RBG Motif Bridge-Like Lipid Transport Proteins: Structure, Functions, and Open Questions

Annual Review of Cell and Developmental Biology, Год журнала: 2023, Номер 39(1), С. 409 - 434

Опубликована: Июль 5, 2023

The life of eukaryotic cells requires the transport lipids between membranes, which are separated by aqueous environment cytosol. Vesicle-mediated traffic along secretory and endocytic pathways lipid transfer proteins (LTPs) cooperate in this transport. Until recently, known LTPs were shown to carry one or a few at time thought mediate shuttle-like mechanisms. Over last years, new family has been discovered that is defined repeating β-groove (RBG) rod-like structure with hydrophobic channel running their entire length. This localization these membrane contact sites suggest bridge-like mechanism Mutations some result neurodegenerative developmental disorders. Here we review properties well-established putative physiological roles proteins, highlight many questions remain open about functions.

Язык: Английский

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In situ architecture of the lipid transport protein VPS13C at ER–lysosome membrane contacts

Proceedings of the National Academy of Sciences, Год журнала: 2022, Номер 119(29)

Опубликована: Июль 13, 2022

VPS13 is a eukaryotic lipid transport protein localized at membrane contact sites. Previous studies suggested that it may transfer lipids between adjacent bilayers by bridge-like mechanism. Direct evidence for this hypothesis from full-length structure and electron microscopy (EM) in situ still missing, however. Here, we have capitalized on AlphaFold predictions to complement the structural information already available about generate model of human VPS13C, Parkinson's disease-linked paralog contacts endoplasmic reticulum (ER) endo/lysosomes. Such predicts an ∼30-nm rod with hydrophobic groove extends throughout its length. We further investigated whether such can be observed ER-endo/lysosome contacts. To aim, combined genetic approaches cryo-focused ion beam (cryo-FIB) milling cryo-electron tomography (cryo-ET) examine HeLa cells overexpressing (either full length or internal truncation) along VAP, anchoring binding partner ER. Using these methods, identified rod-like densities span space separating two membranes match predicted structures either VPS13C shorter truncated mutant, thus providing bridge transport.

Язык: Английский

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A partnership between the lipid scramblase XK and the lipid transfer protein VPS13A at the plasma membrane

Proceedings of the National Academy of Sciences, Год журнала: 2022, Номер 119(35)

Опубликована: Авг. 22, 2022

Chorea-acanthocytosis (ChAc) and McLeod syndrome are diseases with shared clinical manifestations caused by mutations in VPS13A XK, respectively. Key features of these conditions the degeneration caudate neurons presence abnormally shaped erythrocytes. XK belongs to a family plasma membrane (PM) lipid scramblases whose action results exposure PtdSer at cell surface. is an endoplasmic reticulum (ER)-anchored transfer protein putative role transport lipids contacts ER other membranes. Recently were reported interact still unknown mechanisms. So far, however, there no evidence for colocalization two proteins PM, where resides, as was shown be localized between either mitochondria or droplets. Here we show that can also localize ER–PM via binding its PH domain cytosolic loop such interaction regulated intramolecular within both highly expressed neurons. Binding competitive intracellular membranes mediate tethering functions VPS13A. Our findings support model according which VPS13A-dependent PM coupled scrambling PM. They raise possibility defective surface may responsible neurodegeneration.

Язык: Английский

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Phospholipids are imported into mitochondria by VDAC, a dimeric beta barrel scramblase

Nature Communications, Год журнала: 2023, Номер 14(1)

Опубликована: Дек. 8, 2023

Mitochondria are double-membrane-bounded organelles that depend critically on phospholipids supplied by the endoplasmic reticulum. These lipids must cross outer membrane to support mitochondrial function, but how they do this is unclear. We identify Voltage Dependent Anion Channel (VDAC), an abundant protein, as a scramblase-type lipid transporter catalyzes entry. On reconstitution into vesicles, dimers of human VDAC1 and VDAC2 catalyze rapid transbilayer translocation mechanism unrelated their channel activity. Coarse-grained molecular dynamics simulations reveal scrambling occurs at specific dimer interface where polar residues induce large water defects bilayer thinning. The rate phospholipid import yeast mitochondria order magnitude lower in absence VDAC homologs, indicating VDACs provide main pathway for Thus, isoforms, members superfamily beta barrel proteins, moonlight class scramblases - distinct from alpha-helical scramblase proteins act mitochondria.

Язык: Английский

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Parallel phospholipid transfer by Vps13 and Atg2 determines autophagosome biogenesis dynamics

The Journal of Cell Biology, Год журнала: 2023, Номер 222(7)

Опубликована: Апрель 28, 2023

During autophagy, rapid membrane assembly expands small phagophores into large double-membrane autophagosomes. Theoretical modeling predicts that the majority of autophagosomal phospholipids are derived from highly efficient non-vesicular phospholipid transfer (PLT) across phagophore-ER contacts (PERCS). Currently, tether Atg2 is only PLT protein known to drive phagophore expansion in vivo. Here, our quantitative live-cell imaging analysis reveals a poor correlation between duration and size forming autophagosomes number molecules at PERCS starving yeast cells. Strikingly, we find Atg2-mediated non-rate limiting for autophagosome biogenesis because Vps13 localizes rim promotes parallel with Atg2. In absence Vps13, determines an apparent vivo rate ∼200 per molecule second. We propose conserved proteins cooperate channeling organelle contact sites non-rate-limiting during biogenesis.

