1
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Sawyer EM, Jensen LE, Meehl JB, Larsen KP, Petito DA, Hurley JH, Voeltz GK. SigmaR1 shapes rough endoplasmic reticulum membrane sheets. Dev Cell 2024:S1534-5807(24)00382-4. [PMID: 38971154 DOI: 10.1016/j.devcel.2024.06.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2023] [Revised: 02/12/2024] [Accepted: 06/07/2024] [Indexed: 07/08/2024]
Abstract
Rough endoplasmic reticulum (ER) sheets are a fundamental domain of the ER and the gateway into the secretory pathway. Although reticulon proteins stabilize high-curvature ER tubules, it is unclear whether other proteins scaffold the flat membranes of rough ER sheets. Through a proteomics screen using ER sheet-localized RNA-binding proteins as bait, we identify the sigma-1 receptor (SigmaR1) as an ER sheet-shaping factor. High-resolution live cell imaging and electron tomography assign SigmaR1 as an ER sheet-localized factor whose levels determine the amount of rough ER sheets in cells. Structure-guided mutagenesis and in vitro reconstitution on giant unilamellar vesicles further support a mechanism whereby SigmaR1 oligomers use their extended arrays of amphipathic helices to bind and flatten the lumenal leaflet of ER membranes to oppose membrane curvature and stabilize rough ER sheets.
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Affiliation(s)
- Eric M Sawyer
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Howard Hughes Medical Institute
| | - Liv E Jensen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Janet B Meehl
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Howard Hughes Medical Institute
| | - Kevin P Larsen
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Daniel A Petito
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Howard Hughes Medical Institute
| | - James H Hurley
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA 94720, USA; Helen Wills Neuroscience Institute, University of California, Berkeley, Berkeley, CA 94720, USA
| | - Gia K Voeltz
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, CO 80309, USA; Howard Hughes Medical Institute.
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2
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Falahati H, Wu Y, De Camilli P. Ectopic Reconstitution of a Spine-Apparatus Like Structure Provides Insight into Mechanisms Underlying Its Formation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.16.589782. [PMID: 38659799 PMCID: PMC11042382 DOI: 10.1101/2024.04.16.589782] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The endoplasmic reticulum (ER) is a continuous cellular endomembrane network that displays focal specializations. Most notable examples of such specializations include the spine apparatus of neuronal dendrites, and the cisternal organelle of axonal initial segments. Both organelles exhibit stacks of smooth ER sheets with a narrow lumen and interconnected by a dense protein matrix. The actin-binding protein synaptopodin is required for their formation. Here, we report that expression in non-neuronal cells of a synaptopodin construct targeted to the ER is sufficient to generate stacked ER cisterns resembling the spine apparatus with molecular properties distinct from the surrounding ER. Cisterns within these stacks are connected to each other by an actin-based matrix that contains proteins also found at the spine apparatus of neuronal spines. These findings reveal a critical role of a synaptopodin-dependent actin matrix in generating cisternal stacks. These ectopically generated structures provide insight into spine apparatus morphogenesis.
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Affiliation(s)
- Hanieh Falahati
- HHMI; Departments of Neuroscience and Cell Biology; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, 100 College Street, New Haven, 06511, CT, USA
| | - Yumei Wu
- HHMI; Departments of Neuroscience and Cell Biology; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, 100 College Street, New Haven, 06511, CT, USA
| | - Pietro De Camilli
- HHMI; Departments of Neuroscience and Cell Biology; Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, 100 College Street, New Haven, 06511, CT, USA
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3
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Crapart CC, Scott ZC, Konno T, Sharma A, Parutto P, Bailey DMD, Westrate LM, Avezov E, Koslover EF. Luminal transport through intact endoplasmic reticulum limits the magnitude of localized Ca 2+ signals. Proc Natl Acad Sci U S A 2024; 121:e2312172121. [PMID: 38502705 PMCID: PMC10990089 DOI: 10.1073/pnas.2312172121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2023] [Accepted: 02/09/2024] [Indexed: 03/21/2024] Open
Abstract
The endoplasmic reticulum (ER) forms an interconnected network of tubules stretching throughout the cell. Understanding how ER functionality relies on its structural organization is crucial for elucidating cellular vulnerability to ER perturbations, which have been implicated in several neuronal pathologies. One of the key functions of the ER is enabling Ca[Formula: see text] signaling by storing large quantities of this ion and releasing it into the cytoplasm in a spatiotemporally controlled manner. Through a combination of physical modeling and live-cell imaging, we demonstrate that alterations in ER shape significantly impact its ability to support efficient local Ca[Formula: see text] releases, due to hindered transport of luminal content within the ER. Our model reveals that rapid Ca[Formula: see text] release necessitates mobile luminal buffer proteins with moderate binding strength, moving through a well-connected network of ER tubules. These findings provide insight into the functional advantages of normal ER architecture, emphasizing its importance as a kinetically efficient intracellular Ca[Formula: see text] delivery system.
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Affiliation(s)
- Cécile C. Crapart
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | | | - Tasuku Konno
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | - Aman Sharma
- Department of Physics, University of California, San Diego, La Jolla, CA92130
| | - Pierre Parutto
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | - David M. D. Bailey
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | - Laura M. Westrate
- Department of Chemistry and Biochemistry, Calvin University, Grand Rapids, MI49546
| | - Edward Avezov
- UK Dementia Research Institute at the University of Cambridge, CambridgeCB2 0AH, United Kingdom
- Department of Clinical Neurosciences, School of Clinical Medicine, The University of Cambridge, CambridgeCB2 0AH, United Kingdom
| | - Elena F. Koslover
- Department of Physics, University of California, San Diego, La Jolla, CA92130
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4
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Zhang W, Zhang Z, Xiang Y, Gu DD, Chen J, Chen Y, Zhai S, Liu Y, Jiang T, Liu C, He B, Yan M, Wang Z, Xu J, Cao YL, Deng B, Zeng D, Lei J, Zhuo J, Lei X, Long Z, Jin B, Chen T, Li D, Shen Y, Hu J, Gao S, Liu Q. Aurora kinase A-mediated phosphorylation triggers structural alteration of Rab1A to enhance ER complexity during mitosis. Nat Struct Mol Biol 2024; 31:219-231. [PMID: 38177680 DOI: 10.1038/s41594-023-01165-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Accepted: 10/26/2023] [Indexed: 01/06/2024]
Abstract
Morphological rearrangement of the endoplasmic reticulum (ER) is critical for metazoan mitosis. Yet, how the ER is remodeled by the mitotic signaling remains unclear. Here, we report that mitotic Aurora kinase A (AURKA) employs a small GTPase, Rab1A, to direct ER remodeling. During mitosis, AURKA phosphorylates Rab1A at Thr75. Structural analysis demonstrates that Thr75 phosphorylation renders Rab1A in a constantly active state by preventing interaction with GDP-dissociation inhibitor (GDI). Activated Rab1A is retained on the ER and induces the oligomerization of ER-shaping protein RTNs and REEPs, eventually triggering an increase of ER complexity. In various models, from Caenorhabditis elegans and Drosophila to mammals, inhibition of Rab1AThr75 phosphorylation by genetic modifications disrupts ER remodeling. Thus, our study reveals an evolutionarily conserved mechanism explaining how mitotic kinase controls ER remodeling and uncovers a critical function of Rab GTPases in metaphase.
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Affiliation(s)
- Wei Zhang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
- Department of Clinical Immunology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Zijian Zhang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Yun Xiang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Dong-Dong Gu
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Jinna Chen
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Yifan Chen
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Shixian Zhai
- MOE Key Laboratory of Laser Life Science and College of Biophotonics, South China Normal University, Guangzhou, China
| | - Yong Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Tao Jiang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Chong Liu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Bin He
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Min Yan
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Zifeng Wang
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Jie Xu
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Yu-Lu Cao
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Bing Deng
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Deshun Zeng
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Jie Lei
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Junxiao Zhuo
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Xinxing Lei
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China
| | - Zijie Long
- Department of Hematology, The Third Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
- Institute of Hematology, Sun Yat-sen University, Guangzhou, China
| | - Bilian Jin
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China
| | - Tongsheng Chen
- MOE Key Laboratory of Laser Life Science and College of Biophotonics, South China Normal University, Guangzhou, China
| | - Dong Li
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yidong Shen
- University of Chinese Academy of Sciences, Beijing, China
- State Key Laboratory of Cell Biology, Shanghai Institute of Biochemistry and Cell Biology, Center for Excellence in Molecular Cell Science, Chinese Academy of Sciences, Shanghai, China
| | - Junjie Hu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
- University of Chinese Academy of Sciences, Beijing, China.
| | - Song Gao
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China.
| | - Quentin Liu
- State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Sun Yat-sen University Cancer Center, Guangzhou, P.R. China.
- Institute of Cancer Stem Cell, Dalian Medical University, Dalian, China.
- Institute of Hematology, Sun Yat-sen University, Guangzhou, China.
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5
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Fuentes LA, Marin Z, Tyson J, Baddeley D, Bewersdorf J. The nanoscale organization of reticulon 4 shapes local endoplasmic reticulum structure in situ. J Cell Biol 2023; 222:e202301112. [PMID: 37516910 PMCID: PMC10373298 DOI: 10.1083/jcb.202301112] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2023] [Revised: 05/31/2023] [Accepted: 07/06/2023] [Indexed: 07/31/2023] Open
Abstract
The endoplasmic reticulum's (ER's) structure is directly linked to the many functions of the ER, but its formation is not fully understood. We investigate how the ER-membrane curving protein reticulon 4 (Rtn4) localizes to and organizes in the membrane and how that affects the local ER structure. We show a strong correlation between the local Rtn4 density and the local ER membrane curvature. Our data further reveal that the typical ER tubule possesses an elliptical cross-section with Rtn4 enriched at either end of the major axis. Rtn4 oligomers are linear shaped, contain about five copies of the protein, and preferentially orient parallel to the tubule axis. Our observations support a mechanism in which oligomerization leads to an increase of the local Rtn4 concentration with each molecule, increasing membrane curvature through a hairpin wedging mechanism. This quantitative analysis of Rtn4 and its effects on the ER membrane result in a new model of tubule shape as it relates to Rtn4.
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Affiliation(s)
- Lukas A. Fuentes
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Zach Marin
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Jonathan Tyson
- Department of Chemistry, Yale University, New Haven, CT, USA
| | - David Baddeley
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Department of Physics, Yale University, New Haven, CT, USA
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6
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Accogli A, Zaki MS, Al-Owain M, Otaif MY, Jackson A, Argilli E, Chandler KE, De Goede CGEL, Cora T, Alvi JR, Eslahi A, Asl Mohajeri MS, Ashtiani S, Au PYB, Scocchia A, Alakurtti K, Pagnamenta AT, Toosi MB, Karimiani EG, Mojarrad M, Arab F, Duymuş F, Scantlebury MH, Yeşil G, Rosenfeld JA, Türkyılmaz A, Sağer SG, Sultan T, Ashrafzadeh F, Zahra T, Rahman F, Maqbool S, Abdel-Hamid MS, Issa MY, Efthymiou S, Bauer P, Zifarelli G, Salpietro V, Al-Hassnan Z, Banka S, Sherr EH, Gleeson JG, Striano P, Houlden H, Severino M, Maroofian R. Lunapark deficiency leads to an autosomal recessive neurodevelopmental phenotype with a degenerative course, epilepsy and distinct brain anomalies. Brain Commun 2023; 5:fcad222. [PMID: 37794925 PMCID: PMC10546953 DOI: 10.1093/braincomms/fcad222] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2023] [Revised: 06/29/2023] [Accepted: 08/15/2023] [Indexed: 10/06/2023] Open
Abstract
LNPK encodes a conserved membrane protein that stabilizes the junctions of the tubular endoplasmic reticulum network playing crucial roles in diverse biological functions. Recently, homozygous variants in LNPK were shown to cause a neurodevelopmental disorder (OMIM#618090) in four patients displaying developmental delay, epilepsy and nonspecific brain malformations including corpus callosum hypoplasia and variable impairment of cerebellum. We sought to delineate the molecular and phenotypic spectrum of LNPK-related disorder. Exome or genome sequencing was carried out in 11 families. Thorough clinical and neuroradiological evaluation was performed for all the affected individuals, including review of previously reported patients. We identified 12 distinct homozygous loss-of-function variants in 16 individuals presenting with moderate to profound developmental delay, cognitive impairment, regression, refractory epilepsy and a recognizable neuroimaging pattern consisting of corpus callosum hypoplasia and signal alterations of the forceps minor ('ear-of-the-lynx' sign), variably associated with substantia nigra signal alterations, mild brain atrophy, short midbrain and cerebellar hypoplasia/atrophy. In summary, we define the core phenotype of LNPK-related disorder and expand the list of neurological disorders presenting with the 'ear-of-the-lynx' sign suggesting a possible common underlying mechanism related to endoplasmic reticulum-phagy dysfunction.
