bims-mepmim 2023-07-09 papers

bims-mepmim

Biomed News

on Metabolites in pathological microenvironments and immunometabolism

Issue of 2023–07–09
thirty papers selected by
Erika Mariana Palmieri, NIH/NCI Laboratory of Cancer ImmunoMetabolism

Pyruvate transamination and NAD biosynthesis enable proliferation of succinate dehydrogenase-deficient cells by supporting aerobic glycolysis.
Arf1 coordinates fatty acid metabolism and mitochondrial homeostasis.
Constitutively active autophagy in macrophages dampens inflammation through metabolic and post-transcriptional regulation of cytokine production.
SLC38A2 and glutamine signalling in cDC1s dictate anti-tumour immunity.
Ferroptosis in mitochondrial cardiomyopathy.
Cardiac lipid metabolism, mitochondrial function and heart failure.
Endothelial cell CD36 regulates membrane ceramide formation, exosome fatty acid transfer and circulating fatty acid levels.
Tissue-specific reprogramming of glutamine metabolism maintains tolerance to sepsis.
Accelerated Export of Dicer1 from Lipid-Challenged Hepatocytes Buffers Cellular miRNA-122 Levels and Prevents Cell Death.
ATF2 orchestrates macrophage differentiation and activation to promote antibacterial responses.
Proximity-labeling chemoproteomics defines the subcellular cysteinome and inflammation-responsive mitochondrial redoxome.
Vitamin B2 enables regulation of fasting glucose availability.
On demand utilization of phosphoribosyl pyrophosphate by downstream anabolic pathways.
Modeling and therapeutic targeting of inflammation-induced hepatic insulin resistance using human iPSC-derived hepatocytes and macrophages.
Detection of membrane-anchoring lipid modifications of proteins in cells by radioactive metabolic labeling.
Methyltransferase like 3 inhibition limits intrahepatic cholangiocarcinoma metabolic reprogramming and potentiates the efficacy of chemotherapy.
Targeting lipoxygenases to suppress ferroptotic cell death.
Immunometabolic coevolution defines unique microenvironmental niches in ccRCC.
Class 3 PI3K coactivates the circadian clock to promote rhythmic de novo purine synthesis.
Differential roles for ACBD4 and ACBD5 in peroxisome-ER interactions and lipid metabolism.
ACSL1 is a key regulator of inflammatory and macrophage foaming induced by short-term palmitate exposure or acute high-fat feeding.
FOXA2 controls the anti-oxidant response in FH-deficient cells.
Sample Preparation for Metabolite Detection in Mass Spectrometry Imaging.
Isolation of primary human liver cells from normal and nonalcoholic steatohepatitis livers.
m6A RNA modification regulates innate lymphoid cell responses in a lineage-specific manner.
Transitional dendritic cells are distinct from conventional DC2 precursors and mediate proinflammatory antiviral responses.
CDK4-E2F3 signals enhance oxidative skeletal muscle fiber numbers and function to affect myogenesis and metabolism.
Update DESI Mass Spectrometry Imaging (MSI).
Discovery of another mechanism for the inhibition of particulate guanylyl cyclases by the natriuretic peptide clearance receptor.
Endothelial tissue remodeling induced by intraluminal pressure enhances paracellular solute transport.

Cell Death Dis. 2023 Jul 06. 14(7): 403

Pyruvate transamination and NAD biosynthesis enable proliferation of succinate dehydrogenase-deficient cells by supporting aerobic glycolysis.

Luisa Ricci, Federico Uchenna Stanley, Tanja Eberhart, Francesco Mainini, David Sumpton, Simone Cardaci.

Succinate dehydrogenase (SDH) is the mitochondrial enzyme converting succinate to fumarate in the tricarboxylic acid (TCA) cycle. SDH acts as a tumor suppressor with germline loss-of-function mutations in its encoding genes predisposing to aggressive familial neuroendocrine and renal cancer syndromes. Lack of SDH activity disrupts the TCA cycle, imposes Warburg-like bioenergetic features, and commits cells to rely on pyruvate carboxylation for anabolic needs. However, the spectrum of metabolic adaptations enabling SDH-deficient tumors to cope with a dysfunctional TCA cycle remains largely unresolved. By using previously characterized Sdhb-deleted kidney mouse cells, here we found that SDH deficiency commits cells to rely on mitochondrial glutamate-pyruvate transaminase (GPT2) activity for proliferation. We showed that GPT2-dependent alanine biosynthesis is crucial to sustain reductive carboxylation of glutamine, thereby circumventing the TCA cycle truncation determined by SDH loss. By driving the reductive TCA cycle anaplerosis, GPT2 activity fuels a metabolic circuit maintaining a favorable intracellular NAD+ pool to enable glycolysis, thus meeting the energetic demands of SDH-deficient cells. As a metabolic syllogism, SDH deficiency confers sensitivity to NAD+ depletion achieved by pharmacological inhibition of nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme of the NAD+ salvage pathway. Beyond identifying an epistatic functional relationship between two metabolic genes in the control of SDH-deficient cell fitness, this study disclosed a metabolic strategy to increase the sensitivity of tumors to interventions limiting NAD availability.

DOI: https://doi.org/10.1038/s41419-023-05927-5
Nat Cell Biol. 2023 Jul 03.

Arf1 coordinates fatty acid metabolism and mitochondrial homeostasis.

Ludovic Enkler, Viktoria Szentgyörgyi, Mirjam Pennauer, Cristina Prescianotto-Baschong, Isabelle Riezman, Aneta Wiesyk, Reut Ester Avraham, Martin Spiess, Einat Zalckvar, Roza Kucharczyk, Howard Riezman, Anne Spang.

Lipid mobilization through fatty acid β-oxidation is a central process essential for energy production during nutrient shortage. In yeast, this catabolic process starts in the peroxisome from where β-oxidation products enter mitochondria and fuel the tricarboxylic acid cycle. Little is known about the physical and metabolic cooperation between these organelles. Here we found that expression of fatty acid transporters and of the rate-limiting enzyme involved in β-oxidation is decreased in cells expressing a hyperactive mutant of the small GTPase Arf1, leading to an accumulation of fatty acids in lipid droplets. Consequently, mitochondria became fragmented and ATP synthesis decreased. Genetic and pharmacological depletion of fatty acids phenocopied the arf1 mutant mitochondrial phenotype. Although β-oxidation occurs in both mitochondria and peroxisomes in mammals, Arf1's role in fatty acid metabolism is conserved. Together, our results indicate that Arf1 integrates metabolism into energy production by regulating fatty acid storage and utilization, and presumably organelle contact sites.

