151
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Transcriptional regulation of tissue organization and cell morphogenesis: the fly retina as a case study. Dev Biol 2013; 385:168-78. [PMID: 24099926 DOI: 10.1016/j.ydbio.2013.09.031] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2013] [Revised: 09/27/2013] [Accepted: 09/29/2013] [Indexed: 12/11/2022]
Abstract
Understanding how a functional organ can be produced from a small group of cells remains an outstanding question in cell and developmental biology. The developing compound eye of Drosophila has long been a model of choice for addressing this question by dissecting the cellular, genetic and molecular pathways that govern cell specification, differentiation, and multicellular patterning during organogenesis. In this review, the author focussed on cell and tissue morphogenesis during fly retinal development, including the regulated changes in cell shape and cell packing that ultimately determine the shape and architecture of the compound eye. In particular, the author reviewed recent studies that highlight the prominent roles of transcriptional and hormonal controls that orchestrate the cell shape changes, cell-cell junction remodeling and polarized membrane growth that underlie photoreceptor morphogenesis and retinal patterning.
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152
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Abstract
Establishing and maintaining epithelial polarity is crucial during development and for adult tissue homeostasis. A complex network of evolutionarily conserved proteins regulates this compartmentalization. One such protein is Crumbs, a type I transmembrane protein initially shown to be an important apical determinant in Drosophila. We discuss recent studies that have advanced our understanding of the function and regulation of Crumbs. New findings obtained in flies and fish, reporting homotypic interactions of the extracellular domain and retromer-mediated recycling, shed light on the regulation of Crumbs levels and activity. These results - obtained in different organisms, tissues and developmental stages - point to more complex functions and regulation than previously assumed.
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Affiliation(s)
- Shirin Meher Pocha
- Max Planck Institute for Molecular Cell Biology and Genetics, Pfotenhauerstr. 108, 01307 Dresden, Germany.
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153
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Bergstralh DT, Haack T, St Johnston D. Epithelial polarity and spindle orientation: intersecting pathways. Philos Trans R Soc Lond B Biol Sci 2013; 368:20130291. [PMID: 24062590 PMCID: PMC3785970 DOI: 10.1098/rstb.2013.0291] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
During asymmetric stem cell divisions, the mitotic spindle must be correctly oriented and positioned with respect to the axis of cell polarity to ensure that cell fate determinants are appropriately segregated into only one daughter cell. By contrast, epithelial cells divide symmetrically and orient their mitotic spindles perpendicular to the main apical–basal polarity axis, so that both daughter cells remain within the epithelium. Work in the past 20 years has defined a core ternary complex consisting of Pins, Mud and Gαi that participates in spindle orientation in both asymmetric and symmetric divisions. As additional factors that interact with this complex continue to be identified, a theme has emerged: there is substantial overlap between the mechanisms that orient the spindle and those that establish and maintain apical–basal polarity in epithelial cells. In this review, we examine several factors implicated in both processes, namely Canoe, Bazooka, aPKC and Discs large, and consider the implications of this work on how the spindle is oriented during epithelial cell divisions.
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Affiliation(s)
- Dan T Bergstralh
- The Gurdon Institute and the Department of Genetics, University of Cambridge, , Tennis Court Road, Cambridge CB2 1QN, UK
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154
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Fedeles S, Gallagher AR. Cell polarity and cystic kidney disease. Pediatr Nephrol 2013; 28:1161-72. [PMID: 23161205 DOI: 10.1007/s00467-012-2337-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 10/02/2012] [Accepted: 10/02/2012] [Indexed: 10/27/2022]
Abstract
Epithelial cell polarity is essential for organ development; aberrations in this process have been implicated in various diseases, including polycystic kidney disease. Establishment and maintenance of cell polarity is governed by a number of molecular processes and how these processes operate remains an interesting question. Conserved protein complexes guide both apical-basolateral polarity and planar cell polarity. In this review we discuss the recent findings that provide insights into polarity mechanisms and the intriguing crosstalk between apical-basolateral polarity and planar cell polarity, and their relationship to cystic kidney disease.
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Affiliation(s)
- Sorin Fedeles
- Section of Nephrology, Department of Internal Medicine, Yale University School of Medicine, P.O. Box 208029, 333 Cedar Street, New Haven, CT 06520-8029, USA
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155
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Bergstralh DT, Lovegrove HE, St Johnston D. Discs large links spindle orientation to apical-basal polarity in Drosophila epithelia. Curr Biol 2013; 23:1707-12. [PMID: 23891112 PMCID: PMC3770898 DOI: 10.1016/j.cub.2013.07.017] [Citation(s) in RCA: 99] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 07/03/2013] [Accepted: 07/04/2013] [Indexed: 12/11/2022]
Abstract
Mitotic spindles in epithelial cells are oriented in the plane of the epithelium so that both daughter cells remain within the monolayer, and defects in spindle orientation have been proposed to promote tumorigenesis by causing epithelial disorganization and hyperplasia [1]. Previous work has implicated the apical polarity factor aPKC, the junctional protein APC2, and basal integrins in epithelial spindle orientation, but the underlying mechanisms remain unclear. We show that these factors are not required for spindle orientation in the Drosophila follicular epithelium. Furthermore, aPKC and other apical polarity factors disappear from the apical membrane in mitosis. Instead, spindle orientation requires the lateral factor Discs large (Dlg), a function that is separable from its role in epithelial polarity. In neuroblasts, Pins recruits Dlg and Mud to form an apical complex that orients spindles along the apical-basal axis. We show that Pins and Mud are also necessary for spindle orientation in follicle cells, as is the interaction between Dlg and Pins. Dlg localizes independently of Pins, however, suggesting that its lateral localization determines the planar orientation of the spindle in epithelial cells. Thus, different mechanisms recruit the conserved Dlg/Pins/Mud complex to orient the spindle in opposite directions in distinct cell types. Spindle orientation in follicle cells does not require aPKC, APC2, or integrins aPKC and other apical polarity factors disappear from the cortex during mitosis Dlg functions with Pins and Mud to orient the spindle toward the lateral cortex Dlg localization does not require Pins and may determine spindle orientation
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Affiliation(s)
- Dan T Bergstralh
- The Gurdon Institute and the Department of Genetics, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QN, UK
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156
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Sticking together the Crumbs - an unexpected function for an old friend. Nat Rev Mol Cell Biol 2013; 14:307-14. [PMID: 23609509 DOI: 10.1038/nrm3568] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Cell polarity and cell-cell junctions have pivotal roles in organizing cells into tissues and in mediating cell-cell communication. The transmembrane protein Crumbs has a well-established role in the maintenance of epithelial polarity, and it can also regulate signalling via the Notch and Hippo pathways to influence tissue growth. The functions of Crumbs in epithelial polarity and Hippo-mediated growth depend on its short intracellular domain. Recent evidence now points to a conserved and fundamental role for the extracellular domain of Crumbs in mediating homophilic Crumbs-Crumbs interactions at cell-cell junctions.
