bims-celmim 2026-08-02 papers

bims-celmim

Biomed News

on Cellular and mitochondrial metabolism

Issue of 2026–08–02
nineteen papers selected by
Marc Segarra Mondejar, AINA

PLK1-mediated phosphorylation of PHGDH reprograms serine metabolism in advanced prostate cancer.
Intermembrane coupling between Bcl-xL and the IP3 receptor supports local Ca2+ transfer at ER-mitochondrial contacts.
Mechanistic insights into lysosomal stress response network in carcinogenesis and therapeutic opportunities.
Signatures of aging and disease in a single organelle.
Atlas of lysosomal aging reveals a metabolite signature shared with lysosomal storage disorders.
Glutamine Metabolism Supports α cell Mass and Glucagon Secretion.
CCR5 drives glucose metabolic reprogramming to control microglial synaptic pruning via histone lactylation in a mouse model of depression.
SARS-CoV-2 ORF7a drives mitochondrial dysfunction via PDK4 activation and complex I inhibition.
Vimentin intermediate filaments support autophagosome biogenesis at ER-endosome contact sites in response to starvation.
The phase separation of ZC3H18 transcriptionally activates LDHA and forms lactylation-mediated positive feedback loop to promote tumorigenesis of lung cancer.
A Role for Astrocyte Metabolism in Species-Specific Neuronal Development.
An adaptor for feedback regulation of heme biosynthesis by a mitochondrial protease.
Futile cycles in metabolic flexibility: The energetic cost of regulatory precision.
Spatiotemporal control of Atg2 association with the ER during autophagosome formation.
Demonstrating Fluorescent Peptidyl Inhibitor Targeting of Mitochondrial ClpXP by Fluorescence Microscopy in Mammalian Cells.
Mitochondrial control of amino acid catabolism by a fasting-inducible mitochondrial carrier.
Sterol Flux Rewiring: Cholesterol Biosynthesis as a Dynamic Signaling Network.
Transsulfuration links aspartate-asparagine metabolism and redox homeo-stasis to drive tumor growth.
Mapping the chaperonin TRiC/CCT interactome in mouse photoreceptors reveals functional significance for energy metabolism.

Proc Natl Acad Sci U S A. 2026 Aug 04. 123(31): e2618349123

PLK1-mediated phosphorylation of PHGDH reprograms serine metabolism in advanced prostate cancer.

Xiongjian Rao, Derek B Allison, Robert M Flight, Penghui Lin, Daheng He, Zhiguo Li, Yanquan Zhang, Ruixin Wang, Chaohao Li, Jianlin Wang, Xinyi Wang, Jia Peng, Ka Wing Fong, Qing Shao, Chi Wang, Eunus S Ali, Hunter N B Moseley, Xiaoqi Liu.

  Metabolic reprogramming is a hallmark of cancer, enabling tumor cells to meet their increased biosynthetic and energetic demands. Although cells possess the capacity for de novo serine biosynthesis, most transformed cancer cells preferentially rely on exogenous serine uptake to sustain their growth, yet the regulatory mechanisms driving this metabolic dependency remain poorly understood. Here, we uncover a mechanism by which Polo-like kinase 1 (PLK1), frequently overexpressed in prostate cancer, orchestrates a metabolic shift in serine and sphingolipid metabolism through phosphorylation of phosphoglycerate dehydrogenase (PHGDH), the rate-limiting enzyme of the serine synthesis pathway (SSP). Specifically, PLK1 directly phosphorylates PHGDH at S512, S513, and S517, leading to a marked reduction in its protein level and enzymatic activity. This downregulation of de novo serine biosynthesis forces cancer cells to increase their reliance on exogenous serine uptake via the ASCT2 transporter, which in turn fuels the biosynthesis of lipids, including sphingolipids essential for tumor growth and survival. Our findings suggest that targeting the SSP, serine uptake, or downstream lipid biosynthesis pathways may represent promising therapeutic strategies in advanced cancers characterized by PLK1 dysregulation.

Keywords:  PHGDH; PLK1; metabolism; serine; sphingolipids

DOI:  https://doi.org/10.1073/pnas.2618349123
Cell Rep. 2026 Jul 30. pii: S2211-1247(26)00845-4. [Epub ahead of print]45(8): 117767

Intermembrane coupling between Bcl-xL and the IP3 receptor supports local Ca2+ transfer at ER-mitochondrial contacts.

Arijita Ghosh, David Weaver, Chi Li, Gyӧrgy Hajnóczky.

