1
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Xia Z, Ng BG, Jennions E, Blomqvist M, Sandqvist Wiklund A, Hedberg‐Oldfors C, Gonzalez CR, Freeze HH, Ygberg S, Eklund EA. The Swedish COG6-CDG experience and a comprehensive literature review. JIMD Rep 2023; 64:79-89. [PMID: 36636598 PMCID: PMC9830022 DOI: 10.1002/jmd2.12338] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2022] [Revised: 09/07/2022] [Accepted: 09/08/2022] [Indexed: 01/16/2023] Open
Abstract
Here, we present the first two Swedish cases of Conserved Oligomeric Golgi complex subunit 6-congenital disorders of glycosylation (COG6-CDG). Their clinical symptoms include intellectual disability, Attention Deficit/Hyperactivity Disorder (ADHD), delayed brain myelinization, progressive microcephaly, joint laxity, hyperkeratosis, frequent infections, and enamel hypoplasia. In one family, compound heterozygous variants in COG6 were identified, where one (c.785A>G; p.Tyr262Cys) has previously been described in patients of Moroccan descent, whereas the other (c.238G>A; p.Glu80Lys) is undescribed. On the other hand, a previously undescribed homozygous duplication (c.1793_1795dup) was deemed the cause of the disease. To confirm the pathogenicity of the variants, we treated patient and control fibroblasts with the ER-Golgi transport inhibitor Brefeldin-A and show that patient cells manifest a significantly slower anterograde and retrograde ER-Golgi transport.
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Affiliation(s)
- Zhi‐Jie Xia
- Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Bobby G. Ng
- Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Elizabeth Jennions
- Department of PediatricsInstitute of Clinical Sciences, Sahlgrenska AcademyGothenburgSweden
| | - Maria Blomqvist
- Department of Laboratory MedicineInstitute of Biomedicine, University of GothenburgGothenburgSweden
- Department of Clinical ChemistrySahlgrenska University HospitalGothenburgSweden
| | | | - Carola Hedberg‐Oldfors
- Department of Laboratory MedicineInstitute of Biomedicine, University of GothenburgGothenburgSweden
| | | | - Hudson H. Freeze
- Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
| | - Sofia Ygberg
- Department of Medical Biochemistry and BiophysicsKarolinska InstituteStockholmSweden
- Centre for Inherited Metabolic Diseases (CMMS)Karolinska University HospitalStockholmSweden
- Pediatric NeurologyKarolinska University HospitalStockholmSweden
| | - Erik A. Eklund
- Sanford Burnham Prebys Medical Discovery InstituteLa JollaCaliforniaUSA
- Pediatrics, Clinical SciencesLund UniversityLundSweden
- Pediatric NeurologySkåne University HospitalLundSweden
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2
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Zhang X. Alterations of Golgi Structural Proteins and Glycosylation Defects in Cancer. Front Cell Dev Biol 2021; 9:665289. [PMID: 34055798 PMCID: PMC8149618 DOI: 10.3389/fcell.2021.665289] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2021] [Accepted: 04/19/2021] [Indexed: 12/21/2022] Open
Abstract
As the central hub in the secretory and endocytic pathways, the Golgi apparatus continually receives the flow of cargos and serves as a major processing station in the cell. Due to its dynamic nature, a sophisticated and constantly remodeling mechanism needs to be set up to maintain the Golgi architecture and function in the non-stop trafficking of proteins and lipids. Abundant evidence has been accumulated that a well-organized Golgi structure is required for its proper functions, especially protein glycosylation. Remarkably, altered glycosylation has been a hallmark of most cancer cells. To understand the causes of Golgi defects in cancer, efforts have been made to characterize Golgi structural proteins under physiological and pathological conditions. This review summarizes the current knowledge of crucial Golgi structural proteins and their connections with tumor progression. We foresee that understanding the Golgi structural and functional defects may help solve the puzzle of whether glycosylation defect is a cause or effect of oncogenesis.
