The mTOR-lysosome axis at the centre of ageing

SMARCA4 (BRG1) activates ABCC3 transcription to promote hepatocellular carcinogenesis

AIMS

Hepatocellular carcinoma (HCC) is a lead cause of cancer-related deaths. In the present study we investigated the role of Brahma-related gene 1 (BRG1), a chromatin remodeling protein, in HCC the pathogenesis focusing on identifying novel transcription targets.

METHODS AND MATERIALS

Hepatocellular carcinogenesis was modeled in mice by diethylnitrosamine (DEN). Cellular transcriptome was evaluated by RNA-seq.

RESULTS

Hepatocellular carcinoma was appreciably retarded in BRG1 knockout mice compared to wild type littermates. Transcriptomic analysis identified ATP Binding Cassette Subfamily C Member 3 (ABCC3) as a novel target of BRG1. BRG1 over-expression in BRG1low HCC cells (HEP1) up-regulated whereas BRG1 depletion in BRG1high HCC cells (SNU387) down-regulated ABCC3 expression. Importantly, BRG1 was detected to directly bind to the ABCC3 promoter to activate ABCC3 transcription. BRG1 over-expression in HEP1 cells promoted proliferation and migration, both of which were abrogated by ABCC3 silencing. On the contrary, BRG1 depletion in SNU387 cells decelerated proliferation and migration, both of which were rescued by ABCC3 over-expression. Importantly, high BRG1/ABCC3 expression predicted poor prognosis in HCC patients. Mechanistically, ABCC3 regulated hepatocellular carcinogenesis possibly by influencing lysosomal homeostasis.

SIGNIFICANCE

In conclusion, our data suggest that targeting BRG1 and its downstream target ABCC3 can be considered as a reasonable approach for the intervention of hepatocellular carcinoma.

Inhibition of Pim kinases triggers a broad antiviral activity by affecting innate immunity and via the PI3K-Akt-mTOR axis the endolysosomal system

Zoonoses such as ZIKV and SARS-CoV-2 pose a severe risk to global health. There is urgent need for broad antiviral strategies based on host-targets filling gaps between pathogen emergence and availability of therapeutic or preventive strategies. Significant reduction of pathogen titers decreases spread of infections and thereby ensures health systems not being overloaded and public life to continue. Based on previously observed interference with FGFR1/2-signaling dependent impact on interferon stimulated gene (ISG)-expression, we identified Pim kinases as promising druggable cellular target. We therefore focused on analyzing the potential of pan-Pim kinase inhibition to trigger a broad antiviral response. The pan-Pim kinase inhibitor AZD1208 exerted an extraordinarily high antiviral effect against various ZIKV isolates, SARS-CoV-2 and HBV. This was reflected by strong reduction in viral RNA, proteins and released infectious particles. Especially in case of SARS-CoV-2, AZD1208 led to a complete removal of viral traces in cells. Kinome-analysis revealed vast changes in kinase landscape upon AZD1208 treatment, especially for inflammation and the PI3K/Akt-pathway. For ZIKV, a clear correlation between antiviral effect and increase in ISG-expression was observed. Based on a cell culture model with impaired ISG-induction, activation of the PI3K-Akt-mTOR axis, leading to major changes in the endolysosomal equilibrium, was identified as second pillar of the antiviral effect triggered by AZD1208-dependent Pim kinase inhibition, also against HBV. We identified Pim-kinases as cellular target for a broad antiviral activity. The antiviral effect exerted by inhibition of Pim kinases is based on at least two pillars: innate immunity and modulation of the endolysosomal system.

The role of the immunosuppressive PD-1/PD-L1 checkpoint pathway in the aging process and age-related diseases

