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Martinić Cezar T, Lozančić M, Novačić A, Matičević A, Matijević D, Vallée B, Mrša V, Teparić R, Žunar B. Streamlining N-terminally anchored yeast surface display via structural insights into S. cerevisiae Pir proteins. Microb Cell Fact 2023; 22:174. [PMID: 37679759 PMCID: PMC10483737 DOI: 10.1186/s12934-023-02183-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2023] [Accepted: 08/18/2023] [Indexed: 09/09/2023] Open
Abstract
Surface display co-opts yeast's innate ability to embellish its cell wall with mannoproteins, thus converting the yeast's outer surface into a growing and self-sustaining catalyst. However, the efficient toolbox for converting the enzyme of interest into its surface-displayed isoform is currently lacking, especially if the isoform needs to be anchored to the cell wall near the isoform's N-terminus, e.g., through a short GPI-independent protein anchor. Aiming to advance such N-terminally anchored surface display, we employed in silico and machine-learning strategies to study the 3D structure, function, genomic organisation, and evolution of the Pir protein family, whose members evolved to covalently attach themselves near their N-terminus to the β-1,3-glucan of the cell wall. Through the newly-gained insights, we rationally engineered 14 S. cerevisiae Hsp150 (Pir2)-based fusion proteins. We quantified their performance, uncovering guidelines for efficient yeast surface display while developing a construct that promoted a 2.5-fold more efficient display of a reporter protein than the full-length Hsp150. Moreover, we developed a Pir-tag, i.e., a peptide spanning only 4.5 kDa but promoting as efficient surface display of a reporter protein as the full-length Hsp150. These constructs fortify the existing surface display toolbox, allowing for a prompt and routine refitting of intracellular proteins into their N-terminally anchored isoforms.
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Affiliation(s)
- Tea Martinić Cezar
- Laboratory for Biochemistry, Department of Chemistry and Biochemistry, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, Zagreb, 10000, Croatia
| | - Mateja Lozančić
- Laboratory for Biochemistry, Department of Chemistry and Biochemistry, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, Zagreb, 10000, Croatia
| | - Ana Novačić
- Laboratory for Biochemistry, Department of Chemistry and Biochemistry, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, Zagreb, 10000, Croatia
| | - Ana Matičević
- Laboratory for Biochemistry, Department of Chemistry and Biochemistry, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, Zagreb, 10000, Croatia
| | - Dominik Matijević
- Laboratory for Biochemistry, Department of Chemistry and Biochemistry, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, Zagreb, 10000, Croatia
| | - Béatrice Vallée
- Centre de Biophysique Moléculaire (CBM), CNRS, University of Orléans and INSERM, Orléans Cedex 2, UPR, 4301, 45071, France
| | - Vladimir Mrša
- Laboratory for Biochemistry, Department of Chemistry and Biochemistry, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, Zagreb, 10000, Croatia
| | - Renata Teparić
- Laboratory for Biochemistry, Department of Chemistry and Biochemistry, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, Zagreb, 10000, Croatia
| | - Bojan Žunar
- Laboratory for Biochemistry, Department of Chemistry and Biochemistry, Faculty of Food Technology and Biotechnology, University of Zagreb, Pierottijeva 6, Zagreb, 10000, Croatia.
