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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Valdivia A, Duran C, Lee M, Williams HC, Lee MY, San Martin A. Nox1-based NADPH oxidase regulates the Par protein complex activity to control cell polarization. Front Cell Dev Biol 2023; 11:1231489. [PMID: 37635877 PMCID: PMC10457011 DOI: 10.3389/fcell.2023.1231489] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2023] [Accepted: 07/25/2023] [Indexed: 08/29/2023] Open
Abstract
Cell migration is essential for many biological and pathological processes. Establishing cell polarity with a trailing edge and forming a single lamellipodium at the leading edge of the cell is crucial for efficient directional cell migration and is a hallmark of mesenchymal cell motility. Lamellipodia formation is regulated by spatial-temporal activation of the small GTPases Rac and Cdc42 at the front edge, and RhoA at the rear end. At a molecular level, partitioning-defective (Par) protein complex comprising Par3, Par6, and atypical Protein Kinase (aPKC isoforms ζ and λ/ι) regulates front-rear axis polarization. At the front edge, integrin clustering activates Cdc42, prompting the formation of Par3/Par6/aPKC complexes to modulate MTOC positioning and microtubule stabilization. Consequently, the Par3/Par6/aPKC complex recruits Rac1-GEF Tiam to activate Rac1, leading to lamellipodium formation. At the rear end, RhoA-ROCK phosphorylates Par3 disrupting its interaction with Tiam and inactivating Rac1. RhoA activity at the rear end allows the formation of focal adhesions and stress fibers necessary to generate the traction forces that allow cell movement. Nox1-based NADPH oxidase is necessary for PDGF-induced migration in vitro and in vivo for many cell types, including fibroblasts and smooth muscle cells. Here, we report that Nox1-deficient cells failed to acquire a normal front-to-rear polarity, polarize MTOC, and form a single lamellipodium. Instead, these cells form multiple protrusions that accumulate Par3 and active Tiam. The exogenous addition of H2O2 rescues this phenotype and is associated with the hyperactivation of Par3, Tiam, and Rac1. Mechanistically, Nox1 deficiency induces the inactivation of PP2A phosphatase, leading to increased activation of aPKC. These results were validated in Nox1y/- primary mouse aortic smooth muscle cells (MASMCs), which also showed PP2A inactivation after PDGF-BB stimulation consistent with exacerbated activation of aPKC. Moreover, we evaluated the physiological relevance of this signaling pathway using a femoral artery wire injury model to generate neointimal hyperplasia. Nox1y/- mice showed increased staining for the inactive form of PP2A and increased signal for active aPKC, suggesting that PP2A and aPKC activities might contribute to reducing neointima formation observed in the arteries of Nox1y/- mice.
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Affiliation(s)
- Alejandra Valdivia
- Division of Cardiology, Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Charity Duran
- Division of Cardiology, Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Mingyoung Lee
- Division of Cardiology, Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Holly C. Williams
- Division of Cardiology, Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
| | - Moo-Yeol Lee
- Division of Cardiology, Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
- BK21 FOUR Team and Integrated Research Institute for Drug Development, College of Pharmacy, Dongguk University, Goyang, Republic of Korea
| | - Alejandra San Martin
- Division of Cardiology, Department of Medicine, School of Medicine, Emory University, Atlanta, GA, United States
- Institute of Biomedical Sciences, Faculty of Medicine and Faculty of Life Science, Universidad Andres Bello, Santiago, Chile
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3
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Naturale VF, Pickett MA, Feldman JL. Context matters: Lessons in epithelial polarity from the Caenorhabditis elegans intestine and other tissues. Curr Top Dev Biol 2023; 154:37-71. [PMID: 37100523 DOI: 10.1016/bs.ctdb.2023.02.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/28/2023]
Abstract
Epithelia are tissues with diverse morphologies and functions across metazoans, ranging from vast cell sheets encasing internal organs to internal tubes facilitating nutrient uptake, all of which require establishment of apical-basolateral polarity axes. While all epithelia tend to polarize the same components, how these components are deployed to drive polarization is largely context-dependent and likely shaped by tissue-specific differences in development and ultimate functions of polarizing primordia. The nematode Caenorhabditis elegans (C. elegans) offers exceptional imaging and genetic tools and possesses unique epithelia with well-described origins and roles, making it an excellent model to investigate polarity mechanisms. In this review, we highlight the interplay between epithelial polarization, development, and function by describing symmetry breaking and polarity establishment in a particularly well-characterized epithelium, the C. elegans intestine. We compare intestinal polarization to polarity programs in two other C. elegans epithelia, the pharynx and epidermis, correlating divergent mechanisms with tissue-specific differences in geometry, embryonic environment, and function. Together, we emphasize the importance of investigating polarization mechanisms against the backdrop of tissue-specific contexts, while also underscoring the benefits of cross-tissue comparisons of polarity.