The accumulation of senescent cells within tissues is a hallmark of the aging process. Senescent cells are also commonly present in many age-related diseases and in the cancer microenvironment. The escape of abnormal cells from immune surveillance indicates that there is some defect in the function of cytotoxic immune cells, e.g., CD8+ T cells and natural killer (NK) cells. Recent studies have revealed that the expression of programmed death-ligand 1 (PD-L1) protein is abundantly increased in senescent cells. An increase in the amount of PD-L1 protein protects senescent cells from clearance by the PD-1 checkpoint receptor in cytotoxic immune cells. In fact, the activation of the PD-1 receptor suppresses the cytotoxic properties of CD8+ T and NK cells, promoting a state of immunosenescence. The inhibitory PD-1/PD-L1 checkpoint pathway acts in cooperation with immunosuppressive cells; for example, activation of PD-1 receptor can enhance the differentiation of regulatory T cells (Treg), myeloid-derived suppressor cells (MDSC), and M2 macrophages, whereas the cytokines secreted by immunosuppressive cells stimulate the expression of the immunosuppressive PD-L1 protein. Interestingly, many signaling pathways known to promote cellular senescence and the aging process are crucial stimulators of the expression of PD-L1 protein, e.g., epigenetic regulation, inflammatory mediators, mTOR-related signaling, cGAS-STING pathway, and AhR signaling. It seems that the inhibitory PD-1/PD-L1 immune checkpoint axis has a crucial role in the accumulation of senescent cells and thus it promotes the aging process in tissues. Thus, the blockade of the PD-1/PD-L1 checkpoint signaling might be a potential anti-aging senolytic therapy. KEY MESSAGES: Senescent cells accumulate within tissues during aging and age-related diseases. Senescent cells are able to escape immune surveillance by cytotoxic immune cells. Expression of programmed death-ligand 1 (PD-L1) markedly increases in senescent cells. Age-related signaling stimulates the expression of PD-L1 protein in senescent cells. Inhibitory PD-1/PD-L1 checkpoint pathway suppresses clearance of senescent cells.

ROS-mediated lysosomal membrane permeabilization and autophagy inhibition regulate bleomycin-induced cellular senescence

Bleomycin exhibits effective chemotherapeutic activity against multiple types of tumors, and also induces various side effects, such as pulmonary fibrosis and neuronal defects, which limit the clinical application of this drug. Macroautophagy/autophagy has been recently reported to be involved in the functions of bleomycin, and yet the mechanisms of their crosstalk remain insufficiently understood. Here, we demonstrated that reactive oxygen species (ROS) produced during bleomycin activation hampered autophagy flux by inducing lysosomal membrane permeabilization (LMP) and obstructing lysosomal degradation. Exhaustion of ROS with N-acetylcysteine relieved LMP and autophagy defects. Notably, we observed that LMP and autophagy blockage preceded the emergence of cellular senescence during bleomycin treatment. In addition, promoting or inhibiting autophagy-lysosome degradation alleviated or exacerbated the phenotypes of senescence, respectively. This suggests the alternation of autophagy activity is more a regulatory mechanism than a consequence of bleomycin-induced cellular senescence. Taken together, we reveal a specific role of bleomycin-induced ROS in mediating defects of autophagic degradation and further regulating cellular senescence in vitro and in vivo. Our findings, conversely, indicate the autophagy-lysosome degradation pathway as a target for modulating the functions of bleomycin. These provide a new perspective for optimizing bleomycin as a clinically applicable chemotherapeutics devoid of severe side-effects.Abbreviations: AT2 cells: type II alveolar epithelial cells; ATG7: autophagy related 7; bEnd.3: mouse brain microvascular endothelial cells; BNIP3L: BCL2/adenovirus E1B interacting protein 3-like; CCL2: C-C motif chemokine ligand 2; CDKN1A: cyclin dependent kinase inhibitor 1A; CDKN2A: cyclin dependent kinase inhibitor 2A; FTH1: ferritin heavy polypeptide 1; γ-H2AX: phosphorylated H2A.X variant histone; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HUVEC: human umbilical vein endothelial cells; HT22: hippocampal neuronal cell lines; Il: interleukin; LAMP: lysosomal-associated membrane protein; LMP: lysosome membrane permeabilization; MTORC1: mechanistic target of rapamycin kinase complex 1; NAC: N-acetylcysteine; NCOA4: nuclear receptor coactivator 4; PI3K: phosphoinositide 3-kinase; ROS: reactive oxygen species; RPS6KB/S6K: ribosomal protein S6 kinase; SA-GLB1/β-gal: senescence-associated galactosidase, beta 1; SAHF: senescence-associated heterochromatic foci; SASP: senescence-associated secretory phenotype; SEC62: SEC62 homolog, preprotein translocation; SEP: superecliptic pHluorin; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB.

