Cellular metabolic stress: considering how cells respond to nutrient excess. Mol Cell. 2010;40:323-332. [PMID: 20965425 DOI: 10.1016/j.molcel.2010.10.004]

Sestrin2 in POMC neurons modulates energy balance and obesity related metabolic disorders via mTOR signaling

Sestrin2 is a highly conserved protein that can be induced under various stress conditions. Researches have revealed that the signaling pathway of the mammalian target of rapamycin (mTOR) is essential in modulating both glucose and lipid metabolism. However, the precise involvement of Sestrin2 in the hypothalamus, particularly in pro-opiomelanocortin (POMC) neurons, in control of energy homeostasis remains uncertain. In this study, we aimed to investigate the functional role of Sestrin2 in hypothalamic POMC neurons in regulation of energy balance, as well as revealing the underlying mechanisms. Therefore, cre-dependent AAV virus encoding or silencing Sestrin2 was injected into the hypothalamic ARC of pomc-cre transgenic mice. The results demonstrated that Sestrin2 overexpression in POMC neurons ameliorated high-fat diet (HFD)-induced obesity and increased energy expenditure. Conversely, Sestrin2 deficiency in POMC neurons predisposed mice to HFD induced obesity. Additionally, the thermogenesis of brown adipose tissue and lipolysis of inguinal white adipose tissue were both enhanced by the increased sympathetic nerve innervation in Sestrin2 overexpressed mice. Further exploration revealed that Sestrin2 overexpression inhibited the mTOR signaling pathway in hypothalamic POMC neurons, which may account for the alleviation of systematic metabolic disturbance induced by HFD in these mice. Collectively, our findings demonstrate that Sestrin2 in POMC neurons plays a pivotal role in maintaining energy balance in a context of HFD-induced obesity by inhibiting the mTOR pathway, providing new insights into how hypothalamic neurons respond to nutritional signals to protect against obesity-associated metabolic dysfunction.

NPRL2 is required for proliferation of oncogenic Ras-transformed bronchial epithelial cells

Nitrogen permease regulator-like 2 (NPRL2/TUSC4) is known to exert both tumor-suppressing and oncogenic effects in different types of cancers, suggesting that its actions are context dependent. Here, we delineated the molecular and functional effects of NPRL2 in malignantly transformed bronchial epithelial cells. To do so, we depleted NPRL2 in oncogenic HRas-transduced and malignantly transformed human bronchial epithelial (BEAS2B), Ras-AI-T2 cells. Intriguingly, depletion of NPRL2 in these cells induced activation of mTORC1 downstream signaling, inhibited autophagy, and impaired Ras-AI-T2 cell proliferation both in vitro and in vivo. These results suggest that NPRL2 is required for oncogenic HRas-induced cell transformation. Depletion of NPRL2 increased levels of the DNA damage marker γH2AX, the cell cycle inhibitors p21 and p27, and the apoptosis marker cleaved-PARP. These NPRL2-depleted cells first accumulated at G1 and G2, and later exhibited signs of mitotic catastrophe, which implied that NPRL2 depletion may be detrimental to oncogenic HRas-transformed cells. Additionally, NPRL2 depletion reduced heat shock factor 1/heat shock element- and NRF2/antioxidant response element-directed luciferase reporter activities in Ras-AI-T2 cells, indicating that NPRL2 depletion led to the suppression of two key cytoprotective processes in oncogenic HRas-transformed cells. Overall, our data suggest that oncogenic HRas-transduced and malignantly transformed cells may depend on NPRL2 for survival and proliferation, and depletion of NPRL2 also induces a stressed state in these cells.

Extracellular domains of CARs reprogramme T cell metabolism without antigen stimulation

Metabolism is an indispensable part of T cell proliferation, activation and exhaustion, yet the metabolism of chimeric antigen receptor (CAR)-T cells remains incompletely understood. CARs are composed of extracellular domains-often single-chain variable fragments (scFvs)-that determine ligand specificity and intracellular domains that trigger signalling following antigen binding. Here, we show that CARs differing only in the scFv variously reprogramme T cell metabolism. Even without exposure to antigens, some CARs increase proliferation and nutrient uptake in T cells. Using stable isotope tracers and mass spectrometry, we observed basal metabolic fluxes through glycolysis doubling and amino acid uptake overtaking anaplerosis in CAR-T cells harbouring a rituximab scFv, unlike other similar anti-CD20 scFvs. Disparate rituximab and 14G2a-based anti-GD2 CAR-T cells are similarly hypermetabolic and channel excess nutrients to nitrogen overflow metabolism. Modest overflow metabolism of CAR-T cells and metabolic compatibility between cancer cells and CAR-T cells are identified as features of efficacious CAR-T cell therapy.

Glucose metabolism partially regulates β-cell function through epigenomic changes

The β-cell relies predominantly on glucose utilization to generate adenosine triphosphate, which is crucial for both cell viability and insulin secretion. The β-cell has evolved remarkable metabolic flexibility to productively respond to shifts in environmental conditions and changes in glucose availability. Although these adaptive responses are important for maintaining optimal cellular function, there is emerging evidence that the resulting changes in cellular metabolites can impact the epigenome, causing transient and lasting alterations in gene expression. This review explores the intricate interplay between metabolism and the epigenome, providing valuable insights into the molecular mechanisms leading to β-cell dysfunction in diabetes. Understanding these mechanisms will be critical for developing targeted therapeutic strategies to preserve and enhance β-cell function, offering potential avenues for interventions to improve glycemic control in individuals with diabetes.

The phospholipids cardiolipin and phosphatidylethanolamine differentially regulate MDC biogenesis

Cells utilize multiple mechanisms to maintain mitochondrial homeostasis. We recently characterized a pathway that remodels mitochondria in response to metabolic alterations and protein overload stress. This remodeling occurs via the formation of large membranous structures from the mitochondrial outer membrane called mitochondrial-derived compartments (MDCs), which are eventually released from mitochondria and degraded. Here, we conducted a microscopy-based screen in budding yeast to identify factors that regulate MDC formation. We found that two phospholipids, cardiolipin (CL) and phosphatidylethanolamine (PE), differentially regulate MDC biogenesis. CL depletion impairs MDC biogenesis, whereas blocking mitochondrial PE production leads to constitutive MDC formation. Additionally, in response to metabolic MDC activators, cellular and mitochondrial PE declines, and overexpressing mitochondrial PE synthesis enzymes suppress MDC biogenesis. Altogether, our data indicate a requirement for CL in MDC biogenesis and suggest that PE depletion may stimulate MDC formation downstream of MDC-inducing metabolic stress.

Effects of Reactive Oxygen and Nitrogen Species on Male Fertility

Significance: In recent decades, male fertility has been severely reduced worldwide. The causes underlying this decline are multifactorial, and include, among others, genetic alterations, changes in the microbiome, and the impact of environmental pollutants. Such factors can dysregulate the physiological levels of reactive species of oxygen (ROS) and nitrogen (RNS) in the patient, generating oxidative and nitrosative stress that impairs fertility. Recent Advances: Recent studies have delved into other factors involved in the dysregulation of ROS and RNS levels, such as diet, obesity, persistent infections, environmental pollutants, and gut microbiota, thus leading to new strategies to solve male fertility problems, such as consuming prebiotics to regulate gut flora or treating psychological conditions. Critical Issues: The pathways where ROS or RNS may be involved as modulators are still under investigation. Moreover, the extent to which treatments can rescue male infertility as well as whether they may have side effects remains, in most cases, to be elucidated. For example, it is known that prescription of antioxidants to treat nitrosative stress can alter sperm chromatin condensation, which makes DNA more exposed to ROS and RNS, and may thus affect fertilization and early embryo development. Future Directions: The involvement of extracellular vesicles, which might play a crucial role in cell communication during spermatogenesis and epididymal maturation, and the relevance of other factors such as sperm epigenetic signatures should be envisaged in the future.

