DOCSLIB.ORG

ER–Mitochondria Contact Sites Reporters: Strengths and Weaknesses of the Available Approaches

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
ER–Mitochondria Contact Sites Reporters: Strengths and Weaknesses of the Available Approaches International Journal of Molecular Sciences Review ER–Mitochondria Contact Sites Reporters: Strengths and Weaknesses of the Available Approaches Flavia Giamogante 1 , Lucia Barazzuol 1, Marisa Brini 2,* and Tito Calì 1,3,* 1 Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy; fl[email protected] (F.G.); [email protected] (L.B.) 2 Department of Biology, University of Padova, 35131 Padova, Italy 3 Padova Neuroscience Center (PNC), University of Padova, 35131 Padova, Italy * Correspondence: [email protected] (M.B.); [email protected] (T.C.) Received: 22 September 2020; Accepted: 30 October 2020; Published: 31 October 2020 Abstract: Organelle intercommunication represents a wide area of interest. Over the last few decades, increasing evidence has highlighted the importance of organelle contact sites in many biological processes including Ca2+ signaling, lipid biosynthesis, apoptosis, and autophagy but also their involvement in pathological conditions. ER–mitochondria tethering is one of the most investigated inter-organelle communications and it is differently modulated in response to several cellular conditions including, but not limited to, starvation, Endoplasmic Reticulum (ER) stress, and mitochondrial shape modifications. Despite many studies aiming to understand their functions and how they are perturbed under different conditions, approaches to assess organelle proximity are still limited. Indeed, better visualization and characterization of contact sites remain a fascinating challenge. The aim of this review is to summarize strengths and weaknesses of the available methods to detect and quantify contact sites, with a main focus on ER–mitochondria tethering. Keywords: ER–mitochondria tethering; split-GFP; SPLICS; organelle contact sites 1. Introduction In eukaryotes, organelles are delimited by a membrane that enables them to perform specific and unique tasks, whose characterization has been the goal of researchers for many decades. In the last years, however, the inter-organelle communication received momentum and represents an emerging aspect in cell biology. It is now well established that organelles are not isolated, but they are interconnected, thereby forming a communicating network [1]. Proteins identified at the interface between organelles seem to act as tethers that physically bridge two opposing membranes and join them to each other [2,3]; others have a specific role that occurs at the contact sites, such as the ability to transfer small molecules in a non-vesicular manner [4,5]. The interplay between the endoplasmic reticulum (ER) and mitochondria has been one of the first identified and, to date, still represents one of the best characterized forms. ER–mitochondria juxtaposition has been firstly observed by electron microscopy (EM) in the late 1950s in rat tissue; however, at that time, it was considered an artifact due to fixation [6]. Conversely, later approaches compatible with living cells analysis have validated their existence [7]. Now, it is well established that ER–mitochondrial tethering plays a crucial role in several cellular pathways, such as Ca2+ homeostasis [8,9], lipid transfer [10], mitochondrial dynamics [11], apoptosis, and mitophagy [12,13]. Many shreds of evidence report that its alteration is linked to the development of different disorders including diabetes [14], cancer [15], and neurodegenerative diseases (e.g., Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS) [16]). Int. J. Mol. Sci. 2020, 21, 8157; doi:10.3390/ijms21218157 www.mdpi.com/journal/ijms Int. J. Mol. Sci. 2020, 21, 8157 2 of 18 Int. J. Mol. Sci. 2020, 21, 8157 2 of 18 However, most of the research aimed at characterizing ER–mitochondria contact-site componentsHowever, and most their of thefunctions research face aimed the atcomplex characterizing issue of ER–mitochondria unequivocally identifying contact-site componentsthe contact, definingand their its functions function, face and the monitoring complex issue its changes of unequivocally upon perturbations. identifying the To contact,date, several defining methods its function, need toand be monitoring combined itsto changesextract all upon the perturbations.mentioned information To date, several since an methods optimized need approach to be combined that can to provideextract all them the mentionedat once is informationstill missing. since Indeed, an optimized the transient approach nature that and can variable provide abundance them at once of is ER– still mitochondriamissing. Indeed, interactions the transient within nature different and variable cell types abundance make the of ER–mitochondria development of interactionssuitable detecting within methodsdifferent cella big types challenge. make theDuring development the past decades, of suitable considerable detecting methods effort has a bigbeen challenge. spent to Duringameliorate the