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Sun J, Qian P, Kang Y, Dai HB, Wang FZ, Wang HY, Zhou H, Gao Q, Zhou YB. Adrenomedullin 2 attenuates LPS-induced inflammation in microglia cells by receptor-mediated cAMP-PKA pathway. Neuropeptides 2021; 85:102109. [PMID: 33253929 DOI: 10.1016/j.npep.2020.102109] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 11/15/2020] [Accepted: 11/15/2020] [Indexed: 12/18/2022]
Abstract
Inflammation plays a critical role in the development of neurodegenerative diseases. Adrenomedullin 2 (AM2), a member of the calcitonin gene-related peptide family, has been known to have anti-inflammatory effects. Here, we evaluated the anti-inflammatory effects of AM2 in LPS-activated microglia and BV2 cells. The endogenous mRNA and protein expressions of AM2, calcitonin receptor-like receptor (CLR), receptor activity-modifying proteins (RAMPs) including RAMP1, RAMP2 and RAMP3 and the production of inflammatory mediators including tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) were detected by RT-PCR and Western blot. Our results revealed that LPS (1 μg/mL) significantly stimulated CLR, RAMP1, RAMP2 and RAMP3 protein expressions in BV2 microglia cells, but AM2 had a significant decrease. However, the mRNA levels of AM2, CLR, and RAMP1/2/3 were all markedly increased. LPS also induced obvious increases in mRNA and protein levels of the inflammatory mediators (TNF-α, IL-1β, COX2 and iNOS). More importantly, AM2 (10 nM) administration effectively inhibited the mRNA and protein expressions of these mediators induced by LPS and increased the cAMP content in LPS-stimulated BV2 cells. Furthermore, the antagonism with AM2 receptor antagonist IMD17-47, adrenomedullin (AM) receptor antagonist by AM22-52 or the inhibition of protein kinase A (PKA) activation by P1195 effectively prevented the inhibitory role of AM2 in LPS-induced production of the above inflammatory mediators. In conclusion, AM2 inhibits LPS-induced inflammation in BV2 microglia cells that may be mainly through AM receptor-mediated cAMP-PKA pathway. Our results indicate AM2 plays an important protective role in microglia inflammation, suggesting therapeutic potential for AM2 in neuroinflammation diseases caused by activated microglia.
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Affiliation(s)
- Jing Sun
- Department of Physiology, Nanjing Medical University, Nanjing 211166, China
| | - Pei Qian
- Department of Physiology, Nanjing Medical University, Nanjing 211166, China
| | - Ying Kang
- Department of Physiology, Nanjing Medical University, Nanjing 211166, China
| | - Hang-Bing Dai
- Department of Physiology, Nanjing Medical University, Nanjing 211166, China
| | - Fang-Zheng Wang
- Department of Physiology, Nanjing Medical University, Nanjing 211166, China
| | - Hong-Yu Wang
- Department of Physiology, Nanjing Medical University, Nanjing 211166, China
| | - Hong Zhou
- Department of Physiology, Nanjing Medical University, Nanjing 211166, China
| | - Qing Gao
- Department of Physiology, Nanjing Medical University, Nanjing 211166, China
| | - Ye-Bo Zhou
- Department of Physiology, Nanjing Medical University, Nanjing 211166, China.
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Rebollo-Ramirez S, Larrouy-Maumus G. NaCl triggers the CRP-dependent increase of cAMP in Mycobacterium tuberculosis. Tuberculosis (Edinb) 2019; 116:8-16. [PMID: 31153521 DOI: 10.1016/j.tube.2019.03.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2019] [Revised: 03/19/2019] [Accepted: 03/26/2019] [Indexed: 11/19/2022]
Abstract
The second messenger 3',5'-cyclic adenosine monophosphate (3',5'-cAMP) has been shown to be involved in the regulation of many biological processes ranging from carbon catabolite repression in bacteria to cell signalling in eukaryotes. In mycobacteria, the role of cAMP and the mechanisms utilized by the bacterium to adapt to and resist immune and pharmacological sterilization remain poorly understood. Among the stresses encountered by bacteria, ionic and non-ionic osmotic stresses are among the best studied. However, in mycobacteria, the link between ionic osmotic stress, particularly sodium chloride, and cAMP has been relatively unexplored. Using a targeted metabolic analysis combined with stable isotope tracing, we show that the pathogenic Mycobacterium tuberculosis but not the opportunistic pathogen Mycobacterium marinum nor the non-pathogenic Mycobacterium smegmatis responds to NaCl stress via an increase in intracellular cAMP levels. We further showed that this increase in cAMP is dependent on the cAMP receptor protein and in part on the threonine/serine kinase PnkD, which has previously been associated with the NaCl stress response in mycobacteria.
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Affiliation(s)
- Sonia Rebollo-Ramirez
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, UK
| | - Gerald Larrouy-Maumus
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, UK.
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Robichaux WG, Cheng X. Intracellular cAMP Sensor EPAC: Physiology, Pathophysiology, and Therapeutics Development. Physiol Rev 2018; 98:919-1053. [PMID: 29537337 PMCID: PMC6050347 DOI: 10.1152/physrev.00025.2017] [Citation(s) in RCA: 131] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 09/05/2017] [Accepted: 09/06/2017] [Indexed: 12/13/2022] Open
Abstract
This review focuses on one family of the known cAMP receptors, the exchange proteins directly activated by cAMP (EPACs), also known as the cAMP-regulated guanine nucleotide exchange factors (cAMP-GEFs). Although EPAC proteins are fairly new additions to the growing list of cAMP effectors, and relatively "young" in the cAMP discovery timeline, the significance of an EPAC presence in different cell systems is extraordinary. The study of EPACs has considerably expanded the diversity and adaptive nature of cAMP signaling associated with numerous physiological and pathophysiological responses. This review comprehensively covers EPAC protein functions at the molecular, cellular, physiological, and pathophysiological levels; and in turn, the applications of employing EPAC-based biosensors as detection tools for dissecting cAMP signaling and the implications for targeting EPAC proteins for therapeutic development are also discussed.
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Affiliation(s)
- William G Robichaux
- Department of Integrative Biology and Pharmacology, Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center , Houston, Texas
| | - Xiaodong Cheng
- Department of Integrative Biology and Pharmacology, Texas Therapeutics Institute, The Brown Foundation Institute of Molecular Medicine, The University of Texas Health Science Center , Houston, Texas
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4
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Haycocks JRJ, Grainger DC. Unusually Situated Binding Sites for Bacterial Transcription Factors Can Have Hidden Functionality. PLoS One 2016; 11:e0157016. [PMID: 27258043 PMCID: PMC4892627 DOI: 10.1371/journal.pone.0157016] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 05/23/2016] [Indexed: 01/13/2023] Open
Abstract
A commonly accepted paradigm of molecular biology is that transcription factors control gene expression by binding sites at the 5' end of a gene. However, there is growing evidence that transcription factor targets can occur within genes or between convergent genes. In this work, we have investigated one such target for the cyclic AMP receptor protein (CRP) of enterotoxigenic Escherichia coli. We show that CRP binds between two convergent genes. When bound, CRP regulates transcription of a small open reading frame, which we term aatS, embedded within one of the adjacent genes. Our work demonstrates that non-canonical sites of transcription factor binding can have hidden functionality.
