Organization and function of membrane contact sites

Helle, Sebastian Carsten Johannes; Kanfer, Gil; Kolar, Katja; Lang, Alexander; Michel, Agnès H.; Kornmann, Benoı̂t

doi:10.1016/j.bbamcr.2013.01.028

Cited by 388 publications

(386 citation statements)

References 175 publications

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“…The localization of AZI1 and EARLI1 and enrichment of AZI1 at dynamic contact sites indicates that AZI1/ EARLI1 may function to facilitate AZA or lipid-AZA movement. Moreover, MCSs not only assist in lipid exchange, but also ensure and provide specificity 29 . This could explain why DIR1, an AZI1/ EARLI1 interactor and possible member of a 'SAR complex', could be transporting lipidic signals other than AZA 17,32 .…”

Section: Resultsmentioning

confidence: 99%

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Arabidopsis AZI1 family proteins mediate signal mobilization for systemic defence priming

et al. 2015

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Priming is a major mechanism behind the immunological 'memory' observed during two key plant systemic defences: systemic acquired resistance (SAR) and induced systemic resistance (ISR). Lipid-derived azelaic acid (AZA) is a mobile priming signal. Here, we show that the lipid transfer protein (LTP)-like AZI1 and its closest paralog EARLI1 are necessary for SAR, ISR and the systemic movement and uptake of AZA in Arabidopsis. Imaging and fractionation studies indicate that AZI1 and EARLI1 localize to expected places for lipid exchange/movement to occur. These are the ER/plasmodesmata, chloroplast outer envelopes and membrane contact sites between them. Furthermore, these LTP-like proteins form complexes and act at the site of SAR establishment. The plastid targeting of AZI1 and AZI1 paralogs occurs through a mechanism that may enable/facilitate their roles in signal mobilization.

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Section: Resultsmentioning

confidence: 99%

“…In plants, MCSs occur between the chloroplast, ER and plasma membrane (PM) 26,27 . Lipid transfer proteins (LTPs) are key components in MCS formation, where lipid exchange occurs [27][28][29] .…”

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confidence: 99%

Arabidopsis AZI1 family proteins mediate signal mobilization for systemic defence priming

et al. 2015

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“…The Arabidopsis SYT1 Localizes at the ER and the PM and Accumulates at ER-PM Contact Sites SYT1 contains a modular structure similar to ER-PM tether proteins such as E-Syts and tricalbins (Craxton, 2010;Yamazaki et al, 2010), proteins that are localized at specific ER-PM subdomains (Giordano et al, 2013;Helle et al, 2013;Prinz, 2014). Moreover, cell biological and biochemical analyses have reported SYT1 being at the ER, PM, and plasmodesmata (Schapire et al, 2008;Lewis and Lazarowitz, 2010;Yamazaki et al, 2010).…”

Section: Resultsmentioning

confidence: 99%

“…These proteins act as molecular bridges between the ER and the PM at sites where both cellular membranes are in close proximity, called ER-PM contact sites. These specialized microdomains carry out important roles in organelle communication, lipid and Ca 2+ homeostasis, and intracellular signaling in animal and yeast cells (Toulmay and Prinz, 2011;Helle et al, 2013;Prinz, 2014). In plants, these ER-PM contact sites have been morphologically described for decades (Staehelin, 1997), but their physiological roles have not been thoroughly characterized.…”

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confidence: 99%

The Arabidopsis Synaptotagmin1 Is Enriched in Endoplasmic Reticulum-Plasma Membrane Contact Sites and Confers Cellular Resistance to Mechanical Stresses

et al. 2015

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Eukaryotic endoplasmic reticulum (ER)-plasma membrane (PM) contact sites are evolutionarily conserved microdomains that have important roles in specialized metabolic functions such as ER-PM communication, lipid homeostasis, and Ca 2+ influx. Despite recent advances in knowledge about ER-PM contact site components and functions in yeast (Saccharomyces cerevisiae) and mammals, relatively little is known about the functional significance of these structures in plants. In this report, we characterize the Arabidopsis (Arabidopsis thaliana) phospholipid binding Synaptotagmin1 (SYT1) as a plant ortholog of the mammal extended synaptotagmins and yeast tricalbins families of ER-PM anchors. We propose that SYT1 functions at ER-PM contact sites because it displays a dual ER-PM localization, it is enriched in microtubule-depleted regions at the cell cortex, and it colocalizes with Vesicle-Associated Protein27-1, a known ER-PM marker. Furthermore, biochemical and physiological analyses indicate that SYT1 might function as an electrostatic phospholipid anchor conferring mechanical stability in plant cells. Together, the subcellular localization and functional characterization of SYT1 highlights a putative role of plant ER-PM contact site components in the cellular adaptation to environmental stresses.

