read-depth, indicative of male-specificity of this genomic region. Molecular markers were developed and subsequently tested on 96 histologically-sexed fish (42 males and 54 females). Three markers amplified in absolute correspondence with sex (positive in males, negative in females).

CONCLUSIONS

The higher number of heterozygous variants in males combined with the absence of these regions in females support a XY sex-determination model, indicating that the trevally_v1 genome assembly was developed from a male specimen. This sex system contrasts with the ZW sex-determination model documented in closely related carangid species. Our results indicate a sex-determining function of a cyp19a1a-like gene, suggesting the molecular pathway of sex determination is somewhat conserved in this family. The genomic resources developed here will facilitate future comparative work, and enable improved insights into the varied sex determination pathways in teleosts. The sex marker developed in this study will be a valuable resource for aquaculture selective breeding programmes, and for determining sex ratios in wild populations.

The Hsp90 cochaperone TTT promotes cotranslational maturation of PIKKs prior to complex assembly

Phosphatidylinositol 3-kinase-related kinases (PIKKs) are a family of kinases that control fundamental processes, including cell growth, DNA damage repair, and gene expression. Although their regulation and activities are well characterized, little is known about how PIKKs fold and assemble into active complexes. Previous work has identified a heat shock protein 90 (Hsp90) cochaperone, the TTT complex, that specifically stabilizes PIKKs. Here, we describe a mechanism by which TTT promotes their de novo maturation in fission yeast. We show that TTT recognizes newly synthesized PIKKs during translation. Although PIKKs form multimeric complexes, we find that they do not engage in cotranslational assembly with their partners. Rather, our findings suggest a model by which TTT protects nascent PIKK polypeptides from misfolding and degradation because PIKKs acquire their native state after translation is terminated. Thus, PIKK maturation and assembly are temporally segregated, suggesting that the biogenesis of large complexes requires both dedicated chaperones and cotranslational interactions between subunits.

Proximity-Dependent Biotinylation to Elucidate the Interactome of TNK2 Nonreceptor Tyrosine Kinase

Nonreceptor tyrosine kinases (NRTKs) represent an important class of signaling molecules driving diverse cellular pathways. Aberrant expression and hyperphosphorylation of TNK2, an NRTK, have been implicated in multiple cancers. However, the exact proteins and cellular events that mediate phenotypic changes downstream of TNK2 are unclear. Biological systems that employ proximity-dependent biotinylation methods, such as BioID, are being increasingly used to map protein-protein interactions, as they provide increased sensitivity in discovering interaction partners. In this study, we employed stable isotope labeling with amino acids in cell culture and BioID coupled to the biotinylation site identification technology (BioSITe) method that we recently developed to quantitatively explore the interactome of TNK2. By performing a controlled comparative analysis between full-length TNK2 and its truncated counterpart, we were able to not only identify site-level biotinylation of previously well-established TNK2 binders and substrates including NCK1, NCK2, CTTN, and STAT3, but also discover several novel TNK2 interacting partners. We also performed co-immunoprecipitation and immunofluorescence analysis to validate the interaction between TNK2 and CLINT1, a novel TNK2 interacting protein. Overall, this work reveals the power of the BioSITe method coupled to BioID and highlights several molecules that warrant further exploration to assess their functional significance in TNK2-mediated signaling.

The HSP90/R2TP assembly chaperone promotes cell proliferation in the intestinal epithelium

The R2TP chaperone cooperates with HSP90 to integrate newly synthesized proteins into multi-subunit complexes, yet its role in tissue homeostasis is unknown. Here, we generated conditional, inducible knock-out mice for Rpap3 to inactivate this core component of R2TP in the intestinal epithelium. In adult mice, Rpap3 invalidation caused destruction of the small intestinal epithelium and death within 10 days. Levels of R2TP substrates decreased, with strong effects on mTOR, ATM and ATR. Proliferative stem cells and progenitors deficient for Rpap3 failed to import RNA polymerase II into the nucleus and they induced p53, cell cycle arrest and apoptosis. Post-mitotic, differentiated cells did not display these alterations, suggesting that R2TP clients are preferentially built in actively proliferating cells. In addition, high RPAP3 levels in colorectal tumors from patients correlate with bad prognosis. Here, we show that, in the intestine, the R2TP chaperone plays essential roles in normal and tumoral proliferation.