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Affiliation(s)
- James R. J. Haycocks
- Institute of Microbiology and Infection, School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - David C. Grainger
- Institute of Microbiology and Infection, School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- * E-mail:
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Bai J, Zhu X, Wang Q, Zhang J, Chen H, Dong G, Zhu L, Zheng H, Xie Q, Nian J, Chen F, Fu Y, Qian Q, Zuo J. Rice TUTOU1 Encodes a Suppressor of cAMP Receptor-Like Protein That Is Important for Actin Organization and Panicle Development. Plant Physiol 2015; 169:1179-91. [PMID: 26243616 PMCID: PMC4587440 DOI: 10.1104/pp.15.00229] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 07/27/2015] [Indexed: 05/12/2023]
Abstract
Panicle development, a key event in rice (Oryza sativa) reproduction and a critical determinant of grain yield, forms a branched structure containing multiple spikelets. Genetic and environmental factors can perturb panicle development, causing panicles to degenerate and producing characteristic whitish, small spikelets with severely reduced fertility and yield; however, little is known about the molecular basis of the formation of degenerating panicles in rice. Here, we report the identification and characterization of the rice panicle degenerative mutant tutou1 (tut1), which shows severe defects in panicle development. The tut1 also shows a pleiotropic phenotype, characterized by short roots, reduced plant height, and abnormal development of anthers and pollen grains. Molecular genetic studies revealed that TUT1 encodes a suppressor of cAMP receptor/Wiskott-Aldrich syndrome protein family verprolin-homologous (SCAR/WAVE)-like protein. We found that TUT1 contains conserved functional domains found in eukaryotic SCAR/WAVE proteins, and was able to activate Actin-related protein2/3 to promote actin nucleation and polymerization in vitro. Consistently, tut1 mutants show defects in the arrangement of actin filaments in trichome. These results indicate that TUT1 is a functional SCAR/WAVE protein and plays an important role in panicle development.
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Affiliation(s)
- Jiaoteng Bai
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Xudong Zhu
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Qing Wang
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Jian Zhang
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Hongqi Chen
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Guojun Dong
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Lei Zhu
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Huakun Zheng
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Qingjun Xie
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Jinqiang Nian
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Fan Chen
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Ying Fu
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Qian Qian
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
| | - Jianru Zuo
- State Key Laboratory of Plant Genomics and National Plant Gene Research Center (J.B., Q.W., J.Zh., H.Z., Q.X., J.N., J.Zu.) and State Key Laboratory of Molecular Developmental Biology and National Plant Gene Research Center (F.C.), Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing 100101, China;University of Chinese Academy of Sciences, Beijing 100049, China (J.B., Q.W., H.Z., Q.X.);State Key Laboratory of Rice Biology, China National Rice Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310006, China (X.Z., H.C., G.D., Q.Q.); andState Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China (L.Z., Y.F.)
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Gonzales L, Ali ZB, Nygren E, Wang Z, Karlsson S, Zhu B, Quiding-Järbrink M, Sjöling Å. Alkaline pH Is a signal for optimal production and secretion of the heat labile toxin, LT in enterotoxigenic Escherichia coli (ETEC). PLoS One 2013; 8:e74069. [PMID: 24058516 PMCID: PMC3776858 DOI: 10.1371/journal.pone.0074069] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2013] [Accepted: 07/26/2013] [Indexed: 01/12/2023] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) cause secretory diarrhea in children and travelers to endemic areas. ETEC spreads through the fecal-oral route. After ingestion, ETEC passes through the stomach and duodenum before it colonizes the lower part of the small intestine, exposing bacteria to a wide range of pH and environmental conditions. This study aimed to determine the impact of external pH and activity of the Cyclic AMP receptor protein (CRP) on the regulation of production and secretion of heat labile (LT) enterotoxin. ETEC strain E2863wt and its isogenic mutant E2863ΔCRP were grown in LBK media buffered to pH 5, 7 and 9. GM1 ELISA, cDNA and cAMP analyses were carried out on bacterial pellet and supernatant samples derived from 3 and 5 hours growth and from overnight cultures. We confirm that CRP is a repressor of LT transcription and production as has been shown before but we show for the first time that CRP is a positive regulator of LT secretion both in vitro and in vivo. LT secretion increased at neutral to alkaline pH compared to acidic pH 5 where secretion was completely inhibited. At pH 9 secretion of LT was optimal resulting in 600 percent increase of secreted LT compared to unbuffered LBK media. This effect was not due to membrane leakage since the bacteria were viable at pH 9. The results indicate that the transition to the alkaline duodenum and/or exposure to high pH close to the epithelium as well as activation of the global transcription factor CRP are signals that induce secretion of the LT toxin in ETEC.
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Affiliation(s)
- Lucia Gonzales
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
- Instituto de Biología Molecular y Biotecnología, Universidad Mayor de San Andrés, La Paz, Bolivia
| | - Zahra Bagher Ali
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Erik Nygren
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Zhiyun Wang
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, PR China
| | - Stefan Karlsson
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Baoli Zhu
- CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, PR China
| | - Marianne Quiding-Järbrink
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
| | - Åsa Sjöling
- Department of Microbiology and Immunology, Institute of Biomedicine, University of Gothenburg, Gothenburg, Sweden
- * E-mail:
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Abstract
The surface behaviour of swimming amoebae was followed in cells bearing a cAR1-paGFP (cyclic AMP receptor fused to a photoactivatable-GFP) construct. Sensitized amoebae were placed in a buoyant medium where they could swim toward a chemoattractant cAMP source. paGFP, activated at the cell's front, remained fairly stationary in the cell's frame as the cell advanced; the label was not swept rearwards. Similar experiments with chemotaxing cells attached to a substratum gave the same result. Furthermore, if the region around a lateral projection near a crawling cell's front is marked, the projection and the labelled cAR1 behave differently. The label spreads by diffusion but otherwise remains stationary in the cell's frame; the lateral projection moves rearwards on the cell (remaining stationary with respect to the substrate), so that it ends up outside the labelled region. Furthermore, as cAR1-GFP cells move, they occasionally do so in a remarkably straight line; this suggests they do not need to snake to move on a substratum. Previously, we suggested that the surface membrane of a moving amoeba flows from front to rear as part of a polarised membrane trafficking cycle. This could explain how swimming amoebae are able to exert a force against the medium. Our present results indicate that, in amoebae, the suggested surface flow does not exist: this implies that they swim by shape changes.
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Affiliation(s)
- Jonathan D. Howe
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Nicholas P. Barry
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
| | - Mark S. Bretscher
- Cell Biology Division, Medical Research Council Laboratory of Molecular Biology, Cambridge, Cambridgeshire, United Kingdom
- * E-mail:
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8
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Kalivoda EJ, Brothers KM, Stella NA, Schmitt MJ, Shanks RMQ. Bacterial cyclic AMP-phosphodiesterase activity coordinates biofilm formation. PLoS One 2013; 8:e71267. [PMID: 23923059 PMCID: PMC3726613 DOI: 10.1371/journal.pone.0071267] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Accepted: 06/27/2013] [Indexed: 12/26/2022] Open
Abstract
Biofilm-related infections are a major contributor to human disease, and the capacity for surface attachment and biofilm formation are key attributes for the pathogenesis of microbes. Serratia marcescens type I fimbriae-dependent biofilms are coordinated by the adenylate cyclase, CyaA, and the cyclic 3′,5′-adenosine monophosphate (cAMP)-cAMP receptor protein (CRP) complex. This study uses S. marcescens as a model system to test the role of cAMP-phosphodiesterase activity in controlling biofilm formation. Herein we describe the characterization of a putative S. marcescens cAMP-phosphodiesterase gene (SMA3506), designated as cpdS, and demonstrated to be a functional cAMP-phosphodiesterase both in vitro and in vivo. Deletion of cpdS resulted in defective biofilm formation and reduced type I fimbriae production, whereas multicopy expression of cpdS conferred a type I fimbriae-dependent hyper-biofilm. Together, these results support a model in which bacterial cAMP-phosphodiesterase activity modulates biofilm formation.