Autophagy captures the retromer-TBC1D5 complex to inhibit receptor recycling

Retromer prevents the destruction of numerous receptors by recycling them from endosomes to the trans-Golgi network or plasma membrane. This enables retromer to fine-tune the activity of many signaling pathways in parallel. However, the mechanism(s) by which retromer function adapts to environmental fluctuations such as nutrient withdrawal and how this affects the fate of its cargoes remains incompletely understood. Here, we reveal that macroautophagy/autophagy inhibition by MTORC1 controls the abundance of retromer+ endosomes under nutrient-replete conditions. Autophagy activation by chemical inhibition of MTOR or nutrient withdrawal does not affect retromer assembly or its interaction with the RAB7 GAP protein TBC1D5, but rather targets these endosomes for bulk destruction following their capture by phagophores. This process appears to be distinct from amphisome formation. TBC1D5 and its ability to bind to retromer, but not its C-terminal LC3-interacting region (LIR) or nutrient-regulated dephosphorylation, is critical for retromer to be captured by autophagosomes following MTOR inhibition. Consequently, endosomal recycling of its cargoes to the plasma membrane and trans-Golgi network is impaired, leading to their lysosomal turnover. These findings demonstrate a mechanistic link connecting nutrient abundance to receptor homeostasis.Abbreviations: AMPK, 5'-AMP-activated protein kinase; APP, amyloid beta precursor protein; ATG, autophagy related; BafA, bafilomycin A1; CQ, chloroquine; DMEM, Dulbecco's minimum essential medium; DPBS, Dulbecco's phosphate-buffered saline; EBSS, Earle's balanced salt solution; FBS, fetal bovine serum; GAP, GTPase-activating protein; MAP1LC3/LC3, microtubule associated protein 1 light chain 3; LIR, LC3-interacting region; LANDO, LC3-associated endocytosis; LP, leupeptin and pepstatin; MTOR, mechanistic target of rapamycin kinase; MTORC1, MTOR complex 1; nutrient stress, withdrawal of amino acids and serum; PDZ, DLG4/PSD95, DLG1, and TJP1/zo-1; RPS6, ribosomal protein S6; RPS6KB1/S6K1, ribosomal protein S6 kinase B1; SLC2A1/GLUT1, solute carrier family 2 member 1; SORL1, sortillin related receptor 1; SORT1, sortillin 1; SNX, sorting nexin; TBC1D5, TBC1 domain family member 5; ULK1, unc-51 like autophagy activating kinase 1; WASH, WASH complex subunit.

Defects of mitochondria-lysosomes communication induce secretion of mitochondria-derived vesicles and drive chemoresistance in ovarian cancer cells

BACKGROUND

Among the mechanisms of mitochondrial quality control (MQC), generation of mitochondria-derived vesicles (MDVs) is a process to avoid complete failure of mitochondria determining lysosomal degradation of mitochondrial damaged proteins. In this context, RAB7, a late endocytic small GTPase, controls delivery of MDVs to late endosomes for subsequent lysosomal degradation. We previously demonstrated that RAB7 has a pivotal role in response to cisplatin (CDDP) regulating resistance to the drug by extracellular vesicle (EVs) secretion.

METHODS

Western blot and immunofluorescence analysis were used to analyze structure and function of endosomes and lysosomes in CDDP chemosensitive and chemoresistant ovarian cancer cell lines. EVs were purified from chemosensitive and chemoresistant cells by ultracentrifugation or immunoisolation to analyze their mitochondrial DNA and protein content. Treatment with cyanide m-chlorophenylhydrazone (CCCP) and RAB7 modulation were used, respectively, to understand the role of mitochondrial and late endosomal/lysosomal alterations on MDV secretion. Using conditioned media from chemoresistant cells the effect of MDVs on the viability after CDDP treatment was determined. Seahorse assays and immunofluorescence analysis were used to study the biochemical role of MDVs and the uptake and intracellular localization of MDVs, respectively.

RESULTS

We observed that CDDP-chemoresistant cells are characterized by increased MDV secretion, impairment of late endocytic traffic, RAB7 downregulation, an increase of RAB7 in EVs, compared to chemosensitive cells, and downregulation of the TFEB-mTOR pathway overseeing lysosomal and mitochondrial biogenesis and turnover. We established that MDVs can be secreted rather than delivered to lysosomes and are able to deliver CDDP outside the cells. We showed increased secretion of MDVs by chemoresistant cells ultimately caused by the extrusion of RAB7 in EVs, resulting in a dramatic drop in its intracellular content, as a novel mechanism to regulate RAB7 levels. We demonstrated that MDVs purified from chemoresistant cells induce chemoresistance in RAB7-modulated process, and, after uptake from recipient cells, MDVs localize to mitochondria and slow down mitochondrial activity.

CONCLUSIONS

Dysfunctional MQC in chemoresistant cells determines a block in lysosomal degradation of MDVs and their consequent secretion, suggesting that MQC is not able to eliminate damaged mitochondria whose components are secreted becoming effectors and potential markers of chemoresistance.

