51
|
Grossman JD, Camire EJ, Glynn CA, Neil CM, Seguinot BO, Perlstein DL. The Cfd1 Subunit of the Nbp35-Cfd1 Iron Sulfur Cluster Scaffolding Complex Controls Nucleotide Binding. Biochemistry 2019; 58:1587-1595. [PMID: 30785732 DOI: 10.1021/acs.biochem.8b00798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The cytosolic iron sulfur cluster assembly (CIA) scaffold biosynthesizes iron sulfur cluster cofactors for enzymes residing in the cytosol and the nucleus. In fungi and animals, it comprises two homologous ATPases, called Nbp35 and Cfd1 in yeast, which can form homodimeric and heterodimeric complexes. Both proteins are required for CIA function, but their individual roles are not well understood. Here we investigate the nucleotide affinity of each form of the scaffold for ATP and ADP to reveal any differences that could shed light on the functions of the different oligomeric forms of the protein or any distinct roles of the individual subunits. All forms of the CIA scaffold are specific for adenosine nucleotides and not guanosine nucleotides. Although the Cfd1 homodimer has no detectable ATPase activity, it binds ATP with an affinity comparable to that of the hydrolysis competent forms, Nbp352 and Nbp35-Cfd1. Titrations to determine the number of nucleotide binding sites combined with site-directed mutagenesis demonstrate that the nucleotide must bind to the Cfd1 subunit of the heterodimer before it can bind to Nbp35 and that the Cfd1 subunit is hydrolysis competent when bound to Nbp35 in the heterodimer. Altogether, our work reveals the distinct roles of the Nbp35 and Cfd1 subunits in their heterodimeric complex. Cfd1 controls nucleotide binding, and the Nbp35 subunit is required to activate nucleotide hydrolysis.
Collapse
Affiliation(s)
- John D Grossman
- Department of Chemistry , Boston University , Boston , Massachusetts 02215 , United States
| | - Eric J Camire
- Department of Chemistry , Boston University , Boston , Massachusetts 02215 , United States
| | - Calina A Glynn
- Department of Chemistry , Boston University , Boston , Massachusetts 02215 , United States
| | - Christopher M Neil
- Department of Chemistry , Boston University , Boston , Massachusetts 02215 , United States
| | - Bryan O Seguinot
- Department of Chemistry , Boston University , Boston , Massachusetts 02215 , United States
| | - Deborah L Perlstein
- Department of Chemistry , Boston University , Boston , Massachusetts 02215 , United States
| |
Collapse
|
52
|
Reichmann D, Voth W, Jakob U. Maintaining a Healthy Proteome during Oxidative Stress. Mol Cell 2019; 69:203-213. [PMID: 29351842 DOI: 10.1016/j.molcel.2017.12.021] [Citation(s) in RCA: 111] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 12/11/2017] [Accepted: 12/21/2017] [Indexed: 12/11/2022]
Abstract
Some of the most challenging stress conditions that organisms encounter during their lifetime involve the transient accumulation of reactive oxygen and chlorine species. Extremely reactive to amino acid side chains, these oxidants cause widespread protein unfolding and aggregation. It is therefore not surprising that cells draw on a variety of different strategies to counteract the damage and maintain a healthy proteome. Orchestrated largely by direct changes in the thiol oxidation status of key proteins, the response strategies involve all layers of protein protection. Reprogramming of basic biological functions helps decrease nascent protein synthesis and restore redox homeostasis. Mobilization of oxidative stress-activated chaperones and production of stress-resistant non-proteinaceous chaperones prevent irreversible protein aggregation. Finally, redox-controlled increase in proteasome activity removes any irreversibly damaged proteins. Together, these systems pave the way to restore protein homeostasis and enable organisms to survive stress conditions that are inevitable when living an aerobic lifestyle.
Collapse
Affiliation(s)
- Dana Reichmann
- Department of Biological Chemistry, The Alexander Silberman Institute of Life Sciences, Safra Campus Givat Ram, The Hebrew University of Jerusalem, Jerusalem 91904, Israel.
| | - Wilhelm Voth
- Department of Molecular, Cellular, and Developmental Biology and Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-1048, USA
| | - Ursula Jakob
- Department of Molecular, Cellular, and Developmental Biology and Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109-1048, USA.
| |
Collapse
|
53
|
Benarroch R, Austin JM, Ahmed F, Isaacson RL. The roles of cytosolic quality control proteins, SGTA and the BAG6 complex, in disease. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2019; 114:265-313. [PMID: 30635083 PMCID: PMC7102839 DOI: 10.1016/bs.apcsb.2018.11.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
SGTA is a co-chaperone that, in collaboration with the complex of BAG6/UBL4A/TRC35, facilitates the biogenesis and quality control of hydrophobic proteins, protecting them from the aqueous cytosolic environment. This work includes targeting tail-anchored proteins to their resident membranes, sorting of membrane and secretory proteins that mislocalize to the cytoplasm and endoplasmic reticulum-associated degradation of misfolded proteins. Since these functions are all vital for the cell's continued proteostasis, their disruption poses a threat to the cell, with a particular risk of protein aggregation, a phenomenon that underpins many diseases. Although the specific disease implications of machinery involved in quality control of hydrophobic substrates are poorly understood, here we summarize much of the available information on this topic.
Collapse
Affiliation(s)
- Rashi Benarroch
- Department of Chemistry, King's College London, London, United Kingdom
| | - Jennifer M Austin
- Department of Chemistry, King's College London, London, United Kingdom
| | - Fahmeda Ahmed
- Department of Chemistry, King's College London, London, United Kingdom
| | - Rivka L Isaacson
- Department of Chemistry, King's College London, London, United Kingdom.
| |
Collapse
|
54
|
Mateja A, Keenan RJ. A structural perspective on tail-anchored protein biogenesis by the GET pathway. Curr Opin Struct Biol 2018; 51:195-202. [PMID: 30173121 DOI: 10.1016/j.sbi.2018.07.009] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Revised: 07/19/2018] [Accepted: 07/20/2018] [Indexed: 12/16/2022]
Abstract
Many tail-anchored (TA) membrane proteins are targeted to and inserted into the endoplasmic reticulum (ER) by the `guided entry of tail-anchored proteins' (GET) pathway. This post-translational pathway uses transmembrane-domain selective cytosolic chaperones for targeting, and a dedicated membrane protein complex for insertion. The past decade has seen rapid progress towards defining the molecular basis of TA protein biogenesis by the GET pathway. Here we review the mechanisms underlying each step of the pathway, emphasizing recent structural work and highlighting key questions that await future studies.
Collapse
Affiliation(s)
- Agnieszka Mateja
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
| |
Collapse
|
55
|
Kempf G, Stjepanovic G, Sloan J, Hendricks A, Lapouge K, Sinning I. The Escherichia coli SRP Receptor Forms a Homodimer at the Membrane. Structure 2018; 26:1440-1450.e5. [PMID: 30146170 DOI: 10.1016/j.str.2018.07.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2018] [Revised: 06/14/2018] [Accepted: 07/22/2018] [Indexed: 01/19/2023]
Abstract
The Escherichia coli signal recognition particle (SRP) receptor, FtsY, plays a fundamental role in co-translational targeting of membrane proteins via the SRP pathway. Efficient targeting relies on membrane interaction of FtsY and heterodimerization with the SRP protein Ffh, which is driven by detachment of α helix (αN1) in FtsY. Here we show that apart from the heterodimer, FtsY forms a nucleotide-dependent homodimer on the membrane, and upon αN1 removal also in solution. Homodimerization triggers reciprocal stimulation of GTP hydrolysis and occurs in vivo. Biochemical characterization together with integrative modeling suggests that the homodimer employs the same interface as the heterodimer. Structure determination of FtsY NG+1 with GMPPNP shows that a dimerization-induced conformational switch of the γ-phosphate is conserved in Escherichia coli, filling an important gap in SRP GTPase activation. Our findings add to the current understanding of SRP GTPases and may challenge previous studies that did not consider homodimerization of FtsY.
Collapse
Affiliation(s)
- Georg Kempf
- Heidelberg University Biochemistry Centre, Heidelberg 69120, Germany
| | - Goran Stjepanovic
- Heidelberg University Biochemistry Centre, Heidelberg 69120, Germany
| | - Jeremy Sloan
- Heidelberg University Biochemistry Centre, Heidelberg 69120, Germany
| | - Astrid Hendricks
- Heidelberg University Biochemistry Centre, Heidelberg 69120, Germany
| | - Karine Lapouge
- Heidelberg University Biochemistry Centre, Heidelberg 69120, Germany
| | - Irmgard Sinning
- Heidelberg University Biochemistry Centre, Heidelberg 69120, Germany.
| |
Collapse
|
56
|
Manu M, Ghosh D, Chaudhari BP, Ramasamy S. Analysis of tail-anchored protein translocation pathway in plants. Biochem Biophys Rep 2018; 14:161-167. [PMID: 29872748 PMCID: PMC5986991 DOI: 10.1016/j.bbrep.2018.05.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Tail-anchored (TA) proteins are a special class of membrane proteins that carry out vital functions in all living cells. Targeting mechanisms of TA proteins are investigated as the best example for post-translational protein targeting in yeast. Of the several mechanisms, Guided Entry of Tail-anchored protein (GET) pathway plays a major role in TA protein targeting. Many in silico and in vivo analyses are geared to identify TA proteins and their targeting mechanisms in different systems including Arabidopsis thaliana. Yet, crop plants that grow in specific and/or different conditions are not investigated for the presence of TA proteins and GET pathway. This study majorly investigates GET pathway in two crop plants, Oryza sativa subsp. Indica and Solanum tuberosum, through detailed in silico analysis. 508 and 912 TA proteins are identified in Oryza sativa subsp. Indica and Solanum tuberosum respectively and their localization with respect to endoplasmic reticulum (ER), mitochondria, and chloroplast has been delineated. Similarly, the associated GET proteins are identified (Get1, Get3 and Get4) and their structural inferences are elucidated using homology modelling. Get3 models are based on yeast Get3. The cytoplasmic Get3 from O. sativa is identified to be very similar to yeast Get3 with conserved P-loop and TA binding groove. Three cytoplasmic Get3s are identified for S. tuberosum. Taken together, this is the first study to identify TA proteins and GET components in Oryza sativa subsp. Indica and Solanum tuberosum, forming the basis for any further experimental characterization of TA targeting and GET pathway mechanisms in crop plants.