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Affiliation(s)
- Andrea Accogli
- Division of Medical Genetics, Department of Specialized Medicine, McGill University, Montreal H3G 1A4, Canada
- Department of Human Genetics, McGill University, Montreal, QC H3A 0C7, Canada
| | - Maha S Zaki
- Clinical Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo 12622, Egypt
| | - Mohammed Al-Owain
- Department of Medical Genomics, Center for Genomics Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11211, Saudi Arabia
| | - Mansour Y Otaif
- Department of Pediatric, Neurology Section, Abha Maternity and Childern Hospital, Abha 62521, Saudi Arabia
| | - Adam Jackson
- Division of Evolution, Infection and Genomics, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK
- Manchester Centre for Genomic Medicine, University of Manchester, St Mary’s Hospital, Manchester Academic Health Science Centre, Manchester M13 9WL, UK
| | - Emanuela Argilli
- Department of Neurology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Kate E Chandler
- Division of Evolution, Infection and Genomics, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK
- Manchester Centre for Genomic Medicine, University of Manchester, St Mary’s Hospital, Manchester Academic Health Science Centre, Manchester M13 9WL, UK
| | - Christian G E L De Goede
- Department of Paediatric Neurology, Clinical Research Facility, Lancashire Teaching Hospital NHS Trust, Preston PR2 9HT, UK
| | - Tülün Cora
- Department of Medical Genetics, Selcuk University School of Medicine, Konya 42100, Turkey
| | - Javeria Raza Alvi
- Department of Pediatric Neurology, Institute of Child Health, Children's Hospital, Lahore 54590, Pakistan
| | - Atieh Eslahi
- Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad 917794-8564, Iran
- Student Research Committee, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad 9137-86177, Iran
| | - Mahsa Sadat Asl Mohajeri
- Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad 917794-8564, Iran
| | - Setareh Ashtiani
- Alberta Children’s Hospital Research Institute, Department of Medical Genetics, University of Calgary, Alberta T2N 4Z6, Canada
| | - P Y Billie Au
- Alberta Children’s Hospital Research Institute, Department of Medical Genetics, University of Calgary, Alberta T2N 4Z6, Canada
| | | | | | - Alistair T Pagnamenta
- NIHR Biomedical Research Centre, Wellcome Centre for Human Genetics, University of Oxford, Oxford OX3 7BN, UK
| | - Mehran Beiraghi Toosi
- Pediatric Neurology Department, Mashhad University of Medical Sciences, Mashhad 913791-6847, Iran
- Neuroscience Research Center, Mashhad University of Medical Sciences, Mashhad 91375-33116, Iran
| | - Ehsan Ghayoor Karimiani
- Molecular and Clinical Sciences Institute, St. George’s, University of London, Cranmer Terrace, London SW17 0RE, UK
- Department of Medical Genetics, Next Generation Genetic Polyclinic, Mashhad 91869-51591, Iran
| | - Majid Mojarrad
- Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad 917794-8564, Iran
- Student Research Committee, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad 9137-86177, Iran
- Genetic Center of Khorasan Razavi, Mashhad 91877-53831, Iran
| | - Fatemeh Arab
- Department of Medical Genetics, Faculty of Medicine, Tehran University of Medical Sciences, Tehran 1411713135, Iran
| | - Fahrettin Duymuş
- Department of Medical Genetics, Selcuk University School of Medicine, Konya 42100, Turkey
- Department of Medical Genetics, Konya City Hospital, Konya 42020, Turkey
| | - Morris H Scantlebury
- Departments of Pediatrics and Clinical Neuroscience, University of Calgary; Alberta Children’s Hospital Research Institute, Hotchkiss Brain Institute & Owerko Center, University of Calgary, Alberta T2N 4N1, Canada
| | - Gözde Yeşil
- Department of Medical Genetics, Istanbul Medical Faculty, Istanbul University, Istanbul 34093, Turkey
| | - Jill Anne Rosenfeld
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
- Baylor Genetics Laboratories, Houston, TX 77021, USA
| | - Ayberk Türkyılmaz
- Department of Medical Genetics, Karadeniz Technical University Faculty of Medicine, Trabzon 61080, Turkey
| | - Safiye Güneş Sağer
- Clinics of Pediatric Neurology, Kartal Dr. Lütfi Kırdar City Hospital, İstanbul 34890, Turkey
| | - Tipu Sultan
- Department of Pediatric Neurology, Institute of Child Health, Children's Hospital, Lahore 54590, Pakistan
| | - Farah Ashrafzadeh
- Pediatric Neurology Department, Mashhad University of Medical Sciences, Mashhad 913791-6847, Iran
| | - Tatheer Zahra
- Department of Developmental-Behavioral Pediatrics, University of Child Health Sciences, The Children’s Hospital, Lahore 54590, Pakistan
| | - Fatima Rahman
- Department of Developmental-Behavioral Pediatrics, University of Child Health Sciences, The Children’s Hospital, Lahore 54590, Pakistan
| | - Shazia Maqbool
- Department of Developmental-Behavioral Pediatrics, University of Child Health Sciences, The Children’s Hospital, Lahore 54590, Pakistan
| | - Mohamed S Abdel-Hamid
- Medical Molecular Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo 12622, Egypt
| | - Mahmoud Y Issa
- Clinical Genetics Department, Human Genetics and Genome Research Institute, National Research Centre, Cairo 12622, Egypt
| | - Stephanie Efthymiou
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | | | | | - Vincenzo Salpietro
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK
- Department of Biotechnological and Applied Clinical Sciences, University of L’Aquila, L’Aquila 67100, Italy
| | - Zuhair Al-Hassnan
- Department of Medical Genomics, Center for Genomics Medicine, King Faisal Specialist Hospital and Research Center, Riyadh 11211, Saudi Arabia
- College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia
| | - Siddharth Banka
- Division of Evolution, Infection and Genomics, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester M13 9PT, UK
- Manchester Centre for Genomic Medicine, University of Manchester, St Mary’s Hospital, Manchester Academic Health Science Centre, Manchester M13 9WL, UK
| | - Elliot H Sherr
- Department of Neurology, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Joseph G Gleeson
- Department of Neurosciences, University of California, San Diego, La Jolla 92093, USA
- Rady Children’s Institute for Genomic Medicine, San Diego 92123, USA
| | - Pasquale Striano
- Department of Neurosciences Rehabilitation, Ophthalmology, Genetics, Maternal and Child Health (DiNOGMI), University of Genoa, Genoa 16132, Italy
- Pediatric Neurology and Muscular Diseases Unit, IRCCS Istituto ‘Giannina Gaslini’, Genoa 16147, Italy
| | - Henry Houlden
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | | | - Reza Maroofian
- Department of Neuromuscular Diseases, UCL Queen Square Institute of Neurology, Queen Square, London WC1N 3BG, UK
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7
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Choi H, Liao YC, Yoon YJ, Grimm J, Lavis LD, Singer RH, Lippincott-Schwartz J. Lysosomal release of amino acids at ER three-way junctions regulates transmembrane and secretory protein mRNA translation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.01.551382. [PMID: 37577585 PMCID: PMC10418176 DOI: 10.1101/2023.08.01.551382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/15/2023]
Abstract
One-third of the mammalian proteome is comprised of transmembrane and secretory proteins that are synthesized on endoplasmic reticulum (ER). Here, we investigate the spatial distribution and regulation of mRNAs encoding these membrane and secretory proteins (termed "secretome" mRNAs) through live cell, single molecule tracking to directly monitor the position and translation states of secretome mRNAs on ER and their relationship to other organelles. Notably, translation of secretome mRNAs occurred preferentially near lysosomes on ER marked by the ER junction-associated protein, Lunapark. Knockdown of Lunapark reduced the extent of secretome mRNA translation without affecting translation of other mRNAs. Less secretome mRNA translation also occurred when lysosome function was perturbed by raising lysosomal pH or inhibiting lysosomal proteases. Secretome mRNA translation near lysosomes was enhanced during amino acid deprivation. Addition of the integrated stress response inhibitor, ISRIB, reversed the translation inhibition seen in Lunapark knockdown cells, implying an eIF2 dependency. Altogether, these findings uncover a novel coordination between ER and lysosomes, in which local release of amino acids and other factors from ER-associated lysosomes patterns and regulates translation of mRNAs encoding secretory and membrane proteins.
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8
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Jung M, Jung G, Schmid F. Stability of Branched Tubular Membrane Structures. PHYSICAL REVIEW LETTERS 2023; 130:148401. [PMID: 37084449 DOI: 10.1103/physrevlett.130.148401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2022] [Accepted: 02/15/2023] [Indexed: 05/03/2023]
Abstract
We study the energetics and stability of branched tubular membrane structures by computer simulations of a triangulated network model. We find that triple (Y) junctions can be created and stabilized by applying mechanical forces, if the angle between branches is 120°. The same holds for tetrahedral junctions with tetraeder angles. If the wrong angles are enforced, the branches coalesce to a linear structure, a pure tube. After releasing the mechanical force, Y-branched structures remain metastable if one constrains the enclosed volume and the average curvature (the area difference) to a fixed value; tetrahedral junctions however split up into two Y junctions. Somewhat counterintuitively, the energy cost of adding a Y branch is negative in structures with fixed surface area and tube diameter, even if one accounts for the positive contribution of the additional branch end. For fixed average curvature, however, adding a branch also enforces a thinning of tubes, therefore the overall curvature energy cost is positive. Possible implications for the stability of branched networks structures in cells are discussed.
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Affiliation(s)
- Maike Jung
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 9, 55128 Mainz, Germany
| | - Gerhard Jung
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, 34095 Montpellier, France
| | - Friederike Schmid
- Institut für Physik, Johannes Gutenberg-Universität Mainz, Staudingerweg 9, 55128 Mainz, Germany
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9
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Fuentes LA, Marin Z, Tyson J, Baddeley D, Bewersdorf J. The nanoscale organization of reticulon 4 shapes local endoplasmic reticulum structure in situ. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.26.525608. [PMID: 36747764 PMCID: PMC9900957 DOI: 10.1101/2023.01.26.525608] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
UNLABELLED The endoplasmic reticulum’s (ER) structure is directly linked to the many functions of the ER but its formation is not fully understood. We investigate how the ER-membrane curving protein reticulon 4 (Rtn4) localizes to and organizes in the membrane and how that affects local ER structure. We show a strong correlation between the local Rtn4 density and the local ER membrane curvature. Our data further reveal that the typical ER tubule possesses an elliptical cross-section with Rtn4 enriched at either end of the major axis. Rtn4 oligomers are linear-shaped, contain about five copies of the protein, and preferentially orient parallel to the tubule axis. Our observations support a mechanism in which oligomerization leads to an increase of the local Rtn4 concentration with each molecule increasing membrane curvature through a hairpin wedging mechanism. This quantitative analysis of Rtn4 and its effects on the ER membrane result in a new model of tubule shape as it relates to Rtn4. SUMMARY Rtn4 forms linear-shaped oligomers that contain an average of five Rtn4 proteins, localize to the sides of elliptical tubules, prefer orientations near parallel to the tubule axis, and increase local curvature of the ER membrane by increasing local Rtn4 density.
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Affiliation(s)
- Lukas A. Fuentes
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
| | - Zach Marin
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Jonathan Tyson
- Department of Chemistry, Yale University, New Haven, CT, USA
| | - David Baddeley
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Joerg Bewersdorf
- Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA
- Department of Biomedical Engineering, Yale University, New Haven, CT, USA
- Department of Physics, Yale University, New Haven, CT, USA
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10
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Sandoz PA, Denhardt-Eriksson RA, Abrami L, Abriata LA, Spreemann G, Maclachlan C, Ho S, Kunz B, Hess K, Knott G, S Mesquita F, Hatzimanikatis V, van der Goot FG. Dynamics of CLIMP-63 S-acylation control ER morphology. Nat Commun 2023; 14:264. [PMID: 36650170 PMCID: PMC9844198 DOI: 10.1038/s41467-023-35921-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 01/06/2023] [Indexed: 01/19/2023] Open
Abstract
The complex architecture of the endoplasmic reticulum (ER) comprises distinct dynamic features, many at the nanoscale, that enable the coexistence of the nuclear envelope, regions of dense sheets and a branched tubular network that spans the cytoplasm. A key player in the formation of ER sheets is cytoskeleton-linking membrane protein 63 (CLIMP-63). The mechanisms by which CLIMP-63 coordinates ER structure remain elusive. Here, we address the impact of S-acylation, a reversible post-translational lipid modification, on CLIMP-63 cellular distribution and function. Combining native mass-spectrometry, with kinetic analysis of acylation and deacylation, and data-driven mathematical modelling, we obtain in-depth understanding of the CLIMP-63 life cycle. In the ER, it assembles into trimeric units. These occasionally exit the ER to reach the plasma membrane. However, the majority undergoes S-acylation by ZDHHC6 in the ER where they further assemble into highly stable super-complexes. Using super-resolution microscopy and focused ion beam electron microscopy, we show that CLIMP-63 acylation-deacylation controls the abundance and fenestration of ER sheets. Overall, this study uncovers a dynamic lipid post-translational regulation of ER architecture.
