1
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Chong TN, Panjalingam M, Saurabh S, Shapiro L. Phosphatase to kinase switch of a critical enzyme contributes to timing of cell differentiation. mBio 2024; 15:e0212523. [PMID: 38055339 PMCID: PMC10790692 DOI: 10.1128/mbio.02125-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Accepted: 10/20/2023] [Indexed: 12/08/2023] Open
Abstract
IMPORTANCE The process of cell differentiation is highly regulated in both prokaryotic and eukaryotic organisms. The aquatic bacterium, Caulobacter crescentus, undergoes programmed cell differentiation from a motile swarmer cell to a stationary stalked cell with each cell cycle. This critical event is regulated at multiple levels. Kinase activity of the bifunctional enzyme, PleC, is limited to a brief period when it initiates the molecular signaling cascade that results in cell differentiation. Conversely, PleC phosphatase activity is required for pili formation and flagellar rotation. We show that PleC is localized to the flagellar pole by the scaffold protein, PodJ, which is known to suppress PleC kinase activity in vitro. PleC mutants that are unable to bind PodJ have increased kinase activity in vivo, resulting in premature differentiation. We propose a model in which PodJ regulation of PleC's enzymatic activity contributes to the robust timing of cell differentiation during the Caulobacter cell cycle.
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Affiliation(s)
- Trisha N. Chong
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, California, USA
| | - Mayura Panjalingam
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, California, USA
| | - Saumya Saurabh
- Department of Chemistry, New York University, New York, New York, USA
| | - Lucy Shapiro
- Department of Developmental Biology, Stanford University School of Medicine, Stanford, California, USA
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2
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Lu N, Duvall SW, Zhao G, Kowallis KA, Zhang C, Tan W, Sun J, Petitjean HN, Tomares DT, Zhao GP, Childers WS, Zhao W. Scaffold-Scaffold Interaction Facilitates Cell Polarity Development in Caulobacter crescentus. mBio 2023; 14:e0321822. [PMID: 36971555 PMCID: PMC10127582 DOI: 10.1128/mbio.03218-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023] Open
Abstract
Caulobacter crescentus
is a well-established bacterial model to study asymmetric cell division for decades. During cell development, the polarization of scaffold protein PopZ from monopolar to bipolar plays a central role in
C. crescentus
asymmetric cell division.
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3
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Goodsell DS, Lasker K. Integrative visualization of the molecular structure of a cellular microdomain. Protein Sci 2023; 32:e4577. [PMID: 36700303 PMCID: PMC9926476 DOI: 10.1002/pro.4577] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Revised: 01/16/2023] [Accepted: 01/23/2023] [Indexed: 01/27/2023]
Abstract
An integrative approach to visualization is used to create a visual snapshot of the structural biology of the polar microdomain of Caulobacter crescentus. The visualization is based on the current state of molecular and cellular knowledge of the microdomain and its cellular context. The collaborative process of researching and executing the visualization has identified aspects that are well determined and areas that require further study. The visualization is useful for dissemination, education, and outreach, and the study lays the groundwork for future 3D modeling and simulation of this well-studied example of a cellular condensate.
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Affiliation(s)
- David S Goodsell
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, USA.,Research Collaboratory for Structural Bioinformatics Protein Data Bank, Rutgers, The State University of New Jersey, Piscataway, New Jersey, USA.,Institute for Quantitative Biomedicine, Rutgers, The State University of New Jersey, Piscataway, New Jersey, USA.,Rutgers Cancer Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
| | - Keren Lasker
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California, USA
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4
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Tan W, Cheng S, Li Y, Li XY, Lu N, Sun J, Tang G, Yang Y, Cai K, Li X, Ou X, Gao X, Zhao GP, Childers WS, Zhao W. Phase separation modulates the assembly and dynamics of a polarity-related scaffold-signaling hub. Nat Commun 2022; 13:7181. [PMID: 36418326 PMCID: PMC9684454 DOI: 10.1038/s41467-022-35000-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Accepted: 11/14/2022] [Indexed: 11/26/2022] Open
Abstract
Asymmetric cell division (ACD) produces morphologically and behaviorally distinct cells and is the primary way to generate cell diversity. In the model bacterium Caulobacter crescentus, the polarization of distinct scaffold-signaling hubs at the swarmer and stalked cell poles constitutes the basis of ACD. However, mechanisms involved in the formation of these hubs remain elusive. Here, we show that a swarmer-cell-pole scaffold, PodJ, forms biomolecular condensates both in vitro and in living cells via phase separation. The coiled-coil 4-6 and the intrinsically disordered regions are the primary domains that contribute to biomolecular condensate generation and signaling protein recruitment in PodJ. Moreover, a negative regulation of PodJ phase separation by the stalked-cell-pole scaffold protein SpmX is revealed. SpmX impedes PodJ cell-pole accumulation and affects its recruitment ability. Together, by modulating the assembly and dynamics of scaffold-signaling hubs, phase separation may serve as a general biophysical mechanism that underlies the regulation of ACD in bacteria and other organisms.