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Mironov AA. ER-Golgi transport could occur in the absence of COPII vesicles. Nat Rev Mol Cell Biol 2014; 15:1. [PMID: 24496389 DOI: 10.1038/nrm3588-c1] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Yorimitsu T, Sato K, Takeuchi M. Molecular mechanisms of Sar/Arf GTPases in vesicular trafficking in yeast and plants. FRONTIERS IN PLANT SCIENCE 2014; 5:411. [PMID: 25191334 PMCID: PMC4140167 DOI: 10.3389/fpls.2014.00411] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/27/2014] [Accepted: 08/03/2014] [Indexed: 05/21/2023]
Abstract
Small GTPase proteins play essential roles in the regulation of vesicular trafficking systems in eukaryotic cells. Two types of small GTPases, secretion-associated Ras-related protein (Sar) and ADP-ribosylation factor (Arf), act in the biogenesis of transport vesicles. Sar/Arf GTPases function as molecular switches by cycling between active, GTP-bound and inactive, GDP-bound forms, catalyzed by guanine nucleotide exchange factors and GTPase-activating proteins, respectively. Activated Sar/Arf GTPases undergo a conformational change, exposing the N-terminal amphipathic α-helix for insertion into membranes. The process triggers the recruitment and assembly of coat proteins to the membranes, followed by coated vesicle formation and scission. In higher plants, Sar/Arf GTPases also play pivotal roles in maintaining the dynamic identity of organelles in the secretory pathway. Sar1 protein strictly controls anterograde transport from the endoplasmic reticulum (ER) through the recruitment of plant COPII coat components onto membranes. COPII vesicle transport is responsible for the organization of highly conserved polygonal ER networks. In contrast, Arf proteins contribute to the regulation of multiple trafficking routes, including transport through the Golgi complex and endocytic transport. These transport systems have diversified in the plant kingdom independently and exhibit several plant-specific features with respect to Golgi organization, endocytic cycling, cell polarity and cytokinesis. The functional diversification of vesicular trafficking systems ensures the multicellular development of higher plants. This review focuses on the current knowledge of Sar/Arf GTPases, highlighting the molecular details of GTPase regulation in vesicle formation in yeast and advances in knowledge of the characteristics of vesicle trafficking in plants.
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Affiliation(s)
- Tomohiro Yorimitsu
- Department of Life Sciences, Graduate School of Arts and Sciences, University of TokyoTokyo, Japan
| | - Ken Sato
- Department of Life Sciences, Graduate School of Arts and Sciences, University of TokyoTokyo, Japan
| | - Masaki Takeuchi
- Department of Chemistry, Graduate School of Science, University of TokyoTokyo, Japan
- *Correspondence: Masaki Takeuchi, Department of Chemistry, Graduate School of Science, University of Tokyo, Tokyo 113-0033, Japan e-mail:
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Drakakaki G, Dandekar A. Protein secretion: how many secretory routes does a plant cell have? PLANT SCIENCE : AN INTERNATIONAL JOURNAL OF EXPERIMENTAL PLANT BIOLOGY 2013; 203-204:74-8. [PMID: 23415330 DOI: 10.1016/j.plantsci.2012.12.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 12/18/2012] [Accepted: 12/26/2012] [Indexed: 05/19/2023]
Abstract
Conventional protein secretion is mediated by the endomembrane system. Secreted proteins are inserted into the endomembrane system through a N-terminal signal peptide and follow the endoplasmic reticulum to the Golgi trafficking pathway en route to the plasma membrane or the extracellular apoplastic space. In mammalian and yeast cells, unconventional secretion has been identified and relatively well studied. Also in plants, evidence of unconventional secretion mechanisms is accumulating. The ever-increasing number of leaderless proteins identified in proteomic studies indicates the importance of unconventional protein secretion in plants. Novel approaches, such as chemical genomics and vesicle proteomics might be able to provide new insights into unconventional protein secretion in plants.
