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Kunduri G, Yuan C, Parthibane V, Nyswaner KM, Kanwar R, Nagashima K, Britt SG, Mehta N, Kotu V, Porterfield M, Tiemeyer M, Dolph PJ, Acharya U, Acharya JK. Phosphatidic acid phospholipase A1 mediates ER-Golgi transit of a family of G protein-coupled receptors. ACTA ACUST UNITED AC 2014; 206:79-95. [PMID: 25002678 PMCID: PMC4085702 DOI: 10.1083/jcb.201405020] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Cytosolic phosphatidic acid phospholipase A1 interacts with COPII protein family members and is required for the anterograde trafficking of GPCRs. The coat protein II (COPII)–coated vesicular system transports newly synthesized secretory and membrane proteins from the endoplasmic reticulum (ER) to the Golgi complex. Recruitment of cargo into COPII vesicles requires an interaction of COPII proteins either with the cargo molecules directly or with cargo receptors for anterograde trafficking. We show that cytosolic phosphatidic acid phospholipase A1 (PAPLA1) interacts with COPII protein family members and is required for the transport of Rh1 (rhodopsin 1), an N-glycosylated G protein–coupled receptor (GPCR), from the ER to the Golgi complex. In papla1 mutants, in the absence of transport to the Golgi, Rh1 is aberrantly glycosylated and is mislocalized. These defects lead to decreased levels of the protein and decreased sensitivity of the photoreceptors to light. Several GPCRs, including other rhodopsins and Bride of sevenless, are similarly affected. Our findings show that a cytosolic protein is necessary for transit of selective transmembrane receptor cargo by the COPII coat for anterograde trafficking.
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Affiliation(s)
- Govind Kunduri
- Laboratory of Cell and Developmental Signaling, National Cancer Institute, Frederick, MD 21702
| | - Changqing Yuan
- Laboratory of Cell and Developmental Signaling, National Cancer Institute, Frederick, MD 21702
| | - Velayoudame Parthibane
- Laboratory of Cell and Developmental Signaling, National Cancer Institute, Frederick, MD 21702
| | - Katherine M Nyswaner
- Laboratory of Cell and Developmental Signaling, National Cancer Institute, Frederick, MD 21702
| | - Ritu Kanwar
- Laboratory of Cell and Developmental Signaling, National Cancer Institute, Frederick, MD 21702
| | - Kunio Nagashima
- Electron Microscopy Laboratory, Frederick National Laboratory for Cancer Research, Frederick, MD 21702
| | - Steven G Britt
- Department of Cell and Developmental Biology, University of Colorado, Aurora, CO 80045
| | - Nickita Mehta
- Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602
| | - Varshika Kotu
- Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602
| | - Mindy Porterfield
- Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602
| | - Michael Tiemeyer
- Complex Carbohydrate Research Center, The University of Georgia, Athens, GA 30602
| | - Patrick J Dolph
- Department of Biological Sciences, Dartmouth College, Hanover, NH 03755
| | - Usha Acharya
- Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA 01605
| | - Jairaj K Acharya
- Laboratory of Cell and Developmental Signaling, National Cancer Institute, Frederick, MD 21702
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Secretion of a foreign protein from budding yeasts is enhanced by cotranslational translocation and by suppression of vacuolar targeting. Microb Cell Fact 2014; 13:125. [PMID: 25164324 PMCID: PMC4176846 DOI: 10.1186/s12934-014-0125-0] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Accepted: 08/17/2014] [Indexed: 01/31/2023] Open
Abstract
BACKGROUND Budding yeasts are often used to secrete foreign proteins, but the efficiency is variable. To identify roadblocks in the yeast secretory pathway, we used a monomeric superfolder GFP (msGFP) as a visual tracer in Saccharomyces cerevisiae and Pichia pastoris. RESULTS One roadblock for msGFP secretion is translocation into the ER. Foreign proteins are typically fused to the bipartite α-factor secretion signal, which consists of the signal sequence followed by the pro region. The α-factor signal sequence directs posttranslational translocation. For msGFP, posttranslational translocation is inefficient with the α-factor signal sequence alone but is stimulated by the pro region. This requirement for the pro region can be bypassed by using the Ost1 signal sequence, which has been shown to direct cotranslational translocation. A hybrid secretion signal consisting of the Ost1 signal sequence followed by the α-factor pro region drives efficient translocation followed by rapid ER export. A second roadblock for msGFP secretion in S. cerevisiae occurs during exit from the Golgi, when some of the msGFP molecules are diverted to the vacuole. Deletion of the sorting receptor Vps10 prevents vacuolar targeting of msGFP at the expense of missorting vacuolar hydrolases such as carboxypeptidase Y (CPY) to the culture medium. However, a truncation of Vps10 blocks vacuolar targeting of msGFP while permitting CPY to be sorted normally. CONCLUSIONS With budding yeasts, if the secretion or processing of a foreign protein is poor, we recommend two options. First, use the Ost1 signal sequence to achieve efficient entry into the secretory pathway while avoiding the processing issues associated with the α-factor pro region. Second, truncate Vps10 to suppress diversion to the vacuole. These insights obtained with msGFP highlight the value of applying cell biological methods to study yeast secretion.
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Abstract
Endoplasmic reticulum (ER) to Golgi trafficking is an essential step in sorting mature, correctly folded, processed and assembled proteins (cargo) from immature proteins and ER-resident proteins. However, the mechanisms governing trafficking selectivity, specificity and regulation are not yet fully understood. To date, three complementary mechanisms have been described that enable regulation of this trafficking step: ER retention of immature proteins in the ER; selective uptake of fully mature proteins into Golgi-bound vesicles; and retrieval from the Golgi of immature cargo that has erroneously exited the ER. Together, these three mechanisms allow incredible specificity and enable the cell to carry out protein quality control and regulate protein processing, oligomerization and expression. This review will focus on the current knowledge of selectivity mechanisms acting during the ER-to-Golgi sorting step and their significance in health and disease. The review will also highlight several key questions that have remained unanswered and discuss the future frontiers.
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Affiliation(s)
- Yosef Geva
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 761001, Israel
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot 761001, Israel.
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Low YS, Bircham PW, Maass DR, Atkinson PH. Kinetochore genes are required to fully activate secretory pathway expansion in S. cerevisiae under induced ER stress. MOLECULAR BIOSYSTEMS 2014; 10:1790-802. [PMID: 24722431 DOI: 10.1039/c3mb70414a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Basal ER stress occurs when proteins misfold in normal physiological conditions and are corrected by the unfolded protein response (UPR). Elevated ER stress occurs when misfolding is refractory as found in numerous diseases such as atherosclerosis, Type II diabetes and some cancers. In elevated ER stress it is unclear whether cells utilise the same or different networks of genes as in basal levels of ER stress. To probe this question, we used secretory pathway reporters Yip3p-GFP, Erv29p-GFP, Orm2p-GFP and UPREpr-GFP placed on the yeast deletion mutant array (DMA) genetic background. The reporter's expression levels, measured by automated microscopy, at basal versus elevated ER stress induced by the over-expression of CPY* were compared. A novel group of kinetochore genes (CTF19 complex) were found to be uniquely required for full induction of all four ER stress reporters in elevated stress. A follow-up reporter screen was developed by mating the ctf19Δ kinetochore gene deletion strain into the genome-wide XXXp-GFP tagged library then testing with over-expressed CPY*. This screen identified Bcy1p and Bfr1p as possible signalling points that down-regulate the UPR and secretory pathway when kinetochore proteins are absent under elevated stress conditions. Bfr1p appears to be a checkpoint that monitors the integrity of kinetochores at increased levels of ER stress. This study concludes that functional kinetochores are required for full activation of the secretory pathway in elevated ER stress and that the responses to basal and elevated levels of ER stress require different networks of genes.
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Affiliation(s)
- Yee S Low
- School of Biological Sciences, Victoria University of Wellington, Kelburn Parade, Wellington, New Zealand.
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Springer S, Malkus P, Borchert B, Wellbrock U, Duden R, Schekman R. Regulated Oligomerization Induces Uptake of a Membrane Protein into COPII Vesicles Independent of Its Cytosolic Tail. Traffic 2014; 15:531-45. [DOI: 10.1111/tra.12157] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2013] [Revised: 01/07/2014] [Accepted: 01/30/2014] [Indexed: 12/22/2022]
Affiliation(s)
| | - Per Malkus
- Department of Systems Biology; Harvard Medical School; Boston MA 02115 USA
| | - Britta Borchert
- Biochemistry and Cell Biology; Jacobs University Bremen; Bremen Germany
| | - Ursula Wellbrock
- Biochemistry and Cell Biology; Jacobs University Bremen; Bremen Germany
| | - Rainer Duden
- Centre for Structural and Cell Biology in Medicine, Institute of Biology; University of Lübeck; Lübeck Germany
| | - Randy Schekman
- Howard Hughes Medical Institute and Department of Molecular and Cell Biology; University of California, Berkeley; Berkeley CA 94720 USA
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56
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De Craene JO, Courte F, Rinaldi B, Fitterer C, Herranz MC, Schmitt-Keichinger C, Ritzenthaler C, Friant S. Study of the plant COPII vesicle coat subunits by functional complementation of yeast Saccharomyces cerevisiae mutants. PLoS One 2014; 9:e90072. [PMID: 24587212 PMCID: PMC3934973 DOI: 10.1371/journal.pone.0090072] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2013] [Accepted: 01/29/2014] [Indexed: 11/29/2022] Open
Abstract
The formation and budding of endoplasmic reticulum ER-derived vesicles depends on the COPII coat protein complex that was first identified in yeast Saccharomyces cerevisiae. The ER-associated Sec12 and the Sar1 GTPase initiate the COPII coat formation by recruiting the Sec23–Sec24 heterodimer following the subsequent recruitment of the Sec13–Sec31 heterotetramer. In yeast, there is usually one gene encoding each COPII protein and these proteins are essential for yeast viability, whereas the plant genome encodes multiple isoforms of all COPII subunits. Here, we used a systematic yeast complementation assay to assess the functionality of Arabidopsis thaliana COPII proteins. In this study, the different plant COPII subunits were expressed in their corresponding temperature-sensitive yeast mutant strain to complement their thermosensitivity and secretion phenotypes. Secretion was assessed using two different yeast cargos: the soluble α-factor pheromone and the membranous v-SNARE (vesicle-soluble NSF (N-ethylmaleimide-sensitive factor) attachment protein receptor) Snc1 involved in the fusion of the secretory vesicles with the plasma membrane. This complementation study allowed the identification of functional A. thaliana COPII proteins for the Sec12, Sar1, Sec24 and Sec13 subunits that could represent an active COPII complex in plant cells. Moreover, we found that AtSec12 and AtSec23 were co-immunoprecipitated with AtSar1 in total cell extract of 15 day-old seedlings of A. thaliana. This demonstrates that AtSar1, AtSec12 and AtSec23 can form a protein complex that might represent an active COPII complex in plant cells.