DOI: https://doi.org/10.1038/s41556-023-01180-2
Cell Rep. 2023 Jun 30. pii: S2211-1247(23)00719-2. [Epub ahead of print]42(7): 112708

Constitutively active autophagy in macrophages dampens inflammation through metabolic and post-transcriptional regulation of cytokine production.

Jinjin Xu, Lingjia Kong, Blayne A Oliver, Bihua Li, Elizabeth A Creasey, Gaelen Guzman, Monica Schenone, Kimberly L Carey, Steven A Carr, Daniel B Graham, Jacques Deguine, Ramnik J Xavier.

  Autophagy is an essential cellular process that is deeply integrated with innate immune signaling; however, studies that examine the impact of autophagic modulation in the context of inflammatory conditions are lacking. Here, using mice with a constitutively active variant of the autophagy gene Beclin1, we show that increased autophagy dampens cytokine production during a model of macrophage activation syndrome and in adherent-invasive Escherichia coli (AIEC) infection. Moreover, loss of functional autophagy through conditional deletion of Beclin1 in myeloid cells significantly enhances innate immunity in these contexts. We further analyzed primary macrophages from these animals with a combination of transcriptomics and proteomics to identify mechanistic targets downstream of autophagy. Our study reveals glutamine/glutathione metabolism and the RNF128/TBK1 axis as independent regulators of inflammation. Altogether, our work highlights increased autophagic flux as a potential approach to reduce inflammation and defines independent mechanistic cascades involved in this control.

Keywords:  CP: Immunology; RNF128; TBK1 signaling; autophagy; glutamine metabolism; glutathione metabolism; infection; inflammation; macrophages; proteogenomics

DOI:  https://doi.org/10.1016/j.celrep.2023.112708
Nature. 2023 Jul 05.

SLC38A2 and glutamine signalling in cDC1s dictate anti-tumour immunity.

Chuansheng Guo, Zhiyuan You, Hao Shi, Yu Sun, Xingrong Du, Gustavo Palacios, Cliff Guy, Sujing Yuan, Nicole M Chapman, Seon Ah Lim, Xiang Sun, Jordy Saravia, Sherri Rankin, Yogesh Dhungana, Hongbo Chi.

Cancer cells evade T cell-mediated killing through tumour-immune interactions whose mechanisms are not well understood1,2. Dendritic cells (DCs), especially type-1 conventional DCs (cDC1s), mediate T cell priming and therapeutic efficacy against tumours3. DC functions are orchestrated by pattern recognition receptors3-5, although other signals involved remain incompletely defined. Nutrients are emerging mediators of adaptive immunity6-8, but whether nutrients affect DC function or communication between innate and adaptive immune cells is largely unresolved. Here we establish glutamine as an intercellular metabolic checkpoint that dictates tumour-cDC1 crosstalk and licenses cDC1 function in activating cytotoxic T cells. Intratumoral glutamine supplementation inhibits tumour growth by augmenting cDC1-mediated CD8+ T cell immunity, and overcomes therapeutic resistance to checkpoint blockade and T cell-mediated immunotherapies. Mechanistically, tumour cells and cDC1s compete for glutamine uptake via the transporter SLC38A2 to tune anti-tumour immunity. Nutrient screening and integrative analyses show that glutamine is the dominant amino acid in promoting cDC1 function. Further, glutamine signalling via FLCN impinges on TFEB function. Loss of FLCN in DCs selectively impairs cDC1 function in vivo in a TFEB-dependent manner and phenocopies SLC38A2 deficiency by eliminating the anti-tumour therapeutic effect of glutamine supplementation. Our findings establish glutamine-mediated intercellular metabolic crosstalk between tumour cells and cDC1s that underpins tumour immune evasion, and reveal glutamine acquisition and signalling in cDC1s as limiting events for DC activation and putative targets for cancer treatment.

DOI: https://doi.org/10.1038/s41586-023-06299-8
Trends Cell Biol. 2023 Jul 05. pii: S0962-8924(23)00125-3. [Epub ahead of print]

Ferroptosis in mitochondrial cardiomyopathy.

Sofia Ahola, Thomas Langer.

  Ferroptosis is a form of necrotic cell death characterized by iron-dependent lipid peroxidation culminating in membrane rupture. Accumulating evidence links ferroptosis to multiple cardiac diseases and identifies mitochondria as important regulators of ferroptosis. Mitochondria are not only a major source of reactive oxygen species (ROS) but also counteract ferroptosis by preserving cellular redox balance and oxidative defense. Recent evidence has revealed that the mitochondrial integrated stress response limits oxidative stress and ferroptosis in oxidative phosphorylation (OXPHOS)-deficient cardiomyocytes and protects against mitochondrial cardiomyopathy. We summarize the multiple ways in which mitochondria modulate the susceptibility of cells to ferroptosis, and discuss the implications of ferroptosis for cardiomyopathies in mitochondrial disease.

Keywords:  Gpx4; ferroptosis; integrated stress response; mitochondrial cardiomyopathy

DOI:  https://doi.org/10.1016/j.tcb.2023.06.002
Cardiovasc Res. 2023 Jul 01. pii: cvad100. [Epub ahead of print]

Cardiac lipid metabolism, mitochondrial function and heart failure.

Lorenzo Da Dalt, Ainara G Cabodevilla, Ira J Goldberg, Giuseppe Danilo Norata.

  A fine balance between uptake, storage and the use of high energy fuels, like lipids, is crucial in the homeostasis of different metabolic tissues. Nowhere is this balance more important and more precarious than in the heart. This highly energy demanding muscle normally oxidizes almost all the available substrates to generate energy, with fatty acids being the preferred source under physiological conditions. In patients with cardiomyopathies and heart failure, changes in the main energetic substrate are observed; these hearts often prefer to utilize glucose rather than oxidizing fatty acids. An imbalance between uptake and oxidation of fatty acid can result in cellular lipid accumulation and cytotoxicity. In this review we will focus on the sources and uptake pathways used to direct fatty acids to cardiomyocytes. We will then discuss the intracellular machinery used to either store or oxidize these lipids and explain how disruptions in homeostasis can lead to mitochondrial dysfunction and heart failure. Moreover, we will also discuss the role of cholesterol accumulation in cardiomyocytes. Our discussion will attempt to weave in vitro experiments and in vivo data from mice and humans and use several human diseases to illustrate metabolism gone haywire as a cause of or accomplice to cardiac dysfunction.

Keywords:  Cholesterol and Heart failure; Lipids; Lipoprotein

DOI:  https://doi.org/10.1093/cvr/cvad100
Nat Commun. 2023 Jul 07. 14(1): 4029

Endothelial cell CD36 regulates membrane ceramide formation, exosome fatty acid transfer and circulating fatty acid levels.

