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.

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.

scholarly journals Cholesterol Overload: Contact Sites to the Rescue!

Contact ◽  
2019 ◽  
Vol 2 ◽  
pp. 251525641989350 ◽  
Author(s):  
Carlos Enrich ◽  
Carles Rentero ◽  
Thomas Grewal ◽  
Clare E. Futter ◽  
Emily R. Eden
Keyword(s):  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Cholesterol Homeostasis ◽  
Low Density ◽  
Cholesterol Accumulation ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Late Endosomes ◽  
Membrane Contact ◽  
Niemann Pick

Delivery of low-density lipoprotein-derived cholesterol to the endoplasmic reticulum (ER) is essential for cholesterol homeostasis, yet the mechanism of this transport has largely remained elusive. Two recent reports shed some light on this process, uncovering a role for Niemann Pick type-C1 protein (NPC1) in the formation of membrane contact sites (MCS) between late endosomes (LE)/lysosomes (Lys) and the ER. Both studies identified a loss of MCS in cells lacking functional NPC1, where cholesterol accumulates in late endocytic organelles. Remarkably, and taking different approaches, both studies have made a striking observation that expansion of LE/Lys-ER MCS can rescue the cholesterol accumulation phenotype in NPC1 mutant or deficient cells. In both cases, the cholesterol was shown to be transported to the ER, demonstrating the importance of ER-LE/Lys contact sites in the direct transport of low-density lipoprotein-derived cholesterol to the ER.

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 Cholesterol sensor ORP1L contacts the ER protein VAP to control Rab7–RILP–p150Glued and late endosome positioning

2009 ◽  
Vol 185 (7) ◽  
pp. 1209-1225 ◽  
Author(s):  
Nuno Rocha ◽  
Coenraad Kuijl ◽  
Rik van der Kant ◽  
Lennert Janssen ◽  
Diane Houben ◽  
...  
Keyword(s):  
Motor Proteins ◽  
Oxysterol Binding Protein ◽  
Membrane Contact Sites ◽  
Cholesterol Levels ◽  
Dynein Motor ◽  
Late Endosomes ◽  
In Trans ◽  
Membrane Contact ◽  
Cholesterol Control ◽  
Niemann Pick

Late endosomes (LEs) have characteristic intracellular distributions determined by their interactions with various motor proteins. Motor proteins associated to the dynactin subunit p150Glued bind to LEs via the Rab7 effector Rab7-interacting lysosomal protein (RILP) in association with the oxysterol-binding protein ORP1L. We found that cholesterol levels in LEs are sensed by ORP1L and are lower in peripheral vesicles. Under low cholesterol conditions, ORP1L conformation induces the formation of endoplasmic reticulum (ER)–LE membrane contact sites. At these sites, the ER protein VAP (VAMP [vesicle-associated membrane protein]-associated ER protein) can interact in trans with the Rab7–RILP complex to remove p150Glued and associated motors. LEs then move to the microtubule plus end. Under high cholesterol conditions, as in Niemann-Pick type C disease, this process is prevented, and LEs accumulate at the microtubule minus end as the result of dynein motor activity. These data explain how the ER and cholesterol control the association of LEs with motor proteins and their positioning in cells.

scholarly journals NPC1 regulates ER contacts with endocytic organelles to mediate cholesterol egress

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
D. Höglinger ◽  
T. Burgoyne ◽  
E. Sanchez-Heras ◽  
P. Hartwig ◽  
A. Colaco ◽  
...  
Keyword(s):  
Dietary Cholesterol ◽  
Cholesterol Transport ◽  
Cholesterol Accumulation ◽  
C Protein ◽  
Membrane Contact Sites ◽  
Sterol Transport ◽  
Membrane Contact ◽  
Mitochondrial Cholesterol ◽  
Niemann Pick ◽  
The Impact

Abstract Transport of dietary cholesterol from endocytic organelles to the endoplasmic reticulum (ER) is essential for cholesterol homoeostasis, but the mechanism and regulation of this transport remains poorly defined. Membrane contact sites (MCS), microdomains of close membrane apposition, are gaining attention as important platforms for non-vesicular, inter-organellar communication. Here we investigate the impact of ER-endocytic organelle MCS on cholesterol transport. We report a role for Niemann-Pick type C protein 1 (NPC1) in tethering ER-endocytic organelle MCS where it interacts with the ER-localised sterol transport protein Gramd1b to regulate cholesterol egress. We show that artificially tethering MCS rescues the cholesterol accumulation that characterises NPC1-deficient cells, consistent with direct lysosome to ER cholesterol transport across MCS. Finally, we identify an expanded population of lysosome-mitochondria MCS in cells depleted of NPC1 or Gramd1b that is dependent on the late endosomal sterol-binding protein STARD3, likely underlying the mitochondrial cholesterol accumulation in NPC1-deficient cells.

scholarly journals Analysis of cholesterol export from endo-lysosomes by Niemann Pick C2 protein using combined fluorescence and X-ray microscopy

2018 ◽  
Author(s):  
Alice Dupont ◽  
Frederik W. Lund ◽  
Maria Louise V. Jensen ◽  
Maria Szomek ◽  
Gitte K. Nielsen ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Human Fibroblasts ◽  
Three Dimensional ◽  
Cell Periphery ◽  
X Ray ◽  
Transfer Protein ◽  
Membrane Contact Sites ◽  
Late Endosomes ◽  
Membrane Contact ◽  
Niemann Pick

