scholarly journals Structure, functions and regulation of CERT, a lipid‐transfer protein for the delivery of ceramide at the ER–Golgi membrane contact sites

FEBS Letters ◽  
2019 ◽  
Vol 593 (17) ◽  
pp. 2366-2377 ◽  
Author(s):  
Keigo Kumagai ◽  
Kentaro Hanada
Keyword(s):  
Lipid Transfer Protein ◽  
Structure Functions ◽  
Lipid Transfer ◽  
Golgi Membrane ◽  
Transfer Protein ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact

scholarly journals Calcium-stimulated disassembly of focal adhesions mediated by an ORP3/IQSec1 complex

2019 ◽  
Author(s):  
RS D’Souza ◽  
JY Lim ◽  
A Turgut ◽  
K Servage ◽  
J Zhang ◽  
...  
Keyword(s):  
Cell Migration ◽  
Lipid Transfer Protein ◽  
Calcium Influx ◽  
Focal Adhesions ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Lipid Exchange ◽  
Membrane Contact

AbstractCoordinated assembly and disassembly of integrin-mediated focal adhesions (FAs) is essential for cell migration. Many studies have shown that FA disassembly requires Ca2+ influx, however our understanding of this process remains incomplete. Here we show that Ca2+ influx via STIM1/Orai1 calcium channels, which cluster near FAs, leads to activation of the GTPase Arf5 via the Ca2+-activated GEF IQSec1, and that both IQSec1 and Arf5 activation are essential for adhesion disassembly. We further show that IQSec1 forms a complex with the lipid transfer protein ORP3, and that Ca2+ influx triggers PKC-dependent translocation of this complex to ER/plasma membrane contact sites adjacent to FAs. In addition to allosterically activating IQSec1, ORP3 also extracts PI4P from the PM, in exchange for phosphatidylcholine. ORP3-mediated lipid exchange is also important for FA turnover. Together, these findings identify a new pathway that links calcium influx to FA turnover during cell migration.

scholarly journals VPS13: A lipid transfer protein making contacts at multiple cellular locations

2018 ◽  
Vol 217 (10) ◽  
pp. 3322-3324 ◽  
Author(s):  
Mingming Gao ◽  
Hongyuan Yang
Keyword(s):  
Lipid Transfer Protein ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Cell Biol ◽  
Evolutionarily Conserved ◽  
Membrane Contact

The evolutionarily conserved VPS13 proteins localize to multiple membrane contact sites though their function and regulation has been elusive. Bean et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201804111) found that competitive adaptors control the different localizations of yeast Vps13p, while Kumar et al. (2018. J. Cell Biol. https://doi.org/10.1083/jcb.201807019) provide biochemical and structural evidence for VPS13 proteins in the nonvesicular transport of phospholipids.

scholarly journals Nanoscale architecture of a VAP-A-OSBP tethering complex at membrane contact sites

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Eugenio de la Mora ◽  
Manuela Dezi ◽  
Aurélie Di Cicco ◽  
Joëlle Bigay ◽  
Romain Gautier ◽  
...  
Keyword(s):  
Lipid Transfer Protein ◽  
Structural Information ◽  
Transmembrane Protein ◽  
Lipid Transfer ◽  
Oxysterol Binding Protein ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Golgi Network

AbstractMembrane contact sites (MCS) are subcellular regions where two organelles appose their membranes to exchange small molecules, including lipids. Structural information on how proteins form MCS is scarce. We designed an in vitro MCS with two membranes and a pair of tethering proteins suitable for cryo-tomography analysis. It includes VAP-A, an ER transmembrane protein interacting with a myriad of cytosolic proteins, and oxysterol-binding protein (OSBP), a lipid transfer protein that transports cholesterol from the ER to the trans Golgi network. We show that VAP-A is a highly flexible protein, allowing formation of MCS of variable intermembrane distance. The tethering part of OSBP contains a central, dimeric, and helical T-shape region. We propose that the molecular flexibility of VAP-A enables the recruitment of partners of different sizes within MCS of adjustable thickness, whereas the T geometry of the OSBP dimer facilitates the movement of the two lipid-transfer domains between membranes.

scholarly journals The ER cholesterol sensor SCAP promotes CARTS biogenesis at ER–Golgi membrane contact sites

2020 ◽  
Vol 220 (1) ◽  
Author(s):  
Yuichi Wakana ◽  
Kaito Hayashi ◽  
Takumi Nemoto ◽  
Chiaki Watanabe ◽  
Masato Taoka ◽  
...  
Keyword(s):  
Lipid Transfer ◽  
Golgi Membrane ◽  
Proteolytic Activation ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Defective Mutant ◽  
Transport Defect ◽  
Membrane Contact ◽  
Phosphatidylinositol 4 ◽  
Golgi Network