Mechanisms of Biological Effects of Ionic Liquids: From Single Cells to Multicellular Organisms

The review presents a detailed discussion of the evolving field studying interactions between ionic liquids (ILs) and biological systems. Originating from molten salt electrolytes to present multiapplication substances, ILs have found usage across various fields due to their exceptional physicochemical properties, including excellent tunability. However, their interactions with biological systems and potential influence on living organisms remain largely unexplored. This review examines the cytotoxic effects of ILs on cell cultures, biomolecules, and vertebrate and invertebrate organisms. Our understanding of IL toxicity, while growing in recent years, is yet nascent. The established findings include correlations between harmful effects of ILs and their ability to disturb cellular membranes, their potential to trigger oxidative stress in cells, and their ability to cause cell death via apoptosis. Future research directions proposed in the review include studying the distribution of various ILs within cellular compartments and organelles, investigating metabolic transformations of ILs in cells and organisms, detailed analysis of IL effects on proteins involved in oxidative stress and apoptosis, correlation studies between IL doses, exposure times and resulting adverse effects, and examination of effects of subtoxic concentrations of ILs on various biological objects. This review aims to serve as a critical analysis of the current body of knowledge on IL-related toxicity mechanisms. Furthermore, it can guide researchers toward the design of less toxic ILs and the informed use of ILs in drug development and medicine.

The endogenous antioxidant ability of royal jelly in Drosophila is independent of Keap1/Nrf2 by activating oxidoreductase activity

Royal jelly (RJ) is a biologically active substance secreted by the hypopharyngeal and mandibular glands of worker honeybees. It is widely claimed that RJ reduces oxidative stress. However, the antioxidant activity of RJ has mostly been determined by in vitro chemical detection methods or by external administration drugs that cause oxidative stress. Whether RJ can clear the endogenous production of reactive oxygen species (ROS) in cells remains largely unknown. Here, we systematically investigated the antioxidant properties of RJ using several endogenous oxidative stress models of Drosophila. We found that RJ enhanced sleep quality of aging Drosophila, which is decreased due to an increase of oxidative damage with age. RJ supplementation improved survival and suppressed ROS levels in gut cells of flies upon exposure to hydrogen peroxide or to the neurotoxic agent paraquat. Moreover, RJ supplementation moderated levels of ROS in endogenous gut cells and extended lifespan after exposure of flies to heat stress. Sleep deprivation leads to accumulation of ROS in the gut cells, and RJ attenuated the consequences of oxidative stress caused by sleep loss and prolonged lifespan. Mechanistically, RJ prevented cell oxidative damage caused by heat stress or sleep deprivation, with the antioxidant activity in vivo independent of Keap1/Nrf2 signaling. RJ supplementation activated oxidoreductase activity in the guts of flies, suggesting its ability to inhibit endogenous oxidative stress and maintain health, possibly in humans.

Excessive Tryptophan and Phenylalanine Induced Pancreatic Injury and Glycometabolism Disorder in Grower-finisher Pigs

BACKGROUND

The increase in circulating insulin levels is associated with the onset of type 2 diabetes (T2D), and the levels of branched-chain amino acids and aromatic amino acids (AAAs) are altered in T2D, but whether AAAs play a role in insulin secretion and signaling remains unclear.

OBJECTIVES

This study aimed to investigate the effects of different AAAs on pancreatic function and on the use of insulin in finishing pigs.

METHODS

A total of 18 healthy finishing pigs (Large White) with average body weight of 100 ± 1.15 kg were randomly allocated to 3 dietary treatments: Con, a normal diet supplemented with 0.68% alanine; Phe, a normal diet supplemented with 1.26% phenylalanine; and Trp, a normal diet supplemented with 0.78% tryptophan. The 3 diets were isonitrogenous. There were 6 replicates in each group.

RESULTS

Herein, we investigated the effects of tryptophan and phenylalanine on pancreatic function and the use of insulin in finishing pigs and found that the addition of tryptophan and phenylalanine aggravated pancreatic fat deposition, increased the relative content of saturated fatty acids, especially palmitate (C16:0) and stearate (C18:0), and the resulting lipid toxicity disrupted pancreatic secretory function. We also found that tryptophan and phenylalanine inhibited the growth and secretion of β-cells, downregulated the gene expression of the PI3K/Akt pathway in the pancreas and liver, and reduced glucose utilization in the liver.

CONCLUSIONS

Using fattening pigs as a model, multiorgan combined analysis of the insulin-secreting organ pancreas and the main insulin-acting organ liver, excessive intake of tryptophan and phenylalanine will aggravate pancreatic damage leading to glucose metabolism disorders, providing new evidence for the occurrence and development of T2D.

PIM1 drives lipid droplet accumulation to promote proliferation and survival in prostate cancer

Lipid droplets (LDs) are dynamic organelles with a neutral lipid core surrounded by a phospholipid monolayer. Solid tumors exhibit LD accumulation, and it is believed that LDs promote cell survival by providing an energy source during energy deprivation. However, the precise mechanisms controlling LD accumulation and utilization in prostate cancer are not well known. Here, we show peroxisome proliferator-activated receptor α (PPARα) acts downstream of PIM1 kinase to accelerate LD accumulation and promote cell proliferation in prostate cancer. Mechanistically, PIM1 inactivates glycogen synthase kinase 3 beta (GSK3β) via serine 9 phosphorylation. GSK3β inhibition stabilizes PPARα and enhances the transcription of genes linked to peroxisomal biogenesis (PEX3 and PEX5) and LD growth (Tip47). The effects of PIM1 on LD accumulation are abrogated with GW6471, a specific inhibitor for PPARα. Notably, LD accumulation downstream of PIM1 provides a significant survival advantage for prostate cancer cells during nutrient stress, such as glucose depletion. Inhibiting PIM reduces LD accumulation in vivo alongside slow tumor growth and proliferation. Furthermore, TKO mice, lacking PIM isoforms, exhibit suppression in circulating triglycerides. Overall, our findings establish PIM1 as an important regulator of LD accumulation through GSK3β-PPARα signaling axis to promote cell proliferation and survival during nutrient stress.

Emerging role of lipophagy in liver disorders

Lipophagy is a selective degradation of lipids by a lysosomal-mediated pathway, and dysregulation of lipophagy is linked with the pathological hallmark of many liver diseases. Downregulation of lipophagy in liver cells results in abnormal accumulation of LDs (Lipid droplets) in hepatocytes which is a characteristic feature of several liver pathologies such as nonalcoholic fatty liver disease (NAFLD) and nonalcoholic steatohepatitis (NASH). Contrarily, upregulation of lipophagy in activated hepatic stellate cells (HSCs) is associated with hepatic fibrosis and cirrhosis. Lipid metabolism reprogramming in violent cancer cells contributes to the progression of liver cancer. In this review, we have summarized the recent studies focusing on various components of the lipophagic machinery that can be modulated for their potential role as therapeutic agents against a wide range of liver diseases.