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157
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Seidl S, Braun U, Roos N, Li S, Lüdtke THW, Kispert A, Leitges M. Phenotypical analysis of atypical PKCs in vivo function display a compensatory system at mouse embryonic day 7.5. PLoS One 2013; 8:e62756. [PMID: 23690951 PMCID: PMC3653893 DOI: 10.1371/journal.pone.0062756] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 03/25/2013] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND The atypical protein kinases C (PKC) isoforms ι/λ and ζ play crucial roles in many cellular processes including development, cell proliferation, differentiation and cell survival. Possible redundancy between the two isoforms has always been an issue since most biochemical tools do not differentiate between the two proteins. Thus, much effort has been made during the last decades to characterize the functions of aPKCs using gene targeting approaches and depletion studies. However, little is known about the specific roles of each isoform in mouse development. METHODOLOGY/PRINCIPAL FINDINGS To evaluate the importance of PKCι in mouse development we designed PKCι deletion mutants using the gene targeting approach. We show that the deletion of PKCι, results in a reduced size of the amniotic cavity at E7.5 and impaired growth of the embryo at E8.5 with subsequent absorption of the embryo. Our data also indicate an impaired localization of ZO-1 and disorganized structure of the epithelial tissue in the embryo. Importantly, using electron microscopy, embryoid body formation and immunofluorescence analysis, we found, that in the absence of PKCι, tight junctions and apico-basal polarity were still established. Finally, our study points to a non-redundant PKCι function at E9.5, since expression of PKCζ is able to rescue the E7.5 phenotype, but could not prevent embryonic lethality at a later time-point (E9.5). CONCLUSION Our data show that PKCι is crucial for mouse embryogenesis but is dispensable for the establishment of polarity and tight junction formation. We present a compensatory function of PKCζ at E7.5, rescuing the phenotype. Furthermore, this study indicates at least one specific, yet unknown, PKCι function that cannot be compensated by the overexpression of PKCζ at E9.5.
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Affiliation(s)
- Sebastian Seidl
- The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
| | - Ursula Braun
- The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
| | - Norbert Roos
- Department of Molecular Biosciences, University of Oslo, Oslo, Norway
| | - Shaohua Li
- Department of Surgery, University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School, New Brunswick, New Jersey, United States of America
| | - Timo H.-W. Lüdtke
- Institute for Molecular Biology, Medizinische Hochschule Hannover, Hannover, Germany
| | - Andreas Kispert
- Institute for Molecular Biology, Medizinische Hochschule Hannover, Hannover, Germany
| | - Michael Leitges
- The Biotechnology Centre of Oslo, University of Oslo, Oslo, Norway
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158
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Dawes AT, Iron D. Cortical geometry may influence placement of interface between Par protein domains in early Caenorhabditis elegans embryos. J Theor Biol 2013; 333:27-37. [PMID: 23665289 DOI: 10.1016/j.jtbi.2013.04.024] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 04/23/2013] [Indexed: 12/16/2022]
Abstract
During polarization, proteins and other polarity determinants segregate to the opposite ends of the cell (the poles) creating biochemically and dynamically distinct regions. Embryos of the nematode worm Caenorhabditis elegans (C. elegans) polarize shortly after fertilization, creating distinct regions of Par protein family members. These regions are maintained through to first cleavage when the embryo divides along the plane specified by the interface between regions, creating daughter cells with different protein content. In wild type single cell embryos the interface between these Par protein regions is reliably positioned at approximately 60% egg length, however, it is not known what mechanisms are responsible for specifying the position of the interface. In this investigation, we use two mathematical models to investigate the movement and positioning of the interface: a biologically based reaction-diffusion model of Par protein dynamics, and the analytically tractable perturbed Allen-Cahn equation. When we numerically simulate the models on a static 2D domain with constant thickness, both models exhibit a persistently moving interface that specifies the boundary between distinct regions. When we modify the simulation domain geometry, movement halts and the interface is stably positioned where the domain thickness increases. Using asymptotic analysis with the perturbed Allen-Cahn equation, we show that interface movement depends explicitly on domain geometry. Using a combination of analytic and numeric techniques, we demonstrate that domain geometry, a historically overlooked aspect of cellular simulations, may play a significant role in spatial protein patterning during polarization.
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Affiliation(s)
- Adriana T Dawes
- Department of Mathematics, The Ohio State University, 100 Math Tower, 231 West 18th Avenue, Columbus, OH 43210-1174, United States.
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159
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Zhang Y, Wang W, Chen J, Zhang K, Gao F, Gao B, Zhang S, Dong M, Besenbacher F, Gong W, Zhang M, Sun F, Feng W. Structural insights into the intrinsic self-assembly of Par-3 N-terminal domain. Structure 2013; 21:997-1006. [PMID: 23643951 DOI: 10.1016/j.str.2013.04.004] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2013] [Revised: 03/27/2013] [Accepted: 04/01/2013] [Indexed: 12/17/2022]
Abstract
Par-3, the central organizer of the Par-3/Par-6/atypical protein kinase C complex, is a multimodular scaffold protein that is essential for cell polarity establishment and maintenance. The N-terminal domain (NTD) of Par-3 is capable of self-association to form filament-like structures, although the underlying mechanism is poorly understood. Here, we determined the crystal structure of Par-3 NTD and solved the filament structure by cryoelectron microscopy. We found that an intrinsic "front-to-back" interaction mode is important for Par-3 NTD self-association and that both the lateral and longitudinal packing within the filament are mediated by electrostatic interactions. Disruptions of the lateral or longitudinal packing significantly impaired Par-3 NTD self-association and thereby impacted the Par-3-mediated epithelial polarization. We finally demonstrated that a Par-3 NTD-like domain from histidine ammonia-lyase also harbors a similar self-association capacity. This work unequivocally provides the structural basis for Par-3 NTD self-association and characterizes one type of protein domain that can self-assemble via electrostatic interactions.
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Affiliation(s)
- Yan Zhang
- National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, China
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160
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Hoege C, Hyman AA. Principles of PAR polarity in Caenorhabditis elegans embryos. Nat Rev Mol Cell Biol 2013; 14:315-22. [PMID: 23594951 DOI: 10.1038/nrm3558] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
A hallmark of cell polarity in metazoans is the distribution of partitioning defective (PAR) proteins into two domains on the membrane. Domain boundaries are set by the collective integration of mechanical, biochemical and biophysical signals, and the resulting PAR domains define areas of cytosol specialization. However, the complexity of the signals acting on PAR proteins has been a barrier to uncovering the general principles of PAR polarity. We propose that physical studies, when combined with genetic data, provide new understanding of the mechanisms of polarity establishment in the Caenorhabditis elegans embryo and other organisms.
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Affiliation(s)
- Carsten Hoege
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, D-01307 Dresden, Germany.
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161
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Sotillos S, Krahn M, Espinosa-Vázquez JM, Hombría JCG. Src kinases mediate the interaction of the apical determinant Bazooka/PAR3 with STAT92E and increase signalling efficiency in Drosophila ectodermal cells. Development 2013; 140:1507-16. [DOI: 10.1242/dev.092320] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Intercellular communication depends on the correct organization of the signal transduction complexes. In many signalling pathways, the mechanisms controlling the overall cell polarity also localize components of these pathways to different domains of the plasma membrane. In the Drosophila ectoderm, the JAK/STAT pathway components are highly polarized with apical localization of the receptor, the associated kinase and the STAT92E protein itself. The apical localization of STAT92E is independent of the receptor complex and is due to its direct association with the apical determining protein Bazooka (Baz). Here, we find that Baz-STAT92E interaction depends on the presence of the Drosophila Src kinases. In the absence of Src, STAT92E cannot bind to Baz in cells or in whole embryos, and this correlates with an impairment of JAK/STAT signalling function. We believe that the requirement of Src proteins for STAT92E apical localization is mediated through Baz, as we can co-precipitate Src with Baz but not with STAT92E. This is the first time that a functional link between cell polarity, the JAK/STAT signalling pathway and the Src kinases has been established in a whole organism.