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Affiliation(s)
- Johan-Owen De Craene
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
| | - Fanny Courte
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
- Institut de Biologie Moléculaire des Plantes (IBMP), UPR2357 CNRS, Université de Strasbourg, Strasbourg, France
| | - Bruno Rinaldi
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
| | - Chantal Fitterer
- Institut de Biologie Moléculaire des Plantes (IBMP), UPR2357 CNRS, Université de Strasbourg, Strasbourg, France
| | - Mari Carmen Herranz
- Institut de Biologie Moléculaire des Plantes (IBMP), UPR2357 CNRS, Université de Strasbourg, Strasbourg, France
| | - Corinne Schmitt-Keichinger
- Institut de Biologie Moléculaire des Plantes (IBMP), UPR2357 CNRS, Université de Strasbourg, Strasbourg, France
| | - Christophe Ritzenthaler
- Institut de Biologie Moléculaire des Plantes (IBMP), UPR2357 CNRS, Université de Strasbourg, Strasbourg, France
| | - Sylvie Friant
- Department of Molecular and Cellular Genetics, UMR7156, Université de Strasbourg and CNRS, Strasbourg, France
- * E-mail:
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Shcherbik N. Golgi-mediated glycosylation determines residency of the T2 RNase Rny1p in Saccharomyces cerevisiae. Traffic 2013; 14:1209-27. [PMID: 24102742 DOI: 10.1111/tra.12122] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2013] [Revised: 09/16/2013] [Accepted: 09/18/2013] [Indexed: 12/20/2022]
Abstract
The role of glycosylation in the function of the T2 family of RNases is not well understood. In this work, we examined how glycosylation affects the progression of the T2 RNase Rny1p through the secretory pathway in Saccharomyces cerevisiae. We found that Rny1p requires entering into the ER first to become active and uses the adaptor protein Erv29p for packaging into COPII vesicles and transport to the Golgi apparatus. While inside the ER, Rny1p undergoes initial N-linked core glycosylation at four sites, N37, N70, N103 and N123. Rny1p transport to the Golgi results in the further attachment of high-glycans. Whereas modifications with glycans are dispensable for the nucleolytic activity of Rny1p, Golgi-mediated modifications are critical for its extracellular secretion. Failure of Golgi-specific glycosylation appears to direct Rny1p to the vacuole as an alternative destination and/or site of terminal degradation. These data reveal a previously unknown function of Golgi glycosylation in a T2 RNase as a sorting and secretion signal.
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Affiliation(s)
- Natalia Shcherbik
- Department of Cell Biology, School of Osteopathic Medicine, Rowan University, 2 Medical Center Drive, Stratford, NJ 08084, USA.
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Abstract
The secretory pathway is responsible for the synthesis, folding, and delivery of a diverse array of cellular proteins. Secretory protein synthesis begins in the endoplasmic reticulum (ER), which is charged with the tasks of correctly integrating nascent proteins and ensuring correct post-translational modification and folding. Once ready for forward traffic, proteins are captured into ER-derived transport vesicles that form through the action of the COPII coat. COPII-coated vesicles are delivered to the early Golgi via distinct tethering and fusion machineries. Escaped ER residents and other cycling transport machinery components are returned to the ER via COPI-coated vesicles, which undergo similar tethering and fusion reactions. Ultimately, organelle structure, function, and cell homeostasis are maintained by modulating protein and lipid flux through the early secretory pathway. In the last decade, structural and mechanistic studies have added greatly to the strong foundation of yeast genetics on which this field was built. Here we discuss the key players that mediate secretory protein biogenesis and trafficking, highlighting recent advances that have deepened our understanding of the complexity of this conserved and essential process.
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Delic M, Valli M, Graf AB, Pfeffer M, Mattanovich D, Gasser B. The secretory pathway: exploring yeast diversity. FEMS Microbiol Rev 2013; 37:872-914. [PMID: 23480475 DOI: 10.1111/1574-6976.12020] [Citation(s) in RCA: 141] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 02/14/2013] [Accepted: 02/17/2013] [Indexed: 12/11/2022] Open
Abstract
Protein secretion is an essential process for living organisms. In eukaryotes, this encompasses numerous steps mediated by several hundred cellular proteins. The core functions of translocation through the endoplasmic reticulum membrane, primary glycosylation, folding and quality control, and vesicle-mediated secretion are similar from yeasts to higher eukaryotes. However, recent research has revealed significant functional differences between yeasts and mammalian cells, and even among diverse yeast species. This review provides a current overview of the canonical protein secretion pathway in the model yeast Saccharomyces cerevisiae, highlighting differences to mammalian cells as well as currently unresolved questions, and provides a genomic comparison of the S. cerevisiae pathway to seven other yeast species where secretion has been investigated due to their attraction as protein production platforms, or for their relevance as pathogens. The analysis of Candida albicans, Candida glabrata, Kluyveromyces lactis, Pichia pastoris, Hansenula polymorpha, Yarrowia lipolytica, and Schizosaccharomyces pombe reveals that many - but not all - secretion steps are more redundant in S. cerevisiae due to duplicated genes, while some processes are even absent in this model yeast. Recent research obviates that even where homologous genes are present, small differences in protein sequence and/or differences in the regulation of gene expression may lead to quite different protein secretion phenotypes.
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Affiliation(s)
- Marizela Delic
- Department of Biotechnology, University of Natural Resources and Life Sciences (BOKU), Vienna, Austria; Austrian Centre of Industrial Biotechnology (ACIB GmbH), Vienna, Austria
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New putative chloroplast vesicle transport components and cargo proteins revealed using a bioinformatics approach: an Arabidopsis model. PLoS One 2013; 8:e59898. [PMID: 23573218 PMCID: PMC3613420 DOI: 10.1371/journal.pone.0059898] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Accepted: 02/19/2013] [Indexed: 11/23/2022] Open
Abstract
Proteins and lipids are known to be transported to targeted cytosolic compartments in vesicles. A similar system in chloroplasts is suggested to transfer lipids from the inner envelope to the thylakoids. However, little is known about both possible cargo proteins and the proteins required to build a functional vesicle transport system in chloroplasts. A few components have been suggested, but only one (CPSAR1) has a verified location in chloroplast vesicles. This protein is localized in the donor membrane (envelope) and vesicles, but not in the target membrane (thylakoids) suggesting it plays a similar role to a cytosolic homologue, Sar1, in the secretory pathway. Thus, we hypothesized that there may be more similarities, in addition to lipid transport, between the vesicle transport systems in the cytosol and chloroplast, i.e. similar vesicle transport components, possible cargo proteins and receptors. Therefore, using a bioinformatics approach we searched for putative chloroplast components in the model plant Arabidopsis thaliana, corresponding mainly to components of the cytosolic vesicle transport system that may act in coordination with previously proposed COPII chloroplast homologues. We found several additional possible components, supporting the notion of a fully functional vesicle transport system in chloroplasts. Moreover, we found motifs in thylakoid-located proteins similar to those of COPII vesicle cargo proteins, supporting the hypothesis that chloroplast vesicles may transport thylakoid proteins from the envelope to the thylakoid membrane. Several putative cargo proteins are involved in photosynthesis, thus we propose the existence of a novel thylakoid protein pathway that is important for construction and maintenance of the photosynthetic machinery.
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von Blume J, Alleaume AM, Kienzle C, Carreras-Sureda A, Valverde M, Malhotra V. Cab45 is required for Ca(2+)-dependent secretory cargo sorting at the trans-Golgi network. ACTA ACUST UNITED AC 2013; 199:1057-66. [PMID: 23266954 PMCID: PMC3529532 DOI: 10.1083/jcb.201207180] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The Golgi resident protein Cab45 is required for trans-Golgi network Ca2+ homeostasis and sorting of cargos that are destined for secretion. Ca2+ import into the lumen of the trans-Golgi network (TGN) by the secretory pathway calcium ATPase1 (SPCA1) is required for the sorting of secretory cargo. How is Ca2+ retained in the lumen of the Golgi, and what is its role in cargo sorting? We show here that a soluble, lumenal Golgi resident protein, Cab45, is required for SPCA1-dependent Ca2+ import into the TGN; it binds secretory cargo in a Ca2+-dependent reaction and is required for its sorting at the TGN.
