bims-celmim 2024-01-07 papers

bims-celmim

Biomed News

on Cellular and mitochondrial metabolism

Issue of 2024–01–07
29 papers selected by
Marc Segarra Mondejar, University of Cologne

Metabolic switch regulates lineage plasticity and induces synthetic lethality in triple-negative breast cancer.
Mitochondrial-derived vesicles in metabolism, disease, and aging.
Mitochondrial Dynamics at Different Levels: From Cristae Dynamics to Interorganellar Cross Talk.
Over-expression of N-acetylaspartate synthase exacerbates pathological energetic deficit and accelerates cognitive decline in the 5xFAD mouse.
Acylspermidines are conserved mitochondrial sirtuin-dependent metabolites.
Structural insights into respiratory complex I deficiency and assembly from the mitochondrial disease-related ndufs4-/- mouse.
Mitochondrial lipid dynamics regulated by MITOL-mediated ubiquitination.
Fission-independent compartmentalization of mitochondria during budding yeast cell division.
The solute carrier SLC25A17 sustains peroxisomal redox homeostasis in diverse mammalian cell lines.
Alterations in mitochondria isolated from peripheral blood mononuclear cells and tumors of patients with epithelial ovarian cancers.
Mitochondrial Esterase Activity Measured at the Single Organelle Level by Nano-flow Cytometry.
HKDC1, a target of TFEB, is essential to maintain both mitochondrial and lysosomal homeostasis, preventing cellular senescence.
Characterization of genetic and molecular tools for studying the endogenous expression of Lactate dehydrogenase in Drosophila melanogaster.
Nanotechnology Reprogramming Metabolism for Enhanced Tumor Immunotherapy.
Dual regulation of SLC25A39 by AFG3L2 and iron controls mitochondrial glutathione homeostasis.
Basic pathway decomposition of biochemical reaction networks within growing cells.
Metabolic reprogramming by histone deacetylase inhibition preferentially targets NRF2-activated tumors.
Fatty acid synthesis suppresses dietary polyunsaturated fatty acid use.
Glycine homeostasis requires reverse SHMT flux.
Glutamine addiction in tumor cell: oncogene regulation and clinical treatment.
p32 regulates glycometabolism and TCA cycle to inhibit ccRCC progression via copper-induced DLAT lipoylation oligomerization.
An interactive web application for exploring human plasma and fibroblast metabolomics data from patients with inborn errors of metabolism.
MTCH2 cooperates with MFN2 and lysophosphatidic acid synthesis to sustain mitochondrial fusion.
A single mitochondria-targetable fluorescent probe for visualizing cysteine and glutathione in ferroptosis of myocardial ischemia/reperfusion injury.
Serum metabolic signatures for Alzheimer's Disease reveal alterations in amino acid composition: a validation study.
VAP spatially stabilizes dendritic mitochondria to locally support synaptic plasticity.
A new physiological medium uncovers biochemical and cellular alterations in Lesch-Nyhan disease fibroblasts.
Two-pore channel-2 and inositol trisphosphate receptors coordinate Ca2+ signals between lysosomes and the endoplasmic reticulum.
Lysosomal TBK1 Responds to Amino Acid Availability to Relieve Rab7-Dependent mTORC1 Inhibition.

Cell Metab. 2024 Jan 02. pii: S1550-4131(23)00455-2. [Epub ahead of print]36(1): 193-208.e8

Metabolic switch regulates lineage plasticity and induces synthetic lethality in triple-negative breast cancer.

Yingsheng Zhang, Meng-Ju Wu, Wan-Chi Lu, Yi-Chuan Li, Chun Ju Chang, Jer-Yen Yang.

  Metabolic reprogramming is key for cancer development, yet the mechanism that sustains triple-negative breast cancer (TNBC) cell growth despite deficient pyruvate kinase M2 (PKM2) and tumor glycolysis remains to be determined. Here, we find that deficiency in tumor glycolysis activates a metabolic switch from glycolysis to fatty acid β-oxidation (FAO) to fuel TNBC growth. We show that, in TNBC cells, PKM2 directly interacts with histone methyltransferase EZH2 to coordinately mediate epigenetic silencing of a carnitine transporter, SLC16A9. Inhibition of PKM2 leads to impaired EZH2 recruitment to SLC16A9, and in turn de-represses SLC16A9 expression to increase intracellular carnitine influx, programming TNBC cells to an FAO-dependent and luminal-like cell state. Together, these findings reveal a new metabolic switch that drives TNBC from a metabolically heterogeneous-lineage plastic cell state to an FAO-dependent-lineage committed cell state, where dual targeting of EZH2 and FAO induces potent synthetic lethality in TNBC.

Keywords:  EZH2; PKM2; SLC16A9; induced synthetic lethality; lineage plasticity; metabolic reprogramming

DOI:  https://doi.org/10.1016/j.cmet.2023.12.003
Cell Metab. 2024 Jan 02. pii: S1550-4131(23)00446-1. [Epub ahead of print]36(1): 21-35

Mitochondrial-derived vesicles in metabolism, disease, and aging.

Tim König, Heidi M McBride.

Mitochondria are central hubs of cellular metabolism and are tightly connected to signaling pathways. The dynamic plasticity of mitochondria to fuse, divide, and contact other organelles to flux metabolites is central to their function. To ensure bona fide functionality and signaling interconnectivity, diverse molecular mechanisms evolved. An ancient and long-overlooked mechanism is the generation of mitochondrial-derived vesicles (MDVs) that shuttle selected mitochondrial cargoes to target organelles. Just recently, we gained significant insight into the mechanisms and functions of MDV transport, ranging from their role in mitochondrial quality control to immune signaling, thus demonstrating unexpected and diverse physiological aspects of MDV transport. This review highlights the origin of MDVs, their biogenesis, and their cargo selection, with a specific focus on the contribution of MDV transport to signaling across cell and organ barriers. Additionally, the implications of MDVs in peroxisome biogenesis, neurodegeneration, metabolism, aging, and cancer are discussed.

DOI: https://doi.org/10.1016/j.cmet.2023.11.014
Annu Rev Biophys. 2024 Jan 02.

Mitochondrial Dynamics at Different Levels: From Cristae Dynamics to Interorganellar Cross Talk.

Arun Kumar Kondadi, Andreas S Reichert.

