1
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Choi J, Jang H, Xuan Z, Park D. Emerging roles of ATG9/ATG9A in autophagy: implications for cell and neurobiology. Autophagy 2024:1-15. [PMID: 39099167 DOI: 10.1080/15548627.2024.2384349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Revised: 07/01/2024] [Accepted: 07/22/2024] [Indexed: 08/06/2024] Open
Abstract
Atg9, the only transmembrane protein among many autophagy-related proteins, was first identified in the year 2000 in yeast. Two homologs of Atg9, ATG9A and ATG9B, have been found in mammals. While ATG9B shows a tissue-specific expression pattern, such as in the placenta and pituitary gland, ATG9A is ubiquitously expressed. Additionally, ATG9A deficiency leads to severe defects not only at the molecular and cellular levels but also at the organismal level, suggesting key and fundamental roles for ATG9A. The subcellular localization of ATG9A on small vesicles and its functional relevance to autophagy have suggested a potential role for ATG9A in the lipid supply during autophagosome biogenesis. Nevertheless, the precise role of ATG9A in the autophagic process has remained a long-standing mystery, especially in neurons. Recent findings, however, including structural, proteomic, and biochemical analyses, have provided new insights into its function in the expansion of the phagophore membrane. In this review, we aim to understand various aspects of ATG9 (in invertebrates and plants)/ATG9A (in mammals), including its localization, trafficking, and other functions, in nonneuronal cells and neurons by comparing recent discoveries related to ATG9/ATG9A and proposing directions for future research.Abbreviation: AP-4: adaptor protein complex 4; ATG: autophagy related; cKO: conditional knockout; CLA-1: CLArinet (functional homolog of cytomatrix at the active zone proteins piccolo and fife); cryo-EM: cryogenic electron microscopy; ER: endoplasmic reticulum; KO: knockout; PAS: phagophore assembly site; PtdIns3K: class III phosphatidylinositol 3-kinase; PtdIns3P: phosphatidylinositol-3-phosphate; RB1CC1/FIP200: RB1 inducible coiled-coil 1; SV: synaptic vesicle; TGN: trans-Golgi network; ULK: unc-51 like autophagy activating kinase; WIPI2: WD repeat domain, phosphoinositide interacting 2.
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Affiliation(s)
- Jiyoung Choi
- Department of Medical and Biological Sciences, The Catholic University of Korea, Bucheon, South Korea
- Department of Biotechnology, The Catholic University of Korea, Bucheon, South Korea
| | - Haeun Jang
- Department of Medical and Biological Sciences, The Catholic University of Korea, Bucheon, South Korea
| | - Zhao Xuan
- School of Biology and Ecology, University of Maine, Orono, ME, USA
| | - Daehun Park
- Department of Medical and Biological Sciences, The Catholic University of Korea, Bucheon, South Korea
- Department of Biotechnology, The Catholic University of Korea, Bucheon, South Korea
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2
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Wang JR, Zhang JY, Ji WK. Biogenesis of Rab14-positive Endosome Buds at Golgi-endosome Contacts by the RhoBTB3-SHIP164-Vps26B Complex. Curr Med Sci 2024; 44:864-866. [PMID: 38900387 DOI: 10.1007/s11596-024-2901-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Accepted: 04/09/2024] [Indexed: 06/21/2024]
Affiliation(s)
- Jing-Ru Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Jun-Yao Zhang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Wei-Ke Ji
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
- Cell Architecture Research Center, Huazhong University of Science and Technology, Wuhan, 430030, China.
- State Key Laboratory for Diagnosis and Treatment of Severe Zoonotic Infectious Diseases, Huazhong University of Science and Technology, Wuhan, 430030, China.
- Shenzhen Bay Laboratory, Shenzhen, 518132, China.