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Affiliation(s)
- Eric J. Kalivoda
- Charles T. Campbell Laboratory of Ophthalmic Microbiology, Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, Unites States of America
| | - Kimberly M. Brothers
- Charles T. Campbell Laboratory of Ophthalmic Microbiology, Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, Unites States of America
| | - Nicholas A. Stella
- Charles T. Campbell Laboratory of Ophthalmic Microbiology, Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, Unites States of America
| | - Matthew J. Schmitt
- Charles T. Campbell Laboratory of Ophthalmic Microbiology, Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, Unites States of America
| | - Robert M. Q. Shanks
- Charles T. Campbell Laboratory of Ophthalmic Microbiology, Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, Unites States of America
- * E-mail:
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He YL, Liu DD, Fang YJ, Zhan XQ, Yao JJ, Mei YA. Exposure to extremely low-frequency electromagnetic fields modulates Na+ currents in rat cerebellar granule cells through increase of AA/PGE2 and EP receptor-mediated cAMP/PKA pathway. PLoS One 2013; 8:e54376. [PMID: 23349866 PMCID: PMC3551899 DOI: 10.1371/journal.pone.0054376] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2012] [Accepted: 12/11/2012] [Indexed: 12/19/2022] Open
Abstract
Although the modulation of Ca2+ channel activity by extremely low-frequency electromagnetic fields (ELF-EMF) has been studied previously, few reports have addressed the effects of such fields on the activity of voltage-activated Na+ channels (Nav). Here, we investigated the effects of ELF-EMF on Nav activity in rat cerebellar granule cells (GCs). Our results reveal that exposing cerebellar GCs to ELF-EMF for 10–60 min significantly increased Nav currents (INa) by 30–125% in a time- and intensity-dependent manner. The Nav channel steady-state activation curve, but not the steady-state inactivation curve, was significantly shifted (by 5.2 mV) towards hyperpolarization by ELF-EMF stimulation. This phenomenon is similar to the effect of intracellular application of arachidonic acid (AA) and prostaglandin E2 (PGE2) on INa in cerebellar GCs. Increases in intracellular AA, PGE2 and phosphorylated PKA levels in cerebellar GCs were observed following ELF-EMF exposure. Western blottings indicated that the NaV 1.2 protein on the cerebellar GCs membrane was increased, the total expression levels of NaV 1.2 protein were not affected after exposure to ELF-EMF. Cyclooxygenase inhibitors and PGE2 receptor (EP) antagonists were able to eliminate this ELF-EMF-induced increase in phosphorylated PKA and INa. In addition, ELF-EMF exposure significantly enhanced the activity of PLA2 in cerebellar GCs but did not affect COX-1 or COX-2 activity. Together, these data demonstrate for the first time that neuronal INa is significantly increased by ELF-EMF exposure via a cPLA2 AA PGE2 EP receptors PKA signaling pathway.
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Affiliation(s)
- Yan-Lin He
- Institutes of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
| | - Dong-Dong Liu
- Institutes of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
| | - Yan-Jia Fang
- Institutes of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
| | - Xiao-Qin Zhan
- Institutes of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
| | - Jin-Jing Yao
- Institutes of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
| | - Yan-Ai Mei
- Institutes of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
- * E-mail:
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10
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Abstract
UNLABELLED In a previous study of promoters dependent on the Escherichia coli cyclic AMP receptor protein (CRP), carrying tandem DNA sites for CRP, we found that the upstream-bound CRP could either enhance or repress transcription, depending on its location. Here, we have analyzed the interactions between CRP and the C-terminal domains of the RNA polymerase α subunits at some of these promoters. We report that the upstream-bound CRP interacts with these domains irrespective of whether it up- or downregulates promoter activity. Hence, disruption of this interaction can lead to either down- or upregulation, depending on its location. IMPORTANCE Many bacterial promoters carry multiple DNA sites for transcription factors. While most factors that downregulate promoter activity bind to targets that overlap or are downstream of the transcription start and -10 element, very few cases of repression from upstream locations have been reported. Since more Escherichia coli promoters are regulated by cyclic AMP receptor protein (CRP) than by any other transcription factor, and since multiple DNA sites for CRP are commonplace at promoters, our results suggest that promoter downregulation by transcription factors may be more prevalent than hitherto thought, and this will have implications for the annotation of promoters from new bacterial genome sequences.
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Affiliation(s)
- David J Lee
- Institute of Microbiology and Infection, University of Birmingham, Birmingham, United Kingdom
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11
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Tsalkova T, Mei FC, Cheng X. A fluorescence-based high-throughput assay for the discovery of exchange protein directly activated by cyclic AMP (EPAC) antagonists. PLoS One 2012; 7:e30441. [PMID: 22276201 PMCID: PMC3262007 DOI: 10.1371/journal.pone.0030441] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 12/21/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The discovery, more than ten years ago, of exchange proteins directly activated by cAMP (EPAC) as a new family of intracellular cAMP receptors revolutionized the cAMP signaling research field. Extensive studies have revealed that the cAMP signaling network is much more complex and dynamic as many cAMP-related cellular processes, previously thought to be controlled by protein kinase A, are found to be also mediated by EPAC proteins. Although there have been many important discoveries in the roles of EPACs greater understanding of their physiological function in cAMP-mediated signaling is impeded by the absence of EPAC-specific antagonist. METHODOLOGY/PRINCIPAL FINDINGS To overcome this deficit, we have developed a fluorescence-based high throughput assay for screening EPAC specific antagonists. Our assay is highly reproducible and simple to perform using the "mix and measure" format. A pilot screening using the NCI-DTP diversity set library led to the identification of small chemical compounds capable of specifically inhibiting cAMP-induced EPAC activation while not affecting PKA activity. CONCLUSIONS/SIGNIFICANCE Our study establishes a robust high throughput screening assay that can be effectively applied for the discovery of EPAC-specific antagonists, which may provide valuable pharmacological tools for elucidating the biological functions of EPAC and for promoting an understanding of disease mechanisms related to EPAC/cAMP signaling.
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Affiliation(s)
- Tamara Tsalkova
- Department of Pharmacology and Toxicology and Sealy Center for Structural Biology and Molecular Biophysics, The University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Fang C. Mei
- Department of Pharmacology and Toxicology and Sealy Center for Structural Biology and Molecular Biophysics, The University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Xiaodong Cheng
- Department of Pharmacology and Toxicology and Sealy Center for Structural Biology and Molecular Biophysics, The University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail:
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12
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Cha I, Lee SH, Jeon TJ. Chemoattractant-mediated Rap1 activation requires GPCR/G proteins. Mol Cells 2010; 30:563-7. [PMID: 21103944 DOI: 10.1007/s10059-010-0153-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 09/08/2010] [Accepted: 09/10/2010] [Indexed: 10/18/2022] Open
Abstract
Rap1 is rapidly activated upon chemoattractant stimulation and plays an important role in cell adhesion and cytoskeletal reorganization during chemotaxis. Here, we demonstrate that G-protein coupled receptors and G-proteins are essential for chemoattractant-mediated Rap1 activation in Dictyostelium. The rapid Rap1 activation upon cAMP chemoattractant stimulation was absent in cells lacking chemoattractant cAMP receptors cAR1/cAR3 or a subunit of the heterotrimeric G-protein complex Gα2. Loss of guanylyl cyclases GCA/SGC or a cGMP-binding protein GbpC exhibited no effect on Rap1 activation kinetics. These results suggest that Rap1, a key regulator for the regulation of cytoskeletal reorganization during cell movement, is activated through the G-protein coupled receptors cAR1/cAR3 and Gα2 proteins in a way independent of the cGMP signaling pathway.
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Affiliation(s)
- Injun Cha
- Department of Biology, College of Natural Sciences, Chosun University, Gwangju 501-759, Korea
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13
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Hollands K, Lee DJ, Lloyd GS, Busby SJW. Activation of sigma 28-dependent transcription in Escherichia coli by the cyclic AMP receptor protein requires an unusual promoter organization. Mol Microbiol 2010; 75:1098-111. [PMID: 19843224 PMCID: PMC2859248 DOI: 10.1111/j.1365-2958.2009.06913.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/30/2009] [Indexed: 11/27/2022]
Abstract
The Escherichia coli aer regulatory region contains a single promoter that is recognized by RNA polymerase containing the flagellar sigma factor, sigma(28). Expression from this promoter is dependent on direct activation by the cyclic AMP receptor protein, which binds to a target centred 49.5 base pairs upstream from the transcript start. Activator-dependent transcription from the aer promoter was reconstituted in vitro, and a tethered inorganic nuclease was used to find the position of the C-terminal domains of the RNA polymerase alpha subunits in transcriptionally competent open complexes. We report that the ternary activator--RNA polymerase--aer promoter open complex is organized differently from complexes at previously characterized promoters. Among other E. coli promoters recognized by RNA polymerase containing sigma(28), only the trg promoter is activated directly by the cyclic AMP receptor protein. The organization of the different promoter elements and the activator binding site at the trg promoter is the same as at the aer promoter, suggesting a common activation mechanism.