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Affiliation(s)
- Wei Tan
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
| | - Sihua Cheng
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
| | - Yingying Li
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
| | - Xiao-Yang Li
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China ,grid.256922.80000 0000 9139 560XDepartment of Pharmacy, School of Life Sciences, Henan University, Kaifeng, 475004 China
| | - Ning Lu
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
| | - Jingxian Sun
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
| | - Guiyue Tang
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
| | - Yujiao Yang
- grid.9227.e0000000119573309CAS Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032 China ,grid.410726.60000 0004 1797 8419University of Chinese Academy of Sciences, Beijing, 100049 China
| | - Kezhu Cai
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China ,grid.263817.90000 0004 1773 1790Department of Materials Science and Engineering, School of Engineering, Southern University of Science and Technology, Shenzhen, 518055 China
| | - Xuefei Li
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
| | - Xijun Ou
- grid.263817.90000 0004 1773 1790Department of Biology, School of Life Sciences, Southern University of Science and Technology, Shenzhen, 518055 China
| | - Xiang Gao
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
| | - Guo-Ping Zhao
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China ,grid.9227.e0000000119573309CAS Key Laboratory of Synthetic Biology, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai, 200032 China ,grid.8547.e0000 0001 0125 2443State Key Lab of Genetic Engineering & Institutes of Biomedical Sciences, Department of Microbiology and Microbial Engineering, School of Life Sciences, Fudan University, Shanghai, 200433 China
| | - W. Seth Childers
- grid.21925.3d0000 0004 1936 9000Department of Chemistry, University of Pittsburgh, Pittsburgh, PA 15260 USA
| | - Wei Zhao
- grid.458489.c0000 0001 0483 7922CAS Key Laboratory of Quantitative Engineering Biology, Shenzhen Institute of Synthetic Biology, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, 518055 China
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5
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Zhang C, Zhao W, Duvall SW, Kowallis KA, Childers WS. Regulation of the activity of bacterial histidine kinase PleC by the scaffolding protein PodJ. J Biol Chem 2022; 298:101683. [PMID: 35124010 PMCID: PMC8980812 DOI: 10.1016/j.jbc.2022.101683] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Accepted: 01/31/2022] [Indexed: 12/11/2022] Open
Abstract
Scaffolding proteins can customize the response of signaling networks to support cell development and behaviors. PleC is a bifunctional histidine kinase whose signaling activity coordinates asymmetric cell division to yield a motile swarmer cell and a stalked cell in the gram-negative bacterium Caulobacter crescentus. Past studies have shown that PleC’s switch in activity from kinase to phosphatase correlates with a change in its subcellular localization pattern from diffuse to localized at the new cell pole. Here we investigated how the bacterial scaffolding protein PodJ regulates the subcellular positioning and activity of PleC. We reconstituted the PleC-PodJ signaling complex through both heterologous expressions in Escherichia coli and in vitro studies. In vitro, PodJ phase separates as a biomolecular condensate that recruits PleC and inhibits its kinase activity. We also constructed an in vivo PleC-CcaS chimeric histidine kinase reporter assay and demonstrated using this method that PodJ leverages its intrinsically disordered region to bind to PleC’s PAS sensory domain and regulate PleC-CcaS signaling. Regulation of the PleC-CcaS was most robust when PodJ was concentrated at the cell poles and was dependent on the allosteric coupling between PleC-CcaS’s PAS sensory domain and its downstream histidine kinase domain. In conclusion, our in vitro biochemical studies suggest that PodJ phase separation may be coupled to changes in PleC enzymatic function. We propose that this coupling of phase separation and allosteric regulation may be a generalizable phenomenon among enzymes associated with biomolecular condensates.
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6
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Computational modeling of unphosphorylated CtrA: Cori binding in the Caulobacter cell cycle. iScience 2021; 24:103413. [PMID: 34901785 PMCID: PMC8640480 DOI: 10.1016/j.isci.2021.103413] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 09/17/2021] [Accepted: 11/05/2021] [Indexed: 02/04/2023] Open
Abstract
In the alphaproteobacterium, Caulobacter crescentus, phosphorylated CtrA (CtrA∼P), a master regulatory protein, binds directly to the chromosome origin (Cori) to inhibit DNA replication. Using a mathematical model of CtrA binding at Cori site [d], we provide computational evidence that CtrAU can displace CtrA∼P from Cori at the G1-S transition. Investigation of this interaction within a detailed model of the C. crescentus cell cycle suggests that CckA phosphatase may clear Cori of CtrA∼P by altering the [CtrAU]/[CtrA∼P] ratio rather than by completely depleting CtrA∼P. Model analysis reveals that the mechanism allows for a speedier transition into S phase, stabilizes the timing of chromosome replication under fluctuating rates of CtrA proteolysis, and may contribute to the viability of numerous mutant strains. Overall, these results suggest that CtrAU enhances the robustness of chromosome replication. More generally, our proposed regulation of CtrA:Cori dynamics may represent a novel motif for molecular signaling in cell physiology.
