1
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Deutz LN, Sarıkaya S, Dickinson DJ. Membrane extraction in native lipid nanodiscs reveals dynamic regulation of Cdc42 complexes during cell polarization. Biophys J 2023:S0006-3495(23)00721-X. [PMID: 38006206 DOI: 10.1016/j.bpj.2023.11.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2023] [Revised: 10/13/2023] [Accepted: 11/21/2023] [Indexed: 11/26/2023] Open
Abstract
Embryonic development requires the establishment of cell polarity to enable cell fate segregation and tissue morphogenesis. This process is regulated by Par complex proteins, which partition into polarized membrane domains and direct downstream polarized cell behaviors. The kinase aPKC (along with its cofactor Par6) is a key member of this network and can be recruited to the plasma membrane by either the small GTPase Cdc42 or the scaffolding protein Par3. Although in vitro interactions among these proteins are well established, much is still unknown about the complexes they form during development. Here, to enable the study of membrane-associated complexes ex vivo, we used a maleic acid copolymer to rapidly isolate membrane proteins from single C. elegans zygotes into lipid nanodiscs. We show that native lipid nanodisc formation enables detection of endogenous complexes involving Cdc42, which are undetectable when cells are lysed in detergent. We found that Cdc42 interacts more strongly with aPKC/Par6 during polarity maintenance than polarity establishment, two developmental stages that are separated by only a few minutes. We further show that Cdc42 and Par3 do not bind aPKC/Par6 simultaneously, confirming recent in vitro findings in an ex vivo context. Our findings establish a new tool for studying membrane-associated signaling complexes and reveal an unexpected mode of polarity regulation via Cdc42.
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Affiliation(s)
- Lars N Deutz
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas
| | - Sena Sarıkaya
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas
| | - Daniel J Dickinson
- Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas.
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2
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Packer J, Gubieda AG, Brooks A, Deutz LN, Squires I, Ellison S, Naganathan SR, Wollman AJ, Dickinson DJ, Rodriguez J. Atypical Protein Kinase C Promotes its own Asymmetric Localisation by Phosphorylating Cdc42 in Polarising Cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.27.563985. [PMID: 38009101 PMCID: PMC10675845 DOI: 10.1101/2023.10.27.563985] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/28/2023]
Abstract
Atypical protein kinase C (aPKC) is a major regulator of cell polarity. Acting in conjunction with Par6, Par3 and the small GTPase Cdc42, aPKC becomes asymmetrically localised and drives the polarisation of cells. aPKC activity is crucial for its own asymmetric localisation, suggesting a hitherto unknown feedback mechanism contributing to polarisation. Here we show in C. elegans zygotes that the feedback relies on CDC-42 phosphorylation at serine 71 by aPKC, which in turn results in aPKC dissociation from CDC-42. The dissociated aPKC then associates with PAR-3 clusters, which are transported anteriorly by actomyosin-based cortical flow. Moreover, the turnover of aPKC-mediated CDC-42 phosphorylation regulates the organisation of the actomyosin cortex that drives aPKC asymmetry. Given the widespread role of aPKC and Cdc42 in cell polarity, this form of self-regulation of aPKC may be vital for the robust polarisation of many cell types.
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Affiliation(s)
- John Packer
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- These authors contributed equally
| | - Alicia G. Gubieda
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- These authors contributed equally
| | - Aaron Brooks
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- These authors contributed equally
| | - Lars N. Deutz
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas, USA
- These authors contributed equally
| | - Iolo Squires
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- These authors contributed equally
| | | | - Sundar Ram Naganathan
- Department of Biological Sciences, Tata Institute of Fundamental Research, Mumbai 400005, India
| | - Adam J.M. Wollman
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
| | - Daniel J. Dickinson
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas, USA
| | - Josana Rodriguez
- Newcastle University Biosciences Institute, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
- Lead contact
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3
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Vargas E, Prehoda KE. Negative cooperativity underlies dynamic assembly of the Par complex regulators Cdc42 and Par-3. J Biol Chem 2023; 299:102749. [PMID: 36436559 PMCID: PMC9793311 DOI: 10.1016/j.jbc.2022.102749] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 11/15/2022] [Accepted: 11/16/2022] [Indexed: 11/26/2022] Open
Abstract
The Par complex polarizes diverse animal cells through the concerted action of multiple regulators. Binding to the multi-PDZ domain containing protein Par-3 couples the complex to cortical flows that construct the Par membrane domain. Once localized properly, the complex is thought to transition from Par-3 to the Rho GTPase Cdc42 to activate the complex. While this transition is a critical step in Par-mediated polarity, little is known about how it occurs. Here, we used a biochemical reconstitution approach with purified, intact Par complex and qualitative binding assays and found that Par-3 and Cdc42 exhibit strong negative cooperativity for the Par complex. The energetic coupling arises from interactions between the second and third PDZ protein interaction domains of Par-3 and the aPKC Kinase-PBM (PDZ binding motif) that mediate the displacement of Cdc42 from the Par complex. Our results indicate that Par-3, Cdc42, Par-6, and aPKC are the minimal components that are sufficient for this transition to occur and that no external factors are required. Our findings provide the mechanistic framework for understanding a critical step in the regulation of Par complex polarization and activity.
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Affiliation(s)
- Elizabeth Vargas
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, Eugene, Oregon, USA
| | - Kenneth E Prehoda
- Department of Chemistry and Biochemistry, Institute of Molecular Biology, Eugene, Oregon, USA.
