EMBO Reports

Lipid droplets (LDs) are unique organelles, surrounded by a phospholipid monolayer. They are present in most eukaryotic cells including the unicellular model organism S. cerevisiae. LDs store neutral lipids which serve as precursors for amphipathic membrane lipids and as an energy reserve. Loss of LDs in S. cerevisiae results in multiple cellular defects impairing lipid homeostasis and the biogenesis and function of other organelles. Here, we find that the expression levels of many proteins in isolated mitochondrial fractions are altered in cells that cannot synthesize neutral lipids and therefore lack LDs. In addition, among several downregulated proteins, we identified the previously uncharacterized Ylr001c (which we name Vlf1 for Vacuolar Lipophagy Factor 1). We show that Vlf1 is glycosylated and, in contrast to some previous reports, is actually localized to the vacuole. Furthermore, we demonstrate that changes in Vlf1 expression alter growth sensitivity to rapamycin, and detected a physical interaction of Vlf1 with Atg15, a lipase involved in autophagy. Additionally, we observe higher levels of autophagy/lipophagy in the absence of Vlf1 and a reduction upon overexpression of the protein. Taken together, the effects on lipohagy by Vlf1 makes it, according to our knowledge, the first vacuolar lipophagy regulator identified in S. cerevisiae.

Kinesins are microtubule-dependent motors, yet the functions of the kinesin-4 family member KIF27 remain poorly understood. Here, we demonstrate a dynamic and cell-cycle-dependent localization of KIF27, consistent with its functional roles in mitotic progression. Upon mitotic entry, KIF27 relocates to condensed chromosomes. During anaphase, a fraction of KIF27 accumulates at the spindle midzone, and in telophase and late stages of cytokinesis it localizes at the midbody, colocalizing with key cytokinetic regulators at both structures. Recruitment of KIF27 to the midbody depends on KIF23 and CEP55. KIF27 depletion results in profound cell division defects, altered midbody and microtubule morphology, delayed cytokinesis and cytokinesis failure. Beyond cell division, KIF27 depletion directly compromises nuclear morphology, and pan-cancer transcriptomic analyses correlate low KIF27 expression with aneuploidy and poor patient survival in several cancer types. Together, our results identify KIF27 as a novel regulator of mitotic fidelity and genome stability.

Life on earth has always been exposed to the fluctuating Earth's magnetic field, but a magnetic sense affecting behavior has been debated for mammals. We here report that mice, kept under constant laboratory conditions, showed fluctuations in spontaneous behavioral activity with a periodicity of ~14 and ~28 days. This was confirmed in nine cohorts from four facilities on two continents, covering 3 to 41 months. Such oscillations were also maintained in brain Bmal1 knockout mice lacking circadian rhythms, suggesting independence of the circadian clock. The behavioral activity peaked around full and new Moon, and showed a strong alignment with the periodic geomagnetic fluctuations originating in the Earth's iono- and magnetosphere that are modulated by solar rotation and the orbital motion of the Moon. In the ultradian range, this alignment persisted in CRY1/2 knockout mice, suggesting that solar-lunar-driven geomagnetic fluctuations can modulate behavior rhythms independently of CRY1/2.

Macroautophagy is a conserved catabolic process that facilitates the degradation of cellular material by capturing it in double membrane vesicles termed autophagosomes. In Saccharomyces cerevisiae, selective macroautophagy is initiated by the scaffolding protein Atg11. Atg11 recruits the transmembrane protein Atg9, which resides in small vesicles, to autophagic cargo. Atg9 vesicles then fuse, forming the initial membrane sheet that expands into the autophagosomal membrane. While it is known that Atg9 interacts with Atg11 via a set of hydrophobic amino acids in the disordered N-terminus of Atg9, it is unclear how Atg11 mediates this interaction. To gain insight into this unknown aspect of autophagy initiation we utilized a combination of biochemical, structural, and cellular approaches. We demonstrate that the N-terminal domain (NTD) of Atg11 is the primary interaction site for Atg9, but the NTD requires clustering by the C-terminal region of Atg11 for its complete interaction with Atg9. We investigated the structure of the Atg11-NTD using cryo-EM which, in combination with AlphaFold modeling, revealed a positively charged binding pocket within the Atg11-NTD that is essential for Atg9 binding. Mutation of this conserved binding pocket leads to a loss of Atg9 binding in yeast and a reduction in the selective autophagy of mitochondria. Taken together, our results demonstrate the mechanism by which Atg11 recruits Atg9 to autophagy initiation sites.