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7
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Christen M, Beusch C, Bösch Y, Cerletti D, Flores-Tinoco CE, Del Medico L, Tschan F, Christen B. Quantitative Selection Analysis of Bacteriophage φCbK Susceptibility in Caulobacter crescentus. J Mol Biol 2015; 428:419-30. [PMID: 26593064 DOI: 10.1016/j.jmb.2015.11.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2015] [Revised: 11/16/2015] [Accepted: 11/17/2015] [Indexed: 11/25/2022]
Abstract
Classical molecular genetics uses stringent selective conditions to identify mutants with distinct phenotypic responses. Mutations giving rise to less pronounced phenotypes are often missed. However, to gain systems-level insights into complex genetic interaction networks requires genome-wide assignment of quantitative phenotypic traits. In this paper, we present a quantitative selection approach coupled with transposon sequencing (QS-TnSeq) to globally identify the cellular components that orchestrate susceptibility of the cell cycle model bacterium Caulobacter crescentus toward bacteriophage φCbK infection. We found that 135 genes representing 3.30% of the Caulobacter genome exhibit significant accumulation of transposon insertions upon φCbK selection. More than 85% thereof consist of new factors not previously associated with phage φCbK susceptibility. Using hierarchical clustering of dose-dependent TnSeq datasets, we grouped these genes into functional modules that correlate with different stages of the φCbK infection process. We assign φCbK susceptibility to eight new genes that represent novel components of the pilus secretion machinery. Further, we demonstrate that, from 86 motility genes, only seven genes encoding structural and regulatory components of the flagellar hook increase phage resistance when disrupted by transposons, suggesting a link between flagellar hook assembly and pili biogenesis. In addition, we observe high recovery of Tn5 insertions within regulatory sequences of the genes encoding the essential NADH:ubiquinone oxidoreductase complex indicating that intact proton motive force is crucial for effective phage propagation. In sum, QS-TnSeq is broadly applicable to perform quantitative and genome-wide systems-genetics analysis of complex phenotypic traits.
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Affiliation(s)
- Matthias Christen
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland
| | - Christian Beusch
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland
| | - Yvonne Bösch
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland
| | - Dario Cerletti
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland
| | - Carlos Eduardo Flores-Tinoco
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland; Life Science Zürich PhD Program on Systems Biology, Zürich, Switzerland
| | - Luca Del Medico
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland
| | - Flavia Tschan
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland
| | - Beat Christen
- Institute of Molecular Systems Biology, Eidgenössische Technische Hochschule (ETH) Zürich, CH-8093 Zürich, Switzerland.
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8
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PopZ identifies the new pole, and PodJ identifies the old pole during polar growth in Agrobacterium tumefaciens. Proc Natl Acad Sci U S A 2015; 112:11666-71. [PMID: 26324921 DOI: 10.1073/pnas.1515544112] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Agrobacterium tumefaciens elongates by addition of peptidoglycan (PG) only at the pole created by cell division, the growth pole, whereas the opposite pole, the old pole, is inactive for PG synthesis. How Agrobacterium assigns and maintains pole asymmetry is not understood. Here, we investigated whether polar growth is correlated with novel pole-specific localization of proteins implicated in a variety of growth and cell division pathways. The cell cycle of A. tumefaciens was monitored by time-lapse and superresolution microscopy to image the localization of A. tumefaciens homologs of proteins involved in cell division, PG synthesis and pole identity. FtsZ and FtsA accumulate at the growth pole during elongation, and improved imaging reveals FtsZ disappears from the growth pole and accumulates at the midcell before FtsA. The L,D-transpeptidase Atu0845 was detected mainly at the growth pole. A. tumefaciens specific pole-organizing protein (Pop) PopZAt and polar organelle development (Pod) protein PodJAt exhibited dynamic yet distinct behavior. PopZAt was found exclusively at the growing pole and quickly switches to the new growth poles of both siblings immediately after septation. PodJAt is initially at the old pole but then also accumulates at the growth pole as the cell cycle progresses suggesting that PodJAt may mediate the transition of the growth pole to an old pole. Thus, PopZAt is a marker for growth pole identity, whereas PodJAt identifies the old pole.
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9
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The essential features and modes of bacterial polar growth. Trends Microbiol 2015; 23:347-53. [PMID: 25662291 DOI: 10.1016/j.tim.2015.01.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2014] [Revised: 12/19/2014] [Accepted: 01/07/2015] [Indexed: 01/25/2023]
Abstract
Polar growth represents a surprising departure from the canonical dispersed cell growth model. However, we know relatively little of the underlying mechanisms governing polar growth or the requisite suite of factors that direct polar growth. Underscoring how classic doctrine can be turned on its head, the peptidoglycan layer of polar-growing bacteria features unusual crosslinks and in some species the quintessential cell division proteins FtsA and FtsZ are recruited to the growing poles. Remarkably, numerous medically important pathogens utilize polar growth, accentuating the need for intensive research in this area. Here we review models of polar growth in bacteria based on recent research in the Actinomycetales and Rhizobiales, with emphasis on Mycobacterium and Agrobacterium species.
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10
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Abstract
Bacteria are polarized cells with many asymmetrically localized proteins that are regulated temporally and spatially. This spatiotemporal dynamics is critical for several fundamental cellular processes including growth, division, cell cycle regulation, chromosome segregation, differentiation, and motility. Therefore, understanding how proteins find their correct location at the right time is crucial for elucidating bacterial cell function. Despite the diversity of proteins displaying spatiotemporal dynamics, general principles for the dynamic regulation of protein localization to the cell poles and the midcell are emerging. These principles include diffusion-capture, self-assembling polymer-forming landmark proteins, nonpolymer forming landmark proteins, matrix-dependent self-organizing ParA/MinD ATPases, and small Ras-like GTPases.