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Affiliation(s)
- Victor F Naturale
- Department of Biology, Stanford University, Stanford, CA, United States
| | - Melissa A Pickett
- Department of Biology, Stanford University, Stanford, CA, United States; Department of Biological Sciences, San José State University, San José, CA, United States
| | - Jessica L Feldman
- Department of Biology, Stanford University, Stanford, CA, United States.
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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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A particle size threshold governs diffusion and segregation of PAR-3 during cell polarization. Cell Rep 2022; 39:110652. [PMID: 35417695 PMCID: PMC9093022 DOI: 10.1016/j.celrep.2022.110652] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 12/14/2021] [Accepted: 03/17/2022] [Indexed: 11/23/2022] Open
Abstract
The actomyosin cortex regulates the localization and function of proteins at the plasma membrane. Here, we study how membrane binding, cortical movements, and diffusion determine membrane protein distribution. In Caenorhabditis elegans zygotes, actomyosin flows transport PAR polarity proteins to establish the anterior-posterior axis. Oligomerization of a key scaffold protein, PAR-3, is required for polarization. PAR-3 oligomers are a heterogeneous population of many different sizes, and it remains unclear how oligomer size affects PAR-3 segregation. To address this question, we engineered PAR-3 to defined sizes. We report that PAR-3 trimers are necessary and sufficient for PAR-3 function during polarization and later embryo development. Quantitative analysis of PAR-3 diffusion shows that a threshold size of three subunits allows PAR-3 clusters to stably bind the membrane, where they are corralled and transported by the actomyosin cortex. Our study provides a quantitative model for size-dependent protein transportation of peripheral membrane proteins by cortical flow. The actomyosin cytoskeleton is a major regulator of cellular organization. Chang and Dickinson develop protein-engineering and particle-tracking tools to study how clustered membrane-bound proteins are transported by actomyosin contractions in vivo. Data-driven modeling reveals how membrane binding, diffusion, and collisions with F-actin contribute to protein movement.
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6
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Ramalho JJ, Jones VAS, Mutte S, Weijers D. Pole position: How plant cells polarize along the axes. THE PLANT CELL 2022; 34:174-192. [PMID: 34338785 PMCID: PMC8774072 DOI: 10.1093/plcell/koab203] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 07/30/2021] [Indexed: 05/10/2023]
Abstract
Having a sense of direction is a fundamental cellular trait that can determine cell shape, division orientation, or function, and ultimately the formation of a functional, multicellular body. Cells acquire and integrate directional information by establishing discrete subcellular domains along an axis with distinct molecular profiles, a process known as cell polarization. Insight into the principles and mechanisms underlying cell polarity has been propelled by decades of extensive research mostly in yeast and animal models. Our understanding of cell polarity establishment in plants, which lack most of the regulatory molecules identified in other eukaryotes, is more limited, but significant progress has been made in recent years. In this review, we explore how plant cells coordinately establish stable polarity axes aligned with the organ axes, highlighting similarities in the molecular logic used to polarize both plant and animal cells. We propose a classification system for plant cell polarity events and nomenclature guidelines. Finally, we provide a deep phylogenetic analysis of polar proteins and discuss the evolution of polarity machineries in plants.
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Affiliation(s)
| | | | - Sumanth Mutte
- Laboratory of Biochemistry, Wageningen University, Stippeneng 4, 6703WE Wageningen, The Netherlands
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7
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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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8
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Lin DW, Liu Y, Lee YQ, Yang PJ, Ho CT, Hong JC, Hsiao JC, Liao DC, Liang AJ, Hung TC, Chen YC, Tu HL, Hsu CP, Huang HC. Construction of intracellular asymmetry and asymmetric division in Escherichia coli. Nat Commun 2021; 12:888. [PMID: 33563962 PMCID: PMC7873278 DOI: 10.1038/s41467-021-21135-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2019] [Accepted: 01/09/2021] [Indexed: 01/23/2023] Open
Abstract
The design principle of establishing an intracellular protein gradient for asymmetric cell division is a long-standing fundamental question. While the major molecular players and their interactions have been elucidated via genetic approaches, the diversity and redundancy of natural systems complicate the extraction of critical underlying features. Here, we take a synthetic cell biology approach to construct intracellular asymmetry and asymmetric division in Escherichia coli, in which division is normally symmetric. We demonstrate that the oligomeric PopZ from Caulobacter crescentus can serve as a robust polarized scaffold to functionalize RNA polymerase. Furthermore, by using another oligomeric pole-targeting DivIVA from Bacillus subtilis, the newly synthesized protein can be constrained to further establish intracellular asymmetry, leading to asymmetric division and differentiation. Our findings suggest that the coupled oligomerization and restriction in diffusion may be a strategy for generating a spatial gradient for asymmetric cell division.