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Affiliation(s)
- Georgia Drakakaki
- Department of Plant Sciences, University of California, Davis 95616, USA
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Prydz K, Tveit H, Vedeler A, Saraste J. Arrivals and departures at the plasma membrane: direct and indirect transport routes. Cell Tissue Res 2012; 352:5-20. [DOI: 10.1007/s00441-012-1409-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2011] [Accepted: 03/14/2012] [Indexed: 12/21/2022]
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Vesicle-mediated ER export of proteins and lipids. Biochim Biophys Acta Mol Cell Biol Lipids 2012; 1821:1040-9. [PMID: 22265716 DOI: 10.1016/j.bbalip.2012.01.005] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Revised: 12/30/2011] [Accepted: 01/04/2012] [Indexed: 11/21/2022]
Abstract
In eukaryotic cells, the endoplasmic reticulum (ER) is a major site of synthesis of both lipids and proteins, many of which must be transported to other organelles. The COPII coat-comprising Sar1, Sec23/24, Sec13/31-generates transport vesicles that mediate the bulk of protein/lipid export from the ER. The coat exhibits remarkable flexibility in its ability to specifically select and accommodate a large number of cargoes with diverse properties. In this review, we discuss the fundamentals of COPII vesicle production and describe recent advances that further our understanding of just how flexible COPII cargo recruitment and vesicle formation may be. Large or bulky cargo molecules (e.g. collagen rods and lipoprotein particles) exceed the canonical size for COPII vesicles and seem to rely on the additional action of recently identified accessory molecules. Although the bulk of the research has focused on the fate of protein cargo, the mechanisms and regulation of lipid transport are equally critical to cellular survival. From their site of synthesis in the ER, phospholipids, sphingolipids and sterols exit the ER, either accompanying cargo in vesicles or directly across the cytoplasm shielded by lipid-transfer proteins. Finally, we highlight the current challenges to the field in addressing the physiological regulation of COPII vesicle production and the molecular details of how diverse cargoes, both proteins and lipids, are accommodated. This article is part of a Special Issue entitled Lipids and Vesicular Transport.
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Grieve AG, Rabouille C. Golgi bypass: skirting around the heart of classical secretion. Cold Spring Harb Perspect Biol 2011; 3:cshperspect.a005298. [PMID: 21441587 DOI: 10.1101/cshperspect.a005298] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Classical secretion consists of the delivery of transmembrane and soluble proteins to the plasma membrane and the extracellular medium, respectively, and is mediated by the organelles of the secretory pathway, the Endoplasmic Reticulum (ER), the ER exit sites, and the Golgi, as described by the Nobel Prize winner George Palade (Palade 1975). At the center of this transport route, the Golgi stack has a major role in modifying, processing, sorting, and dispatching newly synthesized proteins to their final destinations. More recently, however, it has become clear that an increasing number of transmembrane proteins reach the plasma membrane unconventionally, either by exiting the ER in non-COPII vesicles or by bypassing the Golgi. Here, we discuss the evidence for Golgi bypass and the possible physiological benefits of it. Intriguingly, at least during Drosophila development, Golgi bypass seems to be mediated by a Golgi protein, dGRASP, which is found ectopically localized to the plasma membrane.
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Affiliation(s)
- Adam G Grieve
- Cell Microscopy Centre, Department of Cell Biology, University Medical Center Utrecht, The Netherlands
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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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9
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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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Greco TM, Seeholzer SH, Mak A, Spruce L, Ischiropoulos H. Quantitative mass spectrometry-based proteomics reveals the dynamic range of primary mouse astrocyte protein secretion. J Proteome Res 2010; 9:2764-74. [PMID: 20329800 PMCID: PMC2866110 DOI: 10.1021/pr100134n] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Growing appreciation for astrocytes as active participants in nervous system development, neurovascular metabolic coupling, and neurological disease progression has stimulated recent investigation into specific astrocyte-secreted proteins that may mediate these functions. The current work utilized SILAC-generated isotope reference proteomes to quantify relative protein abundances between the astrocyte proteome and secretome. Multidimensional GeLC-MS/MS analysis of astrocyte conditioned media and cell lysates resulted in the relative quantification of 516 proteins, 92 of which were greater than 1.5-fold enriched in astrocyte-conditioned media (ACM). Eighty of the ACM-enriched proteins had N-terminal signal peptides, comprising well-known classically secreted proteins, such as apolipoprotein E and SPARC, and several cathepsins that localize to endosomal/lysosomal compartments. The remaining twelve ACM-enriched proteins, such as vimentin, ferritins, and histones, lacked N-terminal signal peptides. Also, 47 proteins contained predicted N-terminal signal peptides but were not enriched in ACM (<1.5-fold), 25 of which were localized to ER, Golgi, or mitochondria membrane-bound compartments. Overall, by combining quantitative proteomics with subcellular localization prediction, an informative description of protein distribution can be obtained, providing insights into protein secretion.