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Affiliation(s)
- Patrick A Sandoz
- Global Health Institute, School of Life Sciences, EPFL, Lausanne, Switzerland
| | | | - Laurence Abrami
- Global Health Institute, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - Luciano A Abriata
- Laboratory for Biomolecular Modelling, Institute of Bioengineering, EPFL and Swiss Institute of Bioinformatics, Lausanne, Switzerland.,Protein Production and Structure Core Facility, School of Life Sciences, EPFL, Lausanne, Switzerland
| | | | | | - Sylvia Ho
- Global Health Institute, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - Béatrice Kunz
- Global Health Institute, School of Life Sciences, EPFL, Lausanne, Switzerland
| | - Kathryn Hess
- Brain Mind Institute, EPFL, Lausanne, Switzerland
| | - Graham Knott
- BioEM Facility, School of Life Sciences, EPFL, Lausanne, Switzerland
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11
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Kozlov MM, Taraska JW. Generation of nanoscopic membrane curvature for membrane trafficking. Nat Rev Mol Cell Biol 2023; 24:63-78. [PMID: 35918535 DOI: 10.1038/s41580-022-00511-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2022] [Indexed: 11/09/2022]
Abstract
Curved membranes are key features of intracellular organelles, and their generation involves dynamic protein complexes. Here we describe the fundamental mechanisms such as the hydrophobic insertion, scaffolding and crowding mechanisms these proteins use to produce membrane curvatures and complex shapes required to form intracellular organelles and vesicular structures involved in endocytosis and secretion. For each mechanism, we discuss its cellular functions as well as the underlying physical principles and the specific membrane properties required for the mechanism to be feasible. We propose that the integration of individual mechanisms into a highly controlled, robust process of curvature generation often relies on the assembly of proteins into coats. How cells unify and organize the curvature-generating factors at the nanoscale is presented for three ubiquitous coats central for membrane trafficking in eukaryotes: clathrin-coated pits, caveolae, and COPI and COPII coats. The emerging theme is that these coats arrange and coordinate curvature-generating factors in time and space to dynamically shape membranes to accomplish membrane trafficking within cells.
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Affiliation(s)
- Michael M Kozlov
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel.
| | - Justin W Taraska
- Biochemistry and Biophysics Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA.
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12
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Suhda S, Yamamoto Y, Wisesa S, Sada R, Sakisaka T. The 14-3-3γ isoform binds to and regulates the localization of endoplasmic reticulum (ER) membrane protein TMCC3 for the reticular network of the ER. J Biol Chem 2022; 299:102813. [PMID: 36549645 PMCID: PMC9860497 DOI: 10.1016/j.jbc.2022.102813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 12/07/2022] [Accepted: 12/09/2022] [Indexed: 12/24/2022] Open
Abstract
The reticular network of the endoplasmic reticulum (ER) is formed by connecting ER tubules through three-way junctions and undergoes constant remodeling through formation and loss of the three-way junctions. Transmembrane and coiled-coil domain family 3 (TMCC3), an ER membrane protein localizing at three-way junctions, has been shown to positively regulate formation of the reticular ER network. However, elements that negatively regulate TMCC3 localization have not been characterized. In this study, we report that 14-3-3γ, a phospho-serine/phospho-threonine-binding protein involved in various signal transduction pathways, is a negative regulator of TMCC3. We demonstrate that overexpression of 14-3-3γ reduced localization of TMCC3 to three-way junctions and decreased the number of three-way junctions. TMCC3 bound to 14-3-3γ through the N terminus and had deduced 14-3-3 binding motifs. Additionally, we determined that a TMCC3 mutant substituting alanine for serine to be phosphorylated in the binding motif reduced binding to 14-3-3γ. The TMCC3 mutant was more prone than wildtype TMCC3 to localize at three-way junctions in the cells overexpressing 14-3-3γ. Furthermore, the TMCC3 mutant rescued the ER sheet expansion caused by TMCC3 knockdown less than wild-type TMCC3. Taken together, these results indicate that 14-3-3γ binding negatively regulates localization of TMCC3 to the three-way junctions for the proper reticular ER network, implying that the negative regulation of TMCC3 by 14-3-3γ would underlie remodeling of the reticular network of the ER.
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Affiliation(s)
- Saihas Suhda
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University School of Medicine, Kobe, Japan
| | - Yasunori Yamamoto
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University School of Medicine, Kobe, Japan
| | - Sindhu Wisesa
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University School of Medicine, Kobe, Japan
| | - Risa Sada
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University School of Medicine, Kobe, Japan
| | - Toshiaki Sakisaka
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University School of Medicine, Kobe, Japan.
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13
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Jang W, Puchkov D, Samsó P, Liang Y, Nadler-Holly M, Sigrist SJ, Kintscher U, Liu F, Mamchaoui K, Mouly V, Haucke V. Endosomal lipid signaling reshapes the endoplasmic reticulum to control mitochondrial function. Science 2022; 378:eabq5209. [PMID: 36520888 DOI: 10.1126/science.abq5209] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Cells respond to fluctuating nutrient supply by adaptive changes in organelle dynamics and in metabolism. How such changes are orchestrated on a cell-wide scale is unknown. We show that endosomal signaling lipid turnover by MTM1, a phosphatidylinositol 3-phosphate [PI(3)P] 3-phosphatase mutated in X-linked centronuclear myopathy in humans, controls mitochondrial morphology and function by reshaping the endoplasmic reticulum (ER). Starvation-induced endosomal recruitment of MTM1 impairs PI(3)P-dependent contact formation between tubular ER membranes and early endosomes, resulting in the conversion of ER tubules into sheets, the inhibition of mitochondrial fission, and sustained oxidative metabolism. Our results unravel an important role for early endosomal lipid signaling in controlling ER shape and, thereby, mitochondrial form and function to enable cells to adapt to fluctuating nutrient environments.
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Affiliation(s)
- Wonyul Jang
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Dmytro Puchkov
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Paula Samsó
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - YongTian Liang
- Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, 14195 Berlin, Germany
| | - Michal Nadler-Holly
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany
| | - Stephan J Sigrist
- Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, 14195 Berlin, Germany
| | | | - Fan Liu
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany.,Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
| | - Kamel Mamchaoui
- Centre de Recherche en Myologie, Institut de Myologie, Inserm, Sorbonne Université, 75013 Paris, France
| | - Vincent Mouly
- Centre de Recherche en Myologie, Institut de Myologie, Inserm, Sorbonne Université, 75013 Paris, France
| | - Volker Haucke
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie (FMP), 13125 Berlin, Germany.,Department of Biology, Chemistry, and Pharmacy, Freie Universität Berlin, 14195 Berlin, Germany.,Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany
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14
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Kontou A, Herman EK, Field MC, Dacks JB, Koumandou VL. Evolution of factors shaping the endoplasmic reticulum. Traffic 2022; 23:462-473. [PMID: 36040076 PMCID: PMC9804665 DOI: 10.1111/tra.12863] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2022] [Revised: 06/30/2022] [Accepted: 07/24/2022] [Indexed: 01/09/2023]
Abstract
Endomembrane system compartments are significant elements in virtually all eukaryotic cells, supporting functions including protein synthesis, post-translational modifications and protein/lipid targeting. In terms of membrane area the endoplasmic reticulum (ER) is the largest intracellular organelle, but the origins of proteins defining the organelle and the nature of lineage-specific modifications remain poorly studied. To understand the evolution of factors mediating ER morphology and function we report a comparative genomics analysis of experimentally characterized ER-associated proteins involved in maintaining ER structure. We find that reticulons, REEPs, atlastins, Ufe1p, Use1p, Dsl1p, TBC1D20, Yip3p and VAPs are highly conserved, suggesting an origin at least as early as the last eukaryotic common ancestor (LECA), although many of these proteins possess additional non-ER functions in modern eukaryotes. Secondary losses are common in individual species and in certain lineages, for example lunapark is missing from the Stramenopiles and the Alveolata. Lineage-specific innovations include protrudin, Caspr1, Arl6IP1, p180, NogoR, kinectin and CLIMP-63, which are restricted to the Opisthokonta. Hence, much of the machinery required to build and maintain the ER predates the LECA, but alternative strategies for the maintenance and elaboration of ER shape and function are present in modern eukaryotes. Moreover, experimental investigations for ER maintenance factors in diverse eukaryotes are expected to uncover novel mechanisms.
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Affiliation(s)
- Aspasia Kontou
- Genetics Laboratory, Department of BiotechnologyAgricultural University of AthensAthensGreece
| | - Emily K. Herman
- Division of Infectious Diseases, Department of MedicineUniversity of AlbertaEdmontonAlbertaCanada,Present address:
Department of Agricultural, Food and Nutritional Science, Faculty of Agricultural, Life and Environmental SciencesUniversity of AlbertaEdmontonAlbertaCanada
| | - Mark C. Field
- School of Life SciencesUniversity of DundeeDundeeUK,Biology CentreCzech Academy of SciencesČeské BudějoviceCzech Republic
| | - Joel B. Dacks
- Division of Infectious Diseases, Department of MedicineUniversity of AlbertaEdmontonAlbertaCanada,Biology CentreCzech Academy of SciencesČeské BudějoviceCzech Republic,Centre for Life's Origin and Evolution, Department of Genetics, Evolution and EnvironmentUniversity College of LondonLondonUK
| | - V. Lila Koumandou
- Genetics Laboratory, Department of BiotechnologyAgricultural University of AthensAthensGreece
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15
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Anggrandariyanny PC, Kajiho H, Yamamoto Y, Sakisaka T. Lunapark ubiquitinates atlastin-2 for the tubular network formation of the endoplasmic reticulum. J Biochem 2022; 172:245-257. [PMID: 35894092 DOI: 10.1093/jb/mvac060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2022] [Accepted: 07/11/2022] [Indexed: 11/14/2022] Open
Abstract
Endoplasmic reticulum (ER) tubules are interconnected by three-way junctions, resulting in the formation of a tubular ER network. Lunapark (Lnp) localizes to and stabilizes the three-way junctions. The N-terminal cytoplasmic domain in Lnp has a ubiquitin ligase activity. However, the molecular mechanism of how the ubiquitin ligase activity of Lnp is involved in the formation of the tubular ER network remains unknown. In this study, we examined whether the ER membrane proteins responsible for the formation of the tubular ER network are ubiquitinated by Lnp. We found that atlastin-2 (ATL2), an isoform of the ATL family mediating the generation of the three-way junctions by connecting the ER tubules, is a novel substrate for ubiquitination by Lnp. The localization of Lnp at the three-way junctions is important for ubiquitination of ATL2. Lysine 56, 57, 282, and 302 are the potential ubiquitination sites by Lnp. Silencing ATL2 decreased the number of the three-way junctions, and the expression of the ATL2 mutant in which the lysine residues are substituted with arginine failed to rescue the decrease of the three-way junctions in the ATL2 knocked-down cells. These results suggest that Lnp ubiquitinates ATL2 at the three-way junctions for the proper tubular ER network formation.
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Affiliation(s)
- Putri Chynthia Anggrandariyanny
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, 650-0017, Japan
| | - Hiroaki Kajiho
- Division of Membrane Dynamics, Department of Physiology and Cell Biology, Kobe University Graduate School of Medicine, Kobe, 650-0017, Japan
| | - 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
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16
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Lastun VL, Levet C, Freeman M. The mammalian rhomboid protein RHBDL4 protects against endoplasmic reticulum stress by regulating the morphology and distribution of ER sheets. J Biol Chem 2022; 298:101935. [PMID: 35436469 PMCID: PMC9136127 DOI: 10.1016/j.jbc.2022.101935] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 03/24/2022] [Accepted: 03/28/2022] [Indexed: 11/16/2022] Open
Abstract
In metazoans, the architecture of the endoplasmic reticulum (ER) differs between cell types and undergoes major changes throughout the cell cycle and according to physiological needs. Although much is known about how the different ER morphologies are generated and maintained, especially ER tubules, how context-dependent changes in ER shape and distribution are regulated and the factors involved are less well characterized, as are the factors that contribute to the positioning of the ER within the cell. By overexpression and KO experiments, we show that the levels of RHBDL4, an ER-resident rhomboid protease, modulate the shape and distribution of the ER, especially during conditions that require rapid changes in the ER sheet distribution, such as ER stress. We demonstrate that RHBDL4 interacts with cytoskeleton-linking membrane protein 63 (CLIMP-63), a protein involved in ER sheet stabilization, as well as with the cytoskeleton. Furthermore, we found that mice lacking RHBDL4 are sensitive to ER stress and develop liver steatosis, a phenotype associated with unresolved ER stress. Taken together, these data suggest a new physiological role for RHBDL4 and also imply that this function does not require its enzymatic activity.