PRKAA2, MTOR, and TFEB in the regulation of lysosomal damage response and autophagy

Lysosomes function as critical signaling hubs that govern essential enzyme complexes. LGALS proteins (LGALS3, LGALS8, and LGALS9) are integral to the endomembrane damage response. If ESCRT fails to rectify damage, LGALS-mediated ubiquitination occurs, recruiting autophagy receptors (CALCOCO2, TRIM16, and SQSTM1) and VCP/p97 complex containing UBXN6, PLAA, and YOD1, initiating selective autophagy. Lysosome replenishment through biogenesis is regulated by TFEB. LGALS3 interacts with TFRC and TRIM16, aiding ESCRT-mediated repair and autophagy-mediated removal of damaged lysosomes. LGALS8 inhibits MTOR and activates TFEB for ATG and lysosomal gene transcription. LGALS9 inhibits USP9X, activates PRKAA2, MAP3K7, ubiquitination, and autophagy. Conjugation of ATG8 to single membranes (CASM) initiates damage repair mediated by ATP6V1A, ATG16L1, ATG12, ATG5, ATG3, and TECPR1. ATG8ylation or CASM activates the MERIT system (ESCRT-mediated repair, autophagy-mediated clearance, MCOLN1 activation, Ca2+ release, RRAG-GTPase regulation, MTOR modulation, TFEB activation, and activation of GTPase IRGM). Annexins ANAX1 and ANAX2 aid damage repair. Stress granules stabilize damaged membranes, recruiting FLCN-FNIP1/2, G3BP1, and NUFIP1 to inhibit MTOR and activate TFEB. Lysosomes coordinate the synergistic response to endomembrane damage and are vital for innate and adaptive immunity. Future research should unveil the collaborative actions of ATG proteins, LGALSs, TRIMs, autophagy receptors, and lysosomal proteins in lysosomal damage response.

TorS - Reframing a rational for type 2 diabetes treatment

The mammalian target of rapamycin complex 1 syndrome (Tors), paradigm implies an exhaustive cohesive disease entity driven by a hyperactive mTORC1, and which includes obesity, type 2 diabetic hyperglycemia, diabetic dyslipidemia, diabetic cardiomyopathy, diabetic nephropathy, diabetic peripheral neuropathy, hypertension, atherosclerotic cardiovascular disease, non-alcoholic fatty liver disease, some cancers, neurodegeneration, polycystic ovary syndrome, psoriasis and other. The TorS paradigm may account for the efficacy of standard-of-care treatments of type 2 diabetes (T2D) in alleviating the glycaemic and non-glycaemic diseases of TorS in T2D and non-T2D patients. The TorS paradigm may generate novel treatments for TorS diseases.

Basal autophagic flux measured in blood correlates positively with age in adults at increased risk of type 2 diabetes

Preclinical data show that autophagy delays age-related disease. It has been postulated that age-related disease is-at least in part-caused by an age-related decline in autophagy. However, autophagic flux has never been measured in humans across a spectrum of aging in a physiologically relevant context. To address this critical gap in knowledge, the objective of this cross-sectional observational study was to measure basal autophagic flux in whole blood taken from people at elevated risk of developing type 2 diabetes and correlate it with chronological age. During this study, 119 people were recruited and five people were excluded during sample analysis such that 114 people were included in the final analysis. Basal autophagic flux measured in blood and correlations with parameters such as age, body weight, fat mass, AUSDRISK score, blood pressure, glycated hemoglobin HbA1c, blood glucose and insulin, blood lipids, high-sensitivity C-reactive protein, plasma protein carbonylation, and plasma β-hexosaminidase activity were analysed. Despite general consensus in the literature that autophagy decreases with age, we found that basal autophagic flux increased with age in this human cohort. This is the first study to report measurement of basal autophagic flux in a human cohort and its correlation with age. This increase in basal autophagy could represent a stress response to age-related damage. These data are significant not only for their novelty but also because they will inform future clinical studies and show that measurement of basal autophagic flux in a human cohort is feasible.

A physicochemical perspective on cellular ageing

Cellular ageing described at the molecular level is a multifactorial process that leads to a spectrum of ageing trajectories. There has been recent discussion about whether a decline in physicochemical homeostasis causes aberrant phase transitions, which are a driver of ageing. Indeed, the function of all biological macromolecules, regardless of their participation in biomolecular condensates, depends on parameters such as pH, crowding, and redox state. We expand on the physicochemical homeostasis hypothesis and summarise recent evidence that the intracellular milieu influences molecular processes involved in ageing.