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Affiliation(s)
- Todd M. Greco
- Department of Pediatrics, The Children’s Hospital of Philadelphia Research Institute and The University of Pennsylvania Philadelphia, PA, 19104, USA
| | - Steven H. Seeholzer
- Department of Pediatrics, The Children’s Hospital of Philadelphia Research Institute and The University of Pennsylvania Philadelphia, PA, 19104, USA
| | - Adrian Mak
- Department of Pediatrics, The Children’s Hospital of Philadelphia Research Institute and The University of Pennsylvania Philadelphia, PA, 19104, USA
| | - Lynn Spruce
- Department of Pediatrics, The Children’s Hospital of Philadelphia Research Institute and The University of Pennsylvania Philadelphia, PA, 19104, USA
| | - Harry Ischiropoulos
- Department of Pediatrics, The Children’s Hospital of Philadelphia Research Institute and The University of Pennsylvania Philadelphia, PA, 19104, USA
- Department of Pharmacology, The Children’s Hospital of Philadelphia Research Institute and The University of Pennsylvania Philadelphia, PA, 19104, USA
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11
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Siddiqi S, Saleem U, Abumrad NA, Davidson NO, Storch J, Siddiqi SA, Mansbach CM. A novel multiprotein complex is required to generate the prechylomicron transport vesicle from intestinal ER. J Lipid Res 2010; 51:1918-28. [PMID: 20237389 DOI: 10.1194/jlr.m005611] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Dietary lipid absorption is dependent on chylomicron production whose rate-limiting step across the intestinal absorptive cell is the exit of chylomicrons from the endoplasmic reticulum (ER) in its ER-to-Golgi transport vesicle, the prechylomicron transport vesicle (PCTV). This study addresses the composition of the budding complex for PCTV. Immunoprecipitation (IP) studies from rat intestinal ER solubilized in Triton X-100 suggested that vesicle-associated membrane protein 7 (VAMP7), apolipoprotein B48 (apoB48), liver fatty acid-binding protein (L-FABP), CD36, and the COPII proteins were associated on incubation of the ER with cytosol and ATP. This association was confirmed by chromatography of the solubilized ER over Sephacryl S400-HR in which these constituents cochromatographed with an apparent kDa of 630. No multiprotein complex was detected when the ER was chromatographed in the absence of PCTV budding activity (resting ER or PKCzeta depletion of ER and cytosol). Treatment of the ER with anti-apoB48 or anti-VAMP7 antibodies or using gene disrupted L-FABP or CD36 mice all significantly inhibited PCTV generation. A smaller complex (no COPII proteins) was formed when only rL-FABP was used to bud PCTV. The data support the conclusion that the PCTV budding complex in intestinal ER is composed of VAMP7, apoB48, CD36, and L-FABP, plus the COPII proteins.
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Affiliation(s)
- Shahzad Siddiqi
- Division of Gastroenterology, Department of Medicine, University of Tennessee Health Science Center, Memphis, TN, USA
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12
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Nickel W, Rabouille C. Mechanisms of regulated unconventional protein secretion. Nat Rev Mol Cell Biol 2008; 10:148-55. [PMID: 19122676 DOI: 10.1038/nrm2617] [Citation(s) in RCA: 516] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Most eukaryotic proteins are secreted through the conventional endoplasmic reticulum (ER)-Golgi secretory pathway. However, cytoplasmic, nuclear and signal-peptide-containing proteins have been shown to reach the cell surface by non-conventional transport pathways. The mechanisms and molecular components of unconventional protein secretion are beginning to emerge, including a role for caspase 1 and for the peripheral Golgi protein GRASP, which could function as a plasma membrane tether for membrane compartments during specific stages of development.
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Affiliation(s)
- Walter Nickel
- Heidelberg University Biochemistry Center, Im Neuenheimer Feld 328, 69120 Heidelberg, Germany.