  Bcl-xL, an anti-apoptotic Bcl-2 family protein, engages laterally with Bak/Bax in the outer mitochondrial membrane (OMM) to inhibit apoptosis and interacts with the IP3 receptor Ca2+ channels (IP3Rs) in the endoplasmic reticulum (ER) membrane to control Ca2+ release. It is unknown if OMM-localized Bcl-xL can also interact in trans with IP3Rs at ER-mitochondrial contacts to form a tethering complex that supports IP3R-mediated local Ca2+ transfer from ER to mitochondria. We establish that IP3R-mitochondria Ca2+ signal propagation depends on Bcl-xL. By targeting Bcl-xL specifically to different subcellular compartments, we find that OMM-localized Bcl-xL increases the efficacy of ER-mitochondrial Ca2+ transfer without changing ER Ca2+ release, despite attenuating mitochondrial Ca2+ uptake. We find interaction between Bcl-xL and each IP3R isoform occurring at the mitochondria and a complex formed by OMM-localized Bcl-xL and IP3Rs. OMM Bcl-xL interacts with IP3Rs in trans at ER-mitochondrial contacts to optimize local Ca2+ signal propagation into the mitochondria.

Keywords:  Bcl-xL; CP: cell biology; CP: metabolism; ERMC; IP3R; calcium signaling; endoplasmic reticulum; local Ca(2+) transfer; mitochondria; organellar crosstalk

DOI:  https://doi.org/10.1016/j.celrep.2026.117767
Biochim Biophys Acta Rev Cancer. 2026 Jul 25. pii: S0304-419X(26)00141-1. [Epub ahead of print] 189669

Mechanistic insights into lysosomal stress response network in carcinogenesis and therapeutic opportunities.

Amruta Singh, Soumyadip Sinha, Prakash Kumar Senapati, Kewal Kumar Mahapatra, Sujit Kumar Bhutia.

  Lysosomes are vital organelles that maintain cellular homeostasis and orchestrate dynamic adaptations during physiological and pathological stress. Lysosomal damage, caused by various extrinsic and intrinsic factors, impairs its integrity and simultaneously disrupts the normal functioning of other organelles, including the endoplasmic reticulum and mitochondria. Lysosomal homeostasis through the lysosomal stress response (LSR) network aids cells in adapting to organelle damage, nutrient fluctuations, oxidative stress, and metabolic irregularities. This coordinated network is primarily governed by proteins, including mTOR, TFEB/TFE3, AMPK, Rag GTPases, Ragulator, and TRPML1, which integrates mechanisms involving rapid lysosomal membrane repair, selective elimination of extensively damaged lysosomes, de novo lysosomal biogenesis, and lysosomal reformation pathways. Dysregulation of the LSR network leads to different types of diseases, including cancer. This review summarizes the current understanding of lysosomal damage mitigation, particularly in cancer, where remodeling of the LSR network not only enables cancer cells to maintain metabolic plasticity by resisting therapeutic stress and promoting malignancy but also identifies the LSR network as a critical determinant in tumorigenesis. We further provide a detailed discussion of emerging evidence on the disruption of lysosomal homeostasis, highlighting strong links between lysosome-targeting drugs and cancer therapeutics. Altogether, we establish the LSR network as a central regulator of cellular homeostasis, thereby emerging as a promising therapeutic target in cancer and other lysosome-associated disorders.

Keywords:  Cancer; Lysosomal damage; Lysosomal homeostasis; Lysosomal stress response (LSR) network

DOI:  https://doi.org/10.1016/j.bbcan.2026.189669
Science. 2026 Jul 30. 393(6810): 461

Signatures of aging and disease in a single organelle.

Jeeyoon Na, Anne Brunet.

Changes in lysosomal metabolites are associated with both aging organs and lysosomal storage diseases.

DOI: https://doi.org/10.1126/science.aej5901
Science. 2026 Jul 30. 393(6810): eady0832

Atlas of lysosomal aging reveals a metabolite signature shared with lysosomal storage disorders.

Anna M Puszynska, Thao P Nguyen, Andrew L Cangelosi, Andrea Armani, Justin M Roberts, Kristin A Singh, James C Cameron, Tenzin Tseyang, Grace Y Liu, Steven Lai, Hans-Georg Sprenger, Jason Yang, William N Colgan, Jibril F Kedir, Kathrin M Kajderowicz, Theodore K Esantsi, Yuancheng Ryan Lu, Millenia Waite, Tenzin Kunchok, Caroline A Lewis, Fabian Schulte, George W Bell, David M Sabatini, Jonathan S Weissman.