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Affiliation(s)
- Julia von Blume
- Max Planck Institute for Biochemistry, 82152 Martinsried, Germany
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D'Arcangelo JG, Stahmer KR, Miller EA. Vesicle-mediated export from the ER: COPII coat function and regulation. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2013; 1833:2464-72. [PMID: 23419775 DOI: 10.1016/j.bbamcr.2013.02.003] [Citation(s) in RCA: 110] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Revised: 02/04/2013] [Accepted: 02/05/2013] [Indexed: 11/26/2022]
Abstract
Vesicle trafficking from the endoplasmic reticulum (ER) is a vital cellular process in all eukaryotes responsible for moving secretory cargoes from the ER to the Golgi apparatus. To accomplish this feat, the cell employs a set of conserved cytoplasmic coat proteins - the coat protein II (COPII) complex - that recruit cargo into nascent buds and deform the ER membrane to drive vesicle formation. While our understanding of COPII coat mechanics has developed substantially since its discovery, we have only recently begun to appreciate the factors that regulate this complex and, in turn, ER-to-Golgi trafficking. Here, we describe these factors and their influences on COPII vesicle formation. Properties intrinsic to the GTP cycle of the coat, as well as coat structure, have critical implications for COPII vesicle trafficking. Extrinsic factors in the cytosol can modulate COPII activity through direct interaction with the coat or with scaffolding components, or by changing composition of the ER membrane. Further, lumenal and membrane-bound cargoes and cargo receptors can influence COPII-mediated trafficking in equally profound ways. Together, these factors work in concert to ensure proper cargo movement in this first step of the secretory pathway. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
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Kakoi S, Yorimitsu T, Sato K. COPII machinery cooperates with ER-localized Hsp40 to sequester misfolded membrane proteins into ER-associated compartments. Mol Biol Cell 2013; 24:633-42. [PMID: 23303252 PMCID: PMC3583666 DOI: 10.1091/mbc.e12-08-0639] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Proteins that fail to fold in the endoplasmic reticulum (ER) are subjected to ER-associated degradation (ERAD). Certain transmembrane ERAD substrates are segregated into specialized ER subdomains, termed ER-associated compartments (ERACs), before targeting to ubiquitin-proteasome degradation. The traffic-independent function of several proteins involved in COPII-mediated ER-to-Golgi transport have been implicated in the segregation of exogenously expressed human cystic fibrosis transmembrane conductance regulator (CFTR) into ERACs in Saccharomyces cerevisiae. Here we focus on the properties of COPII components in the sequestration of enhanced green fluorescent protein (EGFP)-CFTR into ERACs. It has been demonstrated that the temperature-sensitive growth defects in many COPII mutants can be suppressed by overexpressing other genes involved in COPII vesicle formation. However, we show that these suppression abilities are not always correlated with the ability to rescue the ERAC formation defect, suggesting that COPII-mediated EGFP-CFTR entry into ERACs is independent of its ER-to-Golgi trafficking function. In addition to COPII machinery, we find that ER-associated Hsp40s are also involved in the sequestration process by directly interacting with EGFP-CFTR. COPII components and ER-associated Hsp40, Hlj1p, act in the same pathway to sequester EGFP-CFTR into ERACs. Our findings point to an as-yet-undefined role of COPII proteins in the formation of ERACs.
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Affiliation(s)
- Shogo Kakoi
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan
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Chen YT, Tsai MS, Yang TL, Ku AT, Huang KH, Huang CY, Chou FJ, Fan HH, Hong JB, Yen ST, Wang WL, Lin CC, Hsu YC, Su KY, Su IC, Jang CW, Behringer RR, Favaro R, Nicolis SK, Chien CL, Lin SW, Yu IS. R26R-GR: a Cre-activable dual fluorescent protein reporter mouse. PLoS One 2012; 7:e46171. [PMID: 23049968 PMCID: PMC3458011 DOI: 10.1371/journal.pone.0046171] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2012] [Accepted: 08/30/2012] [Indexed: 12/17/2022] Open
Abstract
Green fluorescent protein (GFP) and its derivatives are the most widely used molecular reporters for live cell imagining. The development of organelle-specific fusion fluorescent proteins improves the labeling resolution to a higher level. Here we generate a R26 dual fluorescent protein reporter mouse, activated by Cre-mediated DNA recombination, labeling target cells with a chromatin-specific enhanced green fluorescence protein (EGFP) and a plasma membrane-anchored monomeric cherry fluorescent protein (mCherry). This dual labeling allows the visualization of mitotic events, cell shapes and intracellular vesicle behaviors. We expect this reporter mouse to have a wide application in developmental biology studies, transplantation experiments as well as cancer/stem cell lineage tracing.
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Affiliation(s)
- You-Tzung Chen
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Ming-Shian Tsai
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Tsung-Lin Yang
- Department of Otolaryngology, National Taiwan University Hospital and College of Medicine, Taipei, Taiwan
| | - Amy Tsu Ku
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Ke-Han Huang
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Cheng-Yen Huang
- The First Core Laboratory, Branch Office of Medical Research and Development, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Fu-Ju Chou
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Hsiang-Hsuan Fan
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Jin-Bon Hong
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Shuo-Ting Yen
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Wei-Le Wang
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Chang-Ching Lin
- Graduate Institute of Medical Genomics and Proteomics, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Yu-Chen Hsu
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University College of Medicine, Taipei, Taiwan
- Division of Genomic Medicine, NTU Center of Genomic Medicine, National Taiwan University, Taipei, Taiwan
| | - Kang-Yi Su
- Division of Genomic Medicine, NTU Center of Genomic Medicine, National Taiwan University, Taipei, Taiwan
- Institute of Statistical Science, Academia Sinica, Taipei, Taiwan
| | - I-Chang Su
- Graduate Institute of Clinical Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Chuan-Wei Jang
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Genetics and Center for Stem Cell and Developmental Biology, University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Richard R. Behringer
- Program in Developmental Biology, Baylor College of Medicine, Houston, Texas, United States of America
- Department of Genetics and Center for Stem Cell and Developmental Biology, University of Texas MD Anderson Cancer Center, Houston, Texas, United States of America
| | - Rebecca Favaro
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano, Italy
| | - Silvia K. Nicolis
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, Milano, Italy
| | - Chung-Liang Chien
- Graduate Institute of Anatomy and Cell Biology, National Taiwan University College of Medicine, Taipei, Taiwan
| | - Shu-Wha Lin
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University College of Medicine, Taipei, Taiwan
- Department of Laboratory Medicine, National Taiwan University Hospital, Taipei, Taiwan
- * E-mail: (S-WL); (I-SY)
| | - I-Shing Yu
- Transgenic Mouse Model Core Facility of the National Research Program for Genomic Medicine, National Taiwan University College of Medicine, Taipei, Taiwan
- * E-mail: (S-WL); (I-SY)
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Yoshibori M, Yorimitsu T, Sato K. Involvement of the penta-EF-hand protein Pef1p in the Ca2+-dependent regulation of COPII subunit assembly in Saccharomyces cerevisiae. PLoS One 2012; 7:e40765. [PMID: 22792405 PMCID: PMC3394733 DOI: 10.1371/journal.pone.0040765] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2012] [Accepted: 06/13/2012] [Indexed: 11/24/2022] Open
Abstract
Although it is well established that the coat protein complex II (COPII) mediates the transport of proteins and lipids from the endoplasmic reticulum (ER) to the Golgi apparatus, the regulation of the vesicular transport event and the mechanisms that act to counterbalance the vesicle flow between the ER and Golgi are poorly understood. In this study, we present data indicating that the penta-EF-hand Ca2+-binding protein Pef1p directly interacts with the COPII coat subunit Sec31p and regulates COPII assembly in Saccharomyces cerevisiae. ALG-2, a mammalian homolog of Pef1p, has been shown to interact with Sec31A in a Ca2+-dependent manner and to have a role in stabilizing the association of the Sec13/31 complex with the membrane. However, Pef1p displayed reversed Ca2+ dependence for Sec13/31p association; only the Ca2+-free form of Pef1p bound to the Sec13/31p complex. In addition, the influence on COPII coat assembly also appeared to be reversed; Pef1p binding acted as a kinetic inhibitor to delay Sec13/31p recruitment. Our results provide further evidence for a linkage between Ca2+-dependent signaling and ER-to-Golgi trafficking, but its mechanism of action in yeast seems to be different from the mechanism reported for its mammalian homolog ALG-2.