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Affiliation(s)
- Da-Wei Lin
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Yang Liu
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Yue-Qi Lee
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Po-Jiun Yang
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Chia-Tse Ho
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Jui-Chung Hong
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | | | - Der-Chien Liao
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - An-Jou Liang
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Tzu-Chiao Hung
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Yu-Chuan Chen
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan
| | - Hsiung-Lin Tu
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan
- Genome and Systems Biology Degree Program, National Taiwan University, Taipei, Taiwan
| | - Chao-Ping Hsu
- Institute of Chemistry, Academia Sinica, Taipei, Taiwan
- Genome and Systems Biology Degree Program, National Taiwan University, Taipei, Taiwan
| | - Hsiao-Chun Huang
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan.
- Genome and Systems Biology Degree Program, National Taiwan University, Taipei, Taiwan.
- Department of Life Science, National Taiwan University, Taipei, Taiwan.
- Graduate Institute of Electronics Engineering, National Taiwan University, Taipei, Taiwan.
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9
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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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10
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Gubieda AG, Packer JR, Squires I, Martin J, Rodriguez J. Going with the flow: insights from Caenorhabditis elegans zygote polarization. Philos Trans R Soc Lond B Biol Sci 2020; 375:20190555. [PMID: 32829680 PMCID: PMC7482210 DOI: 10.1098/rstb.2019.0555] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/09/2020] [Indexed: 12/12/2022] Open
Abstract
Cell polarity is the asymmetric distribution of cellular components along a defined axis. Polarity relies on complex signalling networks between conserved patterning proteins, including the PAR (partitioning defective) proteins, which become segregated in response to upstream symmetry breaking cues. Although the mechanisms that drive the asymmetric localization of these proteins are dependent upon cell type and context, in many cases the regulation of actomyosin cytoskeleton dynamics is central to the transport, recruitment and/or stabilization of these polarity effectors into defined subcellular domains. The transport or advection of PAR proteins by an actomyosin flow was first observed in the Caenorhabditis elegans zygote more than a decade ago. Since then a multifaceted approach, using molecular methods, high-throughput screens, and biophysical and computational models, has revealed further aspects of this flow and how polarity regulators respond to and modulate it. Here, we review recent findings on the interplay between actomyosin flow and the PAR patterning networks in the polarization of the C. elegans zygote. We also discuss how these discoveries and developed methods are shaping our understanding of other flow-dependent polarizing systems. This article is part of a discussion meeting issue 'Contemporary morphogenesis'.
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Affiliation(s)
| | | | | | | | - Josana Rodriguez
- Biosciences Institute, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
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11
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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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12
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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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13
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Holly RW, Prehoda KE. Phosphorylation of Par-3 by Atypical Protein Kinase C and Competition between Its Substrates. Dev Cell 2020; 49:678-679. [PMID: 31163172 DOI: 10.1016/j.devcel.2019.05.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Ryan W Holly
- Institute of Molecular Biology, Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA
| | - Kenneth E Prehoda
- Institute of Molecular Biology, Department of Chemistry and Biochemistry, University of Oregon, Eugene, OR 97403, USA.
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14
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Kullmann L, Krahn MP. Redundant regulation of localization and protein stability of DmPar3. Cell Mol Life Sci 2018; 75:3269-3282. [PMID: 29523893 PMCID: PMC11105499 DOI: 10.1007/s00018-018-2792-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2017] [Revised: 03/03/2018] [Accepted: 03/07/2018] [Indexed: 11/25/2022]
Abstract
Apical-basal polarity is an important characteristic of epithelia and Drosophila neural stem cells. The conserved Par complex, which consists of the atypical protein kinase C and the scaffold proteins Baz and Par6, is a key player in the establishment of apical-basal cell polarity. Membrane recruitment of Baz has been reported to be accomplished by several mechanisms, which might function in redundancy, to ensure the correct localization of the complex. However, none of the described interactions was sufficient to displace the protein from the apical junctions. Here, we dissected the role of the oligomerization domain and the lipid-binding motif of Baz in vivo in the Drosophila embryo. We found that these domains function in redundancy to ensure the apical junctional localization of Baz: inactivation of only one domain is not sufficient to disrupt the function of Baz during apical-basal polarization of epithelial cells and neural stem cells. In contrast, mutation of both domains results in a strongly impaired protein stability and a phenotype characterized by embryonic lethality and an impaired apical-basal polarity in the embryonic epithelium and neural stem cells, resembling a baz-loss of function allele. Strikingly, the binding of Baz to the transmembrane proteins E-Cadherin, Echinoid, and Starry Night was not affected in this mutant protein. Our findings reveal a redundant function of the oligomerization and the lipid-binding domain, which is required for protein stability, correct subcellular localization, and apical-basal cell polarization.