thepast available decades, methods considerable and edevelopffort has new been ones, spent leading to ameliorate to the possibility the available of further methods investigate and develop on newER– mitochondriaones, leading tocontact the possibility sites and ofprovide further more investigate informat onion. ER–mitochondria Starting from this contact point sitesof view, and the provide goal ofmore this information. review is to Starting discuss from the approaches this point of available view, the goalto investigate of this review ER–mitochondria is to discuss the contact approaches sites, takingavailable into to investigateaccount that ER–mitochondria every single method contact can sites, betaking useful into for accounta specific that range every of single information method dependingcan be useful on for the a topic specific of the range research. of information depending on the topic of the research. 2. Proteins Proteins Involved Involved in ER–Mitochondria Interplay Among the organelles interacting with the ER, ER, wh whichich include include the the Golgi Golgi apparatus, apparatus, mitochondria, mitochondria, peroxisomes, andand the the plasma plasma membrane, membrane, mitochondria mitochondria establish establish one of theone most of andthe well-characterizedmost and well- characterizedconnection [6]. connection Electron tomography [6]. Electron was tomography used to measure was used ER–mitochondria to measure ER–mitochondria proximity and itproximity revealed andthat it the revealed distance that between the distance the two between organelles the istwo approximately organelles is of approximately 10–30 nm [3,8 ].of This10–30 distance nm [3,8]. is closeThis distanceenough to is proposeclose enough that the to ERpropose and the that outer the mitochondria ER and the outer membrane mitochondria (OMM) canmembrane be tethered (OMM) together can beby proteinstethered locatedtogether on by the proteins opposing located membranes—indeed, on the opposing mitochondria-associated membranes—indeed, ERmitochondria- membranes associated(MAMs) can ER be membranes physically separated(MAMs) can from be thephysical otherly organelle separated membranes from the other [17–20 organelle]. We also membranes know that [17–20].their functional We also interplayknow that [ their21] is functional guaranteed interplay by specific, [21] is stabilized guaranteed contacts by specific, [22] that stabilized are able contacts to stay [22]tethered that toare each able other to stay even tethered when the to organelles each other are even moving when along the the organelles cytoskeleton are [23moving]. Many along proteins the cytoskeletonhave been identified [23]. Many in the proteins MAMs but,have for been many iden of them,tified thein the biological MAMs role but, is notfor yetmany fully of understood them, the biological(Figure1). role is not yet fully understood (Figure 1). Figure 1. 1. SchematicSchematic representation representation of the of thetethering tethering complexes complexes at the at endoplasmic the endoplasmic reticulum reticulum (ER)– mitochondria(ER)–mitochondria interface. interface. In yeast cells, the ER–mitochondria connection is ensured by a multiprotein complex called the ER–mitochondria encounter structure (ERMES), containing Mdm12, Mdm34, Mdm10, and Mmm1 proteins [[24].24]. This physical tethering allows efficient efficient lipid transport by soluble lipid-carrier proteins such as ceramide-transfer protein (CERT) and oxysterol-binding protein (OSBP) [[25].25]. In mammalian cells, the the ER–mitochondria ER–mitochondria interface interface is is more more complex. complex. Indeed, Indeed, a plethora a plethora of ofproteins proteins are are involved involved in maintaining and modulating this interaction. Mitofusin 2 (MFN2) is one of such players. It is a Int. J. Mol. Sci. 2020, 21, 8157 3 of 18 in maintaining and modulating this interaction. Mitofusin 2 (MFN2) is one of such players. It is a mitochondrial fusion guanosine-50-triphosphate (GTP)ases, localized at the outer membrane of mitochondria (OMM) and found in MAMs [26–29]. MFN2 plays a crucial role in mitochondrial fusion together with Optic Atrophy 1 OPA1, another mitochondrial fusion GTPase located on the inner membrane of mitochondria [30]. It has been reported that during the mitochondrial fusion process, mitochondrial MFN2 assembles homo- or heterodimer complexes with ER-residing MFN2 [28,31]. The interaction between the protein tyrosine phosphatase-interacting protein-51 (PTPIP51), located on the OMM, and an ER-resident protein, the vesicle-associated membrane protein B (VAPB),
Load more

Recommended publications
  • The Endomembrane System and Proteins