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4
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Energetic determinants of animal cell polarity regulator Par-3 interaction with the Par complex. J Biol Chem 2022; 298:102223. [PMID: 35787373 PMCID: PMC9352551 DOI: 10.1016/j.jbc.2022.102223] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 06/21/2022] [Accepted: 06/22/2022] [Indexed: 12/03/2022] Open
Abstract
The animal cell polarity regulator Par-3 recruits the Par complex (consisting of Par-6 and atypical PKC, aPKC) to specific sites on the cell membrane. Although numerous physical interactions have been reported between Par-3 and the Par complex, it is unclear how each of these interactions contributes to the overall binding. Using a purified, intact Par complex and a quantitative binding assay, here, we found that the energy required for this interaction is provided by the second and third PDZ protein interaction domains of Par-3. We show that both Par-3 PDZ domains bind to the PDZ-binding motif of aPKC in the Par complex, with additional binding energy contributed from the adjacent catalytic domain of aPKC. In addition to highlighting the role of Par-3 PDZ domain interactions with the aPKC kinase domain and PDZ-binding motif in stabilizing Par-3–Par complex assembly, our results indicate that each Par-3 molecule can potentially recruit two Par complexes to the membrane during cell polarization. These results provide new insights into the energetic determinants and structural stoichiometry of the Par-3–Par complex assembly.
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5
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Kroll JR, Remmelzwaal S, Boxem M. CeLINC, a fluorescence-based protein-protein interaction assay in Caenorhabditis elegans. Genetics 2021; 219:6380436. [PMID: 34849800 PMCID: PMC8664570 DOI: 10.1093/genetics/iyab163] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 09/22/2021] [Indexed: 11/30/2022] Open
Abstract
Interactions among proteins are fundamental for life and determining whether two particular proteins physically interact can be essential for fully understanding a protein’s function. We present Caenorhabditis elegans light-induced coclustering (CeLINC), an optical binary protein–protein interaction assay to determine whether two proteins interact in vivo. Based on CRY2/CIB1 light-dependent oligomerization, CeLINC can rapidly and unambiguously identify protein–protein interactions between pairs of fluorescently tagged proteins. A fluorescently tagged bait protein is captured using a nanobody directed against the fluorescent protein (GFP or mCherry) and brought into artificial clusters within the cell. Colocalization of a fluorescently tagged prey protein in the cluster indicates a protein interaction. We tested the system with an array of positive and negative reference protein pairs. Assay performance was extremely robust with no false positives detected in the negative reference pairs. We then used the system to test for interactions among apical and basolateral polarity regulators. We confirmed interactions seen between PAR-6, PKC-3, and PAR-3, but observed no physical interactions among the basolateral Scribble module proteins LET-413, DLG-1, and LGL-1. We have generated a plasmid toolkit that allows use of custom promoters or CRY2 variants to promote flexibility of the system. The CeLINC assay is a powerful and rapid technique that can be widely applied in C. elegans due to the universal plasmids that can be used with existing fluorescently tagged strains without need for additional cloning or genetic modification of the genome.
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Affiliation(s)
- Jason R Kroll
- Division of Developmental Biology, Department of Biology, Faculty of Science, Institute of Biodynamics and Biocomplexity, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Sanne Remmelzwaal
- Division of Developmental Biology, Department of Biology, Faculty of Science, Institute of Biodynamics and Biocomplexity, Utrecht University, 3584 CH Utrecht, the Netherlands
| | - Mike Boxem
- Division of Developmental Biology, Department of Biology, Faculty of Science, Institute of Biodynamics and Biocomplexity, Utrecht University, 3584 CH Utrecht, the Netherlands
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6
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Sarıkaya S, Dickinson DJ. Rapid extraction and kinetic analysis of protein complexes from single cells. Biophys J 2021; 120:5018-5031. [PMID: 34653388 PMCID: PMC8633716 DOI: 10.1016/j.bpj.2021.10.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2021] [Revised: 09/22/2021] [Accepted: 10/08/2021] [Indexed: 11/22/2022] Open
Abstract
Proteins contribute to cell biology by forming dynamic, regulated interactions, and measuring these interactions is a foundational approach in biochemistry. We present a rapid, quantitative in vivo assay for protein-protein interactions, based on optical cell lysis followed by time-resolved single-molecule analysis of protein complex binding to an antibody-coated substrate. We show that our approach has better reproducibility, higher dynamic range, and lower background than previous single-molecule pull-down assays. Furthermore, we demonstrate that by monitoring cellular protein complexes over time after cell lysis, we can measure the dissociation rate constant of a cellular protein complex, providing information about binding affinity and kinetics. Our dynamic single-cell, single-molecule pull-down method thus approaches the biochemical precision that is often sought from in vitro assays while being applicable to native protein complexes isolated from single cells in vivo.
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Affiliation(s)
- Sena Sarıkaya
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas
| | - Daniel J Dickinson
- Department of Molecular Biosciences, University of Texas at Austin, Austin, Texas.
