scholarly journals Interdomain interactions regulate the localization of a lipid transfer protein at ER-PM contact sites

Biology Open ◽  
2021 ◽  
Vol 10 (3) ◽  
Author(s):  
Bishal Basak ◽  
Harini Krishnan ◽  
Padinjat Raghu
Keyword(s):  
Endoplasmic Reticulum ◽  
Lipid Transfer Protein ◽  
Intramolecular Interaction ◽  
Lipid Transfer ◽  
Loss Of Function ◽  
Transfer Protein ◽  
Contact Sites ◽  
Accurate Localization ◽  
Phosphatidylinositol Transfer ◽  
Interdomain Interactions

ABSTRACT During phospholipase C-β (PLC-β) signalling in Drosophila photoreceptors, the phosphatidylinositol transfer protein (PITP) RDGB, is required for lipid transfer at endoplasmic reticulum (ER)–plasma membrane (PM) contact sites (MCS). Depletion of RDGB or its mis-localization away from the ER–PM MCS results in multiple defects in photoreceptor function. Previously, the interaction between the FFAT motif of RDGB and the integral ER protein dVAP-A was shown to be essential for accurate localization to ER–PM MCS. Here, we report that the FFAT/dVAP-A interaction alone is insufficient to localize RDGB accurately; this also requires the function of the C-terminal domains, DDHD and LNS2. Mutations in each of these domains results in mis-localization of RDGB leading to loss of function. While the LNS2 domain is necessary, it is not sufficient for the correct localization of RDGB, which also requires the C-terminal DDHD domain. The function of the DDHD domain is mediated through an intramolecular interaction with the LNS2 domain. Thus, interactions between the additional domains in a multi-domain PITP together lead to accurate localization at the MCS and signalling function. This article has an associated First Person interview with the first author of the paper.

scholarly journals Interdomain interactions regulate the localization of a lipid transfer protein at ER-PM contact sites

2020 ◽  
Author(s):  
Bishal Basak ◽  
Harini Krishnan ◽  
Padinjat Raghu
Keyword(s):  
Endoplasmic Reticulum ◽  
Lipid Transfer Protein ◽  
Intramolecular Interaction ◽  
Lipid Transfer ◽  
Loss Of Function ◽  
Transfer Protein ◽  
Contact Sites ◽  
Accurate Localization ◽  
Phosphatidylinositol Transfer ◽  
Interdomain Interactions

Abstract During phospholipase C-β (PLC-β) signalling in Drosophila photoreceptors, the phosphatidylinositol transfer protein (PITP) RDGB, is required for lipid transfer at endoplasmic reticulum (ER)-plasma membrane (PM) contact sites (MCS). Depletion of RDGB or its mis-localization away from the ER-PM MCS results in multiple defects in photoreceptor function. Previously, the interaction between the FFAT motif of RDGB and the integral ER protein dVAP-A was shown to be essential for accurate localization to ER-PM MCS. Here, we report that the FFAT/dVAP-A interaction alone is insufficient to localize RDGB accurately; this also requires the function of the C-terminal domains, DDHD and LNS2. Mutations in each of these domains results in mis-localization of RDGB leading to loss of function. While the LNS2 domain is necessary, it is not sufficient for the correct localization of RDGB, which also requires the C-terminal DDHD domain. The function of the DDHD domain is mediated through an intramolecular interaction with the LNS2 domain. Thus, interactions between the additional domains in a multi-domain PITP together lead to accurate localization at the MCS and signalling function.

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 First person – Bishal Basak

Biology Open ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. bio058657
Keyword(s):  
Biological Sciences ◽  
Lipid Transfer Protein ◽  
Vesicular Trafficking ◽  
Early Career ◽  
First Person ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Contact Sites ◽  
Interdomain Interactions ◽  
Selection Of

ABSTRACTFirst Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. Bishal Basak is first author on ‘Interdomain interactions regulate the localization of a lipid transfer protein at ER-PM contact sites’, published in BiO. Bishal is a PhD student in the lab of Professor Raghu Padinjat at National Center for Biological Sciences, Rajiv Gandhi Nagar, Kodigehalli, Bengaluru, Karnataka, India, investigating non-vesicular trafficking of lipids at interorganeller contact sites regulate cellular physiology.