Proteostasis in T cell aging

Aging leads to a decline in immune cell function, which leaves the organism vulnerable to infections and age-related multimorbidities. One major player of the adaptive immune response are T cells, and recent studies argue for a major role of disturbed proteostasis contributing to reduced function of these cells upon aging. Proteostasis refers to the state of a healthy, balanced proteome in the cell and is influenced by synthesis (translation), maintenance and quality control of proteins, as well as degradation of damaged or unwanted proteins by the proteasome, autophagy, lysosome and cytoplasmic enzymes. This review focuses on molecular processes impacting on proteostasis in T cells, and specifically functional or quantitative changes of each of these upon aging. Importantly, we describe the biological consequences of compromised proteostasis in T cells, which range from impaired T cell activation and function to enhancement of inflamm-aging by aged T cells. Finally, approaches to improve proteostasis and thus rejuvenate aged T cells through pharmacological or physical interventions are discussed.

Chronic inflammation and the hallmarks of aging

BACKGROUND

Recently, the hallmarks of aging were updated to include dysbiosis, disabled macroautophagy, and chronic inflammation. In particular, the low-grade chronic inflammation during aging, without overt infection, is defined as "inflammaging," which is associated with increased morbidity and mortality in the aging population. Emerging evidence suggests a bidirectional and cyclical relationship between chronic inflammation and the development of age-related conditions, such as cardiovascular diseases, neurodegeneration, cancer, and frailty. How the crosstalk between chronic inflammation and other hallmarks of aging underlies biological mechanisms of aging and age-related disease is thus of particular interest to the current geroscience research.

SCOPE OF REVIEW

This review integrates the cellular and molecular mechanisms of age-associated chronic inflammation with the other eleven hallmarks of aging. Extra discussion is dedicated to the hallmark of "altered nutrient sensing," given the scope of Molecular Metabolism. The deregulation of hallmark processes during aging disrupts the delicate balance between pro-inflammatory and anti-inflammatory signaling, leading to a persistent inflammatory state. The resultant chronic inflammation, in turn, further aggravates the dysfunction of each hallmark, thereby driving the progression of aging and age-related diseases.

MAIN CONCLUSIONS

The crosstalk between chronic inflammation and other hallmarks of aging results in a vicious cycle that exacerbates the decline in cellular functions and promotes aging. Understanding this complex interplay will provide new insights into the mechanisms of aging and the development of potential anti-aging interventions. Given their interconnectedness and ability to accentuate the primary elements of aging, drivers of chronic inflammation may be an ideal target with high translational potential to address the pathological conditions associated with aging.

Counteracting Immunosenescence-Which Therapeutic Strategies Are Promising?

Aging attenuates the overall responsiveness of the immune system to eradicate pathogens. The increased production of pro-inflammatory cytokines by innate immune cells under basal conditions, termed inflammaging, contributes to impaired innate immune responsiveness towards pathogen-mediated stimulation and limits antigen-presenting activity. Adaptive immune responses are attenuated as well due to lowered numbers of naïve lymphocytes and their impaired responsiveness towards antigen-specific stimulation. Additionally, the numbers of immunoregulatory cell types, comprising regulatory T cells and myeloid-derived suppressor cells, that inhibit the activity of innate and adaptive immune cells are elevated. This review aims to summarize our knowledge on the cellular and molecular causes of immunosenescence while also taking into account senescence effects that constitute immune evasion mechanisms in the case of chronic viral infections and cancer. For tumor therapy numerous nanoformulated drugs have been developed to overcome poor solubility of compounds and to enable cell-directed delivery in order to restore immune functions, e.g., by addressing dysregulated signaling pathways. Further, nanovaccines which efficiently address antigen-presenting cells to mount sustained anti-tumor immune responses have been clinically evaluated. Further, senolytics that selectively deplete senescent cells are being tested in a number of clinical trials. Here we discuss the potential use of such drugs to improve anti-aging therapy.

GPR19 Coordinates Multiple Molecular Aspects of Stress Responses Associated with the Aging Process

G protein-coupled receptors (GPCRs) play a significant role in controlling biological paradigms such as aging and aging-related disease. We have previously identified receptor signaling systems that are specifically associated with controlling molecular pathologies associated with the aging process. Here, we have identified a pseudo-orphan GPCR, G protein-coupled receptor 19 (GPR19), that is sensitive to many molecular aspects of the aging process. Through an in-depth molecular investigation process that involved proteomic, molecular biological, and advanced informatic experimentation, this study found that the functionality of GPR19 is specifically linked to sensory, protective, and remedial signaling systems associated with aging-related pathology. This study suggests that the activity of this receptor may play a role in mitigating the effects of aging-related pathology by promoting protective and remedial signaling systems. GPR19 expression variation demonstrates variability in the molecular activity in this larger process. At low expression levels in HEK293 cells, GPR19 expression regulates signaling paradigms linked with stress responses and metabolic responses to these. At higher expression levels, GPR19 expression co-regulates systems involved in sensing and repairing DNA damage, while at the highest levels of GPR19 expression, a functional link to processes of cellular senescence is seen. In this manner, GPR19 may function as a coordinator of aging-associated metabolic dysfunction, stress response, DNA integrity management, and eventual senescence.