Animal cells respond to hypoxic stress through cell-autonomous stabilization of HIF-1, a conserved transcription factor that mediates adaptation to low-oxygen environments. Although HIF-1 is essential for viability under hypoxia, its persistent activation during development causes miswiring defects in the nervous system, raising the question of how developing neurons balance the pro-survival benefits of HIF-1 stabilization against these associated risks. Here we show that C. elegans neurons address this challenge by mobilizing an internal promoter within the hif-1 locus to generate a dominant-negative isoform, HIF-1c, which acts in the nucleus to limit HIF-1/AHA-1 heterodimer formation. This buffering mechanism supports proper neuronal migration, axon guidance, and circuit formation and its loss phenocopies the defects seen when the ubiquitous HIF-1 degradation pathway is disrupted, confirming that HIF-1c serves as a critical layer of protection for the developing nervous system against hypoxic-induced errors. Lastly, we identify the retinoblastoma protein LIN-35 as a modulator of HIF-1 signaling in worms via control of hif-1c expression. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=162 SRC="FIGDIR/small/745244v1_ufig1.gif" ALT="Figure 1"> View larger version (40K): org.highwire.dtl.DTLVardef@3ad347org.highwire.dtl.DTLVardef@4fd4forg.highwire.dtl.DTLVardef@1928804org.highwire.dtl.DTLVardef@11fd1e1_HPS_FORMAT_FIGEXP M_FIG C_FIG

Oxygen is indispensable for survival in aerobic organisms, necessitating mechanisms to sense and respond to fluctuations in oxygen availability. Physiological processes such as early development, proceeds in an oxygen-sensitive environment and this appears conserved across vertebrate evolution. Owing to their avascular nature epithelial tissues routinely experience hypoxia but the epithelial responses to hypoxia and the underlying adaptive molecular regulation remains to be fully understood. We used the bilayered epidermis of Zebrafish embryos to ask how a developing epithelium responds to and copes with hypoxia. We show that under hypoxic conditions, despite the changes in cell morphologies, disruption in E-cadherin polarisation and the presence of intercellular gaps in the outer epidermal layer, the tight junctions are maintained. Our data indicate that ROCK (Rho-associated kinase) mediates the change in cell morphology and the maintenance of barrier function via non-muscle Myosin-II (NM-II). Furthermore, a high level of NM-II activity is essential to suppress Crb3-dependent cell delamination and apoptosis under hypoxia. Genetic perturbations reveal that neither increasing levels of active NMII nor augmenting tight junctions alone improves barrier function defects, indicating both these ROCK-dependent processes are necessary to maintain the barrier function under hypoxia. Our study uncovers the hitherto unappreciated importance of ROCK signaling in the maintenance of epithelial architecture and barrier function in a developing epithelium, ensuring organism survival.

Faithful inheritance of DNA methylation contributes to the memory of epigenetic states and protects against disease. While the mechanisms underlying DNA methylation maintenance at replication forks are well characterized, whether and how DNA methylation is altered or maintained at sites of DNA damage repair is still poorly understood. Here, by exploiting sequencing, imaging and proteomic approaches in mammalian cells exposed to UV radiation, we show that the majority of DNA methylation marks are maintained during UV damage repair and we dissect the molecular machinery involved in DNA methylation control. We detect the recruitment to sites of repair synthesis of the DNMT1 and DNMT3A DNA methylating enzymes, driven by the DNMT1 cofactor UHRF1 and by UV damage repair endonucleases. We also uncover a crosstalk with histone dynamics, whereby newly deposited H3.3 histones at UV damage sites promote the recruitment of DNMT1. Functionally, we reveal the importance of the DNA methylation maintenance machinery for the transcriptional response to UV damage and sustained cell proliferation. This work provides a comprehensive picture of DNA methylation control mechanisms following DNA damage, with important implications for our understanding of human diseases with an altered methylome.