V S Peche, T A Pietka, M Jacome-Sosa, D Samovski, H Palacios, G Chatterjee-Basu, A C Dudley, W Beatty, G A Meyer, I J Goldberg, N A Abumrad.

Endothelial cell (EC) CD36 controls tissue fatty acid (FA) uptake. Here we examine how ECs transfer FAs. FA interaction with apical membrane CD36 induces Src phosphorylation of caveolin-1 tyrosine-14 (Cav-1Y14) and ceramide generation in caveolae. Ensuing fission of caveolae yields vesicles containing FAs, CD36 and ceramide that are secreted basolaterally as small (80-100 nm) exosome-like extracellular vesicles (sEVs). We visualize in transwells EC transfer of FAs in sEVs to underlying myotubes. In mice with EC-expression of the exosome marker emeraldGFP-CD63, muscle fibers accumulate circulating FAs in emGFP-labeled puncta. The FA-sEV pathway is mapped through its suppression by CD36 depletion, blocking actin-remodeling, Src inhibition, Cav-1Y14 mutation, and neutral sphingomyelinase 2 inhibition. Suppression of sEV formation in mice reduces muscle FA uptake, raises circulating FAs, which remain in blood vessels, and lowers glucose, mimicking prominent Cd36-/- mice phenotypes. The findings show that FA uptake influences membrane ceramide, endocytosis, and EC communication with parenchymal cells.

DOI: https://doi.org/10.1038/s41467-023-39752-3
PLoS One. 2023 ;18(7): e0286525

Tissue-specific reprogramming of glutamine metabolism maintains tolerance to sepsis.

Brooks P Leitner, Won D Lee, Wanling Zhu, Xinyi Zhang, Rafael C Gaspar, Zongyu Li, Joshua D Rabinowitz, Rachel J Perry.

Reprogramming metabolism is of great therapeutic interest for reducing morbidity and mortality during sepsis-induced critical illness. Disappointing results from randomized controlled trials targeting glutamine and antioxidant metabolism in patients with sepsis have begged a deeper understanding of the tissue-specific metabolic response to sepsis. The current study sought to fill this gap. We analyzed skeletal muscle transcriptomics of critically ill patients, versus elective surgical controls, which revealed reduced expression of genes involved in mitochondrial metabolism and electron transport, with increases in glutathione cycling, glutamine, branched chain, and aromatic amino acid transport. We then performed untargeted metabolomics and 13C isotope tracing to analyze systemic and tissue specific metabolic phenotyping in a murine polymicrobial sepsis model. We found an increased number of correlations between the metabolomes of liver, kidney, and spleen, with loss of correlations between the heart and quadriceps and all other organs, pointing to a shared metabolic signature within vital abdominal organs, and unique metabolic signatures for muscles during sepsis. A lowered GSH:GSSG and elevated AMP:ATP ratio in the liver underlie the significant upregulation of isotopically labeled glutamine's contribution to TCA cycle anaplerosis and glutamine-derived glutathione biosynthesis; meanwhile, the skeletal muscle and spleen were the only organs where glutamine's contribution to the TCA cycle was significantly suppressed. These results highlight tissue-specific mitochondrial reprogramming to support liver energetic demands and antioxidant synthesis, rather than global mitochondrial dysfunction, as a metabolic consequence of sepsis.

DOI: https://doi.org/10.1371/journal.pone.0286525
J Biol Chem. 2023 Jun 30. pii: S0021-9258(23)02027-6. [Epub ahead of print] 104999

Accelerated Export of Dicer1 from Lipid-Challenged Hepatocytes Buffers Cellular miRNA-122 Levels and Prevents Cell Death.

Diptankar Bandyopadhyay, Sudarshana Basu, Ishita Mukherjee, Saikat Chakrabarti, Partha Chakrabarti, Kamalika Mukherjee, Suvendra N Bhattacharyya.

  Hepatocytes on exposure to high levels of lipids reorganize the metabolic program while fighting against the toxicity associated with elevated cellular lipids. The mechanism of this metabolic reorientation and stress management in lipid-challenged hepatocytes has not been well explored. We have noted the lowering of miR-122, a liver-specific miRNA, in the liver of mice fed with either a high-fat diet or a methionine choline-deficient diet that is associated with increased fat accumulation in mice liver. Interestingly, low miR-122 levels are attributed to the enhanced extracellular export of miRNA processor enzyme Dicer1 in mouse hepatocytes in the presence of high lipids. Export of Dicer1 can also account for the increased cellular levels of pre-miR-122- the substrate of Dicer1. Interestingly, restoration of Dicer1 levels in the mouse liver resulted in a strong inflammatory response and cell death in the presence of high lipids. Increasing death of hepatocytes was found to be caused by increased miR-122 levels in hepatocytes restored for Dicer1. Thus, the Dicer1 export by hepatocytes seems to be a key mechanism to combat lipotoxic stress by shunting out miR-122 from stressed hepatocytes. Finally, as part of this stress management, we determined that the Ago2-interacting pool of Dicer1, responsible for mature miRNP formation in mammalian cells, gets depleted. miRNA-binder and exporter protein HuR is found to accelerate Ago2-Dicer1 uncoupling to ensure export of Dicer1 via extracellular vesicles in lipid loaded hepatocytes.

Keywords:  Cell death; Dicer1; Extracellular Vesicles; Lipotoxic stress; miRNA

DOI:  https://doi.org/10.1016/j.jbc.2023.104999
J Leukoc Biol. 2023 Jul 04. pii: qiad076. [Epub ahead of print]

ATF2 orchestrates macrophage differentiation and activation to promote antibacterial responses.

Nusrah Rajabalee, Hannah Siushansian, Milani Weerapura, Stefania Berton, Fjolla Berbatovci, Breana Hooks, Michele Geoffrion, Dabo Yang, Mary-Ellen Harper, Katey Rayner, Alexandre Blais, Jim Sun.