Organelle Communication: Joined in Sickness and in Health

Organelles are membrane-lined structures that compartmentalize subcellular biochemical functions. Therefore, interorganelle communication is crucial for cellular responses that require the coordination of such functions. Multiple principles govern interorganelle interactions, which arise from the complex nature of organelles: position, multilingualism, continuity, heterogeneity, proximity, and bidirectionality, among others. Given their importance, alterations in organelle communication have been linked to many diseases. Among the different types of contacts, endoplasmic reticulum mitochondria interactions are the best known; however, mounting evidence indicates that other organelles also have something to say in the pathophysiological conversation.

Stonin 2 activates lysosomal-mTOR axis for cell survival in oral cancer

Aberrant expression of various genes is associated with the progression of oral squamous cell carcinoma. Stonin 2, an endocytic protein, has a prominent role in clathrin-associated endocytosis. Its position in oral cancer is still unknown. Here, we report that STON2 expression increases with an increase in the grade of the oral cancer tissue. Further, STON2 overexpressed cells possess a higher rate of proliferation and migraton in oral cancer cells. STON2 helps maintain lysosomal functions by preserving the lysosomal membrane integrity. It activates the Akt-mTOR axis and retains the mTOR on the membrane of the lysosomes. Further, we have identified an inhibitor of STON2, i.e., Trifluoperazine dihydrochloride (TFP), which targets the lysosomal axis by disrupting the Akt-mTOR pathway and causes lysosomal membrane permeabilization. Intererstingly, TFP shows a decrease in cell vaibility on the oral cancer cells and it was observed that cell viability is restored in TFP-treated STON2 overexpressed cells. Moreover, the lysosomal activity and the Akt-mTOR expression are restored in STON2 overexpressed cells co-treated with TFP, establishing TFP targets STON2 to showcase its anti-cancer effects in oral cancer. In conclusion, STON2 might serve as a potential biomarker in oral cancer, and its inhibition could functions as a novel anti-cancer mechanims against oral cancer.

Cysteinyl leukotriene receptor 1 is a potent regulator of the endosomal-lysosomal system in the ARPE-19 retinal pigment epithelial cell line

The endosomal-lysosomal system is central for cell homeostasis and comprises the functions and dynamics of particular organelles including endosomes, lysosomes and autophagosomes. In previous studies, we found that the cysteinyl leukotriene receptor 1 (CysLTR1) regulates autophagy in the retinal pigment epithelial cell line ARPE-19 under basal cellular conditions. However, the underlying mechanism by which CysLTR1 regulates autophagy is unknown. Thus, in the present study, the effects of CysLTR1 inhibition on the endosomal-lysosomal system are analyzed in detail to identify the role of CysLTR1 in cell homeostasis and autophagy regulation. CysLTR1 inhibition in ARPE-19 cells by Zafirlukast, a CysLTR1 antagonist, depleted the lysosomal pool. Furthermore, CysLTR1 antagonization reduced endocytic capacity and internalization of epidermal growth factor and decreased levels of the transferrin receptor, CD71. Serum starvation abolished the effect of Zafirlukast on the autophagic flux, which identifies the endocytic regulation of serum components by CysLTR1 as an important autophagy-modulating mechanism. The role of CysLTR1 in inflammation and cell stress has been exceedingly studied, but its involvement in the endosomal-lysosomal pathway is largely unknown. This current study provides new insights into basal activity of CysLTR1 on cellular endocytosis and the subsequent impact on downstream processes like autophagy.

Iron Limitation Restores Autophagy and Increases Lifespan in the Yeast Model of Niemann–Pick Type C1

Niemann–Pick type C1 (NPC1) is an endolysosomal transmembrane protein involved in the export of cholesterol and sphingolipids to other cellular compartments such as the endoplasmic reticulum and plasma membrane. NPC1 loss of function is the major cause of NPC disease, a rare lysosomal storage disorder characterized by an abnormal accumulation of lipids in the late endosomal/lysosomal network, mitochondrial dysfunction, and impaired autophagy. NPC phenotypes are conserved in yeast lacking Ncr1, an orthologue of human NPC1, leading to premature aging. Herein, we performed a phosphoproteomic analysis to investigate the effect of Ncr1 loss on cellular functions mediated by the yeast lysosome-like vacuoles. Our results revealed changes in vacuolar membrane proteins that are associated mostly with vesicle biology (fusion, transport, organization), autophagy, and ion homeostasis, including iron, manganese, and calcium. Consistently, the cytoplasm to vacuole targeting (Cvt) pathway was increased in ncr1∆ cells and autophagy was compromised despite TORC1 inhibition. Moreover, ncr1∆ cells exhibited iron overload mediated by the low-iron sensing transcription factor Aft1. Iron deprivation restored the autophagic flux of ncr1∆ cells and increased its chronological lifespan and oxidative stress resistance. These results implicate iron overload on autophagy impairment, oxidative stress sensitivity, and cell death in the yeast model of NPC1.