SIRT7: the seventh key to unlocking the mystery of aging

Aging is a chronic yet natural physiological decline of the body. Throughout life, humans are continuously exposed to a variety of exogenous and endogenous stresses, which engender various counteractive responses at the cellular, tissue, organ, as well as organismal levels. The compromised cellular and tissue functions that occur because of genetic factors or prolonged stress (or even the stress response) may accelerate aging. Over the last two decades, the sirtuin (SIRT) family of lysine deacylases has emerged as a key regulator of longevity in a variety of organisms. SIRT7, the most recently identified member of the SIRTs, maintains physiological homeostasis and provides protection against aging by functioning as a watchdog of genomic integrity, a dynamic sensor and modulator of stresses. SIRT7 decline disrupts metabolic homeostasis, accelerates aging, and increases the risk of age-related pathologies including cardiovascular and neurodegenerative diseases, pulmonary and renal disorders, inflammatory diseases, and cancer, etc. Here, we present SIRT7 as the seventh key to unlock the mystery of aging, and its specific manipulation holds great potential to ensure healthiness and longevity.

Immunity-linked genes are stimulated by a membrane stress pathway linked to Golgi function and the ARF-1 GTPase

Infection response and other immunity-linked genes (ILGs) were first named in Caenorhabditis elegans-based expression after pathogen challenge, but many are also up-regulated when lipid metabolism is perturbed. Why pathogen attack and metabolic changes both increase ILGs is unclear. We find that ILGs are activated when phosphatidylcholine (PC) levels change in membranes of secretory organelles in C. elegans. RNAi targeting of the ADP-ribosylation factor arf-1, which disrupts the Golgi and secretory function, also activates ILGs. Low PC limits ARF-1 function, suggesting a mechanism for ILG activation via lipid metabolism, as part of a membrane stress response acting outside the ER. RNAi of selected ILGs uncovered defects in the secretion of two GFP reporters and the accumulation of a pathogen-responsive complement C1r/C1s, Uegf, Bmp1 (CUB) domain fusion protein. Our data argue that up-regulation of some ILGs is a coordinated response to changes in trafficking and may act to counteract stress on secretory function.

An adaptive stress response that confers cellular resilience to decreased ubiquitination

Ubiquitination is a post-translational modification initiated by the E1 enzyme UBA1, which transfers ubiquitin to ~35 E2 ubiquitin-conjugating enzymes. While UBA1 loss is cell lethal, it remains unknown how partial reduction in UBA1 activity is endured. Here, we utilize deep-coverage mass spectrometry to define the E1-E2 interactome and to determine the proteins that are modulated by knockdown of UBA1 and of each E2 in human cells. These analyses define the UBA1/E2-sensitive proteome and the E2 specificity in protein modulation. Interestingly, profound adaptations in peroxisomes and other organelles are triggered by decreased ubiquitination. While the cargo receptor PEX5 depends on its mono-ubiquitination for binding to peroxisomal proteins and importing them into peroxisomes, we find that UBA1/E2 knockdown induces the compensatory upregulation of other PEX proteins necessary for PEX5 docking to the peroxisomal membrane. Altogether, this study defines a homeostatic mechanism that sustains peroxisomal protein import in cells with decreased ubiquitination capacity.

Heat shock response in Sulfolobus acidocaldarius and first implications for cross-stress adaptation

Sulfolobus acidocaldarius, a thermoacidophilic crenarchaeon, frequently encounters temperature fluctuations, oxidative stress, and nutrient limitations in its environment. Here, we employed a high-throughput transcriptomic analysis to examine how the gene expression of S. acidocaldarius changes when exposed to high temperatures (92 °C). The data obtained was subsequently validated using quantitative reverse transcription-PCR (qRT-PCR) analysis. Our particular focus was on genes that are involved in the heat shock response, type-II Toxin-Antitoxin systems, and putative transcription factors. To investigate how S. acidocaldarius adapts to multiple stressors, we assessed the expression of these selected genes under oxidative and nutrient stresses using qRT-PCR analysis. The results demonstrated that the gene thβ encoding the β subunit of the thermosome, as well as hsp14 and hsp20, play crucial roles in the majority of stress conditions. Furthermore, we observed overexpression of at least eight different TA pairs belonging to the type II TA systems under all stress conditions. Additionally, four common transcription factors: FadR, TFEβ, CRISPR loci binding protein, and HTH family protein were consistently overexpressed across all stress conditions, indicating their significant role in managing stress. Overall, this work provides the first insight into molecular players involved in the cross-stress adaptation of S. acidocaldarius.

Clozapine suppresses NADPH oxidase activation, counteracts cytosolic H2O2, and triggers early onset mitochondrial dysfunction during adipogenesis of human liposarcoma SW872 cells

Long-term treatment of schizophrenia with clozapine (CLZ), an atypical antipsychotic drug, is associated with an increased incidence of metabolic disorders mediated by poorly understood mechanisms. We herein report that CLZ, while slowing down the morphological changes and lipid accumulation occurring during SW872 cell adipogenesis, also causes an early (day 3) inhibition of the expression/nuclear translocation of CAAT/enhancer-binding protein β and peroxisome proliferator-activated receptor γ. Under the same conditions, CLZ blunts NADPH oxidase-derived reactive oxygen species (ROS) by a dual mechanism involving enzyme inhibition and ROS scavenging. These effects were accompanied by hampered activation of the nuclear factor (erythroid-derived2)-like 2 (Nrf2)-dependent antioxidant responses compared to controls, and by an aggravated formation of mitochondrial superoxide. CLZ failed to exert ROS scavenging activities in the mitochondrial compartment but appeared to actively scavenge cytosolic H2O2 derived from mitochondrial superoxide. The early formation of mitochondrial ROS promoted by CLZ was also associated with signs of mitochondrial dysfunction. Some of the above findings were recapitulated using mouse embryonic fibroblasts. We conclude that the NADPH oxidase inhibitory and cytosolic ROS scavenging activities of CLZ slow down SW872 cell adipogenesis and suppress their Nrf2 activation, an event apparently connected with increased mitochondrial ROS formation, which is associated with insulin resistance and metabolic syndrome. Thus, the cellular events characterised herein may help to shed light on the more detailed molecular mechanisms explaining some of the adverse metabolic effects of CLZ.

Pharmacological HDAC inhibition impairs pancreatic β-cell function through an epigenome-wide reprogramming

Histone deacetylases enzymes (HDACs) are chromatin modifiers that regulate gene expression through deacetylation of lysine residues within specific histone and non-histone proteins. A cell-specific gene expression pattern defines the identity of insulin-producing pancreatic β cells, yet molecular networks driving this transcriptional specificity are not fully understood. Here, we investigated the HDAC-dependent molecular mechanisms controlling pancreatic β-cell identity and function using the pan-HDAC inhibitor trichostatin A through chromatin immunoprecipitation assays and RNA sequencing experiments. We observed that TSA alters insulin secretion associated with β-cell specific transcriptome programming in both mouse and human β-cell lines, as well as on human pancreatic islets. We also demonstrated that this alternative β-cell transcriptional program in response to HDAC inhibition is related to an epigenome-wide remodeling at both promoters and enhancers. Our data indicate that HDAC activity could be required to protect against loss of β-cell identity with unsuitable expression of genes associated with alternative cell fates.