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3
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Kang Y, Lehmann KS, Vanegas J, Long H, Jefferson A, Freeman M, Clark S. Structural basis of bulk lipid transfer by bridge-like lipid transfer protein LPD-3. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.21.600134. [PMID: 38948693 PMCID: PMC11213131 DOI: 10.1101/2024.06.21.600134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/02/2024]
Abstract
Bridge-like lipid transport proteins (BLTPs) are an evolutionarily conserved family of proteins that localize to membrane contact sites and are thought to mediate the bulk transfer of lipids from a donor membrane, typically the endoplasmic reticulum (ER), to an acceptor membrane, such as a that of the cell or an organelle 1 . Despite the fundamental importance of BLTPs for cellular function, the architecture, composition, and lipid transfer mechanisms remain poorly characterized. Here, we present the subunit composition and the cryo-electron microscopy structure of the native LPD-3 BLTP complex isolated from transgenic C. elegans . LPD-3 folds into an elongated, rod-shaped tunnel whose interior is filled with ordered lipid molecules that are coordinated by a track of ionizable residues that line one side of the tunnel. LPD-3 forms a complex with two previously uncharacterized proteins, here named "Intake" and "Spigot", both of which interact with the N-terminal end of LPD-3 where lipids enter the tunnel. Intake has three transmembrane helices, one of which borders the entrance to the tunnel; Spigot has one transmembrane helix and extends 80 Å along the cytosolic surface of LPD-3. Experiments in multiple model systems indicate that Spigot plays a conserved role in ER-PM contact site formation. Our LPD-3 complex structural data, together with molecular dynamics simulations of the transmembrane region in a lipid bilayer, reveal protein-lipid interactions that suggest a model for how the native LPD-3-complex mediates bulk lipid transport and provide a foundation for mechanistic studies of BLTPs.
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Wang J, Xiong J, Zhang S, Li D, Chu Q, Chang W, Deng L, Ji WK. Biogenesis of Rab14-positive endosome buds at Golgi-endosome contacts by the RhoBTB3-SHIP164-Vps26B complex. Cell Discov 2024; 10:38. [PMID: 38565878 PMCID: PMC10987540 DOI: 10.1038/s41421-024-00651-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Accepted: 01/25/2024] [Indexed: 04/04/2024] Open
Abstract
Early endosomes (EEs) are crucial in cargo sorting within vesicular trafficking. While cargoes destined for degradation are retained in EEs and eventually transported to lysosomes, recycled cargoes for the plasma membrane (PM) or the Golgi undergo segregation into specialized membrane structures known as EE buds during cargo sorting. Despite this significance, the molecular basis of the membrane expansion during EE bud formation has been poorly understood. In this study, we identify a protein complex comprising SHIP164, an ATPase RhoBTB3, and a retromer subunit Vps26B, which promotes the formation of EE buds at Golgi-EE contacts. Our findings reveal that Vps26B acts as a novel Rab14 effector, and Rab14 activity regulates the association of SHIP164 with EEs. Depletion of SHIP164 leads to enlarged Rab14+ EEs without buds, a phenotype rescued by wild-type SHIP164 but not the lipid transfer-defective mutants. Suppression of RhoBTB3 or Vps26B mirrors the effects of SHIP164 depletion. Together, we propose a lipid transport-dependent pathway mediated by the RhoBTB3-SHIP164-Vps26B complex at Golgi-EE contacts, which is essential for EE budding.
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Affiliation(s)
- Jingru Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Huazhong University of Science and Technology, Wuhan, China
- Department of Ultrasound Medicine, Tangdu Hospital, Fourth Military Medical University, Xi'an, Shaanxi, China
| | - Juan Xiong
- Department of Anesthesiology and Pain Medicine, Hubei Key Laboratory of Geriatric Anesthesia and Perioperative Brain Health, and Wuhan Clinical Research Center for Geriatric Anesthesia, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Shuhan Zhang
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Huazhong University of Science and Technology, Wuhan, China
| | - Dongchen Li
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Huazhong University of Science and Technology, Wuhan, China
- Shenzhen Bay Laboratory, Shenzhen, Guangdong, China
| | - Qingzhu Chu
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Huazhong University of Science and Technology, Wuhan, China
| | | | - Lin Deng
- Shenzhen Bay Laboratory, Shenzhen, Guangdong, China.
| | - Wei-Ke Ji
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Huazhong University of Science and Technology, Wuhan, China.
- Shenzhen Bay Laboratory, Shenzhen, Guangdong, China.
- Cell Architecture Research Center, Huazhong University of Science and Technology, Wuhan, Hubei, China.
