scholarly journals Membrane Contact Sites: Complex Zones for Membrane Association and Lipid Exchange

2015 ◽  
Vol 8s1 ◽  
pp. LPI.S37190 ◽  
Author(s):  
Evan Quon ◽  
Christopher T. Beh
Keyword(s):  
Membrane Association ◽  
Ion Transfer ◽  
Lipid Transfer ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Protein Carriers ◽  
Lipid Exchange ◽  
Membrane Tethering ◽  
Membrane Contact

Lipid transport between membranes within cells involves vesicle and protein carriers, but as agents of nonvesicular lipid transfer, the role of membrane contact sites has received increasing attention. As zones for lipid metabolism and exchange, various membrane contact sites mediate direct associations between different organelles. In particular, membrane contact sites linking the plasma membrane (PM) and the endoplasmic reticulum (ER) represent important regulators of lipid and ion transfer. In yeast, cortical ER is stapled to the PM through membrane-tethering proteins, which establish a direct connection between the membranes. In this review, we consider passive and facilitated models for lipid transfer at PM–ER contact sites. Besides the tethering proteins, we examine the roles of an additional repertoire of lipid and protein regulators that prime and propagate PM–ER membrane association. We conclude that instead of being simple mediators of membrane association, regulatory components of membrane contact sites have complex and multilayered functions.

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.

ER-Golgi membrane contact sites

2020 ◽  
Vol 48 (1) ◽  
pp. 187-197 ◽  
Author(s):  
Rossella Venditti ◽  
Maria Chiara Masone ◽  
Maria Antonietta De Matteis
Keyword(s):  
Lipid Transfer ◽  
Lipid Transfer Proteins ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Lipid Exchange ◽  
Pathological Conditions ◽  
The Sixties ◽  
In Trans ◽  
Membrane Contact ◽  
Methodological Approaches

Membrane contact sites (MCSs) are sites where the membranes of two different organelles come into close apposition (10–30 nm). Different classes of proteins populate MCSs including factors that act as tethers between the two membranes, proteins that use the MCSs for their function (mainly lipid or ion exchange), and regulatory proteins and enzymes that can act in trans across the MCSs. The ER-Golgi MCSs were visualized by electron microscopists early in the sixties but have remained elusive for decades due to a lack of suitable methodological approaches. Here we report recent progress in the study of this class of MCSs that has led to the identification of their main morphological features and of some of their components and roles. Among these, lipid transfer proteins and lipid exchange have been the most studied and understood so far. However, many unknowns remain regarding their regulation and their role in controlling key TGN functions such as sorting and trafficking as well as their relevance in physiological and pathological conditions.

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.

The role of membrane contact sites at the bacteria-host interface

2021 ◽  
pp. 1-13
Author(s):  
Chen Jiang ◽  
Xue Huang ◽  
Jia Yao ◽  
Lihua Yu ◽  
Fujing Wei ◽  
...  
Keyword(s):  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact

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 Role of membrane contact sites in protein import into mitochondria

2015 ◽  
Vol 24 (3) ◽  
pp. 277-297 ◽  
Author(s):  
Susanne E. Horvath ◽  
Heike Rampelt ◽  
Silke Oeljeklaus ◽  
Bettina Warscheid ◽  
Martin van der Laan ◽  
...  
Keyword(s):  
Protein Import ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact

scholarly journals A VPS13D spastic ataxia mutation disrupts the conserved adaptor binding site in yeast Vps13

2019 ◽  
Author(s):  
Samantha K. Dziurdzik ◽  
Björn D. M. Bean ◽  
Michael Davey ◽  
Elizabeth Conibear
Keyword(s):  
Binding Site ◽  
Neurological Disorders ◽  
Membrane Recruitment ◽  
Spastic Ataxia ◽  
Membrane Contact Sites ◽  
Contact Sites ◽  
Membrane Contact ◽  
Asparagine Residue ◽  
Early Onset Parkinson’S Disease

AbstractMutations in each of the four human VPS13 (VPS13A-D) proteins are associated with distinct neurological disorders: chorea-acanthocytosis, Cohen syndrome, early-onset Parkinson’s disease and spastic ataxia. Recent evidence suggests that the different VPS13 paralogs transport lipids between organelles at different membrane contact sites. How each VPS13 isoform is targeted to organelles is not known. We have shown that the localization of yeast Vps13 protein to membranes requires a conserved six-repeat region, the Vps13 Adaptor Binding (VAB) domain, which binds to organelle-specific adaptors. Here, we use a systematic mutagenesis strategy to determine the role of each repeat in recognizing each known adaptor. Our results show that mutation of invariant asparagines in repeats 1 and 6 strongly impact the binding all adaptors and block Vps13 membrane recruitment. However, we find that repeats 5 to 6 are sufficient for localization and interaction with adaptors. This supports a model where a single adaptor binding site is found in the last two repeats of the VAB domain, while VAB domain repeat 1 may help maintain domain conformation. Importantly, a disease-causing mutation in VPS13D, which maps to the highly conserved asparagine residue in repeat 6, blocks adaptor binding and Vps13 membrane recruitment when modeled in yeast. Our findings are consistent with a conserved adaptor binding role for the VAB domain and suggests the presence of as-yet-unidentified adaptors in both yeast and humans.

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