ATG2 transports lipids to promote autophagosome                    biogenesis

During macroautophagic stress, autophagosomes can be produced continuously and in high numbers. Many different organelles have been reported as potential donor membranes for this sustained autophagosome growth, but specific machinery to support the delivery of lipid to the growing autophagosome membrane has remained unknown. Here we show that the autophagy protein, ATG2, without a clear function since its discovery over 20 yr ago, is in fact a lipid-transfer protein likely operating at the ER–autophagosome interface. ATG2A can bind tens of glycerophospholipids at once and transfers lipids robustly in vitro. An N-terminal fragment of ATG2A that supports lipid transfer in vitro is both necessary and fully sufficient to rescue blocked autophagosome biogenesis in ATG2A/ATG2B KO cells, implying that regulation of lipid homeostasis is the major autophagy-dependent activity of this protein and, by extension, that protein-mediated lipid transfer across contact sites is a principal contributor to autophagosome formation.

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A model for a partnership of lipid transfer proteins and scramblases in membrane expansion and organelle biogenesis

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2101562118 ◽

2021 ◽

Vol 118 (16) ◽

pp. e2101562118

Author(s):

Alireza Ghanbarpour ◽

Diana P. Valverde ◽

Thomas J. Melia ◽

Karin M. Reinisch

Keyword(s):

Lipid Transfer Protein ◽

Membrane Dynamics ◽

Lipid Homeostasis ◽

In Vitro Assays ◽

Lipid Transfer ◽

Organelle Biogenesis ◽

Lipid Transfer Proteins ◽

Transfer Protein ◽

Donor And Acceptor

The autophagy protein ATG2, proposed to transfer bulk lipid from the endoplasmic reticulum (ER) during autophagosome biogenesis, interacts with ER residents TMEM41B and VMP1 and with ATG9, in Golgi-derived vesicles that initiate autophagosome formation. In vitro assays reveal TMEM41B, VMP1, and ATG9 as scramblases. We propose a model wherein membrane expansion results from the partnership of a lipid transfer protein, moving lipids between the cytosolic leaflets of apposed organelles, and scramblases that reequilibrate the leaflets of donor and acceptor organelle membranes as lipids are depleted or augmented. TMEM41B and VMP1 are implicated broadly in lipid homeostasis and membrane dynamics processes in which their scrambling activities likely are key.

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

10.1101/2020.10.19.345074 ◽

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.

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The Medicago truncatula N5 Gene Encoding a Root-Specific Lipid Transfer Protein Is Required for the Symbiotic Interaction with Sinorhizobium meliloti

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-22-12-1577 ◽

2009 ◽

Vol 22 (12) ◽

pp. 1577-1587 ◽

Cited By ~ 33

Author(s):

Youry Pii ◽

Alessandra Astegno ◽

Elisa Peroni ◽

Massimo Zaccardelli ◽

Tiziana Pandolfini ◽

...

Keyword(s):

Medicago Truncatula ◽

Sinorhizobium Meliloti ◽

Lipid Transfer Protein ◽

Symbiotic Association ◽

Lipid Transfer ◽

Symbiotic Interaction ◽

Transgenic Roots ◽

Transfer Protein ◽

Small Proteins

The Medicago truncatula N5 gene is induced in roots after Sinorhizobium meliloti infection and it codes for a putative lipid transfer protein (LTP), a family of plant small proteins capable of binding and transferring lipids between membranes in vitro. Various biological roles for plant LTP in vivo have been proposed, including defense against pathogens and modulation of plant development. The aim of this study was to shed light on the role of MtN5 in the symbiotic interaction between M. truncatula and S. meliloti. MtN5 cDNA was cloned and the mature MtN5 protein expressed in Escherichia coli. The lipid binding capacity and antimicrobial activity of the recombinant MtN5 protein were tested in vitro. MtN5 showed the capacity to bind lysophospholipids and to inhibit M. truncatula pathogens and symbiont growth in vitro. Furthermore, MtN5 was upregulated in roots after infection with either the fungal pathogen Fusarium semitectum or the symbiont S. meliloti. Upon S. meliloti infection, MtN5 was induced starting from 1 day after inoculation (dpi). It reached the highest concentration at 3 dpi and it was localized in the mature nodules. MtN5-silenced roots were impaired in nodulation, showing a 50% of reduction in the number of nodules compared with control roots. On the other hand, transgenic roots overexpressing MtN5 developed threefold more nodules with respect to control roots. Here, we demonstrate that MtN5 possesses biochemical features typical of LTP and that it is required for the successful symbiotic association between M. truncatula and S. meliloti.