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Affiliation(s)
- Xiaoyan Zhang
- College of Biomedicine and Health, Huazhong Agricultural University, Wuhan, China.,College of Life Science and Technology, Huazhong Agricultural University, Wuhan, China
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3
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D'Souza Z, Taher FS, Lupashin VV. Golgi inCOGnito: From vesicle tethering to human disease. Biochim Biophys Acta Gen Subj 2020; 1864:129694. [PMID: 32730773 PMCID: PMC7384418 DOI: 10.1016/j.bbagen.2020.129694] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/21/2020] [Accepted: 07/23/2020] [Indexed: 12/11/2022]
Abstract
The Conserved Oligomeric Golgi (COG) complex, a multi-subunit vesicle tethering complex of the CATCHR (Complexes Associated with Tethering Containing Helical Rods) family, controls several aspects of cellular homeostasis by orchestrating retrograde vesicle traffic within the Golgi. The COG complex interacts with all key players regulating intra-Golgi trafficking, namely SNAREs, SNARE-interacting proteins, Rabs, coiled-coil tethers, and vesicular coats. In cells, COG deficiencies result in the accumulation of non-tethered COG-complex dependent (CCD) vesicles, dramatic morphological and functional abnormalities of the Golgi and endosomes, severe defects in N- and O- glycosylation, Golgi retrograde trafficking, sorting and protein secretion. In humans, COG mutations lead to severe multi-systemic diseases known as COG-Congenital Disorders of Glycosylation (COG-CDG). In this report, we review the current knowledge of the COG complex and analyze COG-related trafficking and glycosylation defects in COG-CDG patients.
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Affiliation(s)
- Zinia D'Souza
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Farhana S Taher
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Vladimir V Lupashin
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA.
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4
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Blackburn JB, D'Souza Z, Lupashin VV. Maintaining order: COG complex controls Golgi trafficking, processing, and sorting. FEBS Lett 2019; 593:2466-2487. [PMID: 31381138 PMCID: PMC6771879 DOI: 10.1002/1873-3468.13570] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2019] [Revised: 07/31/2019] [Accepted: 08/01/2019] [Indexed: 12/31/2022]
Abstract
The conserved oligomeric Golgi (COG) complex, a multisubunit tethering complex of the CATCHR (complexes associated with tethering containing helical rods) family, controls membrane trafficking and ensures Golgi homeostasis by orchestrating retrograde vesicle targeting within the Golgi. In humans, COG defects lead to severe multisystemic diseases known as COG‐congenital disorders of glycosylation (COG‐CDG). The COG complex both physically and functionally interacts with all classes of molecules maintaining intra‐Golgi trafficking, namely SNAREs, SNARE‐interacting proteins, Rabs, coiled‐coil tethers, and vesicular coats. Here, we review our current knowledge of COG‐related trafficking and glycosylation defects in humans and model organisms, and analyze possible scenarios for the molecular mechanism of the COG orchestrated vesicle targeting.
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Affiliation(s)
- Jessica B Blackburn
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Zinia D'Souza
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Vladimir V Lupashin
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
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5
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Linders PT, Horst CVD, Beest MT, van den Bogaart G. Stx5-Mediated ER-Golgi Transport in Mammals and Yeast. Cells 2019; 8:cells8080780. [PMID: 31357511 PMCID: PMC6721632 DOI: 10.3390/cells8080780] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 07/25/2019] [Accepted: 07/25/2019] [Indexed: 01/12/2023] Open
Abstract
The soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) syntaxin 5 (Stx5) in mammals and its ortholog Sed5p in Saccharomyces cerevisiae mediate anterograde and retrograde endoplasmic reticulum (ER)-Golgi trafficking. Stx5 and Sed5p are structurally highly conserved and are both regulated by interactions with other ER-Golgi SNARE proteins, the Sec1/Munc18-like protein Scfd1/Sly1p and the membrane tethering complexes COG, p115, and GM130. Despite these similarities, yeast Sed5p and mammalian Stx5 are differently recruited to COPII-coated vesicles, and Stx5 interacts with the microtubular cytoskeleton, whereas Sed5p does not. In this review, we argue that these different Stx5 interactions contribute to structural differences in ER-Golgi transport between mammalian and yeast cells. Insight into the function of Stx5 is important given its essential role in the secretory pathway of eukaryotic cells and its involvement in infections and neurodegenerative diseases.