    Chapter 4 | Cell Structure 121 Endosymbiosis We have mentioned that both mitochondria and chloroplasts contain DNA and ribosomes. Have you wondered why? Strong evidence points to endosymbiosis as the explanation. Symbiosis is a relationship in which organisms from two separate species depend on each other for their survival. Endosymbiosis (endo- = “within”) is a mutually beneficial relationship in which one organism lives inside the other. Endosymbiotic relationships abound in nature. We have already mentioned that microbes that produce vitamin K live inside the human gut. This relationship is beneficial for us because we are unable to synthesize vitamin K. It is also beneficial for the microbes because they are protected from other organisms and from drying out, and they receive abundant food from the environment of the large intestine. Scientists have long noticed that bacteria, mitochondria, and chloroplasts are similar in size. We also know that bacteria have DNA and ribosomes, just like mitochondria and chloroplasts. Scientists believe that host cells and bacteria formed an endosymbiotic relationship when the host cells ingested both aerobic and autotrophic bacteria (cyanobacteria) but did not destroy them. Through many millions of years of evolution, these ingested bacteria became more specialized in their functions, with the aerobic bacteria becoming mitochondria and the autotrophic bacteria becoming chloroplasts. The Central Vacuole Previously, we mentioned vacuoles as essential components of plant cells. If you look at Figure 4.8b, you will see that plant cells each have a large central vacuole that occupies most of the cell's area. The central vacuole plays a key role in regulating the cell’s concentration of water in changing environmental conditions.
    [Show full text]
  • Cell Membrane
    John Lenyo Corrina Perez Hazel Owens Cell Membrane http://micro.magnet.fsu.edu/cells/plasmamembrane/plasmamembrane.html • Cell membranes are composed of proteins and lipids. • Since they are made up of mostly lipids, only certain substances can move through. spmbiology403.blogspot.com •Phospholipids are the most abundant type of lipid found in the membrane. Phospholipids are made up of two layers, the outer and inner layers. The inside layer is made of hydrophobic fatty acid tails, while the outer layer is made up of hydrophilic polar heads that are pointed toward the water. academic.brooklyn.cuny.edu •Membrane structure relies on the tendency of fatty acid molecules to spread on the surface of water. • Membrane proteins (which take up half of the membrane) determine what gets into and leaves the cell. •Glycolipids are found on the outer part of the cell membrane. Single Chain vs. Phospholipid • Single chain lipids were assumed to be the first of those to form cell membranes with the more complex phospholipids evolving later • Phospholipids can be synthesized in an abiotic environment without enzymes now • Phosphoplipid bilayers now make up the plasma cell membranes that regulate movement into and out of prokaryotic and eukaryotic cells. Single chain lipid http://web.nestucca.k12.or.us/nvhs/staff/whitehead/homewor http://clincancerres.aacrjournals.org/content/11/5/2018/F1. k.htm expansion Types of Lipids • Today Plasma Membranes are made primarily of phospholipids • It is thought that early membranes may have been made of simpler fatty acids. http://exploringorigins.org/fattyacids.html Properties of Fatty Acids • They are Ampipathic, meaning that they have a hydrophobic (“water hating”) end and a hydrophilic (water loving”) end.
    [Show full text]
  • Endoplasmic Reticulum-Plasma Membrane Contact Sites Integrate Sterol and Phospholipid Regulation
    RESEARCH ARTICLE Endoplasmic reticulum-plasma membrane contact sites integrate sterol and phospholipid regulation Evan Quon1☯, Yves Y. Sere2☯, Neha Chauhan2, Jesper Johansen1, David P. Sullivan2, Jeremy S. Dittman2, William J. Rice3, Robin B. Chan4, Gilbert Di Paolo4,5, Christopher T. Beh1,6*, Anant K. Menon2* 1 Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, Canada, 2 Department of Biochemistry, Weill Cornell Medical College, New York, New York, United States of a1111111111 America, 3 Simons Electron Microscopy Center at the New York Structural Biology Center, New York, New a1111111111 York, United States of America, 4 Department of Pathology and Cell Biology, Columbia University College of a1111111111 Physicians and Surgeons, New York, New York, United States of America, 5 Denali Therapeutics, South San a1111111111 Francisco, California, United States of America, 6 Centre for Cell Biology, Development, and Disease, Simon a1111111111 Fraser University, Burnaby, British Columbia, Canada ☯ These authors contributed equally to this work. * [email protected] (AKM); [email protected] (CTB) OPEN ACCESS Abstract Citation: Quon E, Sere YY, Chauhan N, Johansen J, Sullivan DP, Dittman JS, et al. (2018) Endoplasmic Tether proteins attach the endoplasmic reticulum (ER) to other cellular membranes, thereby reticulum-plasma membrane contact sites integrate sterol and phospholipid regulation. PLoS creating contact sites that are proposed to form platforms for regulating lipid homeostasis Biol 16(5): e2003864. https://doi.org/10.1371/ and facilitating non-vesicular lipid exchange. Sterols are synthesized in the ER and trans- journal.pbio.2003864 ported by non-vesicular mechanisms to the plasma membrane (PM), where they represent Academic Editor: Sandra Schmid, UT almost half of all PM lipids and contribute critically to the barrier function of the PM.