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7
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Castiglioni VG, Pires HR, Rosas Bertolini R, Riga A, Kerver J, Boxem M. Epidermal PAR-6 and PKC-3 are essential for larval development of C. elegans and organize non-centrosomal microtubules. eLife 2020; 9:e62067. [PMID: 33300872 PMCID: PMC7755398 DOI: 10.7554/elife.62067] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Accepted: 12/09/2020] [Indexed: 12/17/2022] Open
Abstract
The cortical polarity regulators PAR-6, PKC-3, and PAR-3 are essential for the polarization of a broad variety of cell types in multicellular animals. In C. elegans, the roles of the PAR proteins in embryonic development have been extensively studied, yet little is known about their functions during larval development. Using inducible protein degradation, we show that PAR-6 and PKC-3, but not PAR-3, are essential for postembryonic development. PAR-6 and PKC-3 are required in the epidermal epithelium for animal growth, molting, and the proper pattern of seam-cell divisions. Finally, we uncovered a novel role for PAR-6 in organizing non-centrosomal microtubule arrays in the epidermis. PAR-6 was required for the localization of the microtubule organizer NOCA-1/Ninein, and defects in a noca-1 mutant are highly similar to those caused by epidermal PAR-6 depletion. As NOCA-1 physically interacts with PAR-6, we propose that PAR-6 promotes non-centrosomal microtubule organization through localization of NOCA-1/Ninein.
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Affiliation(s)
- Victoria G Castiglioni
- Division of Developmental Biology, Institute of Biodynamics and Biocomplexity, Department of Biology, Faculty of Science, Utrecht UniversityUtrechtNetherlands
| | - Helena R Pires
- Division of Developmental Biology, Institute of Biodynamics and Biocomplexity, Department of Biology, Faculty of Science, Utrecht UniversityUtrechtNetherlands
| | - Rodrigo Rosas Bertolini
- Division of Developmental Biology, Institute of Biodynamics and Biocomplexity, Department of Biology, Faculty of Science, Utrecht UniversityUtrechtNetherlands
| | - Amalia Riga
- Division of Developmental Biology, Institute of Biodynamics and Biocomplexity, Department of Biology, Faculty of Science, Utrecht UniversityUtrechtNetherlands
| | - Jana Kerver
- Division of Developmental Biology, Institute of Biodynamics and Biocomplexity, Department of Biology, Faculty of Science, Utrecht UniversityUtrechtNetherlands
| | - Mike Boxem
- Division of Developmental Biology, Institute of Biodynamics and Biocomplexity, Department of Biology, Faculty of Science, Utrecht UniversityUtrechtNetherlands
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8
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Holly RW, Jones K, Prehoda KE. A Conserved PDZ-Binding Motif in aPKC Interacts with Par-3 and Mediates Cortical Polarity. Curr Biol 2020; 30:893-898.e5. [PMID: 32084408 DOI: 10.1016/j.cub.2019.12.055] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 11/20/2019] [Accepted: 12/18/2019] [Indexed: 10/25/2022]
Abstract
Par-3 regulates animal cell polarity by targeting the Par complex proteins Par-6 and atypical protein kinase C (aPKC) to specific cortical sites. Although numerous physical interactions between Par-3 and the Par complex have been identified [1-6], we discovered a novel interaction between Par-3's second PDZ domain and a highly conserved aPKC PDZ-binding motif (PBM) that is required in the context of the full-length, purified Par-6-aPKC complex. We also found that Par-3 is phosphorylated by the full Par complex and phosphorylation induces dissociation of the Par-3 phosphorylation site from aPKC's kinase domain but does not disrupt the Par-3 PDZ2-aPKC PBM interaction. In asymmetrically dividing Drosophila neuroblasts, the aPKC PBM is required for cortical targeting, consistent with its role in mediating a persistent interaction with Par-3. Our results define a physical connection that targets the Par complex to polarized sites on the cell membrane.
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Affiliation(s)
- Ryan W Holly
- Institute of Molecular Biology, Department of Chemistry and Biochemistry, 1229 University of Oregon, Eugene, OR 97403, USA
| | - Kimberly Jones
- Institute of Molecular Biology, Department of Chemistry and Biochemistry, 1229 University of Oregon, Eugene, OR 97403, USA
| | - Kenneth E Prehoda
- Institute of Molecular Biology, Department of Chemistry and Biochemistry, 1229 University of Oregon, Eugene, OR 97403, USA.
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9
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The Role of pkc-3 and Genetic Suppressors in Caenorhabditis elegans Epithelial Cell Junction Formation. Genetics 2020; 214:941-959. [PMID: 32005655 DOI: 10.1534/genetics.120.303085] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2019] [Accepted: 01/29/2020] [Indexed: 12/20/2022] Open
Abstract
Epithelial cells form intercellular junctions to strengthen cell-cell adhesion and limit diffusion, allowing epithelia to function as dynamic tissues and barriers separating internal and external environments. Junctions form as epithelial cells differentiate; clusters of junction proteins first concentrate apically, then mature into continuous junctional belts that encircle and connect each cell. In mammals and Drosophila, atypical protein kinase C (aPKC) is required for junction maturation, although how it contributes to this process is poorly understood. A role for the Caenorhabditis elegans aPKC homolog PKC-3 in junction formation has not been described previously. Here, we show that PKC-3 is essential for junction maturation as epithelia first differentiate. Using a temperature-sensitive allele of pkc-3 that causes junction breaks in the spermatheca and leads to sterility, we identify intragenic and extragenic suppressors that render pkc-3 mutants fertile. Intragenic suppressors include an unanticipated stop-to-stop mutation in the pkc-3 gene, providing evidence for the importance of stop codon identity in gene activity. One extragenic pkc-3 suppressor is a loss-of-function allele of the lethal(2) giant larvae homolog lgl-1, which antagonizes aPKC within epithelia of Drosophila and mammals, but was not known previously to function in C. elegans epithelia. Finally, two extragenic suppressors are loss-of-function alleles of sups-1-a previously uncharacterized gene. We show that SUPS-1 is an apical extracellular matrix protein expressed in epidermal cells, suggesting that it nonautonomously regulates junction formation in the spermatheca. These findings establish a foundation for dissecting the role of PKC-3 and interacting genes in epithelial junction maturation.