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Affiliation(s)
- Lars Kullmann
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany
- Internal Medicine D, University Hospital of Münster, Domagkstr. 3a, 48149, Münster, Germany
| | - Michael P Krahn
- Molecular and Cellular Anatomy, University of Regensburg, Universitätsstr. 31, 93053, Regensburg, Germany.
- Internal Medicine D, University Hospital of Münster, Domagkstr. 3a, 48149, Münster, Germany.
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15
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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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16
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Dickinson DJ, Schwager F, Pintard L, Gotta M, Goldstein B. A Single-Cell Biochemistry Approach Reveals PAR Complex Dynamics during Cell Polarization. Dev Cell 2017; 42:416-434.e11. [PMID: 28829947 DOI: 10.1016/j.devcel.2017.07.024] [Citation(s) in RCA: 90] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Revised: 07/14/2017] [Accepted: 07/25/2017] [Indexed: 11/30/2022]
Abstract
Regulated protein-protein interactions are critical for cell signaling, differentiation, and development. For the study of dynamic regulation of protein interactions in vivo, there is a need for techniques that can yield time-resolved information and probe multiple protein binding partners simultaneously, using small amounts of starting material. Here we describe a single-cell protein interaction assay. Single-cell lysates are generated at defined time points and analyzed using single-molecule pull-down, yielding information about dynamic protein complex regulation in vivo. We established the utility of this approach by studying PAR polarity proteins, which mediate polarization of many animal cell types. We uncovered striking regulation of PAR complex composition and stoichiometry during Caenorhabditis elegans zygote polarization, which takes place in less than 20 min. PAR complex dynamics are linked to the cell cycle by Polo-like kinase 1 and govern the movement of PAR proteins to establish polarity. Our results demonstrate an approach to study dynamic biochemical events in vivo.
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Affiliation(s)
- Daniel J Dickinson
- Department of Biology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
| | - Francoise Schwager
- Department of Cell Physiology and Metabolism, University of Geneva Medical Faculty, 1, rue Michel Servet, 1211 Geneva, Switzerland
| | - Lionel Pintard
- Institut Jacques Monod, Cell Cycle and Development Team, Centre National de la Recherche Scientifique and University of Paris Diderot and Sorbonne Paris Cité UMR7592, Paris 75013, France
| | - Monica Gotta
- Department of Cell Physiology and Metabolism, University of Geneva Medical Faculty, 1, rue Michel Servet, 1211 Geneva, Switzerland
| | - Bob Goldstein
- Department of Biology and Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
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17
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Abstract
The scaffold protein Par-3 (
Drosophila Bazooka) is a central organizer of cell polarity across animals. This review focuses on how the clustering of Par-3 contributes to cell polarity. It begins with the Par-3 homo-oligomerization mechanism and its regulation by Par-1 phosphorylation. The role of polarized cytoskeletal networks in distributing Par-3 clusters to one end of the cell is then discussed, as is the subsequent maintenance of polarized Par-3 clusters through hindered mobility and inhibition from the opposite pole. Finally, specific roles of Par-3 clusters are reviewed, including the bundling of microtubules, the cortical docking of centrosomes, the growth and positioning of cadherin–catenin clusters, and the inhibition of the Par-6–aPKC kinase cassette. Examples are drawn from
Drosophila, Caenorhabditis elegans, mammalian cell culture, and biochemical studies.
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Affiliation(s)
- Tony J C Harris
- Department of Cell & Systems Biology, University of Toronto, Toronto, Canada
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18
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Rodriguez J, Peglion F, Martin J, Hubatsch L, Reich J, Hirani N, Gubieda AG, Roffey J, Fernandes AR, St Johnston D, Ahringer J, Goehring NW. aPKC Cycles between Functionally Distinct PAR Protein Assemblies to Drive Cell Polarity. Dev Cell 2017; 42:400-415.e9. [PMID: 28781174 PMCID: PMC5563072 DOI: 10.1016/j.devcel.2017.07.007] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 06/19/2017] [Accepted: 07/10/2017] [Indexed: 01/09/2023]
Abstract
The conserved polarity effector proteins PAR-3, PAR-6, CDC-42, and atypical protein kinase C (aPKC) form a core unit of the PAR protein network, which plays a central role in polarizing a broad range of animal cell types. To functionally polarize cells, these proteins must activate aPKC within a spatially defined membrane domain on one side of the cell in response to symmetry-breaking cues. Using the Caenorhabditis elegans zygote as a model, we find that the localization and activation of aPKC involve distinct, specialized aPKC-containing assemblies: a PAR-3-dependent assembly that responds to polarity cues and promotes efficient segregation of aPKC toward the anterior but holds aPKC in an inactive state, and a CDC-42-dependent assembly in which aPKC is active but poorly segregated. Cycling of aPKC between these distinct functional assemblies, which appears to depend on aPKC activity, effectively links cue-sensing and effector roles within the PAR network to ensure robust establishment of polarity.
