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Lowe M. The Physiological Functions of the Golgin Vesicle Tethering Proteins. Front Cell Dev Biol 2019; 7:94. [PMID: 31316978 PMCID: PMC6611411 DOI: 10.3389/fcell.2019.00094] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 05/16/2019] [Indexed: 01/02/2023] Open
Abstract
The golgins comprise a family of vesicle tethering proteins that act in a selective manner to tether transport vesicles at the Golgi apparatus. Tethering is followed by membrane fusion to complete the delivery of vesicle-bound cargo to the Golgi. Different golgins are localized to different regions of the Golgi, and their ability to selectively tether transport vesicles is important for the specificity of vesicle traffic in the secretory pathway. In recent years, our mechanistic understanding of golgin-mediated tethering has greatly improved. We are also beginning to appreciate how the loss of golgin function can impact upon physiological processes through the use of animal models and the study of human disease. These approaches have revealed that loss of a golgin causes tissue-restricted phenotypes, which can vary in severity and the cell types affected. In many cases, it is possible to attribute these phenotypes to a defect in vesicular traffic, although why certain tissues are sensitive to loss of a particular golgin is still, in most cases, unclear. Here, I will summarize recent progress in our understanding of golgins, focusing on the physiological roles of these proteins, as determined from animal models and the study of disease in humans. I will describe what these in vivo analyses have taught us, as well as highlight less understood aspects, and areas for future investigations.
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Affiliation(s)
- Martin Lowe
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
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Wehrle A, Witkos TM, Unger S, Schneider J, Follit JA, Hermann J, Welting T, Fano V, Hietala M, Vatanavicharn N, Schoner K, Spranger J, Schmidts M, Zabel B, Pazour GJ, Bloch-Zupan A, Nishimura G, Superti-Furga A, Lowe M, Lausch E. Hypomorphic mutations of TRIP11 cause odontochondrodysplasia. JCI Insight 2019; 4:124701. [PMID: 30728324 PMCID: PMC6413787 DOI: 10.1172/jci.insight.124701] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 12/20/2018] [Indexed: 12/24/2022] Open
Abstract
Odontochondrodysplasia (ODCD) is an unresolved genetic disorder of skeletal and dental development. Here, we show that ODCD is caused by hypomorphic TRIP11 mutations, and we identify ODCD as the nonlethal counterpart to achondrogenesis 1A (ACG1A), the known null phenotype in humans. TRIP11 encodes Golgi-associated microtubule-binding protein 210 (GMAP-210), an essential tether protein of the Golgi apparatus that physically interacts with intraflagellar transport 20 (IFT20), a component of the ciliary intraflagellar transport complex B. This association and extraskeletal disease manifestations in ODCD point to a cilium-dependent pathogenesis. However, our functional studies in patient-derived primary cells clearly support a Golgi-based disease mechanism. In spite of reduced abundance, residual GMAP variants maintain partial Golgi integrity, normal global protein secretion, and subcellular distribution of IFT20 in ODCD. These functions are lost when GMAP-210 is completely abrogated in ACG1A. However, a similar defect in chondrocyte maturation is observed in both disorders, which produces a cellular achondrogenesis phenotype of different severity, ensuing from aberrant glycan processing and impaired extracellular matrix proteoglycan secretion by the Golgi apparatus. Bi-allelic mutations of TRIP11 cause a spectrum of skeletal phenotypes whose severity is primarily based on impaired secretory trafficking and aberrant glycan processing.