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Affiliation(s)
- Peter Ta Linders
- Tumor Immunology Lab, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Chiel van der Horst
- Tumor Immunology Lab, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Martin Ter Beest
- Tumor Immunology Lab, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands
| | - Geert van den Bogaart
- Tumor Immunology Lab, Radboud University Medical Center, Radboud Institute for Molecular Life Sciences, Geert Grooteplein 28, 6525 GA Nijmegen, The Netherlands.
- Department of Molecular Immunology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 7, 9747 AG Groningen, The Netherlands.
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6
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Blackburn JB, Kudlyk T, Pokrovskaya I, Lupashin VV. More than just sugars: Conserved oligomeric Golgi complex deficiency causes glycosylation-independent cellular defects. Traffic 2018; 19:463-480. [PMID: 29573151 PMCID: PMC5948163 DOI: 10.1111/tra.12564] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 03/14/2018] [Accepted: 03/15/2018] [Indexed: 01/03/2023]
Abstract
The conserved oligomeric Golgi (COG) complex controls membrane trafficking and ensures Golgi homeostasis by orchestrating retrograde vesicle trafficking within the Golgi. Human COG defects lead to severe multisystemic diseases known as COG-congenital disorders of glycosylation (COG-CDG). To gain better understanding of COG-CDGs, we compared COG knockout cells with cells deficient to 2 key enzymes, Alpha-1,3-mannosyl-glycoprotein 2-beta-N-acetylglucosaminyltransferase and uridine diphosphate-glucose 4-epimerase (GALE), which contribute to proper N- and O-glycosylation. While all knockout cells share similar defects in glycosylation, these defects only account for a small fraction of observed COG knockout phenotypes. Glycosylation deficiencies were not associated with the fragmented Golgi, abnormal endolysosomes, defective sorting and secretion or delayed retrograde trafficking, indicating that these phenotypes are probably not due to hypoglycosylation, but to other specific interactions or roles of the COG complex. Importantly, these COG deficiency specific phenotypes were also apparent in COG7-CDG patient fibroblasts, proving the human disease relevance of our CRISPR knockout findings. The knowledge gained from this study has important implications, both for understanding the physiological role of COG complex in Golgi homeostasis in eukaryotic cells, and for better understanding human diseases associated with COG/Golgi impairment.
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Affiliation(s)
- Jessica B Blackburn
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Tetyana Kudlyk
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Irina Pokrovskaya
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
| | - Vladimir V Lupashin
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, Little Rock, Arkansas
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7
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Shitara A, Shibui T, Okayama M, Arakawa T, Mizoguchi I, Sakakura Y, Takuma T. VAMP4 and its cognate SNAREs are required for maintaining the ribbon structure of the Golgi apparatus. J Oral Biosci 2017. [DOI: 10.1016/j.job.2017.05.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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8
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Haijes HA, Jaeken J, Foulquier F, van Hasselt PM. Hypothesis: lobe A (COG1–4)-CDG causes a more severe phenotype than lobe B (COG5–8)-CDG. J Med Genet 2017; 55:137-142. [DOI: 10.1136/jmedgenet-2017-104586] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2017] [Revised: 06/07/2017] [Accepted: 06/21/2017] [Indexed: 01/26/2023]
Abstract
The conserved oligomeric Golgi (COG) complex consists of eight subunits organized in two lobes: lobe A (COG1–4) and lobe B (COG5–8). The different functional roles of COG lobe A and lobe B might result in distinct clinical phenotypes in patients with COG-CDG (congenital disorders of glycosylation). This hypothesis is supported by three observations. First, knock-down of COG lobe A components affects Golgi morphology more severely than knock-down of COG lobe B components. Second, nearly all of the 27 patients with lobe B COG-CDG had bi-allelic truncating mutations, as compared with only one of the six patients with lobe A COG-CDG. This represents a frequency gap which suggests that bi-allelic truncating mutations in COG lobe A genes might be non-viable. Third, in support, large-scale exome data of healthy adults (Exome Aggregation Consortium (ExAC)) underline that COG lobe A genes are less tolerant to genetic variation than COG lobe B genes. Thus, comparable molecular defects are more detrimental in lobe A COG-CDG than in lobe B COG-CDG. In a larger perspective, clinical phenotypic severity corresponded nicely with tolerance to genetic variation. Therefore, genomic epidemiology can potentially be used as a photographic negative for mutational severity.