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10
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Geßele R, Halatek J, Würthner L, Frey E. Geometric cues stabilise long-axis polarisation of PAR protein patterns in C. elegans. Nat Commun 2020; 11:539. [PMID: 31988277 PMCID: PMC6985163 DOI: 10.1038/s41467-020-14317-w] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 12/16/2019] [Indexed: 12/21/2022] Open
Abstract
In the Caenorhabditis elegans zygote, PAR protein patterns, driven by mutual anatagonism, determine the anterior-posterior axis and facilitate the redistribution of proteins for the first cell division. Yet, the factors that determine the selection of the polarity axis remain unclear. We present a reaction-diffusion model in realistic cell geometry, based on biomolecular reactions and accounting for the coupling between membrane and cytosolic dynamics. We find that the kinetics of the phosphorylation-dephosphorylation cycle of PARs and the diffusive protein fluxes from the cytosol towards the membrane are crucial for the robust selection of the anterior-posterior axis for polarisation. The local ratio of membrane surface to cytosolic volume is the main geometric cue that initiates pattern formation, while the choice of the long-axis for polarisation is largely determined by the length of the aPAR-pPAR interface, and mediated by processes that minimise the diffusive fluxes of PAR proteins between cytosol and membrane.
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Affiliation(s)
- Raphaela Geßele
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, 80333, München, Germany
| | - Jacob Halatek
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, 80333, München, Germany
| | - Laeschkir Würthner
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, 80333, München, Germany
| | - Erwin Frey
- Arnold Sommerfeld Center for Theoretical Physics and Center for NanoScience, Department of Physics, Ludwig-Maximilians-Universität München, Theresienstraße 37, 80333, München, Germany.
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11
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New insights into apical-basal polarization in epithelia. Curr Opin Cell Biol 2019; 62:1-8. [PMID: 31505411 DOI: 10.1016/j.ceb.2019.07.017] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2019] [Revised: 07/25/2019] [Accepted: 07/26/2019] [Indexed: 11/21/2022]
Abstract
The establishment of an apical-basal axis of polarity is essential for the organization and functioning of epithelial cells. Polarization of epithelial cells is orchestrated by a network of conserved polarity regulators that establish opposing cortical domains through mutually antagonistic interactions and positive feedback loops. While our understanding is still far from complete, the molecular details behind these interactions continue to be worked out. Here, we highlight recent findings on the mechanisms that control the activity and localization of apical-basal polarity regulators, including oligomerization and higher-order complex formation, auto-inhibitory interactions, and electrostatic interactions with the plasma membrane.
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12
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Nunes de Almeida F, Walther RF, Pressé MT, Vlassaks E, Pichaud F. Cdc42 defines apical identity and regulates epithelial morphogenesis by promoting apical recruitment of Par6-aPKC and Crumbs. Development 2019; 146:dev175497. [PMID: 31405903 PMCID: PMC6703713 DOI: 10.1242/dev.175497] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Accepted: 07/10/2019] [Indexed: 01/20/2023]
Abstract
Cdc42 regulates epithelial morphogenesis together with the Par complex (Baz/Par3-Par6-aPKC), Crumbs (Crb/CRB3) and Stardust (Sdt/PALS1). However, how these proteins work together and interact during epithelial morphogenesis is not well understood. To address this issue, we used the genetically amenable Drosophila pupal photoreceptor and follicular epithelium. We show that during epithelial morphogenesis active Cdc42 accumulates at the developing apical membrane and cell-cell contacts, independently of the Par complex and Crb. However, membrane localization of Baz, Par6-aPKC and Crb all depend on Cdc42. We find that although binding of Cdc42 to Par6 is not essential for the recruitment of Par6 and aPKC to the membrane, it is required for their apical localization and accumulation, which we find also depends on Par6 retention by Crb. In the pupal photoreceptor, membrane recruitment of Par6-aPKC also depends on Baz. Our work shows that Cdc42 is required for this recruitment and suggests that this factor promotes the handover of Par6-aPKC from Baz onto Crb. Altogether, we propose that Cdc42 drives morphogenesis by conferring apical identity, Par-complex assembly and apical accumulation of Crb.
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Affiliation(s)
| | - Rhian F Walther
- MRC - Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Mary T Pressé
- MRC - Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Evi Vlassaks
- MRC - Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
| | - Franck Pichaud
- MRC - Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK
- Institute for the Physics of Living Systems, University College London, London WC1E 6BT, UK
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13
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Renschler FA, Bruekner SR, Salomon PL, Mukherjee A, Kullmann L, Schütz-Stoffregen MC, Henzler C, Pawson T, Krahn MP, Wiesner S. Structural basis for the interaction between the cell polarity proteins Par3 and Par6. Sci Signal 2018; 11:11/517/eaam9899. [PMID: 29440511 DOI: 10.1126/scisignal.aam9899] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Polarity is a fundamental property of most cell types. The Par protein complex is a major driving force in generating asymmetrically localized protein networks and consists of atypical protein kinase C (aPKC), Par3, and Par6. Dysfunction of this complex causes developmental abnormalities and diseases such as cancer. We identified a PDZ domain-binding motif in Par6 that was essential for its interaction with Par3 in vitro and for Par3-mediated membrane localization of Par6 in cultured cells. In fly embryos, we observed that the PDZ domain-binding motif was functionally redundant with the PDZ domain in targeting Par6 to the cortex of epithelial cells. Our structural analyses by x-ray crystallography and NMR spectroscopy showed that both the PDZ1 and PDZ3 domains but not the PDZ2 domain in Par3 engaged in a canonical interaction with the PDZ domain-binding motif in Par6. Par3 thus has the potential to recruit two Par6 proteins simultaneously, which may facilitate the assembly of polarity protein networks through multivalent PDZ domain interactions.
