Biology subjects

Budin, I.

Publications and source records attributed to Budin, I..

At least 19 recordsLinked to original sources

bioRxiv2026

Energetics of stalk intermediates elucidated from hydrostatic pressure effects on membrane fusion

Membrane fusion is an essential process in cells that requires a balance of lipid composition to establish biophysical properties conducive to topology changes. During fusion, lipids of opposing membranes must invert and overcome energy barriers associated with forming highly curved stalk and pore intermediates. While theoretical work has modelled the effect of lipid intrinsic curvature on stalk formation, quantifying the relationship experimentally has proven to be a challenge due to the inability to vary lipid curvature without concomitantly changing other properties that affect fusion. Here we address this hurdle by using hydrostatic pressure to modulate lipid intrinsic curvature independently of chemical composition. Using high-pressure stopped-flow fluorimetry, we measured rates of calcium-mediated lipid mixing between populations of vesicles, a process that is strongly inhibited by pressure. We correlated mean lipid intrinsic curvature across pressure with lipid mixing rates by incorporating complementary small-angle x-ray scattering measurements for each individual lipid component. This analysis showed that lipid mixing rates, a proxy for hemifusion, across compositional and pressure regimes are determined by changes in lipid spontaneous curvature. Consistent with previous theoretical models, we find a linear relation between lipid intrinsic curvature and the hemifusion stalk formation energy, offering direct experimental support for the stalk hypothesis. Significance statementMembrane fusion proceeds through a hemifusion stalk intermediate whose formation energy depends on lipid intrinsic curvature, a central prediction of the stalk hypothesis that has lacked direct experimental support. Previous tests relied on changes in lipid composition that affect multiple membrane properties, confounding the contribution of curvature alone. Here we use hydrostatic pressure to tune lipid curvature independently of chemical composition and calibrate its effects with high-pressure SAXS. Hemifusion rates across three lipid compositions and four pressures collapse into a single exponential dependence on mean spontaneous curvature, yielding a linear relation between curvature and energy consistent with continuum elastic theory. This work quantifies how lipid composition tunes fusion kinetics, suggesting that small changes in lipid curvature may strongly affect fusogenicity.

biophysics↗

bioRxiv2026

A pectin-based formulation protects milk fat globule membranes in stored human milk

During household storage, expressed human milk can develop odor and flavor changes that trigger infant refusal and lead caregivers to discard their saved milk supply. We show that typical refrigeration and freezing conditions disrupt the milk fat globule membrane (MFGM), exposing milk lipids to lipases that catalyze hydrolysis and oxidation. A pectin-based formulation (PBF) maintains MFGM integrity during storage and following lipase challenge, suppressing production of glycerol, free fatty acid, and oxylipin byproducts without broadly affecting milk macronutrients, the proteome, and culturable microbial burden. Across an independent cohort of lactating individuals, lipase activity varied but tracked with maternal milk lipase gene expression, implicating endogenous lipolysis in stored-milk deterioration. In a blinded olfactory panel, PBF-treated, lipase-challenged milk smelled more like fresh milk than untreated controls. Together, these findings show that stabilizing the MFGM can protect stored human milk from lipase-driven deterioration, preserve sensory quality, and support use for infant feeding.

biochemistry↗

bioRxiv2026

Ether linkages in phospholipids provide modular control of membrane mechanics

The structures of phospholipid headgroups and chains are well-established determinants of membrane elastic properties, but functions for different chemistries that join these moieties together are poorly understood. While common phospholipids feature ester linkages, alkyl ether- and plasmenyl-linked species emerged in prokaryotes, are highly abundant in metazoans, and have been implicated in neurodegeneration and aging. Multiple pathways for ether lipid synthesis evolved convergently, suggesting conserved functions for ether linkage chemistry in the structure of cell membranes. Here we combine experiments and molecular simulations to show that backbone linkage chemistry provides modular control of membrane mechanics and topology through a set of discrete drivers. Alkyl linkages provide the first of these by additively promoting negative intrinsic curvature, which destabilizes bilayers. Ethers also decouple membrane stiffness from viscosity, softening membranes while maintaining packing in the hydrophobic core. The plasmenyl C=C bond represents a second, distinct driver that stabilizes the inverted hexagonal phase by relieving interstitial packing frustration. These results explain the fusogenicity of ether lipids, show how they regulate membrane topology through multiple physical mechanisms, and provide a rationale for convergent evolution of the complex plasmenyl linkage moiety.