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Ugur B, Schueder F, Shin J, Hanna MG, Wu Y, Leonzino M, Su M, McAdow AR, Wilson C, Postlethwait J, Solnica-Krezel L, Bewersdorf J, De Camilli P. VPS13B is localized at the cis-trans Golgi complex interface and is a functional partner of FAM177A1. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.18.572081. [PMID: 38187698 PMCID: PMC10769246 DOI: 10.1101/2023.12.18.572081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
Mutations in VPS13B, a member of a protein family implicated in bulk lipid transport between adjacent membranes, cause Cohen syndrome. VPS13B is known to be concentrated in the Golgi complex, but its precise location within this organelle and thus the site(s) where it achieves lipid transport remains unclear. Here we show that VPS13B is localized at the interface between cis and trans Golgi sub-compartments and that Golgi complex re-formation after Brefeldin A (BFA) induced disruption is delayed in VPS13B KO cells. This delay is phenocopied by loss of FAM177A1, a Golgi complex protein of unknown function reported to be a VPS13B interactor and whose mutations also result in a developmental disorder. In zebrafish, the vps13b orthologue, not previously annotated in this organism, genetically interacts with fam177a1. Collectively, these findings raise the possibility that bulk lipid transport by VPS13B may play a role in expanding Golgi membranes and that VPS13B may be assisted in this function by FAM177A1.
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Affiliation(s)
- Berrak Ugur
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA
- Aligning Science Across Parkinson’s (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- HHMI, Yale University School of Medicine, New Haven, CT, USA
| | - Florian Schueder
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, USA
| | - Jimann Shin
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO, USA
| | - Michael G. Hanna
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA
- Aligning Science Across Parkinson’s (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- HHMI, Yale University School of Medicine, New Haven, CT, USA
| | - Yumei Wu
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA
- Aligning Science Across Parkinson’s (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- HHMI, Yale University School of Medicine, New Haven, CT, USA
| | - Marianna Leonzino
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA
- HHMI, Yale University School of Medicine, New Haven, CT, USA
| | - Maohan Su
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Anthony R. McAdow
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO, USA
| | - Catherine Wilson
- Institute of Neuroscience, University of Oregon, Eugene, OR, USA
| | | | - Lilianna Solnica-Krezel
- Department of Developmental Biology, Washington University School of Medicine, St Louis, MO, USA
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Nanobiology Institute, Yale University, West Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Department of Physics, Yale University, New Haven, CT, USA
| | - Pietro De Camilli
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA
- Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA
- Aligning Science Across Parkinson’s (ASAP) Collaborative Research Network, Chevy Chase, MD, USA
- HHMI, Yale University School of Medicine, New Haven, CT, USA
- Department of Microbial Pathogenesis, Yale University School of Medicine, New Haven, CT, USA
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6
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Hanna M, Guillén-Samander A, De Camilli P. RBG Motif Bridge-Like Lipid Transport Proteins: Structure, Functions, and Open Questions. Annu Rev Cell Dev Biol 2023; 39:409-434. [PMID: 37406299 DOI: 10.1146/annurev-cellbio-120420-014634] [Citation(s) in RCA: 19] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/07/2023]
Abstract
The life of eukaryotic cells requires the transport of lipids between membranes, which are separated by the aqueous environment of the cytosol. Vesicle-mediated traffic along the secretory and endocytic pathways and lipid transfer proteins (LTPs) cooperate in this transport. Until recently, known LTPs were shown to carry one or a few lipids at a time and were thought to mediate transport by shuttle-like mechanisms. Over the last few years, a new family of LTPs has been discovered that is defined by a repeating β-groove (RBG) rod-like structure with a hydrophobic channel running along their entire length. This structure and the localization of these proteins at membrane contact sites suggest a bridge-like mechanism of lipid transport. Mutations in some of these proteins result in neurodegenerative and developmental disorders. Here we review the known properties and well-established or putative physiological roles of these proteins, and we highlight the many questions that remain open about their functions.