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Affiliation(s)
- Fabian A Renschler
- Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Susanne R Bruekner
- Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Paulin L Salomon
- Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Amrita Mukherjee
- Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Lars Kullmann
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany
| | | | - Christine Henzler
- Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany
| | - Tony Pawson
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, 600 University Avenue, Toronto, Ontario M5G 1X5, Canada
| | - Michael P Krahn
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstrasse 31, 93053 Regensburg, Germany.,Medical Clinic D, University Hospital of Münster, Domagkstraβe 3a, 48149 Münster, Germany
| | - Silke Wiesner
- Max Planck Institute for Developmental Biology, Max-Planck-Ring 5, 72076 Tübingen, Germany.
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14
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Lang CF, Munro E. The PAR proteins: from molecular circuits to dynamic self-stabilizing cell polarity. Development 2017; 144:3405-3416. [PMID: 28974638 DOI: 10.1242/dev.139063] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
PAR proteins constitute a highly conserved network of scaffolding proteins, adaptors and enzymes that form and stabilize cortical asymmetries in response to diverse inputs. They function throughout development and across the metazoa to regulate cell polarity. In recent years, traditional approaches to identifying and characterizing molecular players and interactions in the PAR network have begun to merge with biophysical, theoretical and computational efforts to understand the network as a pattern-forming biochemical circuit. Here, we summarize recent progress in the field, focusing on recent studies that have characterized the core molecular circuitry, circuit design and spatiotemporal dynamics. We also consider some of the ways in which the PAR network has evolved to polarize cells in different contexts and in response to different cues and functional constraints.
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Affiliation(s)
- Charles F Lang
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA.,Committee on Genetics, Genomics and Systems Biology, University of Chicago, Chicago, IL 60637, USA
| | - Edwin Munro
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, USA .,Committee on Genetics, Genomics and Systems Biology, University of Chicago, Chicago, IL 60637, USA
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15
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Wang SC, Low TYF, Nishimura Y, Gole L, Yu W, Motegi F. Cortical forces and CDC-42 control clustering of PAR proteins for Caenorhabditis elegans embryonic polarization. Nat Cell Biol 2017; 19:988-995. [DOI: 10.1038/ncb3577] [Citation(s) in RCA: 89] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Accepted: 06/20/2017] [Indexed: 12/12/2022]
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16
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Pacquelet A. Asymmetric Cell Division in the One-Cell C. elegans Embryo: Multiple Steps to Generate Cell Size Asymmetry. Results Probl Cell Differ 2017; 61:115-140. [PMID: 28409302 DOI: 10.1007/978-3-319-53150-2_5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The first division of the one-cell C. elegans embryo has been a fundamental model in deciphering the mechanisms underlying asymmetric cell division. Polarization of the one-cell zygote is induced by a signal from the sperm centrosome and results in the asymmetric distribution of PAR proteins. Multiple mechanisms then maintain PAR polarity until the end of the first division. Once asymmetrically localized, PAR proteins control several essential aspects of asymmetric division, including the position of the mitotic spindle along the polarity axis. Coordination of the spindle and cytokinetic furrow positions is the next essential step to ensure proper asymmetric division. In this chapter, I review the different mechanisms underlying these successive steps of asymmetric division. Work from the last 30 years has revealed the existence of multiple and redundant regulatory pathways which ensure division robustness. Besides the essential role of PAR proteins, this work also emphasizes the importance of both microtubules and actomyosin throughout the different steps of asymmetric division.
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Affiliation(s)
- Anne Pacquelet
- CNRS, UMR6290, Rennes, France. .,Université de Rennes 1, Institut de Génétique et Développement de Rennes, Rennes, France. .,CNRS UMR6290-IGDR, 2 avenue du Professeur Léon Bernard, 35043, Rennes Cedex, France.
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17
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Dynamic Opposition of Clustered Proteins Stabilizes Cortical Polarity in the C. elegans Zygote. Dev Cell 2016; 35:131-42. [PMID: 26460948 DOI: 10.1016/j.devcel.2015.09.006] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Revised: 08/05/2015] [Accepted: 09/10/2015] [Indexed: 12/13/2022]
Abstract
Dynamic maintenance of cell polarity is essential for development and physiology. Here we combine experiments and modeling to elucidate mechanisms that maintain cortical polarity in the C. elegans zygote. We show that polarity is dynamically stabilized by two coupled cross-inhibitory feedback loops: one involves the oligomeric scaffold PAR-3 and the kinase PAR-1, and the other involves CDC-42 and its putative GAP CHIN-1. PAR-3 and CDC-42 are both required locally to recruit PAR-6/PKC-3, which inhibits PAR-1 (shown previously) and inhibits local growth/accumulation of CHIN-1 clusters. Conversely, PAR-1 inhibits local accumulation of PAR-3 oligomers, while CHIN-1 inhibits CDC-42 (shown previously), such that either PAR-1 or CHIN-1 can prevent recruitment of PAR-6/PKC-3, but loss of both causes complete loss of polarity. Ultrasensitive dependence of CHIN-1 cluster growth on PAR-6/PKC-3 endows this core circuit with bistable dynamics, while transport of CHIN-1 clusters by cortical flow can stabilize the AP boundary against diffusive spread of PAR-6/PKC-3.