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17
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Türkyılmaz A, Sağer SG, Günbey HP, Akın Y. Novel LNPK variant causes progressive cerebral atrophy: Expanding the clinical phenotype. Clin Genet 2022; 102:218-222. [PMID: 35599435 DOI: 10.1111/cge.14166] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2022] [Revised: 05/09/2022] [Accepted: 05/18/2022] [Indexed: 11/30/2022]
Abstract
The biallelic variations of the LNPK gene are associated with the "neurodevelopmental disorder with epilepsy and hypoplasia of the corpus callosum" phenotype [MIM:618090] in the Online Mendelian Inheritance In Men database, and so far, two families have been identified in the literature. A third family with novel clinical features, who bears a novel variant in LNPK (NM_030650.3: c.770delA, p.D257fs*31) is described in the present study. The coexistence of psychomotor regression and neurodegeneration in brain magnetic resonance imaging was found for the first time in the present study, thanks to the long-term follow-up data on the case, which contributed to the phenotypic and mutation spectrum by means of the novel variation.
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Affiliation(s)
- Ayberk Türkyılmaz
- Department of Medical Genetics, Karadeniz Technical University Faculty of Medicine, Trabzon, Turkey
| | - Safiye Güneş Sağer
- Department of Pediatric Neurology, Kartal Dr. Lütfi Kırdar City Hospital, İstanbul, Turkey
| | - Hediye Pınar Günbey
- Department of Radiology, Kartal Dr. Lütfi Kırdar City Hospital, İstanbul, Turkey
| | - Yasemin Akın
- Department of Pediatrics, Kartal Dr. Lütfi Kırdar City Hospital, İstanbul, Turkey
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18
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The endoplasmic reticulum adopts two distinct tubule forms. Proc Natl Acad Sci U S A 2022; 119:e2117559119. [PMID: 35471903 PMCID: PMC9170160 DOI: 10.1073/pnas.2117559119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The endoplasmic reticulum (ER) is one of the most structurally visible and functionally important organelles in the cell. Utilizing superresolution microscopy, we here unveil that in the mammalian cell, the peripheral ER adopts two distinct, well-defined tubule forms of contrasting structures, molecular signatures, and functions, with one of the two curiously being ribbon-like, ultranarrow sheets of fixed widths. With fast multicolor microscopy, we further show how the two tubule forms dynamically interconvert while differentially accommodating proteins in the living cell. The endoplasmic reticulum (ER) is a versatile organelle with diverse functions. Through superresolution microscopy, we show that the peripheral ER in the mammalian cell adopts two distinct forms of tubules. Whereas an ultrathin form, R1, is consistently covered by ER-membrane curvature-promoting proteins, for example, Rtn4 in the native cell, in the second form, R2, Rtn4 and analogs are arranged into two parallel lines at a conserved separation of ∼105 nm over long ranges. The two tubule forms together account for ∼90% of the total tubule length in the cell, with either one being dominant in different cell types. The R1–R2 dichotomy and the final tubule geometry are both coregulated by Rtn4 (and analogs) and the ER sheet–maintaining protein Climp63, which, respectively, define the edge curvature and lumen height of the R2 tubules to generate a ribbon-like structure of well-defined width. Accordingly, the R2 tubule width correlates positively with the Climp63 intraluminal size. The R1 and R2 tubules undergo active remodeling at the second/subsecond timescales as they differently accommodate proteins, with the former effectively excluding ER-luminal proteins and ER-membrane proteins with large intraluminal domains. We thus uncover a dynamic structural dichotomy for ER tubules with intriguing functional implications.
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19
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A role for endoplasmic reticulum dynamics in the cellular distribution of microtubules. Proc Natl Acad Sci U S A 2022; 119:e2104309119. [PMID: 35377783 PMCID: PMC9169640 DOI: 10.1073/pnas.2104309119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
The endoplasmic reticulum (ER) and the microtubule (MT) cytoskeleton form a coextensive, dynamic system that pervades eukaryotic cells. The shape of the ER is generated by a set of evolutionarily conserved membrane proteins that are able to control ER morphology and dynamics independently of MTs. Here we uncover that the molecular machinery that determines ER network dynamics can influence the subcellular distribution of MTs. We show that active control of local ER tubule junction density by ER tethering and fusion is important for the spatial organization of the combined ER–MT system. Our work suggests that cells might alter ER junction dynamics to drive formation of MT bundles, which are important structures, e.g., in migrating cells or in neuronal axons. The dynamic distribution of the microtubule (MT) cytoskeleton is crucial for the shape, motility, and internal organization of eukaryotic cells. However, the basic principles that control the subcellular position of MTs in mammalian interphase cells remain largely unknown. Here we show by a combination of microscopy and computational modeling that the dynamics of the endoplasmic reticulum (ER) plays an important role in distributing MTs in the cell. Specifically, our physics-based model of the ER–MT system reveals that spatial inhomogeneity in the density of ER tubule junctions results in an overall contractile force that acts on MTs and influences their distribution. At steady state, cells rapidly compensate for local variability of ER junction density by dynamic formation, release, and movement of ER junctions across the ER. Perturbation of ER junction tethering and fusion by depleting the ER fusogens called atlastins disrupts the dynamics of junction equilibration, rendering the ER–MT system unstable and causing the formation of MT bundles. Our study points to a mechanical role of ER dynamics in cellular organization and suggests a mechanism by which cells might dynamically regulate MT distribution in, e.g., motile cells or in the formation and maintenance of neuronal axons.
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20
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Jawaid MZ, Sinclair R, Bulone V, Cox DL, Drakakaki G. A biophysical model for plant cell plate maturation based on the contribution of a spreading force. PLANT PHYSIOLOGY 2022; 188:795-806. [PMID: 34850202 PMCID: PMC8825336 DOI: 10.1093/plphys/kiab552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/13/2021] [Accepted: 10/27/2021] [Indexed: 06/13/2023]
Abstract
Plant cytokinesis, a fundamental process of plant life, involves de novo formation of a "cell plate" partitioning the cytoplasm of dividing cells. Cell plate formation is directed by orchestrated delivery, fusion of cytokinetic vesicles, and membrane maturation to form a nascent cell wall by timely deposition of polysaccharides. During cell plate maturation, the fragile membrane network transitions to a fenestrated sheet and finally a young cell wall. Here, we approximated cell plate sub-structures with testable shapes and adopted the Helfrich-free energy model for membranes, including a stabilizing and spreading force, to understand the transition from a vesicular network to a fenestrated sheet and mature cell plate. Regular cell plate development in the model was possible, with suitable bending modulus, for a two-dimensional late stage spreading force of 2-6 pN/nm, an osmotic pressure difference of 2-10 kPa, and spontaneous curvature between 0 and 0.04 nm-1. With these conditions, stable membrane conformation sizes and morphologies emerged in concordance with stages of cell plate development. To reach a mature cell plate, our model required the late-stage onset of a spreading/stabilizing force coupled with a concurrent loss of spontaneous curvature. Absence of a spreading/stabilizing force predicts failure of maturation. The proposed model provides a framework to interrogate different players in late cytokinesis and potentially other membrane networks that undergo such transitions. Callose, is a polysaccharide that accumulates transiently during cell plate maturation. Callose-related observations were consistent with the proposed model's concept, suggesting that it is one of the factors involved in establishing the spreading force.
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Affiliation(s)
- Muhammad Zaki Jawaid
- Department of Physics and Astronomy, University of California, Davis, California, USA
| | - Rosalie Sinclair
- Department of Plant Sciences, University of California, Davis, California, USA
| | - Vincent Bulone
- School of Food, Agriculture and Wine, The University of Adelaide, Waite Campus, Adelaide SA 5064, Australia
- Department of Chemistry, Division of Glycoscience, KTH Royal Institute of Technology, Stockholm, Sweden
| | - Daniel L Cox
- Department of Physics and Astronomy, University of California, Davis, California, USA
| | - Georgia Drakakaki
- Department of Plant Sciences, University of California, Davis, California, USA
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21
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Kang BH, Anderson CT, Arimura SI, Bayer E, Bezanilla M, Botella MA, Brandizzi F, Burch-Smith TM, Chapman KD, Dünser K, Gu Y, Jaillais Y, Kirchhoff H, Otegui MS, Rosado A, Tang Y, Kleine-Vehn J, Wang P, Zolman BK. A glossary of plant cell structures: Current insights and future questions. THE PLANT CELL 2022; 34:10-52. [PMID: 34633455 PMCID: PMC8846186 DOI: 10.1093/plcell/koab247] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 09/29/2021] [Indexed: 05/03/2023]
Abstract
In this glossary of plant cell structures, we asked experts to summarize a present-day view of plant organelles and structures, including a discussion of outstanding questions. In the following short reviews, the authors discuss the complexities of the plant cell endomembrane system, exciting connections between organelles, novel insights into peroxisome structure and function, dynamics of mitochondria, and the mysteries that need to be unlocked from the plant cell wall. These discussions are focused through a lens of new microscopy techniques. Advanced imaging has uncovered unexpected shapes, dynamics, and intricate membrane formations. With a continued focus in the next decade, these imaging modalities coupled with functional studies are sure to begin to unravel mysteries of the plant cell.
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Affiliation(s)
- Byung-Ho Kang
- School of Life Sciences, Centre for Cell & Developmental Biology and State Key Laboratory of Agrobiotechnology, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Charles T Anderson
- Department of Biology and Center for Lignocellulose Structure and Formation, The Pennsylvania State University, University Park, Pennsylvania 16802 USA
| | - Shin-ichi Arimura
- Graduate School of Agricultural and Life Sciences, University of Tokyo, Tokyo, Japan
| | - Emmanuelle Bayer
- Université de Bordeaux, CNRS, Laboratoire de Biogenèse Membranaire, UMR 5200, Villenave d'Ornon F-33140, France
| | - Magdalena Bezanilla
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755, USA
| | - Miguel A Botella
- Departamento de Biología Molecular y Bioquímica, Instituto de Hortifruticultura Subtropical y Mediterránea “La Mayora,” Universidad de Málaga-Consejo Superior de Investigaciones Científicas (IHSM-UMA-CSIC), Universidad de Málaga, Málaga 29071, Spain
| | - Federica Brandizzi
- MSU-DOE Plant Research Lab, Michigan State University, East Lansing, Michigan 48824 USA
- Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA
- Great Lakes Bioenergy Research Center, Michigan State University, East Lansing, Michigan 48824, USA
| | - Tessa M Burch-Smith
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996, USA
| | - Kent D Chapman
- BioDiscovery Institute and Department of Biological Sciences, University of North Texas, Denton, Texas 76203, USA
| | - Kai Dünser
- Faculty of Biology, Chair of Molecular Plant Physiology (MoPP) University of Freiburg, Freiburg 79104, Germany
- Center for Integrative Biological Signalling Studies (CIBSS), University of Freiburg, Freiburg 79104, Germany
| | - Yangnan Gu
- Department of Plant and Microbial Biology, Innovative Genomics Institute, University of California, Berkeley, California 94720, USA
| | - Yvon Jaillais
- Laboratoire Reproduction et Développement des Plantes (RDP), Université de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRAE, Lyon, France
| | - Helmut Kirchhoff
- Institute of Biological Chemistry, Washington State University, Pullman, Washington 99164, USA
| | - Marisa S Otegui
- Department of Botany and Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Wisconsin 53706, USA
| | - Abel Rosado
- Department of Botany, University of British Columbia, Vancouver V6T1Z4, Canada
| | - Yu Tang
- Department of Plant and Microbial Biology, Innovative Genomics Institute, University of California, Berkeley, California 94720, USA
| | - Jürgen Kleine-Vehn
- Faculty of Biology, Chair of Molecular Plant Physiology (MoPP) University of Freiburg, Freiburg 79104, Germany
- Center for Integrative Biological Signalling Studies (CIBSS), University of Freiburg, Freiburg 79104, Germany
| | - Pengwei Wang
- Key Laboratory of Horticultural Plant Biology (MOE), College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan 430070, China
| | - Bethany Karlin Zolman
- Department of Biology, University of Missouri, St. Louis, St. Louis, Missouri 63121, USA
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22
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Haimov E, Urbakh M, Kozlov MM. Negative tension controls stability and structure of intermediate filament networks. Sci Rep 2022; 12:16. [PMID: 34996899 PMCID: PMC8741771 DOI: 10.1038/s41598-021-02536-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 11/11/2021] [Indexed: 11/17/2022] Open
Abstract
Networks, whose junctions are free to move along the edges, such as two-dimensional soap froths and membrane tubular networks of endoplasmic reticulum are intrinsically unstable. This instability is a result of a positive tension applied to the network elements. A paradigm of networks exhibiting stable polygonal configurations in spite of the junction mobility, are networks formed by bundles of Keratin Intermediate Filaments (KIFs) in live cells. A unique feature of KIF networks is a, hypothetically, negative tension generated in the network bundles due to an exchange of material between the network and an effective reservoir of unbundled filaments. Here we analyze the structure and stability of two-dimensional networks with mobile three-way junctions subject to negative tension. First, we analytically examine a simplified case of hexagonal networks with symmetric junctions and demonstrate that, indeed, a negative tension is mandatory for the network stability. Another factor contributing to the network stability is the junction elastic resistance to deviations from the symmetric state. We derive an equation for the optimal density of such networks resulting from an interplay between the tension and the junction energy. We describe a configurational degeneration of the optimal energy state of the network. Further, we analyze by numerical simulations the energy of randomly generated networks with, generally, asymmetric junctions, and demonstrate that the global minimum of the network energy corresponds to the irregular configurations.