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9
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Golgi trafficking defects in postnatal microcephaly: The evidence for “Golgipathies”. Prog Neurobiol 2017; 153:46-63. [DOI: 10.1016/j.pneurobio.2017.03.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2016] [Revised: 02/22/2017] [Accepted: 03/29/2017] [Indexed: 12/17/2022]
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10
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Gómez-Salinero JM, López-Olañeta MM, Ortiz-Sánchez P, Larrasa-Alonso J, Gatto A, Felkin LE, Barton PJR, Navarro-Lérida I, Del Pozo MÁ, García-Pavía P, Sundararaman B, Giovinazo G, Yeo GW, Lara-Pezzi E. The Calcineurin Variant CnAβ1 Controls Mouse Embryonic Stem Cell Differentiation by Directing mTORC2 Membrane Localization and Activation. Cell Chem Biol 2016; 23:1372-1382. [PMID: 27746127 DOI: 10.1016/j.chembiol.2016.09.010] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2016] [Revised: 08/28/2016] [Accepted: 09/02/2016] [Indexed: 12/11/2022]
Abstract
Embryonic stem cells (ESC) have the potential to generate all the cell lineages that form the body. However, the molecular mechanisms underlying ESC differentiation and especially the role of alternative splicing in this process remain poorly understood. Here, we show that the alternative splicing regulator MBNL1 promotes generation of the atypical calcineurin Aβ variant CnAβ1 in mouse ESCs (mESC). CnAβ1 has a unique C-terminal domain that drives its localization mainly to the Golgi apparatus by interacting with Cog8. CnAβ1 regulates the intracellular localization and activation of the mTORC2 complex. CnAβ1 knockdown results in delocalization of mTORC2 from the membrane to the cytoplasm, inactivation of the AKT/GSK3β/β-catenin signaling pathway, and defective mesoderm specification. In summary, here we unveil the structural basis for the mechanism of action of CnAβ1 and its role in the differentiation of mESCs to the mesodermal lineage.
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Affiliation(s)
- Jesús M Gómez-Salinero
- Myocardial Pathophysiology Program, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Marina M López-Olañeta
- Myocardial Pathophysiology Program, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Paula Ortiz-Sánchez
- Myocardial Pathophysiology Program, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Javier Larrasa-Alonso
- Myocardial Pathophysiology Program, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Alberto Gatto
- Myocardial Pathophysiology Program, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Leanne E Felkin
- National Heart and Lung Institute, Imperial College London, London SW7 2AZ, UK
| | - Paul J R Barton
- National Heart and Lung Institute, Imperial College London, London SW7 2AZ, UK; NIHR Cardiovascular Biomedical Research Unit, Royal Brompton and Harefield NHS Foundation Trust, London SW7 2AZ, UK
| | - Inmaculada Navarro-Lérida
- Vascular Pathophysiology Program, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Miguel Ángel Del Pozo
- Vascular Pathophysiology Program, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Pablo García-Pavía
- Heart Failure and Inherited Cardiac Diseases Unit, Department of Cardiology, Hospital Universitario Puerta de Hierro Majadahonda, 28222 Madrid, Spain
| | - Balaji Sundararaman
- Sanford Consortium for Regenerative Medicine, University of California San Diego (UCSD), La Jolla, CA 92037, USA
| | - Giovanna Giovinazo
- Pluripotent Cell Technology Unit, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain
| | - Gene W Yeo
- Sanford Consortium for Regenerative Medicine, University of California San Diego (UCSD), La Jolla, CA 92037, USA
| | - Enrique Lara-Pezzi
- Myocardial Pathophysiology Program, Fundación Centro Nacional de Investigaciones Cardiovasculares Carlos III (CNIC), 28029 Madrid, Spain; National Heart and Lung Institute, Imperial College London, London SW7 2AZ, UK.