Collapse
Affiliation(s)
- M.S. Manu
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory, Pune 411008, India
| | - Deepanjan Ghosh
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory, Pune 411008, India
| | - Bhushan P. Chaudhari
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory, Pune 411008, India
| | - Sureshkumar Ramasamy
- Biochemical Sciences Division, CSIR-National Chemical Laboratory, Pune 411008 India
- Academy of Scientific and Innovative Research (AcSIR), CSIR-National Chemical Laboratory, Pune 411008, India
| |
Collapse
|
57
|
Abstract
Proper localization of membrane proteins is essential for the function of biological membranes and for the establishment of organelle identity within a cell. Molecular machineries that mediate membrane protein biogenesis need to not only achieve a high degree of efficiency and accuracy, but also prevent off-pathway aggregation events that can be detrimental to cells. The posttranslational targeting of tail-anchored proteins (TAs) provides tractable model systems to probe these fundamental issues. Recent advances in understanding TA-targeting pathways reveal sophisticated molecular machineries that drive and regulate these processes. These findings also suggest how an interconnected network of targeting factors, cochaperones, and quality control machineries together ensures robust membrane protein biogenesis.
Collapse
Affiliation(s)
- Un Seng Chio
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125; , ,
| | - Hyunju Cho
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125; , ,
| | - Shu-Ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125; , ,
| |
Collapse
|
58
|
Zalisko BE, Chan C, Denic V, Rock RS, Keenan RJ. Tail-Anchored Protein Insertion by a Single Get1/2 Heterodimer. Cell Rep 2018; 20:2287-2293. [PMID: 28877464 DOI: 10.1016/j.celrep.2017.08.035] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 06/27/2017] [Accepted: 08/07/2017] [Indexed: 01/19/2023] Open
Abstract
The Get1/2 transmembrane complex drives the insertion of tail-anchored (TA) proteins from the cytosolic chaperone Get3 into the endoplasmic reticulum membrane. Mechanistic insight into how Get1/2 coordinates this process is confounded by a lack of understanding of the basic architecture of the complex. Here, we define the oligomeric state of full-length Get1/2 in reconstituted lipid bilayers by combining single-molecule and bulk fluorescence measurements with quantitative in vitro insertion analysis. We show that a single Get1/2 heterodimer is sufficient for insertion and demonstrate that the conserved cytosolic regions of Get1 and Get2 bind asymmetrically to opposing subunits of the Get3 homodimer. Altogether, our results define a simplified model for how Get1/2 and Get3 coordinate TA protein insertion.
Collapse
Affiliation(s)
- Benjamin E Zalisko
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Charlene Chan
- Department of Molecular and Cellular Biology, Northwest Labs, Harvard University, Cambridge, MA 02138, USA
| | - Vladimir Denic
- Department of Molecular and Cellular Biology, Northwest Labs, Harvard University, Cambridge, MA 02138, USA.
| | - Ronald S Rock
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
| |
Collapse
|
59
|
Norlin S, Parekh V, Edlund H. The ATPase activity of Asna1/TRC40 is required for pancreatic progenitor cell survival. Development 2018; 145:dev.154468. [PMID: 29180572 PMCID: PMC5825870 DOI: 10.1242/dev.154468] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2017] [Accepted: 11/10/2017] [Indexed: 12/13/2022]
Abstract
Asna1, also known as TRC40, is implicated in the delivery of tail-anchored (TA) proteins into the endoplasmic reticulum (ER), in vesicle-mediated transport, and in chaperoning unfolded proteins during oxidative stress/ATP depletion. Here, we show that Asna1 inactivation in pancreatic progenitor cells leads to redistribution of the Golgi TA SNARE proteins syntaxin 5 and syntaxin 6, Golgi fragmentation, and accumulation of cytosolic p62+ puncta. Asna1−/− multipotent progenitor cells (MPCs) selectively activate integrated stress response signaling and undergo apoptosis, thereby disrupting endocrine and acinar cell differentiation, resulting in pancreatic agenesis. Rescue experiments implicate the Asna1 ATPase activity and a CXXC di-cysteine motif in ensuring Golgi integrity, syntaxin 5 localization and MPC survival. Ex vivo inhibition of retrograde transport reproduces the perturbed Golgi morphology, and syntaxin 5 and syntaxin 6 expression, whereas modulation of p53 activity, using PFT-α and Nutlin-3, prevents or reproduces apoptosis in Asna1-deficient and wild-type MPCs, respectively. These findings support a role for the Asna1 ATPase activity in ensuring the survival of pancreatic MPCs, possibly by counteracting p53-mediated apoptosis. Summary: Conditional inactivation of Asna1/TRC40 in pancreatic progenitor cells results in pancreatic agenesis resulting from pancreatic progenitor cell apoptosis, thus revealing a crucial role for Asna1/TRC40 in pancreatic progenitor cell survival.
Collapse
Affiliation(s)
- Stefan Norlin
- Umeå Centre for Molecular Medicine, Umeå University, SE-901 87 Umeå, Sweden
| | - Vishal Parekh
- Umeå Centre for Molecular Medicine, Umeå University, SE-901 87 Umeå, Sweden
| | - Helena Edlund
- Umeå Centre for Molecular Medicine, Umeå University, SE-901 87 Umeå, Sweden
| |
Collapse
|
60
|
Grossman JD, Camire EJ, Perlstein DL. Approaches to Interrogate the Role of Nucleotide Hydrolysis by Metal Trafficking NTPases: The Nbp35-Cfd1 Iron-Sulfur Cluster Scaffold as a Case Study. Methods Enzymol 2018; 599:293-325. [PMID: 29746244 DOI: 10.1016/bs.mie.2017.11.005] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Nucleotide hydrolases play integral yet poorly understood roles in several metallocluster biosynthetic pathways. For example, the cytosolic iron-sulfur cluster assembly (CIA) is initiated by the CIA scaffold, an ATPase which builds new iron-sulfur clusters for proteins localized to the cytosol and the nucleus in eukaryotic organisms. While in vivo studies have demonstrated the scaffold's nucleotide hydrolase domain is vital for its function, in vitro approaches have not revealed tight allosteric coupling between the cluster scaffolding site and the ATPase site. Thus, the role of ATP hydrolysis has been hard to pinpoint. Herein, we describe methods to probe the nucleotide affinity and hydrolysis activity of the CIA scaffold from yeast, which is comprised of two homologous polypeptides called Nbp35 and Cfd1. In particular, we report two different equilibrium binding assays that make use of commercially available fluorescent nucleotide analogs. Importantly, these assays can be applied to probe nucleotide affinity of both the apo- and holo-forms of the CIA scaffold. Generally, these fluorescent nucleotide analogs have been underutilized to probe metal trafficking NTPase because one of the most commonly used probes, mantATP, which is labeled with the methylanthraniloyl probe via the 2' or 3' sugar hydroxyls, has an absorption which overlaps with the UV-Vis features of many metal-binding proteins. However, by exploiting analogs like BODIPY-FL and trinitrophenyl-labeled nucleotides which have better photophysical properties for metalloprotein applications, these approaches have the potential to reveal the mechanistic underpinnings of NTPases required for metallocluster biosynthesis.
Collapse
|
61
|
Shao S, Rodrigo-Brenni MC, Kivlen MH, Hegde RS. Mechanistic basis for a molecular triage reaction. Science 2017; 355:298-302. [PMID: 28104892 DOI: 10.1126/science.aah6130] [Citation(s) in RCA: 99] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 12/22/2016] [Indexed: 01/24/2023]
Abstract
Newly synthesized proteins are triaged between biosynthesis and degradation to maintain cellular homeostasis, but the decision-making mechanisms are unclear. We reconstituted the core reactions for membrane targeting and ubiquitination of nascent tail-anchored membrane proteins to understand how their fate is determined. The central six-component triage system is divided into an uncommitted client-SGTA complex, a self-sufficient targeting module, and an embedded but self-sufficient quality control module. Client-SGTA engagement of the targeting module induces rapid, private, and committed client transfer to TRC40 for successful biosynthesis. Commitment to ubiquitination is dictated primarily by comparatively slower client dissociation from SGTA and nonprivate capture by the BAG6 subunit of the quality control module. Our results provide a paradigm for how priority and time are encoded within a multichaperone triage system.
Collapse
Affiliation(s)
- Sichen Shao
- Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Monica C Rodrigo-Brenni
- Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Maryann H Kivlen
- Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Ramanujan S Hegde
- Medical Research Council Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK.
| |
Collapse
|
62
|
A protean clamp guides membrane targeting of tail-anchored proteins. Proc Natl Acad Sci U S A 2017; 114:E8585-E8594. [PMID: 28973888 DOI: 10.1073/pnas.1708731114] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Proper localization of proteins to target membranes is a fundamental cellular process. How the nature and dynamics of the targeting complex help guide substrate proteins to the target membrane is not understood for most pathways. Here, we address this question for the conserved ATPase guided entry of tail-anchored protein 3 (Get3), which targets the essential class of tail-anchored proteins (TAs) to the endoplasmic reticulum (ER). Single-molecule fluorescence spectroscopy showed that, contrary to previous models of a static closed Get3•TA complex, Get3 samples open conformations on the submillisecond timescale upon TA binding, generating a fluctuating "protean clamp" that stably traps the substrate. Point mutations at the ATPase site bias Get3 toward closed conformations, uncouple TA binding from induced Get3•Get4/5 disassembly, and inhibit the ER targeting of the Get3•TA complex. These results demonstrate an essential role of substrate-induced Get3 dynamics in driving TA targeting to the membrane, and reveal a tightly coupled channel of communication between the TA-binding site, ATPase site, and effector interaction surfaces of Get3. Our results provide a precedent for large-scale dynamics in a substrate-bound chaperone, which provides an effective mechanism to retain substrate proteins with high affinity while also generating functional switches to drive vectorial cellular processes.
Collapse
|
63
|
Voth W, Jakob U. Stress-Activated Chaperones: A First Line of Defense. Trends Biochem Sci 2017; 42:899-913. [PMID: 28893460 DOI: 10.1016/j.tibs.2017.08.006] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Revised: 08/18/2017] [Accepted: 08/21/2017] [Indexed: 10/18/2022]
Abstract
Proteins are constantly challenged by environmental stress conditions that threaten their structure and function. Especially problematic are oxidative, acid, and severe heat stress which induce very rapid and widespread protein unfolding and generate conditions that make canonical chaperones and/or transcriptional responses inadequate to protect the proteome. We review here recent advances in identifying and characterizing stress-activated chaperones which are inactive under non-stress conditions but become potent chaperones under specific protein-unfolding stress conditions. We discuss the post-translational mechanisms by which these chaperones sense stress, and consider the role that intrinsic disorder plays in their regulation and function. We examine their physiological roles under both non-stress and stress conditions, their integration into the cellular proteostasis network, and their potential as novel therapeutic targets.