Lipid droplets: a cellular organelle vital in cancer cells

Lipid droplets (LDs) are cellular organelles comprising a core of neutral lipids (glycerides, sterols) encased within a single phospholipid membrane, responsible for storing surplus lipids and furnishing cellular energy. LDs engage in lipid synthesis, catabolism, and transport processes by interacting with other organelles (e.g., endoplasmic reticulum, mitochondria), and they play critical roles in regulating cellular stress and immunity. Recent research has uncovered that an elevated number of LDs is a hallmark of cancer cells, attributable to their enhanced lipid uptake and synthesis capacity, with lipids stored as LDs. Depletion of LDs in cancer cells induces apoptosis, prompting the emergence of small molecule antitumor drugs targeting LDs or key factors (e.g., FASN, SCD1) within the lipid synthesis pathway. Advancements in LD isolation and artificial synthesis have demonstrated their potential applicability in antitumor research. LDs extracted from murine adipose tissue and incubated with lipophilic antitumor drugs yield drug-coated LDs, which promote apoptosis in cancer cells. Furthermore, LDs have been employed as biological lenses to augment the resolution of subcellular structures (microfilaments, microtubules), facilitating the observation of intricate structures within thicker cells, including cancer cells. This review delineates the functional and metabolic mechanisms of LDs in cancer cells and encapsulates recent progress in LD-centered antitumor research, offering novel insights for tumor diagnosis and treatment.

Glc7/PP1 dephosphorylates histone H3T11 to regulate autophagy and telomere silencing in response to nutrient availability

How cells adapt their gene expression to nutritional changes remains poorly understood. Histone H3T11 is phosphorylated by pyruvate kinase to repress gene transcription. Here, we identify the protein phosphatase 1 (PP1), Glc7 as the enzyme that specifically dephosphorylates H3T11. We also characterize two novel Glc7-containing complexes and reveal their roles in regulating gene expression upon glucose starvation. Specifically, the Glc7-Sen1 complex dephosphorylates H3T11 to activate the transcription of autophagy-related genes. The Glc7-Rif1-Rap1 complex dephosphorylates H3T11 to derepress the transcription of telomere-proximal genes. Upon glucose starvation, Glc7 expression is up-regulated and more Glc7 translocates into the nucleus to dephosphorylate H3T11, leading to induction of autophagy and derepressed transcription of telomere-proximal genes. Furthermore, the functions of PP1/Glc7 and the two Glc7-containing complexes are conserved in mammals to regulate autophagy and telomere structure. Collectively, our results reveal a novel mechanism that regulate gene expression and chromatin structure in response to glucose availability.

Metabolic Priming as a Tool in Redox and Mitochondrial Theragnostics

Theragnostics is a promising approach that integrates diagnostics and therapeutics into a single personalized strategy. To conduct effective theragnostic studies, it is essential to create an in vitro environment that accurately reflects the in vivo conditions. In this review, we discuss the importance of redox homeostasis and mitochondrial function in the context of personalized theragnostic approaches. Cells have several ways to respond to metabolic stress, including changes in protein localization, density, and degradation, which can promote cell survival. However, disruption of redox homeostasis can lead to oxidative stress and cellular damage, which are implicated in various diseases. Models of oxidative stress and mitochondrial dysfunction should be developed in metabolically conditioned cells to explore the underlying mechanisms of diseases and develop new therapies. By choosing an appropriate cellular model, adjusting cell culture conditions and validating the cellular model, it is possible to identify the most promising therapeutic options and tailor treatments to individual patients. Overall, we highlight the importance of precise and individualized approaches in theragnostics and the need to develop accurate in vitro models that reflect the in vivo conditions.

Modeling the effect of oxidative stress on Bordetella pertussis fermentations

A mathematical model is proposed for Bordetella pertussis with the main goal to better understand and describe the relation between cell growth, oxidative stress and NADPH levels under different oxidative conditions. The model is validated with flask experiments conducted under different conditions of oxidative stress induced by high initial glutamate concentrations, low initial inoculum and secondary culturing following exposure to starvation. The model exhibited good accuracy when calibrated and validated for the different experimental conditions. From comparisons of model predictions to data with different model mechanisms, it was concluded that intracellular reactive oxidative species only have an indirect effect on growth rate by reacting with NADPH and thereby reducing the amount of NADPH that is available for growth.

Regulative Roles of Metabolic Plasticity Caused by Mitochondrial Oxidative Phosphorylation and Glycolysis on the Initiation and Progression of Tumorigenesis

One important feature of tumour development is the regulatory role of metabolic plasticity in maintaining the balance of mitochondrial oxidative phosphorylation and glycolysis in cancer cells. In recent years, the transition and/or function of metabolic phenotypes between mitochondrial oxidative phosphorylation and glycolysis in tumour cells have been extensively studied. In this review, we aimed to elucidate the characteristics of metabolic plasticity (emphasizing their effects, such as immune escape, angiogenesis migration, invasiveness, heterogeneity, adhesion, and phenotypic properties of cancers, among others) on tumour progression, including the initiation and progression phases. Thus, this article provides an overall understanding of the influence of abnormal metabolic remodeling on malignant proliferation and pathophysiological changes in carcinoma.

Extracellular Domains of CAR Reprogram T-Cell Metabolism Without Antigen Stimulation

Metabolism is an indispensable part of T-cell proliferation, activation, and exhaustion, yet the metabolism of chimeric antigen receptor (CAR)-T cells remains incompletely understood. CARs are comprised of extracellular domains that determine cancer specificity, often using single-chain variable fragments (scFvs), and intracellular domains that trigger signaling upon antigen binding. Here we show that CARs differing only in the scFv reprogram T-cell metabolism differently. Even in the absence of antigens, some CARs increase proliferation and nutrient uptake in T cells. Using stable isotope tracers and mass spectrometry, we observe basal metabolic fluxes through glycolysis doubling and amino acid uptake overtaking anaplerosis in CAR-T cells harboring rituximab scFv, unlike other similar anti-CD20 scFvs. Disparate rituximab and 14g2a-based anti-GD2 CAR-T cells are similarly hypermetabolic and channel excess nutrients to nitrogen overflow metabolism. Since CAR-dependent metabolic reprogramming alters cellular energetics, nutrient utilization, and proliferation, metabolic profiling should be an integral part of CAR-T cell development.

Metaboverse enables automated discovery and visualization of diverse metabolic regulatory patterns

Metabolism is intertwined with various cellular processes, including controlling cell fate, influencing tumorigenesis, participating in stress responses and more. Metabolism is a complex, interdependent network, and local perturbations can have indirect effects that are pervasive across the metabolic network. Current analytical and technical limitations have long created a bottleneck in metabolic data interpretation. To address these shortcomings, we developed Metaboverse, a user-friendly tool to facilitate data exploration and hypothesis generation. Here we introduce algorithms that leverage the metabolic network to extract complex reaction patterns from data. To minimize the impact of missing measurements within the network, we introduce methods that enable pattern recognition across multiple reactions. Using Metaboverse, we identify a previously undescribed metabolite signature that correlated with survival outcomes in early stage lung adenocarcinoma patients. Using a yeast model, we identify metabolic responses suggesting an adaptive role of citrate homeostasis during mitochondrial dysfunction facilitated by the citrate transporter, Ctp1. We demonstrate that Metaboverse augments the user's ability to extract meaningful patterns from multi-omics datasets to develop actionable hypotheses.