biophysics↗

bioRxiv2026

Saturated cardiolipins are potent disruptors of inner mitochondrial membrane structure and function

Cardiolipin (CL) is a four-acyl chained, mitochondrial-specific phospholipid crucial for maintenance of inner mitochondrial membrane (IMM) structure and function. In healthy tissues, CL acyl chains are highly unsaturated and maintained by a conserved remodeling pathway. However, dysregulation of CL acyl chain composition can arise from mutations in the CL transacylase, Tafazzin (TAZ), resulting in Barth syndrome (BTHS), where patients exhibit heightened mitochondrial dysfunction. Cells lacking TAZ accumulate three-acyl chained monolysocardiolipin (MLCL) as well as CL species with saturated acyl chains (CLsat). While the presence of MLCL destabilizes electron transport chain (ETC) complexes and IMM-shaping proteins, the contributions of CLsat to mitochondrial dysfunction have not been elucidated. Here, we find that treatment of TAZ knockout cells with exogenous saturated fatty acids causes accumulation of CLsat and loss of IMM structure despite only minimal changes in MLCL composition. Imaging of cells with elevated CLsat showed reduced fluidity of the inner membrane. Biophysical measurements and molecular dynamics analyses showed that di-saturated (C16:0 18:1)2 CL species order and rigidify membranes, while also losing the intrinsic lipid curvature characteristic of tetra-unsaturated CL. These results implicate CLsat as a potential driver of mitochondrial dysfunction and an additional therapeutic target in mitigating BTHS pathology.

cell biology↗

bioRxiv2026

Coupling between sterol and sphingolipid structure in ordered membrane domains

A hallmark of eukaryotic membranes is the pairing of lineage-specific sterols with characteristic sphingolipid species. Mammalian cell membranes are enriched in both cholesterol and long-chain sphingolipids like sphingomyelin, whereas fungi synthesize ergosterol and very long-chain sphingolipids with sugar-containing head groups. It has been proposed that these two lipid classes co-evolved to support membrane structure and organization. Here we investigated how sterol structure and sphingolipid chain length together control membrane order and phase behavior. In the yeast Saccharomyces cerevisiae, loss of very long-chain C26 sphingolipids disrupted formation of liquid-ordered (Lo) domains in the vacuole membrane. Similarly, substitution of ergosterol synthesis for that of cholesterol also prevented vacuole Lo domains. To determine a possible physical basis of these effects, we investigated synthetic membranes of defined composition containing either ergosterol or cholesterol and sphingomyelin with different chain lengths. In membranes containing egg sphingomyelin with C16 chains, ergosterol only sparsely supported Lo domains, in contrast to cholesterol. Membranes containing sphingomyelin with C26 chains displayed a different pattern. Cholesterol mixtures were largely homogeneous across most compositions, with only a limited region that supported fluid domains. Ergosterol mixtures exhibited a distinct compositional window that supported fluid domains positioned between regimes of uniform membranes and gel phases. This window corresponded to stoichiometric changes in the vacuole as it phase-separates during nutritional restriction. Measurements of membrane order showed that cholesterol strongly increased membrane packing compared to ergosterol in membranes containing egg sphingomyelin, whereas this difference was lost in membranes containing C26 sphingomyelin. The results suggest that sphingolipid chain length can tune sterol interactions needed for membrane organization. SignificanceMembrane phase separation into coexisting ordered and disordered fluid domains has largely been investigated using characteristic mammalian lipid components, cholesterol and long-chain saturated lipids like sphingomyelin. Under nutrient limitation, vacuole membranes in yeast organize into micron-scale domains that are important for their physiology. Compared to mammals, yeast synthesize an alternative sterol, ergosterol, and sphingolipids with very long-chains. We show that vacuole membrane domains are sensitive to both these features, which also show preferential interactions in liposomes that support membrane ordering and phase properties. In lipid mixtures containing very long-chain sphingomyelins, stoichiometric regimes that support phase separation of fluid domains are similar to those of the vacuole lipidome under nutrient limitation. This finding supports a model in which sterols and sphingolipids co-evolved to support membrane structure.

