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Kunishige R, Murata M, Kano F. Targeted protein degradation by Trim-Away using cell resealing coupled with microscopic image-based quantitative analysis. Front Cell Dev Biol 2022; 10:1027043. [PMID: 36601537 PMCID: PMC9806799 DOI: 10.3389/fcell.2022.1027043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 11/28/2022] [Indexed: 12/23/2022] Open
Abstract
"Trim-Away" technology enables rapid degradation of endogenous proteins without prior modification of protein-coding genes or mRNAs through delivery of antibodies that target proteins of interest. Although this approach can be readily applied to almost any cytosolic protein, strategies for cytosolic antibody delivery have been limited to microinjection or electroporation, which require skill-dependent operation or specialized equipment. Thus, the development of antibody delivery methods that are convenient, scalable, and preferably do not require detachment of adherent cells is required to extend the versatility of the Trim-Away method. Here, we developed a cell resealing technique optimized for Trim-Away degradation, which uses the pore-forming toxin streptolysin O (SLO) to permeabilize the cell membrane and delivered the antibodies of interest into HEK293T, HeLa, and HK-2 cell lines. We demonstrated the ability of Trim-Away protein degradation using IKKα and mTOR as targets, and we showed the availability of the developed system in antibody screening for the Trim-Away method. Furthermore, we effectively coupled Trim-Away with cyclic immunofluorescence and microscopic image-based analysis, which enables single-cell multiplexed imaging analysis. Taking advantage of this new analysis strategy, we were able to compensate for low signal-to-noise due to cell-to-cell variation, which occurs in the Trim-Away method because of the heterogenous contents of the introduced antibody, target protein, and TRIM21 in individual cells. Therefore, the reported cell resealing technique coupled with microscopic image analysis enables Trim-Away users to elucidate target protein function and the effects of target protein degradation on various cellular functions in a more quantitative and precise manner.
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Affiliation(s)
- Rina Kunishige
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan,Multimodal Cell Analysis Collaborative Research Cluster, Tokyo Institute of Technology, Yokohama, Japan
| | - Masayuki Murata
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan,Multimodal Cell Analysis Collaborative Research Cluster, Tokyo Institute of Technology, Yokohama, Japan,International Research Center for Neurointelligence, Institutes for Advanced Study, The University of Tokyo, Tokyo, Japan
| | - Fumi Kano
- Cell Biology Center, Institute of Innovative Research, Tokyo Institute of Technology, Yokohama, Japan,Multimodal Cell Analysis Collaborative Research Cluster, Tokyo Institute of Technology, Yokohama, Japan,*Correspondence: Fumi Kano,
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2
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Possible roles of AMPK and macropinocytosis in the defense responses against Δ 9-THC toxicity on HL-1 cardiomyocytes. Toxicol Rep 2021; 8:980-987. [PMID: 34026562 PMCID: PMC8131391 DOI: 10.1016/j.toxrep.2021.04.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2021] [Revised: 04/19/2021] [Accepted: 04/27/2021] [Indexed: 12/17/2022] Open
Abstract
Cannabinoids are some of the most popular recreationally used illicit drugs, and are frequently consumed along with alcoholic beverages. Although the whole body effects of cannabinoids depend largely on their effects on the central nerve system, cannabinoids could harm the heart directly, due to the presence of the endocannabinoid system including cannabinoid receptor1 and 2 (CB-R1 and CB-R2) in the heart. The aim of this study is to examine the mechanism of direct cardiotoxicity of Δ9-tetrahydrocannabinol (Δ9-THC), the main psychoactive ingredient of cannabis. For this purpose, HL-1 murine atrial cardiac muscle cells were treated with 10 or 30 μM Δ9-THC, along with 100 mM ethanol to examine the possible synergistic effects of Δ9-THC and ethanol. Transcriptome analysis showed upregulation of the genes involved in the unfolded protein response (UPR), including Bip, CHOP, ATF4 and ATF6, in cells treated with Δ9-THC. Immunoblot analysis showed caspase3 activation, indicating apoptosis caused by ER stress in Δ9-THC-treated cells. Microscopic analysis showed that Δ9-THC enhances macropinocytosis, a process involved in the uptake of extracellular fluids including nutrients. Moreover Δ9-THC seemed to activate AMPK, a sensor of intracellular energy status and an activator of macropinocytosis. Finally, we found that compound C (AMPK inhibitor) aggravated cell death by Δ9-THC while AICAR (AMPK activator) ameliorated it. Collectively, these results indicate that the activation of AMPK is necessary for the survival of HL-1 cells against Δ9-THC toxicity. Macropinocytosis might serve as one of the survival pathways downstream of AMPK.
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3
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Kumar D, Lak B, Suntio T, Vihinen H, Belevich I, Viita T, Xiaonan L, Vartiainen A, Vartiainen M, Varjosalo M, Jokitalo E. RTN4B interacting protein FAM134C promotes ER membrane curvature and has a functional role in autophagy. Mol Biol Cell 2021; 32:1158-1170. [PMID: 33826365 PMCID: PMC8351555 DOI: 10.1091/mbc.e20-06-0409] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The endoplasmic reticulum (ER) is composed of a controlled ratio of sheets and tubules, which are maintained by several proteins with multiple functions. Reticulons (RTNs), especially RTN4, and DP1/Yop1p family members are known to induce ER membrane curvature. RTN4B is the main RTN4 isoform expressed in nonneuronal cells. In this study, we identified FAM134C as a RTN4B interacting protein in mammalian, nonneuronal cells. FAM134C localized specifically to the ER tubules and sheet edges. Ultrastructural analysis revealed that overexpression of FAM134C induced the formation of unbranched, long tubules or dense globular structures composed of heavily branched narrow tubules. In both cases, tubules were nonmotile. ER tubulation was dependent on the reticulon homology domain (RHD) close to the N-terminus. FAM134C plays a role in the autophagy pathway as its level elevated significantly upon amino acid starvation but not during ER stress. Moreover, FAM134C depletion reduced the number and size of autophagic structures and the amount of ER as a cargo within autophagic structures under starvation conditions. Dominant-negative expression of FAM134C forms with mutated RHD or LC3 interacting region also led to a reduced number of autophagic structures. Our results suggest that FAM134C provides a link between regulation of ER architecture and ER turnover by promoting ER tubulation required for subsequent ER fragmentation and engulfment into autophagosomes.
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Affiliation(s)
| | - Behnam Lak
- Cell and Tissue Dynamics Research Program
| | | | - Helena Vihinen
- Cell and Tissue Dynamics Research Program.,Electron Microscopy Unit, and
| | - Ilya Belevich
- Cell and Tissue Dynamics Research Program.,Electron Microscopy Unit, and
| | | | - Liu Xiaonan
- Molecular Systems Biology Research Group and Proteomics Unit, Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, 00014 Helsinki, Finland
| | | | | | - Markku Varjosalo
- Molecular Systems Biology Research Group and Proteomics Unit, Institute of Biotechnology, Helsinki Institute of Life Science, University of Helsinki, 00014 Helsinki, Finland
| | - Eija Jokitalo
- Cell and Tissue Dynamics Research Program.,Electron Microscopy Unit, and
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4
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Signal Peptide Peptidase-Type Proteases: Versatile Regulators with Functions Ranging from Limited Proteolysis to Protein Degradation. J Mol Biol 2020; 432:5063-5078. [DOI: 10.1016/j.jmb.2020.05.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 05/02/2020] [Accepted: 05/19/2020] [Indexed: 12/15/2022]
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5
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Kunishige R, Kano F, Murata M. The cell resealing technique for manipulating, visualizing, and elucidating molecular functions in living cells. Biochim Biophys Acta Gen Subj 2020; 1864:129329. [DOI: 10.1016/j.bbagen.2019.03.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2018] [Revised: 03/05/2019] [Accepted: 03/20/2019] [Indexed: 12/19/2022]
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6
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Abstract
The Golgi apparatus is a central intracellular membrane-bound organelle with key functions in trafficking, processing, and sorting of newly synthesized membrane and secretory proteins and lipids. To best perform these functions, Golgi membranes form a unique stacked structure. The Golgi structure is dynamic but tightly regulated; it undergoes rapid disassembly and reassembly during the cell cycle of mammalian cells and is disrupted under certain stress and pathological conditions. In the past decade, significant amount of effort has been made to reveal the molecular mechanisms that regulate the Golgi membrane architecture and function. Here we review the major discoveries in the mechanisms of Golgi structure formation, regulation, and alteration in relation to its functions in physiological and pathological conditions to further our understanding of Golgi structure and function in health and diseases.