Collapse
Affiliation(s)
- Wilhelm Voth
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Molecular Biology, Universitätsmedizin Göttingen, 37073 Göttingen, Germany
| | - Ursula Jakob
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Department of Biological Chemistry, University of Michigan, Ann Arbor, MI 48109, USA.
| |
Collapse
|
64
|
Maestre-Reyna M, Wu SM, Chang YC, Chen CC, Maestre-Reyna A, Wang AHJ, Chang HY. In search of tail-anchored protein machinery in plants: reevaluating the role of arsenite transporters. Sci Rep 2017; 7:46022. [PMID: 28382961 PMCID: PMC5382584 DOI: 10.1038/srep46022] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 03/07/2017] [Indexed: 11/09/2022] Open
Abstract
Although the mechanisms underlying selective targeting of tail-anchored (TA) membrane proteins are well established in mammalian and yeast cells, little is known about their role in mediating intracellular membrane trafficking in plant cells. However, a recent study suggested that, in green algae, arsenite transporters located in the cytosol (ArsA1 and ArsA2) control the insertion of TA proteins into the membrane-bound organelles. In the present work, we overproduced and purified these hydrophilic proteins to near homogeneity. The analysis of their catalytic properties clearly demonstrates that C. reinhardtii ArsA proteins exhibit oxyanion-independent ATPase activity, as neither arsenite nor antimonite showed strong effects. Co-expression of ArsA proteins with TA-transmembrane regions showed not only that the former interact with the latter, but that ArsA1 does not share the same ligand specificity as ArsA2. Together with a structural model and molecular dynamics simulations, we propose that C. reinhadtii ArsA proteins are not arsenite transporters, but a TA-protein targeting factor. Further, we propose that ArsA targeting specificity is achieved at the ligand level, with ArsA1 mainly carrying TA-proteins to the chloroplast, while ArsA2 to the endoplasmic reticulum.
Collapse
Affiliation(s)
| | - Shu-Mei Wu
- Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Yu-Ching Chang
- Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan
| | - Chi-Chih Chen
- Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan
- Doctoral Degree Program in Marine Biotechnology, National Sun Yat-Sen University, 70 Lien-Hai Road, Kaohsiung 80424, Taiwan
- Doctoral Degree Program in Marine Biotechnology, Academia Sinica, 128 Academia Road, Section 2, Nankang, Taipei 11529, Taiwan
| | - Alvaro Maestre-Reyna
- Escuela Tecnica Superior de Ingenierios Industriales, Universidad Politecnica de Valencia, Valencia, Spain
| | - Andrew H.-J. Wang
- Institute of Biological Chemistry, Academia Sinica, Taipei, Taiwan
- Core Facilities for Protein Structural Analysis, Academia Sinica, Taipei, Taiwan
- PhD Program for Translational Medicine, College of Medical Science and Technology, Taipei Medical University, Taipei, Taiwan
| | - Hsin-Yang Chang
- Department of Marine Biotechnology and Resources, National Sun Yat-sen University, Kaohsiung, Taiwan
- Doctoral Degree Program in Marine Biotechnology, National Sun Yat-Sen University, 70 Lien-Hai Road, Kaohsiung 80424, Taiwan
- The Asia-Pacific Ocean Research Center, National Sun Yat-sen University, Kaohsiung 804, Taiwan
| |
Collapse
|
65
|
Xing S, Mehlhorn DG, Wallmeroth N, Asseck LY, Kar R, Voss A, Denninger P, Schmidt VAF, Schwarzländer M, Stierhof YD, Grossmann G, Grefen C. Loss of GET pathway orthologs in Arabidopsis thaliana causes root hair growth defects and affects SNARE abundance. Proc Natl Acad Sci U S A 2017; 114:E1544-E1553. [PMID: 28096354 PMCID: PMC5338382 DOI: 10.1073/pnas.1619525114] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are key players in cellular trafficking and coordinate vital cellular processes, such as cytokinesis, pathogen defense, and ion transport regulation. With few exceptions, SNAREs are tail-anchored (TA) proteins, bearing a C-terminal hydrophobic domain that is essential for their membrane integration. Recently, the Guided Entry of Tail-anchored proteins (GET) pathway was described in mammalian and yeast cells that serve as a blueprint of TA protein insertion [Schuldiner M, et al. (2008) Cell 134(4):634-645; Stefanovic S, Hegde RS (2007) Cell 128(6):1147-1159]. This pathway consists of six proteins, with the cytosolic ATPase GET3 chaperoning the newly synthesized TA protein posttranslationally from the ribosome to the endoplasmic reticulum (ER) membrane. Structural and biochemical insights confirmed the potential of pathway components to facilitate membrane insertion, but the physiological significance in multicellular organisms remains to be resolved. Our phylogenetic analysis of 37 GET3 orthologs from 18 different species revealed the presence of two different GET3 clades. We identified and analyzed GET pathway components in Arabidopsis thaliana and found reduced root hair elongation in Atget lines, possibly as a result of reduced SNARE biogenesis. Overexpression of AtGET3a in a receptor knockout (KO) results in severe growth defects, suggesting presence of alternative insertion pathways while highlighting an intricate involvement for the GET pathway in cellular homeostasis of plants.
Collapse
Affiliation(s)
- Shuping Xing
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Dietmar Gerald Mehlhorn
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Niklas Wallmeroth
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Lisa Yasmin Asseck
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Ritwika Kar
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Alessa Voss
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany
| | - Philipp Denninger
- Centre for Organismal Studies, CellNetworks Excellence Cluster, University of Heidelberg, 69120 Heidelberg, Germany
| | - Vanessa Aphaia Fiona Schmidt
- Centre for Organismal Studies, CellNetworks Excellence Cluster, University of Heidelberg, 69120 Heidelberg, Germany
| | - Markus Schwarzländer
- Institute of Crop Science and Resource Conservation, University of Bonn, 53113 Bonn, Germany
| | - York-Dieter Stierhof
- Centre for Plant Molecular Biology, Microscopy, University of Tübingen, 72076 Tuebingen, Germany
| | - Guido Grossmann
- Centre for Organismal Studies, CellNetworks Excellence Cluster, University of Heidelberg, 69120 Heidelberg, Germany
| | - Christopher Grefen
- Centre for Plant Molecular Biology, Developmental Genetics, University of Tübingen, 72076 Tuebingen, Germany;
| |
Collapse
|
66
|
Srivastava R, Zalisko BE, Keenan RJ, Howell SH. The GET System Inserts the Tail-Anchored Protein, SYP72, into Endoplasmic Reticulum Membranes. PLANT PHYSIOLOGY 2017; 173:1137-1145. [PMID: 27923985 PMCID: PMC5291014 DOI: 10.1104/pp.16.00928] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2016] [Accepted: 12/04/2016] [Indexed: 05/25/2023]
Abstract
The Arabidopsis (Arabidopsis thaliana) genome encodes homologs of the Guided Entry of Tail (GET)-anchored protein system for the posttranslational insertion of tail-anchored (TA) proteins into endoplasmic reticulum (ER) membranes. In yeast, TA proteins are loaded onto the cytosolic targeting factor Get3 and are then delivered to the membrane-associated Get1/2 complex for insertion into ER membranes. The role of the GET system in Arabidopsis was investigated by monitoring the membrane insertion of a tail-anchored protein, SYP72, a syntaxin. SYP72 bound to yeast Get3 in vitro, forming a Get3-SYP72 fusion complex that could be inserted into yeast GET1/2-containing proteoliposomes. The Arabidopsis GET system functioned in vivo to insert TA proteins into ER membranes as demonstrated by the fact that the YFP-tagged SYP72 localized to the ER in wild-type plants but accumulated as cytoplasmic inclusions in get1, get3, or get4 mutants. The GET mutants get1 and get3 were less tolerant of ER stress agents and showed symptoms of ER stress even under unstressed conditions. Hence, the GET system is responsible for the insertion of TA proteins into the ER in Arabidopsis, and mutants with GET dysfunctions are more susceptible to ER stress.
Collapse
Affiliation(s)
- Renu Srivastava
- Plant Sciences Institute and Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50010 (R.S., S.H.H.); and
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637 (B.E.Z., R.J.K.)
| | - Benjamin E Zalisko
- Plant Sciences Institute and Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50010 (R.S., S.H.H.); and
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637 (B.E.Z., R.J.K.)
| | - Robert J Keenan
- Plant Sciences Institute and Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50010 (R.S., S.H.H.); and
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637 (B.E.Z., R.J.K.)
| | - Stephen H Howell
- Plant Sciences Institute and Department of Genetics, Development, and Cell Biology, Iowa State University, Ames, Iowa 50010 (R.S., S.H.H.); and
- Department of Biochemistry and Molecular Biology, The University of Chicago, Chicago, Illinois 60637 (B.E.Z., R.J.K.)
| |
Collapse
|
67
|
ATPase and GTPase Tangos Drive Intracellular Protein Transport. Trends Biochem Sci 2016; 41:1050-1060. [PMID: 27658684 DOI: 10.1016/j.tibs.2016.08.012] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2016] [Revised: 08/18/2016] [Accepted: 08/23/2016] [Indexed: 11/24/2022]
Abstract
The GTPase superfamily of proteins provides molecular switches to regulate numerous cellular processes. The 'GTPase switch' paradigm, in which external regulatory factors control the switch of a GTPase between 'on' and 'off' states, has been used to interpret the regulatory mechanism of many GTPases. However, recent work unveiled a class of nucleotide hydrolases that do not adhere to this classical paradigm. Instead, they use nucleotide-dependent dimerization cycles to regulate key cellular processes. In this review article, recent studies of dimeric GTPases and ATPases involved in intracellular protein targeting are summarized. It is suggested that these proteins can use the conformational plasticity at their dimer interface to generate multiple points of regulation, thereby providing the driving force and spatiotemporal coordination of complex cellular pathways.