The PI3K/AKT/mTOR signaling pathway inhibitors enhance radiosensitivity in cancer cell lines

INTRODUCTION

Radiotherapy is one of the most common types of cancer treatment modalities. Radiation can affect both cancer and normal tissues, which limits the whole delivered dose. It is well documented that radiation activates phosphatidylinositol 3-kinase (PI3K) and AKT signaling pathway; hence, the inhibition of this pathway enhances the radiosensitivity of tumor cells. The mammalian target of rapamycin (mTOR) is a regulator that is involved in autophagy, cell growth, proliferation, and survival.

CONCLUSION

The inhibition of mTOR as a downstream mediator of the PI3K/AKT signaling pathway represents a vital option for more effective cancer treatments. The combination of PI3K/AKT/mTOR inhibitors with radiation can increase the radiosensitivity of malignant cells to radiation by autophagy activation. Therefore, this review aims to discuss the impact of such inhibitors on the cell response to radiation.

The role of mTOR in age-related diseases

The ageing population is becoming a significant socio-economic issue. To address the expanding health gap, it is important to deepen our understanding of the mechanisms underlying ageing in various organisms at the single-cell level. The discovery of the antifungal, immunosuppressive, and anticancer drug rapamycin, which possesses the ability to extend the lifespan of several species, has prompted extensive research in the areas of cell metabolic regulation, development, and senescence. At the centre of this research is the mTOR pathway, with key roles in cell growth, proteosynthesis, ribosomal biogenesis, transcriptional regulation, glucose and lipid metabolism, and autophagy. Recently, it has become obvious that mTOR dysregulation is involved in several age-related diseases, such as cancer, neurodegenerative diseases, and type 2 diabetes mellitus. Additionally, mTOR hyperactivation affects the process of ageing per se. In this review, we provide an overview of recent insights into the mTOR signalling pathway, including its regulation and its influence on various hallmarks of ageing at the cellular level.

Structure of the TELO2-TTI1-TTI2 complex and its function in TOR recruitment to the R2TP chaperone

The R2TP (RUVBL1-RUVBL2-RPAP3-PIH1D1) complex, in collaboration with heat shock protein 90 (HSP90), functions as a chaperone for the assembly and stability of protein complexes, including RNA polymerases, small nuclear ribonucleoprotein particles (snRNPs), and phosphatidylinositol 3-kinase (PI3K)-like kinases (PIKKs) such as TOR and SMG1. PIKK stabilization depends on an additional complex of TELO2, TTI1, and TTI2 (TTT), whose structure and function are poorly understood. The cryoelectron microscopy (cryo-EM) structure of the human R2TP-TTT complex, together with biochemical experiments, reveals the mechanism of TOR recruitment to the R2TP-TTT chaperone. The HEAT-repeat TTT complex binds the kinase domain of TOR, without blocking its activity, and delivers TOR to the R2TP chaperone. In addition, TTT regulates the R2TP chaperone by inhibiting RUVBL1-RUVBL2 ATPase activity and by modulating the conformation and interactions of the PIH1D1 and RPAP3 components of R2TP. Taken together, our results show how TTT couples the recruitment of TOR to R2TP with the regulation of this chaperone system.

Insulin Resistance and Diabetes Mellitus in Alzheimer's Disease

Type 2 diabetes mellitus is a progressive disease that is characterized by the appearance of insulin resistance. The term insulin resistance is very wide and could affect different proteins involved in insulin signaling, as well as other mechanisms. In this review, we have analyzed the main molecular mechanisms that could be involved in the connection between type 2 diabetes and neurodegeneration, in general, and more specifically with the appearance of Alzheimer's disease. We have studied, in more detail, the different processes involved, such as inflammation, endoplasmic reticulum stress, autophagy, and mitochondrial dysfunction.