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Affiliation(s)
- Josana Rodriguez
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK; Wellcome Trust/Cancer Research UK Gurdon Institute, Cambridge CB2 1QN, UK.
| | | | - Jack Martin
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | | | - Jacob Reich
- The Francis Crick Institute, London NW1 1AT, UK
| | | | - Alicia G Gubieda
- Institute for Cell and Molecular Biosciences, Newcastle University, Newcastle upon Tyne NE2 4HH, UK
| | - Jon Roffey
- Cancer Research Technology, Wolfson Institute for Biomedical Research, London WC1E 6BT, UK
| | | | - Daniel St Johnston
- Wellcome Trust/Cancer Research UK Gurdon Institute, Cambridge CB2 1QN, UK
| | - Julie Ahringer
- Wellcome Trust/Cancer Research UK Gurdon Institute, Cambridge CB2 1QN, UK
| | - Nathan W Goehring
- The Francis Crick Institute, London NW1 1AT, UK; Medical Research Council Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, UK.
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19
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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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20
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Visco I, Hoege C, Hyman AA, Schwille P. In vitro Reconstitution of a Membrane Switch Mechanism for the Polarity Protein LGL. J Mol Biol 2016; 428:4828-4842. [PMID: 27720986 DOI: 10.1016/j.jmb.2016.10.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/28/2016] [Accepted: 10/01/2016] [Indexed: 12/24/2022]
Abstract
Cell polarity arises from a combination of interactions between biological molecules, such as activation, inhibition, and positive or negative feedback between specific polarity units. Activation and inhibition often take place in the form of a membrane binding switch. Lethal giant larvae (LGL), a conserved regulator of cell polarity in animals, was suggested to function as such a switch. LGL localizes to both the cytoplasm and, asymmetrically, the membrane. However, the spatial regulation mechanism of LGL membrane localization has remained unclear. For systematic elucidation, we set out to reconstitute a minimal polarity unit using a model membrane, Caenorhabditis elegans LGL (LGL-1), and atypical protein kinase C (aPKC) supposed to activate the membrane switch. We identified a membrane binding sequence (MBS) in LGL-1 by a screen in vivo, reconstituted LGL-1 membrane binding in vitro, and successfully implemented the membrane switch by aPKC phosphorylation activity, detaching LGL from membranes. Upon membrane binding, LGL-1 MBS folds into an alpha-helix in which three regions can be identified: a positively charged patch, a switch area containing the three aPKC phosphorylation sites, and a hydrophobic area probably buried in the membrane. Phosphorylation by aPKC dramatically reduces the binding affinity of the LGL-1 MBS to negatively charged model membranes, inducing its detachment. Specific residues in the MBS are critical for LGL-1 function in C. elegans.
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Affiliation(s)
- Ilaria Visco
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
| | - Carsten Hoege
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Anthony A Hyman
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Petra Schwille
- Max Planck Institute of Biochemistry, Am Klopferspitz 18, 82152 Martinsried, Germany.
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21
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Waaijers S, Muñoz J, Berends C, Ramalho JJ, Goerdayal SS, Low TY, Zoumaro-Djayoon AD, Hoffmann M, Koorman T, Tas RP, Harterink M, Seelk S, Kerver J, Hoogenraad CC, Bossinger O, Tursun B, van den Heuvel S, Heck AJR, Boxem M. A tissue-specific protein purification approach in Caenorhabditis elegans identifies novel interaction partners of DLG-1/Discs large. BMC Biol 2016; 14:66. [PMID: 27506200 PMCID: PMC4977824 DOI: 10.1186/s12915-016-0286-x] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 07/19/2016] [Indexed: 01/06/2023] Open
Abstract
Background Affinity purification followed by mass spectrometry (AP/MS) is a widely used approach to identify protein interactions and complexes. In multicellular organisms, the accurate identification of protein complexes by AP/MS is complicated by the potential heterogeneity of complexes in different tissues. Here, we present an in vivo biotinylation-based approach for the tissue-specific purification of protein complexes from Caenorhabditis elegans. Tissue-specific biotinylation is achieved by the expression in select tissues of the bacterial biotin ligase BirA, which biotinylates proteins tagged with the Avi peptide. Results We generated N- and C-terminal tags combining GFP with the Avi peptide sequence, as well as four BirA driver lines expressing BirA ubiquitously and specifically in the seam and hyp7 epidermal cells, intestine, or neurons. We validated the ability of our approach to identify bona fide protein interactions by identifying the known LGL-1 interaction partners PAR-6 and PKC-3. Purification of the Discs large protein DLG-1 identified several candidate interaction partners, including the AAA-type ATPase ATAD-3 and the uncharacterized protein MAPH-1.1. We have identified the domains that mediate the DLG-1/ATAD-3 interaction, and show that this interaction contributes to C. elegans development. MAPH-1.1 co-purified specifically with DLG-1 purified from neurons, and shared limited homology with the microtubule-associated protein MAP1A, a known neuronal interaction partner of mammalian DLG4/PSD95. A CRISPR/Cas9-engineered GFP::MAPH-1.1 fusion was broadly expressed and co-localized with microtubules. Conclusions The method we present here is able to purify protein complexes from specific tissues. We uncovered a series of DLG-1 interactors, and conclude that ATAD-3 is a biologically relevant interaction partner of DLG-1. Finally, we conclude that MAPH-1.1 is a microtubule-associated protein of the MAP1 family and a candidate neuron-specific interaction partner of DLG-1. Electronic supplementary material The online version of this article (doi:10.1186/s12915-016-0286-x) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Selma Waaijers