Mitochondria are essential organelles performing important cellular functions ranging from bioenergetics and metabolism to apoptotic signaling and immune responses. They are highly dynamic at different structural and functional levels. Mitochondria have been shown to constantly undergo fusion and fission processes and dynamically interact with other organelles such as the endoplasmic reticulum, peroxisomes, and lipid droplets. The field of mitochondrial dynamics has evolved hand in hand with technological achievements including advanced fluorescence super-resolution nanoscopy. Dynamic remodeling of the cristae membrane within individual mitochondria, discovered very recently, opens up a further exciting layer of mitochondrial dynamics. In this review, we discuss mitochondrial dynamics at the following levels: (a) within an individual mitochondrion, (b) among mitochondria, and (c) between mitochondria and other organelles. Although the three tiers of mitochondrial dynamics have in the past been classified in a hierarchical manner, they are functionally connected and must act in a coordinated manner to maintain cellular functions and thus prevent various human diseases. Expected final online publication date for the Annual Review of Biophysics, Volume 53 is May 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

DOI: https://doi.org/10.1146/annurev-biophys-030822-020736
J Neurochem. 2024 Jan 05.

Over-expression of N-acetylaspartate synthase exacerbates pathological energetic deficit and accelerates cognitive decline in the 5xFAD mouse.

Jeremy S Francis, Quy Nguyen, Vladimir Markov, Paola Leone.

  N-acetylaspartate (NAA) is an abundant central nervous system amino acid derivative that is tightly coupled to mitochondria and energy metabolism in neurons. A reduced NAA signature is a prominent early pathological biomarker in multiple neurodegenerative diseases and becomes progressively more pronounced as disease advances. Because NAA synthesis requires aspartate drawn directly from mitochondria, we argued that this process is in direct competition with oxidative phosphorylation for substrate and that sustained high levels of NAA synthesis would be incompatible with pathological energy crisis. We show here that over-expression of the rate-limiting NAA synthetic enzyme in the hippocampus of the 5x familial Alzheimer's disease (5xFAD) mouse results in an exaggerated pathological ATP deficit and accelerated cognitive decline. Over-expression of NAA synthase did not increase amyloid burden or result in cell loss but did significantly deplete mitochondrial aspartate and impair the ability of mitochondria to oxidize glutamate for adenosine triphosphate (ATP) synthesis. These results define NAA as a sink for energetic substrate and suggest initial pathological reductions in NAA are part of a response to energetic crisis designed to preserve substrate bioavailability for mitochondrial ATP synthesis.

Keywords:  N-acetylaspartate; Neurodegenerative disease; metabolic decline

DOI:  https://doi.org/10.1111/jnc.16044
Nat Chem Biol. 2024 Jan 02.

Acylspermidines are conserved mitochondrial sirtuin-dependent metabolites.

Bingsen Zhang, James Mullmann, Andreas H Ludewig, Irma R Fernandez, Tyler R Bales, Robert S Weiss, Frank C Schroeder.

Sirtuins are nicotinamide adenine dinucleotide (NAD+)-dependent protein lysine deacylases regulating metabolism and stress responses; however, characterization of the removed acyl groups and their downstream metabolic fates remains incomplete. Here we employed untargeted comparative metabolomics to reinvestigate mitochondrial sirtuin biochemistry. First, we identified N-glutarylspermidines as metabolites downstream of the mitochondrial sirtuin SIR-2.3 in Caenorhabditis elegans and demonstrated that SIR-2.3 functions as a lysine deglutarylase and that N-glutarylspermidines can be derived from O-glutaryl-ADP-ribose. Subsequent targeted analysis of C. elegans, mouse and human metabolomes revealed a chemically diverse range of N-acylspermidines, and formation of N-succinylspermidines and/or N-glutarylspermidines was observed downstream of mammalian mitochondrial sirtuin SIRT5 in two cell lines, consistent with annotated functions of SIRT5. Finally, N-glutarylspermidines were found to adversely affect C. elegans lifespan and mammalian cell proliferation. Our results indicate that N-acylspermidines are conserved metabolites downstream of mitochondrial sirtuins that facilitate annotation of sirtuin enzymatic activities in vivo and may contribute to sirtuin-dependent phenotypes.

DOI: https://doi.org/10.1038/s41589-023-01511-2
EMBO J. 2024 Jan 02.

Structural insights into respiratory complex I deficiency and assembly from the mitochondrial disease-related ndufs4-/- mouse.

Zhan Yin, Ahmed-Noor A Agip, Hannah R Bridges, Judy Hirst.

  Respiratory complex I (NADH:ubiquinone oxidoreductase) is essential for cellular energy production and NAD+ homeostasis. Complex I mutations cause neuromuscular, mitochondrial diseases, such as Leigh Syndrome, but their molecular-level consequences remain poorly understood. Here, we use a popular complex I-linked mitochondrial disease model, the ndufs4-/- mouse, to define the structural, biochemical, and functional consequences of the absence of subunit NDUFS4. Cryo-EM analyses of the complex I from ndufs4-/- mouse hearts revealed a loose association of the NADH-dehydrogenase module, and discrete classes containing either assembly factor NDUFAF2 or subunit NDUFS6. Subunit NDUFA12, which replaces its paralogue NDUFAF2 in mature complex I, is absent from all classes, compounding the deletion of NDUFS4 and preventing maturation of an NDUFS4-free enzyme. We propose that NDUFAF2 recruits the NADH-dehydrogenase module during assembly of the complex. Taken together, the findings provide new molecular-level understanding of the ndufs4-/- mouse model and complex I-linked mitochondrial disease.

Keywords:  Complex I; Cryo-EM; Leigh Syndrome; Mitochondria; NADH:Ubiquinone Oxidoreductase

DOI:  https://doi.org/10.1038/s44318-023-00001-4
J Biochem. 2023 Dec 29. pii: mvad117. [Epub ahead of print]

Mitochondrial lipid dynamics regulated by MITOL-mediated ubiquitination.

Koji Yamano, Hiroki Kinefuchi, Waka Kojima.

  Mitochondria-endoplasmic reticulum (ER) contact sites in mammals provide platforms for various reactions such as calcium signaling, lipid metabolism, organelle dynamics and autophagy. To fulfill these tasks, a number of proteins assemble at the contact sites including MITOL/MARCHF5, a critical mitochondrial ubiquitin ligase. How MITOL regulates mitochondrial function from the contact site, however, has been largely unresolved. Recently, a new role for MITOL in the active transport of phosphatidic acid from the ER to mitochondria was reported. In this commentary, we briefly summarize our current understanding of mitochondria-ER contact sites and discuss the recently elucidated mechanism of MITOL fine-tuning phospholipid transfer activity through ubiquitination.