Collapse
|
68
|
Shigemitsu S, Cao W, Terada T, Shimizu K. Development of a prediction system for tail-anchored proteins. BMC Bioinformatics 2016; 17:378. [PMID: 27634135 PMCID: PMC5025589 DOI: 10.1186/s12859-016-1202-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2016] [Accepted: 08/24/2016] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND "Tail-anchored (TA) proteins" is a collective term for transmembrane proteins with a C-terminal transmembrane domain (TMD) and without an N-terminal signal sequence. TA proteins account for approximately 3-5 % of all transmembrane proteins that mediate membrane fusion, regulation of apoptosis, and vesicular transport. The combined use of TMD and signal sequence prediction tools is typically required to predict TA proteins. RESULTS Here we developed a prediction system named TAPPM that predicted TA proteins solely from target amino acid sequences according to the knowledge of the sequence features of TMDs and the peripheral regions of TA proteins. Manually curated TA proteins were collected from published literature. We constructed hidden markov models of TA proteins as well as three different types of transmembrane proteins with similar structures and compared their likelihoods as TA proteins. CONCLUSIONS Using the HMM models, we achieved high prediction accuracy; area under the receiver operator curve values reaching 0.963. A command line tool written in Python is available at https://github.com/davecao/tappm_cli .
Collapse
Affiliation(s)
- Shunsuke Shigemitsu
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan
| | - Wei Cao
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan
| | - Tohru Terada
- Agricultural Bioinformatics Research Unit, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan
| | - Kentaro Shimizu
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657 Japan
| |
Collapse
|
69
|
Vogl C, Panou I, Yamanbaeva G, Wichmann C, Mangosing SJ, Vilardi F, Indzhykulian AA, Pangršič T, Santarelli R, Rodriguez-Ballesteros M, Weber T, Jung S, Cardenas E, Wu X, Wojcik SM, Kwan KY, Del Castillo I, Schwappach B, Strenzke N, Corey DP, Lin SY, Moser T. Tryptophan-rich basic protein (WRB) mediates insertion of the tail-anchored protein otoferlin and is required for hair cell exocytosis and hearing. EMBO J 2016; 35:2536-2552. [PMID: 27458190 DOI: 10.15252/embj.201593565] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Revised: 05/29/2016] [Accepted: 06/10/2016] [Indexed: 12/21/2022] Open
Abstract
The transmembrane recognition complex (TRC40) pathway mediates the insertion of tail-anchored (TA) proteins into membranes. Here, we demonstrate that otoferlin, a TA protein essential for hair cell exocytosis, is inserted into the endoplasmic reticulum (ER) via the TRC40 pathway. We mutated the TRC40 receptor tryptophan-rich basic protein (Wrb) in hair cells of zebrafish and mice and studied the impact of defective TA protein insertion. Wrb disruption reduced otoferlin levels in hair cells and impaired hearing, which could be restored in zebrafish by transgenic Wrb rescue and otoferlin overexpression. Wrb-deficient mouse inner hair cells (IHCs) displayed normal numbers of afferent synapses, Ca2+ channels, and membrane-proximal vesicles, but contained fewer ribbon-associated vesicles. Patch-clamp of IHCs revealed impaired synaptic vesicle replenishment. In vivo recordings from postsynaptic spiral ganglion neurons showed a use-dependent reduction in sound-evoked spiking, corroborating the notion of impaired IHC vesicle replenishment. A human mutation affecting the transmembrane domain of otoferlin impaired its ER targeting and caused an auditory synaptopathy. We conclude that the TRC40 pathway is critical for hearing and propose that otoferlin is an essential substrate of this pathway in hair cells.
Collapse
Affiliation(s)
- Christian Vogl
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 889, University of Göttingen, Göttingen, Germany
| | - Iliana Panou
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Göttingen Graduate School for Neurosciences, Biophysics and Molecular Biosciences, University of Göttingen, Göttingen, Germany
| | - Gulnara Yamanbaeva
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Auditory Systems Physiology Group and InnerEarLab, Department of Otolaryngology, University of Göttingen Medical Center, Göttingen, Germany
| | - Carolin Wichmann
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Molecular Architecture of Synapses Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Sara J Mangosing
- Otolaryngology Division, Department of Surgery, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Fabio Vilardi
- Institute of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Artur A Indzhykulian
- Howard Hughes Medical Institute and Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Tina Pangršič
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Synaptic Physiology of Mammalian Vestibular Hair Cells Junior Research Group, Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Rosamaria Santarelli
- Department of Neurosciences, University of Padova, Padova, Italy.,Audiology and Phoniatrics Service, Treviso Regional Hospital, Treviso, Italy
| | | | - Thomas Weber
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany
| | - Sangyong Jung
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Elena Cardenas
- Otolaryngology Division, Department of Surgery, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Xudong Wu
- Howard Hughes Medical Institute and Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Sonja M Wojcik
- Department of Molecular Neurobiology, Max-Planck-Institute for Experimental Medicine, Göttingen, Germany
| | - Kelvin Y Kwan
- W. M. Keck Center for Collaborative Neuroscience, Nelson Lab-D250, Rutgers University, Piscataway, NJ, USA
| | - Ignacio Del Castillo
- Servicio de Genetica, Hospital Universitario Ramon y Cajal, IRYCIS, Madrid, Spain.,Centro de Investigacion Biomedica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Blanche Schwappach
- Institute of Molecular Biology, University Medical Center Göttingen, Göttingen, Germany
| | - Nicola Strenzke
- Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Auditory Systems Physiology Group and InnerEarLab, Department of Otolaryngology, University of Göttingen Medical Center, Göttingen, Germany
| | - David P Corey
- Howard Hughes Medical Institute and Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Shuh-Yow Lin
- Otolaryngology Division, Department of Surgery, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Tobias Moser
- Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany .,Collaborative Research Center 889, University of Göttingen, Göttingen, Germany.,Synaptic Nanophysiology Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany.,Center for Nanoscale Microscopy and Molecular Physiology of the Brain, University Medical Center Göttingen, Göttingen, Germany
| |
Collapse
|
70
|
Itakura E, Zavodszky E, Shao S, Wohlever ML, Keenan RJ, Hegde RS. Ubiquilins Chaperone and Triage Mitochondrial Membrane Proteins for Degradation. Mol Cell 2016; 63:21-33. [PMID: 27345149 PMCID: PMC4942676 DOI: 10.1016/j.molcel.2016.05.020] [Citation(s) in RCA: 168] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2016] [Revised: 04/04/2016] [Accepted: 05/16/2016] [Indexed: 12/14/2022]
Abstract
We investigated how mitochondrial membrane proteins remain soluble in the cytosol until their delivery to mitochondria or degradation at the proteasome. We show that Ubiquilin family proteins bind transmembrane domains in the cytosol to prevent aggregation and temporarily allow opportunities for membrane targeting. Over time, Ubiquilins recruit an E3 ligase to ubiquitinate bound clients. The attached ubiquitin engages Ubiquilin's UBA domain, normally bound to an intramolecular UBL domain, and stabilizes the Ubiquilin-client complex. This conformational change precludes additional chances at membrane targeting for the client, while simultaneously freeing Ubiquilin's UBL domain for targeting to the proteasome. Loss of Ubiquilins by genetic ablation or sequestration in polyglutamine aggregates leads to accumulation of non-inserted mitochondrial membrane protein precursors. These findings define Ubiquilins as a family of chaperones for cytosolically exposed transmembrane domains and explain how they use ubiquitin to triage clients for degradation via coordinated intra- and intermolecular interactions.
Collapse
Affiliation(s)
- Eisuke Itakura
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK; Department of Biology, Faculty of Science, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan
| | - Eszter Zavodszky
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Sichen Shao
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK
| | - Matthew L Wohlever
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57(th) Street, Chicago, IL 60637, USA
| | - Ramanujan S Hegde
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
| |
Collapse
|
71
|
On the road to nowhere: cross-talk between post-translational protein targeting and cytosolic quality control. Biochem Soc Trans 2016; 44:796-801. [DOI: 10.1042/bst20160045] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Indexed: 02/06/2023]
Abstract
A well-defined co-translational pathway couples the synthesis and translocation of nascent polypeptides into and across the membrane of the endoplasmic reticulum (ER), thereby minimizing the possibility of the hydrophobic signals and transmembrane domains that such proteins contain from being exposed to the cytosol. Nevertheless, a proportion of these co-translational substrates may fail to reach the ER, and therefore mislocalize to the cytosol where their intrinsic hydrophobicity makes them aggregation-prone. A range of hydrophobic precursor proteins that employ alternative, post-translational, routes for ER translocation also contribute to the cytosolic pool of mislocalized proteins (MLPs). In this review, we detail how mammalian cells can efficiently deal with these MLPs by selectively targeting them for proteasomal degradation. Strikingly, this pathway for MLP degradation is regulated by cytosolic components that also facilitate the TRC40-dependent, post-translational, delivery of tail-anchored membrane proteins (TA proteins) to the ER. Among these components are small glutamine-rich tetratricopeptide repeat-containing protein α (SGTA) and Bcl-2-associated athanogene 6 (BAG6), which appear to play a decisive role in enforcing quality control over hydrophobic precursor proteins that have mislocalized to the cytosol, directing them to either productive membrane insertion or selective ubiquitination and proteasomal degradation.
Collapse
|
72
|
Colombo SF, Cardani S, Maroli A, Vitiello A, Soffientini P, Crespi A, Bram RF, Benfante R, Borgese N. Tail-anchored Protein Insertion in Mammals: FUNCTION AND RECIPROCAL INTERACTIONS OF THE TWO SUBUNITS OF THE TRC40 RECEPTOR. J Biol Chem 2016; 291:15292-306. [PMID: 27226539 DOI: 10.1074/jbc.m115.707752] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Indexed: 11/06/2022] Open
Abstract
The GET (guided entry of tail-anchored proteins)/TRC (transmembrane recognition complex) pathway for tail-anchored protein targeting to the endoplasmic reticulum (ER) has been characterized in detail in yeast and is thought to function similarly in mammals, where the orthologue of the central ATPase, Get3, is known as TRC40 or Asna1. Get3/TRC40 function requires an ER receptor, which in yeast consists of the Get1/Get2 heterotetramer and in mammals of the WRB protein (tryptophan-rich basic protein), homologous to yeast Get1, in combination with CAML (calcium-modulating cyclophilin ligand), which is not homologous to Get2. To better characterize the mammalian receptor, we investigated the role of endogenous WRB and CAML in tail-anchored protein insertion as well as their association, concentration, and stoichiometry in rat liver microsomes and cultured cells. Functional proteoliposomes, reconstituted from a microsomal detergent extract, lost their activity when made with an extract depleted of TRC40-associated proteins or of CAML itself, whereas in vitro synthesized CAML and WRB together were sufficient to confer insertion competence to liposomes. CAML was found to be in ∼5-fold excess over WRB, and alteration of this ratio did not inhibit insertion. Depletion of each subunit affected the levels of the other one; in the case of CAML silencing, this effect was attributable to destabilization of the WRB transcript and not of WRB protein itself. These results reveal unanticipated complexity in the mutual regulation of the TRC40 receptor subunits and raise the question as to the role of the excess CAML in the mammalian ER.