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18
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Moorhouse KS, Gudejko HF, McDougall A, Burgess DR. Influence of cell polarity on early development of the sea urchin embryo. Dev Dyn 2015; 244:1469-84. [PMID: 26293695 PMCID: PMC4715636 DOI: 10.1002/dvdy.24337] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2015] [Revised: 08/11/2015] [Accepted: 08/13/2015] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Establishment and maintenance of cell polarity is critical for normal embryonic development. Previously, it was thought that the echinoderm embryo remained relatively unpolarized until the first asymmetric division at the 16-cell stage. Here, we analyzed roles of the cell polarity regulators, the PAR complex proteins, and how their disruption in early development affects later developmental milestones. RESULTS We found that PAR6, aPKC, and CDC42 localize to the apical cortex as early as the 2-cell stage and that this localization is retained through the gastrula stage. Of interest, PAR1 also colocalizes with these apical markers through the gastrula stage. Additionally, PAR1 was found to be in complex with aPKC, but not PAR6. PAR6, aPKC, and CDC42 are anchored in the cortical actin cytoskeleton by assembled myosin. Furthermore, assembled myosin was found to be necessary to maintain proper PAR6 localization through subsequent cleavage divisions. Interference with myosin assembly prevented the embryos from reaching the blastula stage, while transient disruptions of either actin or microtubules did not have this effect. CONCLUSIONS These observations suggest that disruptions of the polarity in the early embryo can have a significant impact on the ability of the embryo to reach later critical stages in development.
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Affiliation(s)
- Kathleen S. Moorhouse
- Department of Biology, Boston College, Chestnut Hill, Massachusetts
- Marine Biological Laboratory, Woods Hole, Massachusetts
| | - Heather F.M. Gudejko
- Department of Biology, Boston College, Chestnut Hill, Massachusetts
- Marine Biological Laboratory, Woods Hole, Massachusetts
| | - Alex McDougall
- UMR 7009, UPMC Sorbonne Universités, Centre National de la Recherche (CNRS), Observatoire Océanologique, 181 Chemin du Lazaret, 06230 Villefranche-sur-Mer, France
| | - David R. Burgess
- Department of Biology, Boston College, Chestnut Hill, Massachusetts
- Marine Biological Laboratory, Woods Hole, Massachusetts
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19
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Zukaite V, Cook RT, Walker AJ. Multiple roles for protein kinase C in gastropod embryogenesis. Cell Tissue Res 2015; 364:117-24. [DOI: 10.1007/s00441-015-2288-3] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Accepted: 08/27/2015] [Indexed: 02/06/2023]
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20
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Whitney DS, Volkman BF. Some (dis)assembly required: partial unfolding in the Par-6 allosteric switch. Biophys Rev 2015; 7:183-190. [PMID: 26236405 DOI: 10.1007/s12551-015-0164-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Allostery is commonly described as a functional connection between two distant sites in a protein, where a binding event at one site alters affinity at the other. Here we review the conformational dynamics that encode an allosteric switch in the PDZ domain of Par-6. Par-6 is a scaffold protein that organizes other proteins into a complex required to initiate and maintain cell polarity. NMR measurements revealed that the PDZ domain samples an evolutionarily conserved unfolding intermediate allowing rearrangement of two adjacent loop residues that control ligand binding affinity. Cdc42 binding to Par-6 creates a novel interface between the PDZ domain and the adjoining CRIB motif that stabilizes the high-affinity PDZ conformation. Thermodynamic and kinetic studies suggest that partial PDZ unfolding is an integral part of the Par-6 switching mechanism. The Par-6 CRIB-PDZ module illustrates two important structural aspects of protein evolution: the interface between adjacent domains in the same protein can give rise to allosteric regulation, and thermodynamic stability may be sacrificed to increase the sampling frequency of an unfolding intermediate required for conformational switching.
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Affiliation(s)
- Dustin S Whitney
- Department of Biochemistry, Medical College of Wiscsonsin, Milwaukee, WI 52336
| | - Brian F Volkman
- Department of Biochemistry, Medical College of Wiscsonsin, Milwaukee, WI 52336
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21
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Yu CG, Tonikian R, Felsensteiner C, Jhingree JR, Desveaux D, Sidhu SS, Harris TJC. Peptide binding properties of the three PDZ domains of Bazooka (Drosophila Par-3). PLoS One 2014; 9:e86412. [PMID: 24466078 PMCID: PMC3899232 DOI: 10.1371/journal.pone.0086412] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Accepted: 12/12/2013] [Indexed: 12/24/2022] Open
Abstract
The Par complex is a conserved cell polarity regulator. Bazooka/Par-3 is scaffold for the complex and contains three PDZ domains in tandem. PDZ domains can act singly or synergistically to bind the C-termini of interacting proteins. Sequence comparisons among Drosophila Baz and its human and C. elegans Par-3 counterparts indicate a divergence of the peptide binding pocket of PDZ1 and greater conservation for the pockets of PDZ2 and PDZ3. However, it is unclear whether the domains from different species share peptide binding preferences, or if their tandem organization affects their peptide binding properties. To investigate these questions, we first used phage display screens to identify unique peptide binding profiles for each single PDZ domain of Baz. Comparisons with published phage display screens indicate that Baz and C. elegans PDZ2 bind to similar peptides, and that the peptide binding preferences of Baz PDZ3 are more similar to C. elegans versus human PDZ3. Next we quantified the peptide binding preferences of each Baz PDZ domain using single identified peptides in surface plasmon resonance assays. In these direct binding studies, each peptide had a binding preference for a single PDZ domain (although the peptide binding of PDZ2 was weakest and the least specific). PDZ1 and PDZ3 bound their peptides with dissociation constants in the nM range, whereas PDZ2-peptide binding was in the µM range. To test whether tandem PDZ domain organization affects peptide binding, we examined a fusion protein containing all three PDZ domains and their normal linker regions. The binding strengths of the PDZ-specific peptides to single PDZ domains and to the PDZ domain tandem were indistinguishable. Thus, the peptide binding pockets of each PDZ domain in Baz are not obviously affected by the presence of neighbouring PDZ domains, but act as isolated modules with specific in vitro peptide binding preferences.