In response to cholesterol deprivation, SCAP escorts SREBP transcription factors from the endoplasmic reticulum to the Golgi complex for their proteolytic activation, leading to gene expression for cholesterol synthesis and uptake. Here, we show that in cholesterol-fed cells, ER-localized SCAP interacts through Sac1 phosphatidylinositol 4-phosphate (PI4P) phosphatase with a VAP–OSBP complex, which mediates counter-transport of ER cholesterol and Golgi PI4P at ER–Golgi membrane contact sites (MCSs). SCAP knockdown inhibited the turnover of PI4P, perhaps due to a cholesterol transport defect, and altered the subcellular distribution of the VAP–OSBP complex. As in the case of perturbation of lipid transfer complexes at ER–Golgi MCSs, SCAP knockdown inhibited the biogenesis of the trans-Golgi network–derived transport carriers CARTS, which was reversed by expression of wild-type SCAP or a Golgi transport–defective mutant, but not of cholesterol sensing–defective mutants. Altogether, our findings reveal a new role for SCAP under cholesterol-fed conditions in the facilitation of CARTS biogenesis via ER–Golgi MCSs, depending on the ER cholesterol.

scholarly journals The lipid transfer function of RDGB at ER-PM contact sites is regulated by multiple interdomain interactions

2019 ◽  
Author(s):  
Bishal Basak ◽  
Harini Krishnan ◽  
Padinjat Raghu
Keyword(s):  
Endoplasmic Reticulum ◽  
Lipid Homeostasis ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Accurate Localization ◽  
Membrane Contact ◽  
Phosphatidylinositol Transfer ◽  
Interdomain Interactions

SummaryIn Drosophila photoreceptors, following Phospholipase C-β activation, the phosphatidylinositol transfer protein (PITP) RDGB, is required to maintain lipid homeostasis at endoplasmic reticulum (ER) plasma membrane (PM) membrane contact sites (MCS). Depletion or mis-localization of RDGB results in multiple defects in photoreceptors. Previously, interaction between the FFAT motif of RDGB with the integral ER protein dVAP-A was shown to be important for its localization at ER-PM MCS. Here, we report that in addition to FFAT motif, a large unstructured region (USR1) of RDGB is required to support the RDGB/dVAP-A interaction. However, interaction with dVAP-A alone is insufficient for accurate localization of RDGB: this also requires association of RDGB with apical PM, through its C-terminal LNS2 domain. Deletion of LNS2 domain results in complete mis-localisation of RDGB and also induces large mis-regulated interdomain movements abrogating RDGB function. Thus, multiple independent interactions between individual domains of RDGB supports its function at ER-PM MCS.

scholarly journals Nanoscale architecture of a VAP-A-OSBP tethering complex at membrane contact site

2020 ◽  
Author(s):  
Eugenio de la Mora ◽  
Manuela Dezi ◽  
Aurélie Di Cicco ◽  
Joëlle Bigay ◽  
Romain Gautier ◽  
...  
Keyword(s):  
Lipid Transfer Protein ◽  
Structural Information ◽  
Transmembrane Protein ◽  
Lipid Transfer ◽  
Oxysterol Binding Protein ◽  
Transfer Protein ◽  
Membrane Contact Sites ◽  
Membrane Contact ◽  
Golgi Network

SummaryMembrane contact sites (MCS) are subcellular regions where two organelles appose their membranes to exchange small molecules, including lipids. Structural information on how proteins form MCS is scarce. We designed an in vitro MCS with two membranes and a pair of tethering proteins suitable for cryo-tomography analysis. It includes VAP-A, an ER transmembrane protein interacting with a myriad of cytosolic proteins, and oxysterol-binding protein (OSBP), a lipid transfer protein that transports cholesterol from the ER to the trans Golgi network. We show that VAP-A is a highly flexible protein, allowing formation of MCS of variable intermembrane distance. The tethering part of OSBP contains a central, dimeric, and helical T-shape region. We propose that the molecular flexibility of VAP-A enables the recruitment of partners of different sizes within MCS of adjustable thickness, whereas the T geometry of the OSBP dimer facilitates the movement of the two lipid-transfer domains between membranes.

scholarly journals OSBP-mediated cholesterol transfer determines epithelial polarity and associated cargo secretion

2021 ◽  
Author(s):  
David Kovacs ◽  
Anne-Sophie Gay ◽  
Lucile Fleuriot ◽  
Delphine Debayle ◽  
Ana Rita Dias Araujo ◽  
...  
Keyword(s):  
Epithelial To Mesenchymal Transition ◽  
Lipid Transfer Protein ◽  
Cell Junctions ◽  
Lipid Transfer ◽  
Mesenchymal Transition ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Lipid Environment ◽  
E Cadherin

Golgi lipid environment regulates sorting and cargo secretion. However, the mechanisms that spatiotemporally control the lipid composition of the secretory membranes to drive cargo trafficking are poorly understood. Lipid transfer proteins regulate the concentration of specific lipids at membrane contact sites. We hypothesised that by catalysing cholesterol/PI(4)P exchange at ER-trans-Golgi membrane contact sites the lipid transfer protein oxysterol binding protein (OSBP) affects the secretion of a subset of cargoes. Here, we report that OSBP is a major epithelial protein as its inhibition leads to complete loss of apico-basal polarity. By mapping the OSBP proximity proteome with the biotin ligase TurboID, we found that OSBP controls the secretion of multiple membrane associated proteins, including key polarity determinants such as E-cadherin. Mechanistically, we established that OSBP contributes to E-cadherin secretion by supplying cholesterol to post-Golgi membranes. Importantly, when cells downregulate cell-cell junctions upon epithelial-to-mesenchymal transition, they re-wire their lipid homeostasis and downregulate OSBP as well, thus altering the trafficking of the OSBP-dependent secretory cargoes.

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