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Smith EL, Panis G, Woldemeskel SA, Viollier PH, Chien P, Goley ED. Regulation of the transcription factor CdnL promotes adaptation to nutrient stress in Caulobacter. PNAS NEXUS 2024; 3:pgae154. [PMID: 38650860 PMCID: PMC11034885 DOI: 10.1093/pnasnexus/pgae154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Accepted: 04/03/2024] [Indexed: 04/25/2024]
Abstract
In response to nutrient deprivation, bacteria activate a conserved stress response pathway called the stringent response (SR). During SR activation in Caulobacter crescentus, SpoT synthesizes the secondary messengers guanosine 5'-diphosphate 3'-diphosphate and guanosine 5'-triphosphate 3'-diphosphate (collectively known as (p)ppGpp), which affect transcription by binding RNA polymerase (RNAP) to down-regulate anabolic genes. (p)ppGpp also impacts the expression of anabolic genes by controlling the levels and activities of their transcriptional regulators. In Caulobacter, a major regulator of anabolic genes is the transcription factor CdnL. If and how CdnL is controlled during the SR and why that might be functionally important are unclear. In this study, we show that CdnL is down-regulated posttranslationally during starvation in a manner dependent on SpoT and the ClpXP protease. Artificial stabilization of CdnL during starvation causes misregulation of ribosomal and metabolic genes. Functionally, we demonstrate that the combined action of SR transcriptional regulators and CdnL clearance allows for rapid adaptation to nutrient repletion. Moreover, cells that are unable to clear CdnL during starvation are outcompeted by wild-type cells when subjected to nutrient fluctuations. We hypothesize that clearance of CdnL during the SR, in conjunction with direct binding of (p)ppGpp and DksA to RNAP, is critical for altering the transcriptome in order to permit cell survival during nutrient stress.
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Affiliation(s)
- Erika L Smith
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Gaël Panis
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva 1211, Switzerland
| | - Selamawit Abi Woldemeskel
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Patrick H Viollier
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva 1211, Switzerland
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, University of Massachusetts-Amherst, Amherst, MA 01003, USA
| | - Erin D Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
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Smith EL, Panis G, Woldemeskel SA, Viollier PH, Chien P, Goley ED. Regulation of the transcription factor CdnL promotes adaptation to nutrient stress in Caulobacter. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.20.572625. [PMID: 38187569 PMCID: PMC10769358 DOI: 10.1101/2023.12.20.572625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2024]
Abstract
In response to nutrient deprivation, bacteria activate a conserved stress response pathway called the stringent response (SR). During SR activation in Caulobacter crescentus, SpoT synthesizes the secondary messengers (p)ppGpp, which affect transcription by binding RNA polymerase to downregulate anabolic genes. (p)ppGpp also impacts expression of anabolic genes by controlling the levels and activities of their transcriptional regulators. In Caulobacter, a major regulator of anabolic genes is the transcription factor CdnL. If and how CdnL is controlled during the SR and why that might be functionally important is unclear. Here, we show that CdnL is downregulated post-translationally during starvation in a manner dependent on SpoT and the ClpXP protease. Inappropriate stabilization of CdnL during starvation causes misregulation of ribosomal and metabolic genes. Functionally, we demonstrate that the combined action of SR transcriptional regulators and CdnL clearance allows for rapid adaptation to nutrient repletion. Moreover, cells that are unable to clear CdnL during starvation are outcompeted by wild-type cells when subjected to nutrient fluctuations. We hypothesize that clearance of CdnL during the SR, in conjunction with direct binding of (p)ppGpp and DksA to RNAP, is critical for altering the transcriptome in order to permit cell survival during nutrient stress.
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Affiliation(s)
- Erika L. Smith
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205
| | - Gaäl Panis
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland, 1211
| | - Selamawit Abi Woldemeskel
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205
- BlueRock Therapeutics, Cambridge, Massachusetts, 02142 (current)
| | - Patrick H. Viollier
- Department of Microbiology and Molecular Medicine, University of Geneva, Geneva, Switzerland, 1211
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, University of Massachusetts-Amherst, Amherst, Massachusetts, 01003
| | - Erin D. Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 21205
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Ahmed YM, Bowman GR. Phospho-signaling couples polar asymmetry and proteolysis within a membraneless microdomain in C. crescentus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.19.553945. [PMID: 37645878 PMCID: PMC10462113 DOI: 10.1101/2023.08.19.553945] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Asymmetric cell division in bacteria is achieved through cell polarization, where regulatory proteins are directed to specific cell poles. Curiously, both poles contain a membraneless microdomain, established by the polar assembly hub PopZ, through most of the cell cycle, yet many PopZ clients are unipolar and transiently localized. We find that PopZ's interaction with the response regulator CpdR is controlled by phosphorylation, via the histidine kinase CckA. Phosphorylated CpdR does not interact with PopZ and is not localized to cell poles. At poles where CckA acts as a phosphatase, de-phosphorylated CpdR binds directly with PopZ and subsequently recruits ClpX, substrates, and other members of a protease complex to the cell pole. We also find that co-recruitment of protease components and substrates to polar microdomains enhances their coordinated activity. This study connects phosphosignaling with polar assembly and the activity of a protease that triggers cell cycle progression and cell differentiation.
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Affiliation(s)
- Yasin M Ahmed
- Department of Molecular Biology, University of Wyoming, Laramie Wyoming 82071
| | - Grant R Bowman
- Department of Molecular Biology, University of Wyoming, Laramie Wyoming 82071
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4
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Synchronized Swarmers and Sticky Stalks: Caulobacter crescentus as a Model for Bacterial Cell Biology. J Bacteriol 2023; 205:e0038422. [PMID: 36715542 PMCID: PMC9945503 DOI: 10.1128/jb.00384-22] [Citation(s) in RCA: 17] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
First isolated and classified in the 1960s, Caulobacter crescentus has been instrumental in the study of bacterial cell biology and differentiation. C. crescentus is a Gram-negative alphaproteobacterium that exhibits a dimorphic life cycle composed of two distinct cell types: a motile swarmer cell and a nonmotile, division-competent stalked cell. Progression through the cell cycle is accentuated by tightly controlled biogenesis of appendages, morphological transitions, and distinct localization of developmental regulators. These features as well as the ability to synchronize populations of cells and follow their progression make C. crescentus an ideal model for answering questions relevant to how development and differentiation are achieved at the single-cell level. This review will explore the discovery and development of C. crescentus as a model organism before diving into several key features and discoveries that have made it such a powerful organism to study. Finally, we will summarize a few of the ongoing areas of research that are leveraging knowledge gained over the last century with C. crescentus to highlight its continuing role at the forefront of cell and developmental biology.
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5
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Ge Z, Yuan P, Chen L, Chen J, Shen D, She Z, Lu Y. New Global Insights on the Regulation of the Biphasic Life Cycle and Virulence Via ClpP-Dependent Proteolysis in Legionella pneumophila. Mol Cell Proteomics 2022; 21:100233. [PMID: 35427813 PMCID: PMC9112007 DOI: 10.1016/j.mcpro.2022.100233] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Revised: 02/17/2022] [Accepted: 04/07/2022] [Indexed: 01/11/2023] Open
Abstract
Legionella pneumophila, an environmental bacterium that parasitizes protozoa, causes Legionnaires’ disease in humans that is characterized by severe pneumonia. This bacterium adopts a distinct biphasic life cycle consisting of a nonvirulent replicative phase and a virulent transmissive phase in response to different environmental conditions. Hence, the timely and fine-tuned expression of growth and virulence factors in a life cycle–dependent manner is crucial for survival and replication. Here, we report that the completion of the biphasic life cycle and bacterial pathogenesis is greatly dependent on the protein homeostasis regulated by caseinolytic protease P (ClpP)-dependent proteolysis. We characterized the ClpP-dependent dynamic profiles of the regulatory and substrate proteins during the biphasic life cycle of L. pneumophila using proteomic approaches and discovered that ClpP-dependent proteolysis specifically and conditionally degraded the substrate proteins, thereby directly playing a regulatory role or indirectly controlling cellular events via the regulatory proteins. We further observed that ClpP-dependent proteolysis is required to monitor the abundance of fatty acid biosynthesis–related protein Lpg0102/Lpg0361/Lpg0362 and SpoT for the normal regulation of L. pneumophila differentiation. We also found that the control of the biphasic life cycle and bacterial virulence is independent. Furthermore, the ClpP-dependent proteolysis of Dot/Icm (defect in organelle trafficking/intracellular multiplication) type IVB secretion system and effector proteins at a specific phase of the life cycle is essential for bacterial pathogenesis. Therefore, our findings provide novel insights on ClpP-dependent proteolysis, which spans a broad physiological spectrum involving key metabolic pathways that regulate the transition of the biphasic life cycle and bacterial virulence of L. pneumophila, facilitating adaptation to aquatic and intracellular niches. ClpP is the major determinant of biphasic life cycle–dependent protein turnover. ClpP-dependent proteolysis monitors SpoT abundance for cellular differentiation. ClpP-dependent regulation of life cycle and bacterial virulence is independent. ClpP-dependent proteolysis of T4BSS and effector proteins is vital for virulence.
