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Abstract
Regulated transport through the secretory pathway is essential for embryonic development and homeostasis. Disruptions in this process impact cell fate, differentiation and survival, often resulting in abnormalities in morphogenesis and in disease. Several congenital malformations are caused by mutations in genes coding for proteins that regulate cargo protein transport in the secretory pathway. The severity of mutant phenotypes and the unclear aetiology of transport protein-associated pathologies have motivated research on the regulation and mechanisms through which these proteins contribute to morphogenesis. This review focuses on the role of the p24/transmembrane emp24 domain (TMED) family of cargo receptors in development and disease.
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Abstract
Originally identified as Golgi stacking factors in vitro, the Golgi reassembly stacking protein (GRASP) family has been shown to act as membrane tethers with multiple cellular roles. As an update to previous comprehensive reviews of the GRASP family (Giuliani et al., 2011; Vinke et al., 2011; Jarvela and Linstedt, 2012), we outline here the latest findings concerning their diverse roles. New insights into the mechanics of GRASP-mediated tethering come from recent crystal structures. The models of how GRASP65 and GRASP55 tether membranes relate directly to their role in Golgi ribbon formation in mammalian cells and the unlinking of the ribbon at the onset of mitosis. However, it is also clear that GRASPs act outside the Golgi with roles at the ER and ER exit sites (ERES). Furthermore, the proteins of this family display other roles upon cellular stress, especially in mediating unconventional secretion of both transmembrane proteins (Golgi bypass) and cytoplasmic proteins (through secretory autophagosomes).
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Affiliation(s)
- Catherine Rabouille
- Hubrecht Institute, Royal Netherlands Academy of Arts and Sciences (KNAW) and UMC UtrechtUtrecht, Netherlands; The Department of Cell Biology, University Medical Center UtrechtUtrecht, Netherlands
| | - Adam D Linstedt
- Department of Biological Sciences, Carnegie Mellon University Pittsburgh, PA, USA
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Duquet A, Melotti A, Mishra S, Malerba M, Seth C, Conod A, Ruiz i Altaba A. A novel genome-wide in vivo screen for metastatic suppressors in human colon cancer identifies the positive WNT-TCF pathway modulators TMED3 and SOX12. EMBO Mol Med 2015; 6:882-901. [PMID: 24920608 PMCID: PMC4119353 DOI: 10.15252/emmm.201303799] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The progression of tumors to the metastatic state involves the loss of metastatic suppressor functions. Finding these, however, is difficult as in vitro assays do not fully predict metastatic behavior, and the majority of studies have used cloned cell lines, which do not reflect primary tumor heterogeneity. Here, we have designed a novel genome-wide screen to identify metastatic suppressors using primary human tumor cells in mice, which allows saturation screens. Using this unbiased approach, we have tested the hypothesis that endogenous colon cancer metastatic suppressors affect WNT-TCF signaling. Our screen has identified two novel metastatic suppressors: TMED3 and SOX12, the knockdown of which increases metastatic growth after direct seeding. Moreover, both modify the type of self-renewing spheroids, but only knockdown of TMED3 also induces spheroid cell spreading and lung metastases from a subcutaneous xenograft. Importantly, whereas TMED3 and SOX12 belong to different families involved in protein secretion and transcriptional regulation, both promote endogenous WNT-TCF activity. Treatments for advanced or metastatic colon cancer may thus not benefit from WNT blockers, and these may promote a worse outcome.