biophysics↗

bioRxiv2025

Homeostatic regulation of intrinsic lipid curvature in eukaryotic cells

Cell membranes are composed of both bilayer-supporting and non-bilayer phospholipids, with the latters negative intrinsic curvature aiding in membrane trafficking and the dynamics of membrane proteins. Phospholipid metabolism has long been recognized to maintain membrane fluidity, but whether it also acts to maintain the function of high-curvature lipids is not resolved. Here, we find that cells grown under hydrostatic pressure - used to artificially reduce lipid curvature - maintain lipidome curvature through metabolic acclimation. We first observed that manipulation of the lipidome curvature via the phosphatidylethanolamine (PE) to phosphatidylcholine (PC) ratio affects high-pressure growth and viability of yeast independently of membrane fluidity. In wild-type cells, X-ray scattering measurements revealed an increased propensity for lipid extracts to form non-lamellar phases after extended pressure incubations. Unexpectedly, this change in phase behavior was not due to increased levels of PE, but of phosphatidylinositol (PI), the only major phospholipid class whose curvature had not been previously characterized. We found that PI is a non-bilayer lipid, with a negative curvature intermediate to that of PE and PC. Accounting for PI, mean lipidome curvature was defended in response to pressure by two distantly related yeasts. Lipidome curvature also responded to pressure in a human cancer cell line through ether phospholipid metabolism and chain remodeling, but not in bacterial cells. These findings indicate that eukaryotic phospholipid metabolism uses diverse mechanisms to maintain curvature frustration in cell membranes.

biophysics↗

bioRxiv2025

Transport of sphingolipids by yeast Npc2 supports phase separation of the vacuole membrane

The yeast vacuole membrane forms ordered microdomains that facilitate micro-lipophagy under nutrient limitation. We previously found that this process involves the intracellular sorting of sphingolipids to the vacuole. While multiple vacuole protein pathways have been identified, corresponding mechanisms for lipid sorting remain undefined. Here we use a range of approaches to identify how endocytic sorting and intraluminal transport of sphingolipids contribute to the formation of vacuole domains. To visualize sphingolipid trafficking, we employed the ceramide analogue BODIPY C12-ceramide (BODIPY-Cer), which is internalized by cells and stains the vacuole. We observed that cells lacking Vps29 and Vps30, proteins involved in endosomal sorting, show altered vacuole domains and accumulate BODIPY-Cer at sites proximal to the plasma membrane. Subsequent incorporation of endocytic-derived ceramide into the vacuole is dependent on the Niemann-Pick Type C 2 protein (Npc2). Loss of Npc2 reduces domain formation and causes BODIPY-Cer to accumulate within the vacuole lumen. Both intra-vacuole trafficking of BODIPY-Cer and membrane phase separation were not dependent on Npc2s canonical receptor, Ncr1. Lipidomics of isolated vacuoles confirmed that Npc2 independently mediates sphingolipid sorting under micro-lipophagy conditions. In liposome assays, Npc2 robustly transports analogues of ceramide and inositol phosphorylceramide, a complex sphingolipid that is enriched in phase-separated vacuoles. We propose that the enlarged binding cavity of yeast Npc2 is specialized for the incorporation of sphingolipids into the vacuole membrane.