Lysosomal dysfunction is a well-recognized feature of aging. Here, we used a suite of tools for rapid lysosomal isolation to construct a multitissue atlas of the metabolite changes lysosomes undergo during aging. Aged lysosomes in brain, heart, muscle, and white adipose tissue accumulated glycerophosphodiesters and cystine, metabolites that are causally linked to juvenile lysosomal storage disorders, Batten disease, and cystinosis. Levels of these metabolites increased linearly with age, preceding organismal decline. Caloric restriction, a lifespan-extending intervention, mitigated these changes in the heart and muscle but not the brain. Our findings link lysosomal storage disorders to aging-related dysfunction and open avenues for the mechanistic investigation of how lysosomal functions deteriorate during aging and in age-associated diseases.

DOI: https://doi.org/10.1126/science.ady0832
bioRxiv. 2026 Jul 13. pii: 2026.07.09.735845. [Epub ahead of print]

Glutamine Metabolism Supports α cell Mass and Glucagon Secretion.

Anna Marie R Schornack, Tyler J Rodgers, Matthew Shou, Walter A Siv, Linlin Yin, Katelyn Sellick, Varsha Chigurupati, Joshua Debo, Soham Saraf, Paula G Nickles, Selina Park, Shannon E Gibson, Nitin Shankar, Jordyn R Dobson, Soma Behera, Jade E Stanley, Angelina Ehara, Madushika Wimalarathne, Amber Crabtree, Austin Reuter, Alan Attie, Elma Zaganjor, Katie C Coate, Yan Li, Jeffrey C Rathmell, Mark P Keller, David A Jacobson, Wenbiao Chen, E Danielle Dean.

The liver-α cell axis is a finely tuned biological rheostat that regulates whole body amino acid availability. Pancreatic α cells secrete glucagon that regulates amino acid catabolism through gluconeogenesis and ureagenesis, yet the mechanisms linking amino acid levels to α cell growth and function are not fully understood. Here, we identify glutaminase, the enzyme that catalyzes glutamine catabolism, as a critical α cell regulator. Glutaminase is highly enriched in α cells across species. α cell expression of glutaminase is required for nutrient-dependent mTORC1 activation, suppression of AMPK signaling, and sustained expression of the glutamine transporter SLC38A5. This establishes a feed-forward loop linking glutamine metabolism to amino acid sensing and growth. Reduced glutaminase activity impairs dynamic glucagon secretion in response to low glucose and amino acids. Together, these findings highlight the importance of glutamine metabolism in α cell growth and hormone secretion and suggest it may play a role in α cell adaptation to hyperaminoacidemia.

DOI: https://doi.org/10.64898/2026.07.09.735845
Cell Rep. 2026 Jul 29. pii: S2211-1247(26)00827-2. [Epub ahead of print]45(8): 117749

CCR5 drives glucose metabolic reprogramming to control microglial synaptic pruning via histone lactylation in a mouse model of depression.

Ying-Ying Jiao, Zhu Zhu, Rui-An Wang, Ben-Yu He, Hang Yao, Zhi-Yong Zhou, Yun-Fan Shi, Cong Wang, Lei Cao, Yang Liu, Gang Hu, Ren-Hong Du, Ming Lu.

  Depression is linked to microglial activation, but the precise triggers and downstream pathways remain elusive. Through single-cell RNA sequencing of human blood samples, we find upregulation of the CCL5-CCR5 axis in patients with major depressive disorder. Using a chronic social defeat stress mouse model, we show that CCR5 is specifically elevated in activated hippocampal microglia. Microglia-specific deletion of CCR5 alleviates depressive-like behaviors and prevents microglial activation. Mechanistically, CCR5 binding to VHL stabilizes HIF-1α, redirecting microglial metabolism toward aerobic glycolysis. This metabolic shift results in lactate accumulation, which drives histone H4 lysine 12 lactylation (H4K12la). Genome-wide profiling reveals that H4K12la enrichment at complement gene promoters facilitates their transcription, ultimately leading to excessive microglial engulfment of neuronal spines and synaptic loss. Importantly, either inhibiting glycolysis or exogenous lactate supplementation can respectively rescue or mimic the pathological synaptic pruning and depressive-like behaviors. Our findings indicate a CCR5-driven immune-metabolic-transcriptional axis in microglia that underlies synaptic deficits in depressive-like behaviors, offering potential targets for therapeutic intervention.

Keywords:  CCR5; CP: neuroscience; depression; histone lactylation; metabolic reprogramming; metabolism; microglia; synaptic pruning

DOI:  https://doi.org/10.1016/j.celrep.2026.117749
Cell Rep. 2026 Jul 28. pii: S2211-1247(26)00833-8. [Epub ahead of print]45(8): 117755

SARS-CoV-2 ORF7a drives mitochondrial dysfunction via PDK4 activation and complex I inhibition.