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Affiliation(s)
- Jie Li
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Erpan Ahat
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
| | - Yanzhuang Wang
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
- Department of Neurology, University of Michigan School of Medicine, Ann Arbor, MI, USA.
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7
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Avci D, Malchus NS, Heidasch R, Lorenz H, Richter K, Neßling M, Lemberg MK. The intramembrane protease SPP impacts morphology of the endoplasmic reticulum by triggering degradation of morphogenic proteins. J Biol Chem 2018; 294:2786-2800. [PMID: 30578301 DOI: 10.1074/jbc.ra118.005642] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 12/12/2018] [Indexed: 11/06/2022] Open
Abstract
The endoplasmic reticulum (ER), as a multifunctional organelle, plays crucial roles in lipid biosynthesis and calcium homeostasis as well as the synthesis and folding of secretory and membrane proteins. Therefore, it is of high importance to maintain ER homeostasis and to adapt ER function and morphology to cellular needs. Here, we show that signal peptide peptidase (SPP) modulates the ER shape through degradation of morphogenic proteins. Elevating SPP activity induces rapid rearrangement of the ER and formation of dynamic ER clusters. Inhibition of SPP activity rescues the phenotype without the need for new protein synthesis, and this rescue depends on a pre-existing pool of proteins in the Golgi. With the help of organelle proteomics, we identified certain membrane proteins to be diminished upon SPP expression and further show that the observed morphology changes depend on SPP-mediated cleavage of ER morphogenic proteins, including the SNARE protein syntaxin-18. Thus, we suggest that SPP-mediated protein abundance control by a regulatory branch of ER-associated degradation (ERAD-R) has a role in shaping the early secretory pathway.
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Affiliation(s)
- Dönem Avci
- From the Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany and
| | - Nicole S Malchus
- From the Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany and
| | - Ronny Heidasch
- From the Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany and
| | - Holger Lorenz
- From the Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany and
| | - Karsten Richter
- German Cancer Research Center (DKFZ), Central Unit Electron Microscopy, 69120 Heidelberg, Germany
| | - Michelle Neßling
- German Cancer Research Center (DKFZ), Central Unit Electron Microscopy, 69120 Heidelberg, Germany
| | - Marius K Lemberg
- From the Centre for Molecular Biology of Heidelberg University (ZMBH), DKFZ-ZMBH Alliance, 69120 Heidelberg, Germany and
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8
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Insight into Notch Signaling Steps That Involve pecanex from Dominant-Modifier Screens in Drosophila. Genetics 2018; 209:1099-1119. [PMID: 29853475 DOI: 10.1534/genetics.118.300935] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Accepted: 05/22/2018] [Indexed: 12/14/2022] Open
Abstract
Notch signaling plays crucial roles in intercellular communications. In Drosophila, the pecanex (pcx) gene, which encodes an evolutionarily conserved multi-pass transmembrane protein, appears to be required to activate Notch signaling in some contexts, especially during neuroblast segregation in the neuroectoderm. Although Pcx has been suggested to contribute to endoplasmic reticulum homeostasis, its functions remain unknown. Here, to elucidate these roles, we performed genetic modifier screens of pcx We found that pcx heterozygotes lacking its maternal contribution exhibit cold-sensitive lethality, which is attributed to a reduction in Notch signaling at decreased temperatures. Using sets of deletions that uncover most of the second and third chromosomes, we identified four enhancers and two suppressors of the pcx cold-sensitive lethality. Among these, five genes encode known Notch-signaling components: big brain, Delta (Dl), neuralized (neur), Brother of Bearded A (BobA), a member of the Bearded (Brd) family, and N-ethylmaleimide-sensitive factor 2 (Nsf2). We showed that BobA suppresses Dl endocytosis during neuroblast segregation in the neuroectoderm, as Brd family genes reportedly do in the mesoderm for mesectoderm specification. Analyses of Nsf2, a key regulator of vesicular fusion, suggested a novel role in neuroblast segregation, which is distinct from Nsf2's previously reported role in imaginal tissues. Finally, jim lovell, which encodes a potential transcription factor, may play a role in Notch signaling during neuroblast segregation. These results reveal new research avenues for Pcx functions and Notch signaling.
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9
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Yi L, Kaler SG. Interaction between the AAA ATPase p97/VCP and a concealed UBX domain in the copper transporter ATP7A is associated with motor neuron degeneration. J Biol Chem 2018; 293:7606-7617. [PMID: 29599289 DOI: 10.1074/jbc.ra117.000686] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2017] [Revised: 03/09/2018] [Indexed: 11/06/2022] Open
Abstract
The copper-transporting ATPase ATP7A contains eight transmembrane domains and is required for normal human copper homeostasis. Mutations in the ATP7A gene may lead to infantile-onset cerebral degeneration (Menkes disease); occipital horn syndrome (OHS), a related but much milder illness; or an adult-onset isolated distal motor neuropathy. The ATP7A missense mutation T994I is located in the sixth transmembrane domain of ATP7A, represents one of the variants associated with the latter phenotype, and is associated with an abnormal interaction with p97/valosin-containing protein (VCP), a hexameric AAA ATPase (ATPase associated with diverse cellular activities) with multiple biological functions. In this study, we further characterized this interaction and discovered a concealed UBX domain in the third lumenal loop of ATP7A, between its fifth and sixth transmembrane domains. We show that the T994I substitution results in conformational exposure of the UBX domain, which then binds the N-terminal domain of p97/VCP. We also show that this abnormal interaction occurs at or near the cell plasma membrane. The UBX domain has a conserved hydrophobic FP (Phe-Pro) motif, and substitution with di-alanine abrogated the interaction and restored the proper intracellular localization of ATP7A in the trans-Golgi network. Using protein MS, we identified potential coordinating components of the ATP7AT994I-p97 complex, including NSFL1 cofactor (NSF1C or p47) that may be relevant to the pathophysiology and clinical effects associated with ATP7AT994I Our study represents the first report of p97/VCP binding to a UBX domain that is not normally exposed, resulting in an aberrant protein-protein interaction leading to motor neuron degeneration.
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Affiliation(s)
- Ling Yi
- From the Section on Translational Neuroscience, Molecular Medicine Branch, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892-3754
| | - Stephen G Kaler
- From the Section on Translational Neuroscience, Molecular Medicine Branch, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892-3754
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10
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Establishment and phenotyping of disease model cells created by cell-resealing technique. Sci Rep 2017; 7:15167. [PMID: 29123170 PMCID: PMC5680332 DOI: 10.1038/s41598-017-15443-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Accepted: 10/23/2017] [Indexed: 12/28/2022] Open
Abstract
Cell-based assays are growing in importance for screening drugs and investigating their mechanisms of action. Most of the assays use so-called “normal” cell strain because it is difficult to produce cell lines in which the disease conditions are reproduced. In this study, we used a cell-resealing technique, which reversibly permeabilizes the plasma membrane, to develop diabetic (Db) model hepatocytes into which cytosol from diabetic mouse liver had been introduced. Db model hepatocytes showed several disease-specific phenotypes, namely disturbance of insulin-induced repression of gluconeogenic gene expression and glucose secretion. Quantitative image analysis and principal component analysis revealed that the ratio of phosphorylated Akt (pAkt) to Akt was the best index to describe the difference between wild-type and Db model hepatocytes. By performing image-based drug screening, we found pioglitazone, a PPARγ agonist, increased the pAkt/Akt ratio, which in turn ameliorated the insulin-induced transcriptional repression of the gluconeogenic gene phosphoenolpyruvate carboxykinase 1. The disease-specific model cells coupled with image-based quantitative analysis should be useful for drug development, enabling the reconstitution of disease conditions at the cellular level and the discovery of disease-specific markers.