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Affiliation(s)
- Zhenhuang Ge
- School of Chemistry, Sun Yat-sen University, Guangzhou, China; School of Life Sciences, Sun Yat-sen University, Guangzhou, China; Run Ze Laboratory for Gastrointestinal Microbiome Study, Sun Yat-sen University, Guangzhou, China
| | - Peibo Yuan
- Microbiome Medicine Center, Division of Laboratory Medicine, Zhujiang Hospital, Southern Medical University, Guangzhou, China
| | - Lingming Chen
- Zhongshan School of Medicine, Sun Yat-sen University, Guangzhou, China
| | - Junyi Chen
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China; Run Ze Laboratory for Gastrointestinal Microbiome Study, Sun Yat-sen University, Guangzhou, China
| | - Dong Shen
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China
| | - Zhigang She
- School of Chemistry, Sun Yat-sen University, Guangzhou, China
| | - Yongjun Lu
- School of Life Sciences, Sun Yat-sen University, Guangzhou, China; Run Ze Laboratory for Gastrointestinal Microbiome Study, Sun Yat-sen University, Guangzhou, China.
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Fatima NI, Fazili KM, Bhat NH. Proteolysis dependent cell cycle regulation in Caulobacter crescentus. Cell Div 2022; 17:3. [PMID: 35365160 PMCID: PMC8973945 DOI: 10.1186/s13008-022-00078-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2021] [Accepted: 02/22/2022] [Indexed: 11/10/2022] Open
Abstract
Caulobacter crescentus, a Gram-negative alpha-proteobacterium, has surfaced as a powerful model system for unraveling molecular networks that control the bacterial cell cycle. A straightforward synchronization protocol and existence of many well-defined developmental markers has allowed the identification of various molecular circuits that control the underlying differentiation processes executed at the level of transcription, translation, protein localization and dynamic proteolysis. The oligomeric AAA+ protease ClpXP is a well-characterized example of an enzyme that exerts post-translational control over a number of pathways. Also, the proteolytic pathways of its candidate proteins are reported to play significant roles in regulating cell cycle and protein quality control. A detailed evaluation of the impact of its proteolysis on various regulatory networks of the cell has uncovered various significant cellular roles of this protease in C. crescentus. A deeper insight into the effects of regulatory proteolysis with emphasis on cell cycle progression could shed light on how cells respond to environmental cues and implement developmental switches. Perturbation of this network of molecular machines is also associated with diseases such as bacterial infections. Thus, research holds immense implications in clinical translation and health, representing a promising area for clinical advances in the diagnosis, therapeutics and prognosis.
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Affiliation(s)
- Nida I Fatima
- Department of Biotechnology, University of Kashmir, Hazratbal, Srinagar, Jammu and Kashmir, 190006, India
| | - Khalid Majid Fazili
- Department of Biotechnology, University of Kashmir, Hazratbal, Srinagar, Jammu and Kashmir, 190006, India
| | - Nowsheen Hamid Bhat
- Department of Biotechnology, Central University of Kashmir, Ganderbal, Jammu and Kashmir, 191201, India.
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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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Kohga H, Saito Y, Kanamaru M, Uchiyama J, Ohta H. The lack of the cell division protein FtsZ induced generation of giant cells under acidic stress in cyanobacterium Synechocystis sp. PCC6803. PHOTOSYNTHESIS RESEARCH 2021; 150:343-356. [PMID: 33146872 DOI: 10.1007/s11120-020-00792-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 10/23/2020] [Indexed: 06/11/2023]
Abstract
Bacteria exposed to environmental stresses often exhibit superior acclimation abilities to environmental change. Acid treatment causes an increase in the cell length of the cyanobacterium Synechocystis sp. PCC6803 under light conditions. We aimed to elucidate the relationship between acidic stress and cell enlargement. After being synchronized under dark conditions, the cells were cultivated at different pH (pH 8.0 or pH 6.0) levels under light conditions. Synechocystis 6803 cells exhibited only cell growth occurred (cell volume expansion) and slow proliferation under the acidic condition. In the recovery experiment of the enlarged cells, they proliferated normally at pH 8.0, and the cell lengths decreased to the normal cell size under light conditions. Inhibition of cell division might be caused by acidic stress. To understand the effect of acidic stress on cell division, we evaluated the expression of FtsZ via Western blotting. The FtsZ concentration in cells was lower at pH 6.0 than at pH 8.0 and was not sufficient for cell division in the photoautotrophic conditions. ClpXP is well known as a regulator of the Z-ring dynamics in E. coli. The transcriptional level of four clpXP genes was upregulated approximately threefold at pH 6.0 after 24 h compared with that in cells grown at pH 8.0. The lack of FtsZ may be caused by the upregulation of clpXP expression under acidic condition. Therefore, ClpXP may participate in the degradation of FtsZ and be involved in the regulation of cell division via FtsZ under acidic stress in Synechocystis 6803.
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Affiliation(s)
- Hidetaka Kohga
- Department of Mathematics and Science Education, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8601, Japan
| | - Yoshikazu Saito
- Department of Mathematics and Science Education, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8601, Japan
| | - Mirai Kanamaru
- Department of Mathematics and Science Education, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8601, Japan
| | - Junji Uchiyama
- Department of Mathematics and Science Education, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8601, Japan
- Department of Biology, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8601, Japan
| | - Hisataka Ohta
- Department of Mathematics and Science Education, Graduate School of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8601, Japan.
- Department of Biology, Faculty of Science, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo, 162-8601, Japan.
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The Chaperonin GroESL Facilitates Caulobacter crescentus Cell Division by Supporting the Functions of the Z-Ring Regulators FtsA and FzlA. mBio 2021; 12:mBio.03564-20. [PMID: 33947758 PMCID: PMC8262945 DOI: 10.1128/mbio.03564-20] [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] [Indexed: 12/17/2022] Open
Abstract
The highly conserved chaperonin GroESL performs a crucial role in protein folding; however, the essential cellular pathways that rely on this chaperone are underexplored. Loss of GroESL leads to severe septation defects in diverse bacteria, suggesting the folding function of GroESL may be integrated with the bacterial cell cycle at the point of cell division. Here, we describe new connections between GroESL and the bacterial cell cycle using the model organism Caulobacter crescentus. Using a proteomics approach, we identify candidate GroESL client proteins that become insoluble or are degraded specifically when GroESL folding is insufficient, revealing several essential proteins that participate in cell division and peptidoglycan biosynthesis. We demonstrate that other cell cycle events, such as DNA replication and chromosome segregation, are able to continue when GroESL folding is insufficient. We further find that deficiency of two FtsZ-interacting proteins, the bacterial actin homologue FtsA and the constriction regulator FzlA, mediate the GroESL-dependent block in cell division. Our data show that sufficient GroESL is required to maintain normal dynamics of the FtsZ scaffold and divisome functionality in C. crescentus. In addition to supporting divisome function, we show that GroESL is required to maintain the flow of peptidoglycan precursors into the growing cell wall. Linking a chaperone to cell division may be a conserved way to coordinate environmental and internal cues that signal when it is safe to divide.
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Schroeder K, Jonas K. The Protein Quality Control Network in Caulobacter crescentus. Front Mol Biosci 2021; 8:682967. [PMID: 33996917 PMCID: PMC8119881 DOI: 10.3389/fmolb.2021.682967] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2021] [Accepted: 04/08/2021] [Indexed: 11/13/2022] Open
Abstract
The asymmetric life cycle of Caulobacter crescentus has provided a model in which to study how protein quality control (PQC) networks interface with cell cycle and developmental processes, and how the functions of these systems change during exposure to stress. As in most bacteria, the PQC network of Caulobacter contains highly conserved ATP-dependent chaperones and proteases as well as more specialized holdases. During growth in optimal conditions, these systems support a regulated circuit of protein synthesis and degradation that drives cell differentiation and cell cycle progression. When stress conditions threaten the proteome, most components of the Caulobacter proteostasis network are upregulated and switch to survival functions that prevent, revert, and remove protein damage, while simultaneously pausing the cell cycle in order to regain protein homeostasis. The specialized physiology of Caulobacter influences how it copes with proteotoxic stress, such as in the global management of damaged proteins during recovery as well as in cell type-specific stress responses. Our mini-review highlights the discoveries that have been made in how Caulobacter utilizes its PQC network for regulating its life cycle under optimal and proteotoxic stress conditions, and discusses open research questions in this model.