scholarly journals The endoplasmic reticulum-plasma membrane tethering protein TMEM24 is a regulator of cellular Ca2+ homeostasis

2021 ◽  
Author(s):  
Beichen Xie ◽  
Styliani Panagiotou ◽  
Jing Cen ◽  
Patrick Gilon ◽  
Peter Bergsten ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Insulin Secretion ◽  
Lipid Transfer Protein ◽  
Underlying Mechanism ◽  
Lipid Transfer ◽  
Β Cells ◽  
Transfer Protein ◽  
Lipid Exchange ◽  
Membrane Tethering

Endoplasmic reticulum (ER) - plasma membrane (PM) contacts are sites of lipid exchange and Ca2+ transport, and both lipid transport proteins and Ca2+ channels specifically accumulate at these locations. In pancreatic β-cells, both lipid- and Ca2+ signaling are essential for insulin secretion. The recently characterized lipid transfer protein TMEM24 dynamically localize to ER-PM contact sites and provide phosphatidylinositol, a precursor of PI(4)P and PI(4,5)P2, to the plasma membrane. β-cells lacking TMEM24 exhibit markedly suppressed glucose-induced Ca2+ oscillations and insulin secretion but the underlying mechanism is not known. We now show that TMEM24 only weakly interact with the PM, and dissociates in response to both diacylglycerol and nanomolar elevations of cytosolic Ca2+. Release of TMEM24 into the bulk ER membrane also enables direct interactions with mitochondria, and we report that loss of TMEM24 results in excessive accumulation of Ca2+ in both the ER and mitochondria and in impaired mitochondria function.

scholarly journals Phospholipid transfer proteins revisited

1997 ◽  
Vol 324 (2) ◽  
pp. 353-360 ◽  
Author(s):  
Karel. W. A WIRTZ
Keyword(s):  
Mammalian Cells ◽  
Lipid Transfer Protein ◽  
Fusion Reaction ◽  
Lipid Binding ◽  
Lipid Transfer ◽  
Cell Functions ◽  
Transfer Protein ◽  
Phospholipid Transfer ◽  
Phosphatidylinositol Transfer

Phosphatidylinositol transfer protein (PI-TP) and the non-specific lipid transfer protein (nsL-TP) (identical with sterol carrier protein 2) belong to the large and diverse family of intracellular lipid-binding proteins. Although these two proteins may express a comparable phospholipid transfer activity in vitro, recent studies in yeast and mammalian cells have indicated that they serve completely different functions. PI-TP (identical with yeast SEC14p) plays an important role in vesicle flow both in the budding reaction from the trans-Golgi network and in the fusion reaction with the plasma membrane. In yeast, vesicle budding is linked to PI-TP regulating Golgi phosphatidylcholine (PC) biosynthesis with the apparent purpose of maintaining an optimal PI/PC ratio of the Golgi complex. In mammalian cells, vesicle flow appears to be dependent on PI-TP stimulating phosphatidylinositol 4,5-bisphosphate (PIP2) synthesis. This latter process may also be linked to the ability of PI-TP to reconstitute the receptor-controlled PIP2-specific phospholipase C activity. The nsL-TP is a peroxisomal protein which, by its ability to bind fatty acyl-CoAs, is most likely involved in the β-oxidation of fatty acids in this organelle. This protein constitutes the N-terminus of the 58 kDa protein which is one of the peroxisomal 3-oxo-acyl-CoA thiolases. Further studies on these and other known phospholipid transfer proteins are bound to reveal new insights in their important role as mediators between lipid metabolism and cell functions.