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“…nucleus-vacuole junction | Vac8p | Nvj1p | membrane contact sites | crystal structure M embrane contact sites (MCSs) between subcellular compartments play pivotal roles in cellular processes such as cooperative lipid biosynthesis, ion homeostasis, and interorganellar trafficking of molecules in eukaryotic cells (1)(2)(3). MCSs are physically formed through dynamic and direct interactions between proteins that are located in two distinct subcompartments.…”

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confidence: 99%

Mechanistic insight into the nucleus–vacuole junction based on the Vac8p–Nvj1p crystal structure

Jeong

Park

Kim

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Formation of the nucleus-vacuole junction (NVJ) is mediated by direct interaction between the vacuolar protein Vac8p and the outer nuclear endoplasmic reticulum membrane protein Nvj1p. Herein we report the crystal structure of Vac8p bound to Nvj1p at 2.4-Å resolution. Vac8p comprises a flexibly connected N-terminal H1 helix followed by 12 armadillo repeats (ARMs) that form a right-handed superhelical structure. The extended 80-Å-long loop of Nvj1p specifically binds the highly conserved inner groove formed from ARM1−12 of Vac8p. Disruption of the Nvj1p-Vac8p interaction results in the loss of tight NVJs, which impairs piecemeal microautophagy of the nucleus in Saccharomyces cerevisiae. Vac8p cationic triad (Arg276, Arg317, and Arg359) motifs interacting with Nvj1p are also critical to the recognition of Atg13p, a key component of the cytoplasm-to-vacuole targeting (CVT) pathway, indicating competitive binding to Vac8p. Indeed, mutation of the cationic triad abolishes CVT of Ape1p in vivo. Combined with biochemical data, the crystal structure reveals a Vac8p homodimer formed from ARM1, and this self-association, likely regulated by the flexible H1 helix and the C terminus of Nvj1p, is critical for Vac8p cellular functions. M embrane contact sites (MCSs) between subcellular compartments play pivotal roles in cellular processes such as cooperative lipid biosynthesis, ion homeostasis, and interorganellar trafficking of molecules in eukaryotic cells (1-3). MCSs are physically formed through dynamic and direct interactions between proteins that are located in two distinct subcompartments. The nucleus-vacuole junction (NVJ), one of the best-characterized MCSs, is a physical contact site between perinuclear and vacuolar membranes and mediates essential cellular processes such as piecemeal microautophagy of the nucleus (PMN) and lipid biosynthesis in yeast (4, 5). PMN is a selective autophagic recycling process stimulated by carbon or nitrogen starvation through the target of rapamycin signaling pathway in Saccharomyces cerevisiae. Upon nutrient starvation, the region of the nucleus in the vicinity of NVJs invaginates into the vacuolar lumen and forms a bleb-like structure, which is released as a vesicle and eventually degraded by vacuolar hydrolases (5, 6). Because PMN occurs at the NVJ sites, their formation is essential for the initiation of the PMN process (7). NVJs are also involved in lipid metabolism by recruiting the two lipid-modifying enzymes, oxystereol-binding proteins homology (Osh1p) involved in nonvesicular lipid trafficking and the enoyl-CoA reductase Tsc13p that mediates the synthesis of verylong-chain fatty acids (8-11).Previous studies revealed that NVJs are generated by forming tight interactions between Vac8p, a vacuolar membrane protein, and Nvj1p, a nuclear membrane protein (12). Vac8p was initially found as a key player in vacuole inheritance by cooperating with Vac17p, actin, profilin, and Myo2p (13). In addition, Vac8p has a crucial role in mediating the processing of aminopeptidase I through in...

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Organization and function of membrane contact sites

Cited by 388 publications

References 175 publications

Arabidopsis AZI1 family proteins mediate signal mobilization for systemic defence priming

Arabidopsis AZI1 family proteins mediate signal mobilization for systemic defence priming

The Arabidopsis Synaptotagmin1 Is Enriched in Endoplasmic Reticulum-Plasma Membrane Contact Sites and Confers Cellular Resistance to Mechanical Stresses

Mechanistic insight into the nucleus–vacuole junction based on the Vac8p–Nvj1p crystal structure

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