Collapse
Affiliation(s)
- Sara Francesca Colombo
- From the CNR Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano and
| | - Silvia Cardani
- From the CNR Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano and
| | - Annalisa Maroli
- From the CNR Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano and
| | - Adriana Vitiello
- From the CNR Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano and
| | - Paolo Soffientini
- IFOM, the FIRC Institute for Molecular Oncology Foundation, Milan, Italy 20100 and
| | - Arianna Crespi
- From the CNR Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano and
| | | | - Roberta Benfante
- From the CNR Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano and
| | - Nica Borgese
- From the CNR Institute of Neuroscience and BIOMETRA Department, Università degli Studi di Milano and
| |
Collapse
|
73
|
Takeuchi H, Takada A, Kuboniwa M, Amano A. Intracellular periodontal pathogen exploits recycling pathway to exit from infected cells. Cell Microbiol 2016; 18:928-48. [PMID: 26617273 DOI: 10.1111/cmi.12551] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2015] [Revised: 11/09/2015] [Accepted: 11/23/2015] [Indexed: 01/09/2023]
Abstract
Although human gingival epithelium prevents intrusions by periodontal bacteria, Porphyromonas gingivalis, the most well-known periodontal pathogen, is able to invade gingival epithelial cells and pass through the epithelial barrier into deeper tissues. We previously reported that intracellular P. gingivalis exits from gingival epithelial cells via a recycling pathway. However, the underlying molecular process remains unknown. In the present study, we found that the pathogen localized in early endosomes recruits VAMP2 and Rab4A. VAMP2 was found to be specifically localized in early endosomes, although its localization remained unclear in mammalian cells. A single transmembrane domain of VAMP2 was found to be necessary and sufficient for localizing in early endosomes containing P. gingivalis in gingival epithelial cells. VAMP2 forms a complex with EXOC2/Sec5 and EXOC3/Sec6, whereas Rab4A mediates dissociation of the EXOC complex followed by recruitment of RUFY1/Rabip4, Rab4A effector, and Rab14. Depletion of VAMP2 or Rab4A resulted in accumulation of bacteria in early endosomes and disturbed bacterial exit from infected cells. It is suggested that these novel dynamics allow P. gingivalis to exploit fast recycling pathways promoting further bacterial penetration of gingival tissues.
Collapse
Affiliation(s)
- Hiroki Takeuchi
- Department of Preventive Dentistry, Osaka University Graduate School of Dentistry, Suita-Osaka, 565-0871, Japan
| | - Akihiko Takada
- Department of Preventive Dentistry, Osaka University Graduate School of Dentistry, Suita-Osaka, 565-0871, Japan
| | - Masae Kuboniwa
- Department of Preventive Dentistry, Osaka University Graduate School of Dentistry, Suita-Osaka, 565-0871, Japan
| | - Atsuo Amano
- Department of Preventive Dentistry, Osaka University Graduate School of Dentistry, Suita-Osaka, 565-0871, Japan
| |
Collapse
|
74
|
Gristick HB, Rome ME, Chartron JW, Rao M, Hess S, Shan SO, Clemons WM. Mechanism of Assembly of a Substrate Transfer Complex during Tail-anchored Protein Targeting. J Biol Chem 2015; 290:30006-17. [PMID: 26451041 PMCID: PMC4705998 DOI: 10.1074/jbc.m115.677328] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2015] [Revised: 10/02/2015] [Indexed: 11/06/2022] Open
Abstract
Tail-anchored (TA) proteins, defined as having a single transmembrane helix at their C terminus, are post-translationally targeted to the endoplasmic reticulum membrane by the guided entry of TA proteins (GET) pathway. In yeast, the handover of TA substrates is mediated by the heterotetrameric Get4/Get5 complex (Get4/5), which tethers the co-chaperone Sgt2 to the targeting factor, the Get3 ATPase. Binding of Get4/5 to Get3 is critical for efficient TA targeting; however, questions remain about the formation of the Get3·Get4/5 complex. Here we report crystal structures of a Get3·Get4/5 complex from Saccharomyces cerevisiae at 2.8 and 6.0 Å that reveal a novel interface between Get3 and Get4 dominated by electrostatic interactions. Kinetic and mutational analyses strongly suggest that these structures represent an on-pathway intermediate that rapidly assembles and then rearranges to the final Get3·Get4/5 complex. Furthermore, we provide evidence that the Get3·Get4/5 complex is dominated by a single Get4/5 heterotetramer bound to one monomer of a Get3 dimer, uncovering an intriguing asymmetry in the Get4/5 heterotetramer upon Get3 binding. Ultrafast diffusion-limited electrostatically driven Get3·Get4/5 association enables Get4/5 to rapidly sample and capture Get3 at different stages of the GET pathway.
Collapse
Affiliation(s)
| | - Michael E Rome
- From the Division of Chemistry and Chemical Engineering and
| | | | - Meera Rao
- From the Division of Chemistry and Chemical Engineering and
| | - Sonja Hess
- The Proteome Exploration Laboratory, Beckman Institute, California Institute of Technology, Pasadena, California 91125
| | - Shu-ou Shan
- From the Division of Chemistry and Chemical Engineering and
| | | |
Collapse
|
75
|
Camire EJ, Grossman JD, Thole GJ, Fleischman NM, Perlstein DL. The Yeast Nbp35-Cfd1 Cytosolic Iron-Sulfur Cluster Scaffold Is an ATPase. J Biol Chem 2015. [PMID: 26195633 DOI: 10.1074/jbc.m115.667022] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Nbp35 and Cfd1 are prototypical members of the MRP/Nbp35 class of iron-sulfur (FeS) cluster scaffolds that function to assemble nascent FeS clusters for transfer to FeS-requiring enzymes. Both proteins contain a conserved NTPase domain that genetic studies have demonstrated is essential for their cluster assembly activity inside the cell. It was recently reported that these proteins possess no or very low nucleotide hydrolysis activity in vitro, and thus the role of the NTPase domain in cluster biogenesis has remained uncertain. We have reexamined the NTPase activity of Nbp35, Cfd1, and their complex. Using in vitro assays and site-directed mutagenesis, we demonstrate that the Nbp35 homodimer and the Nbp35-Cfd1 heterodimer are ATPases, whereas the Cfd1 homodimer exhibited no or very low ATPase activity. We ruled out the possibility that the observed ATP hydrolysis activity might result from a contaminating ATPase by showing that mutation of key active site residues reduced activity to background levels. Finally, we demonstrate that the fluorescent ATP analog 2'/3'-O-(N'-methylanthraniloyl)-ATP (mantATP) binds stoichiometrically to Nbp35 with a KD = 15.6 μM and that an Nbp35 mutant deficient in ATP hydrolysis activity also displays an increased KD for mantATP. Together, our results demonstrate that the cytosolic iron-sulfur cluster assembly scaffold is an ATPase and pave the way for interrogating the role of nucleotide hydrolysis in cluster biogenesis by this large family of cluster scaffolding proteins found across all domains of life.
Collapse
Affiliation(s)
- Eric J Camire
- From the Department of Chemistry, Boston University, Boston, Massachusetts 02215
| | - John D Grossman
- From the Department of Chemistry, Boston University, Boston, Massachusetts 02215
| | - Grace J Thole
- From the Department of Chemistry, Boston University, Boston, Massachusetts 02215
| | | | - Deborah L Perlstein
- From the Department of Chemistry, Boston University, Boston, Massachusetts 02215
| |
Collapse
|
76
|
Voorhees RM, Hegde RS. Structures of the scanning and engaged states of the mammalian SRP-ribosome complex. eLife 2015; 4. [PMID: 26158507 PMCID: PMC4497383 DOI: 10.7554/elife.07975] [Citation(s) in RCA: 100] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Accepted: 06/07/2015] [Indexed: 12/11/2022] Open
Abstract
The universally conserved signal recognition particle (SRP) is essential for the biogenesis of most integral membrane proteins. SRP scans the nascent chains of translating ribosomes, preferentially engaging those with hydrophobic targeting signals, and delivers these ribosome-nascent chain complexes to the membrane. Here, we present structures of native mammalian SRP-ribosome complexes in the scanning and engaged states. These structures reveal the near-identical SRP architecture of these two states, show many of the SRP-ribosome interactions at atomic resolution, and suggest how the polypeptide-binding M domain selectively engages hydrophobic signals. The scanning M domain, pre-positioned at the ribosomal exit tunnel, is auto-inhibited by a C-terminal amphipathic helix occluding its hydrophobic binding groove. Upon engagement, the hydrophobic targeting signal displaces this amphipathic helix, which then acts as a protective lid over the signal. Biochemical experiments suggest how scanning and engagement are coordinated with translation elongation to minimize exposure of hydrophobic signals during membrane targeting. DOI:http://dx.doi.org/10.7554/eLife.07975.001 Proteins are long chain-like molecules built from smaller building blocks, called amino acids, by a large molecular machine known as a ribosome. Although all proteins are assembled inside cells, some of them must be delivered to the outside or inserted into cell membranes. It is important to understand how this selective delivery system works because secreted proteins (i.e., those delivered outside) and membrane-embedded proteins are essential for cells to communicate with their surroundings. Proteins destined for secretion or membrane insertion contain characteristic stretches of amino acids that act as a targeting signal for delivery to the membrane. These targeting signals are recognized by the ‘signal recognition particle’ (or SRP for short), a large complex found in all living organisms. The SRP has the task of finding ribosomes that are assembling proteins with a targeting signal, and then taking them to the membrane. The protein being assembled can then either cross the membrane for secretion by the cell, or get embedded within the membrane. So, how can the SRP scan the broad range of proteins that are made by the ribosome and engage with only those containing targeting signals? Voorhees and Hegde investigated this question by analyzing SRPs bound to ribosomes that were at different stages of building a membrane protein. The experiment was devised so that SRP would be in two different states: in the first state, the SRP was scanning for its targeting signal and, in the second, it was engaged with the targeting signal. Voorhees and Hegde took many thousands of pictures of these samples using a technique called cryo-electron microscopy, and reconstructed the three-dimensional structures of both states. This revealed fine details of how SRP positions itself immediately next to the part of the ribosome where newly formed protein chains emerge. From here, the SRP scans the protein until the targeting signal emerges and then it engages with the protein. Engaging the targeting signal just as it emerges from the ribosome is probably important because targeting signals tend to aggregate if they are exposed to the contents of a cell. The new structures show how SRP cradles the targeting signal inside a binding groove and covers it with a protective lid to minimize its risk of aggregation. The next challenges are to figure out how SRP chooses which ribosomes to scan, and how it releases the targeting signal when it has delivered it to the membrane. DOI:http://dx.doi.org/10.7554/eLife.07975.002
Collapse
|
77
|
Yamamoto Y, Sakisaka T. The emerging role of calcium-modulating cyclophilin ligand in posttranslational insertion of tail-anchored proteins into the endoplasmic reticulum membrane. J Biochem 2015; 157:419-29. [PMID: 25869254 DOI: 10.1093/jb/mvv035] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Accepted: 02/18/2015] [Indexed: 01/08/2023] Open
Abstract
Tail-anchored (TA) proteins, a class of membrane proteins having an N-terminal cytoplasmic region anchored to the membrane by a single C-terminal transmembrane domain, are posttranslationally inserted into the endoplasmic reticulum (ER) membrane. In yeasts, the posttranslational membrane insertion is mediated by the Guided Entry of TA Proteins (GET) complex. Get3, a cytosolic ATPase, targets newly synthesized TA proteins to the ER membrane, where Get2 and Get3 constitute the Get3 receptor driving the membrane insertion. While mammalian cells employ TRC40 and WRB, mammalian homologs of Get3 and Get1, respectively, they lack the gene homologous to Get2. We recently identified calcium-modulating cyclophilin ligand (CAML) as a TRC40 receptor, indicating that CAML was equivalent to Get2 in the context of the membrane insertion. On the other hand, CAML has been well characterized as a signaling molecule that regulates various biological processes, raising the question of how the two distinct actions of CAML, the membrane insertion and the signal transduction, are assembled. In this review, we summarize recent progress of the molecular mechanism of the membrane insertion of TA proteins and discuss the possibility that CAML could sense the various signals at the ER membrane, thereby controlling TA protein biogenesis.