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Affiliation(s)
- Kristen Schroeder
- Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
| | - Kristina Jonas
- Science for Life Laboratory, Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University, Stockholm, Sweden
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11
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Kang ZH, Liu YT, Gou Y, Deng QR, Hu ZY, Li GR. Progress and prospect of single-molecular ClpX ATPase researching system-a mini-review. Gene 2021; 774:145420. [PMID: 33434627 DOI: 10.1016/j.gene.2021.145420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2020] [Revised: 12/04/2020] [Accepted: 01/05/2021] [Indexed: 11/28/2022]
Abstract
ClpXP in Escherichia coli is a proteasome degrading protein substrates. It consists of one hexamer of ATPase (ClpX) and two heptamers of peptidase (ClpP). The ClpX binds ATP and translocates the substrate protein into the ClpP chamber by binding and hydrolysis of ATP. At single molecular level, ClpX harnesses cycles of power stroke (dwell and burst) to unfold the substrates, then releases the ADP and Pi. Based on the construction and function of ClpXP, especially the recent progress on how ClpX unfold protein substrates, in this mini-review, a currently proposed single ClpX molecular model system detected by optical tweezers, and its prospective for the elucidation of the mechanism of force generation of ClpX in its power stroke and the subunit interaction with each other, were discussed in detail.
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Affiliation(s)
- Zhen-Hui Kang
- School of Bioengineering, Sichuan University of Science & Engineering, Yibin 644005, Sichuan, China.
| | - Yi-Ting Liu
- School of Bioengineering, Sichuan University of Science & Engineering, Yibin 644005, Sichuan, China
| | - Yang Gou
- School of Bioengineering, Sichuan University of Science & Engineering, Yibin 644005, Sichuan, China
| | - Qi-Rui Deng
- School of Bioengineering, Sichuan University of Science & Engineering, Yibin 644005, Sichuan, China
| | - Zi-Yu Hu
- School of Bioengineering, Sichuan University of Science & Engineering, Yibin 644005, Sichuan, China
| | - Guan-Rong Li
- Southwest University, Beibei 400716, Chongqing, China.
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12
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Burgos R, Weber M, Martinez S, Lluch‐Senar M, Serrano L. Protein quality control and regulated proteolysis in the genome-reduced organism Mycoplasma pneumoniae. Mol Syst Biol 2020; 16:e9530. [PMID: 33320415 PMCID: PMC7737663 DOI: 10.15252/msb.20209530] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 11/04/2020] [Accepted: 11/08/2020] [Indexed: 12/14/2022] Open
Abstract
Protein degradation is a crucial cellular process in all-living systems. Here, using Mycoplasma pneumoniae as a model organism, we defined the minimal protein degradation machinery required to maintain proteome homeostasis. Then, we conditionally depleted the two essential ATP-dependent proteases. Whereas depletion of Lon results in increased protein aggregation and decreased heat tolerance, FtsH depletion induces cell membrane damage, suggesting a role in quality control of membrane proteins. An integrative comparative study combining shotgun proteomics and RNA-seq revealed 62 and 34 candidate substrates, respectively. Cellular localization of substrates and epistasis studies supports separate functions for Lon and FtsH. Protein half-life measurements also suggest a role for Lon-modulated protein decay. Lon plays a key role in protein quality control, degrading misfolded proteins and those not assembled into functional complexes. We propose that regulating complex assembly and degradation of isolated proteins is a mechanism that coordinates important cellular processes like cell division. Finally, by considering the entire set of proteases and chaperones, we provide a fully integrated view of how a minimal cell regulates protein folding and degradation.
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Affiliation(s)
- Raul Burgos
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
| | - Marc Weber
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
| | - Sira Martinez
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
| | - Maria Lluch‐Senar
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
| | - Luis Serrano
- Centre for Genomic Regulation (CRG)The Barcelona Institute of Science and TechnologyBarcelonaSpain
- Universitat Pompeu Fabra (UPF)BarcelonaSpain
- ICREABarcelonaSpain
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13
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Springstein BL, Weissenbach J, Koch R, Stücker F, Stucken K. The role of the cytoskeletal proteins MreB and FtsZ in multicellular cyanobacteria. FEBS Open Bio 2020; 10:2510-2531. [PMID: 33112491 PMCID: PMC7714070 DOI: 10.1002/2211-5463.13016] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 10/17/2020] [Accepted: 10/26/2020] [Indexed: 01/28/2023] Open
Abstract
Multiseriate and true‐branching cyanobacteria are at the peak of prokaryotic morphological complexity. However, little is known about the mechanisms governing multiplanar cell division and morphogenesis. Here, we study the function of the prokaryotic cytoskeletal proteins, MreB and FtsZ in Fischerella muscicola PCC 7414 and Chlorogloeopsis fritschii PCC 6912. Vancomycin and HADA labeling revealed a mixed apical, septal, and lateral trichome growth mode in F. muscicola, whereas C. fritschii exhibits septal growth. In all morphotypes from both species, MreB forms either linear filaments or filamentous strings and can interact with FtsZ. Furthermore, multiplanar cell division in F. muscicola likely depends on FtsZ dosage. Our results lay the groundwork for future studies on cytoskeletal proteins in morphologically complex cyanobacteria.
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Affiliation(s)
| | - Julia Weissenbach
- Institute of General Microbiology, Christian-Albrechts University of Kiel, Germany
| | - Robin Koch
- Institute of General Microbiology, Christian-Albrechts University of Kiel, Germany
| | - Fenna Stücker
- Institute of General Microbiology, Christian-Albrechts University of Kiel, Germany
| | - Karina Stucken
- Institute of General Microbiology, Christian-Albrechts University of Kiel, Germany
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14
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Sha Z, Fishovitz J, Wang S, Chilakala S, Xu Y, Lee I. A Selective Fluorogenic Peptide Substrate for the Human Mitochondrial ATP-Dependent Protease Complex ClpXP. Chembiochem 2020; 21:2037-2048. [PMID: 32180333 DOI: 10.1002/cbic.202000030] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Revised: 03/01/2020] [Indexed: 11/07/2022]
Abstract
The goal of this work is to identify differences in the substrate determinants of two human mitochondrial matrix ATP-dependent proteases, human ClpXP (hClpXP) and human Lon (hLon). This information allows the generation of protease-specific peptide substrates that can be used as chemical biology tools to investigate the physiological functions of hClpXP. These enzymes play a role in protein quality control, but currently the physiological functions of human ClpXP are not well defined. In this study, the degradation profile of casein, an alanine positional scanning decapeptide library, and a specific peptide sequence found in an endogenous substrate of bacterial ClpXP by hClpXP as well as hLon were examined. Based on our findings, we generated a specific fluorogenic peptide substrate, FR-Cleptide, for hClpXP with a kcat of 2.44±0.15 s-1 and Km =262±43 μM, respectively. The FR-Cleptide substrate was successfully used to identify a leucine methyl ketone as a potent lead inhibitor, and to detect endogenous hClpXP activity in HeLa cell lysate. We propose that the fluorogenic peptide substrate is a valuable tool for quantitatively monitoring the activity of hClpXP in cell lysate, as well as mechanistic characterization of hClpXP. The peptide-based chemical tools developed in this study will complement the substrates developed for human Lon in aiding the investigation of the physiological functions of the respective protease.
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Affiliation(s)
- Zhou Sha
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Jennifer Fishovitz
- Department of Chemistry and Physics, Saint Mary's College, Notre Dame, Indiana, 46556, USA
| | - Susan Wang
- Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, 44106, USA
| | - Sujatha Chilakala
- Department of Chemistry, Cleveland State University, Cleveland, Ohio, 44115, USA.,Lawrence J. Ellison Institute for Transformative Medicine of USC, University of Southern California, Beverly Hills, CA, 90211, USA
| | - Yan Xu
- Department of Chemistry, Cleveland State University, Cleveland, Ohio, 44115, USA
| | - Irene Lee
- Department of Chemistry, Case Western Reserve University, Cleveland, Ohio, 44106, USA
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15
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Staphylococcus aureus ClpX localizes at the division septum and impacts transcription of genes involved in cell division, T7-secretion, and SaPI5-excision. Sci Rep 2019; 9:16456. [PMID: 31712583 PMCID: PMC6848492 DOI: 10.1038/s41598-019-52823-0] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Accepted: 10/12/2019] [Indexed: 11/25/2022] Open
Abstract
In all living cells, molecular chaperones are essential for facilitating folding and unfolding of proteins. ClpX is a highly conserved ATP-dependent chaperone that besides functioning as a classical chaperone can associate with ClpP to form the ClpXP protease. To investigate the relative impact of the ClpXP protease and the ClpX chaperone in cell physiology of the important pathogenic bacterium Staphylococcus aureus, we assessed the transcriptional changes induced by inactivating only ClpXP, or by completely deleting ClpX. This analysis revealed that ClpX has a profound impact on S. aureus cell physiology that is mediated primarily via ClpXP-dependent pathways. As an example, ClpX impacts expression of virulence genes entirely via ClpXP-dependent mechanisms. Furthermore, ClpX controls a high number of genes and sRNAs via pathways involving both ClpXP protease and ClpX chaperone activities; an interesting example being genes promoting excision and replication of the pathogenicity island SaPI5. Independently of ClpP, ClpX, impacts transcription of only a restricted number of genes involved in peptidoglycan synthesis, cell division, and type seven secretion. Finally, we demonstrate that ClpX localizes in single foci in close proximity to the division septum lending support to the idea that ClpX plays a role in S. aureus cell division.