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Affiliation(s)
- Ehud Haimov
- School of Physics and Astronomy, Raymond and Beverley Sackler Faculty of Exact Sciences, Tel-Aviv University, 69978, Tel-Aviv, Israel
| | - Michael Urbakh
- School of Chemistry, Raymond and Beverley Sackler Faculty of Exact Sciences, Tel-Aviv University, 69978, Tel-Aviv, Israel.
| | - Michael M Kozlov
- Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel-Aviv University, 69978, Tel-Aviv, Israel.
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23
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Pereira C, Di Sansebastiano GP. Mechanisms of membrane traffic in plant cells. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2021; 169:102-111. [PMID: 34775176 DOI: 10.1016/j.plaphy.2021.11.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Revised: 10/31/2021] [Accepted: 11/02/2021] [Indexed: 06/13/2023]
Abstract
The organelles of the secretory pathway are characterized by specific organization and function but they communicate in different ways with intense functional crosstalk. The best known membrane-bound transport carriers are known as protein-coated vesicles. Other traffic mechanisms, despite the intense investigations, still show incongruences. The review intends to provide a general view of the mechanisms involved in membrane traffic. We evidence that organelles' biogenesis involves mechanisms that actively operate during the entire cell cycle and the persistent interconnections between the Endoplasmic reticulum (ER), Golgi apparatus, trans-Golgi network (TGN) and endosomes, the vacuolar complex and the plasma membrane (PM) may be seen as a very dynamic membrane network in which vesicular traffic is part of a general maturation process.
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Affiliation(s)
- Cláudia Pereira
- GreenUPorto-Sustainable Agrifood Production Research Centre & Department of Biology, Faculty of Sciences, University of Porto, Rua Do Campo Alegre, S/nº, 4169-007, Porto, Portugal.
| | - Gian Pietro Di Sansebastiano
- Department of Biological and Environmental Sciences and Technologies (DISTEBA), University of Salento, Campus ECOTEKNE, 73100, Lecce, Italy.
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24
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Tran NH, Carter SD, De Mazière A, Ashkenazi A, Klumperman J, Walter P, Jensen GJ. The stress-sensing domain of activated IRE1α forms helical filaments in narrow ER membrane tubes. Science 2021; 374:52-57. [PMID: 34591618 PMCID: PMC9041316 DOI: 10.1126/science.abh2474] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The signaling network of the unfolded protein response (UPR) adjusts the protein-folding capacity of the endoplasmic reticulum (ER) according to need. The most conserved UPR sensor, IRE1α, spans the ER membrane and activates through oligomerization. IRE1α oligomers accumulate in dynamic foci. We determined the in situ structure of IRE1α foci by cryogenic correlated light and electron microscopy combined with electron cryo-tomography and complementary immuno–electron microscopy in mammalian cell lines. IRE1α foci localized to a network of narrow anastomosing ER tubes (diameter, ~28 nm) with complex branching. The lumen of the tubes contained protein filaments, which were likely composed of arrays of IRE1α lumenal domain dimers that were arranged in two intertwined, left-handed helices. This specialized ER subdomain may play a role in modulating IRE1α signaling.
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Affiliation(s)
- Ngoc-Han Tran
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
| | - Stephen D. Carter
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
| | - Ann De Mazière
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, Netherlands
| | - Avi Ashkenazi
- Cancer Immunology, Genentech, Inc., South San Francisco, CA, USA
| | - Judith Klumperman
- Section Cell Biology, Center for Molecular Medicine, University Medical Center Utrecht, Utrecht, Netherlands
| | - Peter Walter
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, CA, USA
- Corresponding author. (P.W.); (G.J.J.)
| | - Grant J. Jensen
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA, USA
- Department of Chemistry and Biochemistry, Brigham Young University, Provo, UT, USA
- Corresponding author. (P.W.); (G.J.J.)
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25
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ANKRD22 is an N-myristoylated hairpin-like monotopic membrane protein specifically localized to lipid droplets. Sci Rep 2021; 11:19233. [PMID: 34584137 PMCID: PMC8478909 DOI: 10.1038/s41598-021-98486-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2021] [Accepted: 08/23/2021] [Indexed: 12/12/2022] Open
Abstract
The membrane topology and intracellular localization of ANKRD22, a novel human N-myristoylated protein with a predicted single-pass transmembrane domain that was recently reported to be overexpressed in cancer, were examined. Immunofluorescence staining of COS-1 cells transfected with cDNA encoding ANKRD22 coupled with organelle markers revealed that ANKRD22 localized specifically to lipid droplets (LD). Analysis of the intracellular localization of ANKRD22 mutants C-terminally fused to glycosylatable tumor necrosis factor (GLCTNF) and assessment of their susceptibility to protein N-glycosylation revealed that ANKRD22 is synthesized on the endoplasmic reticulum (ER) membrane as an N-myristoylated hairpin-like monotopic membrane protein with the amino- and carboxyl termini facing the cytoplasm and then sorted to LD. Pro98 located at the center of the predicted membrane domain was found to be essential for the formation of the hairpin-like monotopic topology of ANKRD22. Moreover, the hairpin-like monotopic topology, and positively charged residues located near the C-terminus were demonstrated to be required for the sorting of ANKRD22 from ER to LD. Protein N-myristoylation was found to positively affect the LD localization. Thus, multiple factors, including hairpin-like monotopic membrane topology, C-terminal positively charged residues, and protein N-myristoylation cooperatively affected the intracellular targeting of ANKRD22 to LD.
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26
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Garcia-Pardo ME, Simpson JC, O'Sullivan NC. A novel automated image analysis pipeline for quantifying morphological changes to the endoplasmic reticulum in cultured human cells. BMC Bioinformatics 2021; 22:427. [PMID: 34496765 PMCID: PMC8425006 DOI: 10.1186/s12859-021-04334-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Accepted: 08/24/2021] [Indexed: 11/10/2022] Open
Abstract
Background In mammalian cells the endoplasmic reticulum (ER) comprises a highly complex reticular morphology that is spread throughout the cytoplasm. This organelle is of particular interest to biologists, as its dysfunction is associated with numerous diseases, which often manifest themselves as changes to the structure and organisation of the reticular network. Due to its complex morphology, image analysis methods to quantitatively describe this organelle, and importantly any changes to it, are lacking. Results In this work we detail a methodological approach that utilises automated high-content screening microscopy to capture images of cells fluorescently-labelled for various ER markers, followed by their quantitative analysis. We propose that two key metrics, namely the area of dense ER and the area of polygonal regions in between the reticular elements, together provide a basis for measuring the quantities of rough and smooth ER, respectively. We demonstrate that a number of different pharmacological perturbations to the ER can be quantitatively measured and compared in our automated image analysis pipeline. Furthermore, we show that this method can be implemented in both commercial and open-access image analysis software with comparable results. Conclusions We propose that this method has the potential to be applied in the context of large-scale genetic and chemical perturbations to assess the organisation of the ER in adherent cell cultures. Supplementary Information The online version contains supplementary material available at 10.1186/s12859-021-04334-x.
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Affiliation(s)
- M Elena Garcia-Pardo
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin 4, Ireland
| | - Jeremy C Simpson
- Cell Screening Laboratory, UCD School of Biology and Environmental Science, University College Dublin, Dublin 4, Ireland
| | - Niamh C O'Sullivan
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin 4, Ireland.
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27
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Intertwined and Finely Balanced: Endoplasmic Reticulum Morphology, Dynamics, Function, and Diseases. Cells 2021; 10:cells10092341. [PMID: 34571990 PMCID: PMC8472773 DOI: 10.3390/cells10092341] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2021] [Revised: 09/02/2021] [Accepted: 09/04/2021] [Indexed: 02/07/2023] Open
Abstract
The endoplasmic reticulum (ER) is an organelle that is responsible for many essential subcellular processes. Interconnected narrow tubules at the periphery and thicker sheet-like regions in the perinuclear region are linked to the nuclear envelope. It is becoming apparent that the complex morphology and dynamics of the ER are linked to its function. Mutations in the proteins involved in regulating ER structure and movement are implicated in many diseases including neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and amyotrophic lateral sclerosis (ALS). The ER is also hijacked by pathogens to promote their replication. Bacteria such as Legionella pneumophila and Chlamydia trachomatis, as well as the Zika virus, bind to ER morphology and dynamics-regulating proteins to exploit the functions of the ER to their advantage. This review covers our understanding of ER morphology, including the functional subdomains and membrane contact sites that the organelle forms. We also focus on ER dynamics and the current efforts to quantify ER motion and discuss the diseases related to ER morphology and dynamics.
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28
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Perkins HT, Allan VJ, Waigh TA. Network organisation and the dynamics of tubules in the endoplasmic reticulum. Sci Rep 2021; 11:16230. [PMID: 34376706 PMCID: PMC8355327 DOI: 10.1038/s41598-021-94901-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 06/27/2021] [Indexed: 02/07/2023] Open
Abstract
The endoplasmic reticulum (ER) is a eukaryotic subcellular organelle composed of tubules and sheet-like areas of membrane connected at junctions. The tubule network is highly dynamic and undergoes rapid and continual rearrangement. There are currently few tools to evaluate network organisation and dynamics. We quantified ER network organisation in Vero and MRC5 cells, and developed an analysis workflow for dynamics of established tubules in live cells. The persistence length, tubule length, junction coordination number and angles of the network were quantified. Hallmarks of imbalances in ER tension, indications of interactions with microtubules and other subcellular organelles, and active dynamics were observed. Clear differences in dynamic behaviour were observed for established tubules at different positions within the cell using itemset mining. We found that tubules with activity-driven fluctuations were more likely to be located away from the cell periphery and a population of peripheral tubules with no signs of active motion was found.
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Affiliation(s)
- Hannah T Perkins
- Biological Physics, Department of Physics and Astronomy, Schuster Building, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK
- Division of Molecular and Cellular Function, School of Biological Sciences, Michael Smith Building, The University of Manchester, Dover Street, Manchester, M13 9PT, UK
| | - Victoria J Allan
- Division of Molecular and Cellular Function, School of Biological Sciences, Michael Smith Building, The University of Manchester, Dover Street, Manchester, M13 9PT, UK.
| | - Thomas A Waigh
- Biological Physics, Department of Physics and Astronomy, Schuster Building, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.
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29
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Yuval O, Iosilevskii Y, Meledin A, Podbilewicz B, Shemesh T. Neuron tracing and quantitative analyses of dendritic architecture reveal symmetrical three-way-junctions and phenotypes of git-1 in C. elegans. PLoS Comput Biol 2021; 17:e1009185. [PMID: 34280180 PMCID: PMC8321406 DOI: 10.1371/journal.pcbi.1009185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Revised: 07/29/2021] [Accepted: 06/15/2021] [Indexed: 11/18/2022] Open
Abstract
Complex dendritic trees are a distinctive feature of neurons. Alterations to dendritic morphology are associated with developmental, behavioral and neurodegenerative changes. The highly-arborized PVD neuron of C. elegans serves as a model to study dendritic patterning; however, quantitative, objective and automated analyses of PVD morphology are missing. Here, we present a method for neuronal feature extraction, based on deep-learning and fitting algorithms. The extracted neuronal architecture is represented by a database of structural elements for abstracted analysis. We obtain excellent automatic tracing of PVD trees and uncover that dendritic junctions are unevenly distributed. Surprisingly, these junctions are three-way-symmetrical on average, while dendritic processes are arranged orthogonally. We quantify the effect of mutation in git-1, a regulator of dendritic spine formation, on PVD morphology and discover a localized reduction in junctions. Our findings shed new light on PVD architecture, demonstrating the effectiveness of our objective analyses of dendritic morphology and suggest molecular control mechanisms. Nerve cells (neurons) collect input signals via branched cellular projections called dendrites. A major aspect of the study of neurons, dating back over a century, involves the characterization of neuronal shapes and of their dendritic processes. Here, we present an algorithmic approach for detection and classification of the tree-like dendrites of the PVD neuron in C. elegans worms. A key feature of our approach is to represent dendritic trees by a set of fundamental shapes, such as junctions and linear elements. By analyzing this dataset, we discovered several novel structural features. We have found that the junctions connecting branched dendrites have a three-way-symmetry, although the dendrites are arranged in a crosshatch pattern, and that the distribution of junctions varies across distinct sub-classes of the PVD’s dendritic tree. We further quantified subtle morphological effects due to mutation in the git-1 gene, a known regulator of dendritic spines. Our findings suggest molecular mechanisms for dendritic shape regulation and may help direct new avenues of research.