Collapse
Affiliation(s)
- Yasunori Yamamoto
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| | - Toshiaki Sakisaka
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan
| |
Collapse
|
78
|
Mateja A, Paduch M, Chang HY, Szydlowska A, Kossiakoff AA, Hegde RS, Keenan RJ. Protein targeting. Structure of the Get3 targeting factor in complex with its membrane protein cargo. Science 2015; 347:1152-5. [PMID: 25745174 PMCID: PMC4413028 DOI: 10.1126/science.1261671] [Citation(s) in RCA: 87] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Tail-anchored (TA) proteins are a physiologically important class of membrane proteins targeted to the endoplasmic reticulum by the conserved guided-entry of TA proteins (GET) pathway. During transit, their hydrophobic transmembrane domains (TMDs) are chaperoned by the cytosolic targeting factor Get3, but the molecular nature of the functional Get3-TA protein targeting complex remains unknown. We reconstituted the physiologic assembly pathway for a functional targeting complex and showed that it comprises a TA protein bound to a Get3 homodimer. Crystal structures of Get3 bound to different TA proteins showed an α-helical TMD occupying a hydrophobic groove that spans the Get3 homodimer. Our data elucidate the mechanism of TA protein recognition and shielding by Get3 and suggest general principles of hydrophobic domain chaperoning by cellular targeting factors.
Collapse
Affiliation(s)
- Agnieszka Mateja
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Marcin Paduch
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Hsin-Yang Chang
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Anna Szydlowska
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Anthony A Kossiakoff
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA
| | - Ramanujan S Hegde
- MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge CB2 0QH, UK.
| | - Robert J Keenan
- Department of Biochemistry and Molecular Biology, The University of Chicago, 929 East 57th Street, Chicago, IL 60637, USA.
| |
Collapse
|
79
|
Abstract
In this issue, Voth et al. (2014) reveal that Get3, the GET pathway targeting factor shuttling TA-proteins from the ribosome to the ER membrane, moonlights as a chaperone under oxidizing conditions in a manner reminiscent of bacterial Hsp33.
Collapse
Affiliation(s)
- Hannah Girstmair
- Center of Integrated Protein Science Munich, Department Chemie, Technische Universität München, 85748 Garching, Germany
| | - Johannes Buchner
- Center of Integrated Protein Science Munich, Department Chemie, Technische Universität München, 85748 Garching, Germany.
| |
Collapse
|
80
|
Chen Y, Pieuchot L, Loh RA, Yang J, Kari TMA, Wong JY, Jedd G. Hydrophobic handoff for direct delivery of peroxisome tail-anchored proteins. Nat Commun 2014; 5:5790. [PMID: 25517356 DOI: 10.1038/ncomms6790] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 11/04/2014] [Indexed: 02/06/2023] Open
Abstract
Tail-anchored (TA) proteins are inserted into membranes post-translationally through a C-terminal transmembrane domain (TMD). The PEX19 protein binds peroxisome TA proteins in the cytoplasm and delivers them to the membrane through the PEX3 receptor protein. An amphipathic segment in PEX19 promotes docking on PEX3. However, how this leads to substrate insertion is unknown. Here we reconstitute peroxisome TA protein biogenesis into two sequential steps of substrate TMD engagement and membrane insertion. We identify a series of previously uncharacterized amphipathic segments in PEX19 and identify one whose hydrophobicity is required for membrane insertion, but not TMD chaperone activity or PEX3 binding. A membrane-proximal hydrophobic surface of PEX3 promotes an unconventional form of membrane intercalation, and is also required for TMD insertion. Together, these data support a mechanism in which hydrophobic moieties in the TMD chaperone and its membrane-associated receptor act in a concerted manner to prompt TMD release and membrane insertion.
Collapse
Affiliation(s)
- Yinxiao Chen
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Laurent Pieuchot
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Rachel Ann Loh
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Jing Yang
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Teuku Mahfuzh Aufar Kari
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Jie Yun Wong
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| | - Gregory Jedd
- Temasek Life Sciences Laboratory, Department of Biological Sciences, National University of Singapore, Singapore 117604, Singapore
| |
Collapse
|
81
|
Pillai JK, Venkadesh S, Ajees AA, Rosen BP, Bhattacharjee H. Mutations in the ArsA ATPase that restore interaction with the ArsD metallochaperone. Biometals 2014; 27:1263-75. [PMID: 25183649 PMCID: PMC4224984 DOI: 10.1007/s10534-014-9788-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 08/21/2014] [Indexed: 01/01/2023]
Abstract
The ArsA ATPase is the catalytic subunit of the ArsAB As(III) efflux pump. It receives trivalent As(III) from the intracellular metallochaperone ArsD. The interaction of ArsA and ArsD allows for resistance to As(III) at environmental concentrations. A quadruple mutant in the arsD gene encoding a K2A/K37A/K62A/K104A ArsD is unable to interact with ArsA. An error-prone mutagenesis approach was used to generate random mutations in the arsA gene that restored interaction with the quadruple arsD mutant in yeast two-hybrid assays. A number of arsA genes with multiple mutations were isolated. These were analyzed in more detail by separation into single arsA mutants. Three such mutants encoding Q56R, F120I and D137V ArsA were able to restore interaction with the quadruple ArsD mutant in yeast two-hybrid assays. Each of the three single ArsA mutants also interacted with wild type ArsD. Only the Q56R ArsA derivative exhibited significant metalloid-stimulated ATPase activity in vitro. Purified Q56R ArsA was stimulated by wild type ArsD and to a lesser degree by the quadruple ArsD derivative. The F120I and D137V ArsAs did not show metalloid-stimulated ATPase activity. Structural models generated by in silico docking suggest that an electrostatic interface favors reversible interaction between ArsA and ArsD. We predict that mutations in ArsA propagate changes in hydrogen bonding and salt bridges to the ArsA-ArsD interface that affect their interactions.
Collapse
Affiliation(s)
- Jitesh K. Pillai
- Department of Cellular Biology and Pharmacology, Florida International University, Herbert Wertheim College of Medicine, Miami, Florida 33199, USA
| | - Sarkarai Venkadesh
- Department of Cellular Biology and Pharmacology, Florida International University, Herbert Wertheim College of Medicine, Miami, Florida 33199, USA
| | - A. Abdul Ajees
- Department of Atomic and Molecular Physics, Manipal University, Manipal, Karnataka 576104, India
| | - Barry P. Rosen
- Department of Cellular Biology and Pharmacology, Florida International University, Herbert Wertheim College of Medicine, Miami, Florida 33199, USA
| | - Hiranmoy Bhattacharjee
- Department of Cellular Biology and Pharmacology, Florida International University, Herbert Wertheim College of Medicine, Miami, Florida 33199, USA
| |
Collapse
|
82
|
Differential gradients of interaction affinities drive efficient targeting and recycling in the GET pathway. Proc Natl Acad Sci U S A 2014; 111:E4929-35. [PMID: 25368153 DOI: 10.1073/pnas.1411284111] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Efficient and accurate localization of membrane proteins requires a complex cascade of interactions between protein machineries. This requirement is exemplified in the guided entry of tail-anchored (TA) protein (GET) pathway, where the central targeting factor Get3 must sequentially interact with three distinct binding partners to ensure the delivery of TA proteins to the endoplasmic reticulum (ER) membrane. To understand the molecular principles that provide the vectorial driving force of these interactions, we developed quantitative fluorescence assays to monitor Get3-effector interactions at each stage of targeting. We show that nucleotide and substrate generate differential gradients of interaction energies that drive the ordered interaction of Get3 with successive effectors. These data also provide more molecular details on how the targeting complex is captured and disassembled by the ER receptor and reveal a previously unidentified role for Get4/5 in recycling Get3 from the ER membrane at the end of the targeting reaction. These results provide general insights into how complex protein interaction cascades are coupled to energy inputs in biological systems.