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Affiliation(s)
- Sol Sotillos
- Centro Andaluz de Biología del Desarrollo, CSIC/JA/UPO, Ctra de Utrera Km1, 41013 Sevilla, Spain
| | - Michael Krahn
- Stem Cell Biology, Department of Anatomy and Cell Biology, University of Goettingen, Justus-von-Liebig-Weg 11, 37 077 Goettingen, Germany
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162
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Chen J, Zhang M. The Par3/Par6/aPKC complex and epithelial cell polarity. Exp Cell Res 2013; 319:1357-64. [PMID: 23535009 DOI: 10.1016/j.yexcr.2013.03.021] [Citation(s) in RCA: 105] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Revised: 03/11/2013] [Accepted: 03/16/2013] [Indexed: 12/20/2022]
Abstract
Apical-basal polarity is the basic organizing principle of epithelial cells, and endows epithelial cells to function as defensive barriers and as mediators of vectorial transport of nutrients in and out of organisms. Apical-basal polarity is controlled by a number of conserved polarity factors that regulate cytoskeletal organizations, asymmetric distributions of cellular components, and directional transports across cells. Polarity factors often occupy specific membrane regions in response to the adhesion forces generated by cell-cell and cell-extracellular matrix interactions. Both internal polarity factors and the external extracellular matrices play fundamental roles in epithelial cell polarity establishment and maintenance. This review focuses on recent developments of the Par3/Par6/aPKC complex and its interacting proteins in epithelial cell polarity.
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Affiliation(s)
- Jia Chen
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
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163
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Hayase J, Kamakura S, Iwakiri Y, Yamaguchi Y, Izaki T, Ito T, Sumimoto H. The WD40 protein Morg1 facilitates Par6-aPKC binding to Crb3 for apical identity in epithelial cells. ACTA ACUST UNITED AC 2013; 200:635-50. [PMID: 23439680 PMCID: PMC3587828 DOI: 10.1083/jcb.201208150] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Formation of apico-basal polarity in epithelial cells is crucial for both morphogenesis (e.g., cyst formation) and function (e.g., tight junction development). Atypical protein kinase C (aPKC), complexed with Par6, is considered to translocate to the apical membrane and function in epithelial cell polarization. However, the mechanism for translocation of the Par6-aPKC complex has remained largely unknown. Here, we show that the WD40 protein Morg1 (mitogen-activated protein kinase organizer 1) directly binds to Par6 and thus facilitates apical targeting of Par6-aPKC in Madin-Darby canine kidney epithelial cells. Morg1 also interacts with the apical transmembrane protein Crumbs3 to promote Par6-aPKC binding to Crumbs3, which is reinforced with the apically localized small GTPase Cdc42. Depletion of Morg1 disrupted both tight junction development in monolayer culture and cyst formation in three-dimensional culture; apico-basal polarity was notably restored by forced targeting of aPKC to the apical surface. Thus, Par6-aPKC recruitment to the premature apical membrane appears to be required for definition of apical identity of epithelial cells.
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Affiliation(s)
- Junya Hayase
- Department of Biochemistry, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan
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164
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Abstract
Cell polarity is fundamental for the architecture and function of epithelial tissues. Epithelial polarization requires the intervention of several fundamental cell processes, whose integration in space and time is only starting to be elucidated. To understand what governs the building of epithelial tissues during development, it is essential to consider the polarization process in the context of the whole tissue. To this end, the development of three-dimensional organotypic cell culture models has brought new insights into the mechanisms underlying the establishment and maintenance of higher-order epithelial tissue architecture, and in the dynamic remodeling of cell polarity that often occurs during development of epithelial organs. Here we discuss some important aspects of mammalian epithelial morphogenesis, from the establishment of cell polarity to epithelial tissue generation.
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165
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Abstract
Determinants of cell polarity orient the behaviour of many cell types during development. Pioneering genetic screens in yeast, worms and flies have identified key polarity determinants that are evolutionarily conserved across the animal kingdom. Recent work in these three model organisms has combined computer modelling with experimental analysis to reveal the molecular mechanisms that drive the polarisation of determinants. Two key principles have emerged: the first is the requirement for a positive-feedback loop to drive self-recruitment of determinants to the plasma membrane; the second is the requirement for mutual antagonism between determinants that localise to opposite ends of the cell.
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Affiliation(s)
- Barry J Thompson
- Cancer Research UK, London Research Institute, Lincoln's Inn Fields, London WC2A 3LY, UK.
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166
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Leibfried A, Müller S, Ephrussi A. A Cdc42-regulated actin cytoskeleton mediates Drosophila oocyte polarization. Development 2013; 140:362-71. [DOI: 10.1242/dev.089250] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Polarity of the Drosophila oocyte is essential for correct development of the egg and future embryo. The Par proteins Par-6, aPKC and Bazooka are needed to maintain oocyte polarity and localize to specific domains early in oocyte development. To date, no upstream regulator or mechanism for localization of the Par proteins in the oocyte has been identified. We have analyzed the role of the small GTPase Cdc42 in oocyte polarity. We show that Cdc42 is required to maintain oocyte fate, which it achieves by mediating localization of Par proteins at distinct sites within this cell. We establish that Cdc42 localization itself is polarized to the anterolateral cortex of the oocyte and that Cdc42 is needed for maintenance of oocyte polarity throughout oogenesis. Our data show that Cdc42 ensures the integrity of the oocyte actin network and that disruption of this network with Latrunculin A phenocopies loss of Cdc42 or Par protein function in early stages of oogenesis. Finally, we show that Cdc42 and Par proteins, as well as Cdc42/Par and Arp3, interact in the context of oocyte polarity, and that loss of Par proteins reciprocally affects Cdc42 localization and the actin network. These results reveal a mutual dependence between Par proteins and Cdc42 for their localization, regulation of the actin cytoskeleton and, consequently, for the establishment of oocyte polarity. This most likely allows for the robustness in symmetry breaking in the cell.
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Affiliation(s)
- Andrea Leibfried
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Sandra Müller
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
| | - Anne Ephrussi
- Developmental Biology Unit, European Molecular Biology Laboratory, 69117 Heidelberg, Germany
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167
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Regulation of microtubule stability and organization by mammalian Par3 in specifying neuronal polarity. Dev Cell 2012; 24:26-40. [PMID: 23273878 DOI: 10.1016/j.devcel.2012.11.014] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 10/23/2012] [Accepted: 11/25/2012] [Indexed: 12/26/2022]
Abstract
Polarization of mammalian neurons with a specified axon requires precise regulation of microtubule and actin dynamics in the developing neurites. Here we show that mammalian partition defective 3 (mPar3), a key component of the Par polarity complex that regulates the polarization of many cell types including neurons, directly regulates microtubule stability and organization. The N-terminal portion of mPar3 exhibits strong microtubule binding, bundling, and stabilization activity, which can be suppressed by its C-terminal portion via an intramolecular interaction. Interestingly, the intermolecular oligomerization of mPar3 is able to relieve the intramolecular interaction and thereby promote microtubule bundling and stabilization. Furthermore, disruption of this microtubule regulatory activity of mPar3 impairs its function in axon specification. Together, these results demonstrate a role for mPar3 in directly regulating microtubule organization that is crucial for neuronal polarization.
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168
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Abstract
Epithelial cells are polarized along their apical-basal axis. Much of the cellular machinery that goes into establishing and maintaining epithelial cell polarity is evolutionarily conserved. Model organisms, including the fruit fly, Drosophila melanogaster, are thus particularly useful for the study of cell polarity. Work in Drosophila has identified several important components of the polarity machinery and has also established the surprising existence of a secondary cell polarity pathway required only under conditions of energetic stress. This work has important implications for the understanding of human cancer. Most cancers are epithelial in origin, and the loss of cell polarity is a critical step towards malignancy. Thus a better understanding of how polarity is established and maintained in epithelial cells will help us to understand the process of malignant transformation and may lead to improved therapies. In the present chapter we discuss the current understanding of how epithelial cell polarity is regulated and the known associations between polarity factors and cancer.