In-line monitoring of Bordetella pertussis cultivation using fluorescence spectroscopy

Fluorescence spectroscopy is a non-invasive and highly sensitive method for bioprocess monitoring. The use of fluorescence spectroscopy is not very well established in the industry for in-line monitoring. In the present work, a 2-D fluorometer with two excitation lights (365 and 405 nm) and emission spectra in the range of 350-850 nm were used for in-line monitoring of two strains of Bordetella pertussis cultivation operated in batch and fed batch. A Partial Least Squares (PLS) based regression model was used for the estimation of cell biomass, amino acids (glutamate and proline) and antigen (Pertactin) produced. It was observed that accurate predictions were achieved when models were calibrated separately for each cell strain and nutrient media formulation. Also, prediction accuracy was improved when dissolved oxygen, agitation and culture volume are added as additional features in the regression model. The proposed approach of combining in-line fluorescence and other online measurements is shown to have good potential for in-line monitoring of bioprocesses.

New insights into the oxidative damage and antioxidant defense mechanism in Manila clams (Ruditapes philippinarum) exposed to 8:2 polyfluoroalkyl phosphate diester stress

8:2 perfluoroalkyl phosphate diester (8:2 diPAP) is the main precursor of perfluoroalkyl carboxylic acids, and it has been detected in a wide range of environments. In this study, conventional biochemical and histopathological analyses and transcriptome methods were used to investigate the accumulation and oxidative stress of 8:2 diPAP in Manila clams (Ruditapes philippinarum) as well as the clam's defense mechanisms for the first time. The hepatopancreas was the main target organ for 8:2 diPAP accumulation; the concentration reached 484.0 ± 15.5 ng/g after 7 days of exposure to 10 μg/L of 8:2 diPAP, which was 2-100 times higher than that found in other organs. 8:2 diPAP accumulation resulted in significant lipid peroxidation, and the change in malondialdehyde content was highly correlated with 8:2 diPAP accumulation (r > 0.8). The antioxidant enzymes catalase and peroxidase were significantly activated at 7 days of exposure. Although the levels subsequently returned to normal, this restoration was unable to prevent damage. Histopathological analysis showed that 8:2 diPAP exposure resulted in inflammatory damage to the hepatopancreas, which failed to resolve during the recovery period. Transcriptomic analyses showed that the expression of differentially expressed genes had different degrees of positive/negative correlation with antioxidant indicators, and they were significantly enriched in cell death regulatory pathways such as autophagy, apoptosis, and necrosis. The core factor expression results indicated that 8:2 diPAP exposure induced activation of the organismal autophagy factor followed by a shift towards apoptosis. In addition, pathways related to amino acid metabolism and energy metabolism were involved in determining the cell fate of Manila clams. Overall, these results indicated that 8:2 diPAP induced peroxidation of membrane lipids, disturbed physiological processes, and ultimately initiated programmed cell death in Manila clams. The findings of this study provide new insights into the mechanism of toxicity of 8:2 diPAP exposure in marine bivalves.

ROS elevate HIF-1α phosphorylation for insect lifespan through the CK2-MKP3-p38 pathway

Diapause in insects is akin to dauer in Caenorhabditis elegans and hibernation in vertebrates, characterized by metabolic depression and lifespan extension. Previous studies have shown that reactive oxygen species (ROS) and hypoxia-inducible factor-1α (HIF-1α) in brains of diapause-destined pupae are more abundant than those in nondiapause-destined pupae in Helicoverpa armigera, but the ROS regulating HIF-1α activity remain unknown. Here, we showed that high ROS levels in brains of diapause-destined pupae resulted in low casein kinase 2 (CK2) activity and that downregulation of CK2 caused low expression of mitogen-activated protein kinase phosphatase 3 (MKP3), which is an inhibitor of p-p38. Thus, high p-p38 levels accumulate to improve HIF-1α activity via activating HIF-1α phosphorylation at the S732 residue to regulate insect diapause. This is the first report showing that a new pathway, ROS-CK2-MKP3-p38, regulates HIF-1α activity for lifespan in insects.

Activation of protein arginine methyltransferase 1 and subsequent extension of moth lifespan is effected by the ROS/JNK/CREB signaling axis

Previous studies have demonstrated that high physiological levels of reactive oxygen species induce pupal diapause and extend lifespan in the moth Helicoverpa armigera. This has been shown to occur via protein arginine methyltransferase 1 (PRMT1) blockade of Akt-mediated phosphorylation of the transcription factor FoxO, after which activated FoxO promotes the initiation of diapause. However, it is unclear how PRMT1 is activated upstream of FoxO activity. Here, we show that high reactive oxygen species levels in the brains of H. armigera diapause-destined pupae activate the expression of c-Jun N-terminal kinase, which subsequently activates the transcription factor cAMP-response element binding protein. We show that cAMP-response element binding protein then directly binds to the PRMT1 promoter and upregulates its expression to prevent Akt-mediated FoxO phosphorylation and downstream FoxO nuclear localization. This novel finding that c-Jun N-terminal kinase promotes FoxO nuclear localization in a PRMT1-dependent manner to regulate pupal diapause reveals a complex regulatory mechanism in extending the healthspan of H. armigera.

Behind the Curtain: In Silico and In Vitro Experiments Brought to Light New Insights into the Anticryptococcal Action of Synthetic Peptides

Cryptococcus neoformans is the pathogen responsible for cryptococcal pneumonia and meningitis, mainly affecting patients with suppressed immune systems. We have previously revealed the mechanism of anticryptococcal action of synthetic antimicrobial peptides (SAMPs). In this study, computational and experimental analyses provide new insights into the mechanisms of action of SAMPs. Computational analysis revealed that peptides interacted with the PHO36 membrane receptor of C. neoformans. Additionally, ROS (reactive oxygen species) overproduction, the enzymes of ROS metabolism, interference in the ergosterol biosynthesis pathway, and decoupling of cytochrome c mitochondrial membrane were evaluated. Three of four peptides were able to interact with the PHO36 receptor, altering its function and leading to ROS overproduction. SAMPs-treated C. neoformans cells showed a decrease in scavenger enzyme activity, supporting ROS accumulation. In the presence of ascorbic acid, an antioxidant agent, SAMPs did not induce ROS accumulation in C. neoformans cells. Interestingly, two SAMPs maintained inhibitory activity and membrane pore formation in C. neoformans cells by a ROS-independent mechanism. Yet, the ergosterol biosynthesis and lactate dehydrogenase activity were affected by SAMPs. In addition, we noticed decoupling of Cyt c from the mitochondria, which led to apoptosis events in the cryptococcal cells. The results presented herein suggest multiple mechanisms imposed by SAMPs against C. neoformans interfering in the development of resistance, thus revealing the potential of SAMPs in treating infections caused by C. neoformans.

Stress Granules in Cancer

The capacity of cells to organize complex biochemical reactions in intracellular space is a fundamental organizational principle of life. Key to this organization is the compartmentalization of the cytoplasm into distinct organelles, which is frequently achieved through intracellular membranes. Recent evidence, however, has added a new layer of flexibility to cellular compartmentalization. As such, in response to specific stimuli, liquid-liquid phase separations can lead to the rapid rearrangements of the cytoplasm to form membraneless organelles. Stress granules (SGs) are one such type of organelle that form specifically when cells are faced with stress stimuli, to aid cells in coping with stress. Inherently, altered SG formation has been linked to the pathogenesis of diseases associated with stress and inflammatory conditions, including cancer. Exciting discoveries have indicated an intimate link between SGs and tumorigenesis. Several pro-tumorigenic signaling molecules including the RAS oncogene, mTOR, and histone deacetylase 6 (HDAC6) have been shown to upregulate SG formation. Based on these studies, SGs have emerged as structures that can integrate oncogenic signaling and tumor-associated stress stimuli to enhance cancer cell fitness. In addition, growing evidence over the past decade suggests that SGs function not only to regulate the switch between survival and cell death, but also contribute to cancer cell proliferation, invasion, metastasis, and drug resistance. Although much remains to be learned about the role of SGs in tumorigenesis, these studies highlight SGs as a key regulatory hub in cancer and a promising therapeutic target.