Organelle membranes employ diverse lipids to relay key signals for efficient coordination of cellular processes. Diacylglycerol (DAG) is a simple yet critical lipid secondary messenger, but the regulatory mechanisms and functional implications for its distribution remain poorly understood. We have recently shown that Protein Kinase C (Pkc1) activation is driven by selective DAGs (C36:0, C36:1), whose levels are governed by Disco-interacting protein 2 (Dip2) (Shambhavi et al., 2025). Here, through genetic, chemical, and lipidomic screens, we show that the absence of Dip2 leads to specific DAG accumulation on the mitochondrial membrane and impacts its morphology, function, and quality control in yeast. Remarkably, the elevated DAGs in{Delta} dip2 promote translocation of Pkc1 to mitochondria via its DAG-binding C1 domain, but not the HR1 domain, suggesting functional partitioning between the regulatory domains. We also show that only specific DAGs, not the bulk DAGs, are required for Pkc1s targeting and inactivating Phospholipase C (Plc1) restores Pkc1 localisation and the associated mitochondrial defects. In addition, we identify that respiratory growth triggers specific DAG (C36:1) accumulation in the mitochondria, thereby promoting Pkc1 recruitment. Furthermore, we establish that the Psi1-Plc1-Dip2 axis is required for survival under respiratory growth conditions. Taken together, our study uncovers a novel, Dip2-mediated, unconventional Pkc1 signalling axis for maintaining mitochondrial homeostasis under nutrient transition and highlights how distinct lipid fingerprints enable precise control over organellar homeostasis.

The microtubule plus-end tracking proteins (+TIPs) CLIP-170/Bik1 and EB/Bim1 form a condensate, the +TIP body, at the plus-end of most microtubules in vivo. Remarkably, however, these +TIP bodies typically impart different dynamics and interaction profiles to distinct microtubules, according to their cellular function. The molecular mechanisms underlying the functional versatility of the +TIP body are unknown. Here, we show that the +TIP Kar9 utilizes repeats of a lysine-aspartate-lysine (KDK)-centered short linear motif (SLiM) to interact with Bik1 on a restricted subset of cytoplasmic microtubules during yeast mitosis. Furthermore, these multivalent Kar9-Bik1 interactions tune the material behavior of the +TIP body to specify proper microtubule function. Indicating that KDK serves as generic Bik1-interaction motif, similar motifs are also present in Kip2, where they mediate Bik1-dependent recruitment of Kip2 to the +TIP body. Together, our study provides insights into how low-affinity Bik1 interactors diversify microtubule function by locally specializing the content and behavior of +TIP bodies.

Vacuolar ATPases (V-ATPases) are highly conserved multi-subunit proton pumps that drive the acidification of intracellular vesicles, especially endosomes and lysosomes. By regulating progressive acidification of the endolysosomal pathway, V-ATPase activity impacts signaling transduction pathways both positively (e.g., internalization and activation of receptor-ligand complexes in endosomes) and negatively (e.g., degradation of pathway mediators in lysosomes). While the role of V-ATPases in human neurodegenerative diseases and cancer has been extensively studied, the requirement for these proteins in intestinal restitution remains poorly understood. Here, we use Drosophila to study the role of V-ATPases in regulating intestinal-injury and repair driven by excessive oxidative stress. We find that RNAi driven depletion of multiple subunits of the V-ATPase complex suppressed oxidative stress-induced lethality. By contrast, depletion of the main lysosomal catabolic enzyme in Drosophila (Cathepsin-D) had no effect. On a cellular level, these effects map to absorptive enterocytes (ECs) of the Drosophila intestine. Molecular analysis of intestines following injury by oxidative stress compared to uninjured controls reveals increased cell death, increased JNK-pathway activity, and increased IMD/NF-{kappa}B pathway signaling reporter expression compared to uninjured controls. Depletion of Vha44 (subunit C of the V1 complex) was sufficient to suppress the increased cell death, JNK pathway, and IMD/NF-{kappa}B pathway markers induced by oxidative stress in the intestine. Furthermore, overexpression of the MAP3K TAK1 enhanced death, JNK pathway and IMD/NF-{kappa}B pathway activation in a Vha44 dependent manner. These findings suggest that inhibition of V-ATPase activity can protect against intestinal injury caused by excessive oxidative stress. On a molecular level, we find that attenuation of endolysosomal acidification dampens pro-apoptotic JNK and IMD/NF-{kappa}B pathways, highlighting endosomal acidification as a potential amplifier of excessive oxidative stress.