Keywords:  contact site; mitochondria; phospholipid; ubiquitin; ubiquitin ligase

DOI:  https://doi.org/10.1093/jb/mvad117
J Cell Biol. 2024 Mar 04. pii: e202211048. [Epub ahead of print]223(3):

Fission-independent compartmentalization of mitochondria during budding yeast cell division.

Saori R Yoshii, Yves Barral.

Lateral diffusion barriers compartmentalize membranes to generate polarity or asymmetrically partition membrane-associated macromolecules. Budding yeasts assemble such barriers in the endoplasmic reticulum (ER) and the outer nuclear envelope at the bud neck to retain aging factors in the mother cell and generate naïve and rejuvenated daughter cells. However, little is known about whether other organelles are similarly compartmentalized. Here, we show that the membranes of mitochondria are laterally compartmentalized at the bud neck and near the cell poles. The barriers in the inner mitochondrial membrane are constitutive, whereas those in the outer membrane form in response to stresses. The strength of mitochondrial diffusion barriers is regulated positively by spatial cues from the septin axis and negatively by retrograde (RTG) signaling. These data indicate that mitochondria are compartmentalized in a fission-independent manner. We propose that these diffusion barriers promote mitochondrial polarity and contribute to mitochondrial quality control.

DOI: https://doi.org/10.1083/jcb.202211048
Free Radic Biol Med. 2023 Dec 29. pii: S0891-5849(23)01191-7. [Epub ahead of print]212 241-254

The solute carrier SLC25A17 sustains peroxisomal redox homeostasis in diverse mammalian cell lines.

Cláudio F Costa, Celien Lismont, Serhii Chornyi, Janet Koster, Hongli Li, Mohamed A F Hussein, Paul P Van Veldhoven, Hans R Waterham, Marc Fransen.

  Despite the crucial role of peroxisomes in cellular redox maintenance, little is known about how these organelles transport redox metabolites across their membrane. In this study, we sought to assess potential associations between the cellular redox landscape and the human peroxisomal solute carrier SLC25A17, also known as PMP34. This carrier has been reported to function as a counter-exchanger of adenine-containing cofactors such as coenzyme A (CoA), dephospho-CoA, flavin adenine dinucleotide, nicotinamide adenine dinucleotide (NAD+), adenosine 3',5'-diphosphate, flavin mononucleotide, and adenosine monophosphate. We found that inactivation of SLC25A17 resulted in a shift toward a more reductive state in the glutathione redox couple (GSSG/GSH) across HEK-293 cells, HeLa cells, and SV40-transformed mouse embryonic fibroblasts, with variable impact on the NADPH levels and the NAD+/NADH redox couple. This phenotype could be rescued by the expression of Candida boidinii Pmp47, a putative SLC25A17 orthologue reported to be essential for the metabolism of medium-chain fatty acids in yeast peroxisomes. In addition, we provide evidence that the alterations in the redox state are not caused by changes in peroxisomal antioxidant enzyme expression, catalase activity, H2O2 membrane permeability, or mitochondrial fitness. Furthermore, treating control and ΔSLC25A17 cells with dehydroepiandrosterone, a commonly used glucose-6-phosphate dehydrogenase inhibitor affecting NADPH regeneration, revealed a kinetic disconnection between the peroxisomal and cytosolic glutathione pools. Additionally, these experiments underscored the impact of SLC25A17 loss on peroxisomal NADPH metabolism. The relevance of these findings is discussed in the context of the still ambiguous substrate specificity of SLC25A17 and the recent observation that the mammalian peroxisomal membrane is readily permeable to both GSH and GSSG.

Keywords:  CoA; Glutathione; Metabolite transport; NADPH; PMP34; Peroxisomes; Redox compartmentalization; SLC25A17

DOI:  https://doi.org/10.1016/j.freeradbiomed.2023.12.035
Sci Rep. 2024 01 02. 14(1): 15

Alterations in mitochondria isolated from peripheral blood mononuclear cells and tumors of patients with epithelial ovarian cancers.

Kittipat Charoenkwan, Nattayaporn Apaijai, Sirawit Sriwichaiin, Nipon Chattipakorn, Siriporn C Chattipakorn.

Metabolic alterations play an essential role in ovarian carcinogenesis. The flexibility of mitochondrial functions facilitates cellular adaptation to the tough environment associated with carcinogenesis. An understanding of the differences in mitochondrial functions in normal ovaries and cancers could provide a basis for further exploration of future mitochondria-based screening, diagnosis, prognostic prediction, and targeted therapy for epithelial ovarian cancers. The main objective of this study was to assess mitochondrial function profiles measured from PBMCs and ovarian tissues of epithelial ovarian cancers in comparison with normal ovaries. A total of 36 patients were recruited for the study, all of whom underwent primary surgical treatment for malignant epithelial ovarian neoplasm. Of these, 20 patients were in the early stage and 16 patients were in the advanced stage. Additionally, 21 patients who had pelvic surgery for benign gynecologic conditions, with normal ovaries incidentally removed, were recruited as controls. At the time of surgery, a blood sample was collected from each participant for PBMC isolation, and ovarian tissue was retained for molecular studies. These studies included the examination of oxidative stress, mitochondrial mass, mitochondrial respiration, mitochondrial reactive oxygen species (ROS), mitochondrial membrane potential (MMP) changes, and mitochondrial swelling. Clinical and histopathological data were also collected and compared between different stages of epithelial ovarian cancers: early-stage (group 1), advanced-stage (group 2), and normal ovaries (group 3). The levels of cellular oxidative stress, mitochondrial mass, and mitochondrial biogenesis in the peripheral blood mononuclear cells (PBMCs) of participants with ovarian cancer were significantly lower than those of the control group. However, the mitochondrial respiratory parameters measured from the PBMCs were similar across all three groups. Furthermore, mitochondrial membrane depolarization and mitochondrial swelling were observed in ovarian tissues of both early-stage and advanced-stage cancer groups. We demonstrated the dynamic nature of mitochondrial ROS production, biogenesis, and respiratory function in response to epithelial ovarian carcinogenesis. The flexibility of mitochondrial functions under diverse conditions may make it a challenging therapeutic target for ovarian cancer.

DOI: https://doi.org/10.1038/s41598-023-51009-z
Anal Chem. 2024 Jan 04.

Mitochondrial Esterase Activity Measured at the Single Organelle Level by Nano-flow Cytometry.

Liyun Su, Kaimin Gao, Ye Tian, Xu Xiao, Cheng Lu, Jingyi Xu, Xiaomei Yan.