Physiological and transcriptome analysis of Candida albicans in response to X33 antimicrobial oligopeptide treatment

Introduction

Candida albicans is an opportunistic pathogenic fungus, which frequently causes systemic or local fungal infections in humans. The evolution of its drug-resistant mutants necessitate an urgent development of novel antimicrobial agents.

Results

Here, we explored the antimicrobial activity and inhibitory mechanisms of X33 antimicrobial oligopeptide (X33 AMOP) against C. albicans. The oxford cup test results showed that X33 AMOP had strong inhibitory activity against C. albicans, and its MIC and MFC were 0.625 g/L and 2.5 g/L, respectively. Moreover, SEM and TEM showed that X33 AMOP disrupted the integrity of cell membrane. The AKP, ROS, H₂O₂ and MDA contents increased, while the reducing sugar, soluble protein, and pyruvate contents decreased after the X33 AMOP treatment. This indicated that X33 AMOP could damage the mitochondrial integrity of the cells, thereby disrupting the energy metabolism by inducing oxidative stress in C. albicans. Furthermore, transcriptome analysis showed that X33 AMOP treatment resulted in the differential expression of 1140 genes, among which 532 were up-regulated, and 608 were down-regulated. These DEGs were related to protein, nucleic acid, and carbohydrate metabolism, and their expression changes were consistent with the changes in physiological characteristics. Moreover, we found that X33 AMOP could effectively inhibit the virulence attributes of C. albicans by reducing phospholipase activity and disrupting hypha formation.

Discussion

These findings provide the first-ever detailed reference for the inhibitory mechanisms of X33 AMOP against C. albicans and suggest that X33 AMOP is a potential drug candidate for treating C. albicans infections.

Mitochondrial function and nutrient sensing pathways in ageing: enhancing longevity through dietary interventions

Ageing is accompanied by alterations in several biochemical processes, highly influenced by its environment. It is controlled by the interactions at various levels of biological hierarchy. To maintain homeostasis, a number of nutrient sensors respond to the nutritional status of the cell and control its energy metabolism. Mitochondrial physiology is influenced by the energy status of the cell. The alterations in mitochondrial physiology and the network of nutrient sensors result in mitochondrial damage leading to age related metabolic degeneration and diseases. Calorie restriction (CR) has proved to be as the most successful intervention to achieve the goal of longevity and healthspan. CR elicits a hormetic response and regulates metabolism by modulating these networks. In this review, the authors summarize the interdependent relationship between mitochondrial physiology and nutrient sensors during the ageing process and their role in regulating metabolism.

Cerebral Oxygen Delivery and Consumption in Brain-Injured Patients

Organism survival depends on oxygen delivery and utilization to maintain the balance of energy and toxic oxidants production. This regulation is crucial to the brain, especially after acute injuries. Secondary insults after brain damage may include impaired cerebral metabolism, ischemia, intracranial hypertension and oxygen concentration disturbances such as hypoxia or hyperoxia. Recent data highlight the important role of clinical protocols in improving oxygen delivery and resulting in lower mortality in brain-injured patients. Clinical protocols guide the rules for oxygen supplementation based on physiological processes such as elevation of oxygen supply (by mean arterial pressure (MAP) and intracranial pressure (ICP) modulation, cerebral vasoreactivity, oxygen capacity) and reduction of oxygen demand (by pharmacological sedation and coma or hypothermia). The aim of this review is to discuss oxygen metabolism in the brain under different conditions.

Stem cell microencapsulation maintains stemness in inflammatory microenvironment

Maintaining the stemness of the transplanted stem cell spheroids in an inflammatory microenvironment is challenging but important in regenerative medicine. Direct delivery of stem cells to repair periodontal defects may yield suboptimal effects due to the complexity of the periodontal inflammatory environment. Herein, stem cell spheroid is encapsulated by interfacial assembly of metal-phenolic network (MPN) nanofilm to form a stem cell microsphere capsule. Specifically, periodontal ligament stem cells (PDLSCs) spheroid was coated with Fe^III/tannic acid coordination network to obtain spheroid@[Fe^III-TA] microcapsules. The formed biodegradable MPN biointerface acted as a cytoprotective barrier and exhibited antioxidative, antibacterial and anti-inflammatory activities, effectively remodeling the inflammatory microenvironment and maintaining the stemness of PDLSCs. The stem cell microencapsulation proposed in this study can be applied to multiple stem cells with various functional metal ion/polyphenol coordination, providing a simple yet efficient delivery strategy for stem cell stemness maintenance in an inflammatory environment toward a better therapeutic outcome.

Actin dynamics in protein homeostasis

Cell homeostasis is maintained in all organisms by the constant adjustment of cell constituents and organisation to account for environmental context. Fine-tuning of the optimal balance of proteins for the conditions, or protein homeostasis, is critical to maintaining cell homeostasis. Actin, a major constituent of the cytoskeleton, forms many different structures which are acutely sensitive to the cell environment. Furthermore, actin structures interact with and are critically important for the function and regulation of multiple factors involved with mRNA and protein production and degradation, and protein regulation. Altogether, actin is a key, if often overlooked, regulator of protein homeostasis across eukaryotes. In this review, we highlight these roles and how they are altered following cell stress, from mRNA transcription to protein degradation.

Interplays of glucose metabolism and KRAS mutation in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive and deadliest cancer worldwide. The primary reasons for this are the lack of early detection methods and targeted therapy. Emerging evidence highlights the metabolic addiction of cancer cells as a potential target to combat PDAC. Oncogenic mutations of KRAS are the most common triggers that drive glucose uptake and utilization via metabolic reprogramming to support PDAC growth. Conversely, high glucose levels in the pancreatic microenvironment trigger genome instability and de novo mutations, including KRAS^G12D, in pancreatic cells through metabolic reprogramming. Here, we review convergent and diverse metabolic networks related to oncogenic KRAS mutations between PDAC initiation and progression, emphasizing the interplay among oncogenic mutations, glucose metabolic reprogramming, and the tumor microenvironment. Recognizing cancer-related glucose metabolism will provide a better strategy to prevent and treat the high risk PDAC population.

Tumor accomplice: T cell exhaustion induced by chronic inflammation

The development and response to treatment of tumor are modulated by inflammation, and chronic inflammation promotes tumor progression and therapy resistance. This article summarizes the dynamic evolution of inflammation from acute to chronic in the process of tumor development, and its effect on T cells from activation to the promotion of exhaustion. We review the mechanisms by which inflammatory cells and inflammatory cytokines regulate T cell exhaustion and methods for targeting chronic inflammation to improve the efficacy of immunotherapy. It is great significance to refer to the specific state of inflammation and T cells at different stages of tumor development for accurate clinical decision-making of immunotherapy and improving the efficiency of tumor immunotherapy.

