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.

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 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 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 Human Peripheral Blood-derived Mast Cells Contribute to Epithelial to Mesenchymal Transition in Bronchial Epithelial Cells in the Presence of IL-1β

2020 ◽  
Author(s):  
Xian-Song Wang ◽  
Li Xie ◽  
Kaiyu Zheng
Keyword(s):  
Mast Cells ◽  
Peripheral Blood ◽  
Epithelial To Mesenchymal Transition ◽  
Human Peripheral Blood ◽  
Cell Junctions ◽  
Vimentin Expression ◽  
Bronchial Epithelial ◽  
Mesenchymal Transition ◽  
Tgf Β1 ◽  
E Cadherin

Abstract Background: Bronchial epithelial to mesenchymal transition （EMT）is an important mechanism for the airway remodeling in asthmatics. Mast cell is one of the critical effector cells in pathogenesis of asthma. Although mast cells have been shown to release a plethora of pro-fibrotic factors with the potential to induce EMT, it is not clear whether mast cells also directly have an impact on the bronchial EMT. In this study, we investigated the contribution of human mast cells to EMT in human bronchial epithelial cell line 16-HBE. Methods: Human peripheral blood-derived mast cells were co-cultured with 16-HBE cells. The protein and mRNA expression of E-cadherin and vimentin in 16-HBE cells were analyzed by Western blot and quantitative real-time PCR. A scratch wound assay was performed to evaluate the migratory properties of the 16-HBE cells.Results: Mast cells alone failed to produce significant effects on the epithelial morphology, mobility, and expression of E-cadherin and vimentin. However, mast cells in combination of interleukin (IL)-1β significantly decreased E-cadherin expression but increased vimentin expression in the co-cultured 16-HBE cells, which exhibited a spindle-like appearance with reduced cell junctions and enhanced migration. The down-regulation of E-cadherin expression and up-regulation of vimentin expression were not abrogated by the transforming growth factor (TGF)-β1 neutralizing antibody.Conclusion: Mast cells combined with IL-1β, not mast cells alone, were able to induce EMT in 16-HBE cells through a TGF-β1-independent mechanism. The results of in vitro culture suggest the possibility that mast cells contribute to human bronchial epithelial EMT in the asthmatic airway tissues with high level of IL-1β.

scholarly journals β-catenin activation down-regulates cell-cell junction-related genes and induces epithelial-to-mesenchymal transition in colorectal cancers

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Won Kyu Kim ◽  
Yujin Kwon ◽  
Mi Jang ◽  
Minhee Park ◽  
Jiyoon Kim ◽  
...  
Keyword(s):  
Nuclear Localization ◽  
Epithelial To Mesenchymal Transition ◽  
Cell Junctions ◽  
Nuclear Accumulation ◽  
Colorectal Cancers ◽  
Wild Type ◽  
Mesenchymal Transition ◽  
Nuclear Expression ◽  
E Cadherin ◽  
Cell Cell

AbstractWNT signaling activation in colorectal cancers (CRCs) occurs through APC inactivation or β-catenin mutations. Both processes promote β-catenin nuclear accumulation, which up-regulates epithelial-to-mesenchymal transition (EMT). We investigated β-catenin localization, transcriptome, and phenotypic differences of HCT116 cells containing a wild-type (HCT116-WT) or mutant β-catenin allele (HCT116-MT), or parental cells with both WT and mutant alleles (HCT116-P). We then analyzed β-catenin expression and associated phenotypes in CRC tissues. Wild-type β-catenin showed membranous localization, whereas mutant showed nuclear localization; both nuclear and non-nuclear localization were observed in HCT116-P. Microarray analysis revealed down-regulation of Claudin-7 and E-cadherin in HCT116-MT vs. HCT116-WT. Claudin-7 was also down-regulated in HCT116-P vs. HCT116-WT without E-cadherin dysregulation. We found that ZEB1 is a critical EMT factor for mutant β-catenin-mediated loss of E-cadherin and Claudin-7 in HCT116-P and HCT116-MT cells. We also demonstrated that E-cadherin binds to both WT and mutant β-catenin, and loss of E-cadherin releases β-catenin from the cell membrane and leads to its degradation. Alteration of Claudin-7, as well as both Claudin-7 and E-cadherin respectively caused tight junction (TJ) impairment in HCT116-P, and dual loss of TJs and adherens junctions (AJs) in HCT116-MT. TJ loss increased cell motility, and subsequent AJ loss further up-regulated that. Immunohistochemistry analysis of 101 CRCs revealed high (14.9%), low (52.5%), and undetectable (32.6%) β-catenin nuclear expression, and high β-catenin nuclear expression was significantly correlated with overall survival of CRC patients (P = 0.009). Our findings suggest that β-catenin activation induces EMT progression by modifying cell-cell junctions, and thereby contributes to CRC aggressiveness.

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