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Affiliation(s)
- Mariko Yoshibori
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo, Japan
| | - Tomohiro Yorimitsu
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo, Japan
| | - Ken Sato
- Department of Life Sciences, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Meguro-ku, Tokyo, Japan
- * E-mail:
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66
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Herzig Y, Sharpe HJ, Elbaz Y, Munro S, Schuldiner M. A systematic approach to pair secretory cargo receptors with their cargo suggests a mechanism for cargo selection by Erv14. PLoS Biol 2012; 10:e1001329. [PMID: 22629230 PMCID: PMC3358343 DOI: 10.1371/journal.pbio.1001329] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2012] [Accepted: 04/03/2012] [Indexed: 11/29/2022] Open
Abstract
A systematic approach to visualize proteins exiting the endoplasmic reticulum paired with their cargo receptors identifies novel cargo for known receptors and reveals the mechanism of one conserved receptor, Erv14. The endoplasmic reticulum (ER) is the site of synthesis of secreted and membrane proteins. To exit the ER, proteins are packaged into COPII vesicles through direct interaction with the COPII coat or aided by specific cargo receptors. Despite the fundamental role of such cargo receptors in protein traffic, only a few have been identified; their cargo spectrum is unknown and the signals they recognize remain poorly understood. We present here an approach we term “PAIRS” (pairing analysis of cargo receptors), which combines systematic genetic manipulations of yeast with automated microscopy screening, to map the spectrum of cargo for a known receptor or to uncover a novel receptor for a particular cargo. Using PAIRS we followed the fate of ∼150 cargos on the background of mutations in nine putative cargo receptors and identified novel cargo for most of these receptors. Deletion of the Erv14 cargo receptor affected the widest range of cargo. Erv14 substrates have a wide array of functions and structures; however, they are all membrane-spanning proteins of the late secretory pathway or plasma membrane. Proteins residing in these organelles have longer transmembrane domains (TMDs). Detailed examination of one cargo supported the hypothesis that Erv14 dependency reflects the length rather than the sequence of the TMD. The PAIRS approach allowed us to uncover new cargo for known cargo receptors and to obtain an unbiased look at specificity in cargo selection. Obtaining the spectrum of cargo for a cargo receptor allows a novel perspective on its mode of action. The rules that appear to guide Erv14 substrate recognition suggest that sorting of membrane proteins at multiple points in the secretory pathway could depend on the physical properties of TMDs. Such a mechanism would allow diverse proteins to utilize a few receptors without the constraints of evolving location-specific sorting motifs. All cells sense their environment, respond to it, and communicate with neighboring cells. To perform these functions, cells use an impressive array of proteins that they display on their surface membranes and secrete into their external environment. Newly synthesized proteins destined for the surface of nucleated cells, or to be secreted into the environment must enter the secretory pathway through the endoplasmic reticulum. Those that reside there remain behind, but most leave for their next destination as cargo proteins in lipid vesicles. To be packaged into vesicles, many of them require a “cargo receptor,” which recognizes and tethers specific cargo proteins in the vesicles. Our study takes a systematic approach to identify the range of cargo proteins that bind to each of the known receptors in yeast. By using this approach, we both discover new cargo for known cargo receptors and delineate the rule that governs cargo selection for one cargo receptor, Erv14. Thus, our study demonstrates a novel approach to identify the cargo for any receptor or to discover new cargo receptors.
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Affiliation(s)
- Yonatan Herzig
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | | | - Yael Elbaz
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Sean Munro
- MRC Laboratory of Molecular Biology, Cambridge, United Kingdom
- * E-mail: (SM); (MS)
| | - Maya Schuldiner
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
- * E-mail: (SM); (MS)
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67
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Fujii Y, Shiota M, Ohkawa Y, Baba A, Wanibuchi H, Kinashi T, Kurosaki T, Baba Y. Surf4 modulates STIM1-dependent calcium entry. Biochem Biophys Res Commun 2012; 422:615-20. [PMID: 22609200 DOI: 10.1016/j.bbrc.2012.05.037] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Accepted: 05/09/2012] [Indexed: 10/28/2022]
Abstract
Store-operated Ca(2+) entry (SOCE) is crucial for various physiological responses in immune cells. Although it is known that STIM1 relocates into discrete puncta juxtaposed to the plasma membrane to initiate SOCE, the machinery modulating the function of STIM1 remains unclear. We explored to find its modulators using affinity purification for STIM1-binding proteins and identified surfeit locus protein 4 (Surf4). Surf4 associated with STIM1 in the endoplasmic reticulum. Deletion of Surf4 in DT40 B cells resulted in marked increase of SOCE and facilitation of STIM1 clustering upon store-depletion. These findings suggest the modulatory function of Surf4 for STIM1-mediated SOCE.
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Affiliation(s)
- Yoko Fujii
- Laboratory for Lymphocyte Differentiation, RIKEN Research Center for Allergy and Immunology, Yokohama, Kanagawa 230-0045, Japan
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68
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Abstract
Multiple diseases, hematologic and nonhematologic, result from defects in the early secretory pathway. Congenital dyserythropoietic anemia type II (CDAII) and combined deficiency of coagulation factors V and VIII (F5F8D) are the 2 known hematologic diseases that result from defects in the endoplasmic reticulum (ER)-to-Golgi transport system. CDAII is caused by mutations in the SEC23B gene, which encodes a core component of the coat protein complex II (COPII). F5F8D results from mutations in either LMAN1 (lectin mannose-binding protein 1) or MCFD2 (multiple coagulation factor deficiency protein 2), which encode the ER cargo receptor complex LMAN1-MCFD2. These diseases and their molecular pathogenesis are the focus of this review.
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69
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Wang Q, Feng H, Zheng P, Shen B, Chen L, Liu L, Liu X, Hao Q, Wang S, Chen J, Teng J. The intracellular transport and secretion of calumenin-1/2 in living cells. PLoS One 2012; 7:e35344. [PMID: 22514732 PMCID: PMC3325945 DOI: 10.1371/journal.pone.0035344] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 03/14/2012] [Indexed: 01/05/2023] Open
Abstract
Calumenin isoforms 1 and 2 (calu-1/2), encoded by the CALU gene, belong to the CREC protein family. Calu-1/2 proteins are secreted into the extracellular space, but the secretory process and regulatory mechanism are largely unknown. Here, using a time-lapse imaging system, we visualized the intracellular transport and secretory process of calu-1/2-EGFP after their translocation into the ER lumen. Interestingly, we observed that an abundance of calu-1/2-EGFP accumulated in cellular processes before being released into the extracellular space, while only part of calu-1/2-EGFP proteins were secreted directly after attaching to the cell periphery. Moreover, we found the secretion of calu-1/2-EGFP required microtubule integrity, and that calu-1/2-EGFP-containing vesicles were transported by the motor proteins Kif5b and cytoplasmic dynein. Finally, we determined the export signal of calu-1/2-EGFP (amino acid positions 20–46) and provided evidence that the asparagine at site 131 was indispensable for calu-1/2-EGFP stabilization. Taken together, we provide a detailed picture of the intracellular transport of calu-1/2-EGFP, which facilitates our understanding of the secretory mechanism of calu-1/2.
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Affiliation(s)
- Qiao Wang
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
| | - Hui Feng
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
| | - Pengli Zheng
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
| | - Birong Shen
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
| | - Liang Chen
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
| | - Lin Liu
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
| | - Xiao Liu
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
| | - Qingsong Hao
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
| | - Shunchang Wang
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
| | - Jianguo Chen
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
- Center for Theoretical Biology, Peking University, Beijing, China
| | - Junlin Teng
- State Key Laboratory of Bio-membrane and Membrane Bio-engineering and Key Laboratory of Cell Proliferation and Differentiation of the Ministry of Education, College of Life Sciences, Peking University, Beijing, China
- * E-mail:
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70
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Copic A, Latham CF, Horlbeck MA, D'Arcangelo JG, Miller EA. ER cargo properties specify a requirement for COPII coat rigidity mediated by Sec13p. Science 2012; 335:1359-62. [PMID: 22300850 DOI: 10.1126/science.1215909] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Eukaryotic secretory proteins exit the endoplasmic reticulum (ER) via transport vesicles generated by the essential coat protein complex II (COPII) proteins. The outer coat complex, Sec13-Sec31, forms a scaffold that is thought to enforce curvature. By exploiting yeast bypass-of-sec-thirteen (bst) mutants, where Sec13p is dispensable, we probed the relationship between a compromised COPII coat and the cellular context in which it could still function. Genetic and biochemical analyses suggested that Sec13p was required to generate vesicles from membranes that contained asymmetrically distributed cargoes that were likely to confer opposing curvature. Thus, Sec13p may rigidify the COPII cage and increase its membrane-bending capacity; this function could be bypassed when a bst mutation renders the membrane more deformable.
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Affiliation(s)
- Alenka Copic
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
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71
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Izawa T, Nagai H, Endo T, Nishikawa SI. Yos9p and Hrd1p mediate ER retention of misfolded proteins for ER-associated degradation. Mol Biol Cell 2012; 23:1283-93. [PMID: 22298424 PMCID: PMC3315801 DOI: 10.1091/mbc.e11-08-0722] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Yos9p is involved in ER-associated degradation (ERAD) of misfolded glycoproteins. This study shows that Yos9p is required for ER retention of ERAD substrates by targeting them to the Hrd1p E3 ligase. This ER retention is independent of the glycan degradation signal on substrates and is separable from the later degradation step. The endoplasmic reticulum (ER) has an elaborate quality control system, which retains misfolded proteins and targets them to ER-associated protein degradation (ERAD). To analyze sorting between ER retention and ER exit to the secretory pathway, we constructed fusion proteins containing both folded carboxypeptidase Y (CPY) and misfolded mutant CPY (CPY*) units. Although the luminal Hsp70 chaperone BiP interacts with the fusion proteins containing CPY* with similar efficiency, a lectin-like ERAD factor Yos9p binds to them with different efficiency. Correlation between efficiency of Yos9p interactions and ERAD of these fusion proteins indicates that Yos9p but not BiP functions in the retention of misfolded proteins for ERAD. Yos9p targets a CPY*-containing ERAD substrate to Hrd1p E3 ligase, thereby causing ER retention of the misfolded protein. This ER retention is independent of the glycan degradation signal on the misfolded protein and operates even when proteasomal degradation is inhibited. These results collectively indicate that Yos9p and Hrd1p mediate ER retention of misfolded proteins in the early stage of ERAD, which constitutes a process separable from the later degradation step.