Monitoring mitochondrial esterase activity is crucial not only for investigating mitochondrial metabolism but also for assessing the effectiveness of mitochondrial-targeting prodrugs. However, accurately detecting esterase activity within mitochondria poses challenges due to its ubiquitous presence in cells and the uncontrolled localization of fluorogenic probes. To overcome this hurdle and reveal variations among different mitochondria, we isolated mitochondria and preserved their activity and functionality in a buffered environment. Subsequently, we utilized a laboratory-built nano-flow cytometer in conjunction with an esterase-responsive calcein-AM fluorescent probe to measure the esterase activity of individual mitochondria. This approach enabled us to investigate the influence of temperature, pH, metal ions, and various compounds on the mitochondrial esterase activity without any interference from other cellular constituents. Interestingly, we observed a decline in the mitochondrial esterase activity following the administration of mitochondrial respiratory chain inhibitors. Furthermore, we found that mitochondrial esterase activity was notably higher in the presence of a high concentration of ATP compared to that of ADP and AMP. Additionally, we noticed a correlation between elevated levels of complex IV and increased mitochondrial esterase activity. These findings suggest a functional connection between the mitochondrial respiratory chain and mitochondrial esterase activity. Moreover, we detected an upsurge in mitochondrial esterase activity during the early stages of apoptosis, while cellular esterase activity decreased. This highlights the significance of analyzing enzyme activity within specific organelle subregions. In summary, the integration of a nano-flow cytometer and fluorescent dyes introduces a novel method for quantifying mitochondrial enzyme activity with the potential to uncover the alterations and unique functions of other mitochondrial enzymes.

DOI: https://doi.org/10.1021/acs.analchem.3c04321
Proc Natl Acad Sci U S A. 2024 Jan 09. 121(2): e2306454120

HKDC1, a target of TFEB, is essential to maintain both mitochondrial and lysosomal homeostasis, preventing cellular senescence.

Mengying Cui, Koji Yamano, Kenichi Yamamoto, Hitomi Yamamoto-Imoto, Satoshi Minami, Takeshi Yamamoto, Sho Matsui, Tatsuya Kaminishi, Takayuki Shima, Monami Ogura, Megumi Tsuchiya, Kohei Nishino, Brian T Layden, Hisakazu Kato, Hidesato Ogawa, Shinya Oki, Yukinori Okada, Yoshitaka Isaka, Hidetaka Kosako, Noriyuki Matsuda, Tamotsu Yoshimori, Shuhei Nakamura.

  Mitochondrial and lysosomal functions are intimately linked and are critical for cellular homeostasis, as evidenced by the fact that cellular senescence, aging, and multiple prominent diseases are associated with concomitant dysfunction of both organelles. However, it is not well understood how the two important organelles are regulated. Transcription factor EB (TFEB) is the master regulator of lysosomal function and is also implicated in regulating mitochondrial function; however, the mechanism underlying the maintenance of both organelles remains to be fully elucidated. Here, by comprehensive transcriptome analysis and subsequent chromatin immunoprecipitation-qPCR, we identified hexokinase domain containing 1 (HKDC1), which is known to function in the glycolysis pathway as a direct TFEB target. Moreover, HKDC1 was upregulated in both mitochondrial and lysosomal stress in a TFEB-dependent manner, and its function was critical for the maintenance of both organelles under stress conditions. Mechanistically, the TFEB-HKDC1 axis was essential for PINK1 (PTEN-induced kinase 1)/Parkin-dependent mitophagy via its initial step, PINK1 stabilization. In addition, the functions of HKDC1 and voltage-dependent anion channels, with which HKDC1 interacts, were essential for the clearance of damaged lysosomes and maintaining mitochondria-lysosome contact. Interestingly, HKDC1 regulated mitophagy and lysosomal repair independently of its prospective function in glycolysis. Furthermore, loss function of HKDC1 accelerated DNA damage-induced cellular senescence with the accumulation of hyperfused mitochondria and damaged lysosomes. Our results show that HKDC1, a factor downstream of TFEB, maintains both mitochondrial and lysosomal homeostasis, which is critical to prevent cellular senescence.

Keywords:  HKDC1; TFEB; cellular senescence; mitochondria–lysosome contact; mitophagy

DOI:  https://doi.org/10.1073/pnas.2306454120
PLoS One. 2024 ;19(1): e0287865

Characterization of genetic and molecular tools for studying the endogenous expression of Lactate dehydrogenase in Drosophila melanogaster.

Madhulika Rai, Sarah M Carter, Shefali A Shefali, Geetanjali Chawla, Jason M Tennessen.

Drosophila melanogaster larval development relies on a specialized metabolic state that utilizes carbohydrates and other dietary nutrients to promote rapid growth. One unique feature of the larval metabolic program is that Lactate Dehydrogenase (Ldh) activity is highly elevated during this growth phase when compared to other stages of the fly life cycle, indicating that Ldh serves a key role in promoting juvenile development. Previous studies of larval Ldh activity have largely focused on the function of this enzyme at the whole animal level, however, Ldh expression varies significantly among larval tissues, raising the question of how this enzyme promotes tissue-specific growth programs. Here we characterize two transgene reporters and an antibody that can be used to study Ldh expression in vivo. We find that all three tools produce similar Ldh expression patterns. Moreover, these reagents demonstrate that the larval Ldh expression pattern is complex, suggesting the purpose of this enzyme varies across cell types. Overall, our studies validate a series of genetic and molecular reagents that can be used to study glycolytic metabolism in the fly.

DOI: https://doi.org/10.1371/journal.pone.0287865
ACS Nano. 2024 Jan 05.

Nanotechnology Reprogramming Metabolism for Enhanced Tumor Immunotherapy.

Yangkai Zhou, Jing Yuan, Ke Xu, Shilin Li, Ying Liu.

  Mutation burden, hypoxia, and immunoediting contribute to altered metabolic profiles in tumor cells, resulting in a tumor microenvironment (TME) characterized by accumulation of toxic metabolites and depletion of various nutrients, which significantly hinder the antitumor immunity via multiple mechanisms, hindering the efficacy of tumor immunotherapies. In-depth investigation of the mechanisms underlying these phenomena are vital for developing effective antitumor drugs and therapies, while the therapeutic effects of metabolism-targeting drugs are restricted by off-target toxicity toward effector immune cells and high dosage-mediated side effects. Nanotechnologies, which exhibit versatility and plasticity in targeted delivery and metabolism modulation, have been widely applied to boost tumor immunometabolic therapies via multiple strategies, including targeting of metabolic pathways. In this review, recent advances in understanding the roles of tumor cell metabolism in both immunoevasion and immunosuppression are reviewed, and nanotechnology-based metabolic reprogramming strategies for enhanced tumor immunotherapies are discussed.