Ataxia with oculomotor apraxia type 2 (AOA2) is a rare neurodegenerative disease caused by loss-of-function mutations in Senataxin, which encodes an RNA:DNA helicase. Many studies on Senataxin loss focus on its putative roles in regulating transcription and RNA transcript localization. However, several phenotypes remain underexplored, including metabolic dysregulation associated with ataxias. Using Senataxin-deficient mouse cells, we observed increased nuclear and genomic instability, as well as innate immune activation via the cGAS-STING axis. We also observed elevated ROS levels, decreased mitochondrial function, and hyperfused mitochondria. Importantly, mitochondrial dysfunction depends on cGAS/STING activity, indicating that the two phenotypes are functionally connected. Senataxin-deficient mice and AOA2 patient cells similarly exhibit spontaneous innate immune activation, and AOA2 patient cells also show decreased mitochondrial function. Our work identifies a previously unseen phenotype for AOA2 in which loss of Senataxin results in mitochondrial dysfunction promoted by cGAS and STING. SummaryThis study demonstrates a previously unidentified phenotype in AOA2 and Senataxin research in which cGAS-STING promotes mitochondrial dysregulation in Setx-/- MEFs. Further, these innate immune activation and mitochondrial dysregulated phenotypes are recapitulated in AOA2 patient cells.

Cell proliferation and fate specification are fundamental processes that ensure the generation of organs with proper size and patterning. Oxidative stress caused by accumulation of reactive oxygen species (ROS) can lead to cell cycle arrest, senescence, cell death and cell fate misspecification, thereby impairing normal development and contributing to many pathological processes. In this study, we identify Drosophila Ciz1 as a critical factor that safeguards epithelial homeostasis and development by preventing oxidative stress. Knockdown of Ciz1 in the Drosophila wing imaginal disc, an epithelial tissue that serves as the larval precursor of the adult wing, results in a small wing phenotype accompanied by thickened and ectopic veins. We further demonstrate that reduced Ciz1 expression leads to accumulation of donut-shaped mitochondria and elevated ROS levels. The increased oxidative stress subsequently suppresses proliferation via activation of JNK and promotes excessive vein formation by upregulating Rhomboid, a positive regulator of EGFR signaling. Interestingly, although Ciz1 is a zinc finger protein that predominantly localizes to the nucleus, neither its zinc finger motifs nor its nuclear localization is required for suppression of oxidative stress. Instead, the prion-like domain in its N-terminal part is essential for this activity. Our work identifies Ciz1 as an important factor in preventing oxidative stress and maintaining epithelial homeostasis.

Tumors exploit wound healing pathways not only to foster progression but also to lethally disrupt systemic physiology. A prominent example is malignant activation of the clotting cascade, causing pathology through unclear mechanisms that extend beyond thrombosis. Here we show that tumors in a coagulopathy-inducing Drosophila cancer model remotely disrupt intestinal stem cell (ISC) homeostasis. This paraneoplastic, tumor-gut communication axis induces intestinal dysplasia and barrier dysfunction, mimicking remote chronic injury that we show activates inflammation in ISCs via EGFR signaling. Unlike the interorgan responses observed with acute injury, which involves Jak/STAT signaling to activate regenerative ISC proliferation, dysregulated division in both tumor-bearing and chronically injured flies is sustained only by EGFR activation. We also present evidence that deposition of clot material locally onto gut stroma links tumor-driven coagulopathy to intestinal inflammation. Collectively, these findings distinguish mechanisms of remote responses to chronic versus transient stresses. Furthermore, they show how tumor-initiated, dysregulated wound healing programs can drive tissue-specific, pathological inflammation in a host.

The mitochondrial contact site and cristae organizing system (MICOS) is a multiprotein complex that shapes crista junctions and maintains inner and outer membrane contacts. MICOS coordinates the assembly of electron transport chain complexes, a prerequisite for cellular respiration. Indeed, MICOS is lost in eukaryotes that dispensed with cellular respiration, suggesting that its assembly depends on the presence of an active respiratory chain. Trypanosoma brucei provides a unique system to test this hypothesis as its mitochondrion undergoes developmentally regulated remodeling. In the insect stage, the mitochondrion contains cristae with an active electron transport chain, whereas the mammalian bloodstream form possesses precursor cristae with stub-like morphology that lack respiratory activity. MICOS has been characterized in the insect stage but remains unexamined in the bloodstream form. Here, we demonstrate that all MICOS subunits assemble onto precursor cristae, retaining conserved interactions with both outer and inner membrane protein machineries. This is somewhat unexpected given the co-occurrence of MICOS with active cellular respiration in nature. Furthermore, we identify novel MICOS-associated proteins that are dispensable for its stability, suggesting auxiliary rather than core roles in MICOS function. Together, our findings establish that MICOS assembly precedes cellular respiratory competence and expand its interaction landscape in trypanosomatids.