    [Show full text]
  • An Overview of Lipid Membrane Models for Biophysical Studies
    biomimetics Review Mimicking the Mammalian Plasma Membrane: An Overview of Lipid Membrane Models for Biophysical Studies Alessandra Luchini 1 and Giuseppe Vitiello 2,3,* 1 Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark; [email protected] 2 Department of Chemical, Materials and Production Engineering, University of Naples Federico II, Piazzale Tecchio 80, 80125 Naples, Italy 3 CSGI-Center for Colloid and Surface Science, via della Lastruccia 3, 50019 Sesto Fiorentino (Florence), Italy * Correspondence: [email protected] Abstract: Cell membranes are very complex biological systems including a large variety of lipids and proteins. Therefore, they are difficult to extract and directly investigate with biophysical methods. For many decades, the characterization of simpler biomimetic lipid membranes, which contain only a few lipid species, provided important physico-chemical information on the most abundant lipid species in cell membranes. These studies described physical and chemical properties that are most likely similar to those of real cell membranes. Indeed, biomimetic lipid membranes can be easily prepared in the lab and are compatible with multiple biophysical techniques. Lipid phase transitions, the bilayer structure, the impact of cholesterol on the structure and dynamics of lipid bilayers, and the selective recognition of target lipids by proteins, peptides, and drugs are all examples of the detailed information about cell membranes obtained by the investigation of biomimetic lipid membranes. This review focuses specifically on the advances that were achieved during the last decade in the field of biomimetic lipid membranes mimicking the mammalian plasma membrane. In particular, we provide a description of the most common types of lipid membrane models used for biophysical characterization, i.e., lipid membranes in solution and on surfaces, as well as recent examples of their Citation: Luchini, A.; Vitiello, G.
    [Show full text]
  • Membrane Proteins Are Associated with the Membrane of a Cell Or Particular Organelle and Are Generally More Problematic to Purify Than Water-Soluble Proteins
    Strategies for the Purification of Membrane Proteins Sinéad Marian Smith Department of Clinical Medicine, School of Medicine, Trinity College Dublin, Ireland. Email: [email protected] Abstract Although membrane proteins account for approximately 30 % of the coding regions of all sequenced genomes and play crucial roles in many fundamental cell processes, there are relatively few membranes with known 3D structure. This is likely due to technical challenges associated with membrane protein extraction, solubilization and purification. Membrane proteins are classified based on the level of interaction with membrane lipid bilayers, with peripheral membrane proteins associating non- covalently with the membrane, and integral membrane proteins associating more strongly by means of hydrophobic interactions. Generally speaking, peripheral membrane proteins can be purified by milder techniques than integral membrane proteins, whose extraction require phospholipid bilayer disruption by detergents. Here, important criteria for strategies of membrane protein purification are addressed, with a focus on the initial stages of membrane protein solublilization, where problems are most frequently are encountered. Protocols are outlined for the successful extraction of peripheral membrane proteins, solubilization of integral membrane proteins, and detergent removal which is important not only for retaining native protein stability and biological functions, but also for the efficiency of downstream purification techniques. Key Words: peripheral membrane protein, integral membrane protein, detergent, protein purification, protein solubilization. 1. Introduction Membrane proteins are associated with the membrane of a cell or particular organelle and are generally more problematic to purify than water-soluble proteins. Membrane proteins represent approximately 30 % of the open-reading frames of an organism’s genome (1-4), and play crucial roles in basic cell functions including signal transduction, energy production, nutrient uptake and cell-cell communication.