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169
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Pénalva C, Mirouse V. Tissue-specific function of Patj in regulating the Crumbs complex and epithelial polarity. Development 2012; 139:4549-54. [PMID: 23136386 DOI: 10.1242/dev.085449] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Patj is described as a core component of the Crumbs complex. Along with the other components, Crumbs and Stardust, Patj has been proposed as essential for epithelial polarity. However, no proper in vivo genetic analysis of Patj function has been performed in any organism. We have generated the first null mutants for Drosophila Patj. These mutants are lethal. However, Patj is not required in all epithelia where the Crumbs complex is essential. Patj is dispensable for ectoderm polarity and embryonic development, whereas more severe defects are observed in the adult follicular epithelium, including mislocalisation of the Crumbs complex from the apical domain, as well as morphogenetic defects. These defects are similar to those observed with crumbs and stardust mutants, although weaker and less frequent. Also, gain-of-function of Crumbs and Patj mutation genetically suppress each other in follicular cells. We also show that the first PDZ domain of Patj associated with the Stardust-binding domain are sufficient to fully rescue both Drosophila viability and Crumbs localisation. We propose that the only crucial function of Patj hinges on the ability of its first two domains to positively regulate the Crumbs complex, defining a new developmental level of regulation of its dynamics.
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Affiliation(s)
- Clothilde Pénalva
- GReD Laboratory, Faculté de Médecine, UMR CNRS 6293, Clermont Université, INSERM U1103, place Henri-Dunant, 63000 Clermont-Ferrand, France
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170
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Yang Z, Xue B, Umitsu M, Ikura M, Muthuswamy SK, Neel BG. The signaling adaptor GAB1 regulates cell polarity by acting as a PAR protein scaffold. Mol Cell 2012; 47:469-83. [PMID: 22883624 DOI: 10.1016/j.molcel.2012.06.037] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2011] [Revised: 05/16/2012] [Accepted: 06/18/2012] [Indexed: 12/21/2022]
Abstract
Cell polarity plays a key role in development and is disrupted in tumors, yet the molecules and mechanisms that regulate polarity remain poorly defined. We found that the scaffolding adaptor GAB1 interacts with two polarity proteins, PAR1 and PAR3. GAB1 binds PAR1 and enhances its kinase activity. GAB1 brings PAR1 and PAR3 into a transient complex, stimulating PAR3 phosphorylation by PAR1. GAB1 and PAR6 bind the PAR3 PDZ1 domain and thereby compete for PAR3 binding. Consequently, GAB1 depletion causes PAR3 hypophosphorylation and increases PAR3/PAR6 complex formation, resulting in accelerated and enhanced tight junction formation, increased transepithelial resistance, and lateral domain shortening. Conversely, GAB1 overexpression, in a PAR1/PAR3-dependent manner, disrupts epithelial apical-basal polarity, promotes multilumen cyst formation, and enhances growth factor-induced epithelial cell scattering. Our results identify GAB1 as a negative regulator of epithelial cell polarity that functions as a scaffold for modulating PAR protein complexes on the lateral membrane.
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Affiliation(s)
- Ziqiang Yang
- Campbell Family Cancer Research Institute, Ontario Cancer Institute, Princess Margaret Cancer Centre, University Health Network, Toronto, ON M5G 2M9, Canada.
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171
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Iden S, van Riel WE, Schäfer R, Song JY, Hirose T, Ohno S, Collard JG. Tumor type-dependent function of the par3 polarity protein in skin tumorigenesis. Cancer Cell 2012; 22:389-403. [PMID: 22975380 DOI: 10.1016/j.ccr.2012.08.004] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 01/31/2012] [Accepted: 08/06/2012] [Indexed: 12/20/2022]
Abstract
Cell polarization is crucial during development and tissue homeostasis and is regulated by conserved proteins of the Scribble, Crumbs, and Par complexes. In mouse skin tumorigenesis, Par3 deficiency results in reduced papilloma formation and growth. Par3 mediates its tumor-promoting activity through regulation of growth and survival, since Par3 deletion increases apoptosis and reduces growth in vivo and in vitro. In contrast, Par3-deficient mice are predisposed to formation of keratoacanthomas, cutaneous tumors thought to originate from different cellular origin and frequently observed in humans. Par3 expression is reduced in both mouse and human keratoacanthomas, indicating tumor-suppressive properties of Par3. Our results identify a dual function of Par3 in skin cancer, with both pro-oncogenic and tumor-suppressive activity depending on the tumor type.
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Affiliation(s)
- Sandra Iden
- Division of Cell Biology I, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.
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172
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Wang C, Shang Y, Yu J, Zhang M. Substrate recognition mechanism of atypical protein kinase Cs revealed by the structure of PKCι in complex with a substrate peptide from Par-3. Structure 2012; 20:791-801. [PMID: 22579248 DOI: 10.1016/j.str.2012.02.022] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2011] [Revised: 02/24/2012] [Accepted: 02/27/2012] [Indexed: 01/24/2023]
Abstract
Protein kinase C (PKC) play critical roles in many cellular functions including differentiation, proliferation, growth, and survival. However, the molecular bases governing PKC's substrate recognitions remain poorly understood. Here we determined the structure of PKCι in complex with a peptide from Par-3 at 2.4 Å. PKCι in the complex adopts catalytically competent, closed conformation without phosphorylation of Thr402 in the activation loop. The Par-3 peptide binds to an elongated groove formed by the N- and C-lobes of the kinase domain. The PKCι/Par-3 complex structure, together with extensive biochemical studies, reveals a set of substrate recognition sites common to all PKC isozymes as well as a hydrophobic pocket unique to aPKC. A consensus aPKC's substrate recognition sequence pattern can be readily identified based on the complex structure. Finally, we demonstrate that the pseudosubstrate sequence of PKCι resembles its substrate sequence, directly binds to and inhibits the activity of the kinase.
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Affiliation(s)
- Chihao Wang
- Division of Life Science, State Key Laboratory of Molecular Neuroscience, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong
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173
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Abstract
Cell polarization is an evolutionarily conserved process that facilitates asymmetric distribution of organelles and proteins and that is modified dynamically during physiological processes such as cell division, migration, and morphogenesis. The plasticity with which cells change their behavior and phenotype in response to cell intrinsic and extrinsic cues is an essential feature of normal physiology. In disease states such as cancer, cells lose their ability to behave normally in response to physiological cues. A molecular understanding of mechanisms that alter the behavior of cancer cells is limited. Cell polarity proteins are a recognized class of molecules that can receive and interpret both intrinsic and extrinsic signals to modulate cell behavior. In this review, we discuss how cell polarity proteins regulate a diverse array of biological processes and how they can contribute to alterations in the behavior of cancer cells.
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Affiliation(s)
- Senthil K Muthuswamy
- Ontario Cancer Institute, Campbell Family Institute for Breast Cancer Research, University of Toronto, Toronto M5G 2M9, Canada.
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174
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Tepass U. The apical polarity protein network in Drosophila epithelial cells: regulation of polarity, junctions, morphogenesis, cell growth, and survival. Annu Rev Cell Dev Biol 2012; 28:655-85. [PMID: 22881460 DOI: 10.1146/annurev-cellbio-092910-154033] [Citation(s) in RCA: 258] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Epithelial tissue formation and function requires the apical-basal polarization of individual epithelial cells. Apical polarity regulators (APRs) are an evolutionarily conserved group of key factors that govern polarity and several other aspects of epithelial differentiation. APRs compose a diverse set of molecules including a transmembrane protein (Crumbs), a serine/threonine kinase (aPKC), a lipid phosphatase (PTEN), a small GTPase (Cdc42), FERM domain proteins (Moesin, Yurt), and several adaptor or scaffolding proteins (Bazooka/Par3, Par6, Stardust, Patj). These proteins form a dynamic cooperative network that is engaged in negative-feedback regulation with basolateral polarity factors to set up the epithelial apical-basal axis. APRs support the formation of the apical junctional complex and the segregation of the junctional domain from the apical membrane. It is becoming increasingly clear that APRs interact with the cytoskeleton and vesicle trafficking machinery, regulate morphogenesis, and modulate epithelial cell growth and survival. Not surprisingly, APRs have multiple fundamental links to human diseases such as cancer and blindness.