Keywords:  Adaptive immunity; Innate immunity; Metabolism; Metabolites; Nanotechnology; Tumor heterogenicity; Tumor immunotherapy; Tumor microenvironment

DOI:  https://doi.org/10.1021/acsnano.3c11260
Mol Cell. 2023 Dec 20. pii: S1097-2765(23)01027-4. [Epub ahead of print]

Dual regulation of SLC25A39 by AFG3L2 and iron controls mitochondrial glutathione homeostasis.

Xiaojian Shi, Marisa DeCiucis, Kariona A Grabinska, Jean Kanyo, Adam Liu, Tukiet T Lam, Hongying Shen.

  Organelle transporters define metabolic compartmentalization, and how this metabolite transport process can be modulated is poorly explored. Here, we discovered that human SLC25A39, a mitochondrial transporter critical for mitochondrial glutathione uptake, is a short-lived protein under dual regulation at the protein level. Co-immunoprecipitation mass spectrometry and CRISPR knockout (KO) in mammalian cells identified that mitochondrial m-AAA protease AFG3L2 is responsible for degrading SLC25A39 through the matrix loop 1. SLC25A39 senses mitochondrial iron-sulfur cluster using four matrix cysteine residues and inhibits its degradation. SLC25A39 protein regulation is robust in developing and mature neurons. This dual transporter regulation, by protein quality control and metabolic sensing, allows modulating mitochondrial glutathione level in response to iron homeostasis, opening avenues for exploring regulation of metabolic compartmentalization. Neuronal SLC25A39 regulation connects mitochondrial protein quality control, glutathione, and iron homeostasis, which were previously unrelated biochemical features in neurodegeneration.

Keywords:  AFG3L2; SLC25A39; glutathione; iron; mitochondrial transporter; protein quality control

DOI:  https://doi.org/10.1016/j.molcel.2023.12.008
iScience. 2024 Jan 19. 27(1): 108506

Basic pathway decomposition of biochemical reaction networks within growing cells.

Jay R Walton, Paul A Lindahl.

  This contribution treats linear, steady-state dynamics for a metabolic network within a growing cell. Admissible steady-state reaction fluxes are assumed to form a pointed, convex, polyhedral, conical subset of the stoichiometric null-space. A solution of the problem is defined to consist of a linear basis for the stoichiometric null-space consisting of admissible fluxes called basic pathways. The algorithm used to construct the set of basic pathways scales as a polynomial of the system size in contrast to the NP-hard algorithms employed in the traditional notions of solution named extreme pathways, elementary flux modes, MEMos, and MinSpan, and that therefore suffer from the curse of dimensionality. The basic pathways approach is applied to a metabolic network consisting of a simplified version of the TCA cycle coupled to glycolysis highlighting that each basic pathway has a readily understood chemical interpretation. Generic admissible pathways are simply expressed in terms of basic pathways.

Keywords:  Biological sciences; Metabolic engineering; Network

DOI:  https://doi.org/10.1016/j.isci.2023.108506
Cell Rep. 2023 Dec 30. pii: S2211-1247(23)01640-6. [Epub ahead of print]43(1): 113629

Metabolic reprogramming by histone deacetylase inhibition preferentially targets NRF2-activated tumors.

Dimitris Karagiannis, Warren Wu, Albert Li, Makiko Hayashi, Xiao Chen, Michaela Yip, Vaibhav Mangipudy, Xinjing Xu, Francisco J Sánchez-Rivera, Yadira M Soto-Feliciano, Jiangbin Ye, Thales Papagiannakopoulos, Chao Lu.

  The interplay between metabolism and chromatin signaling is implicated in cancer progression. However, whether and how metabolic reprogramming in tumors generates chromatin vulnerabilities remain unclear. Lung adenocarcinoma (LUAD) tumors frequently harbor aberrant activation of the NRF2 antioxidant pathway, which drives aggressive and chemo-resistant disease. Using a chromatin-focused CRISPR screen, we report that NRF2 activation sensitizes LUAD cells to genetic and chemical inhibition of class I histone deacetylases (HDACs). This association is observed across cultured cells, mouse models, and patient-derived xenografts. Integrative epigenomic, transcriptomic, and metabolomic analysis demonstrates that HDAC inhibition causes widespread redistribution of H4ac and its reader protein, which transcriptionally downregulates metabolic enzymes. This results in reduced flux into amino acid metabolism and de novo nucleotide synthesis pathways that are preferentially required for the survival of NRF2-active cancer cells. Together, our findings suggest NRF2 activation as a potential biomarker for effective repurposing of HDAC inhibitors to treat solid tumors.

Keywords:  CP: Cancer; HDAC inhibitors; NRF2 pathway; cancer epigenetics; cancer metabolism; cancer targeted therapy; epigenetic reprogramming; lung cancer

DOI:  https://doi.org/10.1016/j.celrep.2023.113629
Nat Commun. 2024 Jan 02. 15(1): 45

Fatty acid synthesis suppresses dietary polyunsaturated fatty acid use.

Anna Worthmann, Julius Ridder, Sharlaine Y L Piel, Ioannis Evangelakos, Melina Musfeldt, Hannah Voß, Marie O'Farrell, Alexander W Fischer, Sangeeta Adak, Monica Sundd, Hasibullah Siffeti, Friederike Haumann, Katja Kloth, Tatjana Bierhals, Markus Heine, Paul Pertzborn, Mira Pauly, Julia-Josefine Scholz, Suman Kundu, Marceline M Fuh, Axel Neu, Klaus Tödter, Maja Hempel, Uwe Knippschild, Clay F Semenkovich, Hartmut Schlüter, Joerg Heeren, Ludger Scheja, Christian Kubisch, Christian Schlein.

Dietary polyunsaturated fatty acids (PUFA) are increasingly recognized for their health benefits, whereas a high production of endogenous fatty acids - a process called de novo lipogenesis (DNL) - is closely linked to metabolic diseases. Determinants of PUFA incorporation into complex lipids are insufficiently understood and may influence the onset and progression of metabolic diseases. Here we show that fatty acid synthase (FASN), the key enzyme of DNL, critically determines the use of dietary PUFA in mice and humans. Moreover, the combination of FASN inhibition and PUFA-supplementation decreases liver triacylglycerols (TAG) in mice fed with high-fat diet. Mechanistically, FASN inhibition causes higher PUFA uptake via the lysophosphatidylcholine transporter MFSD2A, and a diacylglycerol O-acyltransferase 2 (DGAT2)-dependent incorporation of PUFA into TAG. Overall, the outcome of PUFA supplementation may depend on the degree of endogenous DNL and combining PUFA supplementation and FASN inhibition might be a promising approach to target metabolic disease.