Язык: Английский

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Lipid scrambling is a general feature of protein insertases

Proceedings of the National Academy of Sciences, Год журнала: 2024, Номер 121(17)

Опубликована: Апрель 15, 2024

Glycerophospholipids are synthesized primarily in the cytosolic leaflet of endoplasmic reticulum (ER) membrane and must be equilibrated between bilayer leaflets to allow ER membranes derived from it grow. Lipid equilibration is facilitated by integral proteins called “scramblases.” These feature a hydrophilic groove allowing polar heads lipids traverse hydrophobic interior, similar credit card moving through reader. Nevertheless, despite their fundamental role expansion dynamics, identity most scramblases has remained elusive. Here, combining biochemical reconstitution molecular dynamics simulations, we show that lipid scrambling general protein insertases, which insert polypeptide chains into organelles disconnected vesicle trafficking. Our data indicate occurs same channel insertion takes place abolished presence nascent chains. We propose insertases could have so-far-overlooked as scramblases.

Язык: Английский

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Exploring the ATG9A interactome uncovers interaction with VPS13A

Journal of Cell Science, Год журнала: 2024, Номер 137(4)

Опубликована: Янв. 31, 2024

ATG9A, a transmembrane protein of the core autophagy pathway, cycles between Golgi, endosomes and vesicular compartment. ATG9A was recently shown to act as lipid scramblase, this function is thought require its interaction with another protein, ATG2A, which acts transfer protein. Together, ATG2A are proposed expand growing autophagosome. However, implicated in other pathways including membrane repair droplet homeostasis. To elucidate interactors within or beyond autophagy, we performed an interactome analysis through mass spectrometry. This revealed host proteins involved synthesis trafficking, ACSL3, VPS13A VPS13C. Furthermore, show that directly interacts forms complex distinct from ATG9A-ATG2A complex.

Язык: Английский

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Balancing stability and function: impact of the surface charge of SARS-CoV-2 Omicron spike protein

npj Viruses, Год журнала: 2025, Номер 3(1)

Опубликована: Апрель 1, 2025

Abstract The ectodomain of the Omicron SARS-CoV-2 spike has an increased positive surface charge, favoring binding to host cell surface, but may affect stability ectodomain. Thermal studies identified two transitions associated with flexibility receptor domain and unfolding whole ectodomain, respectively. Despite destabilizing effects some mutations, compensatory mutations maintain ECD functional advantages thus supporting viral fitness.

Язык: Английский

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Sequence Analysis and Structural Predictions of Lipid Transfer Bridges in the Repeating Beta Groove (RBG) Superfamily Reveal Past and Present Domain Variations Affecting Form, Function and Interactions of VPS13, ATG2, SHIP164, Hobbit and Tweek

Contact, Год журнала: 2022, Номер 5, С. 251525642211343 - 251525642211343

Опубликована: Янв. 1, 2022

Lipid transfer between organelles requires proteins that shield the hydrophobic portions of lipids as they cross cytoplasm. In last decade a new structural form lipid protein (LTP) has been found: long grooves made beta-sheet bridge at membrane contact sites. Eukaryotes have five families bridge-like LTPs: VPS13, ATG2, SHIP164, Hobbit and Tweek. These are unified into single superfamily through their bridges being composed just one domain, called repeating beta groove (RBG) which builds rod shaped multimers with hydrophobic-lined hydrophilic exterior. Here, sequences predicted structures RBG were analyzed in depth. Phylogenetics showed eukaryotic common ancestor contained all proteins, duplicated VPS13s. The current set appears to arisen even earlier ancestors from shorter forms 4 domains. extreme ends most amphipathic helices might be an adaptation for direct or indirect bilayer interaction, although this yet tested. exception is C-terminus instead coiled-coil. Finally, exterior surfaces shown conserved residues along length, indicating sites partner interactions almost unknown. findings can inform future cell biological biochemical experiments.

Язык: Английский

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Interaction between VPS13A and the XK scramblase is important for VPS13A function in humans

Journal of Cell Science, Год журнала: 2022, Номер 135(17)

Опубликована: Авг. 11, 2022

VPS13 family proteins form conduits between the membranes of different organelles through which lipids are transferred. In humans, there four paralogs, and mutations in genes encoding each them associated with inherited disorders. contain multiple conserved domains. The Vps13 adaptor-binding (VAB) domain binds to adaptor that recruit specific membrane contact sites. This work demonstrates importance a VPS13A function. pleckstrin homology (PH) at C-terminal region is required complex XK scramblase for co-localization within cell. Alphafold modeling was used predict an interaction surface XK. Mutations this disrupt both formation two proteins. Mutant alleles found patients disease truncate PH domain. phenotypic similarities McLeod syndrome caused by XK, respectively, argue loss VPS13A-XK basis diseases.

Язык: Английский

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