    [Show full text]
  • Reflux of Endoplasmic Reticulum Proteins to the Cytosol Yields Inactivation of Tumor Suppressors
    bioRxiv preprint doi: https://doi.org/10.1101/2020.04.13.038935; this version posted April 13, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. Reflux of Endoplasmic Reticulum proteins to the cytosol yields inactivation of tumor suppressors Daria Sicari1,2, Raphael Pineau1,2, Pierre-Jean Le Reste1,2,3, Luc Negroni4,5,6,7, Sophie Chat8, Aiman Mohtar9, Daniel Thomas8, Reynald Gillet8, M. Ted Hupp9,10, Eric Chevet1,2* and Aeid Igbaria1,2,11* 1Inserm U1242, University of Rennes, Rennes, France. 2Centre de lutte contre le cancer Eugène Marquis, Rennes, France. 3Neurosurgery Dept, University Hospital of Rennes, 35000 Rennes, France. 4Institut de Génétique et de Biologie Moléculaire et Cellulaire, 67404 Illkirch, France. 5Centre National de la Recherche Scientifique, UMR7104, 67404 Illkirch, France. 6Institut National de la Santé et de la Recherche Médicale, U1258, 67404 Illkirch, France. 7Université de Strasbourg, 67404 Illkirch, France. 8Univ. Rennes, CNRS, Institut de Génétique et Développement de Rennes (IGDR) UMR6290, 35000 Rennes, France. 9Edinburgh Cancer Research Centre at the Institute of Genetics and Molecular Medicine, Edinburgh University, Edinburgh, UK. 10International Centre for Cancer Vaccine Science, Gdansk, Poland. 11Department of Life Sciences, Ben-Gurion University of the Negev, Beer Sheva 8410501, Israel. *Correspondence: [email protected], or [email protected] ABSTRACT: In the past decades many studies reported Endoplasmic Reticulum (ER) resident proteins to localize to the cytosol but the mechanisms by which this occurs and whether these proteins exert cytosolic functions remain unknown. We found that select ER luminal proteins accumulate in the cytosol of glioblastoma cells isolated from mouse and human tumors.
    [Show full text]
  • ER-Phagy at a Glance Paolo Grumati1,*, Ivan Dikic1,2,‡ and Alexandra Stolz2,*
    © 2018. Published by The Company of Biologists Ltd | Journal of Cell Science (2018) 131, jcs217364. doi:10.1242/jcs.217364 CELL SCIENCE AT A GLANCE ER-phagy at a glance Paolo Grumati1,*, Ivan Dikic1,2,‡ and Alexandra Stolz2,* ABSTRACT function in response to ER stress signals. This task sharing reflects Selective autophagy represents the major quality control mechanism the complexity of the ER in terms of biological functions and that ensures proper turnover of exhausted or harmful organelles, morphology. In this Cell Science at a Glance article and the among them the endoplasmic reticulum (ER), which is fragmented accompanying poster, we summarize the most recent findings and delivered to the lysosome for degradation via a specific type of about ER-phagy in yeast and in mammalian cells. autophagy called ER-phagy. The recent discovery of ER-resident KEY WORDS: Autophagy, CCPG1, FAM134B, RTN3, SEC62, proteins that bind to mammalian Atg8 proteins has revealed that the Endoplasmic reticulum selective elimination of ER involves different receptors that are specific for different ER subdomains or ER stresses. FAM134B (also known as RETREG1) and RTN3 are reticulon-type proteins that are Introduction able to remodel the ER network and ensure the basal membrane The endoplasmic reticulum (ER) is the largest membrane-bound turnover. SEC62 and CCPG1 are transmembrane ER receptors that organelle in eukaryotic cells. Its complex morphology, which involves sheets, tubules and matrices (Chen et al., 2013; Friedman and Voeltz, 2011; Nixon-Abell et al., 2016), mirrors its diverse roles 1Institute of Biochemistry II, Goethe University Frankfurt - Medical Faculty, in a variety of physiological processes including autophagy University Hospital, 60590 Frankfurt am Main, Germany.