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Affiliation(s)
- Cao Guo Yu
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
| | - Raffi Tonikian
- Terrence Donnelly Centre for Cellular and Biomolecular Research, and Banting and Best Department of Medical Research, and Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Corinna Felsensteiner
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
| | - Jacquelyn R. Jhingree
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
| | - Darrell Desveaux
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
- Centre for the Analysis of Genome Evolution & Function, University of Toronto, Toronto, Ontario, Canada
| | - Sachdev S. Sidhu
- Terrence Donnelly Centre for Cellular and Biomolecular Research, and Banting and Best Department of Medical Research, and Department of Molecular Genetics, University of Toronto, Toronto, Ontario, Canada
| | - Tony J. C. Harris
- Department of Cell & Systems Biology, University of Toronto, Toronto, Ontario, Canada
- * E-mail:
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22
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Motegi F, Seydoux G. The PAR network: redundancy and robustness in a symmetry-breaking system. Philos Trans R Soc Lond B Biol Sci 2013; 368:20130010. [PMID: 24062581 PMCID: PMC3785961 DOI: 10.1098/rstb.2013.0010] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
To become polarized, cells must first 'break symmetry'. Symmetry breaking is the process by which an unpolarized, symmetric cell develops a singularity, often at the cell periphery, that is used to develop a polarity axis. The Caenorhabditis elegans zygote breaks symmetry under the influence of the sperm-donated centrosome, which causes the PAR polarity regulators to sort into distinct anterior and posterior cortical domains. Modelling analyses have shown that cortical flows induced by the centrosome combined with antagonism between anterior and posterior PARs (mutual exclusion) are sufficient, in principle, to break symmetry, provided that anterior and posterior PAR activities are precisely balanced. Experimental evidence indicates, however, that the system is surprisingly robust to changes in cortical flows, mutual exclusion and PAR balance. We suggest that this robustness derives from redundant symmetry-breaking inputs that engage two positive feedback loops mediated by the anterior and posterior PAR proteins. In particular, the PAR-2 feedback loop stabilizes the polarized state by creating a domain where posterior PARs are immune to exclusion by anterior PARs. The two feedback loops in the PAR network share characteristics with the two feedback loops in the Cdc42 polarization network of Saccharomyces cerevisiae.
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Affiliation(s)
- Fumio Motegi
- Temasek Lifesciences Laboratory, National University of Singapore, , 1 Research Link, Singapore 117604, Republic of Singapore
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23
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Beatty A, Morton DG, Kemphues K. PAR-2, LGL-1 and the CDC-42 GAP CHIN-1 act in distinct pathways to maintain polarity in the C. elegans embryo. Development 2013; 140:2005-14. [PMID: 23536568 DOI: 10.1242/dev.088310] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
In the one-cell C. elegans embryo, polarity is maintained by mutual antagonism between the anterior cortical proteins PAR-3, PKC-3, PAR-6 and CDC-42, and the posterior cortical proteins PAR-2 and LGL-1 on the posterior cortex. The mechanisms by which these proteins interact to maintain polarity are incompletely understood. In this study, we investigate the interplay among PAR-2, LGL-1, myosin, the anterior PAR proteins and CDC-42. We find that PAR-2 and LGL-1 affect cortical myosin accumulation by different mechanisms. LGL-1 does not directly antagonize the accumulation of cortical myosin and instead plays a role in regulating PAR-6 levels. By contrast, PAR-2 likely has separate roles in regulating cortical myosin accumulation and preventing the expansion of the anterior cortical domain. We also provide evidence that asymmetry of active CDC-42 can be maintained independently of LGL-1 and PAR-2 by a redundant pathway that includes the CDC-42 GAP CHIN-1. Finally, we show that, in addition to its primary role in regulating the size of the anterior cortical domain via its binding to PAR-6, CDC-42 has a secondary role in regulating cortical myosin that is not dependent on PAR-6.
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Affiliation(s)
- Alexander Beatty
- Department of Molecular Biology and Genetics, Cornell University, 433 Biotechnology Building, Ithaca, NY 14853, USA
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24
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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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25
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Abstract
Cell polarity is crucial for many functions including cell migration, tissue organization and asymmetric cell division. In animal cells, cell polarity is controlled by the highly conserved PAR (PARtitioning defective) proteins. par genes have been identified in Caenorhabditis elegans in screens for maternal lethal mutations that disrupt cytoplasmic partitioning and asymmetric division. Although PAR proteins were identified more than 20 years ago, our understanding on how they regulate polarity and how they are regulated is still incomplete. In this chapter we review our knowledge of the processes of cell polarity establishment and maintenance, and asymmetric cell division in the early C. elegans embryo. We discuss recent findings that highlight new players in cell polarity and/or reveal the molecular details on how PAR proteins regulate polarity processes.