biochemistry↗

bioRxiv2025

An origin for a eukaryotic lipid transfer protein fold in Asgard archaea

Eukaryotic cells rely on conserved lipid transfer proteins (LTPs) to shuttle insoluble phospholipids between membranes and support organelle proliferation. Because cells lacking organelles do not require extensive lipid transport networks, it is not known if such machinery had to evolve during eukaryogenesis. Here we describe a class of phospholipid transporters in Asgard archaea that share structural and functional features with eukaryotic LTPs of the START domain superfamily. Asgard genomes encode three START protein classes, StarAsg1-3, conserved across most phyla, of which only StarAsg1 has the large hydrophobic cavity and membrane-docking motifs required for lipid transfer. StarAsg1 from Lokiarchaeia binds anionic membranes in vitro and in yeast, extracts phospholipids, and transfers several phospholipid classes between membranes, as eukaryotic START LTPs do. Phylogeny suggests eukaryotic LTPs could share ancestry with StarAsg1, while StarAsg2/3 group with a eukaryotic Hsp90 co-chaperone. Inter-membrane lipid transport may have predated eukaryogenesis and subsequently facilitated organelle proliferation.

evolutionary biology↗

bioRxiv2025

A cold-inducible phospholipid--protein interaction in brown fat mitochondria optimizes thermogenic capacity

Cold stress elicits dynamic remodeling of the mitochondrial lipidome in brown adipose tissue (BAT), marked by an increase in arachidonoyl-phosphatidylethanolamine (AA-PE). However, the function of membrane lipid rewiring in thermoregulatory physiology has been a longstanding mystery. Here, we identify LPCAT3 as a cold-regulated O-acyltransferase driving the highly selective accrual of AA-PE in BAT mitochondria. Lipid-based proteomics, molecular dynamics simulations, and bioenergetic analyses reveal that AA-PE partitions at the COX4I1 interface of the Cytochrome c oxidase complex, enhancing electron transport chain (ETC) efficiency. Accordingly, fat-specific Lpcat3-knockout mice have defects in respiratory-dependent BAT thermogenesis and cold tolerance, despite intact {beta}-adrenergic signaling and UCP1 function. Under cold acclimation, Lpcat3-/-BAT exhibits ETC dysfunction and activation of the integrated stress-response. Thus, our study illuminates a cold-regulated lipid-protein interaction as a gating factor in UCP1-dependent thermogenesis.

physiology↗

bioRxiv2025

1-Deoxysphingolipids dysregulate membrane properties and cargo trafficking in the early secretory pathway

1-Deoxysphingolipids are non-canonical sphingolipids linked to several diseases, but their cellular effects are poorly understood. Here, we utilize lipid chemical biology approaches to investigate the role of 1-deoxysphingolipid metabolism on the properties and functions of secretory membranes. We first applied organelle-specific bioorthogonal labeling to visualize the subcellular distribution of metabolically tagged 1-deoxysphingolipids in RPE-1 cells, observing that they are retained in the endoplasmic reticulum (ER). We found that 1-deoxysphingolipids can be transported by the non-vesicular transporter CERT in vitro but are retained at ER exit sites (ERES) in cells, suggesting that they do not efficiently sort into vesicular carriers. Cells expressing disease-associated variants of serine palmitoyl-CoA transferase (SPT) accumulated long-chain 1-deoxysphingolipids, which reduced ER membrane fluidity and enlarged ERES. We observed that the rates of membrane protein release from the ER were altered in response to mutant SPT expression, in a manner that was dependent on the cargo affinity for ordered or disordered membranes. We propose that dysregulation of sphingolipid metabolism alters secretory membrane properties, which can then modulate protein trafficking.

