scholarly journals A programmable DNA-origami platform for studying protein-mediated lipid transfer between bilayers

2019 ◽  
Author(s):  
Xin Bian ◽  
Zhao Zhang ◽  
Pietro De Camilli ◽  
Chenxiang Lin
Keyword(s):  
Dna Origami ◽  
Lipid Transport ◽  
Dna Nanostructures ◽  
Lipid Transfer ◽  
Membrane Contact Sites ◽  
Mechanistic Insight ◽  
Donor And Acceptor ◽  
Membrane Contact ◽  
Insight Into

AbstractNon-vesicular lipid transport between bilayers at membrane contact sites plays important physiological roles. Mechanistic insight into the action of lipid transport proteins localized at these sites (bridge/tunnel versus shuttle models) requires a determination of the distance between bilayers at which this transport can occur. Here, we developed DNA-origami nanostructures to organize size-defined liposomes at precise distances and used them to study lipid transfer by the SMP domain of E-Syt1. Pairs of DNA ring-templated donor and acceptor liposomes were docked through DNA pillars, which determined their distance. The SMP domain was anchored to donor liposomes via an unstructured linker and lipid transfer was assessed via a FRET-based assay. We show that lipid transfer can occur over distances that exceed the length of SMP dimer, compatible with a shuttle model. The DNA nanostructures developed here can be adapted to study other processes occurring where two membranes are closely apposed to each other.

scholarly journals Functions of Oxysterol-Binding Proteins at Membrane Contact Sites and Their Control by Phosphoinositide Metabolism

2021 ◽  
Vol 9 ◽  
Author(s):  
Fubito Nakatsu ◽  
Asami Kawasaki
Keyword(s):  
Lipid Transport ◽  
Phosphoinositide Metabolism ◽  
Lipid Transfer ◽  
Cellular Functions ◽  
Characteristic Functional ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Tightly Coupled ◽  
Membrane Contact ◽  
The Right

Lipids must be correctly transported within the cell to the right place at the right time in order to be fully functional. Non-vesicular lipid transport is mediated by so-called lipid transfer proteins (LTPs), which contain a hydrophobic cavity that sequesters lipid molecules. Oxysterol-binding protein (OSBP)-related proteins (ORPs) are a family of LTPs known to harbor lipid ligands, such as cholesterol and phospholipids. ORPs act as a sensor or transporter of those lipid ligands at membrane contact sites (MCSs) where two different cellular membranes are closely apposed. In particular, a characteristic functional property of ORPs is their role as a lipid exchanger. ORPs mediate counter-directional transport of two different lipid ligands at MCSs. Several, but not all, ORPs transport their lipid ligand from the endoplasmic reticulum (ER) in exchange for phosphatidylinositol 4-phosphate (PI4P), the other ligand, on apposed membranes. This ORP-mediated lipid “countertransport” is driven by the concentration gradient of PI4P between membranes, which is generated by its kinases and phosphatases. In this review, we will discuss how ORP function is tightly coupled to metabolism of phosphoinositides such as PI4P. Recent progress on the role of ORP-mediated lipid transport/countertransport at multiple MCSs in cellular functions will be also discussed.

scholarly journals Mechanisms of nonvesicular lipid transport

2021 ◽  
Vol 220 (3) ◽  
Author(s):  
Karin M. Reinisch ◽  
William A. Prinz
Keyword(s):  
High Volume ◽  
Lipid Transport ◽  
Lipid Transfer ◽  
Specific Lipids ◽  
Membrane Contact Sites ◽  
Membrane Contact ◽  
Transfer Mechanisms ◽  
Efficient Transfer

We have long known that lipids traffic between cellular membranes via vesicles but have only recently appreciated the role of nonvesicular lipid transport. Nonvesicular transport can be high volume, supporting biogenesis of rapidly expanding membranes, or more targeted and precise, allowing cells to rapidly alter levels of specific lipids in membranes. Most such transport probably occurs at membrane contact sites, where organelles are closely apposed, and requires lipid transport proteins (LTPs), which solubilize lipids to shield them from the aqueous phase during their transport between membranes. Some LTPs are cup like and shuttle lipid monomers between membranes. Others form conduits allowing lipid flow between membranes. This review describes what we know about nonvesicular lipid transfer mechanisms while also identifying many remaining unknowns: How do LTPs facilitate lipid movement from and into membranes, do LTPs require accessory proteins for efficient transfer in vivo, and how is directionality of transport determined?