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Affiliation(s)
- Arnaud Duquet
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
| | - Alice Melotti
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
| | - Sonakshi Mishra
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
| | - Monica Malerba
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
| | - Chandan Seth
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
| | - Arwen Conod
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
| | - Ariel Ruiz i Altaba
- Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva, Switzerland
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Vázquez-Martínez R, Díaz-Ruiz A, Almabouada F, Rabanal-Ruiz Y, Gracia-Navarro F, Malagón MM. Revisiting the regulated secretory pathway: from frogs to human. Gen Comp Endocrinol 2012; 175:1-9. [PMID: 21907200 DOI: 10.1016/j.ygcen.2011.08.017] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/17/2011] [Revised: 08/16/2011] [Accepted: 08/20/2011] [Indexed: 01/01/2023]
Abstract
The regulated secretory pathway is a hallmark of endocrine and neuroendocrine cells. This process comprises different sequential steps, including ER-associated protein synthesis, ER-to-Golgi protein transport, Golgi-associated posttranslational modification, sorting and packing of secretory proteins into carrier granules, cytoskeleton-based granule transport towards the plasma membrane and tethering, docking and fusion of granules with specialized releasing zones in the plasma membrane. Each one of these steps is tightly regulated by a large number of factors that function in a spatially and temporarily coordinated fashion. During the past three decades, much effort has been devoted to characterize the precise role of the yet-known proteins participating in the different steps of this process and to identify new regulatory factors in order to obtain a unifying picture of the secretory pathway. In spite of this and given the enormous complexity of the process, certain steps are not fully understood yet and many players remain to be identified. In this review, we offer a summary of the current knowledge on the main molecular mechanisms that govern and ensure the correct release of secretory proteins. In addition, we have integrated the advance on the field made possible by studies carried out in non-mammalian vertebrates, which, although not very numerous, have substantially contributed to acquire a mechanistic understanding of the regulated secretory pathway.
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Affiliation(s)
- Rafael Vázquez-Martínez
- Department of Cell Biology, Physiology and Immunology, Instituto Maimónides de Investigación Biomédica, University of Córdoba, 14014-Córdoba, Spain.
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Strating JRPM, Bouw G, Hafmans TGM, Martens GJM. p24 Proteins from the same subfamily are functionally nonredundant. Biochimie 2010; 93:528-32. [PMID: 21118709 DOI: 10.1016/j.biochi.2010.11.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2010] [Accepted: 11/22/2010] [Indexed: 11/17/2022]
Abstract
The p24 proteins function in early secretory pathway transport processes, but their exact role is unclear. In physiologically activated Xenopus melanotrope cells, a representative of each p24 subfamily (p24α(3), -β(1), -γ(3), -δ(2)) is upregulated coordinately with the major melanotrope cargo, proopiomelanocortin (POMC), whereas two other p24s (p24γ(2) and -δ(1)) are also expressed, but not coordinately with POMC. Using melanotrope-specific transgene expression, we here find that the roles of both p24γ(2) and p24δ(1) in the transport, glycosylation, sulphation and cleavage of POMC are different from those of their upregulated subfamily relatives (p24γ(3) and p24δ(2), respectively). Thus, even p24 proteins from the same subfamily have distinct functions in secretory cargo biosynthesis.
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Affiliation(s)
- Jeroen R P M Strating
- Donders Institute for Brain, Cognition and Behaviour, Centre for Neuroscience, and Nijmegen Centre for Molecular Life Sciences (NCMLS), 282 Department of Molecular Animal Physiology, Radboud University Nijmegen, Geert Grooteplein Zuid 28, Nijmegen, The Netherlands
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Strating JR, Hafmans TG, Martens GJ. COP-binding sites in p24δ2 are necessary for proper secretory cargo biosynthesis. Int J Biochem Cell Biol 2009; 41:1619-27. [DOI: 10.1016/j.biocel.2009.02.010] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Revised: 02/10/2009] [Accepted: 02/12/2009] [Indexed: 01/24/2023]
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Langhans M, Marcote MJ, Pimpl P, Virgili-López G, Robinson DG, Aniento F. In vivo Trafficking and Localization of p24 Proteins in Plant Cells. Traffic 2008; 9:770-85. [DOI: 10.1111/j.1600-0854.2008.00719.x] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Strating JRPM, Bouw G, Hafmans TGM, Martens GJM. Disparate effects of p24alpha and p24delta on secretory protein transport and processing. PLoS One 2007; 2:e704. [PMID: 17684551 PMCID: PMC1933603 DOI: 10.1371/journal.pone.0000704] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Accepted: 07/02/2007] [Indexed: 11/20/2022] Open
Abstract
Background The p24 family is thought to be somehow involved in endoplasmic reticulum (ER)-to-Golgi protein transport. A subset of the p24 proteins (p24α3, -β1, -γ3 and -δ2) is upregulated when Xenopus laevis intermediate pituitary melanotrope cells are physiologically activated to produce vast amounts of their major secretory cargo, the prohormone proopiomelanocortin (POMC). Methodology/Principal Findings Here we find that transgene expression of p24α3 or p24δ2 specifically in the Xenopus melanotrope cells in both cases causes an effective displacement of the endogenous p24 proteins, resulting in severely distorted p24 systems and disparate melanotrope cell phenotypes. Transgene expression of p24α3 greatly reduces POMC transport and leads to accumulation of the prohormone in large, ER-localized electron-dense structures, whereas p24δ2-transgenesis does not influence the overall ultrastructure of the cells nor POMC transport and cleavage, but affects the Golgi-based processes of POMC glycomaturation and sulfation. Conclusions/Significance Transgenic expression of two distinct p24 family members has disparate effects on secretory pathway functioning, illustrating the specificity and non-redundancy of our transgenic approach. We conclude that members of the p24 family furnish subcompartments of the secretory pathway with specific sets of machinery cargo to provide the proper microenvironments for efficient and correct secretory protein transport and processing.