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Affiliation(s)
- Kerry Hollands
- School of Biosciences, University of BirminghamEdgbaston, Birmingham, UK
| | - David J Lee
- School of Biosciences, University of BirminghamEdgbaston, Birmingham, UK
| | - Georgina S Lloyd
- School of Biosciences, University of BirminghamEdgbaston, Birmingham, UK
| | - Stephen J W Busby
- School of Biosciences, University of BirminghamEdgbaston, Birmingham, UK
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14
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Shpakov AO, Derkach KV, Uspenskaia ZI, Pertseva MN. [Regulation by cyclic adenosine monophosphate of functional activity of the adenylyl cyclase system of the infusorian Dileptus anser]. Zh Evol Biokhim Fiziol 2010; 46:119-125. [PMID: 20432705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
In some unicellular eukaryotes, cAMP performs functions not only of the second messenger, but also of hormone, the primary messenger. We have found that cAMP binds to surface receptors of the free-living infusorian Dileptus anser and stimulates activity of the adenylyl cyclase signaling system (AC-system) including heterotrimeric G-proteins and enzyme adenylyl cyclase (AC). The binding of cAMP to receptor is performed with a high affinity (K(D), 27 nM) and is highly specific, as cGMP and adenosine do not produce a marked effect on it. The infusorian cAMP-receptors have been shown to be coupled to G-proteins, which is indicated by a decrease of their affinity to the ligand in the presence of GTP, stimulation of the GTP-binding of G-proteins with the cyclic nucleotide, and block of the cAMP regulatory effects with suramin, an inhibitor of heterotrimeric G-proteins. cAMP stimulates dose-dependently the AC activity, its effect remaining virtually unchanged in the presence of cGMP, AMP, GMP, and adenosine. N6,O2-dibutyryl-cAMP, a non-hydrolyzed cAMP analog, only at comparatively high concentrations competes with cAMP for binding sites and decreases the cAMP stimulating effects on the AC activity and GTP binding. Thus, we have shown for the first time that the AC system of the infusorians D. anser is stimulated with the extracellular cAMP that in this case functions as the external signal regulates activity of extracellular cAMP-dependent effector systems.
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15
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Miyanaga Y, Matsuoka S, Ueda M. Single-molecule imaging techniques to visualize chemotactic signaling events on the membrane of living Dictyostelium cells. Methods Mol Biol 2009; 571:417-435. [PMID: 19763983 DOI: 10.1007/978-1-60761-198-1_28] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
In this chapter, we describe methods to monitor signaling events at the single-molecule level on the membrane of living cells by using total internal reflection fluorescence microscopy (TIRFM). The techniques provide a powerful tool for elucidating the stochastic properties of signaling molecules involved in chemotaxis of the cellular slime mold Dictyostelium discoideum. Taking cAMP receptor 1 (cAR1) as an example of a target protein for single-molecule imaging, we describe the experimental setup of TIRFM, a method for labeling cAR1 with a fluorescent dye, and a method for investigating the receptor's lateral mobility. We discuss how the developmental progression of cells modulates both cAR1 behavior and the phenotypic variability in cAR1 mobility for different cell populations.
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Affiliation(s)
- Yukihiro Miyanaga
- Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, Osaka, Japan
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16
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Bonarek P, Kedracka-Krok S, Kepys B, Wasylewski Z. Quantitative analysis of the ternary complex of RNA polymerase, cyclic AMP receptor protein and DNA by fluorescence anisotropy measurements. Acta Biochim Pol 2008; 55:537-547. [PMID: 18787713] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2008] [Revised: 08/29/2008] [Accepted: 09/08/2008] [Indexed: 05/26/2023]
Abstract
The in vitro formation of transcription complexes with Escherichia coli RNA polymerase was monitored using fluorescence anisotropy measurements of labeled fragments of DNA. The multicomponent system consisted of holo or core RNA polymerase (RNAP) and lac or gal promoter fragments of DNA (in different configurations), in the presence or absence of CRP activator protein (wt or mutants) with its ligand, cAMP. Values of the apparent binding constants characterizing the system were obtained, as a result of all processes taking place in the system. The interaction of the promoters with core RNAP in the absence of CRP protein was characterized by apparent binding constants of 0.67 and 1.9 x 10(6) M(-1) for lac166 and gal178, respectively, and could be regarded as nonspecific. The presence of wt CRP enhanced the strength of the interaction of core RNAP with the promoter, and even in the case of gal promoter it made this interaction specific (apparent binding constant 2.93 x 10(7) M(-1)). Holo RNAP bound the promoters significantly more strongly than core RNAP did (apparent binding constants 1.46 and 40.14 x 10(6) M(-1) for lac166 and gal178, respectively), and the presence of CRP also enhanced the strength of these interactions. The mutation in activator region 1 of CRP did not cause any significant disturbances in the holo RNAP-lac promoter interaction, but mutation in activator region 2 of the activator protein substantially weakened the RNAP-gal promoter interaction.
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Affiliation(s)
- Piotr Bonarek
- Department of Physical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland.
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17
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Abstract
cAMP-mediated signaling pathways regulate a multitude of important biological processes under both physiological and pathological conditions, including diabetes, heart failure and cancer. In eukaryotic cells, the effects of cAMP are mediated by two ubiquitously expressed intracellular cAMP receptors, the classic protein kinase A (PKA)/cAMP-dependent protein kinase and the recently discovered exchange protein directly activated by camp (Epac)/cAMP-regulated guanine nucleotide exchange factors. Like PKA, Epac contains an evolutionally conserved cAMP binding domain that acts as a molecular switch for sensing intracellular second messenger cAMP levels to control diverse biological functions. The existence of two families of cAMP effectors provides a mechanism for a more precise and integrated control of the cAMP signaling pathways in a spatial and temporal manner. Depending upon the specific cellular environments as well as their relative abundance, distribution and localization, Epac and PKA may act independently, converge synergistically or oppose each other in regulating a specific cellular function.
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Affiliation(s)
- Xiaodong Cheng
- Department of Pharmacology and Toxicology, Sealy Center for Cancer Cell Biology, University of Texas Medical Branch, Galveston, Texas 77555-1031, USA.
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18
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Fic E, Górecki A, Wasylewski Z. Fluorescence quenching studies of conformational changes induced by cAMP and DNA binding to heterodimer of cyclic AMP receptor protein from Escherichia coli. Protein J 2008; 26:457-66. [PMID: 17505875 DOI: 10.1007/s10930-007-9085-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
In Escherichia coli, cyclic AMP receptor protein (CRP) is known to regulate the transcription of about 100 genes. The signal to activate CRP is the binding of cyclic AMP. In this study the fluorescence quenching measurements were used to observe conformational changes in the structure of CRP after binding of cAMP and DNA. We used the constructed CRP heterodimer, which contains only a single Trp13 residue localized in the N-terminal domain of one CRP subunit. We propose that apo-CRP subunits exist in a solution in one conformational state and it changes after the ligand binding. We also suggest that the signal transmission upon binding of cAMP is possible not only from the N-terminal domain to C-terminal domain but also in the opposite direction after binding of specific DNA sequence, both with and without cAMP. Thereby it can influence on the CRP's interaction with RNA polymerase and the genes expression.
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Affiliation(s)
- Ewelina Fic
- Department of Physical Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7 str, Krakow, 30-387, Poland.