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11
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Willett R, Blackburn JB, Climer L, Pokrovskaya I, Kudlyk T, Wang W, Lupashin V. COG lobe B sub-complex engages v-SNARE GS15 and functions via regulated interaction with lobe A sub-complex. Sci Rep 2016; 6:29139. [PMID: 27385402 PMCID: PMC4935880 DOI: 10.1038/srep29139] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 06/14/2016] [Indexed: 01/03/2023] Open
Abstract
The conserved oligomeric Golgi (COG) complex is a peripheral membrane protein complex which orchestrates tethering of intra-Golgi vesicles. We found that COG1-4 (lobe A) and 5-8 (lobe B) protein assemblies are present as independent sub-complexes on cell membranes. Super-resolution microscopy demonstrates that COG sub-complexes are spatially separated on the Golgi with lobe A preferential localization on Golgi stacks and the presence of lobe B on vesicle-like structures, where it physically interacts with v-SNARE GS15. The localization and specific interaction of the COG sub-complexes with the components of vesicle tethering/fusion machinery suggests their different roles in the vesicle tethering cycle. We propose and test a novel model that employs association/disassociation of COG sub-complexes as a mechanism that directs vesicle tethering at Golgi membranes. We demonstrate that defective COG assembly or restriction of tethering complex disassembly by a covalent COG1-COG8 linkage is inhibitory to COG complex activity, supporting the model.
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Affiliation(s)
- Rose Willett
- Department of Physiology and Biophysics, UAMS, Little Rock, AR, USA
| | | | - Leslie Climer
- Department of Physiology and Biophysics, UAMS, Little Rock, AR, USA
| | | | - Tetyana Kudlyk
- Department of Physiology and Biophysics, UAMS, Little Rock, AR, USA
| | - Wei Wang
- Department of Physiology and Biophysics, UAMS, Little Rock, AR, USA
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12
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Bailey Blackburn J, Pokrovskaya I, Fisher P, Ungar D, Lupashin VV. COG Complex Complexities: Detailed Characterization of a Complete Set of HEK293T Cells Lacking Individual COG Subunits. Front Cell Dev Biol 2016; 4:23. [PMID: 27066481 PMCID: PMC4813393 DOI: 10.3389/fcell.2016.00023] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 03/11/2016] [Indexed: 01/05/2023] Open
Abstract
The Conserved Oligomeric Golgi complex is an evolutionarily conserved multisubunit tethering complex (MTC) that is crucial for intracellular membrane trafficking and Golgi homeostasis. The COG complex interacts with core vesicle docking and fusion machinery at the Golgi; however, its exact mechanism of action is still an enigma. Previous studies of COG complex were limited to the use of CDGII (Congenital disorders of glycosylation type II)-COG patient fibroblasts, siRNA mediated knockdowns, or protein relocalization approaches. In this study we have used the CRISPR approach to generate HEK293T knock-out (KO) cell lines missing individual COG subunits. These cell lines were characterized for glycosylation and trafficking defects, cell proliferation rates, stability of COG subunits, localization of Golgi markers, changes in Golgi structure, and N-glycan profiling. We found that all KO cell lines were uniformly deficient in cis/medial-Golgi glycosylation and each had nearly abolished binding of Cholera toxin. In addition, all cell lines showed defects in Golgi morphology, retrograde trafficking and sorting, sialylation and fucosylation, but severities varied according to the affected subunit. Lobe A and Cog6 subunit KOs displayed a more severely distorted Golgi structure, while Cog2, 3, 4, 5, and 7 knock outs had the most hypo glycosylated form of Lamp2. These results led us to conclude that every subunit is essential for COG complex function in Golgi trafficking, though to varying extents. We believe that this study and further analyses of these cells will help further elucidate the roles of individual COG subunits and bring a greater understanding to the class of MTCs as a whole.