Raúl Fernández-Rodríguez, Carmen M Soto-Jiménez, Rebeca Acín-Pérez, Ana de Lucas-Rius, Miguel Padilla-Blanco, Luz M Sánchez-Mendoza, Blanca D López-Ayllón, Ángela Peralbo-Molina, Eduardo Chicano-Gálvez, José M Villalba, José A Enríquez, María Montoya, Juan J Garrido, Tránsito García-García.

  Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection reprograms host metabolism to favor viral replication and immune evasion, yet the contribution of accessory proteins remains poorly defined. Here, we characterize the metabolic effects of the SARS-CoV-2 accessory protein ORF7a. Lentiviral expression of ORF7a in human lung epithelial (A549) and monocytic (THP1) cells, combined with integrated transcriptomic, proteomic, and metabolomic analyses, revealed marked dysregulation of glucose and lipid metabolism. ORF7a impaired mitochondrial oxidative phosphorylation, reducing basal and maximal respiration, inducing mitochondrial depolarization, and increasing reactive oxygen species. Mechanistically, ORF7a upregulated pyruvate dehydrogenase kinase 4 (PDK4), enhancing phosphorylation of the pyruvate dehydrogenase complex and suppressing pyruvate oxidation. However, pharmacological PDK4 inhibition failed to restore respiratory function. High-resolution respirometry identified complex I dysfunction, while Blue Native-PAGE revealed defective assembly of respiratory supercomplexes. Together, these findings demonstrate that ORF7a disrupts mitochondrial metabolism through enzymatic regulation and destabilization of the respiratory chain, highlighting mitochondria as a target of SARS-CoV-2-induced metabolic reprogramming.

Keywords:  CP: microbiology; ORF7a; SARS-CoV-2; complex I dysfunction; metabolic reprogramming; mitochondrial dysfunction; oxidative phosphorylation; respiratory chain supercomplexes

DOI:  https://doi.org/10.1016/j.celrep.2026.117755
J Cell Sci. 2026 Jul 15. pii: jcs264635. [Epub ahead of print]139(14):

Vimentin intermediate filaments support autophagosome biogenesis at ER-endosome contact sites in response to starvation.

Quentin Frenger, Dobrawa Amiri Czajkowski, Carla Alemany, Damiana Lecoeuche, Cédric Delevoye, Etienne Morel.

  Macroautophagy (autophagy) is a fundamental catabolic process requiring the biogenesis of the autophagosome to support cell survival during stress. Although the roles of F-actin and microtubule cytoskeleton in autophagy are well established, the contribution of intermediate filaments (IFs) remains poorly understood. Here, we investigated the role of the type III IF vimentin in supporting the early steps of starvation-induced autophagy. We demonstrate that starvation triggers a rapid, perinuclear compaction of vimentin IFs, which showed enhanced overlap with the endoplasmic reticulum (ER) and correlated with transient vimentin phosphorylation at serine 56. We reveal that autophagic proteins accumulate at the vimentin-ER interface, physically connecting the autophagosome biogenesis machinery to the vimentin IF network. Knockout or pharmacological perturbation of vimentin-IFs dynamics using withaferin-A significantly impairs starvation-induced autophagic flux. Mechanistically, we reveal that vimentin IFs are essential coordinators for the mobilization of endosome-ER membrane contact sites (EERCS), a crucial hub for autophagosome nucleation. Together, our findings uncover a novel role for vimentin IFs as a dynamic cytoskeletal coordinator that spatially organizes membrane contact sites to promote the efficient initiation of autophagosome biogenesis in response to nutrient stress.

Keywords:  Autophagosome; Autophagy; Endoplasmic reticulum; Intermediate filaments; Membrane contact sites; Vimentin

DOI:  https://doi.org/10.1242/jcs.264635
Oncogene. 2026 Jul 26.

The phase separation of ZC3H18 transcriptionally activates LDHA and forms lactylation-mediated positive feedback loop to promote tumorigenesis of lung cancer.

Dandan Yin, Chang Zhang, Yuancheng Li, Jiali Dai, Tianyu Qu, Jun Su, Xiyi Lu, Pingping Wu, Liang Han, Erbao Zhang.