Collapse
|
83
|
The protein targeting factor Get3 functions as ATP-independent chaperone under oxidative stress conditions. Mol Cell 2014; 56:116-27. [PMID: 25242142 DOI: 10.1016/j.molcel.2014.08.017] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 08/01/2014] [Accepted: 08/14/2014] [Indexed: 11/23/2022]
Abstract
Exposure of cells to reactive oxygen species (ROS) causes a rapid and significant drop in intracellular ATP levels. This energy depletion negatively affects ATP-dependent chaperone systems, making ROS-mediated protein unfolding and aggregation a potentially very challenging problem. Here we show that Get3, a protein involved in ATP-dependent targeting of tail-anchored (TA) proteins under nonstress conditions, turns into an effective ATP-independent chaperone when oxidized. Activation of Get3's chaperone function, which is a fully reversible process, involves disulfide bond formation, metal release, and its conversion into distinct, higher oligomeric structures. Mutational studies demonstrate that the chaperone activity of Get3 is functionally distinct from and likely mutually exclusive with its targeting function, and responsible for the oxidative stress-sensitive phenotype that has long been noted for yeast cells lacking functional Get3. These results provide convincing evidence that Get3 functions as a redox-regulated chaperone, effectively protecting eukaryotic cells against oxidative protein damage.
Collapse
|
84
|
Abstract
From the catalytic reactions that sustain the global oxygen, nitrogen, and carbon cycles to the stabilization of DNA processing proteins, transition metal ions and metallocofactors play key roles in biology. Although the exquisite interplay between metal ions and protein scaffolds has been studied extensively, the fact that the biological roles of the metals often stem from their placement in the interfaces between proteins and protein subunits is not always recognized. Interfacial metal ions stabilize permanent or transient protein-protein interactions, enable protein complexes involved in cellular signaling to adopt distinct conformations in response to environmental stimuli, and catalyze challenging chemical reactions that are uniquely performed by multisubunit protein complexes. This review provides a structural survey of transition metal ions and metallocofactors found in protein-protein interfaces, along with a series of selected examples that illustrate their diverse biological utility and significance.
Collapse
Affiliation(s)
- Woon Ju Song
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093; emails: , ,
| | | | | | | |
Collapse
|
85
|
Gristick HB, Rao M, Chartron JW, Rome ME, Shan SO, Clemons WM. Crystal structure of ATP-bound Get3-Get4-Get5 complex reveals regulation of Get3 by Get4. Nat Struct Mol Biol 2014; 21:437-42. [PMID: 24727835 PMCID: PMC4386898 DOI: 10.1038/nsmb.2813] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 03/24/2014] [Indexed: 11/16/2022]
Abstract
Correct localization of membrane proteins is essential to all cells. Chaperone cascades coordinate the capture and handover of substrate proteins from the ribosomes to the target membranes, yet the mechanistic and structural details of these processes remain unclear. Here we investigate the conserved GET pathway, in which the Get4-Get5 complex mediates the handover of tail-anchor (TA) substrates from the cochaperone Sgt2 to the Get3 ATPase, the central targeting factor. We present a crystal structure of a yeast Get3-Get4-Get5 complex in an ATP-bound state and show how Get4 primes Get3 by promoting the optimal configuration for substrate capture. Structure-guided biochemical analyses demonstrate that Get4-mediated regulation of ATP hydrolysis by Get3 is essential to efficient TA-protein targeting. Analogous regulation of other chaperones or targeting factors could provide a general mechanism for ensuring effective substrate capture during protein biogenesis.
Collapse
Affiliation(s)
- Harry B. Gristick
- Division of Chemistry and Chemical Engineering, California Institute of Technology, CA, USA
| | - Meera Rao
- Division of Chemistry and Chemical Engineering, California Institute of Technology, CA, USA
| | - Justin W. Chartron
- Division of Chemistry and Chemical Engineering, California Institute of Technology, CA, USA
| | - Michael E. Rome
- Division of Chemistry and Chemical Engineering, California Institute of Technology, CA, USA
| | - Shu-ou Shan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, CA, USA
| | - William M. Clemons
- Division of Chemistry and Chemical Engineering, California Institute of Technology, CA, USA
| |
Collapse
|
86
|
Affiliation(s)
| | | | - Krzysztof Palczewski
- Department of Pharmacology, School of Medicine, Case
Western Reserve University, 2109 Adelbert Road, Cleveland, Ohio 44106-4965,
United States
| |
Collapse
|
87
|
Arias DG, Marquez VE, Chiribao ML, Gadelha FR, Robello C, Iglesias AA, Guerrero SA. Redox metabolism in Trypanosoma cruzi: functional characterization of tryparedoxins revisited. Free Radic Biol Med 2013; 63:65-77. [PMID: 23665397 DOI: 10.1016/j.freeradbiomed.2013.04.036] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2012] [Revised: 04/04/2013] [Accepted: 04/30/2013] [Indexed: 01/01/2023]
Abstract
Tryparedoxins (TXNs) are multipurpose oxidoreductases from trypanosomatids that transfer reducing equivalents from trypanothione to various thiol proteins. In Trypanosoma cruzi, two genes coding for TXN-like proteins have been identified: TXNI, previously characterized as a cytoplasmic protein, and TXNII, a putative tail-anchored membrane protein. In this work, we performed a comparative functional characterization of T. cruzi TXNs. Particularly, we cloned the gene region coding for the soluble version of TXNII for its heterologous expression. The truncated recombinant protein (without its 22 C-terminal transmembrane amino acids) showed TXN activity. It was also able to transfer reducing equivalents from trypanothione, glutathione, or dihydrolipoamide to various acceptors, including methionine sulfoxide reductases and peroxiredoxins. The results support the occurrence and functionality of a second tryparedoxin, which appears as a new component in the redox scenario for T. cruzi.
Collapse
Affiliation(s)
- Diego G Arias
- Instituto de Agrobiotecnología del Litoral, Facultad de Bioquímica y Ciencias Biológicas, Universidad Nacional del Litoral-CONICET, 3000 Santa Fe, Argentina
| | | | | | | | | | | | | |
Collapse
|
88
|
Tung JY, Li YC, Lin TW, Hsiao CD. Structure of the Sgt2 dimerization domain complexed with the Get5 UBL domain involved in the targeting of tail-anchored membrane proteins to the endoplasmic reticulum. ACTA CRYSTALLOGRAPHICA SECTION D: BIOLOGICAL CRYSTALLOGRAPHY 2013; 69:2081-90. [PMID: 24100326 DOI: 10.1107/s0907444913019379] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Accepted: 07/13/2013] [Indexed: 11/10/2022]
Abstract
The insertion of tail-anchored membrane (TA) proteins into the appropriate membrane is a post-translational event that requires stabilization of the transmembrane domain and targeting to the proper destination. Sgt2, a small glutamine-rich tetratricopeptide-repeat protein, is a heat-shock protein cognate (HSC) co-chaperone that preferentially binds endoplasmic reticulum-destined TA proteins and directs them to the GET pathway via Get4 and Get5. The N-terminal domain of Sgt2 seems to exert dual functions. It mediates Get5 interaction and allows substrate delivery to Get3. Following the N-terminus of Get5 is a ubiquitin-like (Ubl) domain that interacts with the N-terminus of Sgt2. Here, the crystal structure of the Sgt2 dimerization domain complexed with the Get5 Ubl domain (Sgt2N-Get5Ubl) is reported. This complex reveals an intimate interaction between one Sgt2 dimer and one Get5 monomer. This research further demonstrates that hydrophobic residues from both Sgt2 and Get5 play an important role in cell survival under heat stress. This study provides detailed molecular insights into the specific binding of this GET-pathway complex.
Collapse
Affiliation(s)
- Jung-Yu Tung
- Institute of Molecular Biology, Academia Sinica, Taipei 115, Taiwan
| | | | | | | |
Collapse
|
89
|
Denic V, Dötsch V, Sinning I. Endoplasmic reticulum targeting and insertion of tail-anchored membrane proteins by the GET pathway. Cold Spring Harb Perspect Biol 2013; 5:a013334. [PMID: 23906715 PMCID: PMC3721280 DOI: 10.1101/cshperspect.a013334] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Hundreds of eukaryotic membrane proteins are anchored to membranes by a single transmembrane domain at their carboxyl terminus. Many of these tail-anchored (TA) proteins are posttranslationally targeted to the endoplasmic reticulum (ER) membrane for insertion by the guided-entry of TA protein insertion (GET) pathway. In recent years, most of the components of this conserved pathway have been biochemically and structurally characterized. Get3 is the pathway-targeting factor that uses nucleotide-linked conformational changes to mediate the delivery of TA proteins between the GET pretargeting machinery in the cytosol and the transmembrane pathway components in the ER. Here we focus on the mechanism of the yeast GET pathway and make a speculative analogy between its membrane insertion step and the ATPase-driven cycle of ABC transporters.
Collapse
Affiliation(s)
- Vladimir Denic
- Department of Molecular and Cellular Biology, Harvard University, Northwest Laboratories, Cambridge, Massachusetts 02138, USA.
| | | | | |
Collapse
|
90
|
SIMIBI twins in protein targeting and localization. Nat Struct Mol Biol 2013; 20:776-80. [DOI: 10.1038/nsmb.2605] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2013] [Accepted: 05/07/2013] [Indexed: 12/31/2022]
|
91
|
Arai C, Kurahashi H, Pack CG, Sako Y, Nakamura Y. Clearance of yeast eRF-3 prion [ PSI+] by amyloid enlargement due to the imbalance between chaperone Ssa1 and cochaperone Sgt2. TRANSLATION 2013; 1:e26574. [PMID: 26824024 PMCID: PMC4718058 DOI: 10.4161/trla.26574] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 09/12/2013] [Accepted: 09/23/2013] [Indexed: 12/03/2022]
Abstract
The cytoplasmic [PSI+] element of budding yeast represents the prion conformation of translation release factor eRF-3 (Sup35). Prions are transmissible agents caused by self-seeded highly ordered aggregates (amyloids). Much interest lies in understanding how prions are developed and transmitted. However, the cellular mechanism involved in the prion clearance is unknown. Recently we have reported that excess misfolded multi-transmembrane protein, Dip5ΔC-v82, eliminates yeast prion [PSI+]. In this study, we showed that the prion loss was caused by enlargement of prion amyloids, unsuitable for transmission, and its efficiency was affected by the cellular balance between the chaperone Hsp70-Ssa1 and Sgt2, a small cochaperone known as a regulator of chaperone targeting to different types of aggregation-prone proteins. The present findings suggest that Sgt2 is titrated by excess Dip5ΔC-v82, and the shortage of Sgt2 led to non-productive binding of Ssa1 on [PSI+] amyloids. Clearance of prion [PSI+] by the imbalance between Ssa1 and Sgt2 might provide a novel array to regulate the release factor function in yeast.