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Affiliation(s)
- Jessica Bailey Blackburn
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences Little Rock, AR, USA
| | - Irina Pokrovskaya
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences Little Rock, AR, USA
| | - Peter Fisher
- Department of Biology, University of York York, UK
| | - Daniel Ungar
- Department of Biology, University of York York, UK
| | - Vladimir V Lupashin
- Department of Physiology and Biophysics, University of Arkansas for Medical Sciences Little Rock, AR, USA
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13
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Fisher P, Ungar D. Bridging the Gap between Glycosylation and Vesicle Traffic. Front Cell Dev Biol 2016; 4:15. [PMID: 27014691 PMCID: PMC4781848 DOI: 10.3389/fcell.2016.00015] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Accepted: 02/22/2016] [Indexed: 11/24/2022] Open
Abstract
Glycosylation is recognized as a vitally important posttranslational modification. The structure of glycans that decorate proteins and lipids is largely dictated by biosynthetic reactions occurring in the Golgi apparatus. This biosynthesis relies on the relative distribution of glycosyltransferases and glycosidases, which is maintained by retrograde vesicle traffic between Golgi cisternae. Tethering of vesicles at the Golgi apparatus prior to fusion is regulated by Rab GTPases, coiled-coil tethers termed golgins and the multisubunit tethering complex known as the conserved oligomeric Golgi (COG) complex. In this review we discuss the mechanisms involved in vesicle tethering at the Golgi apparatus and highlight the importance of tethering in the context of glycan biosynthesis and a set of diseases known as congenital disorders of glycosylation.
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Affiliation(s)
- Peter Fisher
- Department of Biology, University of York York, UK
| | - Daniel Ungar
- Department of Biology, University of York York, UK
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14
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Creating Knockouts of Conserved Oligomeric Golgi Complex Subunits Using CRISPR-Mediated Gene Editing Paired with a Selection Strategy Based on Glycosylation Defects Associated with Impaired COG Complex Function. Methods Mol Biol 2016; 1496:145-61. [PMID: 27632008 DOI: 10.1007/978-1-4939-6463-5_12] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The conserved oligomeric Golgi (COG) complex is a key evolutionally conserved multisubunit protein machinery that regulates tethering and fusion of intra-Golgi transport vesicles. The Golgi apparatus specifically promotes sorting and complex glycosylation of glycoconjugates. Without proper glycosylation and processing, proteins and lipids will be mislocalized and/or have impaired function. The Golgi glycosylation machinery is kept in homeostasis by a careful balance of anterograde and retrograde trafficking to ensure proper localization of the glycosylation enzymes and their substrates. This balance, like other steps of membrane trafficking, is maintained by vesicle trafficking machinery that includes COPI vesicular coat proteins, SNAREs, Rabs, and both coiled-coil and multi-subunit vesicular tethers. The COG complex interacts with other membrane trafficking components and is essential for proper localization of Golgi glycosylation machinery. Here we describe using CRISPR-mediated gene editing coupled with a phenotype-based selection strategy directly linked to the COG complex's role in glycosylation homeostasis to obtain COG complex subunit knockouts (KOs). This has resulted in clonal KOs for each COG subunit in HEK293T cells and gives the ability to further probe the role of the COG complex in Golgi homeostasis.