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Affiliation(s)
- Anke Treuner-Lange
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
| | - Lotte Søgaard-Andersen
- Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, 35043 Marburg, Germany
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11
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Ozaki S, Schalch-Moser A, Zumthor L, Manfredi P, Ebbensgaard A, Schirmer T, Jenal U. Activation and polar sequestration of PopA, a c-di-GMP effector protein involved in Caulobacter crescentus cell cycle control. Mol Microbiol 2014; 94:580-94. [PMID: 25171231 DOI: 10.1111/mmi.12777] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/27/2014] [Indexed: 01/12/2023]
Abstract
When Caulobacter crescentus enters S-phase the replication initiation inhibitor CtrA dynamically positions to the old cell pole to be degraded by the polar ClpXP protease. Polar delivery of CtrA requires PopA and the diguanylate cyclase PleD that positions to the same pole. Here we present evidence that PopA originated through gene duplication from its paralogue response regulator PleD and subsequent co-option as c-di-GMP effector protein. While the C-terminal catalytic domain (GGDEF) of PleD is activated by phosphorylation of the N-terminal receiver domain, functional adaptation has reversed signal transduction in PopA with the GGDEF domain adopting input function and the receiver domain serving as regulatory output. We show that the N-terminal receiver domain of PopA specifically interacts with RcdA, a component required for CtrA degradation. In contrast, the GGDEF domain serves to target PopA to the cell pole in response to c-di-GMP binding. In agreement with the divergent activation and targeting mechanisms, distinct markers sequester PleD and PopA to the old cell pole upon S-phase entry. Together these data indicate that PopA adopted a novel role as topology specificity factor to help recruit components of the CtrA degradation pathway to the protease specific old cell pole of C. crescentus.
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Affiliation(s)
- Shogo Ozaki
- Focal Area of Infection Biology, Biozentrum, University of Basel, 4056, Basel, Switzerland
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12
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Konovalova A, Søgaard-Andersen L, Kroos L. Regulated proteolysis in bacterial development. FEMS Microbiol Rev 2013; 38:493-522. [PMID: 24354618 DOI: 10.1111/1574-6976.12050] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2013] [Revised: 09/03/2013] [Accepted: 10/14/2013] [Indexed: 11/30/2022] Open
Abstract
Bacteria use proteases to control three types of events temporally and spatially during the processes of morphological development. These events are the destruction of regulatory proteins, activation of regulatory proteins, and production of signals. While some of these events are entirely cytoplasmic, others involve intramembrane proteolysis of a substrate, transmembrane signaling, or secretion. In some cases, multiple proteolytic events are organized into pathways, for example turnover of a regulatory protein activates a protease that generates a signal. We review well-studied and emerging examples and identify recurring themes and important questions for future research. We focus primarily on paradigms learned from studies of model organisms, but we note connections to regulated proteolytic events that govern bacterial adaptation, biofilm formation and disassembly, and pathogenesis.
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Affiliation(s)
- Anna Konovalova
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA
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13
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Abstract
It is now well appreciated that bacterial cells are highly organized, which is far from the initial concept that they are merely bags of randomly distributed macromolecules and chemicals. Central to their spatial organization is the precise positioning of certain proteins in subcellular domains of the cell. In particular, the cell poles - the ends of rod-shaped cells - constitute important platforms for cellular regulation that underlie processes as essential as cell cycle progression, cellular differentiation, virulence, chemotaxis and growth of appendages. Thus, understanding how the polar localization of specific proteins is achieved and regulated is a crucial question in bacterial cell biology. Often, polarly localized proteins are recruited to the poles through their interaction with other proteins or protein complexes that were already located there, in a so-called diffusion-and-capture mechanism. Bacteria are also starting to reveal their secrets on how the initial pole 'recognition' can occur and how this event can be regulated to generate dynamic, reproducible patterns in time (for example, during the cell cycle) and space (for example, at a specific cell pole). Here, we review the major mechanisms that have been described in the literature, with an emphasis on the self-organizing principles. We also present regulation strategies adopted by bacterial cells to obtain complex spatiotemporal patterns of protein localization.
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Affiliation(s)
- Géraldine Laloux
- de Duve Institute, Université Catholique de Louvain, B-1200 Brussels, Belgium
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14
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15
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Fields AT, Navarrete CS, Zare AZ, Huang Z, Mostafavi M, Lewis JC, Rezaeihaghighi Y, Brezler BJ, Ray S, Rizzacasa AL, Barnett MJ, Long SR, Chen EJ, Chen JC. The conserved polarity factor podJ1 impacts multiple cell envelope-associated functions in Sinorhizobium meliloti. Mol Microbiol 2012; 84:892-920. [PMID: 22553970 DOI: 10.1111/j.1365-2958.2012.08064.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Although diminutive in size, bacteria possess highly diverse and spatially confined cellular structures. Two related alphaproteobacteria, Sinorhizobium meliloti and Caulobacter crescentus, serve as models for investigating the genetic basis of morphological variations. S. meliloti, a symbiont of leguminous plants, synthesizes multiple flagella and no prosthecae, whereas C. crescentus, a freshwater bacterium, has a single polar flagellum and stalk. The podJ gene, originally identified in C. crescentus for its role in polar organelle development, is split into two adjacent open reading frames, podJ1 and podJ2, in S. meliloti. Deletion of podJ1 interferes with flagellar motility, exopolysaccharide production, cell envelope integrity, cell division and normal morphology, but not symbiosis. As in C. crescentus, the S. meliloti PodJ1 protein appears to act as a polarity beacon and localizes to the newer cell pole. Microarray analysis indicates that podJ1 affects the expression of at least 129 genes, the majority of which correspond to observed mutant phenotypes. Together, phenotypic characterization, microarray analysis and suppressor identification suggest that PodJ1 controls a core set of conserved elements, including flagellar and pili genes, the signalling proteins PleC and DivK, and the transcriptional activator TacA, while alternative downstream targets have evolved to suit the distinct lifestyles of individual species.