Non-vesicular lipid trafficking at the endoplasmic reticulum–mitochondria interface

2018 ◽  
Vol 46 (2) ◽  
pp. 437-452 ◽  
Author(s):  
Francesca Giordano
Keyword(s):  
Endoplasmic Reticulum ◽  
Lipid Transport ◽  
Lipid Transfer ◽  
Lipid Transfer Proteins ◽  
Transport Pathways ◽  
Lipid Trafficking ◽  
Cellular Processes ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact

Mitochondria are highly dynamic organelles involved in various cellular processes such as energy production, regulation of calcium homeostasis, lipid trafficking, and apoptosis. To fulfill all these functions and preserve their morphology and dynamic behavior, mitochondria need to maintain a defined protein and lipid composition in both their membranes. The maintenance of mitochondrial membrane identity requires a selective and regulated transport of specific lipids from/to the endoplasmic reticulum (ER) and across the mitochondria outer and inner membranes. Since they are not integrated in the classical vesicular trafficking routes, mitochondria exchange lipids with the ER at sites of close apposition called membrane contact sites. Deregulation of such transport activities results in several pathologies including cancer and neurodegenerative disorders. However, we are just starting to understand the function of ER–mitochondria contact sites in lipid transport, what are the proteins involved and how they are regulated. In this review, we summarize recent insights into lipid transport pathways at the ER–mitochondria interface and discuss the implication of recently identified lipid transfer proteins in these processes.

scholarly journals Annexin A6 modulates TBC1D15/Rab7/StARD3 axis to control endosomal cholesterol export in NPC1 cells

2019 ◽  
Vol 77 (14) ◽  
pp. 2839-2857 ◽  
Author(s):  
Elsa Meneses-Salas ◽  
Ana García-Melero ◽  
Kristiina Kanerva ◽  
Patricia Blanco-Muñoz ◽  
Frederic Morales-Paytuvi ◽  
...  
Keyword(s):  
Late Endosome ◽  
Dependent Manner ◽  
Lipid Transfer ◽  
Cholesterol Accumulation ◽  
Membrane Contact Sites ◽  
Late Endosomes ◽  
Membrane Contact ◽  
Domain 3 ◽  
Niemann Pick ◽  
Mutant Cells

Abstract Cholesterol accumulation in late endosomes is a prevailing phenotype of Niemann-Pick type C1 (NPC1) mutant cells. Likewise, annexin A6 (AnxA6) overexpression induces a phenotype reminiscent of NPC1 mutant cells. Here, we demonstrate that this cellular cholesterol imbalance is due to AnxA6 promoting Rab7 inactivation via TBC1D15, a Rab7-GAP. In NPC1 mutant cells, AnxA6 depletion and eventual Rab7 activation was associated with peripheral distribution and increased mobility of late endosomes. This was accompanied by an enhanced lipid accumulation in lipid droplets in an acyl-CoA:cholesterol acyltransferase (ACAT)-dependent manner. Moreover, in AnxA6-deficient NPC1 mutant cells, Rab7-mediated rescue of late endosome-cholesterol export required the StAR-related lipid transfer domain-3 (StARD3) protein. Electron microscopy revealed a significant increase of membrane contact sites (MCS) between late endosomes and ER in NPC1 mutant cells lacking AnxA6, suggesting late endosome-cholesterol transfer to the ER via Rab7 and StARD3-dependent MCS formation. This study identifies AnxA6 as a novel gatekeeper that controls cellular distribution of late endosome-cholesterol via regulation of a Rab7-GAP and MCS formation.