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11
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Sorafenib Impedes Rift Valley Fever Virus Egress by Inhibiting Valosin-Containing Protein Function in the Cellular Secretory Pathway. J Virol 2017; 91:JVI.00968-17. [PMID: 28794043 DOI: 10.1128/jvi.00968-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2017] [Accepted: 08/04/2017] [Indexed: 12/20/2022] Open
Abstract
There is an urgent need for therapeutic development to combat infections caused by Rift Valley fever virus (RVFV), which causes devastating disease in both humans and animals. In an effort to repurpose drugs for RVFV treatment, our previous studies screened a library of FDA-approved drugs. The most promising candidate identified was the hepatocellular and renal cell carcinoma drug sorafenib. Mechanism-of-action studies indicated that sorafenib targeted a late stage in virus infection and caused a buildup of virions within cells. In addition, small interfering RNA (siRNA) knockdown studies suggested that nonclassical targets of sorafenib are important for the propagation of RVFV. Here we extend our previous findings to identify the mechanism by which sorafenib inhibits the release of RVFV virions from the cell. Confocal microscopy imaging revealed that glycoprotein Gn colocalizes and accumulates within the endoplasmic reticulum (ER) and the transport of Gn from the Golgi complex to the host cell membrane is reduced. Transmission electron microscopy demonstrated that sorafenib caused virions to be present inside large vacuoles inside the cells. p97/valosin-containing protein (VCP), which is involved in membrane remodeling in the secretory pathway and a known target of sorafenib, was found to be important for RVFV egress. Knockdown of VCP resulted in decreased RVFV replication, reduced Gn Golgi complex localization, and increased Gn ER accumulation. The intracellular accumulation of RVFV virions was also observed in cells transfected with siRNA targeting VCP. Collectively, these data indicate that sorafenib causes a disruption in viral egress by targeting VCP and the secretory pathway, resulting in a buildup of virions within dilated ER vesicles.IMPORTANCE In humans, symptoms of RVFV infection mainly include a self-limiting febrile illness. However, in some cases, infected individuals can also experience hemorrhagic fever, neurological disorders, liver failure, and blindness, which could collectively be lethal. The ability of RVFV to expand geographically outside sub-Saharan Africa is of concern, particularly to the Americas, where native mosquito species are capable of virus transmission. Currently, there are no FDA-approved therapeutics to treat RVFV infection, and thus, there is an urgent need to understand the mechanisms by which the virus hijacks the host cell machinery to replicate. The significance of our research is in identifying the cellular target of sorafenib that inhibits RVFV propagation, so that this information can be used as a tool for the further development of therapeutics used to treat RVFV infection.
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12
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Ye Y, Tang WK, Zhang T, Xia D. A Mighty "Protein Extractor" of the Cell: Structure and Function of the p97/CDC48 ATPase. Front Mol Biosci 2017; 4:39. [PMID: 28660197 PMCID: PMC5468458 DOI: 10.3389/fmolb.2017.00039] [Citation(s) in RCA: 129] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 05/22/2017] [Indexed: 12/13/2022] Open
Abstract
p97/VCP (known as Cdc48 in S. cerevisiae or TER94 in Drosophila) is one of the most abundant cytosolic ATPases. It is highly conserved from archaebacteria to eukaryotes. In conjunction with a large number of cofactors and adaptors, it couples ATP hydrolysis to segregation of polypeptides from immobile cellular structures such as protein assemblies, membranes, ribosome, and chromatin. This often results in proteasomal degradation of extracted polypeptides. Given the diversity of p97 substrates, this "segregase" activity has profound influence on cellular physiology ranging from protein homeostasis to DNA lesion sensing, and mutations in p97 have been linked to several human diseases. Here we summarize our current understanding of the structure and function of this important cellular machinery and discuss the relevant clinical implications.
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Affiliation(s)
- Yihong Ye
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesda, MD, United States
| | - Wai Kwan Tang
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of HealthBethesda, MD, United States
| | - Ting Zhang
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of HealthBethesda, MD, United States
| | - Di Xia
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of HealthBethesda, MD, United States
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13
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Deubiquitinating enzyme VCIP135 dictates the duration of botulinum neurotoxin type A intoxication. Proc Natl Acad Sci U S A 2017; 114:E5158-E5166. [PMID: 28584101 DOI: 10.1073/pnas.1621076114] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Botulism is characterized by flaccid paralysis, which can be caused by intoxication with any of the seven known serotypes of botulinum neurotoxin (BoNT), all of which disrupt synaptic transmission by endoproteolytic cleavage of SNARE proteins. BoNT serotype A (BoNT/A) has the most prolonged or persistent effects, which can last several months, and exerts its effects by specifically cleaving and inactivating SNAP25. A major factor contributing to the persistence of intoxication is the long half-life of the catalytic light chain, which remains enzymatically active months after entry into cells. Here we report that BoNT/A catalytic light chain binds to, and is a substrate for, the ubiquitin ligase HECTD2. However, the light chain evades proteasomal degradation by the dominant effect of a deubiquitinating enzyme, VCIP135/VCPIP1. This deubiquitinating enzyme binds BoNT/A light chain directly, with the two associating in cells through the C-terminal 77 amino acids of the light chain protease. The development of specific DUB inhibitors, together with inhibitors of BoNT/A proteolytic activity, may be useful for reducing the morbidity and public health costs associated with BoNT/A intoxication and could have potential biodefense implications.
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14
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Salo VT, Belevich I, Li S, Karhinen L, Vihinen H, Vigouroux C, Magré J, Thiele C, Hölttä-Vuori M, Jokitalo E, Ikonen E. Seipin regulates ER-lipid droplet contacts and cargo delivery. EMBO J 2016; 35:2699-2716. [PMID: 27879284 PMCID: PMC5167346 DOI: 10.15252/embj.201695170] [Citation(s) in RCA: 210] [Impact Index Per Article: 26.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2016] [Revised: 10/22/2016] [Accepted: 10/24/2016] [Indexed: 11/10/2022] Open
Abstract
Seipin is an endoplasmic reticulum (ER) membrane protein implicated in lipid droplet (LD) biogenesis and mutated in severe congenital lipodystrophy (BSCL2). Here, we show that seipin is stably associated with nascent ER–LD contacts in human cells, typically via one mobile focal point per LD. Seipin appears critical for such contacts since ER–LD contacts were completely missing or morphologically aberrant in seipin knockout and BSCL2 patient cells. In parallel, LD mobility was increased and protein delivery from the ER to LDs to promote LD growth was decreased. Moreover, while growing LDs normally acquire lipid and protein constituents from the ER, this process was compromised in seipin‐deficient cells. In the absence of seipin, the initial synthesis of neutral lipids from exogenous fatty acid was normal, but fatty acid incorporation into neutral lipids in cells with pre‐existing LDs was impaired. Together, our data suggest that seipin helps to connect newly formed LDs to the ER and that by stabilizing ER–LD contacts seipin facilitates the incorporation of protein and lipid cargo into growing LDs in human cells.
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Affiliation(s)
- Veijo T Salo
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Ilya Belevich
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Shiqian Li
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Leena Karhinen
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Helena Vihinen
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Corinne Vigouroux
- Sorbonne Universités, UPMC Univ Paris 6, Inserm UMR_S938, Saint-Antoine Research Center, Institute of Cardiometabolism And Nutrition, AP-HP, Saint-Antoine Hospital Department of Molecular Biology and Genetics, Paris, France
| | - Jocelyne Magré
- l'Institut du Thorax, INSERM CNRS UNIV Nantes, Nantes, France
| | | | - Maarit Hölttä-Vuori
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland.,Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | - Eija Jokitalo
- Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Elina Ikonen
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland .,Minerva Foundation Institute for Medical Research, Helsinki, Finland
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15
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Rämö O, Kumar D, Gucciardo E, Joensuu M, Saarekas M, Vihinen H, Belevich I, Smolander OP, Qian K, Auvinen P, Jokitalo E. NOGO-A/RTN4A and NOGO-B/RTN4B are simultaneously expressed in epithelial, fibroblast and neuronal cells and maintain ER morphology. Sci Rep 2016; 6:35969. [PMID: 27786289 PMCID: PMC5081510 DOI: 10.1038/srep35969] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Accepted: 10/07/2016] [Indexed: 02/08/2023] Open
Abstract
Reticulons (RTNs) are a large family of membrane associated proteins with various functions. NOGO-A/RTN4A has a well-known function in limiting neurite outgrowth and restricting the plasticity of the mammalian central nervous system. On the other hand, Reticulon 4 proteins were shown to be involved in forming and maintaining endoplasmic reticulum (ER) tubules. Using comparative transcriptome analysis and qPCR, we show here that NOGO-B/RTN4B and NOGO-A/RTN4A are simultaneously expressed in cultured epithelial, fibroblast and neuronal cells. Electron tomography combined with immunolabelling reveal that both isoforms localize preferably to curved membranes on ER tubules and sheet edges. Morphological analysis of cells with manipulated levels of NOGO-B/RTN4B revealed that it is required for maintenance of normal ER shape; over-expression changes the sheet/tubule balance strongly towards tubules and causes the deformation of the cell shape while depletion of the protein induces formation of large peripheral ER sheets.