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Affiliation(s)
- Alexander T Fields
- Department of Biology, San Francisco State University, San Francisco, CA 94132, USA
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16
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Curtis PD, Quardokus EM, Lawler ML, Guo X, Klein D, Chen JC, Arnold RJ, Brun YV. The scaffolding and signalling functions of a localization factor impact polar development. Mol Microbiol 2012; 84:712-35. [PMID: 22512778 DOI: 10.1111/j.1365-2958.2012.08055.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
In the differentiating alphaproteobacterium Caulobacter crescentus, organelle synthesis at cell poles is critical to forming different progeny after cell division. Co-ordination of polar organelle synthesis, including pili and holdfast, and flagellum ejection, is mediated in part by the scaffolding protein PodJ. At the time of cell division, PodJ undergoes regulated processing to a short form that persists at the flagellar pole of swarmer cells. This study analyses how PodJ's role in structural and signalling protein localization impacts organelle synthesis. A PodJ mutant with an internal deletion exhibits reduced sensitivity to pili-tropic phage ΦCbK, resulting from reduced pilA gene expression, which can be linked to altered signalling protein localization. The phage sensitivity defect of a ΔpodJ mutant can be partially suppressed by ectopic pilA expression. Induction of PodJ processing, by manipulation of podJ itself or controlled perP expression, resulted in decreased pilus biogenesis and, when coupled with a podJ mutation that reduced pilA expression, led to complete loss of phage sensitivity. As a whole, the results show that PodJ's scaffolding role for structural and signalling proteins both contribute to flagellar pole organelle development.
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Affiliation(s)
- Patrick D Curtis
- Department of Biology, Indiana University, Bloomington, IN 47405, USA
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17
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Radhakrishnan SK, Viollier P. Two-in-one: bifunctional regulators synchronizing developmental events in bacteria. Trends Cell Biol 2012; 22:14-21. [DOI: 10.1016/j.tcb.2011.09.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2011] [Revised: 09/15/2011] [Accepted: 09/15/2011] [Indexed: 10/16/2022]
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18
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Kirkpatrick CL, Viollier PH. Decoding Caulobacter development. FEMS Microbiol Rev 2011; 36:193-205. [PMID: 22091823 DOI: 10.1111/j.1574-6976.2011.00309.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Revised: 09/15/2011] [Accepted: 09/15/2011] [Indexed: 11/27/2022] Open
Abstract
Caulobacter crescentus uses a multi-layered system of oscillating regulators to program different developmental fates into each daughter cell at division. This is achieved by superimposing gene expression, subcellular localization, phosphorylation, and regulated proteolysis to form a complex regulatory network that integrates chromosome replication, segregation, polar differentiation, and cytokinesis. In this review, we outline the current state of research in the field of Caulobacter development, emphasizing new findings that elaborate how the developmental program is modulated by factors such as the environment or the metabolic state of the cell.
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Affiliation(s)
- Clare L Kirkpatrick
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland
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19
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Chen G, Zhang X. New insights into S2P signaling cascades: regulation, variation, and conservation. Protein Sci 2011; 19:2015-30. [PMID: 20836086 DOI: 10.1002/pro.496] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Regulated intramembrane proteolysis (RIP) is a conserved mechanism that regulates signal transduction across the membrane by recruiting membrane-bound proteases to cleave membrane-spanning regulatory proteins. As the first identified protease that performs RIP, the metalloprotease site-2 protease (S2P) has received extensive study during the past decade, and an increasing number of S2P-like proteases have been identified and studied in different organisms; however, some of their substrates and the related S1Ps remain elusive. Here, we review recent research on S2P cascades, including human S2P, E. coli RseP, B. subtilis SpoIVFB and the newly identified S2P homologs. We also discuss the variation and conservation of characterized S2P cascades. The conserved catalytic motif of S2P and prevalence of amino acids of low helical propensity in the transmembrane segments of the substrates suggest a conserved catalytic conformation and mechanism within the S2P family. The review also sheds light on future research on S2P cascades.
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Affiliation(s)
- Gu Chen
- College of Light Industry and Food Sciences, South China University of Technology, Guangzhou 510640, China.
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20
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Getting in the loop: regulation of development in Caulobacter crescentus. Microbiol Mol Biol Rev 2010; 74:13-41. [PMID: 20197497 DOI: 10.1128/mmbr.00040-09] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Caulobacter crescentus is an aquatic Gram-negative alphaproteobacterium that undergoes multiple changes in cell shape, organelle production, subcellular distribution of proteins, and intracellular signaling throughout its life cycle. Over 40 years of research has been dedicated to this organism and its developmental life cycles. Here we review a portion of many developmental processes, with particular emphasis on how multiple processes are integrated and coordinated both spatially and temporally. While much has been discovered about Caulobacter crescentus development, areas of potential future research are also highlighted.