DOI: https://doi.org/10.1038/s41467-023-44364-y
Cell Metab. 2024 Jan 02. pii: S1550-4131(23)00452-7. [Epub ahead of print]36(1): 103-115.e4

Glycine homeostasis requires reverse SHMT flux.

Matthew J McBride, Craig J Hunter, Zhaoyue Zhang, Tara TeSlaa, Xincheng Xu, Gregory S Ducker, Joshua D Rabinowitz.

  The folate-dependent enzyme serine hydroxymethyltransferase (SHMT) reversibly converts serine into glycine and a tetrahydrofolate-bound one-carbon unit. Such one-carbon unit production plays a critical role in development, the immune system, and cancer. Using rodent models, here we show that the whole-body SHMT flux acts to net consume rather than produce glycine. Pharmacological inhibition of whole-body SHMT1/2 and genetic knockout of liver SHMT2 elevated circulating glycine levels up to eight-fold. Stable-isotope tracing revealed that the liver converts glycine to serine, which is then converted by serine dehydratase into pyruvate and burned in the tricarboxylic acid cycle. In response to diets deficient in serine and glycine, de novo biosynthetic flux was unaltered, but SHMT2- and serine-dehydratase-mediated catabolic flux was lower. Thus, glucose-derived serine synthesis is largely insensitive to systemic demand. Instead, circulating serine and glycine homeostasis is maintained through variable consumption, with liver SHMT2 a major glycine-consuming enzyme.

Keywords:  SHMT; amino acid metabolism; folate cycle; glycine; hepatic clearance; homeostasis; serine

DOI:  https://doi.org/10.1016/j.cmet.2023.12.001
Cell Commun Signal. 2024 Jan 03. 22(1): 12

Glutamine addiction in tumor cell: oncogene regulation and clinical treatment.

Xian Li, Xueqiang Peng, Yan Li, Shibo Wei, Guangpeng He, Jiaxing Liu, Xinyu Li, Shuo Yang, Dai Li, Weikai Lin, Jianjun Fang, Liang Yang, Hangyu Li.

   After undergoing metabolic reprogramming, tumor cells consume additional glutamine to produce amino acids, nucleotides, fatty acids, and other substances to facilitate their unlimited proliferation. As such, the metabolism of glutamine is intricately linked to the survival and progression of cancer cells. Consequently, targeting the glutamine metabolism presents a promising strategy to inhibit growth of tumor cell and cancer development. This review describes glutamine uptake, metabolism, and transport in tumor cells and its pivotal role in biosynthesis of amino acids, fatty acids, nucleotides, and more. Furthermore, we have also summarized the impact of oncogenes like C-MYC, KRAS, HIF, and p53 on the regulation of glutamine metabolism and the mechanisms through which glutamine triggers mTORC1 activation. In addition, role of different anti-cancer agents in targeting glutamine metabolism has been described and their prospective applications are assessed.

Keywords:  Glutamine; Metabolism; Oncogene clinical treatment; Tumor

DOI:  https://doi.org/10.1186/s12964-023-01449-x
Int J Biol Sci. 2024 ;20(2): 516-536

p32 regulates glycometabolism and TCA cycle to inhibit ccRCC progression via copper-induced DLAT lipoylation oligomerization.

Shaoping Tian, Rui Wang, Yiting Wang, Ruibing Chen, Tianyu Lin, Xuesong Xiao, Xinyu Liu, Justin Eze Ideozu, Hua Geng, Yong Wang, Dan Yue.

  A key player in mitochondrial respiration, p32, often referred to as C1QBP, is mostly found in the mitochondrial matrix. Previously, we showed that p32 interacts with DLAT in the mitochondria. Here, we found that p32 expression was reduced in ccRCC and suppressed progression and metastasis in ccRCC animal models. We observed that increasing p32 expression led to an increase in oxidative phosphorylation by interacting with DLAT, thus, regulating the activation of the pyruvate dehydrogenase complex (PDHc). Mechanistically, reduced p32 expression, in concert with DLAT, suppresses PDHc activity and the TCA cycle. Furthermore, our research discovered that p32 has a direct binding affinity for copper, facilitating the copper-induced oligomerization of lipo-DLAT specifically in ccRCC cells. This finding reveals an innovative function of the p32/DLAT/copper complex in regulating glycometabolism and the TCA cycle in ccRCC. Importantly, our research provides important new understandings of the underlying molecular processes causing the abnormal mitochondrial metabolism linked to this cancer.

Keywords:  Clear cell renal cell carcinoma; Copper; DLAT; glycometabolism; p32; tricarboxylic acid cycle

DOI:  https://doi.org/10.7150/ijbs.84399
bioRxiv. 2023 Dec 12. pii: 2023.12.11.571124. [Epub ahead of print]

An interactive web application for exploring human plasma and fibroblast metabolomics data from patients with inborn errors of metabolism.

Ling Cai, Hieu S Vu, Wen Gu, Hongli Chen, Jordan Franklin, Lea Abou Haidar, Zheng Wu, Chunxiao Pan, Feng Cai, Phong Nguyen, Bookyung Ko, Chendong Yang, Lauren G Zacharias, Jessica Sudderth, Sarah Montgomery, Crescenda Uhles, Heather Fisher, Julianna Hudnall, Callie Hornbuckle, Christine Quinn, Donnice Michel, Luis Umaña, Angela Scheuerle, Markey C McNutt, Garrett K Gotway, Bushra Afroze, Min Ni, Ralph DeBerardinis.

Metabolomic profiling is instrumental in understanding the systemic and cellular impact of inborn errors of metabolism (IEMs), monogenic disorders caused by pathogenic genomic variants in genes involved in metabolism. This study encompasses untargeted metabolomics analysis of plasma from 474 individuals and fibroblasts from 67 subjects, incorporating healthy controls, patients with 65 different monogenic diseases, and numerous undiagnosed cases. We introduce a web application designed for the in-depth exploration of this extensive metabolomics database. The application offers a user-friendly interface for data review, download, and detailed analysis of metabolic deviations linked to IEMs at the level of individual patients or groups of patients with the same diagnosis. It also provides interactive tools for investigating metabolic relationships and offers comparative analyses of plasma and fibroblast profiles. This tool emphasizes the metabolic interplay within and across biological matrices, enriching our understanding of metabolic regulation in health and disease. As a resource, the application provides broad utility in research, offering novel insights into metabolic pathways and their alterations in various disorders.