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Affiliation(s)
- Ulrich Tepass
- Department of Cell and Systems Biology, University of Toronto, Toronto, Ontario M5S 3G5, Canada.
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175
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Abstract
Epithelial sheets form the basic architectural unit of most tissues and organs. To form complex organs, these sheets are folded and reshaped by cell-shape changes. Reporting recently in Nature, Wang et al. (2012) describe a myosin-independent mechanism that links the regulation of apical-basal polarity to tissue morphogenesis.
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Affiliation(s)
- Kaelyn D Sumigray
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3280, USA
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176
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Yu CG, Harris TJC. Interactions between the PDZ domains of Bazooka (Par-3) and phosphatidic acid: in vitro characterization and role in epithelial development. Mol Biol Cell 2012; 23:3743-53. [PMID: 22833561 PMCID: PMC3442420 DOI: 10.1091/mbc.e12-03-0196] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
The polarity regulator Bazooka (Par-3) is shown to directly bind the signaling lipid phosphatidic acid via its PDZ domains in vitro. In vivo, the interaction appears to support Bazooka functions important for Drosophila embryonic epithelial structure. Thus Bazooka has a closer connection to membrane lipids than previously recognized. Bazooka (Par-3) is a conserved polarity regulator that organizes molecular networks in a wide range of cell types. In epithelia, it functions as a plasma membrane landmark to organize the apical domain. Bazooka is a scaffold protein that interacts with proteins through its three PDZ (postsynaptic density 95, discs large, zonula occludens-1) domains and other regions. In addition, Bazooka has been shown to interact with phosphoinositides. Here we show that the Bazooka PDZ domains interact with the negatively charged phospholipid phosphatidic acid immobilized on solid substrates or in liposomes. The interaction requires multiple PDZ domains, and conserved patches of positively charged amino acid residues appear to mediate the interaction. Increasing or decreasing levels of diacylglycerol kinase or phospholipase D—enzymes that produce phosphatidic acid—reveal a role for phosphatidic acid in Bazooka embryonic epithelial activity but not its localization. Mutating residues implicated in phosphatidic acid binding revealed a possible role in Bazooka localization and function. These data implicate a closer connection between Bazooka and membrane lipids than previously recognized. Bazooka polarity landmarks may be conglomerates of proteins and plasma membrane lipids that modify each other's activities for an integrated effect on cell polarity.
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Affiliation(s)
- Cao Guo Yu
- Department of Cell and Systems Biology, University of Toronto, Toronto, ON, Canada
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177
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Zhou W, Hong Y. Drosophila Patj plays a supporting role in apical-basal polarity but is essential for viability. Development 2012; 139:2891-6. [PMID: 22791898 DOI: 10.1242/dev.083162] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Patj has been characterized as one of the so-called polarity proteins that play essential and conserved roles in regulating cell polarity in many different cell types. Studies of Drosophila and mammalian cells suggest that Patj is required for the apical polarity protein complex Crumbs-Stardust (Pals1 or Mpp5 in mammalian cells) to establish apical-basal polarity. However, owing to the lack of suitable genetic mutants, the exact in vivo function of Patj in regulating apical-basal polarity and development remains to be elucidated. Here, we generated molecularly defined null mutants of Drosophila Patj (dPatj). Our data show conclusively that dPatj only plays supporting and non-essential roles in regulating apical-basal polarity, although such a supporting role may become crucial in cells such as photoreceptors that undergo complex cellular morphogenesis. In addition, our results confirm that dPatj possesses an as yet unidentified function that is essential for pupal development.
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Affiliation(s)
- Wenke Zhou
- Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA
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178
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Regulation of adherens junction dynamics by phosphorylation switches. JOURNAL OF SIGNAL TRANSDUCTION 2012; 2012:125295. [PMID: 22848810 PMCID: PMC3403498 DOI: 10.1155/2012/125295] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 05/21/2012] [Accepted: 05/22/2012] [Indexed: 12/15/2022]
Abstract
Adherens junctions connect the actin cytoskeleton of neighboring cells through transmembrane cadherin receptors and a network of adaptor proteins. The interactions between these adaptors and cadherin as well as the activity of actin regulators localized to adherens junctions are tightly controlled to facilitate cell junction assembly or disassembly in response to changes in external or internal forces and/or signaling. Phosphorylation of tyrosine, serine, or threonine residues acts as a switch on the majority of adherens junction proteins, turning "on" or "off" their interactions with other proteins and/or their enzymatic activity. Here, we provide an overview of the kinases and phosphatases regulating phosphorylation of adherens junction proteins and bring examples of phosphorylation events leading to the assembly or disassembly of adherens junctions, highlighting the important role of phosphorylation switches in regulating their dynamics.
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179
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Cibrián Uhalte E, Kirchner M, Hellwig N, Allen JJ, Donat S, Shokat KM, Selbach M, Abdelilah-Seyfried S. In vivo conditions to identify Prkci phosphorylation targets using the analog-sensitive kinase method in zebrafish. PLoS One 2012; 7:e40000. [PMID: 22768194 PMCID: PMC3386912 DOI: 10.1371/journal.pone.0040000] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2012] [Accepted: 06/04/2012] [Indexed: 12/16/2022] Open
Abstract
Protein kinase C iota is required for various cell biological processes including epithelial tissue polarity and organ morphogenesis. To gain mechanistic insight into different roles of this kinase, it is essential to identify specific substrate proteins in their cellular context. The analog-sensitive kinase method provides a powerful tool for the identification of kinase substrates under in vivo conditions. However, it has remained a major challenge to establish screens based on this method in multicellular model organisms. Here, we report the methodology for in vivo conditions using the analog-sensitive kinase method in a genetically-tractable vertebrate model organism, the zebrafish. With this approach, kinase substrates can uniquely be labeled in the developing zebrafish embryo using bulky ATPγS analogs which results in the thiophosphorylation of substrates. The labeling of kinase substrates with a thiophosphoester epitope differs from phosphoesters that are generated by all other kinases and allows for an enrichment of thiophosphopeptides by immunoaffinity purification. This study provides the foundation for using the analog-sensitive kinase method in the context of complex vertebrate development, physiology, or disease.
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Affiliation(s)
| | | | - Nicole Hellwig
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Jasmina J. Allen
- Howard Hughes Medical Institute, University of California San Francisco, San Francisco, California, United States of America
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, United States of America
| | - Stefan Donat
- Max Delbrück Center for Molecular Medicine, Berlin, Germany
| | - Kevan M. Shokat
- Howard Hughes Medical Institute, University of California San Francisco, San Francisco, California, United States of America
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, California, United States of America
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180
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The BEAF insulator regulates genes involved in cell polarity and neoplastic growth. Dev Biol 2012; 369:124-32. [PMID: 22743648 DOI: 10.1016/j.ydbio.2012.06.013] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 06/01/2012] [Accepted: 06/20/2012] [Indexed: 01/05/2023]
Abstract
Boundary Element Associated Factor-32 (BEAF-32) is an insulator protein predominantly found near gene promoters and thought to play a role in gene expression. We find that mutations in BEAF-32 are lethal, show loss of epithelial morphology in imaginal discs and cause neoplastic growth defects. To investigate the molecular mechanisms underlying this phenotype, we carried out a genome-wide analysis of BEAF-32 localization in wing imaginal disc cells. Mutation of BEAF-32 results in miss-regulation of 3850 genes by at least 1.5-fold, 794 of which are bound by this protein in wing imaginal cells. Up-regulated genes encode proteins involved in cell polarity, cell proliferation and cell differentiation. Among the down-regulated genes are those encoding components of the wingless pathway, which is required for cell differentiation. Miss-regulation of these genes explains the unregulated cell growth and neoplastic phenotypes observed in imaginal tissues of BEAF-32 mutants.