Api5 is elevated in a number of cancers and is associated with many hallmarks of cancer, including resistance to apoptosis, immune escape, stemness, chemotherapy resistance, high proliferation, and cell-cycle dysregulation. In this study, we identified the DNA and chromatin-binding activities of Api5 in tumorigenic cells, as well as its association with genomic instability and chemotherapy resistance. Knockdown of Api5 resulted in reduced nuclear volume, DNA content, and chromosome number, and increased sensitivity to DNA damage. The survival of Api5-knockdown cells decreased following UV and cisplatin treatments due to the accumulation of damaged DNA and inefficient nucleotide excision repair. Interestingly, Api5 knockdown cells also exhibited low pChk1 levels following UV damage. Further, we confirmed the chemotherapy resistance phenotype in cancers with elevated Api5 levels, demonstrating that xenograft tumours with Api5 knockdown responded better to cisplatin, with significant tumour regression. SummaryApoptosis inhibitor 5 (Api5) contributes to chemotherapy resistance by conferring a survival advantage and promoting efficient DNA repair following genotoxic stress through regulation of Chk1 activation.

Programmed cell death is essential for organismal development. When dysregulated, it leads to neurodegenerative diseases and cancer. Although apoptotic pathways are well studied, the role of mitochondrial import translocases in regulating cell death remains unclear. Our study reveals a unique apoptotic pathway controlled by the TIM22 complex, an inner mitochondrial membrane translocase. This pathway involves a multiprotein complex formed by Tim22 and Nde1, a part of the respiratory electron transport chain. Under stress, the cytosol-exposed Nde1 isoform, a pro-apoptotic factor, is stabilised by the TIM22 complex, which includes the Tim18 subunit and Tim22s transmembrane segments. Notably, impairing the TIM22 complex and deleting Nde1 suppresses apoptosis and restores mitochondrial health. Beyond its role in import, our study uncovers a moonlighting function of the TIM22 complex in regulating mitochondria-dependent apoptotic cell death.

Ribosomal protein paralogs are increasingly implicated in the regulation of cellular metabolism and mitochondrial function. However, the mechanisms linking paralog composition of ribosomes to mitochondrial physiology remain largely unclear. Here, we investigate the two Rpl40 paralogs in the budding yeast Saccharomyces cerevisiae and find that deletion of either paralog induces compensatory upregulation of the remaining gene and causes mild mitochondrial stress. Despite this shared phenotype, the mutants display distinct mitochondrial adaptations. Loss of Rpl40a is accompanied by increased abundance of mitochondrial proteins, including MICOS components, whereas loss of Rpl40b leads to reduced levels of mitochondrial inner membrane proteins, including the translocase Tim22 and carrier proteins, together with increased sensitivity to membrane stress. Notably, the two mutants show opposing changes in triglyceride abundance, pointing to paralog-specific control of lipid metabolic remodeling during mitochondrial stress. These findings suggest that Rpl40 paralogs differentially modulate cellular adaptation to mitochondrial stress, linking ribosome composition to mitochondrial proteostasis and lipid homeostasis.

Primary cilium-dependent Hedgehog signalling is essential for embryonic development, tissue patterning, and organ homeostasis, and its disruption causes a spectrum of developmental disorders collectively termed ciliopathies. Whether environmental toxicants can chemically induce ciliopathy-like states by targeting this pathway, however, remains poorly understood. Here we show that endosulfan, a banned organochlorine pesticide epidemiologically linked to severe congenital and reproductive defects in exposed human populations, disrupts Hedgehog signalling by driving GLI transcription factor processing into repressor forms and suppressing target gene expression at both transcriptional and protein levels. Having excluded direct effects on core ciliary receptors and GLI-DNA binding, we identify the pathway kinases PKA and GSK3{beta} as direct targets of endosulfan: endosulfan increases PKA activity through allosteric fine-tuning, and -- in a pharmacologically rare finding -- acts as the first reported small-molecule activator of GSK3{beta}, shifting the kinase toward a catalytically active conformation. We further identify Cetn3 and Cep250 as novel GLI-regulated genes required for centriole cohesion, both of which are repressed upon endosulfan exposure, providing a mechanistic link to the reproductive defects reported in exposed populations and animal models. These findings identify endosulfan as a candidate chemical inducer of ciliopathy and reveal how an environmental toxicant can hijack core kinase signalling to disrupt Hedgehog-dependent development.