Acupuncture inhibits autophagy and repairs synapses by activating the mTOR pathway in Parkinson's disease depression model rats

Acupuncture is a good treatment for depression in Parkinson's disease (DPD), so the possible mechanism of acupuncture in the treatment of DPD was explored in this study. Firstly, observing the behavioral changes of the DPD rat model, the regulation of monoamine neurotransmitters dopamine (DA) and 5-hydroxytryptamine (5-HT) in the midbrain, the change of α-synuclein (α-syn) in the striatum, the efficacy of acupuncture in the treatment of DPD was discussed. Secondly, autophagy inhibitors and activators were selected to judge the effect of acupuncture on autophagy in the DPD rat model. Finally, an mTOR inhibitor was used to observe the effect of acupuncture on the mTOR pathway in the DPD rat model. The results showed that acupuncture could improve the motor and depressive symptoms of DPD model rats, increase the content of DA and 5-HT, and decrease the content of ɑ-syn in the striatum. Acupuncture inhibited the expression of autophagy in the striatum of DPD model rats. At the same time, acupuncture upregulates p-mTOR expression, inhibits autophagy, and promotes synaptic protein expression. Therefore, we concluded that acupuncture might improve the behavior of DPD model rats by activating the mTOR pathway, inhibiting autophagy from removing α-syn and repairing synapses.

mTORC1 syndrome (TorS): unified paradigm for diabetes/metabolic syndrome

'Glucolipotoxicity' and 'insulin resistance' are claimed to drive type 2 diabetes (T2D) and the non-glycemic diseases of the metabolic syndrome (MetS) (obesity, dyslipidemia, hypertension). In line with that, glycemic and/or insulin control are considered to be primary goal in treating T2D/MetS. However, recent standard-of-care (SOC) treatments of T2D, initially designed to control T2D hyperglycemia, appear now to alleviate the cardio-renal and non-glycemic diseases of T2D/MetS independently of glucose lowering and insulin resistance, and in non-T2D patients altogether, calling for an alternative unifying pathophysiology/treatment paradigm for T2D/MetS. This opinion article proposes to replace the current 'glucolipotoxic/insulin-resistance' paradigm of T2D/MetS with an 'mammalian target of rapamycin complex 1 (mTORC1) syndrome' (TorS) paradigm, implying an exhaustive cohesive disease entity driven by an upstream hyperactive mTORC1, and which includes diabetic hyperglycemia, diabetic dyslipidemia, hypertension, diabetic macrovascular and microvascular disease, non-alcoholic fatty liver disease, some cancers, neurodegeneration, polycystic ovary syndrome (PCOS), psoriasis, and others. The TorS paradigm may account for the insulin-resistant glycemic context of TorS, combined with response to insulin of the non-glycemic diseases of TorS. The TorS paradigm may account for the efficacy of current antidiabetic SOC treatments in diabetic and nondiabetic patients. Most importantly, the TorS paradigm may generate novel treatments for TorS.

The role of CaMKK2 in Golgi-associated vesicle trafficking

Calcium/calmodulin-dependent protein kinase kinase 2 (CaMKK2) is a serine/threonine-protein kinase, that is involved in maintaining various physiological and cellular processes within the cell that regulate energy homeostasis and cell growth. CaMKK2 regulates glucose metabolism by the activation of downstream kinases, AMP-activated protein kinase (AMPK) and other calcium/calmodulin-dependent protein kinases. Consequently, its deregulation has a role in multiple human metabolic diseases including obesity and cancer. Despite the importance of CaMKK2, its signalling pathways and pathological mechanisms are not completely understood. Recent work has been aimed at broadening our understanding of the biological functions of CaMKK2. These studies have uncovered new interaction partners that have led to the description of new functions that include lipogenesis and Golgi vesicle trafficking. Here, we review recent insights into the role of CaMKK2 in membrane trafficking mechanisms and discuss the functional implications in a cellular context and for disease.