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16
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Männik J, Walker BE, Männik J. Cell cycle-dependent regulation of FtsZ in Escherichia coli in slow growth conditions. Mol Microbiol 2018; 110:1030-1044. [PMID: 30230648 DOI: 10.1111/mmi.14135] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/17/2018] [Indexed: 01/15/2023]
Abstract
FtsZ is the key regulator of bacterial cell division. It initiates division by forming a dynamic ring-like structure, the Z-ring, at the mid-cell. What triggers the formation of the Z-ring during the cell cycle is poorly understood. In Escherichia coli, the common view is that FtsZ concentration is constant throughout its doubling time and therefore regulation of assembly is controlled by some yet-to-be-identified protein-protein interactions. Using a newly developed functional, fluorescent FtsZ reporter, we performed a quantitative analysis of the FtsZ concentration throughout the cell cycle under slow growth conditions. In contrast to the common expectation, we show that FtsZ concentrations vary in a cell cycle-dependent manner, and that upregulation of FtsZ synthesis correlates with the formation of the Z-ring. The first half of the cell cycle shows an approximately fourfold upregulation of FtsZ synthesis, followed by its rapid degradation by ClpXP protease in the last 10% of the cell cycle. The initiation of rapid degradation coincides with the dissociation of FtsZ from the septum. Altogether, our data suggest that the Z-ring formation in slow growth conditions in E. coli is partially controlled by a regulatory sequence wherein upregulation of an essential cell cycle factor is followed by its degradation.
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Affiliation(s)
- Jaana Männik
- Department of Biochemistry & Cellular and Molecular Biology, University of Tennessee, Knoxville, TN, 37996, USA
| | - Bryant E Walker
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA
| | - Jaan Männik
- Department of Physics and Astronomy, University of Tennessee, Knoxville, TN, 37996, USA
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17
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Polar Localization Hub Protein PopZ Restrains Adaptor-Dependent ClpXP Proteolysis in Caulobacter crescentus. J Bacteriol 2018; 200:JB.00221-18. [PMID: 30082457 DOI: 10.1128/jb.00221-18] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2018] [Accepted: 07/27/2018] [Indexed: 01/20/2023] Open
Abstract
In Caulobacter crescentus, timely degradation of several proteins by the ClpXP protease is critical for proper cell cycle progression. During the cell cycle, the ClpXP protease, the substrate CtrA, and many other proteins are localized to the stalked pole dependent on a polar interaction hub composed of PopZ protein oligomers. Prior work suggests that the localization of ClpXP, protease substrates, and cofactors is needed for recognition of substrates, such as CtrA, by ClpXP. Here, we formally test this hypothesis by examining the role of PopZ in ClpXP activity and find, surprisingly, that CtrA degradation is enhanced in cells lacking polar localization due to loss of PopZ. The ClpXP adaptor CpdR is required for this enhanced degradation of CtrA and other adaptor-dependent substrates, but adaptor-independent substrate degradation is not affected upon loss of PopZ. We find that overexpression of PopZ also leads to faster degradation of CtrA but is likely due to nonphysiologically relevant recognition of CtrA by ClpXP alone, as loss of CpdR does not affect this enhancement. Our main conclusion is that loss of PopZ, and therefore loss of polar localization, does not result in the loss of ClpXP-regulated proteolysis, as would be predicted from a model which requires polar localization of ClpXP for its activation. Rather, our data point to a model where PopZ normally restrains ClpXP proteolysis by promoting the inactivation of the CpdR adaptor, perhaps through the activity and localization of the CckA kinase.IMPORTANCE Regulated proteolysis is critical for the cell cycle progression of bacteria, such as Caulobacter crescentus According to one model, this regulated proteolysis requires localization of the ClpXP protease at the stalked pole for its subsequent degradation of substrates, such as CtrA. This study offers evidence that supports an alternative model to explain how localization might influence protein degradation. Using a delocalized in vivo system created by the deletion of a polar organizing protein, PopZ, we show that activation of the ClpXP protease is independent of its polar localization. The data point to a role for PopZ in restraining ClpXP activity, likely by controlling the activity of upstream regulators of protease activity, such as CckA, though changes in its localization.
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18
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Abstract
Regulated proteolysis is a vital process that affects all living things. Bacteria use energy-dependent AAA+ proteases to power degradation of misfolded and native regulatory proteins. Given that proteolysis is an irreversible event, specificity and selectivity in degrading substrates are key. Specificity is often augmented through the use of adaptors that modify the inherent specificity of the proteolytic machinery. Regulated protein degradation is intricately linked to quality control, cell-cycle progression, and physiological transitions. In this review, we highlight recent work that has shed light on our understanding of regulated proteolysis in bacteria. We discuss the role AAA+ proteases play during balanced growth as well as how these proteases are deployed during changes in growth. We present examples of how protease selectivity can be controlled in increasingly complex ways. Finally, we describe how coupling a core recognition determinant to one or more modifying agents is a general theme for regulated protein degradation.
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Affiliation(s)
- Samar A Mahmoud
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA; ,
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA; ,
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19
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Collier J. Cell division control in Caulobacter crescentus. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1862:685-690. [PMID: 29715525 DOI: 10.1016/j.bbagrm.2018.04.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Revised: 04/26/2018] [Accepted: 04/26/2018] [Indexed: 12/31/2022]
Abstract
Caulobacter crescentus is a free-living Alphaproteobacterium that thrives in oligotrophic environments. This review focuses on the regulatory network used by this bacterium to control the levels of cell division proteins, their organization inside the cell and their activity as a function of the cell cycle. Strikingly, C. crescentus makes frequent use of master transcriptional regulators and epigenetic signals, most likely to synchronize cell division with other events of the cell cycle. In addition, cellular metabolism and DNA damage sensors emerge as central players regulating cell division in response to changing environmental conditions.
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Affiliation(s)
- Justine Collier
- Department of Fundamental Microbiology, Faculty of Biology and Medicine, University of Lausanne, Quartier UNIL/Sorge, Lausanne, CH 1015, Switzerland.
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20
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Flores SA, Howell M, Daniel JJ, Piccolo R, Brown PJB. Absence of the Min System Does Not Cause Major Cell Division Defects in Agrobacterium tumefaciens. Front Microbiol 2018; 9:681. [PMID: 29686659 PMCID: PMC5900048 DOI: 10.3389/fmicb.2018.00681] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2018] [Accepted: 03/22/2018] [Indexed: 12/19/2022] Open
Abstract
In A. tumefaciens, the essential FtsZ protein is located at the growth pole before shifting to the mid-cell right before division. Loss of FtsZ causes a halt in cell separation and lysis of cells. To understand how FtsZ polymerization is regulated to properly localize the FtsZ ring at the mid-cell, we have conducted a systematic characterization of the Min system in A. tumefaciens. Our findings indicate that the Min system is not required for cell survival. Yet, we find that the deletion of either minE or minCDE results in a broad cell size distribution, including an increase in the proportion of short and long cells. We observe that the site of constriction is misplaced in the minE or minCDE deletion strains allowing for short cells to arise from sites of constriction near the cell poles. Remarkably, the short cells are viable and contain DNA. In order to observe chromosome replication and segregation in these strains, YFP-ParB is used as a proxy to track the origin of replication as cells elongate and divide. In the absence of the Min proteins, duplication and segregation of the origin of replication is frequently delayed. Taken together, our data suggest that the Min system contributes to the proper regulation of FtsZ placement and subsequent cell division. Furthermore, the failure to precisely place FtsZ rings at mid-cell in the min mutants impacts other cell cycle features including chromosome segregation.
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Affiliation(s)
- Sue A Flores
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - Matthew Howell
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - Jeremy J Daniel
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - Rebecca Piccolo
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
| | - Pamela J B Brown
- Division of Biological Sciences, University of Missouri, Columbia, MO, United States
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21
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Reduction in adaptor amounts establishes degradation hierarchy among protease substrates. Proc Natl Acad Sci U S A 2018; 115:E4483-E4492. [PMID: 29686082 DOI: 10.1073/pnas.1722246115] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
ATP-dependent proteases control critical cellular processes, including development, physiology, and virulence. A given protease may recognize a substrate directly via an unfoldase domain or subunit or indirectly via an adaptor that delivers the substrate to the unfoldase. We now report that cells achieve differential stability among substrates of a given protease by modulating adaptor amounts. We establish that the regulatory protein PhoP represses transcription of the gene specifying the ClpAP protease adaptor ClpS when the bacteria Salmonella enterica and Escherichia coli experience low cytoplasmic Mg2+ The resulting decrease in ClpS amounts diminishes proteolysis of several ClpSAP-dependent substrates, including the putrescine aminotransferase Oat, which heightens the formation of antibiotic persisters, and the transcriptional regulators UvrY and PhoP, which alter the expression of genes controlled by these proteins. By contrast, the decrease in ClpS amounts did not impact the abundance of the ClpSAP substrate FtsA, reflecting that FtsA binds to ClpS more tightly than to UvrY and PhoP. Our findings show how physiological conditions that reduce adaptor amounts modify the abundance of selected substrates of a given protease.