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19
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Bai G, Gazdik MA, Schaak DD, McDonough KA. The Mycobacterium bovis BCG cyclic AMP receptor-like protein is a functional DNA binding protein in vitro and in vivo, but its activity differs from that of its M. tuberculosis ortholog, Rv3676. Infect Immun 2007; 75:5509-17. [PMID: 17785469 PMCID: PMC2168296 DOI: 10.1128/iai.00658-07] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Mycobacterium tuberculosis Rv3676 encodes a cyclic AMP (cAMP) receptor-like protein (CRP(Mt)) that has been implicated in global gene regulation and may play an important role during tuberculosis infection. The CRP(Mt) ortholog in Mycobacterium bovis BCG, CRP(BCG), is dysfunctional in an Escherichia coli CRP competition assay and has been proposed as a potential source of M. bovis BCG's attenuation. We compared CRP(BCG) and CRP(Mt) in vitro and in vivo, in M. bovis BCG and M. tuberculosis, to evaluate CRP(BCG)'s potential function in a mycobacterial system. Both proteins formed dimers in mycobacterial lysates, bound to the same target DNA sequences, and were similarly affected by the presence of cAMP in DNA binding assays. However, CRP(Mt) and CRP(BCG) differed in their relative affinities for specific DNA target sequences and in their susceptibilities to protease digestion. Surprisingly, CRP(BCG) DNA binding activity was stronger than that of CRP(Mt) both in vitro and in vivo, as measured by electrophoretic mobility shift and chromatin immunoprecipitation assays. Nutrient starvation-associated regulation of several CRP(Mt) regulon members also differed between M. bovis BCG and M. tuberculosis. We conclude that CRP(BCG) is a functional cAMP-responsive DNA binding protein with an in vivo DNA binding profile in M. bovis BCG similar to that of CRP(Mt) in M. tuberculosis. However, biologically significant functional differences may exist between CRP(BCG) and CRP(Mt) with respect to gene regulation, and this issue warrants further study.
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Affiliation(s)
- Guangchun Bai
- Wadsworth Center, 120 New Scotland Avenue, PO Box 22002, Albany, NY 12201-2002, USA
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20
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Chen Y, McQuade KJ, Guan XJ, Thomason PA, Wert MS, Stock JB, Cox EC. Isoprenylcysteine carboxy methylation is essential for development in Dictyostelium discoideum. Mol Biol Cell 2007; 18:4106-18. [PMID: 17699599 PMCID: PMC1995708 DOI: 10.1091/mbc.e06-11-1006] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Members of the Ras superfamily of small GTPases and the heterotrimeric G protein gamma subunit are methylated on their carboxy-terminal cysteine residues by isoprenylcysteine methyltransferase. In Dictyostelium discoideum, small GTPase methylation occurs seconds after stimulation of starving cells by cAMP and returns quickly to basal levels, suggesting an important role in cAMP-dependent signaling. Deleting the isoprenylcysteine methyltransferase-encoding gene causes dramatic defects. Starving mutant cells do not propagate cAMP waves in a sustained manner, and they do not aggregate. Motility is rescued when cells are pulsed with exogenous cAMP, or coplated with wild-type cells, but the rescued cells exhibit altered polarity. cAMP-pulsed methyltransferase-deficient cells that have aggregated fail to differentiate, but mutant cells plated in a wild-type background are able to do so. Localization of and signaling by RasG is altered in the mutant. Localization of the heterotrimeric Ggamma protein subunit was normal, but signaling was altered in mutant cells. These data indicate that isoprenylcysteine methylation is required for intercellular signaling and development in Dictyostelium.
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Affiliation(s)
- Ying Chen
- *Department of Molecular Biology, Princeton University, Princeton, NJ 08544; and
| | - Kyle J. McQuade
- *Department of Molecular Biology, Princeton University, Princeton, NJ 08544; and
- Department of Biology, Mesa State College, Grand Junction, CO 81501
| | - Xiao-Juan Guan
- *Department of Molecular Biology, Princeton University, Princeton, NJ 08544; and
| | - Peter A. Thomason
- *Department of Molecular Biology, Princeton University, Princeton, NJ 08544; and
| | - Michael S. Wert
- *Department of Molecular Biology, Princeton University, Princeton, NJ 08544; and
| | - Jeffry B. Stock
- *Department of Molecular Biology, Princeton University, Princeton, NJ 08544; and
| | - Edward C. Cox
- *Department of Molecular Biology, Princeton University, Princeton, NJ 08544; and
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21
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Kanack KJ, Runyen-Janecky LJ, Ferrell EP, Suh SJ, West SEH. Characterization of DNA-binding specificity and analysis of binding sites of the Pseudomonas aeruginosa global regulator, Vfr, a homologue of the Escherichia coli cAMP receptor protein. Microbiology (Reading) 2006; 152:3485-3496. [PMID: 17159200 DOI: 10.1099/mic.0.29008-0] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Vfr, a global regulator of Pseudomonas aeruginosa virulence factors, is a homologue of the Escherichia coli cAMP receptor protein, CRP. Vfr is 91% similar to CRP and maintains many residues important for CRP to bind cAMP, bind DNA, and interact with RNA polymerase at target promoters. While vfr can complement an E. coli crp mutant in beta-galactosidase production, tryptophanase production and catabolite repression, crp can only complement a subset of Vfr-dependent phenotypes in P. aeruginosa. Using specific CRP binding site mutations, it is shown that Vfr requires the same nucleotides as CRP for optimal transcriptional activity from the E. coli lac promoter. In contrast, CRP did not bind Vfr target sequences in the promoters of the toxA and regA genes. Footprinting analysis revealed Vfr protected sequences upstream of toxA, regA, and the quorum sensing regulator lasR, that are similar to but significantly divergent from the CRP consensus binding sequence, and Vfr causes similar DNA bending to CRP in bound target sequences. Using a preliminary Vfr consensus binding sequence deduced from the Vfr-protected sites, Vfr target sequences were identified upstream of the virulence-associated genes plcN, plcHR, pbpG, prpL and algD, and in the vfr/orfX, argH/fimS, pilM/ponA intergenic regions. From these sequences the Vfr consensus binding sequence, 5'-ANWWTGNGAWNY : AGWTCACAT-3', was formulated. This study suggests that Vfr shares many of the same functions as CRP, but has specialized functions, at least in terms of DNA target sequence binding, required for regulation of a subset of genes in its regulon.
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Affiliation(s)
- Kristen J Kanack
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA
| | - Laura J Runyen-Janecky
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA
| | - Evan P Ferrell
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA
| | - Sang-Jin Suh
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA
| | - Susan E H West
- Department of Pathobiological Sciences, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA
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22
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Miroslavova NS, Mitchell JE, Tebbutt J, Busby SJW. Recruitment of RNA polymerase to Class II CRP-dependent promoters is improved by a second upstream-bound CRP molecule. Biochem Soc Trans 2006; 34:1075-8. [PMID: 17073754 DOI: 10.1042/bst0341075] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Genetics and biochemistry have been exploited to investigate transcription activation by the Escherichia coli CRP (cAMP receptor protein) factor at promoters with a DNA site for CRP near position −41 and the effects of a second upstream-bound CRP molecule. We show that the upstream-bound CRP contributes to transcription activation by improving the recruitment of RNA polymerase.
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Affiliation(s)
- N S Miroslavova
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
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23
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Abstract
Intercellular signaling mediated by cAMP plays a pivotal role in coordinating cell movement into aggregates at the early stage of Dictyostelium development when the extracellular level of cAMP periodically changes at 6- to 7-min intervals. We have shown that MAP kinase ERK2 is activated via the cAMP receptor CAR1 in phase with this periodic change. This was revealed by assessing the level of ERK2 activation with immunoblots using two kinds of antibodies, commercially available anti-phospho-p44/p42 MAP-kinase antibody and anti-Dictyostelium ERK2 antibody. In this chapter, we describe the methods we have used to assess the level of activated ERK2 and partial involvement of G protein in cAMP-induced ERK2 activation.