- Developmental Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.,Present address: Department of Physiology, Radboud University Medical Center, Geert Grooteplein 26, 6525 GA, Nijmegen, The Netherlands
| | - Javier Muñoz
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.,Netherlands Proteomics Centre, Padualaan 8, 3584 CH, Utrecht, The Netherlands.,Present address: Proteomics Unit, Spanish National Cancer Research Centre (CNIO), ProteoRed-ISCIII, 28029, Madrid, Spain
| | - Christian Berends
- Developmental Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - João J Ramalho
- Developmental Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Soenita S Goerdayal
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.,Netherlands Proteomics Centre, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Teck Y Low
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.,Netherlands Proteomics Centre, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Adja D Zoumaro-Djayoon
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.,Netherlands Proteomics Centre, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Michael Hoffmann
- Institut für Wissenschaftliche Medizin, D-40591, Düsseldorf, Germany
| | - Thijs Koorman
- Developmental Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.,Present address: Center for Cancer Research and Department of Pathology, Massachusetts General Hospital and Harvard Medical School Department of Pathology, 149 13th Street, 02129, Charlestown, MA, USA
| | - Roderick P Tas
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Martin Harterink
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Stefanie Seelk
- Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Center for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 10, Berlin, 13125, Germany
| | - Jana Kerver
- Developmental Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Casper C Hoogenraad
- Cell Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Olaf Bossinger
- Molecular Cell Biology, Anatomy I, University of Cologne, D-50937, Cologne, Germany
| | - Baris Tursun
- Berlin Institute for Medical Systems Biology (BIMSB), Max Delbrueck Center for Molecular Medicine (MDC) in the Helmholtz Association, Robert-Roessle-Strasse 10, Berlin, 13125, Germany.
| | - Sander van den Heuvel
- Developmental Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute for Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.,Netherlands Proteomics Centre, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Mike Boxem
- Developmental Biology, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands.
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22
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Cortical Polarity of the RING Protein PAR-2 Is Maintained by Exchange Rate Kinetics at the Cortical-Cytoplasmic Boundary. Cell Rep 2016; 16:2156-2168. [DOI: 10.1016/j.celrep.2016.07.047] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2015] [Revised: 01/10/2016] [Accepted: 07/20/2016] [Indexed: 11/20/2022] Open
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23
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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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24
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Blanchoud S, Busso C, Naef F, Gönczy P. Quantitative analysis and modeling probe polarity establishment in C. elegans embryos. Biophys J 2015; 108:799-809. [PMID: 25692585 DOI: 10.1016/j.bpj.2014.12.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2014] [Revised: 11/17/2014] [Accepted: 12/11/2014] [Indexed: 10/24/2022] Open
Abstract
Cell polarity underlies many aspects of metazoan development and homeostasis, and relies notably on a set of PAR proteins located at the cell cortex. How these proteins interact in space and time remains incompletely understood. We performed a quantitative assessment of polarity establishment in one-cell stage Caenorhabditis elegans embryos by combining time-lapse microscopy and image analysis. We used our extensive data set to challenge and further specify an extant mathematical model. Using likelihood-based calibration, we uncovered that cooperativity is required for both anterior and posterior PAR complexes. Moreover, we analyzed the dependence of polarity establishment on changes in size or temperature. The observed robustness of PAR domain dimensions in embryos of different sizes is in agreement with a model incorporating fixed protein concentrations and variations in embryo surface/volume ratio. In addition, we quantified the dynamics of polarity establishment over most of the viable temperatures range of C. elegans. Modeling of these data suggests that diffusion of PAR proteins is the process most affected by temperature changes, although cortical flows appear unaffected. Overall, our quantitative analytical framework provides insights into the dynamics of polarity establishment in a developing system.
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Affiliation(s)
- Simon Blanchoud
- Swiss Institute for Experimental Cancer Research (ISREC), Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland; The Institute of Bioengineering (IBI), School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
| | - Coralie Busso
- Swiss Institute for Experimental Cancer Research (ISREC), Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
| | - Félix Naef
- The Institute of Bioengineering (IBI), School of Life Sciences, Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland
| | - Pierre Gönczy
- Swiss Institute for Experimental Cancer Research (ISREC), Swiss Federal Institute of Technology (EPFL), Lausanne, Switzerland.