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Affiliation(s)
- Michael Hanna
- Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut, USA;
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, USA
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Andrés Guillén-Samander
- Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut, USA;
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, USA
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Pietro De Camilli
- Department of Neuroscience, Yale University School of Medicine, New Haven, Connecticut, USA;
- Department of Cell Biology, Yale University School of Medicine, New Haven, Connecticut, USA
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, Connecticut, USA
- Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut, USA
- Aligning Science Across Parkinson's Collaborative Research Network, Chevy Chase, Maryland, USA
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7
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Guillén-Samander A, De Camilli P. Endoplasmic Reticulum Membrane Contact Sites, Lipid Transport, and Neurodegeneration. Cold Spring Harb Perspect Biol 2023; 15:a041257. [PMID: 36123033 PMCID: PMC10071438 DOI: 10.1101/cshperspect.a041257] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The Endoplasmic Reticulum (ER) is an endomembrane system that plays a multiplicity of roles in cell physiology and populates even the most distal cell compartments, including dendritic tips and axon terminals of neurons. Some of its functions are achieved by a cross talk with other intracellular membranous organelles and with the plasma membrane at membrane contacts sites (MCSs). As the ER synthesizes most membrane lipids, lipid exchanges mediated by lipid transfer proteins at MCSs are a particularly important aspect of this cross talk, which synergizes with the cross talk mediated by vesicular transport. Several mutations of genes that encode proteins localized at ER MCSs result in familial neurodegenerative diseases, emphasizing the importance of the normal lipid traffic within cells for a healthy brain. Here, we provide an overview of such diseases, with a specific focus on proteins that directly or indirectly impact lipid transport.
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Affiliation(s)
- Andrés Guillén-Samander
- Departments of Neuroscience and of Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut 06520, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, Maryland 20815, USA
| | - Pietro De Camilli
- Departments of Neuroscience and of Cell Biology, Howard Hughes Medical Institute, Program in Cellular Neuroscience, Neurodegeneration and Repair, Yale University School of Medicine, New Haven, Connecticut 06520, USA
- Aligning Science Across Parkinson's (ASAP) Collaborative Research Network, Chevy Chase, Maryland 20815, USA
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8
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Dall'Armellina F, Stagi M, Swan LE. In silico modeling human VPS13 proteins associated with donor and target membranes suggests lipid transfer mechanisms. Proteins 2023; 91:439-455. [PMID: 36404287 PMCID: PMC10953354 DOI: 10.1002/prot.26446] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2022] [Revised: 10/14/2022] [Accepted: 11/03/2022] [Indexed: 11/22/2022]
Abstract
The VPS13 protein family constitutes a novel class of bridge-like lipid transferases. Autosomal recessive inheritance of mutations in VPS13 genes is associated with the development of neurodegenerative diseases in humans. Bioinformatic approaches previously recognized the domain architecture of these proteins. In this study, we model the first ever full-length structures of the four human homologs VPS13A, VPS13B, VPS13C, and VPS13D in association with model membranes, to investigate their lipid transfer ability and potential structural association with membrane leaflets. We analyze the evolutionary conservation and physicochemical properties of these proteins, focusing on conserved C-terminal amphipathic helices that disturb organelle surfaces and that, adjoined, resemble a traditional Venetian gondola. The gondola domains share significant structural homology with lipid droplet surface-binding proteins. We introduce in silico protein-membrane models displaying the mode of association of VPS13A, VPS13B, VPS13C, and VPS13D to donor and target membranes, and present potential models of action for protein-mediated lipid transfer.
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Affiliation(s)
- Filippo Dall'Armellina
- Department of Biochemistry and Systems BiologyInstitute of Systems, Molecular and Integrative Biology, University of LiverpoolLiverpoolUK
| | - Massimiliano Stagi
- Department of Biochemistry and Systems BiologyInstitute of Systems, Molecular and Integrative Biology, University of LiverpoolLiverpoolUK
| | - Laura E. Swan
- Department of Biochemistry and Systems BiologyInstitute of Systems, Molecular and Integrative Biology, University of LiverpoolLiverpoolUK
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9
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Du Y, Hu X, Chang W, Deng L, Ji WK, Xiong J. A Possible Role of VPS13B in the Formation of Golgi-Lipid Droplet Contacts Associating with the ER. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2023; 6:25152564231195718. [PMID: 38090145 PMCID: PMC10714374 DOI: 10.1177/25152564231195718] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2022] [Revised: 08/02/2023] [Accepted: 08/02/2023] [Indexed: 02/18/2024]
Abstract
While the physical interactions between the Golgi apparatus (Golgi) and lipid droplets (LDs) have been suggested through system-level imaging, the Golgi-LD membrane contact sites (MCSs) remain largely uncharacterized. Here, we show evidence to support the existence of Golgi-LD MCSs in HEK293 cells. We further suggest that vacuolar protein sorting-associated protein 13B (VPS13B) localizes to and promotes the formation of Golgi-LD contacts upon oleic acid (OA) stimulation using 3D high-resolution microscopy. Depletion of VPS13B moderately affects the formation of Golgi-LD contacts upon OA treatment in addition to the fragmentation of the Golgi. Although cellular functions of VPS13B-mediated contacts are still elusive, these findings may provide a new insight into related diseases caused by loss-of-function mutations of VPS13B.