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Affiliation(s)
- Mineko Maeda
- Biological Science, Osaka University, Toyonaka, Japan
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24
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Abstract
This chapter describes biochemical assays with which to analyze signal transduction from surface cAMP receptors via G proteins to the effector enzymes adenylyl cyclase, guanylyl cyclase, and phospholipase C. The cAMP-mediated formation of the second messengers cAMP, cGMP, and Ins(1,4,5)P3 in cells will provide information on the entire pathway; here, details on isotope-dilution assays, through which the concentrations of these second messengers can be determined, are offered. Subsequently, several assays that analyze specific parts of the sensory transduction pathway are described. The assays include equilibrium and nonequilibrium binding to surface cAMP receptors on cells and on isolated membranes. The interaction between the cAMP receptor and G proteins can be measured as GTPgammaS-mediated inhibition of cAMP-binding to the receptor, or as cAMP-mediated stimulation of GTPase activity or GTPgammaS-binding to G proteins. Finally, assays for the in vitro G protein-mediated activation of the effector enzymes adenylyl cyclase, guanylyl cyclase, and phospholipase C are described.
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25
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Shpakov AO. [Structural and functional organisation of G protein signal systems of amoeba Dictyostelium discoideum ]. Zh Evol Biokhim Fiziol 2006; 42:426-44. [PMID: 17087006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
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Abstract
The availability of fully sequenced genomes allows the in silico analysis of whole gene families in a given genome. A particularly large and interesting gene family is the G-protein-coupled receptor family. These receptors detect a variety of extracellular signals and transduce them, generally via heterotrimeric G-proteins, to effector proteins inside the cell and thus elicit a physiological response. G-protein-coupled receptors are found in all eukaryotes and constitute in vertebrates 3-5% of all genes. They are also very important drug targets and approximately 25 of the top 100 selling drugs are directed against these receptors. The Dictyostelium discoideum genome contains a surprisingly high number of 55 such receptors, approximately 0.5% of the encoded genes. Besides the four well-studied cAMP receptors the genome encodes eight additional cAMP receptor-like proteins and one of these is distinguished by a novel domain structure, one secretin-like receptor, 17 GABA(B)-like and 25 Frizzled-like receptors. The existence of the latter three types of receptors in D. discoideum was surprising because they had not been observed outside the animal kingdom before. Their presence suggests unprecedentedly complex and so far unknown signaling activities in this lower eukaryote.
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Affiliation(s)
- Yogikala Prabhu
- Centre for Biochemistry, Medical Faculty, University of Cologne, Joseph-Stelzmann-Str. 52, D-50931 Köln, Germany
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Boeckeler K, Adley K, Xu X, Jenkins A, Jin T, Williams RSB. The neuroprotective agent, valproic acid, regulates the mitogen-activated protein kinase pathway through modulation of protein kinase A signalling in Dictyostelium discoideum. Eur J Cell Biol 2006; 85:1047-57. [PMID: 16759735 DOI: 10.1016/j.ejcb.2006.04.013] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Activation of the mitogen-activated protein kinase (MAPK) cascade gives rise to a neuroprotective effect in a variety of cell types. The bipolar disorder treatment, valproic acid (VPA), increases the activity of this pathway by modulating extracellular signal-regulated kinase 2 (ERK2) phosphorylation through an unknown mechanism. To investigate the molecular basis of this effect, we have used the biomedical model system Dictyostelium discoideum to dissect this signalling pathway. We find that, similar to mammalian systems, VPA causes a transient increase in the activation of the MAPK signalling pathway, as shown by ERK2 phosphorylation. We show that the MAP kinase and phosphatase, protein kinase A (PKA) and glycogen synthase kinase signalling pathways all function in controlling the levels of phospho-ERK2 (pERK2). We find that VPA induces elevated pERK2 levels through attenuation of the PKA signalling pathway. Interestingly, pERK2 levels are also controlled by another bipolar disorder drug, lithium, providing a common effect of these two drugs. This work therefore suggests a conserved pathway in eukaryotes that is targeted by neuroprotective and bipolar disorder drugs and allows us to propose a model for this neuroprotective effect.
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Affiliation(s)
- Katrina Boeckeler
- Department of Biology and the Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK
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28
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Choi MH, Sun HY, Park RY, Kim CM, Bai YH, Kim YR, Rhee JH, Shin SH. Effect of the crp mutation on the utilization of transferrin-bound iron by Vibrio vulnificus. FEMS Microbiol Lett 2006; 257:285-92. [PMID: 16553865 DOI: 10.1111/j.1574-6968.2006.00183.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Cyclic AMP-cAMP receptor protein (CRP) complex plays an essential role in the global regulation of Vibrio vulnificus virulence. We found that growth retardation of V. vulnificus caused by mutation of the crp gene encoding CRP was exacerbated under iron-limited conditions. Accordingly, we investigated the effect of crp mutation on the expression of the vulnibactin-mediated iron-uptake system and the ability of V. vulnificus to utilize transferrin-bound iron, and thus to grow in cirrhotic ascites, a human ex vivo system. The production of vulnibactin was suppressed, and the transcription of the vis and vuuA genes, which encode an enzyme required for vulnibactin synthesis and vulnibactin receptor protein, was also suppressed in the crp mutant. Moreover, the crp mutant could not utilize transferrin-bound iron, and its growth was severely suppressed both on transferrin-bound iron and in cirrhotic ascites. All the defects in the crp mutant were recovered by the in trans complementation of the wild-type crp gene. Putative CRP-binding sequences were found in the regulatory regions of the fur, vis and vuuA genes. These results indicate that crp mutation attenuates the ability to grow on transferrin-bound iron and in a human body fluid by down-regulating the vulnibactin-mediated iron-uptake system.
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Affiliation(s)
- Mi-Hwa Choi
- Research Center for Resistant Cells, Chosun University Medical School, Gwangju, Korea
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29
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Abstract
The discovery in 1947 of directed cell movement in Dictyostelium discoideum quietly gave a birth to a new line of investigation into the molecular basis of chemotaxis. Some 60 years later, D. discoideum continues to be a key model system for the study of eukaryotic chemotaxis as well as an array of other important biological processes. As one of the most influential scientists, Guenther Gerisch has inspired several generations of researchers with his insightful and rigorous approaches applied to this model system. His studies have greatly contributed to current knowledge of many fundamental processes, such as cell-cell adhesion, phagocytosis, endocytosis, cytokinesis, cell signaling and chemotaxis. In this review, we wish to look back at the journey that has led to our current understanding of chemotaxis of eukaryotic cells.
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Affiliation(s)
- Tian Jin
- Chemotaxis Signal Section, Laboratories of Immunogenetics, NIAID, NIH, Rockville, MD 20852, USA.
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30
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Abstract
Metabotropic glutamate receptors (mGluRs) are a class of G-protein-coupled receptors that possess a seven transmembrane region involved in the modulation of excitatory synaptic transmission in the nervous system. mGluR orthologs have been identified in Drosophila, Caenorhabditis elegans, and higher organisms. Drosophila possesses two mGluR genes, DmGluRA and DmXR. We screened the Dictyostelium genome data base using the ligand binding domain of rat mGluR1 as bait, and identified a new receptor, DdmGluPR, belonging to the mGluR family. Similar to Drosophila DmXR, the residues of mGluRs involved in the binding of the alpha-carboxylic and alpha-amino groups of glutamate were well conserved in DdmGluPR, but the residues interacting with the gamma-carboxylic group of glutamate were not. The phylogenetic analysis suggests that DdmGluPR diverged after the mGluR family-GABA(B) receptors split but before mGluR family divergence. DdmGluPR mRNA was expressed in vegetative cells and throughout starvation-induced development, but the level of the expression was relatively high until 4 h after starvation. DdmGluPR was localized to the plasma membrane of axenically grown Ax-2 cells expressed as a green fluorescent protein fusion protein. DdmGluPR-null cells grew faster at high cell density and reached higher densities than wild-type cells. DdmGluPR-null cells exhibited delayed aggregates formation upon starvation and impaired chemotaxis toward cAMP. Although expressions of cAR1 and aca, cAMP-signaling components, were rapidly induced and peaked at 2-4 h in wild-type cells, DdmGluPR-null cells displayed sustained and peaked at 8 h of the expressions of these genes. Our findings suggest the involvement of DdmGluPR in the early development of Dictyostelium discoideum.