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22
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Yeom J, Wayne KJ, Groisman EA. Sequestration from Protease Adaptor Confers Differential Stability to Protease Substrate. Mol Cell 2017; 66:234-246.e5. [PMID: 28431231 DOI: 10.1016/j.molcel.2017.03.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2016] [Revised: 02/23/2017] [Accepted: 03/14/2017] [Indexed: 12/24/2022]
Abstract
According to the N-end rule, the N-terminal residue of a protein determines its stability. In bacteria, the adaptor ClpS mediates proteolysis by delivering substrates bearing specific N-terminal residues to the protease ClpAP. We now report that the Salmonella adaptor ClpS binds to the N terminus of the regulatory protein PhoP, resulting in PhoP degradation by ClpAP. We establish that the PhoP-activated protein MgtC protects PhoP from degradation by outcompeting ClpS for binding to PhoP. MgtC appears to act exclusively on PhoP, as it did not alter the stability of a different ClpS-dependent ClpAP substrate. Removal of five N-terminal residues rendered PhoP stability independent of both the clpS and mgtC genes. By preserving PhoP protein levels, MgtC enables normal temporal transcription of PhoP-activated genes. The identified mechanism provides a simple means to spare specific substrates from an adaptor-dependent protease.
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Affiliation(s)
- Jinki Yeom
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
| | - Kyle J Wayne
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
| | - Eduardo A Groisman
- Department of Microbial Pathogenesis, Yale School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA; Yale Microbial Sciences Institute, P.O. Box 27389, West Haven, CT 06516, USA.
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23
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Vass RH, Nascembeni J, Chien P. The Essential Role of ClpXP in Caulobacter crescentus Requires Species Constrained Substrate Specificity. Front Mol Biosci 2017; 4:28. [PMID: 28536693 PMCID: PMC5422525 DOI: 10.3389/fmolb.2017.00028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 04/19/2017] [Indexed: 12/05/2022] Open
Abstract
The ClpXP protease is a highly conserved AAA+ degradation machine that is present throughout bacteria and in eukaryotic organelles. ClpXP is essential in some bacteria, such as Caulobacter crescentus, but dispensible in others, such as Escherichia coli. In Caulobacter, ClpXP normally degrades the SocB toxin and increased levels of SocB result in cell death. ClpX can be deleted in cells lacking this toxin, but these ΔclpX strains are still profoundly deficient in morphology and growth supporting the existence of additional important functions for ClpXP. In this work, we characterize aspects of ClpX crucial for its cellular function. Specifically, we show that although the E. coli ClpX functions with the Caulobacter ClpP in vitro, this variant cannot complement wildtype activity in vivo. Chimeric studies suggest that the N-terminal domain of ClpX plays a crucial, species-specific role in maintaining normal growth. We find that one defect of Caulobacter lacking the proper species of ClpX is the failure to properly proteolytically process the replication clamp loader subunit DnaX. Consistent with this, growth of ΔclpX cells is improved upon expression of a shortened form of DnaX in trans. This work reveals that a broadly conserved protease can acquire highly specific functions in different species and further reinforces the critical nature of the N-domain of ClpX in substrate choice.
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Affiliation(s)
- Robert H Vass
- Molecular and Cellular Biology Graduate Program, University of MassachusettsAmherst, MA, USA
| | - Jacob Nascembeni
- Department of Biochemistry and Molecular Biology, University of MassachusettsAmherst, MA, USA
| | - Peter Chien
- Molecular and Cellular Biology Graduate Program, University of MassachusettsAmherst, MA, USA.,Department of Biochemistry and Molecular Biology, University of MassachusettsAmherst, MA, USA
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24
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Woldemeskel SA, Goley ED. Shapeshifting to Survive: Shape Determination and Regulation in Caulobacter crescentus. Trends Microbiol 2017; 25:673-687. [PMID: 28359631 DOI: 10.1016/j.tim.2017.03.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Revised: 02/28/2017] [Accepted: 03/06/2017] [Indexed: 01/05/2023]
Abstract
Bacterial cell shape is a genetically encoded and inherited feature that is optimized for efficient growth, survival, and propagation of bacteria. In addition, bacterial cell morphology is adaptable to changes in environmental conditions. Work in recent years has demonstrated that individual features of cell shape, such as length or curvature, arise through the spatial regulation of cell wall synthesis by cytoskeletal proteins. However, the mechanisms by which these different morphogenetic factors are coordinated and how they may be globally regulated in response to cell cycle and environmental cues are only beginning to emerge. Here, we have summarized recent advances that have been made to understand morphology in the dimorphic Gram-negative bacterium Caulobacter crescentus.
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Affiliation(s)
- Selamawit Abi Woldemeskel
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA
| | - Erin D Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
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25
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Abstract
Signaling hubs at bacterial cell poles establish cell polarity in the absence of membrane-bound compartments. In the asymmetrically dividing bacterium Caulobacter crescentus, cell polarity stems from the cell cycle-regulated localization and turnover of signaling protein complexes in these hubs, and yet the mechanisms that establish the identity of the two cell poles have not been established. Here, we recapitulate the tripartite assembly of a cell fate signaling complex that forms during the G1-S transition. Using in vivo and in vitro analyses of dynamic polar protein complex formation, we show that a polymeric cell polarity protein, SpmX, serves as a direct bridge between the PopZ polymeric network and the cell fate-directing DivJ histidine kinase. We demonstrate the direct binding between these three proteins and show that a polar microdomain spontaneously assembles when the three proteins are coexpressed heterologously in an Escherichia coli test system. The relative copy numbers of these proteins are essential for complex formation, as overexpression of SpmX in Caulobacter reorganizes the polarity of the cell, generating ectopic cell poles containing PopZ and DivJ. Hierarchical formation of higher-order SpmX oligomers nucleates new PopZ microdomain assemblies at the incipient lateral cell poles, driving localized outgrowth. By comparison to self-assembling protein networks and polar cell growth mechanisms in other bacterial species, we suggest that the cooligomeric PopZ-SpmX protein complex in Caulobacter illustrates a paradigm for coupling cell cycle progression to the controlled geometry of cell pole establishment.IMPORTANCE Lacking internal membrane-bound compartments, bacteria achieve subcellular organization by establishing self-assembling protein-based microdomains. The asymmetrically dividing bacterium Caulobacter crescentus uses one such microdomain to link cell cycle progression to morphogenesis, but the mechanism for the generation of this microdomain has remained unclear. Here, we demonstrate that the ordered assembly of this microdomain occurs via the polymeric network protein PopZ directly recruiting the polarity factor SpmX, which then recruits the histidine kinase DivJ to the developing cell pole. Further, we find that overexpression of the bridge protein SpmX in Caulobacter disrupts this ordered assembly, generating ectopic cell poles containing both PopZ and DivJ. Together, PopZ and SpmX assemble into a cooligomeric network that forms the basis for a polar microdomain that coordinates bacterial cell polarity.
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26
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Caulobacter crescentus CdnL is a non-essential RNA polymerase-binding protein whose depletion impairs normal growth and rRNA transcription. Sci Rep 2017; 7:43240. [PMID: 28233804 PMCID: PMC5324124 DOI: 10.1038/srep43240] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Accepted: 01/23/2017] [Indexed: 12/22/2022] Open
Abstract
CdnL is an essential RNA polymerase (RNAP)-binding activator of rRNA transcription in mycobacteria and myxobacteria but reportedly not in Bacillus. Whether its function and mode of action are conserved in other bacteria thus remains unclear. Because virtually all alphaproteobacteria have a CdnL homolog and none of these have been characterized, we studied the homolog (CdnLCc) of the model alphaproteobacterium Caulobacter crescentus. We show that CdnLCc is not essential for viability but that its absence or depletion causes slow growth and cell filamentation. CdnLCc is degraded in vivo in a manner dependent on its C-terminus, yet excess CdnLCc resulting from its stabilization did not adversely affect growth. We find that CdnLCc interacts with itself and with the RNAP β subunit, and localizes to at least one rRNA promoter in vivo, whose activity diminishes upon depletion of CdnLCc. Interestingly, cells expressing CdnLCc mutants unable to interact with the RNAP were cold-sensitive, suggesting that CdnLCc interaction with RNAP is especially required at lower than standard growth temperatures in C. crescentus. Our study indicates that despite limited sequence similarities and regulatory differences compared to its myco/myxobacterial homologs, CdnLCc may share similar biological functions, since it affects rRNA synthesis, probably by stabilizing open promoter-RNAP complexes.