scholarly journals The Hob Proteins: Putative, Novel Lipid Transfer Proteins at ER-PM Contact Sites

Contact ◽  
2021 ◽  
Vol 4 ◽  
pp. 251525642110523
Author(s):  
Sarah D. Neuman ◽  
Amy T. Cavanagh ◽  
Arash Bashirullah
Keyword(s):  
Structural Models ◽  
Model Systems ◽  
Lipid Transfer ◽  
Lipid Transfer Proteins ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Bona Fide ◽  
Membrane Contact ◽  
Mutant Cells ◽  
Critical Process

Nonvesicular transfer of lipids at membrane contact sites (MCS) has recently emerged as a critical process for cellular function. Lipid transfer proteins (LTPs) mediate this unique transport mechanism, and although several LTPs are known, the cellular complement of these proteins continues to expand. Our recent work has revealed the highly conserved but poorly characterized Hobbit/Hob proteins as novel, putative LTPs at endoplasmic reticulum-plasma membrane (ER-PM) contact sites. Using both S. cerevisiae and D. melanogaster model systems, we demonstrated that the Hob proteins localize to ER-PM contact sites via an N-terminal ER membrane anchor and conserved C-terminal sequences. These conserved C-terminal sequences bind to phosphoinositides (PIPs), and the distribution of PIPs is disrupted in hobbit mutant cells. Recently released structural models of the Hob proteins exhibit remarkable similarity to other bona fide LTPs, like VPS13A and ATG2, that function at MCS. Hobbit is required for viability in Drosophila, suggesting that the Hob proteins are essential genes that may mediate lipid transfer at MCS.

scholarly journals The endoplasmic reticulum-mitochondria encounter structure: coordinating lipid metabolism across membranes

2020 ◽  
Vol 401 (6-7) ◽  
pp. 811-820 ◽  
Author(s):  
Benoît Kornmann
Keyword(s):  
Endoplasmic Reticulum ◽  
Bacterial Symbiont ◽  
Exact Role ◽  
Intracellular Lipid ◽  
Lipid Trafficking ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Tethering ◽  
Membrane Contact ◽  
Insight Into

AbstractEndosymbiosis, the beginning of a collaboration between an archaeon and a bacterium and a founding step in the evolution of eukaryotes, owes its success to the establishment of communication routes between the host and the symbiont to allow the exchange of metabolites. As far as lipids are concerned, it is the host that has learnt the symbiont’s language, as eukaryote lipids appear to have been borrowed from the bacterial symbiont. Mitochondria exchange lipids with the rest of the cell at membrane contact sites. In fungi, the endoplasmic reticulum-mitochondria encounter structure (ERMES) is one of the best understood membrane tethering complexes. Its discovery has yielded crucial insight into the mechanisms of intracellular lipid trafficking. Despite a wealth of data, our understanding of ERMES formation and its exact role(s) remains incomplete. Here, I endeavour to summarise our knowledge on the ERMES complex and to identify lingering gaps.

scholarly journals SHIP164 is a Chorein Motif Containing Lipid Transport Protein that Controls Membrane Dynamics and Traffic at the Endosome-Golgi Interface.