cell biology↗

bioRxiv2025

Coupling between membrane undulations and lipid curvature leads to transient local enrichment of cardiolipin in mitochondrial membranes

Organelles such as mitochondria have characteristic shapes that are critical to their function. Recent efforts have revealed that the curvature contributions of individual lipid species can be a factor in the generation of membrane shape in these organelles. Inspired by lipidomics data from yeast mitochondrial membranes, we used Martini coarse-grained molecular dynamics simulations to investigate how lipid composition facilitates membrane shaping. We found that increasing lipid saturation increases bending rigidity while reducing the monolayer spontaneous curvature. We also found that systems containing cardiolipin exhibited decreased bending rigidity and increased spontaneous curvature when compared to bilayers containing its precursor, phosphatidylglycerol. This finding contradicts some prior experimental results that suggest that bilayers containing tetraoleoyl cardiolipin have greater rigidity than dioleoyl phosphatidylcholine bilayers. To investigate this discrepancy, we analyzed our simulations for correlations between lipid localization and local curvature. We found that there are transient correlations between curved lipids such as cardiolipin (CDL) and phosphatidylethanolamine (PE) and curvature; these interactions enrich specific bilayer undulatory modes and cause bilayer softening. Furthermore, we show that curvature-localization of some lipids such as cardiolipin can influence lipids in the opposing leaflet. These observations add to the emerging evidence that lipid geometric features give rise to local interactions, which can cause membrane compositional heterogeneities. The cross-talk between composition-driven tuning of membrane properties and membrane shape has implications for membrane organization and its related functions. SIGNIFICANCEThe material properties of phospholipid membranes are a function of the lipid composition. Theabundance of cardiolipin in the mitochondrial inner membrane implies a functional role for this special lipid. We explore the interactions of cardiolipin with other lipids with varying lipid saturation using coarse-grained molecular dynamics simulations. We find that membranes containing cardiolipin have higher spontaneous curvature and lower bending rigidity when compared to membranes without cardiolipin - in line with prior models and experiments. We also show that the low bending rigidity of cardiolipin-containing symmetric, and flat bilayered systems is due to the transient partitioning of cardiolipin to undulations due to curvature sensing. This is a mechanism for forming lateral membrane heterogeneities in otherwise symmetric systems.

biophysics↗

bioRxiv2025

Dissection of ergosterol metabolism reveals a pathway optimized for membrane phase separation

Sterols are among the most abundant lipids in eukaryotic cells, yet are synthesized through notoriously long metabolic pathways. It has been proposed that the molecular evolution of such pathways must have required each step to increase the capacity of its product to condense and order phospholipids. Here we carry out a systematic analysis of the ergosterol pathway that leverages the yeast vacuoles capacity to phase-separate as a predictive biophysical readout for each intermediate. In the post-synthetic steps specific to ergosterol biosynthesis, we find that successive modifications act to oscillate ordering capacity, settling on a level that supports phase separation while retaining fluidity of the resulting domains. Simulations carried out with each intermediate showed how conformers in the sterols alkyl tail are capable of modulating long-range ordering of phospholipids, which could underlie changes in phase behavior. Our results indicate that the complexity of sterol metabolism could have resulted from the need to balance lipid interactions required for membrane organization.

biophysics↗

bioRxiv2024

Cardiolipin remodeling maintains the inner mitochondrial membrane in cells with saturated lipidomes