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Affiliation(s)
- Olli Rämö
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Darshan Kumar
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Erika Gucciardo
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Merja Joensuu
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Maiju Saarekas
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Helena Vihinen
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Ilya Belevich
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Olli-Pekka Smolander
- DNA Sequencing and Genomics Laboratory, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Kui Qian
- DNA Sequencing and Genomics Laboratory, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Petri Auvinen
- DNA Sequencing and Genomics Laboratory, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Cell and Molecular Biology Program, Institute of Biotechnology, University of Helsinki, Helsinki, Finland.,Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, Helsinki, Finland
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16
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VCP and ATL1 regulate endoplasmic reticulum and protein synthesis for dendritic spine formation. Nat Commun 2016; 7:11020. [PMID: 26984393 PMCID: PMC4800434 DOI: 10.1038/ncomms11020] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Accepted: 02/12/2016] [Indexed: 12/29/2022] Open
Abstract
Imbalanced protein homeostasis, such as excessive protein synthesis and protein aggregation, is a pathogenic hallmark of a range of neurological disorders. Here, using expression of mutant proteins, a knockdown approach and disease mutation knockin mice, we show that VCP (valosin-containing protein), together with its cofactor P47 and the endoplasmic reticulum (ER) morphology regulator ATL1 (Atlastin-1), regulates tubular ER formation and influences the efficiency of protein synthesis to control dendritic spine formation in neurons. Strengthening the significance of protein synthesis in dendritic spinogenesis, the translation blocker cyclohexamide and the mTOR inhibitor rapamycin reduce dendritic spine density, while a leucine supplement that increases protein synthesis ameliorates the dendritic spine defects caused by Vcp and Atl1 deficiencies. Because VCP and ATL1 are the causative genes of several neurodegenerative and neurodevelopmental disorders, we suggest that impaired ER formation and inefficient protein synthesis are significant in the pathogenesis of multiple neurological disorders. Protein homeostasis is crucial for maintaining a variety of cellular functions. Here the authors show that valosin-containing protein and its cofactors regulate tubular ER formation and protein synthesis efficiency, thereby control dendritic spine formation in neurons.
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17
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Joensuu M, Belevich I, Rämö O, Nevzorov I, Vihinen H, Puhka M, Witkos TM, Lowe M, Vartiainen MK, Jokitalo E. ER sheet persistence is coupled to myosin 1c-regulated dynamic actin filament arrays. Mol Biol Cell 2014; 25:1111-26. [PMID: 24523293 PMCID: PMC3967974 DOI: 10.1091/mbc.e13-12-0712] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2013] [Revised: 01/17/2014] [Accepted: 01/28/2014] [Indexed: 11/11/2022] Open
Abstract
The endoplasmic reticulum (ER) comprises a dynamic three-dimensional (3D) network with diverse structural and functional domains. Proper ER operation requires an intricate balance within and between dynamics, morphology, and functions, but how these processes are coupled in cells has been unclear. Using live-cell imaging and 3D electron microscopy, we identify a specific subset of actin filaments localizing to polygons defined by ER sheets and tubules and describe a role for these actin arrays in ER sheet persistence and, thereby, in maintenance of the characteristic network architecture by showing that actin depolymerization leads to increased sheet fluctuation and transformations and results in small and less abundant sheet remnants and a defective ER network distribution. Furthermore, we identify myosin 1c localizing to the ER-associated actin filament arrays and reveal a novel role for myosin 1c in regulating these actin structures, as myosin 1c manipulations lead to loss of the actin filaments and to similar ER phenotype as observed after actin depolymerization. We propose that ER-associated actin filaments have a role in ER sheet persistence regulation and thus support the maintenance of sheets as a stationary subdomain of the dynamic ER network.
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Affiliation(s)
- Merja Joensuu
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Ilya Belevich
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
- Electron Microscopy Unit, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Olli Rämö
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Ilya Nevzorov
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Helena Vihinen
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
- Electron Microscopy Unit, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Maija Puhka
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Tomasz M. Witkos
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Martin Lowe
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PL, United Kingdom
| | - Maria K. Vartiainen
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
| | - Eija Jokitalo
- Cell and Molecular Biology Program, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
- Electron Microscopy Unit, Institute of Biotechnology, 00014 University of Helsinki, Helsinki, Finland
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18
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O'Sullivan NC, Dräger N, O'Kane CJ. Characterization of the Drosophila atlastin interactome reveals VCP as a functionally related interactor. J Genet Genomics 2013; 40:297-306. [PMID: 23790629 DOI: 10.1016/j.jgg.2013.04.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/29/2013] [Accepted: 04/30/2013] [Indexed: 01/19/2023]
Abstract
At least 25 genes, many involved in trafficking, localisation or shaping of membrane organelles, have been identified as causative genes for the neurodegenerative disorder hereditary spastic paraplegia (HSP). One of the most commonly mutated HSP genes, atlastin-1, encodes a dynamin-like GTPase that mediates homotypic fusion of endoplasmic reticulum (ER) membranes. However, the molecular mechanisms of atlastin-1-related membrane fusion and axonopathy remain unclear. To better understand its mode of action, we used affinity purification coupled with mass spectrometry to identify protein interactors of atlastin in Drosophila. Analysis of 72 identified proteins revealed that the atlastin interactome contains many proteins involved in protein processing and transport, in addition to proteins with roles in mRNA binding, metabolism and mitochondrial proteins. The highest confidence interactor from mass spectrometry analysis, the ubiquitin-selective AAA-ATPase valosin-containing protein (VCP), was validated as an atlastin-interacting protein, and VCP and atlastin showed overlapping subcellular distributions. Furthermore, VCP acted as a genetic modifier of atlastin: loss of VCP partially suppressed an eye phenotype caused by atlastin overexpression, whereas overexpression of VCP enhanced this phenotype. These interactions between atlastin and VCP suggest a functional relationship between these two proteins, and point to potential shared mechanisms between HSP and other forms of neurodegeneration.
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Affiliation(s)
- Niamh C O'Sullivan
- Department of Genetics, University of Cambridge, Downing Street, Cambridge CB2 3EH, United Kingdom.
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19
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Kano F, Nakatsu D, Noguchi Y, Yamamoto A, Murata M. A resealed-cell system for analyzing pathogenic intracellular events: perturbation of endocytic pathways under diabetic conditions. PLoS One 2012; 7:e44127. [PMID: 22952896 PMCID: PMC3430665 DOI: 10.1371/journal.pone.0044127] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Accepted: 07/30/2012] [Indexed: 12/25/2022] Open
Abstract
Cell-based assay systems that can serve as cellular models of aberrant function in pathogenic organs would be novel and useful tools for screening drugs and clarifying the molecular mechanisms of various diseases. We constructed model cells that replicated the conditions in diabetic hepatocytes by using the cell resealing technique, which enables the exchange of cytosol. The plasma membrane of HeLa cells was permeabilized with the streptococcal toxin streptolysin O, and cytosol that had been prepared from wild-type or db/db diabetic mice was introduced into the resulting semi-intact cells. By resealing the plasma membrane by exposure to Ca2+, we created WT or Db model cells, in which the cytosolic conditions replicated those of healthy or diabetic liver. Interestingly, phosphorylation of p38 MAPK was promoted, whereas the level of endosomal phosphatidylinositol-3-phosphate was decreased, in Db cells. We investigated several endocytic pathways in WT and Db cells, and found that retrograde endosome-to-Golgi transport was delayed in a p38 MAPK-dependent manner in Db cells. Furthermore, the degradation pathway of the EGF receptor from endosomes to lysosomes was enhanced in Db cells, and this did not depend on the activation of p38 MAPK. The disease model cell system should become a powerful tool for the detection of aberrant processes in cells under pathogenic conditions and for therapeutic applications.