Current Approaches and Future Directions for the Treatment of mTORopathies

The mechanistic target of rapamycin (mTOR) is a kinase at the center of an evolutionarily conserved signaling pathway that orchestrates cell growth and metabolism. mTOR responds to an array of intra- and extracellular stimuli and in turn controls multiple cellular anabolic and catabolic processes. Aberrant mTOR activity is associated with numerous diseases, with particularly profound impact on the nervous system. mTOR is found in two protein complexes, mTOR complex 1 (mTORC1) and 2 (mTORC2), which are governed by different upstream regulators and have distinct cellular actions. Mutations in genes encoding for mTOR regulators result in a collection of neurodevelopmental disorders known as mTORopathies. While these disorders can affect multiple organs, neuropsychiatric conditions such as epilepsy, intellectual disability, and autism spectrum disorder have a major impact on quality of life. The neuropsychiatric aspects of mTORopathies have been particularly challenging to treat in a clinical setting. Current therapeutic approaches center on rapamycin and its analogs, drugs that are administered systemically to inhibit mTOR activity. While these drugs show some clinical efficacy, adverse side effects, incomplete suppression of mTOR targets, and lack of specificity for mTORC1 or mTORC2 may limit their utility. An increased understanding of the neurobiology of mTOR and the underlying molecular, cellular, and circuit mechanisms of mTOR-related disorders will facilitate the development of improved therapeutics. Animal models of mTORopathies have helped unravel the consequences of mTOR pathway mutations in specific brain cell types and developmental stages, revealing an array of disease-related phenotypes. In this review, we discuss current progress and potential future directions for the therapeutic treatment of mTORopathies with a focus on findings from genetic mouse models.

RNA Sequencing Reveals Distinct Immune Responses in the Chorioamniotic Membranes of Women with Preterm Labor and Microbial or Sterile Intra-amniotic Inflammation

Preterm labor precedes premature birth, the leading cause of neonatal morbidity and mortality worldwide. Preterm labor can occur in the context of either microbe-associated intra-amniotic inflammation (i.e., intra-amniotic infection) or intra-amniotic inflammation in the absence of detectable microorganisms (i.e., sterile intra-amniotic inflammation). Both intra-amniotic infection and sterile intra-amniotic inflammation trigger local immune responses that have deleterious effects on fetal life. Yet, the extent of such immune responses in the fetal tissues surrounding the amniotic cavity (i.e., the chorioamniotic membranes) is poorly understood. By using RNA sequencing (RNA seq) as a discovery approach, we found that there were significant transcriptomic differences involving host response to pathogens in the chorioamniotic membranes of women with intra-amniotic infection compared to those from women without inflammation. In addition, the sterile or microbial nature of intra-amniotic inflammation was associated with distinct transcriptomic profiles in the chorioamniotic membranes. Moreover, the immune response in the chorioamniotic membranes of women with sterile intra-amniotic inflammation was milder in nature than that induced by microbes and involved the upregulation of alarmins and inflammasome-related molecules. Lastly, the presence of maternal and fetal inflammatory responses in the placenta was associated with the upregulation of immune processes in the chorioamniotic membranes. Collectively, these findings provide insight into the immune responses against microbes or alarmins that take place in the fetal tissues surrounding the amniotic cavity, shedding light on the immunobiology of preterm labor and birth.

Finding new edges: systems approaches to MTOR signaling

Cells have evolved highly intertwined kinase networks to finely tune cellular homeostasis to the environment. The network converging on the mechanistic target of rapamycin (MTOR) kinase constitutes a central hub that integrates metabolic signals and adapts cellular metabolism and functions to nutritional changes and stress. Feedforward and feedback loops, crosstalks and a plethora of modulators finely balance MTOR-driven anabolic and catabolic processes. This complexity renders it difficult — if not impossible — to intuitively decipher signaling dynamics and network topology. Over the last two decades, systems approaches have emerged as powerful tools to simulate signaling network dynamics and responses. In this review, we discuss the contribution of systems studies to the discovery of novel edges and modulators in the MTOR network in healthy cells and in disease.

The complex network of mTOR signaling in the heart

The mechanistic target of rapamycin (mTOR) integrates several intracellular and extracellular signals involved in the regulation of anabolic and catabolic processes. mTOR assembles into two macromolecular complexes, named mTORC1 and mTORC2, which have different regulators, substrates and functions. Studies of gain- and loss-of-function animal models of mTOR signaling revealed that mTORC1/2 elicit both adaptive and maladaptive functions in the cardiovascular system. Both mTORC1 and mTORC2 are indispensable for driving cardiac development and cardiac adaption to stress, such as pressure overload. However, persistent and deregulated mTORC1 activation in the heart is detrimental during stress and contributes to the development and progression of cardiac remodeling and genetic and metabolic cardiomyopathies. In this review, we discuss the latest findings regarding the role of mTOR in the cardiovascular system, both under basal conditions and during stress, such as pressure overload, ischemia and metabolic stress. Current data suggest that mTOR modulation may represent a potential therapeutic strategy for the treatment of cardiac diseases.