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15
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Bhatt JM, Viktorova EG, Busby T, Wyrozumska P, Newman LE, Lin H, Lee E, Wright J, Belov GA, Kahn RA, Sztul E. Oligomerization of the Sec7 domain Arf guanine nucleotide exchange factor GBF1 is dispensable for Golgi localization and function but regulates degradation. Am J Physiol Cell Physiol 2015; 310:C456-69. [PMID: 26718629 DOI: 10.1152/ajpcell.00185.2015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Accepted: 12/14/2015] [Indexed: 12/15/2022]
Abstract
Members of the large Sec7 domain-containing Arf guanine nucleotide exchange factor (GEF) family have been shown to dimerize through their NH2-terminal dimerization and cyclophilin binding (DCB) and homology upstream of Sec7 (HUS) domains. However, the importance of dimerization in GEF localization and function has not been assessed. We generated a GBF1 mutant (91/130) in which two residues required for oligomerization (K91 and E130 within the DCB domain) were replaced with A and assessed the effects of these mutations on GBF1 localization and cellular functions. We show that 91/130 is compromised in oligomerization but that it targets to the Golgi in a manner indistinguishable from wild-type GBF1 and that it rapidly exchanges between the cytosolic and membrane-bound pools. The 91/130 mutant appears active as it integrates within the functional network at the Golgi, supports Arf activation and COPI recruitment, and sustains Golgi homeostasis and cargo secretion when provided as a sole copy of functional GBF1 in cells. In addition, like wild-type GBF1, the 91/130 mutant supports poliovirus RNA replication, a process requiring GBF1 but believed to be independent of GBF1 catalytic activity. However, oligomerization appears to stabilize GBF1 in cells, and the 91/130 mutant is degraded faster than the wild-type GBF1. Our data support a model in which oligomerization is not a key regulator of GBF1 activity but impacts its function by regulating the cellular levels of GBF1.
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Affiliation(s)
- Jay M Bhatt
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Ekaterina G Viktorova
- Department of Veterinary Medicine, Virginia-Maryland Regional College of Veterinary Medicine, University of Maryland, College Park, Maryland; and
| | - Theodore Busby
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Paulina Wyrozumska
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Laura E Newman
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia
| | - Helen Lin
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
| | - Eunjoo Lee
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
| | - John Wright
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama
| | - George A Belov
- Department of Veterinary Medicine, Virginia-Maryland Regional College of Veterinary Medicine, University of Maryland, College Park, Maryland; and
| | - Richard A Kahn
- Department of Biochemistry, Emory University School of Medicine, Atlanta, Georgia
| | - Elizabeth Sztul
- Department of Cell, Developmental and Integrative Biology, University of Alabama at Birmingham, Birmingham, Alabama;
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Climer LK, Dobretsov M, Lupashin V. Defects in the COG complex and COG-related trafficking regulators affect neuronal Golgi function. Front Neurosci 2015; 9:405. [PMID: 26578865 PMCID: PMC4621299 DOI: 10.3389/fnins.2015.00405] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 10/12/2015] [Indexed: 12/22/2022] Open
Abstract
The Conserved Oligomeric Golgi (COG) complex is an evolutionarily conserved hetero-octameric protein complex that has been proposed to organize vesicle tethering at the Golgi apparatus. Defects in seven of the eight COG subunits are linked to Congenital Disorders of Glycosylation (CDG)-type II, a family of rare diseases involving misregulation of protein glycosylation, alterations in Golgi structure, variations in retrograde trafficking through the Golgi and system-wide clinical pathologies. A troublesome aspect of these diseases are the neurological pathologies such as low IQ, microcephaly, and cerebellar atrophy. The essential function of the COG complex is dependent upon interactions with other components of trafficking machinery, such as Rab-GTPases and SNAREs. COG-interacting Rabs and SNAREs have been implicated in neurodegenerative diseases like Alzheimer's disease and Parkinson's disease. Defects in Golgi maintenance disrupts trafficking and processing of essential proteins, frequently associated with and contributing to compromised neuron function and human disease. Despite the recent advances in molecular neuroscience, the subcellular bases for most neurodegenerative diseases are poorly understood. This article gives an overview of the potential contributions of the COG complex and its Rab and SNARE partners in the pathogenesis of different neurodegenerative disorders.