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Affiliation(s)
- Omer Yuval
- Faculty of Biology, Technion–Israel Institute of Technology, Haifa, Israel
- School of Computing, Faculty of Engineering and Physical Sciences, University of Leeds, Leeds, United Kingdom
| | - Yael Iosilevskii
- Faculty of Biology, Technion–Israel Institute of Technology, Haifa, Israel
| | - Anna Meledin
- Faculty of Biology, Technion–Israel Institute of Technology, Haifa, Israel
| | - Benjamin Podbilewicz
- Faculty of Biology, Technion–Israel Institute of Technology, Haifa, Israel
- * E-mail: (BP); (TS)
| | - Tom Shemesh
- Faculty of Biology, Technion–Israel Institute of Technology, Haifa, Israel
- * E-mail: (BP); (TS)
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30
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Cheng J, Liu HP, Lin WY, Tsai FJ. Machine learning compensates fold-change method and highlights oxidative phosphorylation in the brain transcriptome of Alzheimer's disease. Sci Rep 2021; 11:13704. [PMID: 34211065 PMCID: PMC8249453 DOI: 10.1038/s41598-021-93085-z] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Accepted: 06/18/2021] [Indexed: 02/06/2023] Open
Abstract
Alzheimer's disease (AD) is a neurodegenerative disorder causing 70% of dementia cases. However, the mechanism of disease development is still elusive. Despite the availability of a wide range of biological data, a comprehensive understanding of AD's mechanism from machine learning (ML) is so far unrealized, majorly due to the lack of needed data density. To harness the AD mechanism's knowledge from the expression profiles of postmortem prefrontal cortex samples of 310 AD and 157 controls, we used seven predictive operators or combinations of RapidMiner Studio operators to establish predictive models from the input matrix and to assign a weight to each attribute. Besides, conventional fold-change methods were also applied as controls. The identified genes were further submitted to enrichment analysis for KEGG pathways. The average accuracy of ML models ranges from 86.30% to 91.22%. The overlap ratio of the identified genes between ML and conventional methods ranges from 19.7% to 21.3%. ML exclusively identified oxidative phosphorylation genes in the AD pathway. Our results highlighted the deficiency of oxidative phosphorylation in AD and suggest that ML should be considered as complementary to the conventional fold-change methods in transcriptome studies.
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Affiliation(s)
- Jack Cheng
- grid.254145.30000 0001 0083 6092Graduate Institute of Integrated Medicine, College of Chinese Medicine, China Medical University, Taichung, 40402 Taiwan ,grid.411508.90000 0004 0572 9415Department of Medical Research, China Medical University Hospital, Taichung, 40447 Taiwan
| | - Hsin-Ping Liu
- grid.254145.30000 0001 0083 6092Graduate Institute of Acupuncture Science, College of Chinese Medicine, China Medical University, Taichung, 40402 Taiwan
| | - Wei-Yong Lin
- grid.254145.30000 0001 0083 6092Graduate Institute of Integrated Medicine, College of Chinese Medicine, China Medical University, Taichung, 40402 Taiwan ,grid.411508.90000 0004 0572 9415Department of Medical Research, China Medical University Hospital, Taichung, 40447 Taiwan ,grid.254145.30000 0001 0083 6092Brain Diseases Research Center, China Medical University, Taichung, 40402 Taiwan
| | - Fuu-Jen Tsai
- grid.411508.90000 0004 0572 9415Department of Medical Research, China Medical University Hospital, Taichung, 40447 Taiwan ,grid.254145.30000 0001 0083 6092School of Chinese Medicine, China Medical University, Taichung, 40402 Taiwan ,grid.252470.60000 0000 9263 9645Department of Medical Laboratory and Biotechnology, Asia University, Taichung, 41354 Taiwan ,grid.254145.30000 0001 0083 6092Division of Pediatric Genetics, Children’s Hospital of China Medical University, Taichung, 40447 Taiwan
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31
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Gumeni S, Vantaggiato C, Montopoli M, Orso G. Hereditary Spastic Paraplegia and Future Therapeutic Directions: Beneficial Effects of Small Compounds Acting on Cellular Stress. Front Neurosci 2021; 15:660714. [PMID: 34025345 PMCID: PMC8134669 DOI: 10.3389/fnins.2021.660714] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 03/29/2021] [Indexed: 12/29/2022] Open
Abstract
Hereditary spastic paraplegia (HSP) is a group of inherited neurodegenerative conditions that share a characteristic feature of degeneration of the longest axons within the corticospinal tract, which leads to progressive spasticity and weakness of the lower limbs. Mutations of over 70 genes produce defects in various biological pathways: axonal transport, lipid metabolism, endoplasmic reticulum (ER) shaping, mitochondrial function, and endosomal trafficking. HSPs suffer from an adequate therapeutic plan. Currently the treatments foreseen for patients affected by this pathology are physiotherapy, to maintain the outgoing tone, and muscle relaxant therapies for spasticity. Very few clinical studies have been conducted, and it's urgent to implement preclinical animal studies devoted to pharmacological test and screening, to expand the rose of compounds potentially attractive for clinical trials. Small animal models, such as Drosophila melanogaster and zebrafish, have been generated, analyzed, and used as preclinical model for screening of compounds and their effects. In this work, we briefly described the role of HSP-linked proteins in the organization of ER endomembrane system and in the regulation of ER homeostasis and stress as a common pathological mechanism for these HSP forms. We then focused our attention on the pharmacodynamic and pharmacokinetic features of some recently identified molecules with antioxidant property, such as salubrinal, guanabenz, N-acetyl cysteine, methylene blue, rapamycin, and naringenin, and on their potential use in future clinical studies. Expanding the models and the pharmacological screening for HSP disease is necessary to give an opportunity to patients and clinicians to test new molecules.
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Affiliation(s)
- Sentiljana Gumeni
- Department of Cell Biology and Biophysics, Faculty of Biology, National and Kapodistrian University of Athens, Athens, Greece
| | - Chiara Vantaggiato
- Laboratory of Molecular Biology, Scientific Institute IRCCS Eugenio Medea, Bosisio Parini, Italy
| | - Monica Montopoli
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padua, Italy
| | - Genny Orso
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Padua, Italy
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32
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Speckner K, Stadler L, Weiss M. Unscrambling exit site patterns on the endoplasmic reticulum as a quenched demixing process. Biophys J 2021; 120:2532-2542. [PMID: 33932435 DOI: 10.1016/j.bpj.2021.04.023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 03/31/2021] [Accepted: 04/19/2021] [Indexed: 11/19/2022] Open
Abstract
The endoplasmic reticulum (ER) is a vital organelle in mammalian cells with a complex morphology. Consisting of sheet-like cisternae in the cell center, the peripheral ER forms a vast tubular network on which a dispersed pattern of a few hundred specialized domains (ER exit sites (ERESs)) is maintained. Molecular details of cargo sorting and vesicle formation at individual ERESs, fueling the early secretory pathway, have been studied in some detail. The emergence of spatially extended ERES patterns, however, has remained poorly understood. Here, we show that these patterns are determined by the underlying ER morphology, suggesting ERESs to emerge from a demixing process that is quenched by the ER network topology. In particular, we observed fewer but larger ERESs when transforming the ER network to more sheet-like morphologies. In contrast, little to no changes with respect to native ERES patterns were observed when fragmenting the ER, indicating that hampering the diffusion-mediated coarse graining of domains is key for native ERES patterns. Model simulations support the notion of effective diffusion barriers impeding the coarse graining and maturation of ERES patterns. We speculate that tuning a simple demixing mechanism by the ER topology allows for a robust but flexible adaption of ERES patterns, ensuring a properly working early secretory pathway in a variety of conditions.
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Affiliation(s)
| | - Lorenz Stadler
- Experimental Physics I, University of Bayreuth, Bayreuth, Germany
| | - Matthias Weiss
- Experimental Physics I, University of Bayreuth, Bayreuth, Germany.
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33
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Morphological Heterogeneity of the Endoplasmic Reticulum within Neurons and Its Implications in Neurodegeneration. Cells 2021; 10:cells10050970. [PMID: 33919188 PMCID: PMC8143122 DOI: 10.3390/cells10050970] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Revised: 04/13/2021] [Accepted: 04/19/2021] [Indexed: 12/19/2022] Open
Abstract
The endoplasmic reticulum (ER) is a multipurpose organelle comprising dynamic structural subdomains, such as ER sheets and tubules, serving to maintain protein, calcium, and lipid homeostasis. In neurons, the single ER is compartmentalized with a careful segregation of the structural subdomains in somatic and neurite (axodendritic) regions. The distribution and arrangement of these ER subdomains varies between different neuronal types. Mutations in ER membrane shaping proteins and morphological changes in the ER are associated with various neurodegenerative diseases implying significance of ER morphology in maintaining neuronal integrity. Specific neurons, such as the highly arborized dopaminergic neurons, are prone to stress and neurodegeneration. Differences in morphology and functionality of ER between the neurons may account for their varied sensitivity to stress and neurodegenerative changes. In this review, we explore the neuronal ER and discuss its distinct morphological attributes and specific functions. We hypothesize that morphological heterogeneity of the ER in neurons is an important factor that accounts for their selective susceptibility to neurodegeneration.
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Sandor A, Fricker MD, Kriechbaumer V, Sweetlove LJ. IntEResting structures: formation and applications of organized smooth endoplasmic reticulum in plant cells. PLANT PHYSIOLOGY 2021; 185:550-561. [PMID: 33822222 PMCID: PMC8892044 DOI: 10.1104/pp.20.00719] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Accepted: 07/21/2020] [Indexed: 06/12/2023]
Abstract
The endoplasmic reticulum (ER) is an organelle with remarkable plasticity, capable of rapidly changing its structure to accommodate different functions based on intra- and extracellular cues. One of the ER structures observed in plants is known as "organized smooth endoplasmic reticulum" (OSER), consisting of symmetrically stacked ER membrane arrays. In plants, these structures were first described in certain specialized tissues, e.g. the sieve elements of the phloem, and more recently in transgenic plants overexpressing ER membrane resident proteins. To date, much of the investigation of OSER focused on yeast and animal cells but research into plant OSER has started to grow. In this update, we give a succinct overview of research into the OSER phenomenon in plant cells with case studies highlighting both native and synthetic occurrences of OSER. We also assess the primary driving forces that trigger the formation of OSER, collating evidence from the literature to compare two competing theories for the origin of OSER: that OSER formation is initiated by oligomerizing protein accumulation in the ER membrane or that OSER is the result of ER membrane proliferation. This has long been a source of controversy in the field and here we suggest a way to integrate arguments from both sides into a single unifying theory. Finally, we discuss the potential biotechnological uses of OSER as a tool for the nascent plant synthetic biology field with possible applications as a synthetic microdomain for metabolic engineering and as an extensive membrane surface for synthetic chemistry or protein accumulation.
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Affiliation(s)
- Andras Sandor
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Mark D Fricker
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
| | - Verena Kriechbaumer
- Department of Biological and Medical Sciences, Oxford Brookes University, Oxford OX3 0BP, UK
| | - Lee J Sweetlove
- Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK
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Maintaining the structural and functional homeostasis of the plant endoplasmic reticulum. Dev Cell 2021; 56:919-932. [PMID: 33662257 DOI: 10.1016/j.devcel.2021.02.008] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2020] [Revised: 01/21/2021] [Accepted: 02/08/2021] [Indexed: 12/14/2022]
Abstract
The endoplasmic reticulum (ER) is a ubiquitous organelle that is vital to the life of eukaryotic cells. It synthesizes essential lipids and proteins and initiates the glycosylation of intracellular and surface proteins. As such, the ER is necessary for cell growth and communication with the external environment. The ER is also a highly dynamic organelle, whose structure is continuously remodeled through an interaction with the cytoskeleton and the action of specialized ER shapers. Recent and significant advances in ER studies have brought to light conserved and unique features underlying the structure and function of this organelle in plant cells. In this review, exciting developments in the understanding of the mechanisms for plant ER structural and functional homeostasis, particularly those that underpin ER network architecture and ER degradation, are presented and discussed.