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Affiliation(s)
- Fumi Kano
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, Japan
- PRESTO, Japan Science and Technology Agency, Saitama, Japan
| | - Daiki Nakatsu
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, Japan
| | - Yoshiyuki Noguchi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, Japan
| | - Akitsugu Yamamoto
- Department of Cell Biology, Nagahama Institute of Bio-Science and Technology, Nagahama, Shiga, Japan
| | - Masayuki Murata
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Meguro-ku, Tokyo, Japan
- * E-mail:
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20
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Dynamic flexibility of the ATPase p97 is important for its interprotomer motion transmission. Proc Natl Acad Sci U S A 2012; 109:9792-7. [PMID: 22675116 DOI: 10.1073/pnas.1205853109] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The hexameric protein p97, a very abundant type II AAA ATPase (ATPase associated with various cellular activities), is involved in a diverse range of cellular functions. During its ATPase cycle p97 functions as an ATP motor, converting the chemical energy released upon hydrolysis of ATP to ADP into mechanical work, which is then directed toward the proteins that serve as substrates. A key question in this process is: How is the nucleotide-induced motion transmitted from the C-terminal ATPase domain (the D2 domain) of p97 to the distant N-terminal substrate-processing domain? We have previously reported the surprising finding that motion transmission between the two ATPase domains (the D2 and D1 domains) is mediated by the D1-D2 linker region of its neighboring protomer. In this study we report efforts to better understand this process. Our findings suggest that the amino acid sequence containing Gly-Gly that is located at the C terminus of the D1-D2 linker functions as a pivoting point that allows the dynamic movement of the D1-D2 linker. Furthermore, we found that locking the D1-D2 linker to the D2 domain by introducing disulfide bonds significantly impaired the motion-transmission process. These results support our previous model for interprotomer motion transmission, and provide more detailed information on how the motion transmission between the two ATPase domains of p97 is relayed by the flexible movement of the D1-D2 linker from its neighboring protomer.
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21
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Puhka M, Joensuu M, Vihinen H, Belevich I, Jokitalo E. Progressive sheet-to-tubule transformation is a general mechanism for endoplasmic reticulum partitioning in dividing mammalian cells. Mol Biol Cell 2012; 23:2424-32. [PMID: 22573885 PMCID: PMC3386207 DOI: 10.1091/mbc.e10-12-0950] [Citation(s) in RCA: 115] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
During mitosis, ER network reorganization can lead to packing of the ER into tight concentric layers at the cell cortex and occurs in tandem with rounding of the cell. Morphometric and 3D EM analysis shows that in addition to reorganization, ER sheets undergo transformation toward more fenestrated and tubular forms before anaphase in mammalian cells. The endoplasmic reticulum (ER) is both structurally and functionally complex, consisting of a dynamic network of interconnected sheets and tubules. To achieve a more comprehensive view of ER organization in interphase and mitotic cells and to address a discrepancy in the field (i.e., whether ER sheets persist, or are transformed to tubules, during mitosis), we analyzed the ER in four different mammalian cell lines using live-cell imaging, high-resolution electron microscopy, and three dimensional electron microscopy. In interphase cells, we found great variation in network organization and sheet structures among different cell lines. In mitotic cells, we show that the ER undergoes both spatial reorganization and structural transformation of sheets toward more fenestrated and tubular forms. However, the extent of spatial reorganization and sheet-to-tubule transformation varies among cell lines. Fenestration and tubulation of the ER correlates with a reduced number of membrane-bound ribosomes.
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Affiliation(s)
- Maija Puhka
- Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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22
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Interprotomer motion-transmission mechanism for the hexameric AAA ATPase p97. Proc Natl Acad Sci U S A 2012; 109:3737-41. [PMID: 22355145 DOI: 10.1073/pnas.1200255109] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Multimeric AAA ATPases represent a structurally homologous yet functionally diverse family of proteins. The essential and highly abundant hexameric AAA ATPase p97 is perhaps the best studied AAA protein, playing an essential role in various important cellular activities. During ATP-hydrolysis process, p97 undergoes dramatic conformational changes, and these changes are initiated in the C-terminal ATPase domain and transmitted across the entire length of the molecule to the N-terminal effector domain. However, the detailed mechanism of the motion transmission remains unclear. Here, we report an interprotomer motion-transmission mechanism to explain this process: The nucleotide-dependent motion transmission between the two ATPase domains of one protomer is mediated by its neighboring protomer. This finding reveals a strict requirement for interprotomer coordination of p97 during the motion-transmission process and may shed light on studies of other AAA ATPases.
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23
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Naydenov NG, Harris G, Brown B, Schaefer KL, Das SK, Fisher PB, Ivanov AI. Loss of soluble N-ethylmaleimide-sensitive factor attachment protein α (αSNAP) induces epithelial cell apoptosis via down-regulation of Bcl-2 expression and disruption of the Golgi. J Biol Chem 2011; 287:5928-41. [PMID: 22194596 DOI: 10.1074/jbc.m111.278358] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Intracellular trafficking represents a key mechanism that regulates cell fate by participating in either prodeath or prosurvival signaling. Soluble N-ethylmaleimide-sensitive factor (NSF) attachment protein α (αSNAP) is a well known component of vesicle trafficking machinery that mediates intermembrane fusion. αSNAP increases cell resistance to cytotoxic stimuli, although mechanisms of its prosurvival function are poorly understood. In this study, we found that either siRNA-mediated knockdown of αSNAP or expression of its dominant negative mutant induced epithelial cell apoptosis. Apoptosis was not caused by activation of the major prodeath regulators Bax and p53 and was independent of a key αSNAP binding partner, NSF. Instead, death of αSNAP-depleted cells was accompanied by down-regulation of the antiapoptotic Bcl-2 protein; it was mimicked by inhibition and attenuated by overexpression of Bcl-2. Knockdown of αSNAP resulted in impairment of Golgi to endoplasmic reticulum (ER) trafficking and fragmentation of the Golgi. Moreover, pharmacological disruption of ER-Golgi transport by brefeldin A and eeyarestatin 1 or siRNA-mediated depletion of an ER/Golgi-associated p97 ATPase recapitulated the effects of αSNAP inhibition by decreasing Bcl-2 level and triggering apoptosis. These results reveal a novel role for αSNAP in promoting epithelial cell survival by unique mechanisms involving regulation of Bcl-2 expression and Golgi biogenesis.
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Affiliation(s)
- Nayden G Naydenov
- Department of Medicine, University of Rochester, Rochester, New York 14642, USA
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24
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Ramanathan HN, Ye Y. The p97 ATPase associates with EEA1 to regulate the size of early endosomes. Cell Res 2011; 22:346-59. [PMID: 21556036 DOI: 10.1038/cr.2011.80] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The AAA (ATPase-associated with various cellular activities) ATPase p97 acts on diverse substrate proteins to partake in various cellular processes such as membrane fusion and endoplasmic reticulum-associated degradation (ERAD). In membrane fusion, p97 is thought to function in analogy to the related ATPase NSF (N-ethylmaleimide-sensitive fusion protein), which promotes membrane fusion by disassembling a SNARE complex. In ERAD, p97 dislocates misfolded proteins from the ER membrane to facilitate their turnover by the proteasome. Here, we identify a novel function of p97 in endocytic trafficking by establishing the early endosomal autoantigen 1 (EEA1) as a new p97 substrate. We demonstrate that a fraction of p97 is localized to the early endosome membrane, where it binds EEA1 via the N-terminal C2H2 zinc finger domain. Inhibition of p97 either by siRNA or a pharmacological inhibitor results in clustering and enlargement of early endosomes, which is associated with an altered trafficking pattern for an endocytic cargo. Mechanistically, we show that p97 inhibition causes increased EEA1 self-association at the endosome membrane. We propose that p97 may regulate the size of early endosomes by governing the oligomeric state of EEA1.