  The differentiation and activation of macrophages are critical regulatory programs that are central to host inflammation and defense against pathogens. However, the transcriptional regulatory pathways involved in these programs are not well understood. Herein, we demonstrate that the activity and expression of Activating Transcription Factor 2 (ATF2) is precisely regulated during primary human monocyte to macrophage differentiation, and that its activation is linked to M1 polarization and antibacterial responses. Genetic perturbation experiments demonstrated that deletion of ATF2 (THP-ΔATF2) resulted in irregular and abnormal macrophage morphology, whereas macrophages overexpressing ATF2 (THP-ATF2) developed round and pancake-like morphology, resembling classically activated (M1) macrophages. Mechanistically, we show that ATF2 binds to the core promoter of PPM1A, a phosphatase that regulates monocyte-to-macrophage differentiation, to regulate its expression. Functionally, overexpression of ATF2 sensitized macrophages to M1 polarization, resulting in increased production of MHC Class II, IL-1β and IP-10, improved phagocytic capacity, and enhanced control of the intracellular pathogen Mycobacterium tuberculosis. Gene expression profiling revealed that overexpression of ATF2 reprogramed macrophages to promote antibacterial pathways enriched in chemokine signaling, metabolism and antigen presentation. Consistent with pathways analysis, metabolic profiling revealed that genetic overexpression or stimuli-induced activation of ATF2 alters the metabolic capacity of macrophages and primes these cells for glycolytic metabolism during M1 polarization or bacterial infection. Our findings reveal that ATF2 plays a central role during macrophage differentiation and M1 polarization to enhance the functional capacities of macrophages.

Keywords:   Mycobacterium tuberculosis ; ATF2; innate immunity; macrophage polarization; metabolic reprogramming; monocyte-to-macrophage differentiation; transcription factors

DOI:  https://doi.org/10.1093/jleuko/qiad076
Cell Chem Biol. 2023 Jun 22. pii: S2451-9456(23)00186-1. [Epub ahead of print]

Proximity-labeling chemoproteomics defines the subcellular cysteinome and inflammation-responsive mitochondrial redoxome.

Tianyang Yan, Ashley R Julio, Miranda Villanueva, Anthony E Jones, Andréa B Ball, Lisa M Boatner, Alexandra C Turmon, Kaitlyn B Nguyễn, Stephanie L Yen, Heta S Desai, Ajit S Divakaruni, Keriann M Backus.

  Proteinaceous cysteines function as essential sensors of cellular redox state. Consequently, defining the cysteine redoxome is a key challenge for functional proteomic studies. While proteome-wide inventories of cysteine oxidation state are readily achieved using established, widely adopted proteomic methods such as OxICAT, Biotin Switch, and SP3-Rox, these methods typically assay bulk proteomes and therefore fail to capture protein localization-dependent oxidative modifications. Here we establish the local cysteine capture (Cys-LoC) and local cysteine oxidation (Cys-LOx) methods, which together yield compartment-specific cysteine capture and quantitation of cysteine oxidation state. Benchmarking of the Cys-LoC method across a panel of subcellular compartments revealed more than 3,500 cysteines not previously captured by whole-cell proteomic analysis. Application of the Cys-LOx method to LPS-stimulated immortalized murine bone marrow-derived macrophages (iBMDM), revealed previously unidentified, mitochondrially localized cysteine oxidative modifications upon pro-inflammatory activation, including those associated with oxidative mitochondrial metabolism.

Keywords:  TurboID; chemoproteomics; cysteine; cysteine oxidation; lipopolysaccharide; macrophages; mitochondria; proximity labeling

DOI:  https://doi.org/10.1016/j.chembiol.2023.06.008
Elife. 2023 Jul 07. pii: e84077. [Epub ahead of print]12

Vitamin B2 enables regulation of fasting glucose availability.

Peter M Masschelin, Pradip Saha, Scott A Ochsner, Aaron R Cox, Kang Ho Kim, Jessica B Felix, Robert Sharp, Xin Li, Lin Tan, Jun Hyoung Park, Liping Wang, Vasanta Putluri, Philip L Lorenzi, Alli M Nuotio-Antar, Zheng Sun, Benny Abraham Kaipparettu, Nagireddy Putluri, David D Moore, Scott A Summers, Neil J McKenna, Sean M Hartig.

  Flavin adenine dinucleotide (FAD) interacts with flavoproteins to mediate oxidation-reduction reactions required for cellular energy demands. Not surprisingly, mutations that alter FAD binding to flavoproteins cause rare inborn errors of metabolism (IEMs) that disrupt liver function and render fasting intolerance, hepatic steatosis, and lipodystrophy. In our study, depleting FAD pools in mice with a vitamin B2-deficient diet (B2D) caused phenotypes associated with organic acidemias and other IEMs, including reduced body weight, hypoglycemia, and fatty liver disease. Integrated discovery approaches revealed B2D tempered fasting activation of target genes for the nuclear receptor PPARα, including those required for gluconeogenesis. We also found PPARα knockdown in the liver recapitulated B2D effects on glucose excursion and fatty liver disease in mice. Finally, treatment with the PPARα agonist fenofibrate activated the integrated stress response and refilled amino acid substrates to rescue fasting glucose availability and overcome B2D phenotypes. These findings identify metabolic responses to FAD availability and nominate strategies for the management of organic acidemias and other rare IEMs.

Keywords:  FAD; cell biology; gluconeogenesis; inborn errors of metabolism; metabolism; mouse; nuclear receptor

DOI:  https://doi.org/10.7554/eLife.84077
J Biol Chem. 2023 Jul 04. pii: S0021-9258(23)02039-2. [Epub ahead of print] 105011

On demand utilization of phosphoribosyl pyrophosphate by downstream anabolic pathways.

Benoît Pinson, Michel Moenner, Christelle Saint-Marc, Alexandra Granger-Farbos, Bertrand Daignan-Fornier.

  The pentose phosphate pathway (PPP) is critical for anabolism and biomass production. Here we show that the essential function of PPP in yeast is the synthesis of phosphoribosyl pyrophosphate (PRPP) catalyzed by PRPP-synthetase. Using combinations of yeast mutants, we found that a mildly decreased synthesis of PRPP affects biomass production, resulting in reduced cell size, while a more severe decrease ends up affecting yeast doubling time. We establish that it is PRPP itself that is limiting in invalid PRPP-synthetase mutants and that the resulting metabolic and growth defect can be bypassed by proper supplementation of the medium with ribose-containing precursors or by the expression of bacterial or human PRPP-synthetase. In addition, using documented pathologic human hyperactive forms of PRPP-synthetase, we show that intracellular PRPP as well as its derived products can be increased in both human and yeast cells and we describe the ensuing metabolic and physiological consequences. Finally, we found that PRPP consumption appears to take place "on demand" by the various PRPP-utilizing pathways, as shown by blocking or increasing the flux in specific PRPP-consuming metabolic routes. Overall, our work reveals important similarity between human and yeast for both synthesis and consumption of PRPP.

Keywords:  Pentose phosphate pathway; nucleotide biosynthesis; phosphoribosyl pyrophosphate; yeast

DOI:  https://doi.org/10.1016/j.jbc.2023.105011
Nat Commun. 2023 07 03. 14(1): 3902

Modeling and therapeutic targeting of inflammation-induced hepatic insulin resistance using human iPSC-derived hepatocytes and macrophages.