Cardiolipin (CL) is a unique, four-chain phospholipid synthesized in the inner mitochondrial membrane (IMM). The acyl chain composition of CL is regulated through a remodeling pathway, whose loss causes mitochondrial dysfunction in Barth syndrome. Yeast has been used extensively as a model system to characterize CL metabolism, but mutants lacking its two remodeling enzymes, Cld1p and Taz1p, have not recapitulated the structural and respiratory phenotypes observed in other systems. Here we show the essential role of CL remodeling in the structure and function of the IMM in yeast grown under reduced oxygenation. Microaerobic fermentation, which mimics natural yeast environments, caused the accumulation of saturated fatty acids and, under these conditions, remodeling mutants showed a loss of IMM ultrastructure. We extended this observation to HEK293 cells, where iPLA2 inhibition by bromoenol lactone resulted in respiratory dysfunction and cristae loss upon mild treatment with exogenous saturated fatty acids. In microaerobic yeast, remodeling mutants accumulated unremodeled, saturated CL, but also displayed reduced total CL levels, highlighting the interplay between saturation and CL biosynthesis and breakdown. We identified the mitochondrial phospholipase A1 Ddl1p as a regulator of CL levels, and those of its precursors phosphatidylglycerol and phosphatidic acid, under these conditions. Loss of DDL1 partially rescued IMM structure in cells unable to initiate CL remodeling and had differing lipidomic effects depending on oxygenation. These results introduce a revised yeast model for investigating CL remodeling and suggest that its structural functions are dependent on the overall lipid environment in the mitochondrion.

cell biology↗

bioRxiv2024

Subcellular imaging of lipids and sugars using genetically encoded proximity sensors

The lipid composition of cells varies widely across organelles and between individual membrane leaflets. Transport proteins are thought to generate this heterogeneity, but measuring their functions in vivo has been hampered by limited tools for imaging lipids at relevant spatial resolutions. Here we present fluorogen-activating coincidence encounter sensing (FACES), a chemogenetic tool capable of quantitatively imaging subcellular lipid pools and reporting their transbilayer orientation in living cells. FACES combines bioorthogonal chemistry with genetically encoded fluorogen-activating proteins (FAPs) for reversible proximity sensing of conjugated molecules. We first apply this approach to identify roles for lipid transfer proteins that traffic phosphatidylcholine pools between the ER and mitochondria. We then show that transmembrane domain-containing FAPs can reveal the membrane asymmetry of multiple lipid classes in the trans-Golgi network and be used to investigate the mechanisms that generate it. Lastly, we demonstrate FACES can be applied to measure other molecule classes, like sugars.

cell biology↗

bioRxiv2024

Organelle-targeted Laurdans measure heterogeneity in subcellular membranes and their responses to saturated lipid stress

Cell organelles feature characteristic lipid compositions that lead to differences in membrane properties. In living cells, membrane ordering and fluidity are commonly measured using the solvatochromic dye Laurdan, whose fluorescence is sensitive to membrane packing. As a general lipophilic dye, Laurdan stains all hydrophobic environments in cells, so it is challenging to characterize membrane properties in specific organelles or assess their responses to pharmacological treatments in intact cells. Here, we describe the synthesis and application of Laurdan-derived probes that read out membrane packing of individual cellular organelles. The set of Organelle-targeted Laurdans (OTL) localizes to the ER, mitochondria, lysosomes and Golgi compartments with high specificity, while retaining the spectral resolution needed to detect biological changes in membrane packing. We show that ratiometric imaging with OTL can resolve membrane heterogeneity within organelles, as well as changes in membrane packing resulting from inhibition of lipid trafficking or bioenergetic processes. We apply these probes to characterize organelle-specific responses to saturated lipid stress. While ER and lysosomal membrane fluidity is sensitive to exogenous saturated fatty acids, that of mitochondrial membranes is protected. We then use differences in ER membrane fluidity to sort populations of cells based on their fatty acid diet, highlighting the ability of organelle-localized solvatochromic probes to distinguish between cells based on their metabolic state. These results expand the repertoire of targeted membrane probes and demonstrate their application to interrogating lipid dysregulation.

biophysics↗

bioRxiv2023

Intracellular sphingolipid sorting drives membrane phase separation in the yeast vacuole