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Affiliation(s)
- Yuanjiao Du
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xuewen Hu
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | | | - Lin Deng
- Shenzhen Bay Laboratory, Shenzhen, China
| | - Wei-Ke Ji
- Department of Biochemistry and Molecular Biology, School of Basic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
- Cell Architecture Research Center; Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Juan Xiong
- Department of Anesthesiology, Hubei Key Laboratory of Geriatric Anesthesia and Perioperative Brain Health, and Wuhan Clinical Research Center for Geriatric Anesthesia, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
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10
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Pandey T, Zhang J, Wang B, Ma DK. Bridge-Like Lipid Transfer Proteins (BLTPs) in C. elegans: From Genetics to Structures and Functions. CONTACT (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2023; 6:25152564231186489. [PMID: 37455813 PMCID: PMC10345909 DOI: 10.1177/25152564231186489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 06/07/2023] [Indexed: 07/18/2023]
Abstract
In eukaryotic cells, lipid transfer can occur at membrane contact sites (MCS) to facilitate the exchange of various lipids between two adjacent cellular organelle membranes. Lipid transfer proteins (LTPs), including shuttle LTP or bridge-like LTP (BLTP), transport lipids at MCS and are critical for diverse cellular processes, including lipid metabolism, membrane trafficking, and cell signaling. BLTPs (BLTP1-5, including the ATG2 and VPS13 family proteins) contain lipid-accommodating hydrophobic repeating β-groove (RBG) domains that allow the bulk transfer of lipids through MCS. Compared with vesicular lipid transfer and shuttle LTP, BLTPs have been only recently identified. Their functions and regulatory mechanisms are currently being unraveled in various model organisms and by diverse approaches. In this review, we summarize the genetics, structural features, and biological functions of BLTP in the genetically tractable model organism C. elegans. We discuss our recent studies and findings on C. elegans LPD-3, a prototypical megaprotein ortholog of BLTP1, with identified lipid transfer functions that are evolutionarily conserved in multicellular organisms and in human cells. We also highlight areas for future research of BLTP using C. elegans and complementary model systems and approaches. Given the emerging links of BLTP to several human diseases, including Parkinson's disease and Alkuraya-Kučinskas syndrome, discovering evolutionarily conserved roles of BLTPs and their mechanisms of regulation and action should contribute to new advances in basic cell biology and potential therapeutic development for related human disorders.
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Affiliation(s)
- Taruna Pandey
- Cardiovascular Research Institute and Department of Physiology, University of California San Francisco, San Francisco, USA
| | - Jianxiu Zhang
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Bingying Wang
- Cardiovascular Research Institute and Department of Physiology, University of California San Francisco, San Francisco, USA
| | - Dengke K. Ma
- Cardiovascular Research Institute and Department of Physiology, University of California San Francisco, San Francisco, USA
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11
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Braschi B, Bruford EA, Cavanagh AT, Neuman SD, Bashirullah A. The bridge-like lipid transfer protein (BLTP) gene group: introducing new nomenclature based on structural homology indicating shared function. Hum Genomics 2022; 16:66. [PMID: 36461115 PMCID: PMC9719229 DOI: 10.1186/s40246-022-00439-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2022] [Accepted: 11/22/2022] [Indexed: 12/03/2022] Open
Abstract
The HUGO Gene Nomenclature Committee assigns unique symbols and names to human genes. The use of approved nomenclature enables effective communication between researchers, and there are multiple examples of how the usage of unapproved alias symbols can lead to confusion. We discuss here a recent nomenclature update (May 2022) for a set of genes that encode proteins with a shared repeating β-groove domain. Some of the proteins encoded by genes in this group have already been shown to function as lipid transporters. By working with researchers in the field, we have been able to introduce a new root symbol (BLTP, which stands for "bridge-like lipid transfer protein") for this domain-based gene group. This new nomenclature not only reflects the shared domain in these proteins, but also takes into consideration the mounting evidence of a shared lipid transport function.