PGM3 regulates beta-catenin activity to promote colorectal cancer cell progression

The hexosamine biosynthetic pathway (HBP) is connected to abnormal N- and O-linked protein glycosylation in cancer, which performs critical roles in tumorigenesis. However, the regulation mechanisms of HBP and its role in colorectal cancer (CRC) progression remain unexplained. This study analyzed the expression level of phosphoglucomutase 3 (PGM3), a key enzyme in HBP, and identified its function in CRC cell lines. Analysis of publicly available CRC microarray data determined that PGM3 is upregulated in CRC tumor tissues. Furthermore, functional experiments emphasized the significant roles of PGM3 in facilitating CRC cell proliferation and migration. Mechanistically, we demonstrated that the activity of β-catenin in CRC was maintained by PGM3-mediated O-GlcNAcylation. PGM3 knockdown or inhibition of O-GlcNAc transferase decreased β-catenin activity and the expression levels of its downstream targets. Collectively, our findings indicate that PGM3 exhibits tumor-promoting roles by elevating O-GlcNAcylation level and maintaining β-catenin activity, and might serve as a prognostic biomarker and treatment target in CRC.

Endo-M Mediated Chemoenzymatic Approach Enables Reversible Glycopeptide Labeling for O-GlcNAcylation Analysis

To selectively enrich O-linked β-N-acetylglucosamine (O-GlcNAc) peptides in their original form from complex samples, we report the first reversible chemoenzymatic labeling approach for proteomic analysis. In this strategy, the O-GlcNAc moieties are ligated with long N-glycans using an Endo-M mutant, which enables the enrichment of the labeled glycopeptides by hydrophilic interaction liquid chromatography (HILIC). The attached glycans on the enriched glycopeptides are removed by wild-type Endo-M/S to restore the O-GlcNAc moiety. Compared with classic chemoenzymatic labeling, this approach enables the tag-free identification, and eliminates the interference of bulky tags in glycopeptide detection. This approach presents a unique avenue for the proteome-wide analysis of protein O-GlcNAcylation to promote its mechanism research.

Long noncoding RNA CASC7 is a novel regulator of glycolysis in oesophageal cancer via a miR-143-3p-mediated HK2 signalling pathway

Long noncoding RNAs have been proven to play a crucial role in many tumours. Here, we explored the role of the lncRNA cancer susceptibility candidate 7 (CASC7) in oesophageal cancer. LncRNA CASC7 was identified in our database analysis, and we found that it was significantly higher in oesophageal tumour tissue than in normal tissue and that high expression of lncRNA CASC7 predicted a poor prognosis. Furthermore, we verified through cell experiments that low expression of lncRNA CASC7 in oesophageal cancer cells significantly inhibited tumour proliferation, which could be explained by the effect of lncRNA CASC7 on aerobic glycolysis. Next, we found that the expression of CASC7 and hexokinase 2 (HK2) in oesophageal cancer was positively correlated in database analysis, and this conclusion was further verified in cell experiments. To determine the mechanism, we found that miR-143-3p can bind to both lncRNA CASC7 and HK2. In clinical specimens, we also found high expression of lncRNA CASC7 in tumours, and the expression levels of lncRNA CASC7 and HK2 were positively correlated. In conclusion, downregulating lncRNA CASC7 could inhibit tumour proliferation by reducing glycolysis through the miR-143-3p/HK2 axis.

Control of topoisomerase II activity and chemotherapeutic inhibition by TCA cycle metabolites

Topoisomerase II (topo II) is essential for disentangling newly replicated chromosomes. DNA unlinking involves the physical passage of one duplex through another and depends on the transient formation of double-stranded DNA breaks, a step exploited by frontline chemotherapeutics to kill cancer cells. Although anti-topo II drugs are efficacious, they also elicit cytotoxic side effects in normal cells; insights into how topo II is regulated in different cellular contexts is essential to improve their targeted use. Using chemical fractionation and mass spectrometry, we have discovered that topo II is subject to metabolic control through the TCA cycle. We show that TCA metabolites stimulate topo II activity in vitro and that levels of TCA flux modulate cellular sensitivity to anti-topo II drugs in vivo. Our work reveals an unanticipated connection between the control of DNA topology and cellular metabolism, a finding with ramifications for the clinical use of anti-topo II therapies.

Leptin Level in Obese Children with Vitamin D Deficiency

Introduction: Vitamin D contributes to leptin synthesis through its effects on adipogenesis, the regulation of pro-inflammatory cytokines, and its effect on mRNA leptin. The purpose of this study is to determine the correlation of leptin and vitamin D deficiency and in children with obesity. Methods: This cross-sectional study was conducted from December 2019 to February 2020 and was chosen using multistage cluster random sampling with the target of junior high and high school students in Makassar city who met the obesity criteria. The subjects were divided into obese children with vitamin D deficiency group and obese children without vitamin D deficiency group. Results: The occurrence of hyperleptinemia in children with obesity and vitamin D deficiency was 42 (82.4 %), while it was 1 (2.2%) in children with obesity but no vitamin D deficiency, with a statistical analysis showing a value of p=0.000 and an OR value of 205.333. The leptin levels’ mean value in children with obesity and vitamin D deficiency was 31.67 ng/mL, while it was 5.13 ng/mL in the group without vitamin D deficiency. A Spearman correlation analysis of vitamin D and leptin levels revealed a negative correlation with p = 0.000 and r = -0.817. Conclusion: The level of leptin was higher in children with obesity and vitamin D deficiency than in children with obesity but no vitamin D deficiency.

Oxidative Stress and Gut Microbiome in Inflammatory Skin Diseases

Oxidative stress plays a dominant role in inflammatory skin diseases. Emerging evidence has shown that the close interaction occurred between oxidative stress and the gut microbiome. Overall, in this review, we have summarized the impact of oxidative stress and gut microbiome during the progression and treatment for inflammatory skin diseases, the interactions between gut dysbiosis and redox imbalance, and discussed the potential possible role of oxidative stress in the gut-skin axis. In addition, we have also elucidated the promising gut microbiome/redox-targeted therapeutic strategies for inflammatory skin diseases.

Protection of Quiescence and Longevity of IgG Memory B Cells by Mitochondrial Autophagy

The development of long-lived immune memory cells against pathogens is critical for the success of vaccines to establish protection against future infections. However, the mechanisms governing the long-term survival of immune memory cells remain to be elucidated. In this article, we show that the maintenance mitochondrial homeostasis by autophagy is critical for restricting metabolic functions to protect IgG memory B cell survival. Knockout of mitochondrial autophagy genes, Nix and Bnip3, leads to mitochondrial accumulation and increases in oxidative phosphorylation and fatty acid synthesis, resulting in the loss of IgG⁺ memory B cells in mice. Inhibiting fatty acid synthesis or silencing necroptosis gene Ripk3 rescued Nix^-/-Bnip3^-/- IgG memory B cells, indicating that mitochondrial autophagy is important for limiting metabolic functions to prevent cell death. Our results suggest a critical role for mitochondrial autophagy in the maintenance of immunological memory by protecting the metabolic quiescence and longevity of memory B cells.

