Shaping the Endoplasmic Reticulum into a Social Network

Zhang, Hong; Hu, Junjie

doi:10.1016/j.tcb.2016.06.002

Cited by 106 publications

(103 citation statements)

References 82 publications

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“…In yeast cells, most of the COPII vesicles, which transport cargo from the ER to Golgi, form in the tubular ER (Okamoto et al, 2012). In addition, proteins residing in ER tubules often possess membrane-anchoring motifs that prefer high curvature (Zhang and Hu, 2016). These motifs include TMH, such as in RTNs or REEP/Yop1p proteins, or an amphipathic helix (APH) that may insert easily into a curved membrane and is found in many of the proteins identified here.…”

Section: Discussionmentioning

confidence: 99%

Quantitative proteomics reveal proteins enriched in tubular endoplasmic reticulum of Saccharomyces cerevisiae

Wang

et al. 2017

eLife

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The tubular network is a critical part of the endoplasmic reticulum (ER). The network is shaped by the reticulons and REEPs/Yop1p that generate tubules by inducing high membrane curvature, and the dynamin-like GTPases atlastin and Sey1p/RHD3 that connect tubules via membrane fusion. However, the specific functions of this ER domain are not clear. Here, we isolated tubule-based microsomes from Saccharomyces cerevisiae via classical cell fractionation and detergent-free immunoprecipitation of Flag-tagged Yop1p, which specifically localizes to ER tubules. In quantitative comparisons of tubule-derived and total microsomes, we identified a total of 79 proteins that were enriched in the ER tubules, including known proteins that organize the tubular ER network. Functional categorization of the list of proteins revealed that the tubular ER network may be involved in membrane trafficking, lipid metabolism, organelle contact, and stress sensing. We propose that affinity isolation coupled with quantitative proteomics is a useful tool for investigating ER functions.DOI: http://dx.doi.org/10.7554/eLife.23816.001

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Section: Discussionmentioning

confidence: 99%

Quantitative proteomics reveal proteins enriched in tubular endoplasmic reticulum of Saccharomyces cerevisiae

Wang

et al. 2017

eLife

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“…Novel membrane proteins are still being identified in for instance the endoplasmic reticulum (ER) and the plasma membrane (PM) [1–4], and insight in their topology is essential for unraveling their function [1,5]. Several experimental and software-based prediction methods are available for ER as well as other membrane proteins [6–11].…”

Section: Introductionmentioning

confidence: 99%

A Split-GFP Gateway Cloning System for Topology Analyses of Membrane Proteins in Plants

et al. 2017

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To understand the function of membrane proteins, it is imperative to know their topology. For such studies, a split green fluorescent protein (GFP) method is useful. GFP is barrel-shaped, consisting of 11 β-sheets. When the first ten β-sheets (GFP1-10) and the 11th β-sheet (GFP11) are expressed from separate genes they will self-assembly and reconstitute a fluorescent GFP protein. However, this will only occur when the two domains co-localize in the same cellular compartment. We have developed an easy-to-use Gateway vector set for determining on which side of the membrane the N- and C-termini are located. Two vectors were designed for making N- and C-terminal fusions between the membrane proteins-of-interest and GFP11, while another three plasmids were designed to express GFP1-10 in either the cytosol, the endoplasmic reticulum (ER) lumen or the apoplast. We tested functionality of the system by applying the vector set for the transmembrane domain, CNXTM, of the ER membrane protein, calnexin, after transient expression in Nicotiana benthamiana leaves. We observed GFP signal from the ER when we reciprocally co-expressed GFP11-CNXTM with GFP1-10-HDEL and CNXTM-GFP with cytosolic GFP1-10. The opposite combinations did not result in GFP signal emission. This test using the calnexin ER-membrane domain demonstrated its C-terminus to be in the cytosol and its N-terminus in the ER lumen. This result confirmed the known topology of calnexin, and we therefore consider this split-GFP system highly useful for ER membrane topology studies. Furthermore, the vector set provided is useful for detecting the topology of proteins on other membranes in the cell, which we confirmed for a plasma membrane syntaxin. The set of five Ti-plasmids are easily and efficiently used for Gateway cloning and transient transformation of N. benthamiana leaves.

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“…The endoplasmic reticulum (ER) is the largest organelle in the cell and serves multiple functions, including protein and lipid synthesis. Newly synthesized lipids must then be transported to other organelles, and an increasing number of reports highlight the importance of non‐vesicular transport of lipids at membrane contact sites (MCSs) (reviewed by). MCSs are regions where the membranes of 2 organelles are close together, typically within a distance of 30 nm.…”

Section: Introductionmentioning

confidence: 99%

Vacuole membrane protein 1 marks endoplasmic reticulum subdomains enriched in phospholipid synthesizing enzymes and is required for phosphoinositide distribution

Tábara

Vicente

Biazik

et al. 2018

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The multispanning membrane protein vacuole membrane protein 1 (VMP1) marks and regulates endoplasmic reticulum (ER)-domains associated with diverse ER-organelle membrane contact sites. A proportion of these domains associate with endosomes during their maturation and remodeling. We found that these VMP1 domains are enriched in choline/ethanolamine phosphotransferase and phosphatidylinositol synthase (PIS1), 2 ER enzymes required for the synthesis of various phospholipids. Interestingly, the lack of VMP1 impairs the formation of PIS1-enriched ER domains, suggesting a role in the distribution of phosphoinositides. In fact, depletion of VMP1 alters the distribution of PtdIns4P and proteins involved in the trafficking of PtdIns4P. Consistently, in these conditions, defects were observed in endosome trafficking and maturation as well as in Golgi morphology. We propose that VMP1 regulates the formation of ER domains enriched in lipid synthesizing enzymes. These domains might be necessary for efficient distribution of PtdIns4P and perhaps other lipid species. These findings, along with previous reports that involved VMP1 in regulating PtdIns3P during autophagy, expand the role of VMP1 in lipid trafficking and explain the pleiotropic effects observed in VMP1-deficient mammalian cells and other model systems.

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Shaping the Endoplasmic Reticulum into a Social Network

Cited by 106 publications

References 82 publications

Quantitative proteomics reveal proteins enriched in tubular endoplasmic reticulum of Saccharomyces cerevisiae

Quantitative proteomics reveal proteins enriched in tubular endoplasmic reticulum of Saccharomyces cerevisiae

A Split-GFP Gateway Cloning System for Topology Analyses of Membrane Proteins in Plants

Vacuole membrane protein 1 marks endoplasmic reticulum subdomains enriched in phospholipid synthesizing enzymes and is required for phosphoinositide distribution

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