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Affiliation(s)
- Bryony Braschi
- grid.225360.00000 0000 9709 7726HUGO Gene Nomenclature Committee, European Molecular Biology Laboratory, European Bioinformatics Institute, Hinxton, Cambridgeshire, CB10 1SD UK
| | - Elspeth A. Bruford
- grid.225360.00000 0000 9709 7726HUGO Gene Nomenclature Committee, European Molecular Biology Laboratory, European Bioinformatics Institute, Hinxton, Cambridgeshire, CB10 1SD UK ,grid.5335.00000000121885934Department of Haematology, School of Clinical Medicine, University of Cambridge, Cambridge, Cambridgeshire, CB2 0AW UK
| | - Amy T. Cavanagh
- grid.14003.360000 0001 2167 3675Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222 USA
| | - Sarah D. Neuman
- grid.14003.360000 0001 2167 3675Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222 USA
| | - Arash Bashirullah
- grid.14003.360000 0001 2167 3675Division of Pharmaceutical Sciences, University of Wisconsin-Madison, Madison, WI 53705-2222 USA
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12
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In situ architecture of the lipid transport protein VPS13C at ER-lysosome membrane contacts. Proc Natl Acad Sci U S A 2022; 119:e2203769119. [PMID: 35858323 PMCID: PMC9303930 DOI: 10.1073/pnas.2203769119] [Citation(s) in RCA: 31] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
VPS13 is a eukaryotic lipid transport protein localized at membrane contact sites. Previous studies suggested that it may transfer lipids between adjacent bilayers by a bridge-like mechanism. Direct evidence for this hypothesis from a full-length structure and from electron microscopy (EM) studies in situ is still missing, however. Here, we have capitalized on AlphaFold predictions to complement the structural information already available about VPS13 and to generate a full-length model of human VPS13C, the Parkinson's disease-linked VPS13 paralog localized at contacts between the endoplasmic reticulum (ER) and endo/lysosomes. Such a model predicts an ∼30-nm rod with a hydrophobic groove that extends throughout its length. We further investigated whether such a structure can be observed in situ at ER-endo/lysosome contacts. To this aim, we combined genetic approaches with cryo-focused ion beam (cryo-FIB) milling and cryo-electron tomography (cryo-ET) to examine HeLa cells overexpressing this protein (either full length or with an internal truncation) along with VAP, its anchoring binding partner at the ER. Using these methods, we identified rod-like densities that span the space separating the two adjacent membranes and that match the predicted structures of either full-length VPS13C or its shorter truncated mutant, thus providing in situ evidence for a bridge model of VPS13 in lipid transport.
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Levine TP. 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 (THOUSAND OAKS (VENTURA COUNTY, CALIF.)) 2022; 5:251525642211343. [PMID: 36571082 PMCID: PMC7613979 DOI: 10.1177/25152564221134328] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Lipid transfer between organelles requires proteins that shield the hydrophobic portions of lipids as they cross the cytoplasm. In the last decade a new structural form of lipid transfer protein (LTP) has been found: long hydrophobic grooves made of beta-sheet that bridge between organelles at membrane contact sites. Eukaryotes have five families of bridge-like LTPs: VPS13, ATG2, SHIP164, Hobbit and Tweek. These are unified into a single superfamily through their bridges being composed of just one domain, called the repeating beta groove (RBG) domain, which builds into rod shaped multimers with a hydrophobic-lined groove and hydrophilic exterior. Here, sequences and predicted structures of the RBG superfamily were analyzed in depth. Phylogenetics showed that the last eukaryotic common ancestor contained all five RBG proteins, with duplicated VPS13s. The current set of long RBG protein appears to have arisen in even earlier ancestors from shorter forms with 4 RBG domains. The extreme ends of most RBG proteins have amphipathic helices that might be an adaptation for direct or indirect bilayer interaction, although this has yet to be tested. The one exception to this is the C-terminus of SHIP164, which instead has a coiled-coil. Finally, the exterior surfaces of the RBG bridges are shown to have conserved residues along most of their length, indicating sites for partner interactions almost all of which are unknown. These findings can inform future cell biological and biochemical experiments.
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