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Affiliation(s)
- Toshiaki Izawa
- Department of Chemistry, Graduate School of Science, Nagoya University, Chikusa-ku, Nagoya, Japan
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72
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Gupta GS. L-Type Lectins in ER-Golgi Intermediate Compartment. ANIMAL LECTINS: FORM, FUNCTION AND CLINICAL APPLICATIONS 2012. [PMCID: PMC7123055 DOI: 10.1007/978-3-7091-1065-2_7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 10/29/2022]
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73
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Ruiz-May E, Kim SJ, Brandizzi F, Rose JKC. The secreted plant N-glycoproteome and associated secretory pathways. FRONTIERS IN PLANT SCIENCE 2012; 3:117. [PMID: 22685447 PMCID: PMC3368311 DOI: 10.3389/fpls.2012.00117] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 05/15/2012] [Indexed: 05/14/2023]
Abstract
N-Glycosylation is a common form of eukaryotic protein post-translational modification, and one that is particularly prevalent in plant cell wall proteins. Large scale and detailed characterization of N-glycoproteins therefore has considerable potential in better understanding the composition and functions of the cell wall proteome, as well as those proteins that reside in other compartments of the secretory pathway. While there have been numerous studies of mammalian and yeast N-glycoproteins, less is known about the population complexity, biosynthesis, structural variation, and trafficking of their plant counterparts. However, technical developments in the analysis of glycoproteins and the structures the glycans that they bear, as well as valuable comparative analyses with non-plant systems, are providing new insights into features that are common among eukaryotes and those that are specific to plants, some of which may reflect the unique nature of the plant cell wall. In this review we present an overview of the current knowledge of plant N-glycoprotein synthesis and trafficking, with particular reference to those that are cell wall localized.
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Affiliation(s)
- Eliel Ruiz-May
- Department of Plant Biology, Cornell UniversityIthaca, NY, USA
| | - Sang-Jin Kim
- Great Lakes Bioenergy Research Center, Michigan State UniversityEast Lansing, MI, USA
- DOE Plant Research Laboratory, Michigan State UniversityEast Lansing, MI, USA
| | - Federica Brandizzi
- Great Lakes Bioenergy Research Center, Michigan State UniversityEast Lansing, MI, USA
- DOE Plant Research Laboratory, Michigan State UniversityEast Lansing, MI, USA
| | - Jocelyn K. C. Rose
- Department of Plant Biology, Cornell UniversityIthaca, NY, USA
- *Correspondence: Jocelyn K. C. Rose, Department of Plant Biology, Cornell University, 412 Mann Library Building, Ithaca, NY 14853 USA. e-mail:
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74
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Hsu CL, Prasad R, Blackman C, Ng DTW. Endoplasmic reticulum stress regulation of the Kar2p/BiP chaperone alleviates proteotoxicity via dual degradation pathways. Mol Biol Cell 2011; 23:630-41. [PMID: 22190740 PMCID: PMC3279391 DOI: 10.1091/mbc.e11-04-0297] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
ETOC: A procedure to uncouple the highly conserved target gene Kar2/BiP from UPR regulation is used to show that the primary function of its induction is to mediate the disposal of misfolded proteins that would otherwise be toxic. The unfolded protein response (UPR) monitors and maintains protein homeostasis in the endoplasmic reticulum (ER). In budding yeast, the UPR is a transcriptional regulatory pathway that is quiescent under normal conditions. Under conditions of acute ER stress, activation of UPR targets is essential for cell viability. How individual target genes contribute to stress tolerance is unclear. Uncovering these roles is hampered because most targets also play important functions in the absence of stress. To differentiate stress-specific roles from everyday functions, a single target gene was uncoupled from UPR control by eliminating its UPR-specific regulatory element. Through this approach, the UPR remains intact, aside from its inability to induce the designated target. Applying the strategy to the major ER chaperone Kar2p/BiP revealed the physiological function of increasing its cellular concentration. Despite hundreds of target genes under UPR control, we show that activation of KAR2 is indispensable to alleviate some forms of ER stress. Specifically, activation is essential to dispose misfolded proteins that are otherwise toxic. Surprisingly, induced BiP/Kar2p molecules are dedicated to alleviating stress. The inability to induce KAR2 under stress had no effect on its known housekeeping functions.
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Affiliation(s)
- Chia-Ling Hsu
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604
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75
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Matsuzaki F, Shirane M, Matsumoto M, Nakayama KI. Protrudin serves as an adaptor molecule that connects KIF5 and its cargoes in vesicular transport during process formation. Mol Biol Cell 2011; 22:4602-20. [PMID: 21976701 PMCID: PMC3226478 DOI: 10.1091/mbc.e11-01-0068] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 09/26/2011] [Accepted: 09/28/2011] [Indexed: 01/22/2023] Open
Abstract
Neurons are highly polarized cells with long neurites. Vesicular transport is required for neurite extension. We recently identified protrudin as a key regulator of vesicular transport during neurite extension. Expression of protrudin in nonneuronal cells thus induces formation of neurite-like membrane protrusions. We adopted a proteomics approach to identify proteins that associate with protrudin. Among the protrudin-associated proteins, including many with a function related to intracellular trafficking, we focused on KIF5, a motor protein that mediates anterograde vesicular transport in neurons. A coimmunoprecipitation assay confirmed that endogenous protrudin and KIF5 interact in mouse brain. Overexpression of KIF5 induced the formation of membrane protrusions in HeLa cells, reminiscent of the effect of protrudin overexpression. Forced expression of both protrudin and KIF5 promoted protrusion extension in a synergistic manner, whereas depletion of either protein attenuated protrusion formation. Protrudin facilitated the interaction of KIF5 with Rab11, VAP-A and -B, Surf4, and RTN3, suggesting that protrudin serves as an adaptor protein and that the protrudin-KIF5 complex contributes to the transport of these proteins in neurons. Given that mutation of protrudin or KIF5 is a cause of human hereditary spastic paraplegia, the protrudin-KIF5 axis appears to be integral to neuronal function.
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Affiliation(s)
- Fumiko Matsuzaki
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan; CREST, Japan Science and Technology Corporation (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Michiko Shirane
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan; CREST, Japan Science and Technology Corporation (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Masaki Matsumoto
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan; CREST, Japan Science and Technology Corporation (JST), Kawaguchi, Saitama 332-0012, Japan
| | - Keiichi I. Nakayama
- Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Fukuoka 812-8582, Japan; CREST, Japan Science and Technology Corporation (JST), Kawaguchi, Saitama 332-0012, Japan
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76
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Abstract
Analysis of the human genome reveals that approximately a third of all open reading frames code for proteins that enter the endoplasmic reticulum (ER), demonstrating the importance of this organelle for global protein maturation. The path taken by a polypeptide through the secretory pathway starts with its translocation across or into the ER membrane. It then must fold and be modified correctly in the ER before being transported via the Golgi apparatus to the cell surface or another destination. Being physically segregated from the cytosol means that the ER lumen has a distinct folding environment. It contains much of the machinery for fulfilling the task of protein production, including complex pathways for folding, assembly, modification, quality control, and recycling. Importantly, the compartmentalization means that several modifications that do not occur in the cytosol, such as glycosylation and extensive disulfide bond formation, can occur to secreted proteins to enhance their stability before their exposure to the extracellular milieu. How these various machineries interact during the normal pathway of folding and protein secretion is the subject of this review.
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Affiliation(s)
- Ineke Braakman
- Cellular Protein Chemistry, Faculty of Science, Utrecht University, Utrecht, The Netherlands.
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77
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Fujita M, Watanabe R, Jaensch N, Romanova-Michaelides M, Satoh T, Kato M, Riezman H, Yamaguchi Y, Maeda Y, Kinoshita T. Sorting of GPI-anchored proteins into ER exit sites by p24 proteins is dependent on remodeled GPI. ACTA ACUST UNITED AC 2011; 194:61-75. [PMID: 21727194 PMCID: PMC3135397 DOI: 10.1083/jcb.201012074] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
p24 complexes act as cargo receptors for sorting GPI-anchored proteins into COPII vesicles. Glycosylphosphatidylinositol (GPI) anchoring of proteins is a posttranslational modification occurring in the endoplasmic reticulum (ER). After GPI attachment, proteins are transported by coat protein complex II (COPII)-coated vesicles from the ER. Because GPI-anchored proteins (GPI-APs) are localized in the lumen, they cannot interact with cytosolic COPII components directly. Receptors that link GPI-APs to COPII are thought to be involved in efficient packaging of GPI-APs into vesicles; however, mechanisms of GPI-AP sorting are not well understood. Here we describe two remodeling reactions for GPI anchors, mediated by PGAP1 and PGAP5, which were required for sorting of GPI-APs to ER exit sites. The p24 family of proteins recognized the remodeled GPI-APs and sorted them into COPII vesicles. Association of p24 proteins with GPI-APs was pH dependent, which suggests that they bind in the ER and dissociate in post-ER acidic compartments. Our results indicate that p24 complexes act as cargo receptors for correctly remodeled GPI-APs to be sorted into COPII vesicles.
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Affiliation(s)
- Morihisa Fujita
- Research Institute for Microbial Diseases and WPI Immunology Frontier Research Center, Osaka University, Suita, Osaka 565-0871, Japan
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78
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Suntio T, Shiryaev SA, Makarow M. ATPase activity of a yeast secretory glycoprotein allows ER exit during inactivation of COPII components Sec24p and Sec13p. Yeast 2011; 28:453-65. [PMID: 21446055 DOI: 10.1002/yea.1850] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2010] [Accepted: 02/15/2011] [Indexed: 11/07/2022] Open
Abstract
Proteins exit the endoplasmic reticulum (ER) in vesicles pinching off from the membrane at sites covered by the COPII coat, which consists of Sec23/24p and Sec13/31p. We have shown that the glycoprotein Hsp150 exits the ER in the absence of Sec13p or any member of the Sec24p family. The determinant responsible for this resides in the C-terminal domain of Hsp150 (CTD). Here, A- and B-type Walker motifs were identified in the CTD. Authentic Hsp150 from the yeast culture medium, as well as Hsp150 and the CTD fragment produced in Escherichia coli, exhibited ATPase activity nearly three times higher than the published activity of the ER chaperone Kar2p/BiP. Deletion of the Walker motif, and a K335A mutation in it, abolished the ATPase activity. Hsp150 homologues Pir3p and Pir4p, differing in critical amino acids of the Walker motif, also lacked ATPase activity. Unexpectedly, inactivation of the ATPase activity blocked ER exit of Hsp150 in the absence of Sec24p or Sec13p function, whereas secretion in normal cells was not compromised. To our knowledge this is the first documentation of the ATPase activity of a protein serving an intracellular transport function.