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27
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Viola MG, LaBreck CJ, Conti J, Camberg JL. Proteolysis-Dependent Remodeling of the Tubulin Homolog FtsZ at the Division Septum in Escherichia coli. PLoS One 2017; 12:e0170505. [PMID: 28114338 PMCID: PMC5256927 DOI: 10.1371/journal.pone.0170505] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 01/05/2017] [Indexed: 11/18/2022] Open
Abstract
During bacterial cell division a dynamic protein structure called the Z-ring assembles at the septum. The major protein in the Z-ring in Escherichia coli is FtsZ, a tubulin homolog that polymerizes with GTP. FtsZ is degraded by the two-component ATP-dependent protease ClpXP. Two regions of FtsZ, located outside of the polymerization domain in the unstructured linker and at the C-terminus, are important for specific recognition and degradation by ClpXP. We engineered a synthetic substrate containing green fluorescent protein (Gfp) fused to an extended FtsZ C-terminal tail (residues 317–383), including the unstructured linker and the C-terminal conserved region, but not the polymerization domain, and showed that it is sufficient to target a non-native substrate for degradation in vitro. To determine if FtsZ degradation regulates Z-ring assembly during division, we expressed a full length Gfp-FtsZ fusion protein in wild type and clp deficient strains and monitored fluorescent Z-rings. In cells deleted for clpX or clpP, or cells expressing protease-defective mutant protein ClpP(S97A), Z-rings appear normal; however, after photobleaching a region of the Z-ring, fluorescence recovers ~70% more slowly in cells without functional ClpXP than in wild type cells. Gfp-FtsZ(R379E), which is defective for degradation by ClpXP, also assembles into Z-rings that recover fluorescence ~2-fold more slowly than Z-rings containing Gfp-FtsZ. In vitro, ClpXP cooperatively degrades and disassembles FtsZ polymers. These results demonstrate that ClpXP is a regulator of Z-ring dynamics and that the regulation is proteolysis-dependent. Our results further show that FtsZ-interacting proteins in E. coli fine-tune Z-ring dynamics.
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Affiliation(s)
- Marissa G. Viola
- Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Christopher J. LaBreck
- Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Joseph Conti
- Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, United States of America
| | - Jodi L. Camberg
- Department of Cell and Molecular Biology, The University of Rhode Island, Kingston, Rhode Island, United States of America
- * E-mail:
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28
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Cytoskeletal Proteins in Caulobacter crescentus: Spatial Orchestrators of Cell Cycle Progression, Development, and Cell Shape. Subcell Biochem 2017; 84:103-137. [PMID: 28500524 DOI: 10.1007/978-3-319-53047-5_4] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Caulobacter crescentus, an aquatic Gram-negative α-proteobacterium, is dimorphic, as a result of asymmetric cell divisions that give rise to a free-swimming swarmer daughter cell and a stationary stalked daughter. Cell polarity of vibrioid C. crescentus cells is marked by the presence of a stalk at one end in the stationary form and a polar flagellum in the motile form. Progression through the cell cycle and execution of the associated morphogenetic events are tightly controlled through regulation of the abundance and activity of key proteins. In synergy with the regulation of protein abundance or activity, cytoskeletal elements are key contributors to cell cycle progression through spatial regulation of developmental processes. These include: polarity establishment and maintenance, DNA segregation, cytokinesis, and cell elongation. Cytoskeletal proteins in C. crescentus are additionally required to maintain its rod shape, curvature, and pole morphology. In this chapter, we explore the mechanisms through which cytoskeletal proteins in C. crescentus orchestrate developmental processes by acting as scaffolds for protein recruitment, generating force, and/or restricting or directing the motion of molecular machines. We discuss each cytoskeletal element in turn, beginning with those important for organization of molecules at the cell poles and chromosome segregation, then cytokinesis, and finally cell shape.
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29
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Liu J, Francis LI, Jonas K, Laub MT, Chien P. ClpAP is an auxiliary protease for DnaA degradation in Caulobacter crescentus. Mol Microbiol 2016; 102:1075-1085. [PMID: 27667502 DOI: 10.1111/mmi.13537] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/20/2016] [Indexed: 11/28/2022]
Abstract
The Clp family of proteases is responsible for controlling both stress responses and normal growth. In Caulobacter crescentus, the ClpXP protease is essential and drives cell cycle progression through adaptor-mediated degradation. By contrast, the physiological role for the ClpAP protease is less well understood with only minor growth defects previously reported for ΔclpA cells. Here, we show that ClpAP plays an important role in controlling chromosome content and cell fitness during extended growth. Cells lacking ClpA accumulate aberrant numbers of chromosomes upon prolonged growth suggesting a defect in replication control. Levels of the replication initiator DnaA are elevated in ΔclpA cells and degradation of DnaA is more rapid in cells lacking the ClpA inhibitor ClpS. Consistent with this observation, ClpAP degrades DnaA in vitro while ClpS inhibits this degradation. In cells lacking Lon, the protease previously shown to degrade DnaA in Caulobacter, ClpA overexpression rescues defects in fitness and restores degradation of DnaA. Finally, we show that cells lacking ClpA are particularly sensitive to inappropriate increases in DnaA activity. Our work demonstrates an unexpected effect of ClpAP in directly regulating replication through degradation of DnaA and expands the functional role of ClpAP in Caulobacter.
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Affiliation(s)
- Jing Liu
- Molecular and Cellular Biology Graduate Program, Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Laura I Francis
- Department of Biology, University of Massachusetts Amherst, Amherst, MA, USA
| | - Kristina Jonas
- Howard Hughes Medical Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Michael T Laub
- Howard Hughes Medical Institute and Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Peter Chien
- Molecular and Cellular Biology Graduate Program, Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, MA, USA
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30
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Abstract
Protein degradation is essential for all living things. Bacteria use energy-dependent proteases to control protein destruction in a highly specific manner. Recognition of substrates is determined by the inherent specificity of the proteases and through adaptor proteins that alter the spectrum of substrates. In the α-proteobacterium Caulobacter crescentus, regulated protein degradation is required for stress responses, developmental transitions, and cell cycle progression. In this review, we describe recent progress in our understanding of the regulated and stress-responsive protein degradation pathways in Caulobacter. We discuss how organization of highly specific adaptors into functional hierarchies drives destruction of proteins during the bacterial cell cycle. Because all cells must balance the need for degradation of many true substrates with the toxic consequences of nonspecific protein destruction, principles found in one system likely generalize to others.
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Affiliation(s)
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts 01003;
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31
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An intracellular compass spatially coordinates cell cycle modules in Caulobacter crescentus. Curr Opin Microbiol 2016; 33:131-139. [PMID: 27517351 DOI: 10.1016/j.mib.2016.06.007] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2016] [Accepted: 06/24/2016] [Indexed: 12/27/2022]
Abstract
Cellular functions in Bacteria, such as chromosome segregation and cytokinesis, result from cascades of molecular events operating largely as self-contained modules. Regulated timing of these cellular modules stems from global genetic circuits that allow precise temporal activation with respect to cell cycle progression and cell differentiation. Critically, many of these functions occur at defined locations within the cell, and therefore regulators of each module must communicate to remain coordinated in space. In this perspective, we highlight recent discoveries in Caulobacter crescentus asymmetric cell division to illuminate diverse mechanisms by which a cellular compass, composed of scaffolding and signaling proteins, directs cell cycle modules to their exact cellular addresses.
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32
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Busiek KK, Margolin W. Bacterial actin and tubulin homologs in cell growth and division. Curr Biol 2016; 25:R243-R254. [PMID: 25784047 DOI: 10.1016/j.cub.2015.01.030] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
In contrast to the elaborate cytoskeletal machines harbored by eukaryotic cells, such as mitotic spindles, cytoskeletal structures detectable by typical negative stain electron microscopy are generally absent from bacterial cells. As a result, for decades it was thought that bacteria lacked cytoskeletal machines. Revolutions in genomics and fluorescence microscopy have confirmed the existence not only of smaller-scale cytoskeletal structures in bacteria, but also of widespread functional homologs of eukaryotic cytoskeletal proteins. The presence of actin, tubulin, and intermediate filament homologs in these relatively simple cells suggests that primitive cytoskeletons first arose in bacteria. In bacteria such as Escherichia coli, homologs of tubulin and actin directly interact with each other and are crucial for coordinating cell growth and division. The function and direct interactions between these proteins will be the focus of this review.
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Affiliation(s)
- Kimberly K Busiek
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin St., Houston, TX 77030, USA
| | - William Margolin
- Department of Microbiology and Molecular Genetics, University of Texas Medical School at Houston, 6431 Fannin St., Houston, TX 77030, USA.
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33
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Haeusser DP, Margolin W. Splitsville: structural and functional insights into the dynamic bacterial Z ring. Nat Rev Microbiol 2016; 14:305-19. [PMID: 27040757 DOI: 10.1038/nrmicro.2016.26] [Citation(s) in RCA: 216] [Impact Index Per Article: 27.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Bacteria must divide to increase in number and colonize their niche. Binary fission is the most widespread means of bacterial cell division, but even this relatively simple mechanism has many variations on a theme. In most bacteria, the tubulin homologue FtsZ assembles into a ring structure, termed the Z ring, at the site of cytokinesis and recruits additional proteins to form a large protein machine - the divisome - that spans the membrane. In this Review, we discuss current insights into the regulation of the assembly of the Z ring and how the divisome drives membrane invagination and septal cell wall growth while flexibly responding to various cellular inputs.