2021 ◽  
Author(s):  
Michael G Hanna ◽  
Patreece Suen ◽  
Yumei Wu ◽  
Karin M Reinisch ◽  
Pietro De Camilli
Keyword(s):  
Functional Characterization ◽  
Membrane Dynamics ◽  
Endocytic Pathway ◽  
Lipid Transfer ◽  
Vesicular Traffic ◽  
Membrane Contact Sites ◽  
Membrane Contact ◽  
Retrograde Traffic ◽  
Transfer Properties

Cellular membranes differ in protein and lipid composition as well as in the protein-lipid ratio. Thus, progression of membranous organelles along traffic routes requires mechanisms to control bilayer lipid chemistry and their abundance relative to proteins. The recent structural and functional characterization of VPS13-family proteins has suggested a mechanism through which lipids can be transferred in bulk from one membrane to another at membrane contact sites, and thus independently of vesicular traffic. Here we show that SHIP164 (UHRF1BP1L) shares structural and lipid transfer properties with these proteins and is localized on a subpopulation of vesicle clusters in the early endocytic pathway whose membrane cargo includes the cation-independent mannose-6-phosphate receptor (MPR) and ATG9. Loss of SHIP164 disrupts retrograde traffic of these organelles to the Golgi complex. Our findings raise the possibility that bulk transfer of lipids to endocytic membranes may play a role in their traffic.

scholarly journals Reconstitution of autophagosome nucleation defines Atg9 vesicles as seeds for membrane formation

Science ◽  
2020 ◽  
Vol 369 (6508) ◽  
pp. eaaz7714 ◽  
Author(s):  
Justyna Sawa-Makarska ◽  
Verena Baumann ◽  
Nicolas Coudevylle ◽  
Sören von Bülow ◽  
Veronika Nogellova ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
De Novo ◽  
Lipid Transfer ◽  
Related Protein ◽  
Membrane Formation ◽  
Selective Autophagy ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Phosphatidylinositol 3

Autophagosomes form de novo in a manner that is incompletely understood. Particularly enigmatic are autophagy-related protein 9 (Atg9)–containing vesicles that are required for autophagy machinery assembly but do not supply the bulk of the autophagosomal membrane. In this study, we reconstituted autophagosome nucleation using recombinant components from yeast. We found that Atg9 proteoliposomes first recruited the phosphatidylinositol 3-phosphate kinase complex, followed by Atg21, the Atg2-Atg18 lipid transfer complex, and the E3-like Atg12–Atg5-Atg16 complex, which promoted Atg8 lipidation. Furthermore, we found that Atg2 could transfer lipids for Atg8 lipidation. In selective autophagy, these reactions could potentially be coupled to the cargo via the Atg19-Atg11-Atg9 interactions. We thus propose that Atg9 vesicles form seeds that establish membrane contact sites to initiate lipid transfer from compartments such as the endoplasmic reticulum.

Touché! STARD3 and STARD3NL tether the ER to endosomes

2016 ◽  
Vol 44 (2) ◽  
pp. 493-498 ◽  
Author(s):  
Léa P. Wilhelm ◽  
Catherine Tomasetto ◽  
Fabien Alpy
Keyword(s):  
Lipid Transfer Protein ◽  
Regulatory Protein ◽  
Direct Interaction ◽  
Lipid Transfer ◽  
Membrane Contact Sites ◽  
Late Endosomes ◽  
Metabolite Exchange ◽  
Membrane Contact ◽  
Domain 3 ◽  
Steroidogenic Acute Regulatory

Membrane contact sites (MCSs) are subcellular regions where the membranes of distinct organelles come into close apposition. These specialized areas of the cell, which are involved in inter-organelle metabolite exchange, are scaffolded by specific complexes. STARD3 [StAR (steroidogenic acute regulatory protein)-related lipid transfer domain-3] and its close paralogue STARD3NL (STARD3 N-terminal like) are involved in the formation of contacts between late-endosomes and the endoplasmic reticulum (ER). The lipid transfer protein (LTP) STARD3 and STARD3NL, which are both anchored on the limiting membrane of late endosomes (LEs), interact with ER-anchored VAP [VAMP (vesicle-associated membrane protein)-associated protein] (VAP-A and VAP-B) proteins. This direct interaction allows ER–endosome contact formation. STARD3 or STARD3NL-mediated ER–endosome contacts, which affect endosome dynamics, are believed to be involved in cholesterol transport.

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