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Affiliation(s)
- Taina Suntio
- Programme in Cellular Biotechnology, Institute of Biotechnology, University of Helsinki, Finland.
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79
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Abstract
Trafficking of newly synthesized cargo through the early secretory pathway defines and maintains the intracellular organization of eukaryotic cells as well as the organization of tissues and organs. The importance of this pathway is underlined by the increasing number of mutations in key components of the ER export machinery that are causative of a diversity of human diseases. Here we discuss the molecular mechanisms that dictate cargo selection during vesicle budding. While, in vitro reconstitution assays, unicellular organisms such as budding yeast, and mammalian cell culture still have much to offer in terms of gaining a full understanding of the molecular basis for secretory cargo export, such assays have to date been limited to analysis of smaller, freely diffusible cargoes. The export of large macromolecular complexes from the ER such as collagens (up to 300 nm) or lipoproteins (~500 nm) presents a clear problem in terms of maintaining both selectivity and efficiency of export. It has also become clear that in order to translate our knowledge of the molecular basis for ER export to a full understanding of the implications for normal development and disease progression, the use of metazoan models is essential. Combined, these approaches are now starting to shed light not only on the mechanisms of macromolecular cargo export from the ER but also reveal the implications of failure of this process to human development and disease.
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Affiliation(s)
- Katy Schmidt
- Cell Biology Laboratories, School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol, UK.
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80
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Protein Quality Control, Retention, and Degradation at the Endoplasmic Reticulum. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2011; 292:197-280. [DOI: 10.1016/b978-0-12-386033-0.00005-0] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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81
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Kawaguchi S, Hsu CL, Ng DTW. Interplay of substrate retention and export signals in endoplasmic reticulum quality control. PLoS One 2010; 5:e15532. [PMID: 21151492 PMCID: PMC2991357 DOI: 10.1371/journal.pone.0015532] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2010] [Accepted: 10/05/2010] [Indexed: 11/19/2022] Open
Abstract
Background Endoplasmic reticulum (ER) quality control mechanisms are part of a comprehensive system to manage cell stress. The flux of molecules is monitored to retain folding intermediates and target misfolded molecules to ER-associated degradation (ERAD) pathways. The mechanisms of sorting remain unclear. While some proteins are retained statically, the classical model substrate CPY* is found in COPII transport vesicles, suggesting a retrieval mechanism for retention. However, its management can be even more dynamic. If ERAD is saturated under stress, excess CPY* traffics to the vacuole for degradation. These observations suggest that misfolded proteins might display different signals for their management. Methodology/Principal Findings Here, we report the existence of a functional ER exit signal in the pro-domain of CPY*. Compromising its integrity causes ER retention through exclusion from COPII vesicles. The signal co-exists with other signals used for retention and degradation. Physiologically, the export signal is important for stress tolerance. Disabling it converts a benign protein into one that is intrinsically cytotoxic. Conclusions/Significance These data reveal the remarkable interplay between opposing signals embedded within ERAD substrate molecules and the mechanisms that decipher them. Our findings demonstrate the diversity of mechanisms deployed for protein quality control and maintenance of protein homeostasis.
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Affiliation(s)
- Shinichi Kawaguchi
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore, Singapore
| | - Chia-Ling Hsu
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore, Singapore
| | - Davis T. W. Ng
- Temasek Life Sciences Laboratory, National University of Singapore, Singapore, Singapore
- Department of Biological Sciences, National University of Singapore, Singapore, Singapore
- * E-mail:
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82
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Abstract
Estimates based on proteomic analyses indicate that a third of translated proteins in eukaryotic genomes enter the secretory pathway. After folding and assembly of nascent secretory proteins in the endoplasmic reticulum (ER), the coat protein complex II (COPII) selects folded cargo for export in membrane-bound vesicles. To accommodate the great diversity in secretory cargo, protein sorting receptors are required in a number of instances for efficient ER export. These transmembrane sorting receptors couple specific secretory cargo to COPII through interactions with both cargo and coat subunits. After incorporation into COPII transport vesicles, protein sorting receptors release bound cargo in pre-Golgi or Golgi compartments, and receptors are then recycled back to the ER for additional rounds of cargo export. Distinct types of protein sorting receptors that recognize carbohydrate and/or polypeptide signals in secretory cargo have been characterized. Our current understanding of the molecular mechanisms underlying cargo receptor function are described.
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Affiliation(s)
- Julia Dancourt
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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83
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Wilson JD, Barlowe C. Yet1p and Yet3p, the yeast homologs of BAP29 and BAP31, interact with the endoplasmic reticulum translocation apparatus and are required for inositol prototrophy. J Biol Chem 2010; 285:18252-61. [PMID: 20378542 DOI: 10.1074/jbc.m109.080382] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The mammalian B-cell receptor-associated proteins of 29 and 31 kDa (BAP29 and BAP31) are conserved integral membrane proteins that have reported roles in endoplasmic reticulum (ER) quality control, ER export of secretory cargo, and programmed cell death. In this study we investigated the yeast homologs of BAP29 and BAP31, known as Yet1p and Yet3p, to gain insight on cellular function. We found that Yet1p forms a complex with Yet3p (Yet complex) and that complex assembly was important for subunit stability and proper ER localization. The Yet complex was not efficiently packaged into ER-derived COPII vesicles and therefore does not appear to act as an ER export receptor. Instead, a fraction of the Yet complex was detected in association with the ER translocation apparatus (Sec complex). Specific mutations in the Sec complex or Yet complex influenced these interactions. Moreover, associations between the Yet complex and Sec complex were increased by ER stress and diminished when protein translocation substrates were depleted. Surprisingly, yet1Delta and yet3Delta mutant strains displayed inositol starvation-related growth defects. In accord with the biochemical data, these growth defects were exacerbated by a combination of certain mutations in the Sec complex with yet1Delta or yet3Delta mutations. We propose a model for the Yet-Sec complex interaction that places Yet1p and Yet3p at the translocation pore to manage biogenesis of specific transmembrane secretory proteins.
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Affiliation(s)
- Joshua D Wilson
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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84
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Brodsky JL. The use of in vitro assays to measure endoplasmic reticulum-associated degradation. Methods Enzymol 2010; 470:661-79. [PMID: 20946830 DOI: 10.1016/s0076-6879(10)70027-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
Approximately one-third of all newly translated polypeptides interact with the endoplasmic reticulum (ER), an event that is essential to target these nascent proteins to distinct compartments within the cell or to the extracellular milieu. Thus, the ER houses molecular chaperones that augment the folding of this diverse group of macromolecules. The ER also houses the enzymes that catalyze a multitude of posttranslational modifications. If, however, proteins misfold or are improperly modified in the ER they are proteolyzed via a process known as ER-associated degradation (ERAD). During ERAD, substrates are selected by molecular chaperones and chaperone-like proteins. They are then delivered to the cytoplasmic proteasome and hydrolyzed. In most cases, delivery and proteasome-targeting require the covalent attachment of ubiquitin. The discovery and underlying mechanisms of the ERAD pathway have been aided by the development of in vitro assays that employ components derived from the yeast, Saccharomyces cerevisiae. These assays recapitulate the selection of ERAD substrates, the "retrotranslocation" of selected polypeptides from the ER into the cytoplasm, and the proteasome-mediated degradation of the substrate. The ubiquitination of integral membrane ERAD substrates has also been reconstituted.
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Affiliation(s)
- Jeffrey L Brodsky
- Department of Biological Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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85
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Wang S, Ng DTW. Evasion of endoplasmic reticulum surveillance makes Wsc1p an obligate substrate of Golgi quality control. Mol Biol Cell 2010; 21:1153-65. [PMID: 20130083 PMCID: PMC2847520 DOI: 10.1091/mbc.e09-10-0910] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
In the endoplasmic reticulum (ER), most newly synthesized proteins are retained by quality control mechanisms until folded. Misfolded molecules are sorted to ER-associated degradation (ERAD) pathways for disposal. Reports of mutant proteins degraded in the vacuole/lysosome suggested an independent Golgi-based mechanism also at work. Although little is understood of the post-ER pathway, the growing number of variants using it suggests a major role in quality control. Why seemingly redundant mechanisms in sequential compartments are needed is unclear. To understand their physiological relationship, the identification of endogenous pathway-specific substrates is a prerequisite. With ERAD substrates already well characterized, the discovery of Wsc1p as an obligate substrate of Golgi quality control enabled detailed cross-pathway analyses for the first time. By analyzing a panel of engineered substrates, the data show that the surveillance mode is determined by each polypeptide's intrinsic design. Although most secretory pathway proteins can display ERAD determinants when misfolded, the lack thereof shields Wsc1p from inspection by ER surveillance. Additionally, a powerful ER export signal mediates transport whether the luminal domain is folded or not. By evading ERAD through these passive and active mechanisms, Wsc1p is fully dependent on the post-ER system for its quality control.