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Seppä L, Makarow M. Regulation and recovery of functions of Saccharomyces cerevisiae chaperone BiP/Kar2p after thermal insult. EUKARYOTIC CELL 2005; 4:2008-16. [PMID: 16339719 PMCID: PMC1317487 DOI: 10.1128/ec.4.12.2008-2016.2005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We described earlier a novel mode of regulation of Hsp104, a cytosolic chaperone directly involved in the refolding of heat-denatured proteins, and designated it delayed upregulation, or DUR. When Saccharomyces cerevisiae cells grown at the physiological temperature of 24 degrees C, preconditioned at 37 degrees C, and treated briefly at 50 degrees C were shifted back to 24 degrees C, Hsp104 expression was strongly induced after 2.5 h of recovery and returned back to normal after 5 h. Here we show that the endoplasmic reticulum (ER) chaperones BiP/Kar2p and Lhs1p and the mitochondrial chaperone Hsp78 were also upregulated at the physiological temperature during recovery from thermal insult. The heat shock element (HSE) in the KAR2 promoter was found to be sufficient to drive DUR. The unfolded protein element could also evoke DUR, albeit weakly, in the absence of a functional HSE. BiP/Kar2p functions in ER translocation and assists protein folding. Here we found that the synthesis of new BiP/Kar2p molecules was negligible for more than an hour after the shift of the cells from 50 degrees C to 24 degrees C. Concomitantly, ER translocation was blocked, suggesting that preexisting BiP/Kar2p molecules or other necessary proteins were not functioning. Translocation resumed concomitantly with enhanced synthesis of BiP/Kar2p after 3 h of recovery, after which ER exit and protein secretion also resumed. For a unicellular organism like S. cerevisiae, conformational repair of denatured proteins is the sole survival strategy. Chaperones that refold proteins in the cytosol, ER, and mitochondria of S. cerevisiae appear to be subject to DUR to ensure survival after thermal insults.
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Affiliation(s)
- Laura Seppä
- Program in Cellular Biotechnology, Institute of Biotechnology, P.O. Box 56, 00014 University of Helsinki, Finland.
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Karhinen L, Bastos RN, Jokitalo E, Makarow M. Endoplasmic reticulum exit of a secretory glycoprotein in the absence of sec24p family proteins in yeast. Traffic 2005; 6:562-74. [PMID: 15941408 DOI: 10.1111/j.1600-0854.2005.00297.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Glycoproteins exit the endoplasmic reticulum (ER) of the yeast Saccharomyces cerevisiae in coat protein complex II (COPII) coated vesicles. The coat consists of the essential proteins Sec23p, Sec24p, Sec13p, Sec31p, Sar1p and Sec16p. Sec24p and its two nonessential homologues Sfb2p and Sfb3p have been suggested to serve in cargo selection. Using temperature-sensitive sec24-1 mutants, we showed previously that a secretory glycoprotein, Hsp150, does not require functional Sec24p for ER exit. Deletion of SFB2, SFB3 or both from wild type or the deletion of SFB2 from sec24-1 cells did not affect Hsp150 transport. SFB3 deletion has been reported to be lethal in sec24-1. However, here we constructed a sec24-1 Deltasfb3 and a sec24-1 Deltasfb2 Deltasfb3 strain and show that Hsp150 was secreted slowly in both. Turning off the SEC24 gene did not inhibit Hsp150 secretion either, and the lack of SEC24 expression in a Deltasfb2 Deltasfb3 deletant still allowed some secretion. The sec24-1 Deltasfb2 Deltasfb3 mutant grew slower than sec24-1. The cells were irregularly shaped, budded from random sites and contained proliferated ER at permissive temperature. At restrictive temperature, the ER formed carmellae-like proliferations. Our data indicate that ER exit may occur in vesicles lacking a full complement of Sec23p/24p and Sec13p/31p, demonstrating diversity in the composition of the COPII coat.
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Affiliation(s)
- Leena Karhinen
- Program in Cellular Biotechnology, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.