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Affiliation(s)
- Hideo Taniura
- Laboratory of Molecular Pharmacology, Graduate School of Natural Science and Technology, Kanazawa University, Kakumamachi, Kanazawa, Ishikawa 920-1192, Japan.
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31
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Liţcanu G, Velázquez JJL. Singular perturbation analysis of cAMP signalling in Dictyostelium discoideum aggregates. J Math Biol 2006; 52:682-718. [PMID: 16521026 DOI: 10.1007/s00285-005-0370-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2005] [Revised: 11/30/2005] [Indexed: 11/28/2022]
Abstract
In this paper, we use singular perturbation methods to study the structure of travelling waves for some reaction-diffusion models obtained from the Martiel-Goldbeter and Goldbeter-Segel's models of cAMP signalling in Dictyostelium discoideum. As a consequence, we derive analytic formulae for quantities like wave speed, maximum concentration and other magnitudes in terms of the different biochemical constants that appear in the model.
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Affiliation(s)
- Gabriela Liţcanu
- Institute of Mathematics O. Mayer, Romanian Academy, Iaşi, Romania.
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32
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Abstract
A fundamental property of multicellular organisms is signal relay, the process by which information is transmitted from one cell to another. The integration of external information, such as nutritional status or developmental cues, is critical to the function of organisms. In addition, the spatial organizations of multicellular organisms require intricate signal relay mechanisms. Signal relay is remarkably exhibited during the life cycle of the social amoebae Dictyostelium discoideum, a eukaryote that retains a simple way of life, yet it has greatly contributed to our knowledge of the mechanisms cells use to communicate and integrate information. This chapter focuses on the molecules and mechanisms that Dictyostelium employs during its life cycle to relay temporal and spatial cues that are required for survival.
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Affiliation(s)
- Dana C Mahadeo
- Laboratory of Cellular and Molecular Biology, Center for Cancer Research, NCI, NIH, Bethesda, Maryland 20892, USA
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33
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Wickstrum JR, Santangelo TJ, Egan SM. Cyclic AMP receptor protein and RhaR synergistically activate transcription from the L-rhamnose-responsive rhaSR promoter in Escherichia coli. J Bacteriol 2005; 187:6708-18. [PMID: 16166533 PMCID: PMC1251584 DOI: 10.1128/jb.187.19.6708-6718.2005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Escherichia coli rhaSR operon encodes two AraC family transcription activator proteins, RhaS and RhaR, which regulate expression of the l-rhamnose catabolic regulon in response to l-rhamnose availability. RhaR positively regulates rhaSR in response to l-rhamnose, and RhaR activation can be enhanced by the cyclic AMP (cAMP) receptor protein (CRP) protein. CRP is a well-studied global transcription regulator that binds to DNA as a dimer and activates transcription in the presence of cAMP. We investigated the mechanism of CRP activation at rhaSR both alone and in combination with RhaR in vivo and in vitro. Base pair substitutions at potential CRP binding sites in the rhaSR-rhaBAD intergenic region demonstrate that CRP site 3, centered at position -111.5 relative to the rhaSR transcription start site, is required for the majority of the CRP-dependent activation of rhaSR. DNase I footprinting confirms that CRP binds to site 3; CRP binding to the other potential CRP sites at rhaSR was not detected. We show that, at least in vitro, CRP is capable of both RhaR-dependent and RhaR-independent activation of rhaSR from a total of three transcription start sites. In vitro transcription assays indicate that the carboxy-terminal domain of the alpha subunit (alpha-CTD) of RNA polymerase is at least partially dispensable for RhaR-dependent activation but that the alpha-CTD is required for CRP activation of rhaSR. Although CRP requires the presence of RhaR for efficient in vivo activation of rhaSR, DNase I footprinting assays indicated that cooperative binding between RhaR and CRP does not make a significant contribution to the mechanism of CRP activation at rhaSR. It therefore appears that CRP activates transcription from rhaSR as it would at simple class I promoters, albeit from a relatively distant position.
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Affiliation(s)
- Jason R Wickstrum
- Department of Molecular Biosciences, University of Kansas, 8031 Haworth Hall, 1200 Sunnyside Avenue, Lawrence, KS 66045-7534, USA
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Abstract
Diffusion of a chemoattractant from a micropipet is routinely used to examine the different aspects of a cell's chemotactic response. To quantify the effect of cell elongation on chemotactic sensitivity in the micropipet assay, the chemoattractant concentration at the cell plasma membrane was determined by solving the equation for diffusion from a point source in the presence of a prolate ellipsoid of varying eccentricity. The results show that cell elongation can significantly increase the difference in receptor occupancy between near and far cell ends and thereby enhance the sensitivity of chemotactic cells to shallow chemoattractant gradients.
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Affiliation(s)
- Igor Weber
- Department of Molecular Biology, Ruer Bosković Institute, Bijenicka 54, HR-10000 Zagreb, Croatia.
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35
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Chen Y, Rodrick V, Yan Y, Brazill D. PldB, a putative phospholipase D homologue in Dictyostelium discoideum mediates quorum sensing during development. Eukaryot Cell 2005; 4:694-702. [PMID: 15821129 PMCID: PMC1087817 DOI: 10.1128/ec.4.4.694-702.2005] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Quorum sensing, also known as cell-density sensing in the unicellular eukaryote Dictyostelium discoideum, is required for efficient entry into the differentiation and development segment of its life cycle. Quorum sensing is accomplished by simultaneously secreting and sensing the glycoprotein Conditioned Medium Factor, or CMF. When the density of starving cells is high, CMF levels are high, which leads to aggregation followed by development. Here, we describe the role of pldB, a gene coding for a putative phospholipase D (PLD) homologue, in quorum sensing. We find that in submerged culture, adding butanol, an inhibitor of PLD-catalyzed phosphatidic acid production, allows cells to bypass the requirement for CMF mediated quorum sensing and aggregate at low cell density. Deletion of pldB mimics the presence of butanol, allowing cells to aggregate at low cell density. pldB- cells also initiate and finish aggregation rapidly. Analysis of early developmental gene expression in pldB- cells reveals that the cyclic AMP receptor cAR1 is expressed at higher levels earlier than in wild-type cells, which could explain the rapid aggregation phenotype. As would be predicted, cells overexpressing pldB are unable to aggregate even at high cell density. Adding CMF to these pldB- overexpressing cells does not rescue aggregation. Both of these phenotypes are cell autonomous, as mixing a small number of pldB- cells with wild-type cells does not cause the wild-type cells to behave like pldB- cells.
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Affiliation(s)
- Yi Chen
- Department of Biological Sciences, Hunter College, New York, New York 10021, USA
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36
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Alvarez-Curto E, Rozen DE, Ritchie AV, Fouquet C, Baldauf SL, Schaap P. Evolutionary origin of cAMP-based chemoattraction in the social amoebae. Proc Natl Acad Sci U S A 2005; 102:6385-90. [PMID: 15851658 PMCID: PMC1088387 DOI: 10.1073/pnas.0502238102] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2005] [Indexed: 11/18/2022] Open
Abstract
Phenotypic novelties can arise if integrated developmental pathways are expressed at new developmental stages and then recruited to serve new functions. We analyze the origin of a novel developmental trait of Dictyostelid amoebae: the evolution of cAMP as a developmental chemoattractant. We show that cAMP's role of attracting starving amoebae arose through recruitment of a pathway that originally evolved to coordinate fruiting body morphogenesis. Orthologues of the high-affinity cAMP receptor (cAR), cAR1, were identified in a selection of species that span the Dictyostelid phylogeny. The cAR1 orthologue from the basal species Dictyostelium minutum restored aggregation and development when expressed in an aggregation-defective mutant of the derived species Dictyostelium discoideum that lacks high-affinity cARs, thus demonstrating that the D. minutum cAR is a fully functional cAR. cAR1 orthologues from basal species are expressed during fruiting body formation, and only this process, and not aggregation, was disrupted by abrogation of cAR1 function. This is in contrast to derived species, where cAR1 is also expressed during aggregation and critically regulates this process. Our data show that coordination of fruiting body formation is the ancestral function of extracellular cAMP signaling, whereas its derived role in aggregation evolved by recruitment of a preexisting pathway to an earlier stage of development. This most likely occurred by addition of distal cis-regulatory regions to existing cAMP signaling genes.