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Affiliation(s)
- Songyu Wang
- Department of Biological Sciences, National University of Singapore, Singapore
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86
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GPI glycan remodeling by PGAP5 regulates transport of GPI-anchored proteins from the ER to the Golgi. Cell 2009; 139:352-65. [PMID: 19837036 DOI: 10.1016/j.cell.2009.08.040] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 06/29/2009] [Accepted: 08/12/2009] [Indexed: 01/12/2023]
Abstract
Many eukaryotic proteins are attached to the cell surface via glycosylphosphatidylinositol (GPI) anchors. How GPI-anchored proteins (GPI-APs) are trafficked from the endoplasmic reticulum (ER) to the cell surface is poorly understood, but the GPI moiety has been postulated to function as a signal for sorting and transport. Here, we established mutant cells that were selectively defective in transport of GPI-APs from the ER to the Golgi. We identified a responsible gene, designated PGAP5 (post-GPI-attachment to proteins 5). PGAP5 belongs to a dimetal-containing phosphoesterase family and catalyzed the remodeling of the glycan moiety on GPI-APs. PGAP5 catalytic activity is a prerequisite for the efficient exit of GPI-APs from the ER. Our data demonstrate that GPI glycan acts as an ER-exit signal and suggest that glycan remodeling mediated by PGAP5 regulates GPI-AP transport in the early secretory pathway.
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87
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Budnik A, Stephens DJ. ER exit sites--localization and control of COPII vesicle formation. FEBS Lett 2009; 583:3796-803. [PMID: 19850039 DOI: 10.1016/j.febslet.2009.10.038] [Citation(s) in RCA: 127] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2009] [Revised: 10/13/2009] [Accepted: 10/15/2009] [Indexed: 11/15/2022]
Abstract
The first membrane trafficking step in the biosynthetic secretory pathway, the export of proteins and lipids from the endoplasmic reticulum (ER), is mediated by COPII-coated vesicles. In mammalian cells, COPII vesicle budding occurs at specialized sites on the ER, the so-called transitional ER (tER). Here, we discuss aspects of the formation and maintenance of these sites, the mechanisms by which cargo becomes segregated within them, and the propagation of ER exit sites (ERES) during cell division. All of these features are inherently linked to the formation, maintenance and function of the Golgi apparatus underlining the importance of ERES to Golgi function and more widely in terms of intracellular organization and cellular function.
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Affiliation(s)
- Annika Budnik
- Cell Biology Laboratories, Department of Biochemistry, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, United Kingdom
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88
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Townley AK, Stephens DJ. Vesicle coating and uncoating: controlling the formation of large COPII-coated carriers. F1000 BIOLOGY REPORTS 2009; 1:65. [PMID: 20401317 PMCID: PMC2854804 DOI: 10.3410/b1-65] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The basic mechanisms underlying the formation of coated vesicles are now defined in considerable detail. This article highlights recent developments in our understanding of the problem of exporting large macromolecular cargo such as procollagen from the endoplasmic reticulum and discusses the implications that this has for cell and tissue organisation and human disease.
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Affiliation(s)
- Anna K Townley
- Cell Biology Laboratories, Department of Biochemistry, University of Bristol, School of Medical Sciences, University Walk, Bristol BS8 1TD, UK
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89
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On vesicle formation and tethering in the ER–Golgi shuttle. Curr Opin Cell Biol 2009; 21:531-6. [DOI: 10.1016/j.ceb.2009.03.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2009] [Revised: 03/24/2009] [Accepted: 03/24/2009] [Indexed: 01/13/2023]
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90
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Bue CA, Barlowe C. Molecular dissection of Erv26p identifies separable cargo binding and coat protein sorting activities. J Biol Chem 2009; 284:24049-60. [PMID: 19574229 DOI: 10.1074/jbc.m109.022590] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Efficient export of secretory alkaline phosphatase (ALP) from the endoplasmic reticulum depends on the conserved transmembrane sorting adaptor Erv26p/Svp26p. In the present study we investigated the mechanism by which Erv26p couples pro-ALP to the coat protein complex II (COPII) export machinery. Site-specific mutations were introduced into Erv26p, and mutant proteins were assessed in cell-free assays that monitor interactions with pro-ALP cargo and packaging into COPII vesicles. Mutations in the second and third loop domains of Erv26p inhibited interaction with pro-ALP, whereas mutations in the C-terminal tail sequence influenced incorporation into COPII vesicles and subcellular distribution. Interestingly mutations in the second loop domain also influenced Erv26p homodimer associations. Finally we demonstrated that Ktr3p, a cis-Golgi-localized mannosyltransferase, also relies on Erv26p for efficient COPII-dependent export from the endoplasmic reticulum. These findings demonstrate that Erv26p acts as a protein sorting adaptor for a variety of Type II transmembrane cargo proteins and requires domain-specific interactions with both cargo and coat subunits to promote efficient secretory protein transport.
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Affiliation(s)
- Catherine A Bue
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
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91
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TANGO1 facilitates cargo loading at endoplasmic reticulum exit sites. Cell 2009; 136:891-902. [PMID: 19269366 DOI: 10.1016/j.cell.2008.12.025] [Citation(s) in RCA: 266] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Revised: 10/08/2008] [Accepted: 12/12/2008] [Indexed: 01/09/2023]
Abstract
A genome-wide screen revealed previously unidentified components required for transport and Golgi organization (TANGO). We now provide evidence that one of these proteins, TANGO1, is an integral membrane protein localized to endoplasmic reticulum (ER) exit sites, with a luminal SH3 domain and a cytoplasmic proline-rich domain (PRD). Knockdown of TANGO1 inhibits export of bulky collagen VII from the ER. The SH3 domain of TANGO1 binds to collagen VII; the PRD binds to the COPII coat subunits, Sec23/24. In this scenario, PRD binding to Sec23/24 subunits could stall COPII carrier biogenesis to permit the luminal domain of TANGO1 to guide SH3-bound cargo into a growing carrier. All cells except those of hematopoietic origin express TANGO1. We propose that TANGO1 exports other cargoes in cells that do not secrete collagen VII. However, TANGO1 does not enter the budding carrier, which represents a unique mechanism to load cargo into COPII carriers.
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92
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The presence of an ER exit signal determines the protein sorting upon ER exit in yeast. Biochem J 2008; 414:237-45. [DOI: 10.1042/bj20080715] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
In yeast, there are at least two vesicle populations upon ER (endoplasmic reticulum) exit, one containing Gap1p (general aminoacid permease) and a glycosylated α-factor, gpαF (glycosylated proα-factor), and the other containing GPI (glycosylphosphatidylinositol)-anchored proteins, Gas1p (glycophospholipid-anchored surface protein) and Yps1p. We attempted to identify sorting determinants for this protein sorting event in the ER. We found that mutant Gas1 proteins that lack a GPI anchor and/or S/T region (serine- and threonine-rich region), two common characteristic features conserved among yeast GPI-anchored proteins, were still sorted away from Gap1p-containing vesicles. Furthermore, a mutant glycosylated α-factor, gpαGPI, which contains both the GPI anchor and S/T region from Gas1p, still entered Gap1p-containing vesicles, demonstrating that these conserved characteristics do not prevent proteins from entering Gap1p-containing vesicles. gpαF showed severely reduced budding efficiency in the absence of its ER exit receptor Erv29p, and this residual budding product no longer entered Gap1p-containing vesicles. These results suggest that the interaction of gpαF with Erv29p is essential for sorting into Gap1p-containing vesicles. We compared the detergent solubility of Gas1p and the gpαGPI in the ER with that in ER-derived vesicles. Both GPI-anchored proteins similarly partitioned into the DRM (detergent-resistant membrane) in the ER. Based on the fact that they entered different ER-derived vesicles, we conclude that DRM partitioning of GPI-anchored proteins is not the dominant determinant of protein sorting upon ER exit. Interestingly, upon incorporation into the ER-derived vesicles, gpαGPI was no longer detergent-insoluble, in contrast with the persistent detergent insolubility of Gas1p in the ER-derived vesicles. We present different explanations for the different behaviours of GPI-anchored proteins in distinct ER-derived vesicle populations.
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93
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Abstract
α-synuclein gene mutations are major underlying genetic defects known in familial juvenile onset Parkinson’s disease (PD), and α-synuclein is a major constituent of Lewy Bodies, the pathological hallmark of PD. The normal cellular function of α-synuclein has been elusive, and its exact etiological mechanism in causing dopaminergic neuronal death in PD is also not clearly understood. Very recent reports now indicate that mutant or simply over-expressed α-synuclein could cause damage by interfering with particular steps of neuronal membrane traffic. α-synuclein selectively blocks endoplamic reticulum-to-Golgi transport, thus causing ER stress. A screen in a yeast revealed that α-synuclein toxicity could be suppressed by over-expression of the small GTPase Ypt1/Rab1, and that over-expression of the latter rescues neuron loss in invertebrate and mammalian models of α-synuclein-induced neurodegeneration. α-synuclein may also serve a chaperone function for the proper folding of synaptic SNAREs that are important for neurotransmitter release. We discuss these recent results and the emerging pathophysiological interaction of α-synuclein with components of neuronal membrane traffic.
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94
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Hwang SO, Boswell SA, Seo JS, Lee SW. Novel oxidative stress-responsive gene ERS25 functions as a regulator of the heat-shock and cell death response. J Biol Chem 2008; 283:13063-9. [PMID: 18326488 DOI: 10.1074/jbc.m709656200] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Members of the yeast p24 family, including Emp24p and Erv25p, exist as heteromeric complexes that have been proposed to cycle between the endoplasmic reticulum (ER) and Golgi compartments. The specific functions and sites of action of p24 proteins are still unknown. Here we identified a human homolog of the yeast p24 family of proteins, named ERS25 (endoplasmic reticulum stress-response protein 25), and investigated its role in stress response. ERS25 is predicted to have an ER localization signal peptide, a GOLD (Golgi dynamics) domain, which is found in several eukaryotic Golgi and lipid-trafficking proteins, a coiled-coil region, and a transmembrane domain. We demonstrate that ERS25 is localized to the ER and is induced by ER-specific stress, heat shock, and oxidative stress. The selective induction of ERS25 by brefeldin A, but not tunicamycin, implicates the involvement of ERS25 in protein trafficking between the ER and the Golgi. Small interfering RNA-mediated inhibition of ERS25 results in a significant decrease in apoptosis as well as a reduction of reactive oxygen species induced by oxidative stress. Moreover, ERS25 depletion results in a significant increase in the levels of the ER chaperone HSP70 in response to heat-shock stress through increased levels of HSF-1. We also found that inhibition of ERS25 induction in response to heat shock enhanced the binding of HSP70 to Apaf-1, which is likely to interfere in stress-mediated apoptosis. Together, the data presented here demonstrate that ERS25 may play a critical role in regulation of heat-shock response and apoptosis.