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

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Ryan S D'Souza ◽  
Jun Y Lim ◽  
Alper Turgut ◽  
Kelly Servage ◽  
Junmei Zhang ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Cell Migration ◽  
Calcium Channels ◽  
Lipid Transfer Protein ◽  
Calcium Influx ◽  
Focal Adhesions ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Contact Sites ◽  
Lipid Exchange

Coordinated 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 (PM) 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 The autophagic membrane tether ATG2A transfers lipids between membranes

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Shintaro Maeda ◽  
Chinatsu Otomo ◽  
Takanori Otomo
Keyword(s):  
Endoplasmic Reticulum ◽  
De Novo ◽  
Lipid Transfer Protein ◽  
Membrane Vesicles ◽  
Building Blocks ◽  
Underlying Mechanism ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Membrane Compartment ◽  
Membrane Tether

An enigmatic step in de novo formation of the autophagosome membrane compartment is the expansion of the precursor membrane phagophore, which requires the acquisition of lipids to serve as building blocks. Autophagy-related 2 (ATG2), the rod-shaped protein that tethers phosphatidylinositol 3-phosphate (PI3P)-enriched phagophores to the endoplasmic reticulum (ER), is suggested to be essential for phagophore expansion, but the underlying mechanism remains unclear. Here, we demonstrate that human ATG2A is a lipid transfer protein. ATG2A can extract lipids from membrane vesicles and unload them to other vesicles. Lipid transfer by ATG2A is more efficient between tethered vesicles than between untethered vesicles. The PI3P effectors WIPI4 and WIPI1 associate ATG2A stably to PI3P-containing vesicles, thereby facilitating ATG2A-mediated tethering and lipid transfer between PI3P-containing vesicles and PI3P-free vesicles. Based on these results, we propose that ATG2-mediated transfer of lipids from the ER to the phagophore enables phagophore expansion.

scholarly journals ORP5 regulates PI(4)P on the lipid droplet: Novel players on the monolayer

2019 ◽  
Vol 219 (1) ◽  
Author(s):  
Mike F. Renne ◽  
Brooke M. Emerling
Keyword(s):  
Lipid Droplet ◽  
Lipid Composition ◽  
Lipid Transfer Protein ◽  
Lipid Transfer ◽  
Transfer Protein ◽  
Contact Sites ◽  
Phosphatidylinositol 4

How the distinct lipid composition of organelles is determined and maintained is still poorly understood. In this issue, Du et al. (2019. J. Cell Biol.https://doi.org/10.1083/jcb.201905162) show that the lipid transfer protein ORP5 functions at ER–LD contact sites, regulating lipid droplet levels of phosphatidylserine and phosphatidylinositol-4-phosphate.

scholarly journals CARTS biogenesis requires VAP–lipid transfer protein complexes functioning at the endoplasmic reticulum–Golgi interface

2015 ◽  
Vol 26 (25) ◽  
pp. 4686-4699 ◽  
Author(s):  
Yuichi Wakana ◽  
Richika Kotake ◽  
Nanako Oyama ◽  
Motohide Murate ◽  
Toshihide Kobayashi ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Cell Surface ◽  
Lipid Transfer Protein ◽  
Protein Complexes ◽  
Lipid Transfer ◽  
Trans Golgi Network ◽  
Transfer Protein ◽  
Membrane Contact Sites ◽  
Golgi Network

Vesicle-associated membrane protein–associated protein (VAP) is an endoplasmic reticulum (ER)-resident integral membrane protein that controls a nonvesicular mode of ceramide and cholesterol transfer from the ER to the Golgi complex by interacting with ceramide transfer protein and oxysterol-binding protein (OSBP), respectively. We report that VAP and its interacting proteins are required for the processing and secretion of pancreatic adenocarcinoma up-regulated factor, whose transport from the trans-Golgi network (TGN) to the cell surface is mediated by transport carriers called “carriers of the trans-Golgi network to the cell surface” (CARTS). In VAP-depleted cells, diacylglycerol level at the TGN was decreased and CARTS formation was impaired. We found that VAP forms a complex with not only OSBP but also Sac1 phosphoinositide phosphatase at specialized ER subdomains that are closely apposed to the trans-Golgi/TGN, most likely reflecting membrane contact sites. Immobilization of ER–Golgi contacts dramatically reduced CARTS production, indicating that association–dissociation dynamics of the two membranes are important. On the basis of these findings, we propose that the ER–Golgi contacts play a pivotal role in lipid metabolism to control the biogenesis of transport carriers from the TGN.

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.

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