Marko Groeger, Koji Matsuo, Emad Heidary Arash, Ashley Pereira, Dounia Le Guillou, Cindy Pino, Kayque A Telles-Silva, Jacquelyn J Maher, Edward C Hsiao, Holger Willenbring.

Hepatic insulin resistance is recognized as a driver of type 2 diabetes and fatty liver disease but specific therapies are lacking. Here we explore the potential of human induced pluripotent stem cells (iPSCs) for modeling hepatic insulin resistance in vitro, with a focus on resolving the controversy about the impact of inflammation in the absence of steatosis. For this, we establish the complex insulin signaling cascade and the multiple inter-dependent functions constituting hepatic glucose metabolism in iPSC-derived hepatocytes (iPSC-Heps). Co-culture of these insulin-sensitive iPSC-Heps with isogenic iPSC-derived pro-inflammatory macrophages induces glucose output by preventing insulin from inhibiting gluconeogenesis and glycogenolysis and activating glycolysis. Screening identifies TNFα and IL1β as the mediators of insulin resistance in iPSC-Heps. Neutralizing these cytokines together restores insulin sensitivity in iPSC-Heps more effectively than individual inhibition, reflecting specific effects on insulin signaling and glucose metabolism mediated by NF-κB or JNK. These results show that inflammation is sufficient to induce hepatic insulin resistance and establish a human iPSC-based in vitro model to mechanistically dissect and therapeutically target this metabolic disease driver.

DOI: https://doi.org/10.1038/s41467-023-39311-w
STAR Protoc. 2023 Jul 04. pii: S2666-1667(23)00383-0. [Epub ahead of print]4(3): 102416

Detection of membrane-anchoring lipid modifications of proteins in cells by radioactive metabolic labeling.

Sameer Ahmed Bhat, Rachel Ferguson, Ritika Adhikari, Shafi Kuchay.

  Prenylation and palmitoylation are two major lipid modifications of cellular proteins that anchor proteins to cell membranes. Here, we present a protocol for detecting these modifications in cellular proteins by radioactive metabolic labeling. We describe steps for metabolic labeling of cells, cell harvesting for carrying out immunoprecipitations, subjecting immunocomplexes to SDS-PAGE, and transferring them to polyvinylidine flouride (PVDF) membranes. We then detail detection of labeled target proteins by exposing PVDF membranes to phosphor screens and using a phosphor imager machine. For complete details of this protocol, please refer to Liang et al.1.

Keywords:  Cell Membrane; Cell-based Assays; Protein Expression and Purification

DOI:  https://doi.org/10.1016/j.xpro.2023.102416
Oncogene. 2023 Jul 07.

Methyltransferase like 3 inhibition limits intrahepatic cholangiocarcinoma metabolic reprogramming and potentiates the efficacy of chemotherapy.

Jun Gao, Yuan Fang, Jiafeng Chen, Zheng Tang, Mengxin Tian, Xifei Jiang, Chenyang Tao, Run Huang, Guiqi Zhu, Weifeng Qu, Xiaoling Wu, Jian Zhou, Jia Fan, Weiren Liu, Yinghong Shi.

N6-methyladenosine (m6A) RNA methylation and its associated methyltransferase like 3 (METTL3) are involved in the development and maintenance of various tumors. The present study aimed to evaluate the cross-talk of METTL3 with glucose metabolism and reveal a novel mechanism for intrahepatic cholangiocarcinoma (ICC) progression. Real-time quantitative PCR, western blotting, and immunohistochemistry analyses suggested that METTL3 was highly expressed in ICC, which was correlated with poor patient prognosis. Immunoprecipitation sequencing of m6A-RNA showed that METTL3 upregulated m6A modification of NFAT5, which recruited IGF2BP1 for NFAT5 mRNA stabilization. Elevated expression of NFAT5 increased the expression of the gluconeogenesis-related genes GLUT1 and PGK1, resulting in enhanced aerobic glycolysis, proliferation, and tumor metastasis of ICC. Moreover, higher METTL3 expression was observed in tumor tissues of ICC patients with activated ICC glucose metabolism. Importantly, STM2457, a highly potent METTL3 inhibitor, which inhibited METTL3 activity and acted synergistically with gemcitabine, suggests that reprogramming RNA epigenetic modifications may serve as a potential therapeutic strategy. Overall, our findings highlighted the role of METTL3-mediated m6A modification of NFAT5 in activating glycolytic reprogramming in ICC and proposed that the METTL3/NFAT5 axis was a clinical target for the management of ICC chemoresistance by targeting cancer glycolysis.

DOI: https://doi.org/10.1038/s41388-023-02760-0
Proc Natl Acad Sci U S A. 2023 Jul 18. 120(29): e2309317120

Targeting lipoxygenases to suppress ferroptotic cell death.

Derek A Pratt.

DOI: https://doi.org/10.1073/pnas.2309317120
Cell Metab. 2023 Jun 28. pii: S1550-4131(23)00215-2. [Epub ahead of print]

Immunometabolic coevolution defines unique microenvironmental niches in ccRCC.

Cerise Tang, Amy X Xie, Eric Minwei Liu, Fengshen Kuo, Minsoo Kim, Renzo G DiNatale, Mahdi Golkaram, Ying-Bei Chen, Sounak Gupta, Robert J Motzer, Paul Russo, Jonathan Coleman, Maria I Carlo, Martin H Voss, Ritesh R Kotecha, Chung-Han Lee, Wesley Tansey, Nikolaus Schultz, A Ari Hakimi, Ed Reznik.

  Tumor cell phenotypes and anti-tumor immune responses are shaped by local metabolite availability, but intratumoral metabolite heterogeneity (IMH) and its phenotypic consequences remain poorly understood. To study IMH, we profiled tumor/normal regions from clear cell renal cell carcinoma (ccRCC) patients. A common pattern of IMH transcended all patients, characterized by correlated fluctuations in the abundance of metabolites and processes associated with ferroptosis. Analysis of intratumoral metabolite-RNA covariation revealed that the immune composition of the microenvironment, especially the abundance of myeloid cells, drove intratumoral metabolite variation. Motivated by the strength of RNA-metabolite covariation and the clinical significance of RNA biomarkers in ccRCC, we inferred metabolomic profiles from the RNA sequencing data of ccRCC patients enrolled in 7 clinical trials, and we ultimately identifyied metabolite biomarkers associated with response to anti-angiogenic agents. Local metabolic phenotypes, therefore, emerge in tandem with the immune microenvironment, influence ongoing tumor evolution, and are associated with therapeutic sensitivity.