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181
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Abstract
A key function of signal transduction during cell polarization is the creation of spatially segregated regions of the cell cortex that possess different lipid and protein compositions and have distinct functions. Polarity can be initiated spontaneously or in response to signaling inputs from adjacent cells or soluble factors and is stabilized by positive-feedback loops. A conserved group of proteins, the Par proteins, plays a central role in polarity establishment and maintenance in many contexts. These proteins generate and maintain their distinct locations in cells by actively excluding one another from specific regions of the plasma membrane. The Par signaling pathway intersects with multiple other pathways that control cell growth, death, and organization.
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Affiliation(s)
- Luke Martin McCaffrey
- Department of Oncology, Rosalind and Morris Goodman Cancer Research Centre, McGill University, Montreal, Quebec, Canada
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182
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Positive feedback and mutual antagonism combine to polarize Crumbs in the Drosophila follicle cell epithelium. Curr Biol 2012; 22:1116-22. [PMID: 22658591 DOI: 10.1016/j.cub.2012.04.020] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2011] [Revised: 03/06/2012] [Accepted: 04/11/2012] [Indexed: 12/15/2022]
Abstract
Epithelial tissues are composed of polarized cells with distinct apical and basolateral membrane domains. In the Drosophila ovarian follicle cell epithelium, apical membranes are specified by Crumbs (Crb), Stardust (Sdt), and the aPKC-Par6-cdc42 complex. Basolateral membranes are specified by Lethal giant larvae (Lgl), Discs large (Dlg), and Scribble (Scrib). Apical and basolateral determinants are known to act in a mutually antagonistic fashion, but it remains unclear how this interaction generates polarity. We have built a computer model of apicobasal polarity that suggests that the combination of positive feedback among apical determinants plus mutual antagonism between apical and basal determinants is essential for polarization. In agreement with this model, in vivo experiments define a positive feedback loop in which Crb self-recruits via Crb-Crb extracellular domain interactions, recruitment of Sdt-aPKC-Par6-cdc42, aPKC phosphorylation of Crb, and recruitment of Expanded (Ex) and Kibra (Kib) to prevent endocytic removal of Crb from the plasma membrane. Lgl antagonizes the operation of this feedback loop, explaining why apical determinants do not normally spread into the basolateral domain. Once Crb is removed from the plasma membrane, it undergoes recycling via Rab11 endosomes. Our results provide a dynamic model for understanding how epithelial polarity is maintained in Drosophila follicle cells.
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183
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Regulation of epithelial polarity by the E3 ubiquitin ligase Neuralized and the Bearded inhibitors in Drosophila. Nat Cell Biol 2012; 14:467-76. [PMID: 22504274 DOI: 10.1038/ncb2481] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 03/14/2012] [Indexed: 12/17/2022]
Abstract
Understanding how epithelial polarity is established and regulated during tissue morphogenesis is a major issue. Here, we identify a regulatory mechanism important for mesoderm invagination, germ-band extension and transepithelial migration in the Drosophila melanogaster embryo. This mechanism involves the inhibition of the conserved E3 ubiquitin ligase Neuralized by proteins of the Bearded family. First, Bearded mutant embryos exhibited a loss of epithelial polarity associated with an early loss of the apical domain. Bearded regulated epithelial polarity by antagonizing neuralized. Second, repression of Bearded gene expression by Snail was required for the Snail-dependent disassembly of adherens junctions in the mesoderm. Third, neuralized was strictly required to promote the downregulation of the apical domain in the midgut epithelium and to facilitate the transepithelial migration of primordial germ cells across this epithelium. This function of Neuralized was independent of its known role in Notch signalling. Thus, Neuralized has two distinct functions in epithelial cell polarity and Notch signalling.
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184
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Wang YC, Khan Z, Kaschube M, Wieschaus EF. Differential positioning of adherens junctions is associated with initiation of epithelial folding. Nature 2012; 484:390-3. [PMID: 22456706 PMCID: PMC3597240 DOI: 10.1038/nature10938] [Citation(s) in RCA: 119] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Accepted: 02/09/2012] [Indexed: 12/30/2022]
Abstract
During tissue morphogenesis, simple epithelial sheets undergo folding to form complex structures. The prevailing model underlying epithelial folding involves cell shape changes driven by Myosin-dependent apical constriction1. Here we describe an alternative mechanism that requires differential positioning of adherens junctions controlled by modulation of epithelial apical-basal polarity. Using live embryo imaging, we show that prior to the initiation of dorsal transverse folds during Drosophila gastrulation, adherens junctions shift basally in the initiating cells, but maintain their original subapical positioning in the neighboring cells. Junctional positioning in the dorsal epithelium depends on the polarity proteins Bazooka and Par-1. In particular, the basal shift that occurs in the initiating cells is associated with a progressive decrease in Par-1 levels. We show that uniform reduction of the activity of Bazooka or Par-1 results in uniform apical or lateral positioning of junctions and in each case dorsal fold initiation is abolished. In addition, an increase in the Bazooka/Par-1 ratio causes formation of ectopic dorsal folds. The basal shift of junctions not only alters the apical shape of the initiating cells, but also forces the lateral membrane of the adjacent cells to bend toward the initiating cells, thereby facilitating tissue deformation. Our data thus establish a direct link between modification of epithelial polarity and initiation of epithelial folding.
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Affiliation(s)
- Yu-Chiun Wang
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
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185
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Ellenbroek SIJ, Iden S, Collard JG. Cell polarity proteins and cancer. Semin Cancer Biol 2012; 22:208-15. [PMID: 22465739 DOI: 10.1016/j.semcancer.2012.02.012] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2011] [Revised: 02/27/2012] [Accepted: 02/28/2012] [Indexed: 01/06/2023]
Abstract
Cell polarity is essential in many biological processes and required for development as well as maintenance of tissue integrity. Loss of polarity is considered both a hallmark and precondition for human cancer. Three conserved polarity protein complexes regulate different modes of polarity that are conserved throughout numerous cell types and species. These complexes are the Crumbs, Par and Scribble complex. Given the importance of cell polarity for normal tissue homeostasis, aberrant polarity signaling is suggested to contribute to the multistep processes of human cancer. Most human cancers are formed from epithelial cells. Evidence confirming the roles for polarity proteins in different phases of the oncogenic trajectory comes from functional studies using mammalian cells as well as Drosophila and zebrafish models. Furthermore, several reports have revealed aberrant expression and localization of polarity proteins in different human tumors. In this review we will give an overview on the current data available that couple polarity signaling to tumorigenesis, particularly in epithelial cells.