The yeast vacuole membrane can phase separate into ordered and disordered domains, a phenomenon that is required for micro-lipophagy under nutrient limitation. Here we report that sorting of sphingolipids (SLs) into the vacuole membrane controls this process. We first developed a vacuole isolation method to identify lipidome changes during the onset of phase separation in early stationary stage cells. We found that phase separated vacuoles are characterized by increases in lipid raft-forming components not found in the whole cell, including a dramatic change in SL composition. Sorting of both SLs and ergosterol into the vacuole membrane is dependent on Npc2, the yeast homologue of the Niemann-Pick Type C2 lipid transporter. Genetic dissection of SL biosynthesis revealed that the composition of vacuole SLs modulates membrane phase separation and micro-lipophagy under glucose restriction. These results show that lipid trafficking can drive membrane phase separation in vivo and identify SLs as key mediators of this process in yeast.

biophysics↗

bioRxiv2023

Cristae formation is a mechanical buckling event controlled by the inner membrane lipidome

Cristae are high curvature structures in the inner mitochondrial membrane (IMM) that are crucial for ATP production. While cristae-shaping proteins have been defined, analogous mechanisms for lipids have yet to be elucidated. Here we combine experimental lipidome dissection with multi-scale modeling to investigate how lipid interactions dictate IMM morphology and ATP generation. When modulating phospholipid (PL) saturation in engineered yeast strains, we observed a surprisingly abrupt breakpoint in IMM topology driven by a continuous loss of ATP synthase organization at cristae ridges. We found that cardiolipin (CL) specifically buffers the IMM against curvature loss, an effect that is independent of ATP synthase dimerization. To explain this interaction, we developed a continuum model for cristae tubule formation that integrates both lipid and protein-mediated curvatures. The model highlighted a snapthrough instability, which drives IMM collapse upon small changes in membrane properties. We also showed that CL is essential in low oxygen conditions that promote PL saturation. These results demonstrate that the mechanical function of CL is dependent on the surrounding lipid and protein components of the IMM. SynopsisO_LIcritical lipidic breakpoint for yeast mitochondria phenocopies the loss of cristae-shaping proteins in the IMM. C_LIO_LIsaturation controls membrane mechanical properties and modulates ATP synthase oligomerization. C_LIO_LImitochondrial-specific lipid cardiolipin can functionally compensate for increased phospholipid saturation and is required for cristae formation in low oxygen environments. C_LIO_LImathematical model for cristae membrane tubules predicts a snapthrough instability mediated by both protein and lipid-encoded curvatures. C_LI Synopsis Figure O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=156 SRC="FIGDIR/small/532310v3_ufig1.gif" ALT="Figure 1"> View larger version (25K): org.highwire.dtl.DTLVardef@196aefforg.highwire.dtl.DTLVardef@1bafcadorg.highwire.dtl.DTLVardef@122f502org.highwire.dtl.DTLVardef@35afd_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2021

Vacuole phase-partitioning boosts mitochondria activity and cell lifespan through an inter-organelle lipid pipeline

Functional linkage between mitochondria and lysosomes is crucial for survival under starvation and lifespan extension. Despite such co-dependency, the supportive pathways connecting mitochondria and lysosomes remain unclear. Here, we identify an inter-organelle lipid trafficking pathway linking yeast vacuole and mitochondria that results in increased mitochondria growth and respiratory activity under glucose starvation. The pathway depends on vacuolar phase-separated, lipid domains, which provide zones for: activation of the vacuolar proton pump; lipid droplet (LD) docking and internalization; and, lipid transfer from vacuole-to-ER-to-mitochondria. Partitioned vacuolar domains form through a specialized type of macro-autophagy, triggered only under acute glucose starvation, that delivers sterol-rich, endosomal-derived lipids to the vacuole. To balance this lipid influx, the vacuole reroutes lipids back to the ER to support both LD biogenesis and mitochondria growth and activity. Energy produced by enhanced mitochondrial activity then feeds back to support the inter-organelle lipid trafficking pathways to ensure survival under nutrient stress.

cell biology↗