Keywords:  cancer metabolism; immune microenvironment; immunometabolism; imputation; intratumoral heterogeneity; metabolites; metabolomics; renal cell carcinoma; transcriptomics

DOI:  https://doi.org/10.1016/j.cmet.2023.06.005
Nat Cell Biol. 2023 Jul 06.

Class 3 PI3K coactivates the circadian clock to promote rhythmic de novo purine synthesis.

Chantal Alkhoury, Nathaniel F Henneman, Volodymyr Petrenko, Yui Shibayama, Arianna Segaloni, Alexis Gadault, Ivan Nemazanyy, Edouard Le Guillou, Amare Desalegn Wolide, Konstantina Antoniadou, Xin Tong, Teruya Tamaru, Takeaki Ozawa, Muriel Girard, Karim Hnia, Dominik Lutter, Charna Dibner, Ganna Panasyuk.

Metabolic demands fluctuate rhythmically and rely on coordination between the circadian clock and nutrient-sensing signalling pathways, yet mechanisms of their interaction remain not fully understood. Surprisingly, we find that class 3 phosphatidylinositol-3-kinase (PI3K), known best for its essential role as a lipid kinase in endocytosis and lysosomal degradation by autophagy, has an overlooked nuclear function in gene transcription as a coactivator of the heterodimeric transcription factor and circadian driver Bmal1-Clock. Canonical pro-catabolic functions of class 3 PI3K in trafficking rely on the indispensable complex between the lipid kinase Vps34 and regulatory subunit Vps15. We demonstrate that although both subunits of class 3 PI3K interact with RNA polymerase II and co-localize with active transcription sites, exclusive loss of Vps15 in cells blunts the transcriptional activity of Bmal1-Clock. Thus, we establish non-redundancy between nuclear Vps34 and Vps15, reflected by the persistent nuclear pool of Vps15 in Vps34-depleted cells and the ability of Vps15 to coactivate Bmal1-Clock independently of its complex with Vps34. In physiology we find that Vps15 is required for metabolic rhythmicity in liver and, unexpectedly, it promotes pro-anabolic de novo purine nucleotide synthesis. We show that Vps15 activates the transcription of Ppat, a key enzyme for the production of inosine monophosphate, a central metabolic intermediate for purine synthesis. Finally, we demonstrate that in fasting, which represses clock transcriptional activity, Vps15 levels are decreased on the promoters of Bmal1 targets, Nr1d1 and Ppat. Our findings open avenues for establishing the complexity for nuclear class 3 PI3K signalling for temporal regulation of energy homeostasis.

DOI: https://doi.org/10.1038/s41556-023-01171-3
J Biol Chem. 2023 Jul 04. pii: S0021-9258(23)02041-0. [Epub ahead of print] 105013

Differential roles for ACBD4 and ACBD5 in peroxisome-ER interactions and lipid metabolism.

Joseph L Costello, Janet Koster, Beatriz S C Silva, Harley L Worthy, Tina A Schrader, Christian Hacker, Josiah Passmore, Frans A Kuypers, Hans R Waterham, Michael Schrader.

  Peroxisomes and the endoplasmic reticulum (ER) are intimately linked subcellular organelles, physically connected at membrane contact sites. As well as collaborating in lipid metabolism, e.g. of very long chain fatty acids (VLCFAs) and plasmalogens, the ER also plays a role in peroxisome biogenesis. Recent work has identified tethering complexes on the ER and peroxisome membranes which connect the organelles. These include membrane contacts formed via interactions between the ER protein VAPB (vesicle-associated membrane protein-associated protein B) and the peroxisomal proteins ACBD4 and ACBD5 (acyl-coenzyme A-binding domain protein). Loss of ACBD5 has been shown to cause a significant reduction in peroxisome-ER contacts and accumulation of VLCFAs. However, the role of ACBD4, and the relative contribution these two proteins make to contact site formation and recruitment of VLCFAs to peroxisomes remains unclear. Here, we address these questions, using a combination of molecular cell biology, biochemical and lipidomics analyses following loss of ACBD4 or ACBD5 in HEK293 cells. We show that the tethering function of ACBD5 is not absolutely required for efficient peroxisomal β-oxidation of VLCFAs. We demonstrate that loss of ACBD4 does not reduce peroxisome-ER connections or result in accumulation of VLCFAs. Instead, the loss of ACBD4 resulted in an increase in the rate of β-oxidation of VLCFAs. Finally, we observe interaction between ACBD5 and ACBD4, independent of VAPB binding. Overall, our findings suggest that ACBD5 may act as a primary tether and VLCFA recruitment factor, whereas ACBD4 may have regulatory functions in peroxisomal lipid metabolism at the peroxisome-ER interface.

Keywords:  ACBD4; ACBD5; ER; Peroxisomes; VAPB; fatty acid metabolism; membrane contact sites

DOI:  https://doi.org/10.1016/j.jbc.2023.105013
iScience. 2023 Jul 21. 26(7): 107145

ACSL1 is a key regulator of inflammatory and macrophage foaming induced by short-term palmitate exposure or acute high-fat feeding.

Fatema Al-Rashed, Dania Haddad, Ashraf Al Madhoun, Sardar Sindhu, Texy Jacob, Shihab Kochumon, Lina M Obeid, Fahd Al-Mulla, Yusuf A Hannun, Rasheed Ahmad.

  Foamy and inflammatory macrophages play pathogenic roles in metabolic disorders. However, the mechanisms that promote foamy and inflammatory macrophage phenotypes under acute-high-fat feeding (AHFF) remain elusive. Herein, we investigated the role of acyl-CoA synthetase-1 (ACSL1) in favoring the foamy/inflammatory phenotype of monocytes/macrophages upon short-term exposure to palmitate or AHFF. Palmitate exposure induced a foamy/inflammatory phenotype in macrophages which was associated with increased ACSL1 expression. Inhibition/knockdown of ACSL1 in macrophages suppressed the foamy/inflammatory phenotype through the inhibition of the CD36-FABP4-p38-PPARδ signaling axis. ACSL1 inhibition/knockdown suppressed macrophage foaming/inflammation after palmitate stimulation by downregulating the FABP4 expression. Similar results were obtained using primary human monocytes. As expected, oral administration of ACSL1 inhibitor triacsin-C in mice before AHFF normalized the inflammatory/foamy phenotype of the circulatory monocytes by suppressing FABP4 expression. Our results reveal that targeting ACSL1 leads to the attenuation of the CD36-FABP4-p38-PPARδ signaling axis, providing a therapeutic strategy to prevent the AHFF-induced macrophage foaming and inflammation.