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21
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Hardy GG, Allen RC, Toh E, Long M, Brown PJB, Cole-Tobian JL, Brun YV. A localized multimeric anchor attaches the Caulobacter holdfast to the cell pole. Mol Microbiol 2010; 76:409-27. [PMID: 20233308 PMCID: PMC2908716 DOI: 10.1111/j.1365-2958.2010.07106.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Caulobacter crescentus attachment is mediated by the holdfast, a complex of polysaccharide anchored to the cell by HfaA, HfaB and HfaD. We show that all three proteins are surface exposed outer membrane (OM) proteins. HfaA is similar to fimbrial proteins and assembles into a high molecular weight (HMW) form requiring HfaD, but not holdfast polysaccharide. The HfaD HMW form is dependent on HfaA but not on holdfast polysaccharide. We show that HfaA and HfaD form homomultimers and that they require HfaB for stability and OM translocation. All three proteins localize to the late pre-divisional flagellar pole, remain at this pole in swarmer cells, and localize at the stalk tip after the stalk is synthesized at the same pole. Hfa protein localization requires the holdfast polysaccharide secretion proteins and the polar localization factor PodJ. An hfaB mutant is much more severely deficient in adherence and holdfast attachment than hfaA and hfaD mutants. An hfaA, hfaD double mutant phenocopies either single mutant, suggesting that HfaB is involved in holdfast attachment beyond secretion of HfaA and HfaD. We hypothesize that HfaB secretes HfaA and HfaD across the outer membrane, and the three proteins form a complex anchoring the holdfast to the stalk.
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Affiliation(s)
- Gail G. Hardy
- Department of Biology, Jordan Hall 142, Indiana University, 1001 E. 3 St., Bloomington, IN 47405
| | | | - Evelyn Toh
- Department of Biology, Jordan Hall 142, Indiana University, 1001 E. 3 St., Bloomington, IN 47405
| | | | - Pamela J. B. Brown
- Department of Biology, Jordan Hall 142, Indiana University, 1001 E. 3 St., Bloomington, IN 47405
| | | | - Yves V. Brun
- Department of Biology, Jordan Hall 142, Indiana University, 1001 E. 3 St., Bloomington, IN 47405
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22
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High-throughput identification of protein localization dependency networks. Proc Natl Acad Sci U S A 2010; 107:4681-6. [PMID: 20176934 DOI: 10.1073/pnas.1000846107] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Bacterial cells are highly organized with many protein complexes and DNA loci dynamically positioned to distinct subcellular sites over the course of a cell cycle. Such dynamic protein localization is essential for polar organelle development, establishment of asymmetry, and chromosome replication during the Caulobacter crescentus cell cycle. We used a fluorescence microscopy screen optimized for high-throughput to find strains with anomalous temporal or spatial protein localization patterns in transposon-generated mutant libraries. Automated image acquisition and analysis allowed us to identify genes that affect the localization of two polar cell cycle histidine kinases, PleC and DivJ, and the pole-specific pili protein CpaE, each tagged with a different fluorescent marker in a single strain. Four metrics characterizing the observed localization patterns of each of the three labeled proteins were extracted for hundreds of cell images from each of 854 mapped mutant strains. Using cluster analysis of the resulting set of 12-element vectors for each of these strains, we identified 52 strains with mutations that affected the localization pattern of the three tagged proteins. This information, combined with quantitative localization data from epitasis experiments, also identified all previously known proteins affecting such localization. These studies provide insights into factors affecting the PleC/DivJ localization network and into regulatory links between the localization of the pili assembly protein CpaE and the kinase localization pathway. Our high-throughput screening methodology can be adapted readily to any sequenced bacterial species, opening the potential for databases of localization regulatory networks across species, and investigation of localization network phylogenies.
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23
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The role of proteolysis in the Caulobacter crescentus cell cycle and development. Res Microbiol 2009; 160:687-95. [PMID: 19781638 DOI: 10.1016/j.resmic.2009.09.006] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Revised: 09/03/2009] [Accepted: 09/04/2009] [Indexed: 11/23/2022]
Abstract
Caulobacter crescentus cell cycle progression is implemented by oscillating global transcriptional regulators that establish temporal and spatial control of modular genetic subsystems during the cell cycle. The hierarchy of this regulatory circuit is established through a combination of gene expression control and regulated proteolysis. Recent results highlight the importance of spatial organization for controlled proteolysis in C. crescentus.
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24
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Duerig A, Abel S, Folcher M, Nicollier M, Schwede T, Amiot N, Giese B, Jenal U. Second messenger-mediated spatiotemporal control of protein degradation regulates bacterial cell cycle progression. Genes Dev 2009; 23:93-104. [PMID: 19136627 DOI: 10.1101/gad.502409] [Citation(s) in RCA: 229] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Second messengers control a wide range of important cellular functions in eukaryotes and prokaryotes. Here we show that cyclic di-GMP, a global bacterial second messenger, promotes cell cycle progression in Caulobacter crescentus by mediating the specific degradation of the replication initiation inhibitor CtrA. During the G1-to-S-phase transition, both CtrA and its cognate protease ClpXP dynamically localize to the old cell pole, where CtrA is rapidly degraded. Sequestration of CtrA to the cell pole depends on PopA, a newly identified cyclic di-GMP effector protein. PopA itself localizes to the cell pole and directs CtrA to this subcellular site via the direct interaction with a mediator protein, RcdA. We present evidence that c-di-GMP regulates CtrA degradation during the cell cycle by controlling the dynamic sequestration of the PopA recruitment factor to the cell pole. Furthermore, we show that cell cycle timing of CtrA degradation relies on converging pathways responsible for substrate and protease localization to the old cell pole. This is the first report that links cyclic di-GMP to protein dynamics and cell cycle control in bacteria.