RNA-binding proteins (RBPs) play crucial roles in tumorigenesis and cancer treatment. As metabolic reprogramming is known to participate in tumorigenesis, elucidation of the mechanisms of crosstalk between RBPs and metabolism could provide new insights into cancer biology. Here, we found that the RBP ZC3H18 is overexpressed in lung cancer through copy number gain, which exerts oncogenic functions. Mechanistically, ZC3H18 undergoes phase separation to transcriptionally activate a key metabolic enzyme, lactate dehydrogenase A (LDHA), by binding to the LDHA promoter, thus promoting glycolysis and the production of lactate. The accumulation of lactate, in turn, activates the transcription of ZC3H18 through histone H3K18 lactylation (H3K18la) and directly induces the lactylation of ZC3H18 at the Lys186 residue (K186) in post-translational, thus forming a positive ZC3H18/LDHA/lactate/ZC3H18 feedback loop. Moreover, the combination of ZC3H18 inhibition and an LDHA small-molecule inhibitor (GSK2837808A) exhibited better antitumor efficacy in lung cancer patient-derived xenograft (PDX) model, suggesting the therapeutic potential of targeting the ZC3H18/LDHA axis. Taken together, our findings clarify the dialogue between RBP phase separation and lactate metabolism from a novel perspective and suggest that the ZC3H18/LDHA axis may serve as a potential therapeutic target for lung cancer.

DOI: https://doi.org/10.1038/s41388-026-03817-6
bioRxiv. 2026 Jul 17. pii: 2026.07.15.737608. [Epub ahead of print]

A Role for Astrocyte Metabolism in Species-Specific Neuronal Development.

Sheila Steiner, Kaia Foster, Rebecca Chinn, Joshua Pratt, Sarah Fernandes, Amandeep Sharma, Renata Santos, Christian Metallo, Maria Carolina Marchetto, Fred H Gage.

Human neurons develop more slowly than non-human primate (NHP) neurons, a phenomenon called neoteny, but research has primarily focused on neuron-intrinsic drivers. We hoped to further elucidate any species-specific divergence in function and the astrocytes' role in influencing species-specific neurodevelopment rate. In this study, we identified a delayed onset of gliogenesis in human versus NHP organoid models. Transcriptomic and 13 C metabolic flux analyses of iPSC-derived astrocytes revealed distinct metabolic profiles: NHP astrocytes exhibit increased serine and glycine synthesis, whereas human astrocytes show elevated lactate secretion, suggesting a change in the metabolic role of astrocytes across primate evolution. We then assessed the impact of these different species' astrocytes on neuronal development. We observed an increase in electrophysiological maturation and a change in transcriptomic neuronal development trajectory in human neurons cultured with rhesus astrocyte conditioned media as opposed to human astrocyte conditioned media. Human astrocyte secretomes were enriched for synaptogenic and axon-growth proteins, which could indicate they play a greater role in supporting structural complexity and dendritic arborization over rapid maturation when compared to NHP astrocytes. Finally, chemical inhibition of PHGDH demonstrated that these changes in neuronal differentiation are partially mediated by the different metabolic roles that astrocytes play in humans versus NHPs. Collectively, our results reveal a cell-extrinsic role for astrocyte metabolism in shaping human-specific neurodevelopmental timing and trajectories.

DOI: https://doi.org/10.64898/2026.07.15.737608
Science. 2026 Jul 30. 393(6810): eads5397

An adaptor for feedback regulation of heme biosynthesis by a mitochondrial protease.

Thomas Cottle, Lydia Joh, Cori Posner, Adam DeCosta, Dean R Campagna, Mark D Fleming, Sarah Ducamp, Julia R Kardon.

Heme biosynthesis is tightly coordinated to support essential functions without accumulating toxic porphyrins and depleting cellular iron. Heme induces degradation of the heme biosynthetic enzyme, 5-aminolevulinate synthase (ALAS), by the mitochondrial caseinolytic protease complex CLPX-CLPP (CLPXP), but the mechanism for heme-triggered degradation had not been elucidated. We found that polymerase delta-interacting protein 2 (POLDIP2) is a heme-sensing adaptor protein sufficient to reconstitute negative feedback degradation of ALAS by CLPXP. POLDIP2 was necessary to support ALAS turnover in cells and regulate heme production during erythropoiesis. POLDIP2 directly recognized and recruited heme-bound ALAS to CLPXP. Degradation initiation required a carboxyl-terminal element of ALAS, truncations of which cause an erythropoietic protoporphyria. Our findings establish a mechanism for conditional degradation by CLPXP that underlies erythropoietic protoporphyrias linked to CLPX and ALAS.

DOI: https://doi.org/10.1126/science.ads5397
Biochim Biophys Acta Mol Cell Biol Lipids. 2026 Jul 27. pii: S1388-1981(26)00048-X. [Epub ahead of print] 159762

Futile cycles in metabolic flexibility: The energetic cost of regulatory precision.