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Affiliation(s)
- Harish N Ramanathan
- Laboratory of Molecular Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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25
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Thomas U, Kobler O, Gundelfinger ED. TheDrosophilaLarval Neuromuscular Junction as a Model for Scaffold Complexes at Glutamatergic Synapses: Benefits and Limitations. J Neurogenet 2010; 24:109-19. [DOI: 10.3109/01677063.2010.493589] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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26
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Khoshnood A, Noguchi H, Gompper G. Lipid membranes with transmembrane proteins in shear flow. J Chem Phys 2010; 132:025101. [PMID: 20095714 DOI: 10.1063/1.3285269] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The effects of embedded proteins on the dynamical properties of lipid bilayer membranes are studied in shear flow. Coarse-grained molecular simulations are employed, in which lipids are modeled as short polymers consisting of hydrophilic head groups and hydrophobic tail monomers; similarly, transmembrane proteins are modeled as connected hydrophobic double- or triple-chain molecules with hydrophilic groups at both ends. In thermal equilibrium, rigid proteinlike molecules aggregate in a membrane of flexible lipids, while flexible proteins do not aggregate. In shear flow parallel to the membrane, the monolayers of lipid bilayer slide over each other. The presence of transmembrane proteins enhances the intermonolayer friction. The friction coefficient depends on the chain lengths of lipids, the membrane tension, the length of the protein, and the cluster size. It is found to increase with protein length (with positive mismatch, i.e., proteins which are longer than the membrane thickness) and protein cluster size. In flow, proteins get oriented in the flow direction to reduce friction, with large fluctuations of the orientation angle.
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Affiliation(s)
- Atefeh Khoshnood
- Department of Mechanical Engineering, Computational Mechanics Laboratory, Sharif University of Technology, Azadi Avenue, Tehran, Iran.
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27
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Guanine Exchange Factor Vav2: A Novel Potential Target for the Development of Drugs Effective in the Prevention of Papillomavirus Infection and Disease. Am J Ther 2009; 16:496-507. [DOI: 10.1097/mjt.0b013e31819be0a5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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28
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Woźniak MJ, Bola B, Brownhill K, Yang YC, Levakova V, Allan VJ. Role of kinesin-1 and cytoplasmic dynein in endoplasmic reticulum movement in VERO cells. J Cell Sci 2009; 122:1979-89. [PMID: 19454478 DOI: 10.1242/jcs.041962] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Generating the extended endoplasmic reticulum (ER) network depends on microtubules, which act as tracks for motor-driven ER tubule movement, generate the force to extend ER tubules by means of attachment to growing microtubule plus-ends and provide static attachment points. We have analysed ER dynamics in living VERO cells and find that most ER tubule extension is driven by microtubule motors. Surprisingly, we observe that approximately 50% of rapid ER tubule movements occur in the direction of the centre of the cell, driven by cytoplasmic dynein. Inhibition of this movement leads to an accumulation of lamellar ER in the cell periphery. By expressing dominant-negative kinesin-1 constructs, we show that kinesin-1 drives ER tubule extension towards the cell periphery and that this motility is dependent on the KLC1B kinesin light chain splice form but not on KLC1D. Inhibition of kinesin-1 promotes a shift from tubular to lamellar morphology and slows down the recovery of the ER network after microtubule depolymerisation and regrowth. These observations reconcile previous conflicting studies of kinesin-1 function in ER motility in vivo. Furthermore, our data reveal that cytoplasmic dynein plays a role in ER motility in a mammalian cultured cell, demonstrating that ER motility is more complex than previously thought.
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Affiliation(s)
- Marcin J Woźniak
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester, UK M13 9PT
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29
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Iinuma T, Aoki T, Arasaki K, Hirose H, Yamamoto A, Samata R, Hauri HP, Arimitsu N, Tagaya M, Tani K. Role of syntaxin 18 in the organization of endoplasmic reticulum subdomains. J Cell Sci 2009; 122:1680-90. [PMID: 19401338 DOI: 10.1242/jcs.036103] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The presence of subdomains in the endoplasmic reticulum (ER) enables this organelle to perform a variety of functions, yet the mechanisms underlying their organization are poorly understood. In the present study, we show that syntaxin 18, a SNAP (soluble NSF attachment protein) receptor localized in the ER, is important for the organization of two ER subdomains, smooth/rough ER membranes and ER exit sites. Knockdown of syntaxin 18 caused a global change in ER membrane architecture, leading to the segregation of the smooth and rough ER. Furthermore, the organization of ER exit sites was markedly changed concomitantly with dispersion of the ER-Golgi intermediate compartment and the Golgi complex. These morphological changes in the ER were substantially recovered by treatment of syntaxin-18-depleted cells with brefeldin A, a reagent that stimulates retrograde membrane flow to the ER. These results suggest that syntaxin 18 has an important role in ER subdomain organization by mediating the fusion of retrograde membrane carriers with the ER membrane.
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Affiliation(s)
- Takayuki Iinuma
- School of Life Sciences, Tokyo University of Pharmacy and Life Sciences, Hachioji, Tokyo 192-0392, Japan
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30
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Members of a mammalian SNARE complex interact in the endoplasmic reticulum in vivo and are found in COPI vesicles. Eur J Cell Biol 2008; 87:863-78. [DOI: 10.1016/j.ejcb.2008.07.003] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2008] [Revised: 06/19/2008] [Accepted: 07/03/2008] [Indexed: 11/18/2022] Open
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31
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Abstract
Protein modification by ubiquitin and ubiquitin-like molecules is a critical regulatory process. Like most regulated protein modifications, ubiquitination is reversible. Deubiquitination, the reversal of ubiquitination, is quickly being recognized as an important regulatory strategy. Nearly one hundred human DUBs (deubiquitinating enzymes) in five different gene families oppose the action of several hundred ubiquitin ligases, suggesting that both ubiquitination and its reversal are highly regulated and specific processes. It has long been recognized that ubiquitin ligases are modular enzyme systems that often depend on scaffolds and adaptors to deliver substrates to the catalytically active macromolecular complex. Although many DUBs bind ubiquitin with reasonable affinities (in the nM to microM range), a larger number have little affinity but exhibit robust catalytic capability. Thus it is apparent that these DUBs must acquire their substrates by binding the target protein in a conjugate or by associating with other macromolecular complexes. We would then expect that a study of protein partners of DUBs would reveal a variety of substrates, scaffolds, adaptors and ubiquitin receptors. In the present review we suggest that, like ligases, much of the regulation and specificity of deubiquitination arises from the association of DUBs with these protein partners.
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32
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Mukhopadhyay S, Lee J, Sehgal PB. Depletion of the ATPase NSF from Golgi membranes with hypo-S-nitrosylation of vasorelevant proteins in endothelial cells exposed to monocrotaline pyrrole. Am J Physiol Heart Circ Physiol 2008; 295:H1943-55. [PMID: 18775848 DOI: 10.1152/ajpheart.00642.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Investigations of regulated S-nitrosylation and denitrosylation of vasorelevant proteins are a newly emergent area in vascular biology. We previously showed that monocrotaline pyrrole (MCTP)-induced megalocytosis of pulmonary arterial endothelial cells (PAECs), which underlies the development of pulmonary arterial hypertension, was associated with a Golgi blockade characterized by the trapping of diverse vesicle tethers, soluble N-ethylmaleimide-sensitive factor (NSF)-attachment protein receptors (SNAREs), and soluble NSF-attachment proteins (SNAPs) in the Golgi; reduced trafficking of caveolin-1 (cav-1) and endotheial nitric oxide (NO) synthase (eNOS) from the Golgi to the plasma membrane; and decreased caveolar NO. We have investigated whether NSF, the ATPase involved in all SNARE disassembly, might be the upstream target of MCTP and whether MCTP might regulate NSF by S-nitrosylation. Immunofluorescence microscopy and Golgi purification techniques revealed the discordant decrease of NSF by approximately 50% in Golgi membranes after MCTP despite increases in alpha-SNAP, cav-1, eNOS, and syntaxin-6. The NO scavenger (4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide failed to affect the initiation or progression of MCTP megalocytosis despite a reduction of 4,5-diaminofluorescein diacetate fluorescence and inhibition of S-nitrosylation of eNOS as assayed using the biotin-switch method. Moreover, the latter assay not only revealed constitutive S-nitrosylation of NSF, eNOS, cav-1, and clathrin heavy chain (CHC) in PAECs but also a dramatic 70-95% decrease in the S-nitrosylation of NSF, eNOS, cav-1, and CHC after MCTP. These data point to depletion of NSF from Golgi membranes as a mechanism for Golgi blockade after MCTP and to denitrosylation of vasorelevant proteins as critical to the development of endothelial cell megalocytosis.