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Affiliation(s)
- Anna Duerig
- Biozentrum, University of Basel, 4056 Basel, Switzerland
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25
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Complex regulatory pathways coordinate cell-cycle progression and development in Caulobacter crescentus. Adv Microb Physiol 2008; 54:1-101. [PMID: 18929067 DOI: 10.1016/s0065-2911(08)00001-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Caulobacter crescentus has become the predominant bacterial model system to study the regulation of cell-cycle progression. Stage-specific processes such as chromosome replication and segregation, and cell division are coordinated with the development of four polar structures: the flagellum, pili, stalk, and holdfast. The production, activation, localization, and proteolysis of specific regulatory proteins at precise times during the cell cycle culminate in the ability of the cell to produce two physiologically distinct daughter cells. We examine the recent advances that have enhanced our understanding of the mechanisms of temporal and spatial regulation that occur during cell-cycle progression.
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26
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Characterization of the Caulobacter crescentus holdfast polysaccharide biosynthesis pathway reveals significant redundancy in the initiating glycosyltransferase and polymerase steps. J Bacteriol 2008; 190:7219-31. [PMID: 18757530 DOI: 10.1128/jb.01003-08] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Caulobacter crescentus cells adhere to surfaces by using an extremely strong polar adhesin called the holdfast. The polysaccharide component of the holdfast is comprised in part of oligomers of N-acetylglucosamine. The genes involved in the export of the holdfast polysaccharide and the anchoring of the holdfast to the cell were previously discovered. In this study, we identified a cluster of polysaccharide biosynthesis genes (hfsEFGH) directly adjacent to the holdfast polysaccharide export genes. Sequence analysis indicated that these genes are involved in the biosynthesis of the minimum repeat unit of the holdfast polysaccharide. HfsE is predicted to be a UDP-sugar lipid-carrier transferase, the glycosyltransferase that catalyzes the first step in polysaccharide biosynthesis. HfsF is predicted to be a flippase, HfsG is a glycosyltransferase, and HfsH is similar to a polysaccharide (chitin) deacetylase. In-frame hfsG and hfsH deletion mutants resulted in severe deficiencies both in surface adhesion and in binding to the holdfast-specific lectin wheat germ agglutinin. In contrast, hfsE and hfsF mutants exhibited nearly wild-type levels of adhesion and holdfast synthesis. We identified three paralogs to hfsE, two of which are redundant to hfsE for holdfast synthesis. We also identified a redundant paralog to the hfsC gene, encoding the putative polysaccharide polymerase, and present evidence that the hfsE and hfsC paralogs, together with the hfs genes, are absolutely required for proper holdfast synthesis.
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27
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Lawler ML, Brun YV. Advantages and mechanisms of polarity and cell shape determination in Caulobacter crescentus. Curr Opin Microbiol 2007; 10:630-7. [PMID: 17997127 DOI: 10.1016/j.mib.2007.09.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2007] [Accepted: 09/14/2007] [Indexed: 11/19/2022]
Abstract
The tremendous diversity of bacterial cell shapes and the targeting of proteins and macromolecular complexes to specific subcellular sites strongly suggest that cellular organization provides important advantages to bacteria in their environment. Key advances have been made in the understanding of the mechanism and function of polarity and cell shape by studying the aquatic bacterium Caulobacter crescentus, whose cell cycle progression involves the ordered synthesis of different polar structures, and culminates in the biosynthesis of a thin polar cell envelope extension called the stalk. Recent results indicate that the important function of polar development is to maximize cell attachment to surfaces and to improve nutrient uptake by nonmotile and attached cells. Major progress has been made in understanding the regulatory network that coordinates polar development and morphogenesis and the role of polar localization of regulatory proteins.
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Affiliation(s)
- Melanie L Lawler
- Department of Biology, Indiana University, 1001 East Third Street, Bloomington, IN 47405-3700, USA
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28
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Collier J, Shapiro L. Spatial complexity and control of a bacterial cell cycle. Curr Opin Biotechnol 2007; 18:333-40. [PMID: 17709236 PMCID: PMC2716793 DOI: 10.1016/j.copbio.2007.07.007] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Accepted: 07/12/2007] [Indexed: 10/22/2022]
Abstract
A major breakthrough in understanding the bacterial cell cycle is the discovery that bacteria exhibit a high degree of intracellular organization. Chromosomal loci and many protein complexes are positioned at particular subcellular sites. In this review, we examine recently discovered control mechanisms that make use of dynamically localized protein complexes to orchestrate the Caulobacter crescentus cell cycle. Protein localization, notably of signal transduction proteins, chromosome partition proteins, and proteases, serves to coordinate cell division with chromosome replication and cell differentiation. The developmental fate of daughter cells is decided before completion of cytokinesis, via the early establishment of cell polarity by the distribution of activated signaling proteins, bacterial cytoskeleton, and landmark proteins.
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Affiliation(s)
| | - Lucy Shapiro
- To whom correspondence should be addressed. Lucy Shapiro: E-mail: . Telephone: 650 858 1864, Fax: 650 725 7739, Justine Collier: E-mail: , Telephone: 650 725 7603, Fax: 650 7257739
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29
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Ebersbach G, Jacobs-Wagner C. Exploration into the spatial and temporal mechanisms of bacterial polarity. Trends Microbiol 2007; 15:101-8. [PMID: 17275310 DOI: 10.1016/j.tim.2007.01.004] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 01/04/2007] [Accepted: 01/23/2007] [Indexed: 10/23/2022]
Abstract
The recognition of bacterial asymmetry is not new: the first high-resolution microscopy studies revealed that bacteria come in a multitude of shapes and sometimes carry asymmetrically localized external structures such as flagella on the cell surface. Even so, the idea that bacteria could have an inherent overall polarity, which affects not only their outer appearance but also many of their vital processes, has only recently been appreciated. In this review, we focus on recent advances in our understanding of the molecular mechanisms underlying the establishment of polarized functions and cell polarity in bacteria.