    [Show full text]
  • Endomembrane System
    Cell Structure & Function Cell Theory Cells are fundamental to biology Cells are the basic living units within organisms (all chemical rxns. of life take place within cells) All organisms are made of cells Single-celled organisms (bacteria/protists) Multicellular organisms (plants/animals/fungi) Cell Structure & Function Basic Aspects of Cell Structure & Function Plasma membrane Lipid bilayer Proteins DNA-containing region Cytoplasm Eukaryotic v. Prokaryotic cells Prokaryotic v. Eukaryotic Cells Two major classes of cells Prokaryotic cells (pro-, “before”) Cell lacks a “true” nucleus DNA is coiled in a nucleoid region Cells lack nuclear membrane Prokaryotic v. Eukaryotic Cells [attachment structure] [DNA location] [organelles that synthesize proteins] [enclosing the cytoplasm] [rigid structure outside the p.m. ] [jelly-like outer coating] [locomotion organelle] Prokaryotic v. Eukaryotic Cells Eukaryotic cells (eu-, “true”) Nucleus contains most of the cells nuclear material, DNA usually the largest organelle Bordered by a membranous envelope Prokaryotic v. Eukaryotic Cells Plant v. Animal Cells Both contain Plasma membrane (functions as a selective barrier) Nucleus (gene-containing organelle) Cytoplasm (region between nucleus and p.m.) Consists of organelles in a fluid (cytosol) Prokaryotic v. Eukaryotic Cells Plant v. Animal Cells Organelles Bordered by internal membranes Compartmentalizes the functions of a cell Maintains organelle’s unique environment Most organelles are found in both plant and animal cells Plant v. Animal Cells
    [Show full text]
  • ER-Phagy and Its Role in ER Homeostasis in Plants
    plants Review ER-Phagy and Its Role in ER Homeostasis in Plants Yan Bao 1,2,* and Diane C. Bassham 1,* 1 Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA 2 Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, MI 48824, USA * Correspondence: [email protected] (Y.B.); [email protected] (D.C.B.) Received: 19 November 2020; Accepted: 11 December 2020; Published: 14 December 2020 Abstract: The endoplasmic reticulum (ER) is the largest continuous membrane-bound cellular organelle and plays a central role in the biosynthesis of lipids and proteins and their distribution to other organelles. Autophagy is a conserved process that is required for recycling unwanted cellular components. Recent studies have implicated the ER as a membrane source for the formation of autophagosomes, vesicles that transport material to the vacuole during autophagy. When unfolded proteins accumulate in the ER and/or the ER lipid bilayer is disrupted, a condition known as ER stress results. During ER stress, ER membranes can also be engulfed through autophagy in a process termed ER-phagy. An interplay between ER stress responses and autophagy thus maintains the functions of the ER to allow cellular survival. In this review, we discuss recent progress in understanding ER-phagy in plants, including identification of regulatory factors and selective autophagy receptors. We also identify key unanswered questions in plant ER-phagy for future study. Keywords: autophagy; endoplasmic reticulum; ER stress; ER-phagy; unfolded protein response 1. Introduction Plants live in a world of ever-changing conditions; for survival, they need to adapt to the challenges of their surroundings to balance growth and stress responses [1,2].
    [Show full text]
  • And Cytosolic Proteases Endoplasmic Reticulum Aminopeptidase 1
    Processing of a Class I-Restricted Epitope from Tyrosinase Requires Peptide N -Glycanase and the Cooperative Action of Endoplasmic Reticulum Aminopeptidase 1 This information is current as and Cytosolic Proteases of September 28, 2021. Michelle L. Altrich-VanLith, Marina Ostankovitch, Joy M. Polefrone, Claudio A. Mosse, Jeffrey Shabanowitz, Donald F. Hunt and Victor H. Engelhard J Immunol 2006; 177:5440-5450; ; Downloaded from doi: 10.4049/jimmunol.177.8.5440 http://www.jimmunol.org/content/177/8/5440 http://www.jimmunol.org/ References This article cites 45 articles, 25 of which you can access for free at: http://www.jimmunol.org/content/177/8/5440.full#ref-list-1 Why The JI? Submit online. • Rapid Reviews! 30 days* from submission to initial decision by guest on September 28, 2021 • No Triage! Every submission reviewed by practicing scientists • Fast Publication! 4 weeks from acceptance to publication *average Subscription Information about subscribing to The Journal of Immunology is online at: http://jimmunol.org/subscription Permissions Submit copyright permission requests at: http://www.aai.org/About/Publications/JI/copyright.html Email Alerts Receive free email-alerts when new articles cite this article. Sign up at: http://jimmunol.org/alerts The Journal of Immunology is published twice each month by The American Association of Immunologists, Inc., 1451 Rockville Pike, Suite 650, Rockville, MD 20852 Copyright © 2006 by The American Association of Immunologists All rights reserved. Print ISSN: 0022-1767 Online ISSN: 1550-6606. The Journal of Immunology Processing of a Class I-Restricted Epitope from Tyrosinase Requires Peptide N-Glycanase and the Cooperative Action of Endoplasmic Reticulum Aminopeptidase 1 and Cytosolic Proteases1 Michelle L.