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Affiliation(s)
- Leslie K Climer
- Department of Physiology and Biophysics, College of Medicine, University of Arkansas for Medical Sciences Little Rock, AR, USA
| | - Maxim Dobretsov
- Department of Anesthesiology, College of Medicine, University of Arkansas for Medical Sciences Little Rock, AR, USA
| | - Vladimir Lupashin
- Department of Physiology and Biophysics, College of Medicine, University of Arkansas for Medical Sciences Little Rock, AR, USA
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17
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Cog5-Cog7 crystal structure reveals interactions essential for the function of a multisubunit tethering complex. Proc Natl Acad Sci U S A 2014; 111:15762-7. [PMID: 25331899 DOI: 10.1073/pnas.1414829111] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The conserved oligomeric Golgi (COG) complex is required, along with SNARE and Sec1/Munc18 (SM) proteins, for vesicle docking and fusion at the Golgi. COG, like other multisubunit tethering complexes (MTCs), is thought to function as a scaffold and/or chaperone to direct the assembly of productive SNARE complexes at the sites of membrane fusion. Reflecting this essential role, mutations in the COG complex can cause congenital disorders of glycosylation. A deeper understanding of COG function and dysfunction will likely depend on elucidating its molecular structure. Despite some progress toward this goal, including EM studies of COG lobe A (subunits 1-4) and higher-resolution structures of portions of Cog2 and Cog4, the structures of COG's eight subunits and the principles governing their assembly are mostly unknown. Here, we report the crystal structure of a complex between two lobe B subunits, Cog5 and Cog7. The structure reveals that Cog5 is a member of the complexes associated with tethering containing helical rods (CATCHR) fold family, with homology to subunits of other MTCs including the Dsl1, exocyst, and Golgi-associated retrograde protein (GARP) complexes. The Cog5-Cog7 interaction is analyzed in relation to the Dsl1 complex, the only other CATCHR-family MTC for which subunit interactions have been characterized in detail. Biochemical and functional studies validate the physiological relevance of the observed Cog5-Cog7 interface, indicate that it is conserved from yeast to humans, and demonstrate that its disruption in human cells causes defects in trafficking and glycosylation.
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18
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Target silencing of components of the conserved oligomeric Golgi complex impairs HIV-1 replication. Virus Res 2014; 192:92-102. [PMID: 25179963 DOI: 10.1016/j.virusres.2014.08.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 08/21/2014] [Accepted: 08/22/2014] [Indexed: 12/23/2022]
Abstract
All viruses require host cell factors to replicate. A large number of host factors have been identified that participate at numerous points of the human immunodeficiency virus 1 (HIV-1) life cycle. Recent evidence supports a role for components of the trans-Golgi network (TGN) in mediating early steps in the HIV-1 life cycle. The conserved oligomeric Golgi (COG) complex is a heteroctamer complex that functions in coat protein complex I (COPI)-mediated intra-Golgi retrograde trafficking and plays an important role in the maintenance of Golgi structure and integrity as well as glycosylation enzyme homeostasis. The targeted silencing of components of lobe B of the COG complex, namely COG5, COG6, COG7 and COG8, inhibited HIV-1 replication. This inhibition of HIV-1 replication preceded late reverse transcription (RT) but did not affect viral fusion. Silencing of the COG interacting protein the t-SNARE syntaxin 5, showed a similar defect in late RT product formation, strengthening the role of the TGN in HIV replication.
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19
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Hong W, Lev S. Tethering the assembly of SNARE complexes. Trends Cell Biol 2014; 24:35-43. [DOI: 10.1016/j.tcb.2013.09.006] [Citation(s) in RCA: 219] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 09/09/2013] [Accepted: 09/10/2013] [Indexed: 12/11/2022]
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