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33
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Li G, Zhao G, Schindelin H, Lennarz WJ. Tyrosine phosphorylation of ATPase p97 regulates its activity during ERAD. Biochem Biophys Res Commun 2008; 375:247-51. [PMID: 18706391 DOI: 10.1016/j.bbrc.2008.08.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2008] [Accepted: 08/02/2008] [Indexed: 12/01/2022]
Abstract
In eukaryotic cells, the endoplasmic reticulum-associated degradation (ERAD) pathway is essential for the disposal of misfolded proteins. Recently, we demonstrated the existence of a higher order complex consisting of the ER bound E3 ligase gp78, p97, PNGase, and HR23B in mammals. This complex may serve to facilitate the routing of misfolded glycoproteins out of the ER to the cytosol where they are degraded by the proteasome. In this complex, p97 functions as an organizer to mediate the interactions with gp78 and the deglycosylating enzyme PNGase. A novel protein-binding motif of mouse p97 was identified that consists of its last 10 amino acid residues; this motif is sufficient to mediate the interaction of p97 with PNGase and Ufd3. Phosphorylation of p97's highly conserved penultimate tyrosine residue, completely blocks binding of both PNGase and Ufd3 to mp97. We have found that c-Src kinase directly and selectively phosphorylated the penultimate tyrosine of p97 in vitro, and that overexpression of c-Src significantly increased the phosphorylation level of p97 in cells and caused accumulation of the ERAD substrate TCRalpha-GFP, as well as ubiquitin-conjugated substrates. These results suggest a role for p97 phosphorylation in the degradation of misfolded glycoproteins.
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Affiliation(s)
- Guangtao Li
- Department of Biochemistry and Cell Biology, 450 Life Science Building, Stony Brook University, Stony Brook, NY 11794-5215, USA
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Puhka M, Vihinen H, Joensuu M, Jokitalo E. Endoplasmic reticulum remains continuous and undergoes sheet-to-tubule transformation during cell division in mammalian cells. ACTA ACUST UNITED AC 2007; 179:895-909. [PMID: 18056408 PMCID: PMC2099207 DOI: 10.1083/jcb.200705112] [Citation(s) in RCA: 187] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The endoplasmic reticulum (ER) is a multifaceted cellular organelle both structurally and functionally, and its cell cycle–dependent morphological changes are poorly understood. Our quantitative confocal and EM analyses show that the ER undergoes dramatic reorganization during cell division in cultured mammalian cells as mitotic ER profiles become shorter and more branched. 3D modeling by electron tomography reveals that the abundant interphase structures, sheets, are lost and subsequently transform into a branched tubular network that remains continuous. This is confirmed by observing the most prominent ER subdomain, the nuclear envelope (NE). A NE marker protein spreads to the mitotic ER tubules, although it does not show a homogenous distribution within the network. We mimicked the mitotic ER reorganization using puromycin to strip the membrane-bound ribosomes from the interphase ER corresponding to the observed loss of ribosomes normally occurring during mitosis. We propose that the structural changes in mitotic ER are linked to ribosomal action on the ER membranes.
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Affiliation(s)
- Maija Puhka
- Electron Microscopy Unit, Institute of Biotechnology, University of Helsinki, 00014 Helsinki, Finland
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35
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Lowe M, Barr FA. Inheritance and biogenesis of organelles in the secretory pathway. Nat Rev Mol Cell Biol 2007; 8:429-39. [PMID: 17505521 DOI: 10.1038/nrm2179] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
In eukaryotic cells, cellular functions are compartmentalized into membrane-bound organelles. This has many advantages, as shown by the success of the eukaryotic lineage, but creates many problems for cells, such as the need to build and partition these organelles during cell growth and division. Diverse mechanisms for biogenesis of the endoplasmic reticulum and Golgi apparatus have evolved, ranging from de novo synthesis to the copying of a template organelle. The different mechanisms by which organelles are inherited in yeasts, protozoa and metazoans probably reflect the differences in the structure and copy number of these organelles.
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Affiliation(s)
- Martin Lowe
- Faculty of Life Sciences, University of Manchester, The Michael Smith Building, Oxford Road, Manchester M13 9PT, UK
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36
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Gorczyca D, Ashley J, Speese S, Gherbesi N, Thomas U, Gundelfinger E, Gramates LS, Budnik V. Postsynaptic membrane addition depends on the Discs-Large-interacting t-SNARE Gtaxin. J Neurosci 2007; 27:1033-44. [PMID: 17267557 PMCID: PMC4664082 DOI: 10.1523/jneurosci.3160-06.2007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Targeted membrane addition is a hallmark of many cellular functions. In the nervous system, modification of synaptic membrane size has a major impact on synaptic function. However, because of the complex shape of neurons and the need to target membrane addition to very small and polarized synaptic compartments, this process is poorly understood. Here, we show that Gtaxin (GTX), a Drosophila t-SNARE (target-soluble N-ethylmaleimide-sensitive factor attachment protein receptor), is required for expansion of postsynaptic membranes during new synapse formation. Mutations in gtx lead to drastic reductions in postsynaptic membrane surface, whereas gtx upregulation results in the formation of complex membrane structures at ectopic sites. Postsynaptic GTX activity depends on its direct interaction with Discs-Large (DLG), a multidomain scaffolding protein of the PSD-95 (postsynaptic density protein-95) family with key roles in cell polarity and formation of cellular junctions as well as synaptic protein anchoring and trafficking. We show that DLG selectively determines the postsynaptic distribution of GTX to type I, but not to type II or type III boutons on the same cell, thereby defining sites of membrane addition to this unique set of glutamatergic synapses. We provide a mechanistic explanation for selective targeted membrane expansion at specific synaptic junctions.
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Affiliation(s)
- David Gorczyca
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - James Ashley
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Sean Speese
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Norberto Gherbesi
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Ulrich Thomas
- Leibniz Institute for Neurobiology, 39118 Magdeburg, Germany, and
| | | | - L. Sian Gramates
- Molecular and Cellular Biology Graduate Program, University of Massachusetts at Amherst, Amherst, Massachusetts 01003
| | - Vivian Budnik
- Department of Neurobiology, University of Massachusetts Medical School, Worcester, Massachusetts 01605
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37
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Abstract
Most membrane-bound organelles have elaborate, dynamic shapes and often include regions with distinct morphologies. These complex structures are relatively conserved throughout evolution, which indicates that they are important for optimal organelle function. Various mechanisms of determining organelle shape have been proposed - proteins that stabilize highly curved membranes, the tethering of organelles to other cellular components and the regulation of membrane fission and fusion might all contribute.
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Affiliation(s)
- Gia K Voeltz
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309, USA.
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38
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Latterich M. p97 adaptor choice regulates organelle biogenesis. Dev Cell 2007; 11:755-7. [PMID: 17141151 DOI: 10.1016/j.devcel.2006.11.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The AAA protein p97 requires adaptor-like cofactors for its numerous cellular functions. In this issue of Developmental Cell, Uchiyama et al. (2006) identify p37 as a p97 adaptor that is required constitutively for ER and Golgi membrane fusion, analogous to the mitotic membrane fusion role of the adaptor p47. Their study suggests that related p97 adaptors involved in similar cellular pathways can be subject to differential regulation.