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25
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Sturrock M, Dawes AT. Protein abundance may regulate sensitivity to external cues in polarized cells. J R Soc Interface 2015; 12:rsif.2015.0150. [PMID: 25878132 DOI: 10.1098/rsif.2015.0150] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Cell polarization is a ubiquitous process which results in cellular constituents being organized into discrete intracellular spatial domains. It occurs in a variety of cell types, including epithelial cells, immune system cells and neurons. A key player in this process is the Par protein family whose asymmetric localization to anterior and posterior parts of the cell is crucial for proper division and cell fate specification. In this paper, we explore a stochastic analogue of the temporal model of Par protein interactions first developed in Dawes & Munro (Dawes and Munro 2011 Biophys. J. 101, 1412-1422. (doi:10.1016/j.bpj.2011.07.030)). We focus on how protein abundance influences the behaviour of both the deterministic and stochastic versions of the model. In Dawes & Munro (2011), it was found that bistable behaviour in the temporal model of Par protein led to the existence of complementary domains in the corresponding spatio-temporal model. Here, we find that the corresponding temporal stochastic model permits switching behaviour (the model solution 'jumps' between steady states) for lower protein abundances, whereas for higher protein abundances the stochastic and deterministic models are in good agreement (the model solution evolves to one of two steady states). This led us to the testable hypothesis that cells with lower abundances of Par protein may be more sensitive to external cues, whereas cells with higher abundances of Par protein may be less sensitive to external cues. In order to gain more control over the precise abundance of Par protein, we proposed and explored a second model (again, examining both deterministic and stochastic versions) in which the total number of Par molecules is conserved. We found that this model required an additional dimerization reaction in the cytoplasm in order for bistable and switching behaviour to be found. Once this additional reaction was included, we found that both the first and second models gave qualitatively similar results but in different regions of the parameter space, suggesting a further regulatory mechanism that cells could potentially use to modulate their response to external signals.
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Affiliation(s)
- Marc Sturrock
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
| | - Adriana T Dawes
- Department of Mathematics, The Ohio State University, 231 West 18th Avenue, Columbus, OH 43210, USA Department of Molecular Genetics, The Ohio State University, 231 West 18th Avenue, Columbus, OH 43210, USA
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26
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Goehring NW. PAR polarity: from complexity to design principles. Exp Cell Res 2014; 328:258-66. [PMID: 25128809 DOI: 10.1016/j.yexcr.2014.08.009] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2014] [Accepted: 08/04/2014] [Indexed: 12/13/2022]
Abstract
The par-titioning-defective or PAR proteins comprise the core of an essential cell polarity network that underlies polarization in a wide variety of cell types and developmental contexts. The output of this network in nearly every case is the establishment of opposing and complementary membrane domains that define a cell׳s polarity axis. Yet, behind this simple pattern is a complex system of interactions, regulation and dynamic behaviors. How these various parts combine to generate polarized patterns of protein localization in cells is only beginning to become clear. This review, part of the Special Issue on Cell Polarity, aims to highlight several emerging themes and design principles that underlie the process of cell polarization by components of the PAR network.
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Affiliation(s)
- Nathan W Goehring
- Cancer Research UK London Research Institute, 44 Lincoln׳s Inn Fields, London WC2A 3LY, UK; MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK.
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27
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Actomyosin regulation and symmetry breaking in a model of polarization in the early Caenorhabditis elegans embryo : symmetry breaking in cell polarization. Bull Math Biol 2014; 76:2426-48. [PMID: 25185748 DOI: 10.1007/s11538-014-0016-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2014] [Accepted: 08/21/2014] [Indexed: 12/21/2022]
Abstract
Polarization, whereby a cell defines a spatial axis by segregating specific determinants to distinct regions, is an essential and highly conserved biological process. The process of polarization is initiated by a cue that breaks an initially symmetric distribution of determinants, allowing for a spatially asymmetric redistribution. The nature of this cue is currently not well understood. Utilizing the conservation of polarization process and its determinants, we theoretically investigate the nature of the cue and the regulation of contractility that enables the establishment of polarity in early embryos of the nematode worm Caenorhabditis elegans (C. elegans). Our biologically based model, which consists of coupled partial differential equations, suggests that a biochemical but not mechanical cue is sufficient for symmetry breaking, and inhibition of contractile elements by specific determinants is needed for sustained spatial redistribution.