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Kriechbaumer V, Brandizzi F. The plant endoplasmic reticulum: an organized chaos of tubules and sheets with multiple functions. J Microsc 2020; 280:122-133. [PMID: 32426862 PMCID: PMC10895883 DOI: 10.1111/jmi.12909] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2020] [Revised: 05/08/2020] [Accepted: 05/14/2020] [Indexed: 12/14/2022]
Abstract
The endoplasmic reticulum is a fascinating organelle at the core of the secretory pathway. It is responsible for the synthesis of one third of the cellular proteome and, in plant cells, it produces receptors and transporters of hormones as well as the proteins responsible for the biosynthesis of critical components of a cellulosic cell wall. The endoplasmic reticulum structure resembles a spider-web network of interconnected tubules and cisternae that pervades the cell. The study of the dynamics and interaction of this organelles with other cellular structures such as the plasma membrane, the Golgi apparatus and the cytoskeleton, have been permitted by the implementation of fluorescent protein and advanced confocal imaging. In this review, we report on the findings that contributed towards the understanding of the endoplasmic reticulum morphology and function with the aid of fluorescent proteins, focusing on the contributions provided by pioneering work from the lab of the late Professor Chris Hawes.
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Affiliation(s)
- V Kriechbaumer
- Plant Cell Biology, Department of Biological and Medical Sciences, Oxford Brookes University, Oxford, U.K
| | - F Brandizzi
- MSU-DOE Plant Research Laboratory, Department of Plant Biology, Michigan State University, East Lansing, Michigan, U.S.A
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Chen YJ, Williams JM, Arvan P, Tsai B. Reticulon protects the integrity of the ER membrane during ER escape of large macromolecular protein complexes. J Cell Biol 2020; 219:133556. [PMID: 31895406 PMCID: PMC7041682 DOI: 10.1083/jcb.201908182] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2019] [Revised: 10/28/2019] [Accepted: 11/24/2019] [Indexed: 02/08/2023] Open
Abstract
Escape of large macromolecular complexes from the endoplasmic reticulum (ER), such as a viral particle or cellular aggregate, likely induces mechanical stress initiated on the luminal side of the ER membrane, which may threaten its integrity. How the ER responds to this threat remains unknown. Here we demonstrate that the cytosolic leaflet ER morphogenic protein reticulon (RTN) protects ER membrane integrity when polyomavirus SV40 escapes the ER to reach the cytosol en route to infection. SV40 coopts an intrinsic RTN function, as we also found that RTN prevents membrane damage during ER escape of a misfolded proinsulin aggregate destined for lysosomal degradation via ER-phagy. Our studies reveal that although ER membrane integrity may be threatened during ER escape of large macromolecular protein complexes, the action of RTN counters this, presumably by deploying its curvature-inducing activity to provide membrane flexibility and stability to limit mechanical stress imposed on the ER membrane.
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Affiliation(s)
- Yu-Jie Chen
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Jeffrey M Williams
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
| | - Peter Arvan
- Division of Metabolism Endocrinology and Diabetes, Comprehensive Diabetes Center, University of Michigan Medical School, Ann Arbor, MI
| | - Billy Tsai
- Department of Cell and Developmental Biology, University of Michigan Medical School, Ann Arbor, MI
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Niwa M. A cell cycle checkpoint for the endoplasmic reticulum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1867:118825. [PMID: 32828757 DOI: 10.1016/j.bbamcr.2020.118825] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 08/10/2020] [Accepted: 08/12/2020] [Indexed: 02/07/2023]
Abstract
The generation of new cells is one of the most fundamental aspects of cell biology. Proper regulation of the cell cycle is critical for human health, as underscored by many diseases associated with errors in cell cycle regulation, including both cancer and hereditary diseases. A large body of work has identified regulatory mechanisms and checkpoints that ensure accurate and timely replication and segregation of chromosomal DNA. However, few studies have evaluated the extent to which similar checkpoints exist for the division of cytoplasmic components, including organelles. Such checkpoint mechanisms might be crucial for compartments that cannot be generated de novo, such as the endoplasmic reticulum (ER). In this review, we highlight recent work in the model organism Saccharomyces cerevisiae that led to the discovery of such a checkpoint that ensures that cells inherit functional ER into the daughter cell.
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Affiliation(s)
- Maho Niwa
- Division of Biological Sciences, Section of Molecular Biology, University of California San Diego, NSB#1, Rm 5328, 9500 Gilman Drive, La Jolla, CA 92093-0377, United States of America.
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Bozelli JC, Epand RM. Membrane Shape and the Regulation of Biological Processes. J Mol Biol 2020; 432:5124-5136. [DOI: 10.1016/j.jmb.2020.03.028] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 03/25/2020] [Accepted: 03/27/2020] [Indexed: 01/06/2023]
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40
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TMCC3 localizes at the three-way junctions for the proper tubular network of the endoplasmic reticulum. Biochem J 2020; 476:3241-3260. [PMID: 31696206 DOI: 10.1042/bcj20190359] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Revised: 10/08/2019] [Accepted: 10/17/2019] [Indexed: 01/26/2023]
Abstract
The tubular network of the endoplasmic reticulum (ER) is formed by connecting ER tubules through three-way junctions. Two classes of the conserved ER membrane proteins, atlastins and lunapark, have been shown to reside at the three-way junctions so far and be involved in the generation and stabilization of the three-way junctions. In this study, we report TMCC3 (transmembrane and coiled-coil domain family 3), a member of the TEX28 family, as another ER membrane protein that resides at the three-way junctions in mammalian cells. When the TEX28 family members were transfected into U2OS cells, TMCC3 specifically localized at the three-way junctions in the peripheral ER. TMCC3 bound to atlastins through the C-terminal transmembrane domains. A TMCC3 mutant lacking the N-terminal coiled-coil domain abolished localization to the three-way junctions, suggesting that TMCC3 localized independently of binding to atlastins. TMCC3 knockdown caused a decrease in the number of three-way junctions and expansion of ER sheets, leading to a reduction of the tubular ER network in U2OS cells. The TMCC3 knockdown phenotype was partially rescued by the overexpression of atlastin-2, suggesting that TMCC3 knockdown would decrease the activity of atlastins. These results indicate that TMCC3 localizes at the three-way junctions for the proper tubular ER network.
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Shi X, Hai L, Govindasamy K, Gao J, Coppens I, Hu J, Wang Q, Bhanot P. A Plasmodium homolog of ER tubule-forming proteins is required for parasite virulence. Mol Microbiol 2020; 114:454-467. [PMID: 32432369 DOI: 10.1111/mmi.14526] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2019] [Revised: 05/04/2020] [Accepted: 05/05/2020] [Indexed: 01/27/2023]
Abstract
Reticulon and REEP family of proteins stabilize the high curvature of endoplasmic reticulum (ER) tubules. Plasmodium berghei Yop1 (PbYop1) is a REEP5 homolog in Plasmodium. Here, we characterize its function using a gene-knockout (Pbyop1∆). Pbyop1∆ asexual stage parasites display abnormal ER architecture and an enlarged digestive vacuole. The erythrocytic cycle of Pbyop1∆ parasites is severely attenuated and the incidence of experimental cerebral malaria is significantly decreased in Pbyop1∆-infected mice. Pbyop1∆ sporozoites have reduced speed, are slower to invade host cells but give rise to equal numbers of infected HepG2 cells, as WT sporozoites. We propose that PbYOP1's disruption may lead to defects in trafficking and secretion of a subset of proteins required for parasite development and invasion of erythrocytes. Furthermore, the maintenance of ER morphology in different parasite stages is likely to depend on different proteins.
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Affiliation(s)
- Xiaoyu Shi
- Department of Immunology, School of Basic Medical Sciences, Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China
| | - Lei Hai
- Department of Immunology, School of Basic Medical Sciences, Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China
| | - Kavitha Govindasamy
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, Newark, NJ, USA
| | - Jian Gao
- Department of Immunology, School of Basic Medical Sciences, Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China
| | - Isabelle Coppens
- Department of Molecular Microbiology and Immunology, The Johns Hopkins University Bloomberg School of Public Health, Baltimore, MD, USA
| | - Junjie Hu
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Qian Wang
- Department of Immunology, School of Basic Medical Sciences, Tianjin Key Laboratory of Cellular and Molecular Immunology, Key Laboratory of Immune Microenvironment and Diseases of Educational Ministry of China, Tianjin Medical University, Tianjin, China.,National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
| | - Purnima Bhanot
- Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers New Jersey Medical School, Newark, NJ, USA
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Kaul Z, Mookherjee D, Das S, Chatterjee D, Chakrabarti S, Chakrabarti O. Loss of tumor susceptibility gene 101 (TSG101) perturbs endoplasmic reticulum structure and function. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2020; 1867:118741. [PMID: 32422153 DOI: 10.1016/j.bbamcr.2020.118741] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2020] [Revised: 05/02/2020] [Accepted: 05/08/2020] [Indexed: 12/30/2022]
Abstract
Tumor susceptibility gene 101 (TSG101), an ESCRT-I protein, is implicated in multiple cellular processes and its functional depletion can lead to blocked lysosomal degradation, cell cycle arrest, demyelination and neurodegeneration. Here, we show that loss of TSG101 results in endoplasmic reticulum (ER) stress and this causes ER membrane remodelling (EMR). This correlates with an expansion of ER, increased vacuolation, altered relative distribution of the rough and smooth ER and disruption of three-way junctions. Blocked lysosomal degradation due to TSG101 depletion leads to ER stress and Ca2+ leakage from ER stores, causing destabilization of actin cytoskeleton. Inhibiting Ca2+ release from the ER by blocking ryanodine receptors (RYRs) with Dantrolene partially rescues the ER stress phenotypes. Hence, in this study we have identified the involvement of TSG101 in modulating ER stress mediated remodelling by engaging the actin cytoskeleton. This is significant because functional depletion of TSG101 effectuates ER-stress, perturbs the structure, mobility and function of the ER, all aspects closely associated with neurodegenerative diseases. SUMMARY STATEMENT: We show that tumor susceptibility gene (TSG) 101 regulates endoplasmic reticulum (ER) stress and its membrane remodelling. Loss of TSG101 perturbs structure, mobility and function of the ER as a consequence of actin destabilization.
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Affiliation(s)
- Zenia Kaul
- Biophysics & Structural Genomics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India; Laboratory of Immune System Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA..
| | - Debdatto Mookherjee
- Biophysics & Structural Genomics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India
| | - Subhrangshu Das
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, CN 6, Sector V, Salt Lake, Kolkata 700091, India
| | - Debmita Chatterjee
- Biophysics & Structural Genomics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India
| | - Saikat Chakrabarti
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, CN 6, Sector V, Salt Lake, Kolkata 700091, India
| | - Oishee Chakrabarti
- Biophysics & Structural Genomics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700064, India; Homi Bhabha National Institute, India.
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43
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Ubiquitylation of the ER-Shaping Protein Lunapark via the CRL3KLHL12 Ubiquitin Ligase Complex. Cell Rep 2020; 31:107664. [DOI: 10.1016/j.celrep.2020.107664] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Revised: 01/16/2020] [Accepted: 04/28/2020] [Indexed: 11/19/2022] Open
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Carter SD, Hampton CM, Langlois R, Melero R, Farino ZJ, Calderon MJ, Li W, Wallace CT, Tran NH, Grassucci RA, Siegmund SE, Pemberton J, Morgenstern TJ, Eisenman L, Aguilar JI, Greenberg NL, Levy ES, Yi E, Mitchell WG, Rice WJ, Wigge C, Pilli J, George EW, Aslanoglou D, Courel M, Freyberg RJ, Javitch JA, Wills ZP, Area-Gomez E, Shiva S, Bartolini F, Volchuk A, Murray SA, Aridor M, Fish KN, Walter P, Balla T, Fass D, Wolf SG, Watkins SC, Carazo JM, Jensen GJ, Frank J, Freyberg Z. Ribosome-associated vesicles: A dynamic subcompartment of the endoplasmic reticulum in secretory cells. SCIENCE ADVANCES 2020; 6:eaay9572. [PMID: 32270040 PMCID: PMC7112762 DOI: 10.1126/sciadv.aay9572] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 01/13/2020] [Indexed: 05/21/2023]
Abstract
The endoplasmic reticulum (ER) is a highly dynamic network of membranes. Here, we combine live-cell microscopy with in situ cryo-electron tomography to directly visualize ER dynamics in several secretory cell types including pancreatic β-cells and neurons under near-native conditions. Using these imaging approaches, we identify a novel, mobile form of ER, ribosome-associated vesicles (RAVs), found primarily in the cell periphery, which is conserved across different cell types and species. We show that RAVs exist as distinct, highly dynamic structures separate from the intact ER reticular architecture that interact with mitochondria via direct intermembrane contacts. These findings describe a new ER subcompartment within cells.