Keywords:  Cellular physiology; Immunology; Physiology

DOI:  https://doi.org/10.1016/j.isci.2023.107145
Cell Rep. 2023 Jul 04. pii: S2211-1247(23)00762-3. [Epub ahead of print]42(7): 112751

FOXA2 controls the anti-oxidant response in FH-deficient cells.

Connor Rogerson, Marco Sciacovelli, Lucas A Maddalena, Andromachi Pouikli, Marc Segarra-Mondejar, Lorea Valcarcel-Jimenez, Christina Schmidt, Ming Yang, Elena Ivanova, Joshua Kent, Ariane Mora, Danya Cheeseman, Jason S Carroll, Gavin Kelsey, Christian Frezza.

  Hereditary leiomyomatosis and renal cell cancer (HLRCC) is a cancer syndrome caused by inactivating germline mutations in fumarate hydratase (FH) and subsequent accumulation of fumarate. Fumarate accumulation leads to profound epigenetic changes and the activation of an anti-oxidant response via nuclear translocation of the transcription factor NRF2. The extent to which chromatin remodeling shapes this anti-oxidant response is currently unknown. Here, we explored the effects of FH loss on the chromatin landscape to identify transcription factor networks involved in the remodeled chromatin landscape of FH-deficient cells. We identify FOXA2 as a key transcription factor that regulates anti-oxidant response genes and subsequent metabolic rewiring cooperating without direct interaction with the anti-oxidant regulator NRF2. The identification of FOXA2 as an anti-oxidant regulator provides additional insights into the molecular mechanisms behind cell responses to fumarate accumulation and potentially provides further avenues for therapeutic intervention for HLRCC.

Keywords:  CP: Cancer; CP: Molecular biology; FOXA2; NRF2; anti-oxidant response; fumarate hydratase

DOI:  https://doi.org/10.1016/j.celrep.2023.112751
Methods Mol Biol. 2023 ;2688 135-146

Sample Preparation for Metabolite Detection in Mass Spectrometry Imaging.

Maria K Andersen, Marco Giampà, Elise Midtbust, Therese S Høiem, Sebastian Krossa, May-Britt Tessem.

  Metabolites reflect the biological state of cells and tissue, and metabolomics is therefore a field of high interest both to understand normal physiological functions and disease development. When studying heterogeneous tissue samples, mass spectrometry imaging (MSI) is a valuable tool as it conserves the spatial distribution of analytes on tissue sections. A large proportion of metabolites are, however, small and polar, making them vulnerable to delocalizing through diffusion during sample preparation. Here we present a sample preparation method optimized to limit diffusion and delocalization of small polar metabolites in fresh frozen tissue sections. This sample preparation protocol includes cryosectioning, vacuum frozen storage, and matrix application. The methods described were primely developed for matrix-assisted laser desorption/ionization (MALDI) MSI, but the protocol describing cryosectioning and vacuum freezing storage can also be applied before desorption electrospray ionization (DESI) MSI. Our vacuum drying and vacuum packing approach offers a particular advantage to limit delocalization and safe storage.

Keywords:  Analyte localization; Cryosectioning; Fresh frozen tissue; Mass spectrometry imaging; Matrix application; Small metabolites

DOI:  https://doi.org/10.1007/978-1-0716-3319-9_12
STAR Protoc. 2023 Jul 04. pii: S2666-1667(23)00358-1. [Epub ahead of print]4(3): 102391

Isolation of primary human liver cells from normal and nonalcoholic steatohepatitis livers.

Xiao Liu, Kevin Lam, Huayi Zhao, Sadatsugu Sakane, Hyun Young Kim, Alvaro Eguileor, Karin Diggle, Shuai Wu, Raquel Carvalho Gontijo Weber, Pejman Soroosh, Mojgan Hosseini, Kristin Mekeel, David A Brenner, Tatiana Kisseleva.

  Here, we present a protocol for isolating human hepatocytes and neural progenitor cells from normal and nonalcoholic steatohepatitis livers. We describe steps for perfusion for scaled-up liver cell isolation and optimization of chemical digestion to achieve maximal yield and cell viability. We then detail a liver cell cryopreservation and potential applications, such as the use of human liver cells as a tool to link experimental and translational research.

Keywords:  Cell Biology; Health Sciences

DOI:  https://doi.org/10.1016/j.xpro.2023.102391
Nat Immunol. 2023 Jul 03.

m6A RNA modification regulates innate lymphoid cell responses in a lineage-specific manner.

Yingyu Zhang, Wanwei Zhang, Jingyao Zhao, Takamasa Ito, Jiacheng Jin, Alexis O Aparicio, Junsong Zhou, Vincent Guichard, Yinshan Fang, Jianwen Que, Joseph F Urban, Jacob H Hanna, Sankar Ghosh, Xuebing Wu, Lei Ding, Uttiya Basu, Yuefeng Huang.

Innate lymphoid cells (ILCs) can quickly switch from a quiescent state to an active state and rapidly produce effector molecules that provide critical early immune protection. How the post-transcriptional machinery processes different stimuli and initiates robust gene expression in ILCs is poorly understood. Here, we show that deletion of the N6-methyladenosine (m6A) writer protein METTL3 has little impact on ILC homeostasis or cytokine-induced ILC1 or ILC3 responses but significantly diminishes ILC2 proliferation, migration and effector cytokine production and results in impaired antihelminth immunity. m6A RNA modification supports an increase in cell size and transcriptional activity in activated ILC2s but not in ILC1s or ILC3s. Among other transcripts, the gene encoding the transcription factor GATA3 is highly m6A methylated in ILC2s. Targeted m6A demethylation destabilizes nascent Gata3 mRNA and abolishes the upregulation of GATA3 and ILC2 activation. Our study suggests a lineage-specific requirement of m6A for ILC2 responses.

DOI: https://doi.org/10.1038/s41590-023-01548-4
Nat Immunol. 2023 Jul 06.

Transitional dendritic cells are distinct from conventional DC2 precursors and mediate proinflammatory antiviral responses.

Fernando Bandeira Sulczewski, Raul A Maqueda-Alfaro, Marcela Alcántara-Hernández, Oriana A Perez, Sanjana Saravanan, Tae Jin Yun, David Seong, Rebeca Arroyo Hornero, Hayley M Raquer-McKay, Eduardo Esteva, Zachary R Lanzar, Rebecca A Leylek, Nicholas M Adams, Annesa Das, Adeeb H Rahman, Andres Gottfried-Blackmore, Boris Reizis, Juliana Idoyaga.