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Affiliation(s)
- Sun Ok Hwang
- Cutaneous Biology Research Center, Massachusetts General Hospital, Charlestown, Massachusetts 02129, USA
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95
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Liu Y, Chang A. Heat shock response relieves ER stress. EMBO J 2008; 27:1049-59. [PMID: 18323774 DOI: 10.1038/emboj.2008.42] [Citation(s) in RCA: 129] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 02/15/2008] [Indexed: 11/09/2022] Open
Abstract
Accumulation of misfolded protein in the endoplasmic reticulum (ER) causes stress. The unfolded protein response (UPR), a transcriptional induction pathway, is activated to relieve ER stress. Although UPR is not essential for viability, UPR-deficient cells are more sensitive to ER stress; ire1Delta cells cannot grow when challenged with tunicamycin or by overexpression of misfolded CPY(*). In these cells, multiple functions are defective, including translocation, ER-associated degradation (ERAD), and ER-to-Golgi transport. We tested whether heat shock response (HSR) can relieve ER stress. Using a constitutively active Hsf1 transcription factor to induce HSR without temperature shift, we find that HSR rescues growth of stressed ire1Delta cells, and partially relieves defects in translocation and ERAD. Cargo-specific effects of constitutively active Hsf1 on ER-to-Golgi transport are correlated with enhanced protein levels of the respective cargo receptors. In vivo, HSR is activated by ER stress, albeit to a lower level than that caused by heat. Genomic analysis of HSR targets reveals that >25% have function in common with UPR targets. We propose that HSR can relieve stress in UPR-deficient cells by affecting multiple ER activities.
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Affiliation(s)
- Yu Liu
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48104, USA
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96
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Mitrovic S, Ben-Tekaya H, Koegler E, Gruenberg J, Hauri HP. The cargo receptors Surf4, endoplasmic reticulum-Golgi intermediate compartment (ERGIC)-53, and p25 are required to maintain the architecture of ERGIC and Golgi. Mol Biol Cell 2008; 19:1976-90. [PMID: 18287528 DOI: 10.1091/mbc.e07-10-0989] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Rapidly cycling proteins of the early secretory pathway can operate as cargo receptors. Known cargo receptors are abundant proteins, but it remains mysterious why their inactivation leads to rather limited secretion phenotypes. Studies of Surf4, the human orthologue of the yeast cargo receptor Erv29p, now reveal a novel function of cargo receptors. Surf4 was found to interact with endoplasmic reticulum-Golgi intermediate compartment (ERGIC)-53 and p24 proteins. Silencing Surf4 together with ERGIC-53 or silencing the p24 family member p25 induced an identical phenotype characterized by a reduced number of ERGIC clusters and fragmentation of the Golgi apparatus without effect on anterograde transport. Live imaging showed decreased stability of ERGIC clusters after knockdown of p25. Silencing of Surf4/ERGIC-53 or p25 resulted in partial redistribution of coat protein (COP) I but not Golgi matrix proteins to the cytosol and partial resistance of the cis-Golgi to brefeldin A. These findings imply that cargo receptors are essential for maintaining the architecture of ERGIC and Golgi by controlling COP I recruitment.
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97
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Nyfeler B, Reiterer V, Wendeler MW, Stefan E, Zhang B, Michnick SW, Hauri HP. Identification of ERGIC-53 as an intracellular transport receptor of alpha1-antitrypsin. ACTA ACUST UNITED AC 2008; 180:705-12. [PMID: 18283111 PMCID: PMC2265576 DOI: 10.1083/jcb.200709100] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Secretory proteins are exported from the endoplasmic reticulum (ER) by bulk flow and/or receptor-mediated transport. Our understanding of this process is limited because of the low number of identified transport receptors and cognate cargo proteins. In mammalian cells, the lectin ER Golgi intermediate compartment 53-kD protein (ERGIC-53) represents the best characterized cargo receptor. It assists ER export of a subset of glycoproteins including coagulation factors V and VIII and cathepsin C and Z. Here, we report a novel screening strategy to identify protein interactions in the lumen of the secretory pathway using a yellow fluorescent protein-based protein fragment complementation assay. By screening a human liver complementary DNA library, we identify alpha1-antitrypsin (alpha1-AT) as previously unrecognized cargo of ERGIC-53 and show that cargo capture is carbohydrate- and conformation-dependent. ERGIC-53 knockdown and knockout cells display a specific secretion defect of alpha1-AT that is corrected by reintroducing ERGIC-53. The results reveal ERGIC-53 to be an intracellular transport receptor of alpha1-AT and provide direct evidence for active receptor-mediated ER export of a soluble secretory protein in higher eukaryotes.
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Affiliation(s)
- Beat Nyfeler
- Biozentrum, University of Basel, CH-4056 Basel, Switzerland
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98
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Foley DA, Sharpe HJ, Otte S. Membrane topology of the endoplasmic reticulum to Golgi transport factor Erv29p. Mol Membr Biol 2007; 24:259-68. [PMID: 17520482 DOI: 10.1080/09687860601178518] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Secretory proteins are transported from the endoplasmic reticulum to the Golgi apparatus via COPII-coated intermediates. Yeast Erv29p is a transmembrane protein cycling between these compartments. It is conserved across species, with one ortholog found in each genome studied, including the surf-4 protein in mammals. Yeast Erv29p acts as a receptor, loading a specific subset of soluble cargo, including glycosylated alpha factor pheromone precursor and carboxypeptidase Y, into vesicles. As the eukaryotic secretory pathway is highly conserved, mammalian surf-4 may perform a similar role in the transport of unknown substrates. Here we report the membrane topology of yeast Erv29p, which we solved by minimally invasive cysteine accessibility scanning using thiol-specific biotinylation and fluorescent labeling methods. Erv29p contains four transmembrane domains with both termini exposed to the cytosol. Two luminal loops may contain a recognition site for hydrophobic export signals on soluble cargo.
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Affiliation(s)
- Deirdre A Foley
- Department of Biochemistry and Molecular Genetics, University of Illinois at Chicago, Illinois, USA
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99
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Baines AC, Zhang B. Receptor-mediated protein transport in the early secretory pathway. Trends Biochem Sci 2007; 32:381-8. [PMID: 17618120 DOI: 10.1016/j.tibs.2007.06.006] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2007] [Revised: 05/31/2007] [Accepted: 06/22/2007] [Indexed: 11/25/2022]
Abstract
Many secretory proteins are thought to rely upon transmembrane cargo receptors for efficient endoplasmic reticulum (ER)-to-Golgi transport. These receptors recognize specific cargo-encoded sorting signals. Only a few such cargo receptors have been characterized in detail, most of them in yeast. The only well-defined cargo receptor from mammalian cells, the LMAN1-MCFD2 complex, is required for the efficient secretion of coagulation factors V and VIII. Studies of this complex, coupled with recent advances in elucidating the basic machinery that mediates ER-to-Golgi transport, have provided a more-detailed picture of the mechanisms underlying receptor-mediated transport in the early secretory pathway. In addition to yeast studies, insights have also come from investigations into several inherited disorders that have recently been attributed to defects in the secretory pathway.
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Affiliation(s)
- Andrea C Baines
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109-2216, USA
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100
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Nonaka M, Ma BY, Ohtani M, Yamamoto A, Murata M, Totani K, Ito Y, Miwa K, Nogami W, Kawasaki N, Kawasaki T. Subcellular localization and physiological significance of intracellular mannan-binding protein. J Biol Chem 2007; 282:17908-20. [PMID: 17442667 DOI: 10.1074/jbc.m700992200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mannan-binding protein (MBP) is a C-type mammalian lectin specific for mannose and N-acetylglucosamine. MBP is mainly synthesized in the liver and occurs naturally in two forms, serum MBP (S-MBP) and intracellular MBP (I-MBP). S-MBP activates complement in association with MBP-associated serine proteases via the lectin pathway. Despite our previous study (Mori, K., Kawasaki, T., and Yamashina, I. (1984) Arch. Biochem. Biophys. 232, 223-233), the subcellular localization of I-MBP and its functional implication have not been clarified yet. Here, as an extension of our previous studies, we have demonstrated that the expression of human MBP cDNA reproduces native MBP differentiation of S-MBP and I-MBP in human hepatoma cells. I-MBP shows distinct accumulation in cytoplasmic granules, and is predominantly localized in the endoplasmic reticulum (ER) and involved in COPII vesicle-mediated ER-to-Golgi transport. However, the subcellular localization of either a mutant (C236S/C244S) I-MBP, which lacks carbohydrate-binding activity, or the wild-type I-MBP in tunicamycin-treated cells shows an equally diffuse cytoplasmic distribution, suggesting that the unique accumulation of I-MBP in the ER and COPII vesicles is mediated by an N-glycan-lectin interaction. Furthermore, the binding of I-MBP with glycoprotein intermediates occurs in the ER, which is carbohydrate- and pH-dependent, and is affected by glucose-trimmed high-mannose-type oligosaccharides. These results strongly indicate that I-MBP may function as a cargo transport lectin facilitating ER-to-Golgi traffic in glycoprotein quality control.
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Affiliation(s)
- Motohiro Nonaka
- Research Center for Glycobiotechnology, Ritsumeikan University, Shiga 525-8577, Japan
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