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Affiliation(s)
- Daniel P Haeusser
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin Street, Houston, Texas 77030, USA.,Biology Department, Canisius College, 2001 Main Street, Buffalo, New York 14208, USA
| | - William Margolin
- Department of Microbiology and Molecular Genetics, McGovern Medical School, 6431 Fannin Street, Houston, Texas 77030, USA
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34
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Buczek MS, Cardenas Arevalo AL, Janakiraman A. ClpXP and ClpAP control the Escherichia coli division protein ZapC by proteolysis. MICROBIOLOGY-SGM 2016; 162:909-920. [PMID: 26978224 DOI: 10.1099/mic.0.000278] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The bacterial FtsZ-ring is an essential cytokinetic structure under tight spatiotemporal regulation. In Escherichia coli, FtsZ polymerization and assembly into the Z-ring is controlled on multiple levels through interactions with positive and negative regulators. Among these regulatory factors are ZapC, a Z-ring stabilizer, and the conserved protease ClpXP, which has been shown to degrade FtsZ protofilaments in preference to FtsZ monomers. Here we report that ZapC and ClpX interact in a protein-protein interaction assay, and that ZapC is degraded in a ClpXP-dependent manner in vivo. The SspB adaptor protein is not required for targeting ZapC to the ClpXP proteolytic machinery. A mutation disrupting the zapC ssrA-like sequence (zapCDD) stabilizes ZapC consistent with a reduction in ClpXP-mediated ZapC degradation. ZapCDD retains the ability to interact with FtsZ and to promote bundling in vitro indicating that WT ZapC contains discrete FtsZ and ClpX recognition motifs. Additionally, ClpAP complexes are sufficient for degradation of ZapC in the absence of ClpX in vivo. Further, chromosomal expression of zapCDD suppresses filamentation of the temperature-sensitive ftsZ84 mutant, confirming the role of ZapC as a Z-ring stabilizer. Lastly, changes in ClpXP and ZapC levels lead to cell division effects, likely through their roles in modulating FtsZ assembly dynamics. Taken together, our results indicate that the Z-ring stabilizer ZapC is a substrate of both ClpXP and ClpAP in vivo. Our data also point to a more complex regulatory circuit that integrates FtsZ, ClpXP and ZapC in achieving Z-ring stability in E. coli and related species.
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Affiliation(s)
- Monika S Buczek
- Department of Biology, MR 526, The City College of CUNY, New York, NY 10031, USA.,The Graduate Center of CUNY, New York, NY 10016, USA
| | | | - Anuradha Janakiraman
- The Graduate Center of CUNY, New York, NY 10016, USA.,Department of Biology, MR 526, The City College of CUNY, New York, NY 10031, USA
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35
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Cell cycle control in Alphaproteobacteria. Curr Opin Microbiol 2016; 30:107-113. [PMID: 26871482 DOI: 10.1016/j.mib.2016.01.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 01/19/2016] [Accepted: 01/21/2016] [Indexed: 11/22/2022]
Abstract
Alphaproteobacteria include many medically and environmentally important organisms. Despite the diversity of their niches and lifestyles, from free-living to host-associated, they usually rely on very similar mechanisms to control their cell cycles. Studies on Caulobacter crescentus still lay the foundation for understanding the molecular details of pathways regulating DNA replication and cell division and coordinating these two processes with other events of the cell cycle. This review highlights recent discoveries on the regulation and the mode of action of conserved global regulators and small molecules like c-di-GMP and (p)ppGpp, which play key roles in cell cycle control. It also describes several newly identified mechanisms that modulate cell cycle progression in response to stresses or environmental conditions.
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36
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The Caulobacter crescentus Homolog of DnaA (HdaA) Also Regulates the Proteolysis of the Replication Initiator Protein DnaA. J Bacteriol 2015; 197:3521-32. [PMID: 26324449 DOI: 10.1128/jb.00460-15] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 08/21/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED It is not known how diverse bacteria regulate chromosome replication. Based on Escherichia coli studies, DnaA initiates replication and the homolog of DnaA (Hda) inactivates DnaA using the RIDA (regulatory inactivation of DnaA) mechanism that thereby prevents extra chromosome replication cycles. RIDA may be widespread, because the distantly related Caulobacter crescentus homolog HdaA also prevents extra chromosome replication (J. Collier and L. Shapiro, J Bacteriol 191:5706-5715, 2009, http://dx.doi.org/10.1128/JB.00525-09). To further study the HdaA/RIDA mechanism, we created a C. crescentus strain that shuts off hdaA transcription and rapidly clears HdaA protein. We confirm that HdaA prevents extra replication, since cells lacking HdaA accumulate extra chromosome DNA. DnaA binds nucleotides ATP and ADP, and our results are consistent with the established E. coli mechanism whereby Hda converts active DnaA-ATP to inactive DnaA-ADP. However, unlike E. coli DnaA, C. crescentus DnaA is also regulated by selective proteolysis. C. crescentus cells lacking HdaA reduce DnaA proteolysis in logarithmically growing cells, thereby implicating HdaA in this selective DnaA turnover mechanism. Also, wild-type C. crescentus cells remove all DnaA protein when they enter stationary phase. However, cells lacking HdaA retain stable DnaA protein even when they stop growing in nutrient-depleted medium that induces complete DnaA proteolysis in wild-type cells. Additional experiments argue for a distinct HdaA-dependent mechanism that selectively removes DnaA prior to stationary phase. Related freshwater Caulobacter species also remove DnaA during entry to stationary phase, implying a wider role for HdaA as a novel component of programed proteolysis. IMPORTANCE Bacteria must regulate chromosome replication, and yet the mechanisms are not completely understood and not fully exploited for antibiotic development. Based on Escherichia coli studies, DnaA initiates replication, and the homolog of DnaA (Hda) inactivates DnaA to prevent extra replication. The distantly related Caulobacter crescentus homolog HdaA also regulates chromosome replication. Here we unexpectedly discovered that unlike the E. coli Hda, the C. crescentus HdaA also regulates DnaA proteolysis. Furthermore, this HdaA proteolysis acts in logarithmically growing and in stationary-phase cells and therefore in two very different physiological states. We argue that HdaA acts to help time chromosome replications in logarithmically growing cells and that it is an unexpected component of the programed entry into stationary phase.
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37
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Narayanan S, Janakiraman B, Kumar L, Radhakrishnan SK. A cell cycle-controlled redox switch regulates the topoisomerase IV activity. Genes Dev 2015; 29:1175-87. [PMID: 26063575 PMCID: PMC4470285 DOI: 10.1101/gad.257030.114] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Narayanan et al. show in C. crescentus that NstA acts by binding to the ParC DNA-binding subunit of topoisomerase IV and inhibits its decatenation activity. They also uncover a dynamic oscillation of the intracellular redox state during the cell cycle, which correlates with and controls NstA activity. Topoisomerase IV (topo IV), an essential factor during chromosome segregation, resolves the catenated chromosomes at the end of each replication cycle. How the decatenating activity of the topo IV is regulated during the early stages of the chromosome cycle despite being in continuous association with the chromosome remains poorly understood. Here we report a novel cell cycle-regulated protein in Caulobacter crescentus, NstA (negative switch for topo IV decatenation activity), that inhibits the decatenation activity of the topo IV during early stages of the cell cycle. We demonstrate that in C. crescentus, NstA acts by binding to the ParC DNA-binding subunit of topo IV. Most importantly, we uncover a dynamic oscillation of the intracellular redox state during the cell cycle, which correlates with and controls NstA activity. Thus, we propose that predetermined dynamic intracellular redox fluctuations may act as a global regulatory switch to control cellular development and cell cycle progression and may help retain pathogens in a suitable cell cycle state when encountering redox stress from the host immune response.