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Jüschke C, Wächter A, Schwappach B, Seedorf M. SEC18/NSF-independent, protein-sorting pathway from the yeast cortical ER to the plasma membrane. ACTA ACUST UNITED AC 2005; 169:613-22. [PMID: 15911878 PMCID: PMC2171690 DOI: 10.1083/jcb.200503033] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Classic studies of temperature-sensitive secretory (sec) mutants have demonstrated that secreted and plasma membrane proteins follow a common SEC pathway via the endoplasmic reticulum (ER), Golgi apparatus, and secretory vesicles to the cell periphery. The yeast protein Ist2p, which is synthesized from a localized mRNA, travels from the ER to the plasma membrane via a novel route that operates independently of the formation of coat protein complex II-coated vesicles. In this study, we show that the COOH-terminal domain of Ist2p is necessary and sufficient to mediate SEC18-independent sorting when it is positioned at the COOH terminus of different integral membrane proteins and exposed to the cytoplasm. This domain functions as a dominant plasma membrane localization determinant that overrides other protein sorting signals. Based on these observations, we suggest a local synthesis of Ist2p at cortical ER sites, from where the protein is sorted by a novel mechanism to the plasma membrane.
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Affiliation(s)
- Christoph Jüschke
- Center of Molecular Biology, University of Heidelberg, D-69120 Heidelberg, Germany
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Tang BL, Wang Y, Ong YS, Hong W. COPII and exit from the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2005; 1744:293-303. [PMID: 15979503 DOI: 10.1016/j.bbamcr.2005.02.007] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/14/2004] [Revised: 02/16/2005] [Accepted: 02/23/2005] [Indexed: 01/06/2023]
Abstract
First discovered by genetic analysis of yeast secretion mutants, the evolutionarily conserved vesicular coat protein II (COPII) complex is responsible for membrane transport from the endoplasmic reticulum (ER) to the Golgi apparatus. In recent years, extensive efforts in structural, morphological, genetic and molecular analysis have greatly enhanced our understanding of the structural and molecular basis of COPII subunit assembly and selective cargo packaging during ER export. Very recent data have also indicated that a more "classical" picture of vesicle formation from ER exit sites (ERES) followed by their transport to the Golgi is far from accurate. Proteins modulating the function of COPII have also emerged in recent analysis. They either affect COPII-based cargo selection, the formation of vesicle/transport carrier, or subsequent targeting of the transport carrier. Together, elucidation of COPII-mediated ER export has painted a fascinating picture of molecular complexity for an essential process in all eukaryotic cells.
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Affiliation(s)
- Bor Luen Tang
- Department of Biochemistry, National University of Singapore, 8 Medical Drive, Singapore 117597, Singapore.
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Appenzeller-Herzog C, Nyfeler B, Burkhard P, Santamaria I, Lopez-Otin C, Hauri HP. Carbohydrate- and conformation-dependent cargo capture for ER-exit. Mol Biol Cell 2005; 16:1258-67. [PMID: 15635097 PMCID: PMC551490 DOI: 10.1091/mbc.e04-08-0708] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Some secretory proteins leave the endoplasmic reticulum (ER) by a receptor-mediated cargo capture mechanism, but the signals required for the cargo-receptor interaction are largely unknown. Here, we describe a novel targeting motif that is composed of a high-mannose type oligosaccharide intimately associated with a surface-exposed peptide beta-hairpin loop. The motif accounts for lectin ERGIC-53-assisted ER-export of the lyososomal enzyme procathepsin Z. The second oligosaccharide chain of procathepsin Z exhibits no binding activity for ERGIC-53, illustrating the selective lectin properties of ERGIC-53. Our data suggest that the conformation-based motif is only present in fully folded procathepsin Z and that its recognition by ERGIC-53 reflects a quality control mechanism that acts complementary to the primary folding machinery in the ER. A similar oligosaccharide/beta-hairpin loop structure is present in cathepsin C, another cargo of ERGIC-53, suggesting the general nature of this ER-exit signal. To our knowledge this is the first documentation of an ER-exit signal in soluble cargo in conjunction with its decoding by a transport receptor.
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