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Affiliation(s)
- Martin Latterich
- Department of Anatomy and Cell Biology, McGill University, 3640 University Street, Montreal, Quebec, H3A 2B2, Canada
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39
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Jentsch S, Rumpf S. Cdc48 (p97): a "molecular gearbox" in the ubiquitin pathway? Trends Biochem Sci 2006; 32:6-11. [PMID: 17142044 DOI: 10.1016/j.tibs.2006.11.005] [Citation(s) in RCA: 239] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2006] [Revised: 11/07/2006] [Accepted: 11/23/2006] [Indexed: 10/23/2022]
Abstract
Cdc48 (p97), a conserved chaperone-like ATPase of eukaryotic cells, has attracted attention recently because of its wide range of cellular functions. Cdc48 is intimately linked to the ubiquitin pathway because its primary action is to segregate ubiquitinated substrates from unmodified partners. This 'segregase' activity is crucial for certain proteasomal degradation pathways and for some nonproteolytic functions of ubiquitin. Cdc48 associates not only with different 'substrate-recruiting cofactors' but also with distinct 'substrate-processing cofactors'. The latter proteins control the degree of ubiquitination of bound substrates by shifting the polyubiquitination reaction into 'forward', 'neutral' or 'reverse'. We discuss how Cdc48 might use this 'gearbox activity' to control protein fate and propose a similar mode of action for the 19S cap of the proteasome.
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Affiliation(s)
- Stefan Jentsch
- Department of Molecular Cell Biology, Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
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40
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Mimnaugh EG, Xu W, Vos M, Yuan X, Neckers L. Endoplasmic Reticulum Vacuolization and Valosin-Containing Protein Relocalization Result from Simultaneous Hsp90 Inhibition by Geldanamycin and Proteasome Inhibition by Velcade. Mol Cancer Res 2006; 4:667-81. [PMID: 16966435 DOI: 10.1158/1541-7786.mcr-06-0019] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Geldanamycin and Velcade, new anticancer drugs with novel mechanisms of action, are currently undergoing extensive clinical trials. Geldanamycin interrupts Hsp90 chaperone activity and causes down-regulation of its many client proteins by the ubiquitin-proteasome pathway; Velcade is a specific proteasome inhibitor. Misfolded Hsp90 clients within the endoplasmic reticulum (ER) lumen are cleared by ER--associated protein degradation, a sequential process requiring valosin-containing protein (VCP)-dependent retrotranslocation followed by ubiquitination and proteasomal proteolysis. Cotreatment of cells with geldanamycin and Velcade prevents destruction of destabilized, ubiquitinated Hsp90 client proteins, causing them to accumulate. Here, we report that misfolded protein accumulation within the ER resulting from geldanamycin and Velcade exposure overwhelms the ability of the VCP--centered machine to maintain the ER secretory pathway, causing the ER to distend into conspicuous vacuoles. Overexpression of dominant-negative VCP or the "small VCP--interacting protein" exactly recapitulated the vacuolated phenotype provoked by the drugs, associating loss of VCP function with ER vacuolization. In cells transfected with a VCP--enhanced yellow fluorescent protein fluorescent construct, geldanamycin plus Velcade treatment redistributed VCP--enhanced yellow fluorescent protein from the cytoplasm and ER into perinuclear aggresomes. In further support of the view that compromise of VCP function is responsible for ER vacuolization, small interfering RNA interference of VCP expression induced ER vacuolization that was markedly increased by Velcade. VCP knockdown by small interfering RNA eventually deconstructed both the ER and Golgi and interdicted protein trafficking through the secretory pathway to the plasma membrane. Thus, simultaneous geldanamycin and Velcade treatment has far-reaching secondary cytotoxic consequences that likely contribute to the cytotoxic activity of this anticancer drug combination.
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Affiliation(s)
- Edward G Mimnaugh
- Urologic Oncology Branch, Center for Cancer Research, National Cancer Institute, NIH, 9000 Rockville Pike, Building 10, Room 1-5940, Bethesda, MD 20892-1107, USA
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41
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Abstract
The endoplasmic reticulum (ER) of higher eukaryotic cells is a dynamic network of interconnected membrane tubules that pervades almost the entire cytoplasm. On the basis of the morphological changes induced by the disruption of the cytoskeleton or molecular motor proteins, the commonly accepted model has emerged that microtubules and conventional kinesin (kinesin-1) are essential determinants in establishing and maintaining the structure of the ER by active membrane expansion. Surprisingly, very similar ER phenotypes have now been observed when the cytoskeleton-linking ER membrane protein of 63 kDa (CLIMP-63) is mutated, revealing stable attachment of ER membranes to the microtubular cytoskeleton as a novel requirement for ER maintenance. Additional recent findings suggest that ER maintenance also requires ongoing homotypic membrane fusion, possibly controlled by the p97/p47/VICP135 protein complex. Work on other proteins proposed to regulate ER structure, including huntingtin, the EF-hand Ca(2+)-binding protein p22, the vesicle-associated membrane protein-associated protein B and kinectin isoforms further contribute to the new emerging concept that ER shape is not only determined by motor driven processes but by a variety of different mechanisms.
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Affiliation(s)
- Cécile Vedrenne
- Biozentrum, University of Basel, Klingelbergstrasse 70, CH-4056 Basel, Switzerland
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42
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Millard SM, Wood SA. Riding the DUBway: regulation of protein trafficking by deubiquitylating enzymes. ACTA ACUST UNITED AC 2006; 173:463-8. [PMID: 16702236 PMCID: PMC2063856 DOI: 10.1083/jcb.200602082] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ubiquitylation is a key regulator of protein trafficking, and much about the functions of ubiquitin ligases, which add ubiquitin to substrates in this regulation, has recently come to light. However, a clear understanding of ubiquitin-dependent protein localization cannot be achieved without knowledge of the role of deubiquitylating enzymes (DUBs). DUBs, by definition, function downstream in ubiquitin pathways and, as such, have the potential to be the final editors of protein ubiquitylation status, thus determining substrate fate. This paper assimilates the current evidence concerning the substrates and activities of DUBs that regulate protein trafficking.
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Affiliation(s)
- Susan M Millard
- Child Health Research Institute, North Adelaide, South Australia 5006, Australia
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43
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Beuron F, Dreveny I, Yuan X, Pye VE, Mckeown C, Briggs LC, Cliff MJ, Kaneko Y, Wallis R, Isaacson RL, Ladbury JE, Matthews SJ, Kondo H, Zhang X, Freemont PS. Conformational changes in the AAA ATPase p97-p47 adaptor complex. EMBO J 2006; 25:1967-76. [PMID: 16601695 PMCID: PMC1456939 DOI: 10.1038/sj.emboj.7601055] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2005] [Accepted: 02/27/2006] [Indexed: 11/08/2022] Open
Abstract
The AAA+ATPase p97/VCP, helped by adaptor proteins, exerts its essential role in cellular events such as endoplasmic reticulum-associated protein degradation or the reassembly of Golgi, ER and the nuclear envelope after mitosis. Here, we report the three-dimensional cryo-electron microscopy structures at approximately 20 Angstroms resolution in two nucleotide states of the endogenous hexameric p97 in complex with a recombinant p47 trimer, one of the major p97 adaptor proteins involved in membrane fusion. Depending on the nucleotide state, we observe the p47 trimer to be in two distinct arrangements on top of the p97 hexamer. By combining the EM data with NMR and other biophysical measurements, we propose a model of ATP-dependent p97(N) domain motions that lead to a rearrangement of p47 domains, which could result in the disassembly of target protein complexes.
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Affiliation(s)
- Fabienne Beuron
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
| | - Ingrid Dreveny
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
| | - Xuemei Yuan
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
| | - Valerie E Pye
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
| | - Ciaran Mckeown
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
| | - Louise C Briggs
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
| | - Matthew J Cliff
- Department of Biochemistry and Molecular Biology, University College London, London, UK
| | - Yayoi Kaneko
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
- PRESTO and SORST, Japan Science and Technology Corporation, Japan
| | - Russell Wallis
- Department of Biochemistry, University of Oxford, Oxford, UK
- Department of Infection, Immunity, and Inflammation, Medical Research Council Immunochemistry Unit, University of Leicester, Leicester, UK
| | - Rivka L Isaacson
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
| | - John E Ladbury
- Department of Biochemistry and Molecular Biology, University College London, London, UK
| | - Steve J Matthews
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
| | - Hisao Kondo
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK
- PRESTO and SORST, Japan Science and Technology Corporation, Japan
| | - Xiaodong Zhang
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
| | - Paul S Freemont
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington, London, UK
- Centre for Structural Biology, Division of Molecular Biosciences, Imperial College London, South Kensington Campus, Biochemistry Building, South Kensington, London SW7 2AZ, UK. Tel.: +44 20 7594 5327; Fax: +44 20 7594 3057; E-mail:
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