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Affiliation(s)
- Saskia I J Ellenbroek
- Division of Cell Biology I, The Netherlands Cancer Institute, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands
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186
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Iden S, Misselwitz S, Peddibhotla SSD, Tuncay H, Rehder D, Gerke V, Robenek H, Suzuki A, Ebnet K. aPKC phosphorylates JAM-A at Ser285 to promote cell contact maturation and tight junction formation. ACTA ACUST UNITED AC 2012; 196:623-39. [PMID: 22371556 PMCID: PMC3307692 DOI: 10.1083/jcb.201104143] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
The PAR-3-atypical protein kinase C (aPKC)-PAR-6 complex has been implicated in the development of apicobasal polarity and the formation of tight junctions (TJs) in vertebrate epithelial cells. It is recruited by junctional adhesion molecule A (JAM-A) to primordial junctions where aPKC is activated by Rho family small guanosine triphosphatases. In this paper, we show that aPKC can interact directly with JAM-A in a PAR-3-independent manner. Upon recruitment to primordial junctions, aPKC phosphorylates JAM-A at S285 to promote the maturation of immature cell-cell contacts. In fully polarized cells, S285-phosphorylated JAM-A is localized exclusively at the TJs, and S285 phosphorylation of JAM-A is required for the development of a functional epithelial barrier. Protein phosphatase 2A dephosphorylates JAM-A at S285, suggesting that it antagonizes the activity of aPKC. Expression of nonphosphorylatable JAM-A/S285A interferes with single lumen specification during cyst development in three-dimensional culture. Our data suggest that aPKC phosphorylates JAM-A at S285 to regulate cell-cell contact maturation, TJ formation, and single lumen specification.
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Affiliation(s)
- Sandra Iden
- Institute-associated Research Group: Cell adhesion and cell polarity, University Münster, 48419 Münster, Germany
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187
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McKinley RFA, Yu CG, Harris TJC. Assembly of Bazooka polarity landmarks through a multifaceted membrane-association mechanism. J Cell Sci 2012; 125:1177-90. [PMID: 22303000 DOI: 10.1242/jcs.091884] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Epithelial cell polarity is essential for animal development. The scaffold protein Bazooka (Baz/PAR-3) forms apical polarity landmarks to organize epithelial cells. However, it is unclear how Baz is recruited to the plasma membrane and how this is coupled with downstream effects. Baz contains an oligomerization domain, three PDZ domains, and binding regions for the protein kinase aPKC and phosphoinositide lipids. With a structure-function approach, we dissected the roles of these domains in the localization and function of Baz in the Drosophila embryonic ectoderm. We found that a multifaceted membrane association mechanism localizes Baz to the apical circumference. Although none of the Baz protein domains are essential for cortical localization, we determined that each contributes to cortical anchorage in a specific manner. We propose that the redundancies involved might provide plasticity and robustness to Baz polarity landmarks. We also identified specific downstream effects, including the promotion of epithelial structure, a positive-feedback loop that recruits aPKC, PAR-6 and Crumbs, and a negative-feedback loop that regulates Baz.
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Affiliation(s)
- R F Andrew McKinley
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
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188
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Guilgur LG, Prudêncio P, Ferreira T, Pimenta-Marques AR, Martinho RG. Drosophila aPKC is required for mitotic spindle orientation during symmetric division of epithelial cells. Development 2012; 139:503-13. [DOI: 10.1242/dev.071027] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Epithelial cells mostly orient the spindle along the plane of the epithelium (planar orientation) for mitosis to produce two identical daughter cells. The correct orientation of the spindle relies on the interaction between cortical polarity components and astral microtubules. Recent studies in mammalian tissue culture cells suggest that the apically localised atypical protein kinase C (aPKC) is important for the planar orientation of the mitotic spindle in dividing epithelial cells. Yet, in chicken neuroepithelial cells, aPKC is not required in vivo for spindle orientation, and it has been proposed that the polarization cues vary between different epithelial cell types and/or developmental processes. In order to investigate whether Drosophila aPKC is required for spindle orientation during symmetric division of epithelial cells, we took advantage of a previously isolated temperature-sensitive allele of aPKC. We showed that Drosophila aPKC is required in vivo for spindle planar orientation and apical exclusion of Pins (Raps). This suggests that the cortical cues necessary for spindle orientation are not only conserved between Drosophila and mammalian cells, but are also similar to those required for spindle apicobasal orientation during asymmetric cell division.
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Affiliation(s)
- Leonardo G. Guilgur
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, Oeiras 2781-901, Portugal
| | - Pedro Prudêncio
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, Oeiras 2781-901, Portugal
| | - Tânia Ferreira
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, Oeiras 2781-901, Portugal
| | | | - Rui Gonçalo Martinho
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, Oeiras 2781-901, Portugal
- Regenerative Medicine Program, Departamento de Ciências Biomédicas e Medicina, and IBB-Institute for Biotechnology and Bioengineering, Centro de Biomedicina Molecular e Estrutural, Universidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal
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189
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Harris TJ. Adherens Junction Assembly and Function in the Drosophila Embryo. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 293:45-83. [DOI: 10.1016/b978-0-12-394304-0.00007-5] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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190
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Abstract
Caenorhabditis elegans provides a simplified, in vivo model system in which to study adherens junctions (AJs) and their role in morphogenesis. The core AJ components-HMR-1/E-cadherin, HMP-2/β-catenin and HMP-1/α-catenin-were initially identified through genetic screens for mutants with body axis elongation defects. In early embryos, AJ proteins are found at sites of contact between blastomeres, and in epithelial cells AJ proteins localize to the multifaceted apical junction (CeAJ)-a single structure that combines the adhesive and barrier functions of vertebrate adherens and tight junctions. The apically localized polarity proteins PAR-3 and PAR-6 mediate formation and maturation of junctions, while the basolaterally localized regulator LET-413/Scribble ensures that junctions remain apically positioned. AJs promote robust adhesion between epithelial cells and provide mechanical resistance for the physical strains of morphogenesis. However, in contrast to vertebrates, C. elegans AJ proteins are not essential for general cell adhesion or for epithelial cell polarization. A combination of conserved and novel proteins localizes to the CeAJ and works together with AJ proteins to mediate adhesion.
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191
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Abstract
After years of extensive scientific discovery much has been learned about the networks that regulate epithelial homeostasis. Loss of expression or functional activity of cell adhesion and cell polarity proteins (including the PAR, crumbs (CRB) and scribble (SCRIB) complexes) is intricately related to advanced stages of tumour progression and invasiveness. But the key roles of these proteins in crosstalk with the Hippo and liver kinase B1 (LKB1)-AMPK pathways and in epithelial function and proliferation indicate that they may also be associated with the early stages of tumorigenesis. For example, deregulation of adhesion and polarity proteins can cause misoriented cell divisions and increased self-renewal of adult epithelial stem cells. In this Review, we highlight some advances in the understanding of how loss of epithelial cell polarity contributes to tumorigenesis.
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Affiliation(s)
- Fernando Martin-Belmonte
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Madrid 28049, Spain.
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192
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Muschalik N, Knust E. Increased levels of the cytoplasmic domain of Crumbs repolarise developing Drosophila photoreceptors. J Cell Sci 2011; 124:3715-25. [PMID: 22025631 DOI: 10.1242/jcs.091223] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Photoreceptor morphogenesis in Drosophila requires remodelling of apico-basal polarity and adherens junctions (AJs), and includes cell shape changes, as well as differentiation and expansion of the apical membrane. The evolutionarily conserved transmembrane protein Crumbs (Crb) organises an apical membrane-associated protein complex that controls photoreceptor morphogenesis. Expression of the small cytoplasmic domain of Crb in crb mutant photoreceptor cells (PRCs) rescues the crb mutant phenotype to the same extent as the full-length protein. Here, we show that overexpression of the membrane-tethered cytoplasmic domain of Crb in otherwise wild-type photoreceptor cells has major effects on polarity and morphogenesis. Whereas early expression causes severe abnormalities in apico-basal polarity and ommatidial integrity, expression at later stages affects the shape and positioning of AJs. This result supports the importance of Crb for junctional remodelling during morphogenetic changes. The most pronounced phenotype observed upon early expression is the formation of ectopic apical membrane domains, which often develop into a complete second apical pole, including ectopic AJs. Induction of this phenotype requires members of the Par protein network. These data point to a close integration of the Crb complex and Par proteins during photoreceptor morphogenesis and underscore the role of Crb as an apical determinant.