DOI: https://doi.org/10.1101/2023.12.11.571124
EMBO Rep. 2023 Dec 14.

MTCH2 cooperates with MFN2 and lysophosphatidic acid synthesis to sustain mitochondrial fusion.

Andres Goldman, Michael Mullokandov, Yehudit Zaltsman, Limor Regev, Smadar Levin-Zaidman, Atan Gross.

  Fusion of the outer mitochondrial membrane (OMM) is regulated by mitofusin 1 (MFN1) and 2 (MFN2), yet the differential contribution of each of these proteins is less understood. Mitochondrial carrier homolog 2 (MTCH2) also plays a role in mitochondrial fusion, but its exact function remains unresolved. MTCH2 overexpression enforces MFN2-independent mitochondrial fusion, proposedly by modulating the phospholipid lysophosphatidic acid (LPA), which is synthesized by glycerol-phosphate acyl transferases (GPATs) in the endoplasmic reticulum (ER) and the OMM. Here we report that MTCH2 requires MFN1 to enforce mitochondrial fusion and that fragmentation caused by loss of MTCH2 can be specifically counterbalanced by overexpression of MFN2 but not MFN1, partially independent of its GTPase activity and mitochondrial localization. Pharmacological inhibition of GPATs (GPATi) or silencing ER-resident GPATs suppresses MFN2's ability to compensate for the loss of MTCH2. Loss of either MTCH2, MFN2, or GPATi does not impair stress-induced mitochondrial fusion, whereas the combined loss of MTCH2 and GPATi or the combined loss of MTCH2 and MFN2 does. Taken together, we unmask two cooperative mechanisms that sustain mitochondrial fusion.

Keywords:  LPA; MFN2; MTCH2; Mitochondria-ER Communication; Mitochondrial Fusion

DOI:  https://doi.org/10.1038/s44319-023-00009-1
Talanta. 2023 Dec 28. pii: S0039-9140(23)01361-9. [Epub ahead of print]270 125610

A single mitochondria-targetable fluorescent probe for visualizing cysteine and glutathione in ferroptosis of myocardial ischemia/reperfusion injury.

Jiayu Zeng, Minhui Liu, Ting Yang, Songjiao Li, Dan Cheng, Longwei He.

  Ferroptosis plays an important role in the early stage of myocardial ischemia/reperfusion (MI/R) injury, which is closely associated with the antioxidant damage of mitochondrial cysteine (Cys)/glutathione (GSH)/glutathione peroxidase 4 (GPX4) axis. Visualization of Cys and GSH in mitochondria is meaningful to value ferroptosis and further contributes to understanding and preventing MI/R injury. Herein a mitochondria-targetable thiols fluorescent probe (MTTP) was designed and synthesized based on sulfonyl benzoxadiazole (SBD) chromophore with a triphenylphosphine unit as the mitochondria-targeted functional group. Cys and GSH can be differentiated by MTTP with two distinguishable emission bands (583 nm and 520 nm) through the controllable aromatic substitution-rearrangement reaction. Importantly, MTTP is capable of monitoring ferroptosis and its inhibition by measuring mitochondrial Cys and GSH. MTTP was also employed to non-invasively detect ferroptosis during oxygen and glucose deprivation/reoxygenation (OGD/R)-induced MI/R injury in H9C2 cells. In a word, MTTP provides a visual tool that can simultaneously detect Cys and GSH to monitor ferroptosis processes during MI/R injury, which helps for more deeper understanding of the role of ferroptosis in MI/R injury-related diseases.

Keywords:  Cysteine; Ferroptosis; Fluorescent probe; Glutathione; Mitochondria; Myocardial ischemia/reperfusion injury

DOI:  https://doi.org/10.1016/j.talanta.2023.125610
Metabolomics. 2024 Jan 05. 20(1): 12

Serum metabolic signatures for Alzheimer's Disease reveal alterations in amino acid composition: a validation study.

Jonas Ellegaard Nielsen, Trygve Andreassen, Charlotte Held Gotfredsen, Dorte Aalund Olsen, Karsten Vestergaard, Jonna Skov Madsen, Søren Risom Kristensen, Shona Pedersen.

   INTRODUCTION: Alzheimer's Disease (AD) is complex and novel approaches are urgently needed to aid in diagnosis. Blood is frequently used as a source for biomarkers; however, its complexity prevents proper detection. The analytical power of metabolomics, coupled with statistical tools, can assist in reducing this complexity.
OBJECTIVES: Thus, we sought to validate a previously proposed panel of metabolic blood-based biomarkers for AD and expand our understanding of the pathological mechanisms involved in AD that are reflected in the blood.
METHODS: In the validation cohort serum and plasma were collected from 25 AD patients and 25 healthy controls. Serum was analysed for metabolites using nuclear magnetic resonance (NMR) spectroscopy, while plasma was tested for markers of neuronal damage and AD hallmark proteins using single molecule array (SIMOA).
RESULTS: The diagnostic performance of the metabolite biomarker panel was confirmed using sparse-partial least squares discriminant analysis (sPLS-DA) with an area under the curve (AUC) of 0.73 (95% confidence interval: 0.59-0.87). Pyruvic acid and valine were consistently reduced in the discovery and validation cohorts. Pathway analysis of significantly altered metabolites in the validation set revealed that they are involved in branched-chain amino acids (BCAAs) and energy metabolism (glycolysis and gluconeogenesis). Additionally, strong positive correlations were observed for valine and isoleucine between cerebrospinal fluid p-tau and t-tau.
CONCLUSIONS: Our proposed panel of metabolites was successfully validated using a combined approach of NMR and sPLS-DA. It was discovered that cognitive-impairment-related metabolites belong to BCAAs and are involved in energy metabolism.

Keywords:  Alzheimer; Biomarker; Metabolites; Nuclear magnetic resonance; Serum; Single molecule array

DOI:  https://doi.org/10.1007/s11306-023-02078-8
Nat Commun. 2024 Jan 04. 15(1): 205

VAP spatially stabilizes dendritic mitochondria to locally support synaptic plasticity.

Ojasee Bapat, Tejas Purimetla, Sarah Kruessel, Monil Shah, Ruolin Fan, Christina Thum, Fiona Rupprecht, Julian D Langer, Vidhya Rangaraju.