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Affiliation(s)
- Anika Wehrle
- Department of Pediatrics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Tomasz M Witkos
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Sheila Unger
- Division of Genetic Medicine, University of Lausanne, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
| | - Judith Schneider
- Department of Pediatrics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - John A Follit
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Johannes Hermann
- Department of Pediatrics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Tim Welting
- Laboratory for Experimental Orthopedics, Department of Orthopaedic Surgery, Maastricht University Medical Centre, Maastricht, the Netherlands
| | - Virginia Fano
- Hospital de Pediatria JP Garrahan, Buenos Aires, Argentina
| | - Marja Hietala
- Medical Biochemistry and Genetics, University of Turku, Turku, Finland
| | | | - Katharina Schoner
- Institute of Pathology, Philipps-University Marburg, Marburg, Germany
| | - Jürgen Spranger
- Department of Pediatrics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Miriam Schmidts
- Department of Pediatrics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Bernhard Zabel
- Department of Pediatrics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Gregory J Pazour
- Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Agnes Bloch-Zupan
- Centre de Référence des Manifestations Odontologiques des Maladies Rares, Pôle de Médecine et Chirurgie Bucco-dentaires, Hôpitaux Universitaires de Strasbourg (HUS), Faculté de Chirurgie Dentaire, Université de Strasbourg, Strasbourg, France.,Université de Strasbourg, Faculté de Chirurgie Dentaire, Institute of Advanced Studies, USIAS, Strasbourg, France.,HUS, Pôle de Médecine et Chirurgie Bucco-dentaires Hôpital Civil, Centre de référence des maladies rares orales et dentaires, O-Rares, Filière Santé Maladies rares TETE COU, European Reference Network ERN CRANIO, Strasbourg, France.,Université de Strasbourg, Institut de Génétique et de Biologie Moléculaire et Cellulaire (IGBMC), CERBM, INSERM U1258, CNRS- UMR7104, Illkirch, France
| | - Gen Nishimura
- Department of Radiology and Medical Imaging, Tokyo Metropolitan Kiyose Children's Hospital, Kiyose, Japan
| | - Andrea Superti-Furga
- Division of Genetic Medicine, University of Lausanne, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
| | - Martin Lowe
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Ekkehart Lausch
- Department of Pediatrics, Medical Center-University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
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Bird IM, Kim SH, Schweppe DK, Caetano-Lopes J, Robling AG, Charles JF, Gygi SP, Warman ML, Smits PJ. The skeletal phenotype of achondrogenesis type 1A is caused exclusively by cartilage defects. Development 2018; 145:dev.156588. [PMID: 29180569 PMCID: PMC5825869 DOI: 10.1242/dev.156588] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Accepted: 11/16/2017] [Indexed: 12/12/2022]
Abstract
Inactivating mutations in the ubiquitously expressed membrane trafficking component GMAP-210 (encoded by Trip11) cause achondrogenesis type 1A (ACG1A). ACG1A is surprisingly tissue specific, mainly affecting cartilage development. Bone development is also abnormal, but as chondrogenesis and osteogenesis are closely coupled, this could be a secondary consequence of the cartilage defect. A possible explanation for the tissue specificity of ACG1A is that cartilage and bone are highly secretory tissues with a high use of the membrane trafficking machinery. The perinatal lethality of ACG1A prevents investigating this hypothesis. We therefore generated mice with conditional Trip11 knockout alleles and inactivated Trip11 in chondrocytes, osteoblasts, osteoclasts and pancreas acinar cells, all highly secretory cell types. We discovered that the ACG1A skeletal phenotype is solely due to absence of GMAP-210 in chondrocytes. Mice lacking GMAP-210 in osteoblasts, osteoclasts and acinar cells were normal. When we inactivated Trip11 in primary chondrocyte cultures, GMAP-210 deficiency affected trafficking of a subset of chondrocyte-expressed proteins rather than globally impairing membrane trafficking. Thus, GMAP-210 is essential for trafficking specific cargoes in chondrocytes but is dispensable in other highly secretory cells. Summary: Conditional inactivation of the cis-Golgin GMAP-210 reveals that the skeletal phenotype in achondrogenesis type-1A, which is caused by mutations in GMAP-210, is solely due to impaired protein trafficking by chondrocytes.