Radhika Khandelwal, Lianggong Ding, Anand Kumar Sharma.

  Futile cycles (FCs), also known as substrate cycles, are a pair of opposing biochemical reactions that continually convert a substrate into a product and back. In doing so, FCs waste ATP without producing a tangible metabolic output (thus termed 'futile'). Because ATP hydrolysis is exothermic, recent studies have extensively focused on the thermogenic function of various FCs, particularly in adipose tissue. However, the function of FCs on other target organs and their primary biological functions remain poorly defined. In this forward-looking minireview/perspective, we discuss a few underexplored functions of FCs that underpin metabolic flexibility and systemic metabolic health. We propose an integrative model in which discrete FCs across metabolic organs act in concert to regulate cellular energetics and organismal metabolic physiology. We postulate that FCs sense and integrate metabolic status, redox balance, and metabolite signaling, with mitochondria serving as the central hub where energetic and signaling cues converge to generate a calibrated cellular response. Given the broad regulatory role of FCs, including in metabolic flexibility, future studies should aim to define the wider functions vis-à-vis metabolic homeostasis in health and disease.

Keywords:  Futile cycles; Lipid metabolism; Metabolic flexibility; Metabolic flux; Mitochondria; Thermogenesis

DOI:  https://doi.org/10.1016/j.bbalip.2026.159762
Proc Natl Acad Sci U S A. 2026 Aug 04. 123(31): e2606606123

Spatiotemporal control of Atg2 association with the ER during autophagosome formation.

Tetsuya Kotani, Haruki Tanabe, Shinri Kitta, Momoko Higashi, Tatsuya Niwa, Tatsuya Kaminishi, Chika Kakuta, Junko Shimasaki, Hidetaka Kosako, Tamotsu Yoshimori, Akiko Kuma, Hitoshi Nakatogawa.

  Autophagy degrades various intracellular components by sequestering them within membrane vesicles called autophagosomes and delivering them to lysosomes or vacuoles. Previous studies have revealed that the conserved, bridge-like lipid transfer protein Atg2 tethers autophagosome precursors to the endoplasmic reticulum (ER) and mediates lipid supply from the ER to drive their expansion into autophagosomes. However, how Atg2 docks onto the ER has remained unclear. Here, we show in Saccharomyces cerevisiae that Atg2 interacts with the ER-resident VAP family protein Scs2. This interaction is mediated by a phospho-FFAT motif in Atg2 and the major sperm protein domain of Scs2 and enhanced by phosphorylation of the motif by the autophagy-initiating kinase Atg1, which is activated at the autophagosome formation site upon autophagy induction. This interaction cooperates with the N-terminal region of Atg2, which contains a weakly amphipathic helix, to mediate Atg2 association with the ER. Thus, the Atg2-Scs2 interaction functions as a spatiotemporal switch that controls Atg2-ER association. We also show that mammalian ATG2 interacts with the VAP-like proteins MOSPD1 and MOSPD3 to promote autophagosome formation. Collectively, this study reveals a conserved mechanism that initiates lipid transfer during autophagosome formation.

Keywords:  Atg2; VAP protein; autophagy; lipid transfer protein; phospho-FFAT motif

DOI:  https://doi.org/10.1073/pnas.2606606123
J Vis Exp. 2026 Jul 07.

Demonstrating Fluorescent Peptidyl Inhibitor Targeting of Mitochondrial ClpXP by Fluorescence Microscopy in Mammalian Cells.

Zhou Sha, Stephen Benkovic, Irene Lee.

Mitochondrial ATP-dependent proteases are essential for maintaining protein homeostasis through degradation of damaged or misfolded proteins. Among these, the ClpXP protease complex locates in mitochondrial matrix and contributes to mitochondrial quality control under physiological and stress conditions. This work demonstrates a quantitative fluorescence microscopy workflow to assess mitochondrial targeting of the fluorescent peptidyl inhibitor FAM-FAPAL-CMK and evaluate mitochondrial morphological changes associated with ClpXP inhibition in mammalian cells. HeLa cells were treated with FAM-FAPAL-CMK and analyzed using confocal microscopy combined with immunofluorescence staining of mitochondrial markers and quantitative image analysis. Colocalization analysis using Costes thresholding and Manders' overlap coefficients demonstrated mitochondrial enrichments of the inhibitor signal. As a consequence, inhibition of ClpP altered mitochondrial morphology. Immunoblot analysis showed no significant change in ClpP protein abundance upon inhibitor treatment. Taken together, this work describes a reproducible imaging-based workflow that will enable interrogation of mitochondrial ClpXP functions in intact cells in response to perturbations of homeostasis, such as oxidative stress.