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Affiliation(s)
- Gitte Ebersbach
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, CT 06520, USA
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30
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Mittl PRE, Schneider-Brachert W. Sel1-like repeat proteins in signal transduction. Cell Signal 2006; 19:20-31. [PMID: 16870393 DOI: 10.1016/j.cellsig.2006.05.034] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2006] [Accepted: 05/23/2006] [Indexed: 02/06/2023]
Abstract
Solenoid proteins, which are distinguished from general globular proteins by their modular architectures, are frequently involved in signal transduction pathways. Proteins from the tetratricopeptide repeat (TPR) and Sel1-like repeat (SLR) families share similar alpha-helical conformations but different consensus sequence lengths and superhelical topologies. Both families are characterized by low sequence similarity levels, rendering the identification of functional homologous difficult. Therefore current knowledge of the molecular and cellular functions of the SLR proteins Sel1, Hrd3, Chs4, Nif1, PodJ, ExoR, AlgK, HcpA, Hsp12, EnhC, LpnE, MotX, and MerG has been reviewed. Although SLR proteins possess different cellular functions they all seem to serve as adaptor proteins for the assembly of macromolecular complexes. Sel1, Hrd3, Hsp12 and LpnE are activated under cellular stress. The eukaryotic Sel1 and Hrd3 proteins are involved in the ER-associated protein degradation, whereas the bacterial LpnE, EnhC, HcpA, ExoR, and AlgK proteins mediate the interactions between bacterial and eukaryotic host cells. LpnE and EnhC are responsible for the entry of L. pneumophila into epithelial cells and macrophages. ExoR from the symbiotic microorganism S. melioti and AlgK from the pathogen P. aeruginosa regulate exopolysaccaride synthesis. Nif1 and Chs4 from yeast are responsible for the regulation of mitosis and septum formation during cell division, respectively, and PodJ guides the cellular differentiation during the cell cycle of the bacterium C. crescentus. Taken together the SLR motif establishes a link between signal transduction pathways from eukaryotes and bacteria. The SLR motif is so far absent from archaea. Therefore the SLR could have developed in the last common ancestor between eukaryotes and bacteria.
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Affiliation(s)
- Peer R E Mittl
- Biochemisches Institut, Universität Zürich, Winterthurer Strasse 190, 8057 Zürich, Switzerland.
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31
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Abstract
Many cells divide asymmetrically by generating two different cell ends or poles prior to cell division, but the mechanisms by which cells distinguish one pole from the other is poorly understood. In this issue of Cell, Huitema et al. (2006) and Lam et al. (2006) describe a protein that defines one specific pole of a bacterial cell by localizing to the site of cell division to be inherited by both progeny at the resulting new poles.
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Affiliation(s)
- Melanie L Lawler
- Department of Biology, Indiana University, Bloomington, Indiana 47405, USA
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32
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Chen JC, Hottes AK, McAdams HH, McGrath PT, Viollier PH, Shapiro L. Cytokinesis signals truncation of the PodJ polarity factor by a cell cycle-regulated protease. EMBO J 2006; 25:377-86. [PMID: 16395329 PMCID: PMC1383518 DOI: 10.1038/sj.emboj.7600935] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2005] [Accepted: 12/02/2005] [Indexed: 11/08/2022] Open
Abstract
We demonstrate that successive cleavage events involving regulated intramembrane proteolysis (Rip) occur as a function of time during the Caulobacter cell cycle. The proteolytic substrate PodJ(L) is a polar factor that recruits proteins required for polar organelle biogenesis to the correct cell pole at a defined time in the cell cycle. We have identified a periplasmic protease (PerP) that initiates the proteolytic sequence by truncating PodJ(L) to a form with altered activity (PodJ(S)). Expression of perP is regulated by a signal transduction system that activates cell type-specific transcription programs and conversion of PodJ(L) to PodJ(S) in response to the completion of cytokinesis. PodJ(S), sequestered to the progeny swarmer cell, is subsequently released from the polar membrane by the membrane metalloprotease MmpA for degradation during the swarmer-to-stalked cell transition. This sequence of proteolytic events contributes to the asymmetric localization of PodJ isoforms to the appropriate cell pole. Thus, temporal activation of the PerP protease and spatial restriction of the polar PodJ(L) substrate cooperatively control the cell cycle-dependent onset of Rip.
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Affiliation(s)
- Joseph C Chen
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Alison K Hottes
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Harley H McAdams
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Patrick T McGrath
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
- Department of Physics, Stanford University, Stanford, CA, USA
| | - Patrick H Viollier
- Department of Molecular Biology and Microbiology, Case Western Reserve University, Cleveland, OH, USA
| | - Lucy Shapiro
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
- Department of Developmental Biology, Stanford University, Beckman Center B300, Stanford, CA 94305, USA. Tel.: +1 650 725 7678; Fax: +1 650 725 7739; E-mail:
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