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26
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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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27
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Dawes AT, Munro EM. PAR-3 oligomerization may provide an actin-independent mechanism to maintain distinct par protein domains in the early Caenorhabditis elegans embryo. Biophys J 2011; 101:1412-22. [PMID: 21943422 DOI: 10.1016/j.bpj.2011.07.030] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2011] [Revised: 06/11/2011] [Accepted: 07/06/2011] [Indexed: 02/06/2023] Open
Abstract
Par proteins establish discrete intracellular spatial domains to polarize many different cell types. In the single-cell embryo of the nematode worm Caenorhabditis elegans, the segregation of Par proteins is crucial for proper division and cell fate specification. Actomyosin-based cortical flows drive the initial formation of anterior and posterior Par domains, but cortical actin is not required for the maintenance of these domains. Here we develop a model of interactions between the Par proteins that includes both mutual inhibition and PAR-3 oligomerization. We show that this model gives rise to a bistable switch mechanism, allowing the Par proteins to occupy distinct anterior and posterior domains seen in the early C. elegans embryo, independent of dynamics or asymmetries in the actin cortex. The model predicts a sharp loss of cortical Par protein asymmetries during gradual depletion of the Par protein PAR-6, and we confirm this prediction experimentally. Together, these results suggest both mutual inhibition and PAR-3 oligomerization are sufficient to maintain distinct Par protein domains in the early C. elegans embryo.
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Affiliation(s)
- Adriana T Dawes
- Department of Mathematical and Statistical Statistical Sciences, University of Alberta, Edmonton, Alberta, Canada.
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28
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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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29
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Abstract
Cell polarity is essential for cells to divide asymmetrically, form spatially restricted subcellular structures and participate in three-dimensional multicellular organization. PAR proteins are conserved polarity regulators that function by generating cortical landmarks that establish dynamic asymmetries in the distribution of effector proteins. Here, we review recent findings on the role of PAR proteins in cell polarity in C. elegans and Drosophila, and emphasize the links that exist between PAR networks and cytoskeletal proteins that both regulate PAR protein localization and act as downstream effectors to elaborate polarity within the cell.
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Affiliation(s)
- Jeremy Nance
- Helen L. and Martin S. Kimmel Center for Biology and Medicine at the Skirball Institute for Biomolecular Medicine, NYU School of Medicine, 540 First Avenue, New York, NY 10016, USA.
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30
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Noatynska A, Panbianco C, Gotta M. SPAT-1/Bora acts with Polo-like kinase 1 to regulate PAR polarity and cell cycle progression. Development 2010; 137:3315-25. [PMID: 20823068 DOI: 10.1242/dev.055293] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
During asymmetric cell division, cell polarity and cell cycle progression are tightly coordinated, yet mechanisms controlling both these events are poorly understood. Here we show that the Bora homologue SPAT-1 regulates both PAR polarity and cell cycle progression in C. elegans embryos. We find that, similarly to mammalian cells, SPAT-1 acts with PLK-1 and not with the mitotic kinase Aurora A (AIR-1), as shown in Drosophila. SPAT-1 binds to PLK-1, and depletion of SPAT-1 or PLK-1 leads to similar cell division defects in early embryos, which differ from the defects caused by depletion of AIR-1. Additionally, SPAT-1 and PLK-1 depletion causes impaired polarity with abnormal length of the anterior and posterior PAR domains, and partial plk-1(RNAi) or spat-1(RNAi), but not air-1(RNAi), can rescue the lethality of a par-2 mutant. SPAT-1 is enriched in posterior cells, and this enrichment depends on PAR polarity and PLK-1. Taken together, our data suggest a model in which SPAT-1 promotes the activity of PLK-1 to regulate both cell polarity and cell cycle timing during asymmetric cell division, providing a link between these two processes.
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Affiliation(s)
- Anna Noatynska
- Department of Genetic Medicine and Development, Faculty of Medicine, University of Geneva, 1 rue Michel Servet, Geneva 4, Switzerland
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31
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Li B, Kim H, Beers M, Kemphues K. Different domains of C. elegans PAR-3 are required at different times in development. Dev Biol 2010; 344:745-57. [PMID: 20678977 DOI: 10.1016/j.ydbio.2010.05.506] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2009] [Revised: 05/17/2010] [Accepted: 05/24/2010] [Indexed: 01/26/2023]
Abstract
Polarity is a fundamental cellular feature that is critical for generating cell diversity and maintaining organ functions during development. In C. elegans, the one-cell embryo is polarized via asymmetric localization of the PAR proteins, which in turn are required to establish the future anterior-posterior axis of the embryo. PAR-3, a conserved PDZ domain-containing protein, acts with PAR-6 and PKC-3 (atypical protein kinase; aPKC) to regulate cell polarity and junction formation in a variety of cell types. To understand how PAR-3 localizes and functions during C. elegans development, we produced targeted mutations and deletions of conserved domains of PAR-3 and examined the localization and function of the GFP-tagged proteins in C. elegans embryos and larvae. We find that CR1, the PAR-3 self-oligomerization domain, is required for PAR-3 cortical distribution and function only during early embryogenesis and that PDZ2 is required for PAR-3 to accumulate stably at the cell periphery in early embryos and at the apical surface in pharyngeal and intestinal epithelial cells. We also show that phosphorylation at S863 by PKC-3 is not essential in early embryogenesis, but is important in later development. Surprisingly neither PDZ1 nor PDZ3 are essential for localization or function. Our results indicate that the different domains and phosphorylated forms of PAR-3 can have different roles during C. elegans development.
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Affiliation(s)
- Bingsi Li
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA
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