DOI: https://doi.org/10.3791/72089
Sci Adv. 2026 Jul 31. 12(31): eaef0140

Mitochondrial control of amino acid catabolism by a fasting-inducible mitochondrial carrier.

Satoshi Oikawa, Tadashi Yamamuro, Hiroshi Nishida, Daisuke Katoh, Dandan Wang, Masanori Fujimoto, Shingo Kajimura.

Metabolic adaptation to nutrient deprivation requires coordinated control of mitochondrial anaplerosis and cataplerosis; however, how metabolite flux across the mitochondrial membrane is regulated during fasting remains less defined. Here, we report SLC25A34 as a fasting-inducible mitochondrial carrier that is highly expressed in oxidative skeletal muscle. Using bacterial reconstitution, proteo-liposomes, and tracer studies, we showed that SLC25A34 mediates the import of phosphoenolpyruvate (PEP) into the mitochondrial matrix. Loss of SLC25A34 impaired glutamine-supported anaplerosis under nutrient-deprived conditions, while glucose and pyruvate utilization remained largely intact. Muscle-specific deletion of Slc25a34 resulted in reduced fasting-induced amino acid catabolism and the accumulation of amino acids, leading to activation of mTORC1 signaling even under fasted conditions. Consequently, SLC25A34-deficient soleus muscle exhibited hypertrophy and myopathic features, accompanied by mTORC1-dependent increase in protein synthesis. Together, these results highlight a unique biological role for the inducible mitochondrial carrier SLC25A34, which couples PEP import to amino acid catabolism and proteostasis to preserve skeletal muscle integrity in response to metabolic stress.

DOI: https://doi.org/10.1126/sciadv.aef0140
J Biol Chem. 2026 Jul 30. pii: S0021-9258(26)02253-2. [Epub ahead of print] 113381

Sterol Flux Rewiring: Cholesterol Biosynthesis as a Dynamic Signaling Network.

Marc Poirot, Philippe de Médina, Sandrine Silvente-Poirot.

  Cholesterol biosynthesis is among the best-characterized metabolic pathways in biology, yet a fundamental question remains unresolved: why does this pathway generate more than twenty enzymatic reactions and numerous structurally distinct intermediates if cholesterol is its major biological end product? Over the past several decades, biochemical, genetic, pharmacological, biophysical, and lipidomic studies have progressively revealed that many sterol intermediates are not merely transient precursors. Instead, they possess distinct biophysical, signaling, and oxidative properties that contribute directly to cellular physiology and disease. However, these discoveries have largely been interpreted within separate biological and experimental contexts, including inherited disorders of cholesterol biosynthesis, membrane biology, nuclear receptor signaling, oxysterol metabolism, and pharmacological inhibition of distal sterol enzymes. Here, we propose that sterol flux rewiring provides an integrative framework that connects these independent observations into a unified view of cholesterol metabolism. In this framework, biological responses emerge from dynamic redistribution of metabolic flux, generating distinct sterol states characterized by specific membrane properties, signaling activities, oxidative potentials, and downstream metabolic outputs rather than by the accumulation of individual metabolites alone. This perspective explains how changes in sterol composition reshape membrane organization, oxidative diversification, and interconnected signaling networks, including the epoxycholestanoid pathway. It also provides a coherent framework for understanding how alterations in cholesterol metabolism contribute to development, immunity, neurobiology, ageing, regeneration, and cancer, while highlighting new opportunities for therapeutic strategies aimed at reprogramming sterol-state organization rather than simply inhibiting cholesterol synthesis.

Keywords:  Cancer metabolism; Cholesterol biosynthesis; EChA; oxysterols; sterol flux rewiring; sterol metabolism

DOI:  https://doi.org/10.1016/j.jbc.2026.113381
bioRxiv. 2026 Jul 13. pii: 2026.07.10.737826. [Epub ahead of print]

Transsulfuration links aspartate-asparagine metabolism and redox homeo-stasis to drive tumor growth.

Mirko Milosevic, Kristina Dmytruk, Ahmad Alghadi, Pavel Jakoube, Julian Wong Soon, Petra Hyrossova, Muhammad Bin Munim, Sara Isabel Fernandes, Anna Shevzov-Zebrun, Robert Stanko, Isidora Mitric, Zuzana Cockova, Lukas Kucera, Juan Fernández-García, Ales Benda, Bryan Marzullo, Radislav Sedlacek, Jiri Neuzil, Sarah-Maria Fendt, Daniel A Tennant, Matthew G Vander Heiden, Katerina Rohlenova, Jakub Rohlena.