Collapse
|
92
|
Precise timing of ATPase activation drives targeting of tail-anchored proteins. Proc Natl Acad Sci U S A 2013; 110:7666-71. [PMID: 23610396 DOI: 10.1073/pnas.1222054110] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The localization of tail-anchored (TA) proteins, whose transmembrane domain resides at the extreme C terminus, presents major challenges to cellular protein targeting machineries. In eukaryotic cells, the highly conserved ATPase, guided entry of tail-anchored protein 3 (Get3), coordinates the delivery of TA proteins to the endoplasmic reticulum. How Get3 uses its ATPase cycle to drive this fundamental process remains unclear. Here, we establish a quantitative framework for the Get3 ATPase cycle and show that ATP specifically induces multiple conformational changes in Get3 that culminate in its ATPase activation through tetramerization. Further, upstream and downstream components actively regulate the Get3 ATPase cycle to ensure the precise timing of ATP hydrolysis in the pathway: the Get4/5 TA loading complex locks Get3 in the ATP-bound state and primes it for TA protein capture, whereas the TA substrate induces tetramerization of Get3 and activates its ATPase reaction 100-fold. Our results establish a precise model for how Get3 harnesses the energy from ATP to drive the membrane localization of TA proteins and illustrate how dimerization-activated nucleotide hydrolases regulate diverse cellular processes.
Collapse
|
93
|
Ast T, Schuldiner M. All roads lead to Rome (but some may be harder to travel): SRP-independent translocation into the endoplasmic reticulum. Crit Rev Biochem Mol Biol 2013; 48:273-88. [PMID: 23530742 DOI: 10.3109/10409238.2013.782999] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Translocation into the endoplasmic reticulum (ER) is the first biogenesis step for hundreds of eukaryotic secretome proteins. Over the past 30 years, groundbreaking biochemical, structural and genetic studies have delineated one conserved pathway that enables ER translocation- the signal recognition particle (SRP) pathway. However, it is clear that this is not the only pathway which can mediate ER targeting and insertion. In fact, over the past decade, several SRP-independent pathways have been uncovered, which recognize proteins that cannot engage the SRP and ensure their subsequent translocation into the ER. These SRP-independent pathways face the same challenges that the SRP pathway overcomes: chaperoning the preinserted protein while in the cytosol, targeting it rapidly to the ER surface and generating vectorial movement that inserts the protein into the ER. This review strives to summarize the various mechanisms and machineries which mediate these stages of SRP-independent translocation, as well as examine why SRP-independent translocation is utilized by the cell. This emerging understanding of the various pathways utilized by secretory proteins to insert into the ER draws light to the complexity of the translocational task, and underlines that insertion into the ER might be more varied and tailored than previously appreciated.
Collapse
Affiliation(s)
- Tslil Ast
- Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel.
| | | |
Collapse
|
94
|
Yang HC, Fu HL, Lin YF, Rosen BP. Pathways of arsenic uptake and efflux. CURRENT TOPICS IN MEMBRANES 2013; 69:325-58. [PMID: 23046656 DOI: 10.1016/b978-0-12-394390-3.00012-4] [Citation(s) in RCA: 124] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Arsenic is the most prevalent environmental toxic substance and ranks first on the U.S. Environmental Protection Agency's Superfund List. Arsenic is a carcinogen and a causative agent of numerous human diseases. Paradoxically arsenic is used as a chemotherapeutic agent for treatment of acute promyelocytic leukemia. Inorganic arsenic has two biological important oxidation states: As(V) (arsenate) and As(III) (arsenite). Arsenic uptake is adventitious because the arsenate and arsenite are chemically similar to required nutrients. Arsenate resembles phosphate and is a competitive inhibitor of many phosphate-utilizing enzymes. Arsenate is taken up by phosphate transport systems. In contrast, at physiological pH, the form of arsenite is As(OH)(3), which resembles organic molecules such as glycerol. Consequently, arsenite is taken into cells by aquaglyceroporin channels. Arsenic efflux systems are found in nearly every organism and evolved to rid cells of this toxic metalloid. These efflux systems include members of the multidrug resistance protein family and the bacterial exchangers Acr3 and ArsB. ArsB can also be a subunit of the ArsAB As(III)-translocating ATPase, an ATP-driven efflux pump. The ArsD metallochaperone binds cytosolic As(III) and transfers it to the ArsA subunit of the efflux pump. Knowledge of the pathways and transporters for arsenic uptake and efflux is essential for understanding its toxicity and carcinogenicity and for rational design of cancer chemotherapeutic drugs.
Collapse
Affiliation(s)
- Hung-Chi Yang
- Department of Medical Biotechnology and Laboratory Sciences, Chang-Gung University, Tao-Yuan, Taiwan
| | | | | | | |
Collapse
|
95
|
Lee JG, Ye Y. Bag6/Bat3/Scythe: a novel chaperone activity with diverse regulatory functions in protein biogenesis and degradation. Bioessays 2013; 35:377-85. [PMID: 23417671 DOI: 10.1002/bies.201200159] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Upon emerging from the ribosome exiting tunnel, polypeptide folding occurs immediately with the assistance of both ribosome-associated and free chaperones. While many chaperones known to date are dedicated folding catalysts, recent studies have revealed a novel chaperoning system that functions at the interface of protein biogenesis and quality control by using a special "holdase" activity in order to sort and channel client proteins to distinct destinations. The key component, Bag6/Bat3/Scythe, can effectively shield long hydrophobic segments exposed on the surface of a polypeptide, preventing aggregation or inappropriate interactions before a triaging decision is made. The biological consequences of Bag6-mediated chaperoning are divergent for different substrates, ranging from membrane integration to proteasome targeting and destruction. Accordingly, Bag6 can act in various cellular contexts in order to execute many essential cellular functions, while dysfunctions in the Bag6 system can cause severe cellular abnormalities that may be associated with some pathological conditions.
Collapse
Affiliation(s)
- Jin-Gu Lee
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | | |
Collapse
|
96
|
Rodrigo-Brenni MC, Hegde RS. Design principles of protein biosynthesis-coupled quality control. Dev Cell 2013; 23:896-907. [PMID: 23153486 DOI: 10.1016/j.devcel.2012.10.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The protein biosynthetic machinery, composed of ribosomes, chaperones, and localization factors, is increasingly found to interact directly with factors dedicated to protein degradation. The coupling of these two opposing processes facilitates quality control of nascent polypeptides at each stage of their maturation. Sequential checkpoints maximize the overall fidelity of protein maturation, minimize the exposure of defective products to the bulk cellular environment, and protect organisms from protein misfolding diseases.
Collapse
|
97
|
Post-translational translocation into the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2012; 1833:2403-9. [PMID: 23266354 DOI: 10.1016/j.bbamcr.2012.12.008] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2012] [Revised: 12/06/2012] [Accepted: 12/11/2012] [Indexed: 01/26/2023]
Abstract
Proteins destined for the endomembrane system of eukaryotic cells are typically translocated into or across the membrane of the endoplasmic reticulum and this process is normally closely coupled to protein synthesis. However, it is becoming increasingly apparent that a significant proportion of proteins are targeted to and inserted into the ER membrane post-translationally, that is after their synthesis is complete. These proteins must be efficiently captured and delivered to the target membrane, and indeed a failure to do so may even disrupt proteostasis resulting in cellular dysfunction and disease. In this review, we discuss the mechanisms by which various protein precursors can be targeted to the ER and either inserted into or translocated across the membrane post-translationally. This article is part of a Special Issue entitled: Functional and structural diversity of endoplasmic reticulum.
Collapse
|
98
|
Yamamoto Y, Sakisaka T. Molecular Machinery for Insertion of Tail-Anchored Membrane Proteins into the Endoplasmic Reticulum Membrane in Mammalian Cells. Mol Cell 2012; 48:387-97. [DOI: 10.1016/j.molcel.2012.08.028] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Revised: 07/02/2012] [Accepted: 08/27/2012] [Indexed: 11/27/2022]
|
99
|
Denic V. A portrait of the GET pathway as a surprisingly complicated young man. Trends Biochem Sci 2012; 37:411-7. [PMID: 22951232 DOI: 10.1016/j.tibs.2012.07.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 07/19/2012] [Accepted: 07/20/2012] [Indexed: 01/04/2023]
Abstract
Many eukaryotic membrane proteins have a single C-terminal transmembrane domain that anchors them to a variety of organelles in secretory and endocytic pathways. These tail-anchored (TA) proteins are post-translationally inserted into the endoplasmic reticulum by molecular mechanisms that have long remained mysterious. This review describes how, in just the past 5 years, intense research by a handful of laboratories has led to identification of all the key components of one such mechanism, the guided entry of TA proteins (GET) pathway, which is conserved from yeast to man. The GET pathway is both surprisingly complicated and yet more experimentally tractable than most other membrane insertion mechanisms, and is rapidly revealing new fundamental concepts in membrane protein biogenesis.
Collapse
Affiliation(s)
- Vladimir Denic
- Department of Molecular and Cellular Biology, Harvard University, Northwest Labs, Cambridge, MA 02138, USA.
| |
Collapse
|
100
|
Park KT, Wu W, Lovell S, Lutkenhaus J. Mechanism of the asymmetric activation of the MinD ATPase by MinE. Mol Microbiol 2012; 85:271-81. [PMID: 22651575 DOI: 10.1111/j.1365-2958.2012.08110.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
MinD is a component of the Min system involved in the spatial regulation of cell division. It is an ATPase in the MinD/ParA/Mrp deviant Walker A motif family which is within the P loop GTPase superfamily. Its ATPase activity is stimulated by MinE; however, the mechanism of this activation is unclear. MinD forms a symmetric dimer with two binding sites for MinE; however, a recent model suggested that MinE occupying one site was sufficient for ATP hydrolysis. By generating heterodimers with one binding site for MinE we show that one binding site is sufficient for stimulation of the MinD ATPase. Furthermore, comparison of structures of MinD and related proteins led us to examine the role of N45 in the switch I region. An asparagine at this position is conserved in four of the deviant Walker A motif subfamilies (MinD, chromosomal ParAs, Get3 and FleN) and we find that N45 in MinD is essential for MinE-stimulated ATPase activity and suggest that it is a key residue affected by MinE binding.
Collapse
Affiliation(s)
- Kyung-Tae Park
- Department of Microbiology, Molecular Genetics and Immunology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | | | | | | |
Collapse
|