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Affiliation(s)
- Jeroen R. P. M. Strating
- Department of Molecular Animal Physiology, Nijmegen Centre for Molecular Life Sciences, Institute for Neuroscience, Faculty of Science, Radboud University, Nijmegen, The Netherlands
| | - Gerrit Bouw
- Department of Molecular Animal Physiology, Nijmegen Centre for Molecular Life Sciences, Institute for Neuroscience, Faculty of Science, Radboud University, Nijmegen, The Netherlands
| | - Theo G. M. Hafmans
- Department of Molecular Animal Physiology, Nijmegen Centre for Molecular Life Sciences, Institute for Neuroscience, Faculty of Science, Radboud University, Nijmegen, The Netherlands
| | - Gerard J. M. Martens
- Department of Molecular Animal Physiology, Nijmegen Centre for Molecular Life Sciences, Institute for Neuroscience, Faculty of Science, Radboud University, Nijmegen, The Netherlands
- * To whom correspondence should be addressed. E-mail:
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Bouw G, Van Huizen R, Jansen EJR, Martens GJM. A cell-specific transgenic approach in Xenopus reveals the importance of a functional p24 system for a secretory cell. Mol Biol Cell 2003; 15:1244-53. [PMID: 14699062 PMCID: PMC363117 DOI: 10.1091/mbc.e03-08-0600] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The p24alpha, -beta, -gamma, and -delta proteins are major multimeric constituents of cycling endoplasmic reticulum-Golgi transport vesicles and are thought to be involved in protein transport through the early secretory pathway. In this study, we targeted transgene overexpression of p24delta2 specifically to the Xenopus intermediate pituitary melanotrope cell that is involved in background adaptation of the animal and produces high levels of its major secretory cargo proopiomelanocortin (POMC). The transgene product effectively displaced the endogenous p24 proteins, resulting in a melanotrope cell p24 system that consisted predominantly of the transgene p24delta2 protein. Despite the severely distorted p24 machinery, the subcellular structures as well as the level of POMC synthesis were normal in these cells. However, the number and pigment content of skin melanophores were reduced, impairing the ability of the transgenic animal to fully adapt to a black background. This physiological effect was likely caused by the affected profile of POMC-derived peptides observed in the transgenic melanotrope cells. Together, our results suggest that in the early secretory pathway an intact p24 system is essential for efficient secretory cargo transport or for supplying cargo carriers with the correct protein machinery to allow proper secretory protein processing.
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Affiliation(s)
- Gerrit Bouw
- Department of Molecular Animal Physiology, Nijmegen Center for Molecular Life Sciences, University of Nijmegen, 6525 GA Nijmegen, The Netherlands
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Abstract
Understanding the biosynthetic pathways involved in cellular transport is an important issue in cell biology. More than a hundred years after the discovery of the Golgi apparatus, we still do not understand the regulation of vesicular transport to, within and from the Golgi apparatus. Recently, however, it has become clear that cargo might not simply be a passive passenger, and that ADP-ribosylation factor (ARF) GAPs are not only GTPase-activating proteins for ARF, but might play crucial roles in regulating coat protein complex I vesicle formation.
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Affiliation(s)
- Anne Spang
- Friedrich Miescher Laboratorium, Max-Planck-Gesellschaft, Spemannstrasse 39 D-72076 Tübingen, Germany.
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