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Biochemical analysis of antimicrobial peptides in two different Capsicum genotypes after fruit infection by Colletotrichum gloeosporioides

Bioscience Reports ◽

10.1042/bsr20181889 ◽

2019 ◽

Vol 39 (4) ◽

Cited By ~ 2

Author(s):

Álan C. Maracahipes ◽

Gabriel B. Taveira ◽

Erica O. Mello ◽

André O. Carvalho ◽

Rosana Rodrigues ◽

...

Keyword(s):

Antimicrobial Peptides ◽

Colletotrichum Gloeosporioides ◽

Protein Extraction ◽

Lipid Transfer Protein ◽

Extraction Process ◽

Lipid Transfer ◽

Protease Inhibition ◽

Transfer Protein ◽

Trypsin Inhibition

Abstract There are several phytosanitary problems that have been causing serious damage to the Capsicum crops, including anthracnose. Upon attack by certain pathogens, various protein molecules are produced, which are known as proteins related to pathogenesis (PR proteins), including antimicrobial peptides such as protease inhibitors, defensins and lipid transfer proteins (LTPs). The objective of this work is to identify antimicrobial proteins and/or peptides of two genotypes from Capsicum annuum fruits infected with Colletotrichum gloeosporioides. The fungus was inoculated into Capsicum fruits by the deposition of a spore suspension (106 conidia ml−1), and after 24 and 48 h intervals, the fruits were removed from the humid chamber and subjected to a protein extraction process. Protein analysis of the extracts was performed by tricine gel electrophoresis and Western blotting. The distinctive bands between genotypes in the electrophoresis profiles were subjected to mass spectrometry sequencing. Trypsin inhibition assays, reverse zymographic detection of protease inhibition and β-1,3-glucanase activity assays were also performed and extracts were also tested for their ability to inhibit the growth of C. gloeosporioides fungi ‘in vitro’. There were several low molecular weight proteins in all treated samples, and some treatments in which antimicrobial peptides such as defensin, lipid transfer protein (LTP) and protease inhibitor have been identified. It was shown that the green fruits are more responsive to infection, showing the production of antimicrobial peptides in response to injury and inoculation of the fungus, what did not occur in ripe fruits under any treatment.

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Phospholipid transfer proteins revisited

Biochemical Journal ◽

10.1042/bj3240353 ◽

1997 ◽

Vol 324 (2) ◽

pp. 353-360 ◽

Cited By ~ 123

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.

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In vitro gastrointestinal digestion of the major peach allergen Pru p 3, a lipid transfer protein: Molecular characterization of the products and assessment of their IgE binding abilities

Molecular Nutrition & Food Research ◽

10.1002/mnfr.200900552 ◽

2010 ◽

Vol 54 (10) ◽

pp. 1452-1457 ◽

Cited By ~ 27

Author(s):

Valeria Cavatorta ◽

Stefano Sforza ◽

Giancarlo Aquino ◽

Gianni Galaverna ◽

Arnaldo Dossena ◽

...

Keyword(s):

Molecular Characterization ◽

Lipid Transfer Protein ◽

Lipid Transfer ◽

Gastrointestinal Digestion ◽

Transfer Protein ◽

Ige Binding ◽

In Vitro Gastrointestinal Digestion ◽

Pru P 3

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

eLife ◽

10.7554/elife.54113 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 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.

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

The Journal of Cell Biology ◽

10.1083/jcb.201912010 ◽

2019 ◽

Vol 219 (1) ◽

Cited By ~ 2

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.

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