Synapses are pivotal sites of plasticity and memory formation. Consequently, synapses are energy consumption hotspots susceptible to dysfunction when their energy supplies are perturbed. Mitochondria are stabilized near synapses via the cytoskeleton and provide the local energy required for synaptic plasticity. However, the mechanisms that tether and stabilize mitochondria to support synaptic plasticity are unknown. We identified proteins exclusively tethering mitochondria to actin near postsynaptic spines. We find that VAP, the vesicle-associated membrane protein-associated protein implicated in amyotrophic lateral sclerosis, stabilizes mitochondria via actin near the spines. To test if the VAP-dependent stable mitochondrial compartments can locally support synaptic plasticity, we used two-photon glutamate uncaging for spine plasticity induction and investigated the induced and adjacent uninduced spines. We find VAP functions as a spatial stabilizer of mitochondrial compartments for up to ~60 min and as a spatial ruler determining the ~30 μm dendritic segment supported during synaptic plasticity.

DOI: https://doi.org/10.1038/s41467-023-44233-8
Mol Med. 2024 Jan 03. 30(1): 3

A new physiological medium uncovers biochemical and cellular alterations in Lesch-Nyhan disease fibroblasts.

Paula Escudero-Ferruz, Neus Ontiveros, Claudia Cano-Estrada, Diane J Sutcliffe, H A Jinnah, Rosa J Torres, José M López.

   BACKGROUND: Lesch-Nyhan disease (LND) is a severe neurological disorder caused by the genetic deficiency of hypoxanthine-guanine phosphoribosyltransferase (HGprt), an enzyme involved in the salvage synthesis of purines. To compensate this deficiency, there is an acceleration of the de novo purine biosynthetic pathway. Most studies have failed to find any consistent abnormalities of purine nucleotides in cultured cells obtained from the patients. Recently, it has been shown that 5-aminoimidazole-4-carboxamide riboside 5'-monophosphate (ZMP), an intermediate of the de novo pathway, accumulates in LND fibroblasts maintained with RPMI containing physiological levels (25 nM) of folic acid (FA), which strongly differs from FA levels of regular cell culture media (2200 nM). However, RPMI and other standard media contain non-physiological levels of many nutrients, having a great impact in cell metabolism that does not precisely recapitulate the in vivo behavior of cells.
METHODS: We prepared a new culture medium containing physiological levels of all nutrients, including vitamins (Plasmax-PV), to study the potential alterations of LND fibroblasts that may have been masked by the usage of non-physiological media. We quantified ZMP accumulation under different culture conditions and evaluated the activity of two known ZMP-target proteins (AMPK and ADSL), the mRNA expression of the folate carrier SLC19A1, possible mitochondrial alterations and functional consequences in LND fibroblasts.
RESULTS: LND fibroblasts maintained with Plasmax-PV show metabolic adaptations such a higher glycolytic capacity, increased expression of the folate carrier SCL19A1, and functional alterations such a decreased mitochondrial potential and reduced cell migration compared to controls. These alterations can be reverted with high levels of folic acid, suggesting that folic acid supplements might be a potential treatment for LND.
CONCLUSIONS: A complete physiological cell culture medium reveals new alterations in Lesch-Nyhan disease. This work emphasizes the importance of using physiological cell culture conditions when studying a metabolic disorder.

Keywords:  AICAR; Folic acid; Lesch-Nyhan disease; Plasmax; Purine nucleotides; ZMP

DOI:  https://doi.org/10.1186/s10020-023-00774-8
Cell Rep. 2023 Dec 30. pii: S2211-1247(23)01639-X. [Epub ahead of print]43(1): 113628

Two-pore channel-2 and inositol trisphosphate receptors coordinate Ca2+ signals between lysosomes and the endoplasmic reticulum.

Yu Yuan, Vikas Arige, Ryo Saito, Qianru Mu, Gabriela C Brailoiu, Gustavo J S Pereira, Stephen R Bolsover, Marco Keller, Franz Bracher, Christian Grimm, Eugen Brailoiu, Jonathan S Marchant, David I Yule, Sandip Patel.

  Lysosomes and the endoplasmic reticulum (ER) are Ca2+ stores mobilized by the second messengers NAADP and IP3, respectively. Here, we establish Ca2+ signals between the two sources as fundamental building blocks that couple local release to global changes in Ca2+. Cell-wide Ca2+ signals evoked by activation of endogenous NAADP-sensitive channels on lysosomes comprise both local and global components and exhibit a major dependence on ER Ca2+ despite their lysosomal origin. Knockout of ER IP3 receptor channels delays these signals, whereas expression of lysosomal TPC2 channels accelerates them. High-resolution Ca2+ imaging reveals elementary events upon TPC2 opening and signals coupled to IP3 receptors. Biasing TPC2 activation to a Ca2+-permeable state sensitizes local Ca2+ signals to IP3. This increases the potency of a physiological agonist to evoke global Ca2+ signals and activate a downstream target. Our data provide a conceptual framework to understand how Ca2+ release from physically separated stores is coordinated.

Keywords:  CP: Cell biology; Ca(2+) stores; IP(3); IP(3) receptors; NAADP; endoplasmic reticulum; histamine; lysosomes; puffs; tuffs; two-pore channels

DOI:  https://doi.org/10.1016/j.celrep.2023.113628
bioRxiv. 2023 Dec 17. pii: 2023.12.16.571979. [Epub ahead of print]

Lysosomal TBK1 Responds to Amino Acid Availability to Relieve Rab7-Dependent mTORC1 Inhibition.

Gabriel Talaia, Amanda Bentley-DeSousa, Shawn M Ferguson.

Lysosomes play a pivotal role in coordinating macromolecule degradation and regulating cell growth and metabolism. Despite substantial progress in identifying lysosomal signaling proteins, understanding the pathways that synchronize lysosome functions with changing cellular demands remains incomplete. This study uncovers a role for TANK-binding kinase 1 (TBK1), well known for its role in innate immunity and organelle quality control, in modulating lysosomal responsiveness to nutrients. Specifically, we identify a pool of TBK1 that is recruited to lysosomes in response to elevated amino acid levels. At lysosomes, this TBK1 phosphorylates Rab7 on serine 72. This is critical for alleviating Rab7-mediated inhibition of amino acid-dependent mTORC1 activation. Furthermore, a TBK1 mutant (E696K) associated with amyotrophic lateral sclerosis and frontotemporal dementia constitutively accumulates at lysosomes, resulting in elevated Rab7 phosphorylation and increased mTORC1 activation. This data establishes the lysosome as a site of amino acid regulated TBK1 signaling that is crucial for efficient mTORC1 activation. This lysosomal pool of TBK1 has broader implications for lysosome homeostasis, and its dysregulation could contribute to the pathogenesis of ALS-FTD.

DOI: https://doi.org/10.1101/2023.12.16.571979