AbstractThe Niemann-Pick C2 protein (NPC2) is a sterol transfer protein in late endosomes and lysosomes (LE/LYSs). How its capacity to transport cholesterol between membranes is linked to endo-lysosomal membrane trafficking is not known. Using quantitative fluorescence imaging combined with soft X-ray tomography (SXT); we show that NPC2 mediated sterol efflux is accompanied by large changes in distribution, size and ultrastructure of endocytic organelles. We observed clearance of intra-luminal lipid deposits, a decrease in number of autophagosomes, formation of membrane contact sites (MCSs) to the endoplasmic reticulum and extensive tubulation of LE/LYSs in three-dimensional SXT reconstructions of NPC2 treated human fibroblasts. The cells could recycle the cholesterol analog dehydroergosterol (DHE) from LE/LYSs slowly also in the absence of NPC2 protein but internalized NPC2 synchronized and accelerated this process significantly. Most fluorescent NPC2 was retained in LE/LYSs while DHE was selectively removed from these organelles, at least partially by non-vesicular exchange with other membranes. During sterol efflux LE/LYSs were reallocated to the cell periphery, where they could fuse with newly formed endosomes. Surface shedding of micro-vesicles was found, suggesting a pathway for cellular sterol release. We conclude that NPC2 mediated sterol efflux from LE/LYSs controls membrane traffic through the endo-lysosomal pathway.

scholarly journals PDZD8 interacts with Protrudin and Rab7 at ER-late endosome membrane contact sites associated with mitochondria

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Yael Elbaz-Alon ◽  
Yuting Guo ◽  
Nadav Segev ◽  
Michal Harel ◽  
Daniel E. Quinnell ◽  
...  
Keyword(s):  
Late Endosome ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact

scholarly journals A role for oxysterol-binding protein–related protein 5 in endosomal cholesterol trafficking

2011 ◽  
Vol 192 (1) ◽  
pp. 121-135 ◽  
Author(s):  
Ximing Du ◽  
Jaspal Kumar ◽  
Charles Ferguson ◽  
Timothy A. Schulz ◽  
Yan Shan Ong ◽  
...  
Keyword(s):  
Binding Protein ◽  
Lipid Binding ◽  
Cholesterol Trafficking ◽  
Cholesterol Accumulation ◽  
Oxysterol Binding Protein ◽  
Late Endosomes ◽  
Evolutionarily Conserved ◽  
Niemann Pick ◽  
Related Proteins ◽  
Lipid Binding Proteins

Oxysterol-binding protein (OSBP) and its related proteins (ORPs) constitute a large and evolutionarily conserved family of lipid-binding proteins that target organelle membranes to mediate sterol signaling and/or transport. Here we characterize ORP5, a tail-anchored ORP protein that localizes to the endoplasmic reticulum. Knocking down ORP5 causes cholesterol accumulation in late endosomes and lysosomes, which is reminiscent of the cholesterol trafficking defect in Niemann Pick C (NPC) fibroblasts. Cholesterol appears to accumulate in the limiting membranes of endosomal compartments in ORP5-depleted cells, whereas depletion of NPC1 or both ORP5 and NPC1 results in luminal accumulation of cholesterol. Moreover, trans-Golgi resident proteins mislocalize to endosomal compartments upon ORP5 depletion, which depends on a functional NPC1. Our results establish the first link between NPC1 and a cytoplasmic sterol carrier, and suggest that ORP5 may cooperate with NPC1 to mediate the exit of cholesterol from endosomes/lysosomes.

scholarly journals Mutagenesis of the putative sterol-sensing domain of yeast Niemann Pick C–related protein reveals a primordial role in subcellular sphingolipid distribution

2004 ◽  
Vol 164 (4) ◽  
pp. 547-556 ◽  
Author(s):  
Krishnamurthy Malathi ◽  
Katsumi Higaki ◽  
Arthur H. Tinkelenberg ◽  
Dina A. Balderes ◽  
Dorca Almanzar-Paramio ◽  
...  
Keyword(s):  
Neurodegenerative Disorder ◽  
Chinese Hamster ◽  
Antibiotic Sensitivity ◽  
Cholesterol Accumulation ◽  
Transmembrane Glycoprotein ◽  
Lysosomal Accumulation ◽  
Type C ◽  
Niemann Pick ◽  
Sphingolipid Biosynthesis ◽  
Mutant Cells

Lipid movement between organelles is a critical component of eukaryotic membrane homeostasis. Niemann Pick type C (NP-C) disease is a fatal neurodegenerative disorder typified by lysosomal accumulation of cholesterol and sphingolipids. Expression of yeast NP-C–related gene 1 (NCR1), the orthologue of the human NP-C gene 1 (NPC1) defective in the disease, in Chinese hamster ovary NPC1 mutant cells suppressed lipid accumulation. Deletion of NCR1, encoding a transmembrane glycoprotein predominantly residing in the vacuole of normal yeast, gave no phenotype. However, a dominant mutation in the putative sterol-sensing domain of Ncr1p conferred temperature and polyene antibiotic sensitivity without changes in sterol metabolism. Instead, the mutant cells were resistant to inhibitors of sphingolipid biosynthesis and super sensitive to sphingosine and C2-ceramide. Moreover, plasma membrane sphingolipids accumulated and redistributed to the vacuole and other subcellular membranes of the mutant cells. We propose that the primordial function of these proteins is to recycle sphingolipids and that defects in this process in higher eukaryotes secondarily result in cholesterol accumulation.

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