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Affiliation(s)
- Sharath Narayanan
- School of Biology, Indian Institute of Science Education and Research, Thiruvananthapuram 695016, Kerala, India
| | - Balaganesh Janakiraman
- School of Biology, Indian Institute of Science Education and Research, Thiruvananthapuram 695016, Kerala, India
| | - Lokesh Kumar
- School of Biology, Indian Institute of Science Education and Research, Thiruvananthapuram 695016, Kerala, India
| | - Sunish Kumar Radhakrishnan
- School of Biology, Indian Institute of Science Education and Research, Thiruvananthapuram 695016, Kerala, India
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38
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Sundararajan K, Miguel A, Desmarais SM, Meier EL, Casey Huang K, Goley ED. The bacterial tubulin FtsZ requires its intrinsically disordered linker to direct robust cell wall construction. Nat Commun 2015; 6:7281. [PMID: 26099469 PMCID: PMC4532373 DOI: 10.1038/ncomms8281] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 04/26/2015] [Indexed: 12/17/2022] Open
Abstract
The bacterial GTPase FtsZ forms a cytokinetic ring at midcell, recruits the division machinery, and orchestrates membrane and peptidoglycan cell wall invagination. However, the mechanism for FtsZ regulation of peptidoglycan metabolism is unknown. The FtsZ GTPase domain is separated from its membrane-anchoring C-terminal conserved (CTC) peptide by a disordered C-terminal linker (CTL). Here, we investigate CTL function in Caulobacter crescentus. Strikingly, production of FtsZ lacking the CTL (ΔCTL) is lethal: cells become filamentous, form envelope bulges, and lyse, resembling treatment with β-lactam antibiotics. This phenotype is produced by FtsZ polymers bearing the CTC and a CTL shorter than 14 residues. Peptidoglycan synthesis still occurs downstream of ΔCTL, however cells expressing ΔCTL exhibit reduced peptidoglycan crosslinking and longer glycan strands than wildtype. Importantly, midcell proteins are still recruited to sites of ΔCTL assembly. We propose that FtsZ regulates peptidoglycan metabolism through a CTL-dependent mechanism that extends beyond simple protein recruitment.
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Affiliation(s)
- Kousik Sundararajan
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Amanda Miguel
- Department of Bioengineering, Stanford University, Stanford, California 94305, USA
| | - Samantha M Desmarais
- Department of Bioengineering, Stanford University, Stanford, California 94305, USA
| | - Elizabeth L Meier
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Kerwyn Casey Huang
- 1] Department of Bioengineering, Stanford University, Stanford, California 94305, USA [2] Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Erin D Goley
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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39
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Schrader JM, Shapiro L. Synchronization of Caulobacter crescentus for investigation of the bacterial cell cycle. J Vis Exp 2015:52633. [PMID: 25938623 PMCID: PMC4541484 DOI: 10.3791/52633] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
The cell cycle is important for growth, genome replication, and development in all cells. In bacteria, studies of the cell cycle have focused largely on unsynchronized cells making it difficult to order the temporal events required for cell cycle progression, genome replication, and division. Caulobacter crescentus provides an excellent model system for the bacterial cell cycle whereby cells can be rapidly synchronized in a G0 state by density centrifugation. Cell cycle synchronization experiments have been used to establish the molecular events governing chromosome replication and segregation, to map a genetic regulatory network controlling cell cycle progression, and to identify the establishment of polar signaling complexes required for asymmetric cell division. Here we provide a detailed protocol for the rapid synchronization of Caulobacter NA1000 cells. Synchronization can be performed in a large-scale format for gene expression profiling and western blot assays, as well as a small-scale format for microscopy or FACS assays. The rapid synchronizability and high cell yields of Caulobacter make this organism a powerful model system for studies of the bacterial cell cycle.
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Affiliation(s)
- Jared M Schrader
- Department of Developmental Biology, Stanford University School of Medicine;
| | - Lucy Shapiro
- Department of Developmental Biology, Stanford University School of Medicine
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40
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Intergenerational continuity of cell shape dynamics in Caulobacter crescentus. Sci Rep 2015; 5:9155. [PMID: 25778096 PMCID: PMC4894450 DOI: 10.1038/srep09155] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2014] [Accepted: 02/11/2015] [Indexed: 01/15/2023] Open
Abstract
We investigate the intergenerational shape dynamics of single Caulobacter crescentus cells using a novel combination of imaging techniques and theoretical modeling. We determine the dynamics of cell pole-to-pole lengths, cross-sectional widths, and medial curvatures from high accuracy measurements of cell contours. Moreover, these shape parameters are determined for over 250 cells across approximately 10000 total generations, which affords high statistical precision. Our data and model show that constriction is initiated early in the cell cycle and that its dynamics are controlled by the time scale of exponential longitudinal growth. Based on our extensive and detailed growth and contour data, we develop a minimal mechanical model that quantitatively accounts for the cell shape dynamics and suggests that the asymmetric location of the division plane reflects the distinct mechanical properties of the stalked and swarmer poles. Furthermore, we find that the asymmetry in the division plane location is inherited from the previous generation. We interpret these results in terms of the current molecular understanding of shape, growth, and division of C. crescentus.
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41
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Heinrich K, Leslie DJ, Jonas K. Modulation of bacterial proliferation as a survival strategy. ADVANCES IN APPLIED MICROBIOLOGY 2015; 92:127-71. [PMID: 26003935 DOI: 10.1016/bs.aambs.2015.02.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The cell cycle is one of the most fundamental processes in biology, underlying the proliferation and growth of all living organisms. In bacteria, the cell cycle has been extensively studied since the 1950s. Most of this research has focused on cell cycle regulation in a few model bacteria, cultured under standard growth conditions. However in nature, bacteria are exposed to drastic environmental changes. Recent work shows that by modulating their own growth and proliferation bacteria can increase their survival under stressful conditions, including antibiotic treatment. Here, we review the mechanisms that allow bacteria to integrate environmental information into their cell cycle. In particular, we focus on mechanisms controlling DNA replication and cell division. We conclude this chapter by highlighting the importance of understanding bacterial cell cycle and growth control for future research as well as other disciplines.
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42
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Schrader JM, Zhou B, Li GW, Lasker K, Childers WS, Williams B, Long T, Crosson S, McAdams HH, Weissman JS, Shapiro L. The coding and noncoding architecture of the Caulobacter crescentus genome. PLoS Genet 2014; 10:e1004463. [PMID: 25078267 PMCID: PMC4117421 DOI: 10.1371/journal.pgen.1004463] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2014] [Accepted: 05/13/2014] [Indexed: 11/24/2022] Open
Abstract
Caulobacter crescentus undergoes an asymmetric cell division controlled by a genetic circuit that cycles in space and time. We provide a universal strategy for defining the coding potential of bacterial genomes by applying ribosome profiling, RNA-seq, global 5′-RACE, and liquid chromatography coupled with tandem mass spectrometry (LC-MS) data to the 4-megabase C. crescentus genome. We mapped transcript units at single base-pair resolution using RNA-seq together with global 5′-RACE. Additionally, using ribosome profiling and LC-MS, we mapped translation start sites and coding regions with near complete coverage. We found most start codons lacked corresponding Shine-Dalgarno sites although ribosomes were observed to pause at internal Shine-Dalgarno sites within the coding DNA sequence (CDS). These data suggest a more prevalent use of the Shine-Dalgarno sequence for ribosome pausing rather than translation initiation in C. crescentus. Overall 19% of the transcribed and translated genomic elements were newly identified or significantly improved by this approach, providing a valuable genomic resource to elucidate the complete C. crescentus genetic circuitry that controls asymmetric cell division. Caulobacter crescentus is a model system for studying asymmetric cell division, a fundamental process that, through differential gene expression in the two daughter cells, enables the generation of cells with different fates. To explore how the genome directs and maintains asymmetry upon cell division, we performed a coordinated analysis of multiple genomic and proteomic datasets to identify the RNA and protein coding features in the C. crescentus genome. Our integrated analysis identifies many new genetic regulatory elements, adding significant regulatory complexity to the C. crescentus genome. Surprisingly, 75.4% of protein coding genes lack a canonical translation initiation sequence motif (the Shine-Dalgarno site) which hybridizes to the 3′ end of the ribosomal RNA allowing translation initiation. We find Shine-Dalgarno sites primarily inside of genes where they cause translating ribosomes to pause, possibly allowing nascent proteins to correctly fold. With our detailed map of genomic transcription and translation elements, a systems view of the genetic network that controls asymmetric cell division is within reach.
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Affiliation(s)
- Jared M. Schrader
- Department of Developmental Biology, Stanford University, Stanford, California, United States of America
| | - Bo Zhou
- Department of Developmental Biology, Stanford University, Stanford, California, United States of America
| | - Gene-Wei Li
- Department of Cellular and Molecular Pharmacology, California Institute of Quantitative Biology, Center for RNA Systems Biology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, California, United States of America
| | - Keren Lasker
- Department of Developmental Biology, Stanford University, Stanford, California, United States of America
| | - W. Seth Childers
- Department of Developmental Biology, Stanford University, Stanford, California, United States of America
| | - Brandon Williams
- Department of Developmental Biology, Stanford University, Stanford, California, United States of America
| | - Tao Long
- Department of Developmental Biology, Stanford University, Stanford, California, United States of America
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois, United States of America
| | - Harley H. McAdams
- Department of Developmental Biology, Stanford University, Stanford, California, United States of America
| | - Jonathan S. Weissman
- Department of Cellular and Molecular Pharmacology, California Institute of Quantitative Biology, Center for RNA Systems Biology, Howard Hughes Medical Institute, University of California, San Francisco, San Francisco, California, United States of America
| | - Lucy Shapiro
- Department of Developmental Biology, Stanford University, Stanford, California, United States of America
- * E-mail:
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