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Affiliation(s)
- Nadine Muschalik
- Max-Planck-Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307-Dresden, Germany
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193
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Dickinson DJ, Weis WI, Nelson WJ. Protein evolution in cell and tissue development: going beyond sequence and transcriptional analysis. Dev Cell 2011; 21:32-4. [PMID: 21763606 DOI: 10.1016/j.devcel.2011.06.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Studies of animal evolution often focus on sequence and transcriptional analysis, based on an assumption that the evolution of development is driven by changes in gene expression. We argue that biochemical and cell biological approaches are also required, because sequence-conserved proteins can have different biochemical, cellular, and developmental properties.
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194
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St Johnston D, Sanson B. Epithelial polarity and morphogenesis. Curr Opin Cell Biol 2011; 23:540-6. [PMID: 21807488 DOI: 10.1016/j.ceb.2011.07.005] [Citation(s) in RCA: 110] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2011] [Revised: 07/07/2011] [Accepted: 07/07/2011] [Indexed: 12/19/2022]
Affiliation(s)
- Daniel St Johnston
- The Gurdon Institute and the Department of Genetics, University of Cambridge, Tennis Court Rd, Cambridge CB2 1QN, United Kingdom.
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195
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Laprise P. Emerging role for epithelial polarity proteins of the Crumbs family as potential tumor suppressors. J Biomed Biotechnol 2011; 2011:868217. [PMID: 21912482 PMCID: PMC3168773 DOI: 10.1155/2011/868217] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2011] [Accepted: 07/09/2011] [Indexed: 12/21/2022] Open
Abstract
Defects in apical-basal polarity regulation are associated with tissue overgrowth and tumorogenesis, yet the molecular mechanisms linking epithelial polarity regulators to hyperplasia or neoplasia remain elusive. In addition, exploration of the expression and function of the full complement of proteins required for the polarized architecture of epithelial cells in the context of cancer is awaited. This paper provides an overview of recent studies performed on Drosophila and vertebrates showing that apical polarity proteins of the Crumbs family act to repress tissue growth and epithelial to mesenchymal transition. Thus, these proteins emerge as potential tumor suppressors. Interestingly, analysis of the molecular function of Crumbs proteins reveals a function for these polarity regulators in junctional complexes stability and control of signaling pathways regulating proliferation and apoptosis. Thereby, these studies provide a molecular basis explaining how regulation of epithelial polarity is coupled to tumorogenesis.
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Affiliation(s)
- Patrick Laprise
- Department of Molecular Biology, Medical Biochemistry and Pathology/Cancer Research Center, Laval University and CRCHUQ-Hôtel-Dieu de Québec, 9 McMahon, Québec, QC, Canada G1R 2J6.
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196
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Abstract
Inositol phospholipids have been implicated in almost all aspects of cellular physiology including spatiotemporal regulation of cellular signaling, acquisition of cellular polarity, specification of membrane identity, cytoskeletal dynamics, and regulation of cellular adhesion, motility, and cytokinesis. In this review, we examine the critical role phosphoinositides play in these processes to execute the establishment and maintenance of cellular architecture. Epithelial tissues perform essential barrier and transport functions in almost all major organs. Key to their development and function is the establishment of epithelial cell polarity. We place a special emphasis on highlighting recent studies demonstrating phosphoinositide regulation of epithelial cell polarity and how individual cells use phosphoinositides to further organize into epithelial tissues.
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Affiliation(s)
- Annette Shewan
- Department of Anatomy, University of California, San Francisco, San Francisco, California 94143-2140, USA
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197
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A novel function for the PAR complex in subcellular morphogenesis of tracheal terminal cells in Drosophila melanogaster. Genetics 2011; 189:153-64. [PMID: 21750259 DOI: 10.1534/genetics.111.130351] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The processes that generate cellular morphology are not well understood. To investigate this problem, we use Drosophila melanogaster tracheal terminal cells, which undergo two distinct morphogenetic processes: subcellular branching morphogenesis and subcellular apical lumen formation. Here we show these processes are regulated by components of the PAR-polarity complex. This complex, composed of the proteins Par-6, Bazooka (Par-3), aPKC, and Cdc42, is best known for roles in asymmetric cell division and apical/basal polarity. We find Par-6, Bazooka, and aPKC, as well as known interactions between them, are required for subcellular branch initiation, but not for branch outgrowth. By analysis of single and double mutants, and isolation of two novel alleles of Par-6, one of which specifically truncates the Par-6 PDZ domain, we conclude that dynamic interactions between apical PAR-complex members control the branching pattern of terminal cells. These data suggest that canonical apical PAR-complex activity is required for subcellular branching morphogenesis. In addition, we find the PAR proteins are downstream of the FGF pathway that controls terminal cell branching. In contrast, we find that while Par-6 and aPKC are both required for subcellular lumen formation, neither Bazooka nor a direct interaction between Par-6 and aPKC is needed for this process. Thus a novel, noncanonical role for the polarity proteins Par-6 and aPKC is used in formation of this subcellular apical compartment. Our results demonstrate that proteins from the PAR complex can be deployed independently within a single cell to control two different morphogenetic processes.
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198
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Abstract
The asymmetric polarization of cells allows specialized functions to be performed at discrete subcellular locales. Spatiotemporal coordination of polarization between groups of cells allowed the evolution of metazoa. For instance, coordinated apical-basal polarization of epithelial and endothelial cells allows transport of nutrients and metabolites across cell barriers and tissue microenvironments. The defining feature of such tissues is the presence of a central, interconnected luminal network. Although tubular networks are present in seemingly different organ systems, such as the kidney, lung, and blood vessels, common underlying principles govern their formation. Recent studies using in vivo and in vitro models of lumen formation have shed new light on the molecular networks regulating this fundamental process. We here discuss progress in understanding common design principles underpinning de novo lumen formation and expansion.
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199
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Laprise P, Tepass U. Novel insights into epithelial polarity proteins in Drosophila. Trends Cell Biol 2011; 21:401-8. [DOI: 10.1016/j.tcb.2011.03.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2011] [Revised: 03/18/2011] [Accepted: 03/21/2011] [Indexed: 01/04/2023]
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200
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Retromer controls epithelial cell polarity by trafficking the apical determinant Crumbs. Curr Biol 2011; 21:1111-7. [PMID: 21700461 DOI: 10.1016/j.cub.2011.05.007] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 04/20/2011] [Accepted: 05/05/2011] [Indexed: 11/22/2022]
Abstract
The evolutionarily conserved apical determinant Crumbs (Crb) is essential for maintaining apicobasal polarity and integrity of many epithelial tissues [1]. Crb levels are crucial for cell polarity and homeostasis, yet strikingly little is known about its trafficking or the mechanism of its apical localization. Using a newly established, liposome-based system described here, we determined Crb to be an interaction partner and cargo of the retromer complex. Retromer is essential for the retrograde transport of numerous transmembrane proteins from endosomes to the trans-Golgi network (TGN) and is conserved between plants, fungi, and animals [2]. We show that loss of retromer function results in a substantial reduction of Crb in Drosophila larvae, wing discs, and the follicle epithelium. Moreover, loss of retromer phenocopies loss of crb by preventing apical localization of key polarity molecules, such as atypical protein kinase C (aPKC) and Par6 in the follicular epithelium, an effect that can be rescued by overexpression of Crb. Additionally, loss of retromer results in multilayering of the follicular epithelium, indicating that epithelial integrity is severely compromised. Our data reveal a mechanism for Crb trafficking by retromer that is vital for maintaining Crb levels and localization. We also show a novel function for retromer in maintaining epithelial cell polarity.
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