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Affiliation(s)
- Stephen D. Carter
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Cheri M. Hampton
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Robert Langlois
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Roberto Melero
- Biocomputing Unit, Centro Nacional de Biotecnología–CSIC, Darwin 3, Campus Universidad Autónoma, 28049 Madrid, Spain
| | - Zachary J. Farino
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Michael J. Calderon
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Wen Li
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Callen T. Wallace
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Ngoc Han Tran
- HHMI, Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Robert A. Grassucci
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
| | - Stephanie E. Siegmund
- Department of Cellular, Molecular and Biophysical Studies, Columbia University Medical Center, New York, NY 10032, USA
- Department of Neurology, Columbia University, New York, NY 10032, USA
| | - Joshua Pemberton
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Travis J. Morgenstern
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Leanna Eisenman
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jenny I. Aguilar
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Nili L. Greenberg
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Elana S. Levy
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Edward Yi
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - William G. Mitchell
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | | | | | - Jyotsna Pilli
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Emily W. George
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Despoina Aslanoglou
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Maïté Courel
- CNRS-UMR7622, Institut de Biologie Paris-Seine, Université Pierre & Marie Curie, 75252 Paris, France
| | - Robin J. Freyberg
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Jonathan A. Javitch
- Department of Psychiatry, Columbia University, New York, NY 10032, USA
- Division of Molecular Therapeutics, New York State Psychiatric Institute, New York, NY 10032, USA
| | - Zachary P. Wills
- Department of Neurobiology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Estela Area-Gomez
- Department of Neurology, Columbia University, New York, NY 10032, USA
| | - Sruti Shiva
- Department of Pharmacology and Chemical Biology, University of Pittsburgh, Pittsburgh, PA 15261, USA
- Vascular Medicine Institute, University of Pittsburgh, Pittsburgh, PA 15261, USA
- Center for Metabolism and Mitochondrial Medicine, University of Pittsburgh, Pittsburgh, PA 15261, USA
| | - Francesca Bartolini
- Department of Pathology and Cell Biology, Columbia University, New York, NY 10032, USA
| | - Allen Volchuk
- Program in Cell Biology, Hospital for Sick Children, Toronto, Ontario, Canada
| | - Sandra A. Murray
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Meir Aridor
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Kenneth N. Fish
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - Peter Walter
- HHMI, Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Tamas Balla
- Section on Molecular Signal Transduction, Program for Developmental Neuroscience, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Deborah Fass
- Department of Structural Biology, Weizmann Institute of Science, Rehovot, Israel
| | - Sharon G. Wolf
- Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel
| | - Simon C. Watkins
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
| | - José María Carazo
- Biocomputing Unit, Centro Nacional de Biotecnología–CSIC, Darwin 3, Campus Universidad Autónoma, 28049 Madrid, Spain
| | - Grant J. Jensen
- HHMI, Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA
| | - Joachim Frank
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY 10032, USA
- Department of Biological Sciences, Columbia University, New York, NY 10027, USA
| | - Zachary Freyberg
- Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA 15213, USA
- Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA 15213, USA
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Lee CT, Laughlin JG, Angliviel de La Beaumelle N, Amaro RE, McCammon JA, Ramamoorthi R, Holst M, Rangamani P. 3D mesh processing using GAMer 2 to enable reaction-diffusion simulations in realistic cellular geometries. PLoS Comput Biol 2020; 16:e1007756. [PMID: 32251448 PMCID: PMC7162555 DOI: 10.1371/journal.pcbi.1007756] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 04/16/2020] [Accepted: 03/01/2020] [Indexed: 12/17/2022] Open
Abstract
Recent advances in electron microscopy have enabled the imaging of single cells in 3D at nanometer length scale resolutions. An uncharted frontier for in silico biology is the ability to simulate cellular processes using these observed geometries. Enabling such simulations requires watertight meshing of electron micrograph images into 3D volume meshes, which can then form the basis of computer simulations of such processes using numerical techniques such as the finite element method. In this paper, we describe the use of our recently rewritten mesh processing software, GAMer 2, to bridge the gap between poorly conditioned meshes generated from segmented micrographs and boundary marked tetrahedral meshes which are compatible with simulation. We demonstrate the application of a workflow using GAMer 2 to a series of electron micrographs of neuronal dendrite morphology explored at three different length scales and show that the resulting meshes are suitable for finite element simulations. This work is an important step towards making physical simulations of biological processes in realistic geometries routine. Innovations in algorithms to reconstruct and simulate cellular length scale phenomena based on emerging structural data will enable realistic physical models and advance discovery at the interface of geometry and cellular processes. We posit that a new frontier at the intersection of computational technologies and single cell biology is now open.
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Affiliation(s)
- Christopher T. Lee
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California, United States of America
| | - Justin G. Laughlin
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California, United States of America
| | - Nils Angliviel de La Beaumelle
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California, United States of America
| | - Rommie E. Amaro
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, United States of America
| | - J. Andrew McCammon
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California, United States of America
| | - Ravi Ramamoorthi
- Department of Computer Science and Engineering, University of California, San Diego, La Jolla, California, United States of America
| | - Michael Holst
- Department of Mathematics, University of California, San Diego, La Jolla, California, United States of America
| | - Padmini Rangamani
- Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California, United States of America
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Impact of global structure on diffusive exploration of organelle networks. Sci Rep 2020; 10:4984. [PMID: 32188905 PMCID: PMC7080787 DOI: 10.1038/s41598-020-61598-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Accepted: 02/25/2020] [Indexed: 01/08/2023] Open
Abstract
We investigate diffusive search on planar networks, motivated by tubular organelle networks in cell biology that contain molecules searching for reaction partners and binding sites. Exact calculation of the diffusive mean first-passage time on a spatial network is used to characterize the typical search time as a function of network connectivity. We find that global structural properties — the total edge length and number of loops — are sufficient to largely determine network exploration times for a variety of both synthetic planar networks and organelle morphologies extracted from living cells. For synthetic networks on a lattice, we predict the search time dependence on these global structural parameters by connecting with percolation theory, providing a bridge from irregular real-world networks to a simpler physical model. The dependence of search time on global network structural properties suggests that network architecture can be designed for efficient search without controlling the precise arrangement of connections. Specifically, increasing the number of loops substantially decreases search times, pointing to a potential physical mechanism for regulating reaction rates within organelle network structures.
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REEP5 depletion causes sarco-endoplasmic reticulum vacuolization and cardiac functional defects. Nat Commun 2020; 11:965. [PMID: 32075961 PMCID: PMC7031342 DOI: 10.1038/s41467-019-14143-9] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 12/17/2019] [Indexed: 12/17/2022] Open
Abstract
The sarco-endoplasmic reticulum (SR/ER) plays an important role in the development and progression of many heart diseases. However, many aspects of its structural organization remain largely unknown, particularly in cells with a highly differentiated SR/ER network. Here, we report a cardiac enriched, SR/ER membrane protein, REEP5 that is centrally involved in regulating SR/ER organization and cellular stress responses in cardiac myocytes. In vitro REEP5 depletion in mouse cardiac myocytes results in SR/ER membrane destabilization and luminal vacuolization along with decreased myocyte contractility and disrupted Ca2+ cycling. Further, in vivo CRISPR/Cas9-mediated REEP5 loss-of-function zebrafish mutants show sensitized cardiac dysfunction upon short-term verapamil treatment. Additionally, in vivo adeno-associated viral (AAV9)-induced REEP5 depletion in the mouse demonstrates cardiac dysfunction. These results demonstrate the critical role of REEP5 in SR/ER organization and function as well as normal heart function and development. The sarcoplasmic (SR) and endoplasmic reticulum (ER) are involved in heart development but how this arises is unclear. Here, the authors show that loss of a SR/ER protein REEP5 causes membrane destabilization and decreased cardiac myocyte contractility, with cardiac dysfunction in mutant mouse and zebrafish models.
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Abstract
This article summarizes recent progress on biomimetic subcellular structures and discusses integration of these isolated systems.
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Affiliation(s)
- Shuying Yang
- College of Chemistry and Materials Science
- Jinan University
- Guangzhou 510632
- China
| | - Lingxiang Jiang
- College of Chemistry and Materials Science
- Jinan University
- Guangzhou 510632
- China
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Dynamic constriction and fission of endoplasmic reticulum membranes by reticulon. Nat Commun 2019; 10:5327. [PMID: 31757972 PMCID: PMC6876568 DOI: 10.1038/s41467-019-13327-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Accepted: 10/25/2019] [Indexed: 12/16/2022] Open
Abstract
The endoplasmic reticulum (ER) is a continuous cell-wide membrane network. Network formation has been associated with proteins producing membrane curvature and fusion, such as reticulons and atlastin. Regulated network fragmentation, occurring in different physiological contexts, is less understood. Here we find that the ER has an embedded fragmentation mechanism based upon the ability of reticulon to produce fission of elongating network branches. In Drosophila, Rtnl1-facilitated fission is counterbalanced by atlastin-driven fusion, with the prevalence of Rtnl1 leading to ER fragmentation. Ectopic expression of Drosophila reticulon in COS-7 cells reveals individual fission events in dynamic ER tubules. Consistently, in vitro analyses show that reticulon produces velocity-dependent constriction of lipid nanotubes leading to stochastic fission via a hemifission mechanism. Fission occurs at elongation rates and pulling force ranges intrinsic to the ER, thus suggesting a principle whereby the dynamic balance between fusion and fission controlling organelle morphology depends on membrane motility. The endoplasmic reticulum (ER) is an intracellular network characterized by highly dynamic behavior whose control mechanisms are unclear. Here, the authors show that the ER-membrane protein Reticulon (Rtnl1) can constrict ER bilayers and lead to ER fission.
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Human Antiviral Protein MxA Forms Novel Metastable Membraneless Cytoplasmic Condensates Exhibiting Rapid Reversible Tonicity-Driven Phase Transitions. J Virol 2019; 93:JVI.01014-19. [PMID: 31484749 DOI: 10.1128/jvi.01014-19] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 08/28/2019] [Indexed: 12/13/2022] Open
Abstract
Phase-separated biomolecular condensates of proteins and nucleic acids form functional membrane-less organelles (e.g., stress granules and P-bodies) in the mammalian cell cytoplasm and nucleus. In contrast to the long-standing belief that interferon (IFN)-inducible human myxovirus resistance protein A (MxA) associated with the endoplasmic reticulum (ER) and Golgi apparatus, we report that MxA formed membraneless metastable (shape-changing) condensates in the cytoplasm. In our studies, we used the same cell lines and methods as those used by previous investigators but concluded that wild-type MxA formed variably sized spherical or irregular bodies, filaments, and even a reticulum distinct from that of ER/Golgi membranes. Moreover, in Huh7 cells, MxA structures associated with a novel cytoplasmic reticular meshwork of intermediate filaments. In live-cell assays, 1,6-hexanediol treatment led to rapid disassembly of green fluorescent protein (GFP)-MxA structures; FRAP revealed a relative stiffness with a mobile fraction of 0.24 ± 0.02 within condensates, consistent with a higher-order MxA network structure. Remarkably, in intact cells, GFP-MxA condensates reversibly disassembled/reassembled within minutes of sequential decrease/increase, respectively, in tonicity of extracellular medium, even in low-salt buffers adjusted only with sucrose. Condensates formed from IFN-α-induced endogenous MxA also displayed tonicity-driven disassembly/reassembly. In vesicular stomatitis virus (VSV)-infected Huh7 cells, the nucleocapsid (N) protein, which participates in forming phase-separated viral structures, associated with spherical GFP-MxA condensates in cells showing an antiviral effect. These observations prompt comparisons with the extensive literature on interactions between viruses and stress granules/P-bodies. Overall, the new data correct a long-standing misinterpretation in the MxA literature and provide evidence for membraneless MxA biomolecular condensates in the uninfected cell cytoplasm.IMPORTANCE There is a long-standing belief that interferon (IFN)-inducible human myxovirus resistance protein A (MxA), which displays antiviral activity against several RNA and DNA viruses, associates with the endoplasmic reticulum (ER) and Golgi apparatus. We provide data to correct this misinterpretation and further report that MxA forms membraneless metastable (shape-changing) condensates in the cytoplasm consisting of variably sized spherical or irregular bodies, filaments, and even a reticulum. Remarkably, MxA condensates showed the unique property of rapid (within 1 to 3 min) reversible disassembly and reassembly in intact cells exposed sequentially to hypotonic and isotonic conditions. Moreover, GFP-MxA condensates included the VSV nucleocapsid (N) protein, a protein previously shown to form liquid-like condensates. Since intracellular edema and ionic changes are hallmarks of cytopathic effects of a viral infection, the tonicity-driven regulation of MxA condensates may reflect a mechanism for modulation of MxA function during viral infection.
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