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Affiliation(s)
- Ian M Bird
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, Boston Children's Hospital, Boston, MA 02115, USA
| | - Susie H Kim
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, Boston Children's Hospital, Boston, MA 02115, USA
| | - Devin K Schweppe
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Joana Caetano-Lopes
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, Boston Children's Hospital, Boston, MA 02115, USA
| | - Alexander G Robling
- Department of Anatomy and Cell Biology, Indiana University, Indianapolis, IN 46202, USA
| | - Julia F Charles
- Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA
| | - Steven P Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA
| | - Matthew L Warman
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, Boston Children's Hospital, Boston, MA 02115, USA.,Howard Hughes Medical Institute, Boston Children's Hospital, Boston, MA 02115, USA.,Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
| | - Patrick J Smits
- Orthopaedic Research Laboratories, Department of Orthopaedic Surgery, Boston Children's Hospital, Boston, MA 02115, USA
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Cardenas J, Rivero S, Goud B, Bornens M, Rios RM. Golgi localisation of GMAP210 requires two distinct cis-membrane binding mechanisms. BMC Biol 2009; 7:56. [PMID: 19715559 PMCID: PMC2744908 DOI: 10.1186/1741-7007-7-56] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2009] [Accepted: 08/28/2009] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND The Golgi apparatus in mammals appears as a ribbon made up of interconnected stacks of flattened cisternae that is positioned close to the centrosome in a microtubule-dependent manner. How this organisation is achieved and retained is not well understood. GMAP210 is a long coiled-coil cis-Golgi associated protein that plays a role in maintaining Golgi ribbon integrity and position and contributes to the formation of the primary cilium. An amphipathic alpha-helix able to bind liposomes in vitro has been recently identified at the first 38 amino acids of the protein (amphipathic lipid-packing sensor motif), and an ARF1-binding domain (Grip-related Arf-binding domain) was found at the C-terminus. To which type of membranes these two GMAP210 regions bind in vivo and how this contributes to GMAP210 localisation and function remains to be investigated. RESULTS By using truncated as well as chimeric mutants and videomicroscopy we found that both the N-terminus and the C-terminus of GMAP210 are targeted to the cis-Golgi in vivo. The ALPS motif was identified as the N-terminal binding motif and appeared concentrated in the periphery of Golgi elements and between Golgi stacks. On the contrary, the C-terminal domain appeared uniformly distributed in the cis-cisternae of the Golgi apparatus. Strikingly, the two ends of the protein also behave differently in response to the drug Brefeldin A. The N-terminal domain redistributed to the endoplasmic reticulum (ER) exit sites, as does the full-length protein, whereas the C-terminal domain rapidly dissociated from the Golgi apparatus to the cytosol. Mutants comprising the full-length protein but lacking one of the terminal motifs also associated with the cis-Golgi with distribution patterns similar to those of the corresponding terminal end whereas a mutant consisting in fused N- and C-terminal ends exhibits identical localisation as the endogenous protein. CONCLUSION We conclude that the Golgi localisation of GMAP210 is the result of the combined action of the two N- and C-terminal domains that recognise different sub-regions of the cis-GA. Based on present and previous data, we propose a model in which GMAP210 would participate in homotypic fusion of cis-cisternae by anchoring the surface of cisternae via its C-terminus and projecting its distal N-terminus to bind the rims or to stabilise tubular structures connecting neighbouring cis-cisternae.
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Stamm S, Ben-Ari S, Rafalska I, Tang Y, Zhang Z, Toiber D, Thanaraj TA, Soreq H. Function of alternative splicing. Gene 2004; 344:1-20. [PMID: 15656968 DOI: 10.1016/j.gene.2004.10.022] [Citation(s) in RCA: 651] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2004] [Revised: 09/10/2004] [Accepted: 10/21/2004] [Indexed: 02/06/2023]
Abstract
Alternative splicing is one of the most important mechanisms to generate a large number of mRNA and protein isoforms from the surprisingly low number of human genes. Unlike promoter activity, which primarily regulates the amount of transcripts, alternative splicing changes the structure of transcripts and their encoded proteins. Together with nonsense-mediated decay (NMD), at least 25% of all alternative exons are predicted to regulate transcript abundance. Molecular analyses during the last decade demonstrate that alternative splicing determines the binding properties, intracellular localization, enzymatic activity, protein stability and posttranslational modifications of a large number of proteins. The magnitude of the effects range from a complete loss of function or acquisition of a new function to very subtle modulations, which are observed in the majority of cases reported. Alternative splicing factors regulate multiple pre-mRNAs and recent identification of physiological targets shows that a specific splicing factor regulates pre-mRNAs with coherent biological functions. Therefore, evidence is now accumulating that alternative splicing coordinates physiologically meaningful changes in protein isoform expression and is a key mechanism to generate the complex proteome of multicellular organisms.
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Affiliation(s)
- Stefan Stamm
- Institute for Biochemistry, University of Erlangen, Fahrstrasse 17, 91054 Erlangen, Germany.
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