Laurdan in live cell imaging: Effect of acquisition settings, cell culture conditions and data analysis on generalized polarization measurements

Cell function is highly dependent on membrane structure, organization, and fluidity. Therefore, methods to probe the biophysical properties of biological membranes are required. Determination of generalized polarization (GP) values using Laurdan in fluorescence microscopy studies is one of the most widely-used methods to investigate changes in membrane fluidity in vitro and in vivo. In the last couple of decades, there has been a major increase in the number of studies using Laurdan GP, where several different methodological approaches are used. Such differences interfere with data interpretation inasmuch as it is difficult to validate if Laurdan GP variations actually reflect changes in membrane organization or arise from biased experimental approaches. To address this, we evaluated the influence of different methodological details of experimental data acquisition and analysis on Laurdan GP. Our results showed that absolute GP values are highly dependent on several of the parameters analyzed, showing that incorrect data can result from technical and methodological inconsistencies. Considering these differences, we further analyzed the impact of cell variability on GP determination, focusing on basic cell culture conditions, such as cell confluency, number of passages and media composition. Our results show that GP values can report alterations in the biophysical properties of cell membranes caused by cellular adaptation to the culture conditions. In summary, this study provides thorough analysis of the factors that can lead to Laurdan GP variability and suggests approaches to improve data quality, which would generate more precise interpretation and comparison within individual studies and among the literature on Laurdan GP.

Acetylation-dependent SAGA complex dimerization promotes nucleosome acetylation and gene transcription

Cells reprogram their transcriptomes to adapt to external conditions. The SAGA (Spt-Ada-Gcn5 acetyltransferase) complex is a highly conserved transcriptional coactivator that plays essential roles in cell growth and development, in part by acetylating histones. Here, we uncover an autoregulatory mechanism of the Saccharomyces cerevisiae SAGA complex in response to environmental changes. Specifically, the SAGA complex acetylates its Ada3 subunit at three sites (lysines 8, 14 and 182) that are dynamically deacetylated by Rpd3. The acetylated Ada3 lysine residues are bound by bromodomains within SAGA subunits Gcn5 and Spt7 that synergistically facilitate formation of SAGA homo-dimers. Ada3-mediated dimerization is enhanced when cells are grown under sucrose or under phosphate-starvation conditions. Once dimerized, SAGA efficiently acetylates nucleosomes, promotes gene transcription and enhances cell resistance to stress. Collectively, our work reveals a mechanism for regulation of SAGA structure and activity and provides insights into how cells adapt to environmental conditions.

Biogenesis and Breakdown of Lipid Droplets in Pathological Conditions

Lipid droplets (LD) have long been considered as mere fat drops; however, LD have lately been revealed to be ubiquitous, dynamic and to be present in diverse organelles in which they have a wide range of key functions. Although incompletely understood, the biogenesis of eukaryotic LD initiates with the synthesis of neutral lipids (NL) by enzymes located in the endoplasmic reticulum (ER). The accumulation of NL leads to their segregation into nanometric nuclei which then grow into lenses between the ER leaflets as they are further filled with NL. The lipid composition and interfacial tensions of both ER and the lenses modulate their shape which, together with specific ER proteins, determine the proneness of LD to bud from the ER toward the cytoplasm. The most important function of LD is the buffering of energy. But far beyond this, LD are actively integrated into physiological processes, such as lipid metabolism, control of protein homeostasis, sequestration of toxic lipid metabolic intermediates, protection from stress, and proliferation of tumours. Besides, LD may serve as platforms for pathogen replication and defense. To accomplish these functions, from biogenesis to breakdown, eukaryotic LD have developed mechanisms to travel within the cytoplasm and to establish contact with other organelles. When nutrient deprivation occurs, LD undergo breakdown (lipolysis), which begins with the LD-associated members of the perilipins family PLIN2 and PLIN3 chaperone-mediated autophagy degradation (CMA), a specific type of autophagy that selectively degrades a subset of cytosolic proteins in lysosomes. Indeed, PLINs CMA degradation is a prerequisite for further true lipolysis, which occurs via cytosolic lipases or by lysosome luminal lipases when autophagosomes engulf portions of LD and target them to lysosomes. LD play a crucial role in several pathophysiological processes. Increased accumulation of LD in non-adipose cells is commonly observed in numerous infectious diseases caused by intracellular pathogens including viral, bacterial, and parasite infections, and is gradually recognized as a prominent characteristic in a variety of cancers. This review discusses current evidence related to the modulation of LD biogenesis and breakdown caused by intracellular pathogens and cancer.

Nutrient-responsive O-GlcNAcylation dynamically modulates the secretion of glycan-binding protein galectin 3

Endomembrane glycosylation and cytoplasmic O-GlcNAcylation each play essential roles in nutrient sensing, and characteristic changes in glycan patterns have been described in disease states such as diabetes and cancer. These changes in glycosylation have important functional roles and can drive disease progression. However, little is known about the molecular mechanisms underlying how these signals are integrated and transduced into biological effects. Galectins are proteins that bind glycans and that are secreted by a poorly characterized nonclassical secretory mechanism. Once outside the cell, galectins bind to the terminal galactose residues of cell surface glycans and modulate numerous extracellular functions, such as clathrin-independent endocytosis (CIE). Originating in the cytoplasm, galectins are predicted substrates for O-GlcNAc addition and removal; and as we have shown, galectin 3 is a substrate for O-GlcNAc transferase. In this study, we also show that galectin 3 secretion is sensitive to changes in O-GlcNAc levels. We determined using immunoprecipitation and Western blotting that there is a significant difference in O-GlcNAcylation status between cytoplasmic and secreted galectin 3. We observed dramatic alterations in galectin 3 secretion in response to nutrient conditions, which were dependent on dynamic O-GlcNAcylation. Importantly, we showed that these O-GlcNAc-driven alterations in galectin 3 secretion also facilitated changes in CIE. These results indicate that dynamic O-GlcNAcylation of galectin 3 plays a role in modulating its secretion and can tune its function in transducing nutrient-sensing information coded in cell surface glycosylation into biological effects.

Amino acid restriction induces a long non-coding RNA UBA6-AS1 to regulate GCN2-mediated integrated stress response in breast cancer

Oncogene activation, massive proliferation, and increased nutrient demands often result in nutrient and oxygen deprivation in solid tumors including breast cancer (BC), leading to the induction of oxidative stress and endoplasmic reticulum (ER) stress, and subsequently triggering integrated stress response (ISR). To elucidate the role of long non-coding RNAs (lncRNAs) in the ISR of BC, we performed transcriptome analyses and identified a lncRNA, UBA6-AS1, which was upregulated upon amino acid deprivation and ER stress. UBA6-AS1 was preferentially induced in triple-negative BC (TNBC) cells deprived of arginine or glutamine, two critical amino acids required for cancer cell growth, or treated with ER stress inducers. Mechanistically, UBA6-AS1 was regulated through the GCN2/eIF2α/ATF4 pathway, one of the major routes mediating ISR in amino acid sensing. In addition, both in vitro and in vivo assays indicated that UBA6-AS1 promoted TNBC cell survival when cells encountered metabolic stress, implicating a regulatory role of UBA6-AS1 in response to intratumoral metabolic stress during tumor progression. Moreover, PARP1 expression and activity were positively regulated by the GCN2/UBA6-AS1 axis upon amino acid deprivation. In conclusion, our data suggest that UBA6-AS1 is a novel lncRNA regulating ISR upon metabolic stress induction to promote TNBC cell survival. Furthermore, the GCN2-ATF4 axis is important for UBA6-AS1 induction to enhance PARP1 activity and could serve as a marker for the susceptibility of PARP inhibitors in TNBC.