High-dimensional approaches have revealed heterogeneity amongst dendritic cells (DCs), including a population of transitional DCs (tDCs) in mice and humans. However, the origin and relationship of tDCs to other DC subsets has been unclear. Here we show that tDCs are distinct from other well-characterized DCs and conventional DC precursors (pre-cDCs). We demonstrate that tDCs originate from bone marrow progenitors shared with plasmacytoid DCs (pDCs). In the periphery, tDCs contribute to the pool of ESAM+ type 2 DCs (DC2s), and these DC2s have pDC-related developmental features. Different from pre-cDCs, tDCs have less turnover, capture antigen, respond to stimuli and activate antigen-specific naïve T cells, all characteristics of differentiated DCs. Different from pDCs, viral sensing by tDCs results in IL-1β secretion and fatal immune pathology in a murine coronavirus model. Our findings suggest that tDCs are a distinct pDC-related subset with a DC2 differentiation potential and unique proinflammatory function during viral infections.

DOI: https://doi.org/10.1038/s41590-023-01545-7
J Clin Invest. 2023 07 03. pii: e162479. [Epub ahead of print]133(13):

CDK4-E2F3 signals enhance oxidative skeletal muscle fiber numbers and function to affect myogenesis and metabolism.

Young Jae Bahn, Hariom Yadav, Paolo Piaggi, Brent S Abel, Oksana Gavrilova, Danielle A Springer, Ioannis Papazoglou, Patricia M Zerfas, Monica C Skarulis, Alexandra C McPherron, Sushil G Rane.

  Understanding how skeletal muscle fiber proportions are regulated is vital to understanding muscle function. Oxidative and glycolytic skeletal muscle fibers differ in their contractile ability, mitochondrial activity, and metabolic properties. Fiber-type proportions vary in normal physiology and disease states, although the underlying mechanisms are unclear. In human skeletal muscle, we observed that markers of oxidative fibers and mitochondria correlated positively with expression levels of PPARGC1A and CDK4 and negatively with expression levels of CDKN2A, a locus significantly associated with type 2 diabetes. Mice expressing a constitutively active Cdk4 that cannot bind its inhibitor p16INK4a, a product of the CDKN2A locus, were protected from obesity and diabetes. Their muscles exhibited increased oxidative fibers, improved mitochondrial properties, and enhanced glucose uptake. In contrast, loss of Cdk4 or skeletal muscle-specific deletion of Cdk4's target, E2F3, depleted oxidative myofibers, deteriorated mitochondrial function, and reduced exercise capacity, while increasing diabetes susceptibility. E2F3 activated the mitochondrial sensor PPARGC1A in a Cdk4-dependent manner. CDK4, E2F3, and PPARGC1A levels correlated positively with exercise and fitness and negatively with adiposity, insulin resistance, and lipid accumulation in human and rodent muscle. All together, these findings provide mechanistic insight into regulation of skeletal muscle fiber-specification that is of relevance to metabolic and muscular diseases.

Keywords:  Metabolism; Mitochondria; Muscle Biology; Skeletal muscle

DOI:  https://doi.org/10.1172/JCI162479
Methods Mol Biol. 2023 ;2688 41-54

Update DESI Mass Spectrometry Imaging (MSI).

Emmanuelle Claude, Mark Towers, Emrys Jones.

  Desorption electrospray ionization (DESI) is an ambient technique that allows chemical information to be obtained directly from a wide range of surfaces, without pretreatment. Here we describe the improvements that have been developed to be able to achieve low tens of microns pixel size MSI experiments with high sensitivity for metabolites and lipids from biological tissue sections.In the last decade, DESI mass spectrometry has undergone developmental improvements, with regard to the method of desorption and ionization as well as the mass spectrometer to which the DESI source has been coupled to. DESI is becoming a mass spectrometry imaging technique, which can match and complement the currently most widely adopted ionization technique, the matrix-assisted laser desorption/ionization (MALDI).

Keywords:  Ambient; Co-registration; DESI; Heated transfer line; High definition imaging

DOI:  https://doi.org/10.1007/978-1-0716-3319-9_4
Proc Natl Acad Sci U S A. 2023 07 11. 120(28): e2307882120

Discovery of another mechanism for the inhibition of particulate guanylyl cyclases by the natriuretic peptide clearance receptor.

Dianxin Liu, Ryan P Ceddia, Wei Zhang, Fubiao Shi, Huafeng Fang, Sheila Collins.

  The cardiac natriuretic peptides (NPs) control pivotal physiological actions such as fluid and electrolyte balance, cardiovascular homeostasis, and adipose tissue metabolism by activating their receptor enzymes [natriuretic peptide receptor-A (NPRA) and natriuretic peptide receptor-B (NPRB)]. These receptors are homodimers that generate intracellular cyclic guanosine monophosphate (cGMP). The natriuretic peptide receptor-C (NPRC), nicknamed the clearance receptor, lacks a guanylyl cyclase domain; instead, it can bind the NPs to internalize and degrade them. The conventional paradigm is that by competing for and internalizing NPs, NPRC blunts the ability of NPs to signal through NPRA and NPRB. Here we show another previously unknown mechanism by which NPRC can interfere with the cGMP signaling function of the NP receptors. By forming a heterodimer with monomeric NPRA or NPRB, NPRC can prevent the formation of a functional guanylyl cyclase domain and thereby suppress cGMP production in a cell-autonomous manner.

Keywords:  NPRA; NPRB; NPRC; natriuretic peptide; receptors

DOI:  https://doi.org/10.1073/pnas.2307882120
iScience. 2023 Jul 21. 26(7): 107141

Endothelial tissue remodeling induced by intraluminal pressure enhances paracellular solute transport.

Jean Cacheux, Aurélien Bancaud, Daniel Alcaide, Jun-Ichi Suehiro, Yoshihiro Akimoto, Hiroyuki Sakurai, Yukiko T Matsunaga.

  The endothelial layers of the microvasculature regulate the transport of solutes to the surrounding tissues. It remains unclear how this barrier function is affected by blood flow-induced intraluminal pressure. Using a 3D microvessel model, we compare the transport of macromolecules through endothelial tissues at mechanical rest or with intraluminal pressure, and correlate these data with electron microscopy of endothelial junctions. On application of an intraluminal pressure of 100 Pa, we demonstrate that the flow through the tissue increases by 2.35 times. This increase is associated with a 25% expansion of microvessel diameter, which leads to tissue remodeling and thinning of the paracellular junctions. We recapitulate these data with the deformable monopore model, in which the increase in paracellular transport is explained by the augmentation of the diffusion rate across thinned junctions under mechanical stress. We therefore suggest that the deformation of microvasculatures contributes to regulate their barrier function.

Keywords:  Bioengineering; Biomechanics; Cell biology; Computer modeling; Tissue engineering

DOI:  https://doi.org/10.1016/j.isci.2023.107141