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28
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Dodgson J, Chessel A, Yamamoto M, Vaggi F, Cox S, Rosten E, Albrecht D, Geymonat M, Csikasz-Nagy A, Sato M, Carazo-Salas RE. Spatial segregation of polarity factors into distinct cortical clusters is required for cell polarity control. Nat Commun 2013; 4:1834. [PMID: 23673619 PMCID: PMC3674234 DOI: 10.1038/ncomms2813] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2012] [Accepted: 03/26/2013] [Indexed: 01/06/2023] Open
Abstract
Cell polarity is regulated by evolutionarily conserved polarity factors whose precise higher-order organization at the cell cortex is largely unknown. Here we image frontally the cortex of live fission yeast cells using time-lapse and super-resolution microscopy. Interestingly, we find that polarity factors are organized in discrete cortical clusters resolvable to ~50–100 nm in size, which can form and become cortically enriched by oligomerization. We show that forced co-localization of the polarity factors Tea1 and Tea3 results in polarity defects, suggesting that the maintenance of both factors in distinct clusters is required for polarity. However, during mitosis, their co-localization increases, and Tea3 helps to retain the cortical localization of the Tea1 growth landmark in preparation for growth reactivation following mitosis. Thus, regulated spatial segregation of polarity factor clusters provides a means to spatio-temporally control cell polarity at the cell cortex. We observe similar clusters in Saccharomyces cerevisiae and Caenorhabditis elegans cells, indicating this could be a universal regulatory feature. Cell polarity is generated and maintained by the spatial accumulation of polarity factors. By imaging fission yeast cells ‘end-on’, the authors show that the polarity factors Tea1 and Tea3 segregate into distinct clusters, and that surprisingly, their segregation is critical for cell polarization.
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Affiliation(s)
- James Dodgson
- The Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, UK
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29
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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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30
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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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31
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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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32
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Pittman KJ, Skop AR. Anterior PAR proteins function during cytokinesis and maintain DYN-1 at the cleavage furrow in Caenorhabditis elegans. Cytoskeleton (Hoboken) 2012; 69:826-39. [PMID: 22887994 DOI: 10.1002/cm.21053] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2012] [Revised: 07/16/2012] [Accepted: 07/17/2012] [Indexed: 12/25/2022]
Abstract
PAR proteins are key regulators of cellular polarity and have links to the endocytic machinery and the actin cytoskeleton. Our data suggest a unique role for PAR proteins in cytokinesis. We have found that at the onset of cytokinesis, anterior PAR-6 and posterior PAR-2 proteins are redistributed to the furrow membrane in a temporal and spatial manner. PAR-6 and PAR-2 localize to the furrow membrane during ingression but PAR-2-GFP is distinct in that it is excluded from the extreme tip of the furrow. Once the midbody has formed, PAR-2-GFP becomes restricted to the midbody region (the midbody plus the membrane flanking it). Depletion of both anterior PAR proteins, PAR-3 and PAR-6, led to an increase in multinucleate embryos, suggesting that the anterior PAR proteins are necessary during cytokinesis and that PAR-3 and PAR-6 function in cytokinesis may be partially redundant. Lastly, anterior PAR proteins play a role in the maintenance of DYN-1 in the cleavage furrow. Our data indicate that the PAR proteins are involved in the events that occur during cytokinesis and may play a role in promoting the membrane trafficking and remodeling events that occur during this time.
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Affiliation(s)
- Kelly J Pittman
- Laboratory of Genetics and Medical Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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33
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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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34
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Motegi F, Zonies S, Hao Y, Cuenca AA, Griffin E, Seydoux G. Microtubules induce self-organization of polarized PAR domains in Caenorhabditis elegans zygotes. Nat Cell Biol 2011; 13:1361-7. [PMID: 21983565 PMCID: PMC3208083 DOI: 10.1038/ncb2354] [Citation(s) in RCA: 126] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Accepted: 09/05/2011] [Indexed: 02/06/2023]
Abstract
A hallmark of polarized cells is the segregation of the PAR polarity regulators into asymmetric domains at the cell cortex1, 2. Antagonistic interactions involving two conserved kinases, atypical protein kinase C (aPKC) and PAR-1, have been implicated in polarity maintenance1, 2, but the mechanisms that initiate the formation of asymmetric PAR domains are not understood. Here, we describe one pathway used by the sperm-donated centrosome to polarize the PAR proteins in Caenorhabditis elegans zygotes. Before polarization, cortical aPKC excludes PAR-1 kinase and its binding partner PAR-2 by phosphorylation. During symmetry breaking, microtubules nucleated by the centrosome locally protect PAR-2 from phosphorylation by aPKC, allowing PAR-2 and PAR-1 to access the cortex nearest the centrosome. Cortical PAR-1 phosphorylates PAR-3, causing the PAR-3/aPKC complex to leave the cortex. Our findings illustrate how microtubules, independent of actin dynamics, stimulate the self-organization of PAR proteins by providing local protection against a global barrier imposed by aPKC.
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Affiliation(s)
- Fumio Motegi
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Center for Cell Dynamics, Johns Hopkins University School of Medicine, 725 N. Wolfe St., PCTB 706, Baltimore, Maryland 21205, USA
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35
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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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36
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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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