Cytosolic redox balance is tightly coupled to aspartate synthesis through the malate-aspartate shuttle, and limiting the malate-aspartate shuttle has been proposed to constrain tumor growth by restricting aspartate availability. Here we show that tumors derived from cancer cells lacking GOT1 and GOT2, the cytosolic and mitochondrial aspartate aminotransferases essential for as-partate production and malate-aspartate shuttle function, grow despite impaired canonical as-partate synthesis. This is because cytosolic redox state, not aspartate supply, is the primary metabolic bottleneck in GOT1/GOT2 knockout cells. Using single-cell transcriptomics, metabo-lite tracing, and a loss-of-function CRISPR screen, we find that these tumors engage an adaptive bypass in which availability of asparagine, a product of aspartate, enables serine- and methio-nine-dependent transsulfuration to generate α-ketobutyrate, whose reduction regenerates cy-tosolic NAD⁺ and restores redox homeostasis. Pharmacological inhibition or genetic ablation of transsulfuration abrogates this asparagine-driven rescue. These findings define asparagine as a regulator of cytosolic NAD⁺/NADH balance and reveal a link between amino acid metabolism and redox control that suggests transsulfuration as a targetable vulnerability in tumor redox maintenance.
Significance statement: Aspartate synthesis and cytosolic redox balance are both coupled through the malate-aspartate shuttle. We show that the cytosolic NAD⁺/NADH ratio, not aspartate supply, is a critical output of the malate-aspartate shuttle for tumor growth. Availability of asparagine, a product of aspar-tate, enables serine- and methionine-dependent transsulfuration to restore cytosolic NAD⁺/NADH balance, proliferation and tumor growth independently of canonical aspartate pro-duction by the malate-aspartate shuttle. This defines asparagine as a regulator of cytosolic re-dox and identifies transsulfuration as a targetable vulnerability in tumor redox maintenance.

DOI: https://doi.org/10.64898/2026.07.10.737826
PLoS One. 2026 ;21(7): e0345843

Mapping the chaperonin TRiC/CCT interactome in mouse photoreceptors reveals functional significance for energy metabolism.

Celine Brooks, David Salcedo-Tacuma, Isabella Mascari, Mark Eminhizer, Tuan Ngo, Douglas Kolson, Emily Sechrest, Tongju Guan, Neil Billington, Wen-Tao Deng, David Smith, Jianhai Du, Nikolai Skiba, Maxim Sokolov.

The eukaryotic chaperonin TRiC/CCT is essential for folding a diverse set of proteins, yet its interactome and functional roles in specialized neurons remain incompletely understood. To investigate TRiC-mediated folding in rod photoreceptors, we generated a transgenic mouse line expressing an epitope-tagged Tcp-1α subunit, enabling purification of intact TRiC complexes from retinal tissue. Mass spectrometry identified 226 TRiC-interacting proteins, including known TRiC substrates and co-chaperones as well as numerous novel candidates enriched in RNA processing, cytoskeletal organization, and cell-cycle regulation. Using a TRiC loss-of-function model in which expression of a short splice isoform of phosducin-like protein (PhLPs) competitively inhibits TRiC activity, we observed marked reductions in canonical TRiC substrates, including tubulins, transducin β subunits, and triosephosphate isomerase, as well as secondary alterations in proteins involved in cytoskeletal stability, membrane trafficking, energy metabolism, and phototransduction. Quantitative metabolomic profiling revealed that TRiC deficiency induces a metabolic "energy crisis" characterized by reduced glycolytic- and tricarboxylic acid cycle intermediates, acylcarnitines, ATP, NAD, and NADH, implicating widespread impairment of glucose utilization, mitochondrial bioenergetics, and fatty acid oxidation. Integrative proteomic-metabolomic analysis identified a small subset of proteins, including Rab10 and Anxa1, as potential drivers of these metabolic disruptions, with defective Rab10-dependent GLUT4 trafficking emerging as a plausible mechanism underlying impaired glucose uptake in TRiC-deficient rods. Finally, experiments using a perpetually unfolded Gβ1 mutant and Gγ1-knockout mice demonstrated that substrate overload sequesters TRiC and competitively displaces other clients, exacerbating proteostasis imbalance. Together, our study provides a comprehensive in vivo mapping of the TRiC interactome in mammalian rods, reveals a connection between TRiC-dependent proteostasis and energy metabolism in rods, and indicates a mechanism by which misfolded TRiC substrates exacerbate a proteostasis imbalance that ultimately results in neurodegeneration.

DOI: https://doi.org/10.1371/journal.pone.0345843