Natural compounds from botanical drugs targeting mTOR signaling pathway as promising therapeutics for atherosclerosis: A review

Atherosclerosis (AS) is a chronic inflammatory disease that is a major cause of cardiovascular diseases (CVDs), including coronary artery disease, hypertension, myocardial infarction, and heart failure. Hence, the mechanisms of AS are still being explored. A growing compendium of evidence supports that the activity of the mechanistic/mammalian target of rapamycin (mTOR) is highly correlated with the risk of AS. The mTOR signaling pathway contributes to AS progression by regulating autophagy, cell senescence, immune response, and lipid metabolism. Various botanical drugs and their functional compounds have been found to exert anti- AS effects by modulating the activity of the mTOR signaling pathway. In this review, we summarize the pathogenesis of AS based on the mTOR signaling pathway from the aspects of immune response, autophagy, cell senescence, and lipid metabolism, and comb the recent advances in natural compounds from botanical drugs to inhibit the mTOR signaling pathway and delay AS development. This review will provide a new perspective on the mechanisms and precision treatments of AS.

Targeting Immune Senescence in Atherosclerosis

Atherosclerosis is one of the main underlying causes of cardiovascular diseases (CVD). It is associated with chronic inflammation and intimal thickening as well as the involvement of multiple cell types including immune cells. The engagement of innate or adaptive immune response has either athero-protective or atherogenic properties in exacerbating or alleviating atherosclerosis. In atherosclerosis, the mechanism of action of immune cells, particularly monocytes, macrophages, dendritic cells, and B- and T-lymphocytes have been discussed. Immuno-senescence is associated with aging, viral infections, genetic predispositions, and hyperlipidemia, which contribute to atherosclerosis. Immune senescent cells secrete SASP that delays or accelerates atherosclerosis plaque growth and associated pathologies such as aneurysms and coronary artery disease. Senescent cells undergo cell cycle arrest, morphological changes, and phenotypic changes in terms of their abundances and secretome profile including cytokines, chemokines, matrix metalloproteases (MMPs) and Toll-like receptors (TLRs) expressions. The senescence markers are used in therapeutics and currently, senolytics represent one of the emerging treatments where specific targets and clearance of senescent cells are being considered as therapy targets for the prevention or treatment of atherosclerosis.

The Less We Eat, the Longer We Live: Can Caloric Restriction Help Us Become Centenarians?

Striving for longevity is neither a recent human desire nor a novel scientific field. The first article on this topic was published in 1838, when the average human life expectancy was approximately 40 years. Although nowadays people on average live almost as twice as long, we still (and perhaps more than ever) look for new ways to extend our lifespan. During this seemingly endless journey of discovering efficient methods to prolong life, humans were enthusiastic regarding several approaches, one of which is caloric restriction (CR). Where does CR, initially considered universally beneficial for extending both lifespan and health span, stand today? Does a lifelong decrease in food consumption represent one of the secrets of centenarians’ long and healthy life? Do we still believe that if we eat less, we will live longer? This review aims to summarize the current literature on CR as a potential life-prolonging intervention in humans and discusses metabolic pathways that underlie this effect.

The role of eIF2 phosphorylation in cell and organismal physiology: new roles for well-known actors

Control of protein synthesis (mRNA translation) plays key roles in shaping the proteome and in many physiological, including homeostatic, responses. One long-known translational control mechanism involves phosphorylation of initiation factor, eIF2, which is catalysed by any one of four protein kinases, which are generally activated in response to stresses. They form a key arm of the integrated stress response (ISR). Phosphorylated eIF2 inhibits eIF2B (the protein that promotes exchange of eIF2-bound GDP for GTP) and thus impairs general protein synthesis. However, this mechanism actually promotes translation of certain mRNAs by virtue of specific features they possess. Recent work has uncovered many previously unknown features of this regulatory system. Several studies have yielded crucial insights into the structure and control of eIF2, including that eIF2B is regulated by several metabolites. Recent studies also reveal that control of eIF2 and the ISR helps determine organismal lifespan and surprising roles in sensing mitochondrial stresses and in controlling the mammalian target of rapamycin (mTOR). The latter effect involves an unexpected role for one of the eIF2 kinases, HRI. Phosphoproteomic analysis identified new substrates for another eIF2 kinase, Gcn2, which senses the availability of amino acids. Several genetic disorders arise from mutations in genes for eIF2α kinases or eIF2B (i.e. vanishing white matter disease, VWM and microcephaly, epileptic seizures, microcephaly, hypogenitalism, diabetes and obesity, MEHMO). Furthermore, the eIF2-mediated ISR plays roles in cognitive decline associated with Alzheimer's disease. New findings suggest potential therapeutic value in interfering with the ISR in certain settings, including VWM, for example by using compounds that promote eIF2B activity.