Rubicon is a negative regulator of autophagy and the endolysosomal network (ELN) and an antagonist of the class III phosphatidylinositol 3-kinase complex II (PI3KC3-C2). Inhibition of Rubicon is considered a potential means to therapeutically upregulate autophagy and the ELN to treat Parkinsons disease and other conditions characterized by autophagic and ELN dysfunction. Rubicon is specific for the UVRAG-containing PI3KC3-C2 over the purely autophagic ATG14- containing PI3KC3-C1 complex. Here, we determined the high-resolution cryo-electron microscopy structure of PI3KC3-C2 in complex with the PI3KC3-binding domain (PIKBD) of Rubicon and compared it to cryo-EM structures of unbound PI3KC3-C2 and PI3KC3-C1. Rubicon binds directly to PI3KC3-C2 only via the BARA domain of the BECN1 subunit, which is common to both C1 and C2. The selectivity of Rubicon for the PI3KC3-C2 complex over the PI3KC3-C1 complex is attributed to a conformation of the BECN1BARA domain induced by UVRAG, rather than to direct contact with UVRAG or direct antagonism by the ATG14 subunit of PI3KC3-C1. Targeted disruption of the Rubicon:PI3K3-C2 structural interface by site-directed mutations enhances mitophagic activity in human epithelial cells to levels comparable to those observed in Rubicon knockout (KO) cells. Similarly, disruption of the interaction in Rubicon-overexpressing hippocampal neurons restored lysosomal flux to wild-type levels. These data show that suppressing the function of PI3K3- C2 can fully account for the negative regulatory effects of Rubicon in the autophagy and ELN pathways. Significance StatementEndolysosome maturation and autophagosome-lysosome fusion require the production of phosphatidylinositol 3-phosphate (PI(3)P) by the class III phosphatidylinositol 3-kinase complex II (PI3KC3-C2). Rubicon is a key negative regulator of endolysosomes and autophagy that suppresses PI3KC3-C2 activity. Here, we reveal in atomistic detail how Rubicon selectively recognizes PI3KC3-C2. Disrupting the Rubicon-PI3KC3-C2 interaction restores mitophagy and enhances lysosomal activity to the same extent as Rubicon gene deletion, establishing that PI3KC3-C2 inhibition fully accounts for the biological regulatory effects of Rubicon in the autophagy and lysosome pathways.

MTCH2 (mitochondrial carrier homolog 2) is a noncanonical member of the solute carrier family with five transmembrane (TM) helices, localized to the mitochondrial outer membrane. MTCH2's atypical topology creates a membrane-accessible hydrophilic groove, predicted to be necessary for its protein insertase and lipid scramblase activities. MTCH2 is linked to lipid metabolism and obesity and is required for starvation-induced mitochondrial hyperfusion. Here, we show that MTCH2 is a stable component of a complex containing the Armadillo (ARM) repeat-containing protein, ARMC1, and the DnaJ/Hsp40 chaperone protein, DNAJC11. Protein crosslinking, protein structural modeling, and molecular dynamics simulations demonstrate that the ARMC1 alpha-helical C-terminal domain (CTD) inserts into and stably interacts with the MTCH2 hydrophilic groove and blocks its lipid scramblase activity. We observe that starvation-induced mitochondrial fatty acid oxidation (FAO) is negatively regulated by the ARMC1-MTCH2 interaction. In ARMC1-deficient cells, FAO is stimulated compared to wild-type cells and lipid droplet abundance is significantly reduced. The altered lipid phenotype of ARMC1-/- cells is strictly dependent on MTCH2 and is reversed by ARMC1 expression in a manner dependent on its CTD. Beyond this metabolic axis, we also identify a function for ARMC1 in regulating lysosomal distribution and autophagic flux that is independent of its CTD and interaction with MTCH2. Thus, our data support a model in which the MTCH2-ARMC1 interaction functions as a metabolic switch during starvation to regulate the balance between fat storage and fat burning.