    [Show full text]
  • A Signal-Anchor Sequence Stimulates Signal Recognition Particle Binding to Ribosomes from Inside the Exit Tunnel
    A signal-anchor sequence stimulates signal recognition particle binding to ribosomes from inside the exit tunnel Uta Berndta,b,1, Stefan Oellerera,b,c,1, Ying Zhanga,b,c, Arthur E. Johnsond, and Sabine Rosperta,b,2 aInstitute of Biochemistry and Molecular Biology and bCenter for Biological Signalling Studies, University of Freiburg, Stefan-Meier-Strasse 17, D-79104 Freiburg, Germany; cFakulta¨t fu¨ r Biologie, University of Freiburg, Scha¨nzlestrasse 1, D-79104 Freiburg, Germany; and dDepartment of Molecular and Cellular Medicine, Texas A&M Health Science Center, 116 Reynolds Medical Building, College Station, TX 77843 Edited by Arthur Horwich, Yale University School of Medicine, New Haven, CT, and approved December 15, 2008 (received for review August 29, 2008) Sorting of eukaryotic membrane and secretory proteins depends direct interaction between SRP and the nascent chain. Previous on recognition of ribosome-bound nascent chain signal sequences studies have addressed the question of whether or not specific by the signal recognition particle (SRP). The current model suggests amino acid sequences of segments inside the tunnel can further that the SRP cycle is initiated when a signal sequence emerges from the affinity of SRP for RNCs (9, 10). Because signal sequences the ribosomal tunnel and binds to SRP. Then elongation is slowed would be prime candidates for such effects, this possibility was until the SRP-bound ribosome–nascent chain complex (RNC) is tested in the eukaryotic system by using RNCs carrying prep- targeted to the SRP receptor in the endoplasmic reticulum (ER) rolactin, a secreted protein with a cleavable signal sequence. membrane. The RNC is then transferred to the translocon, SRP is However, when nascent preprolactin was too short to exit the released, and translation resumes.
    [Show full text]
  • Review Questions Plasma Membrane
    Review Questions Plasma Membrane 1. What is the function of the plasma membrane? The plasma membrane forms the outer boundary of all cells. Described as semi-permeable, the membrane regulates the passage of atoms and molecules in and out of the cell. All membrane-bound organelles are also built of plasma membrane. 2. Draw a phospholipid bilayer and label the polar heads and the non-polar tails. The plasma membrane is made of a phospholipid bilayer. Phospholipids have a glycerol backbone attached to two fatty acid chains (one is unsaturated) and one phosphate group. The phosphate has a negative charge. The rest of the lipid is nonpolar. Water is attracted to the phosphate group and repelled by the rest of the molecule, so a phospholipid has a dual nature: a hydrophilic region (“head”) and a hydrophobic region (“tails”). When placed in water, the phospholipids form a bilayer. The heads face outward and the tails stay inside. The bilayer is semi-permeable barrier. Some substances can freely cross the membrane whereas others are stopped. 3. Why is the plasma membrane described as a “fluid mosaic”? The plasma membrane is a fluid because the phospholipid molecule is unsaturated. At room temperature, this causes the bilayer to have the consistency of salad oil. The term “mosaic” refers to the variety of embedded transmembrane proteins scattered throughout the membrane. 4. Why is cholesterol an important component of animal cell membranes? Cholesterol is a component of the cell membranes of animals. Cholesterol makes the membrane less fluid and therefore more impermeable to biological molecules. In a sense, cholesterol creates a more solid membrane and a more restrictive membrane.
    [Show full text]