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Affiliation(s)
- Elisa Alvarez-Curto
- School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom
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37
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Wang L, Hashimoto Y, Tsao CY, Valdes JJ, Bentley WE. Cyclic AMP (cAMP) and cAMP receptor protein influence both synthesis and uptake of extracellular autoinducer 2 in Escherichia coli. J Bacteriol 2005; 187:2066-76. [PMID: 15743955 PMCID: PMC1064054 DOI: 10.1128/jb.187.6.2066-2076.2005] [Citation(s) in RCA: 146] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Bacterial autoinducer 2 (AI-2) is proposed to be an interspecies mediator of cell-cell communication that enables cells to operate at the multicellular level. Many environmental stimuli have been shown to affect the extracellular AI-2 levels, carbon sources being among the most important. In this report, we show that both AI-2 synthesis and uptake in Escherichia coli are subject to catabolite repression through the cyclic AMP (cAMP)-CRP complex, which directly stimulates transcription of the lsr (for "luxS regulated") operon and indirectly represses luxS expression. Specifically, cAMP-CRP is shown to bind to a CRP binding site located in the upstream region of the lsr promoter and works with the LsrR repressor to regulate AI-2 uptake. The functions of the lsr operon and its regulators, LsrR and LsrK, previously reported in Salmonella enterica serovar Typhimurium, are confirmed here for E. coli. The elucidation of cAMP-CRP involvement in E. coli autoinduction impacts many areas, including the growth of E. coli in fermentation processes.
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Affiliation(s)
- Liang Wang
- Center for Biosystems Research, University of Maryland Biotechnology Institute, College Park, MD 20742, USA
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38
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Abstract
We have previously reported that cells of Dictyostelium discoideum lacking the fatty acid oxidation enzyme MFE1 accumulate excess cyclopropane fatty acids from ingested bacteria. Cells in which mfeA(-) is disrupted fail to develop when grown in association with bacteria but form normal fruiting bodies when grown in axenic media. Bacterially grown mfeA(-) cells express the genes for the cyclic AMP (cAMP) receptor (carA) and adenylyl cyclase (acaA) but fail to respond to a cAMP pulse by synthesis of additional cAMP which normally relays the signal. Moreover, they do not accumulate the adhesion protein, gp80, which is encoded by the cAMP-induced gene, csaA. As a consequence, they do not acquire developmentally regulated EDTA-resistant cell-cell adhesion. When mutant cells are mixed with wild-type cells and allowed to develop together, they co-aggregate and differentiate into both spores and stalk cells. Thus, most of the developmental consequences of excess cyclopropane fatty acids appear to result from impaired cAMP relay.
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Affiliation(s)
- Satomi Matsuoka
- Department of Biology, Graduate School of Science, Osaka University, 1-16 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan
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Abstract
Dd-TRAP1 is a Dictyostelium homologue of tumor necrosis factor receptor-associated protein 1 (TRAP-1). Dd-TRAP1 is located in the cortex of cells growing at a low density, but was found to be translocated to mitochondria with the help of a novel prestarvation factor that was accumulated in growth medium along with increased cell densities. The knockdown mutant of Dd-TRAP1 (TRAP1-RNAi cells) exhibited a significant defect in prestarvation response. Although TRAP1-RNAi cells showed normal expressions of classical prestarvation genes [dscA (discoidin I) and car1 (carA; cAMP receptor)], the expression of differentiation-associated genes (dia1 and dia3) induced by the prestarvation response were markedly repressed. By contrast, transformants overexpressing Dd-TRAP1 showed an early prestarvation response and also increased expression of dia1 and dia3 in a cell-density-dependent manner. Importantly, introduction of Dd-TRAP1 antibody into D. discoideum Ax-2 cells by electroporation inhibited the translocation of Dd-TRAP1 from the cortex to mitochondria and greatly inhibited the initiation of differentiation. Taken together, these results indicate that Dd-TRAP1 is translocated to mitochondria by sensing the cell density in growth medium and enhances the early developmental program through a novel prestarvation response.
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Affiliation(s)
- Tsuyoshi Morita
- Department of Developmental Biology and Neurosciences, Graduate School of Life Sciences, Tohoku University, Aoba, Sendai 980-8578, Japan
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40
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Abstract
Cyclic AMP receptor protein (CRP) binds to DNA and induces DNA bending. DNA bending plays an important role in transcription activation of many genes in Escherichia coli. To know DNA helical change by CRP, we used molar cyclization factor (j(M)), which is sensitive to helical twist or torsional alignment. Six consecutive DNA fragments were constructed that contained phasing sequence at left arm and CRP binding site in center. j(M) values measured in this study were approximately 10 times increased by CRP relative to that measured for DNA only. The analysis of set of j(M) values indicated that CRP induced DNA bending without the helical change like helical twisting or torsional alignment change.
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Affiliation(s)
- JongBack Gang
- Department of Chemistry, Kyungwon University, Sungnam, Republic of Korea.
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Suzuki T, Yoshimura H, Hisabori T, Ohmori M. Two cAMP receptor proteins with different biochemical properties in the filamentous cyanobacterium Anabaena sp. PCC 7120. FEBS Lett 2004; 571:154-60. [PMID: 15280034 DOI: 10.1016/j.febslet.2004.06.074] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2004] [Revised: 06/24/2004] [Accepted: 06/28/2004] [Indexed: 10/26/2022]
Abstract
Two open reading frames (ORFs), alr0295 and alr2325, are found to encode putative cAMP receptor proteins (CRPs) in the genome of the filamentous cyanobacterium Anabaena sp. PCC 7120. These ORFs were named cAMP receptor protein-like gene A in Anabaena sp. PCC 7120 (ancrpA) and cAMP receptor protein-like gene B in Anabaena sp. PCC 7120 (ancrpB), respectively, and those translated products were investigated. The equilibrium dialysis measurements revealed that AnCrpA bound with cAMP specifically, while AnCrpB bound with both cAMP and cGMP, though the affinity for cGMP was weak. The binding affinity for cAMP of AnCrpA showed the lowest dissociation constant, approximately 0.8 microM, among bacterial CRPs. A gel mobility shift assay elucidated that AnCrpA and AnCrpB formed a complex with the consensus DNA sequence in the presence of cAMP, although AnCrpB did not have ordinary DNA-binding motifs.
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Affiliation(s)
- Takayuki Suzuki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro, Tokyo 153-8902, Japan
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42
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Maeda M, Lu S, Shaulsky G, Miyazaki Y, Kuwayama H, Tanaka Y, Kuspa A, Loomis WF. Periodic signaling controlled by an oscillatory circuit that includes protein kinases ERK2 and PKA. Science 2004; 304:875-8. [PMID: 15131307 DOI: 10.1126/science.1094647] [Citation(s) in RCA: 133] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Self-regulating systems often use robust oscillatory circuits. One such system controls the chemotactic signaling mechanism of Dictyostelium, where pulses of adenosine 3',5'-monophosphate (cAMP) are generated with a periodicity of 7 minutes. We have observed spontaneous oscillations in activation of the mitogen-activated protein (MAP) kinase ERK2 that occur in phase with peaks of cAMP, and we show that ERK2 modulates cAMP levels through the phosphodiesterase RegA. Computer modeling and simulations of the underlying circuit faithfully account for the ability of the cells to spontaneously generate periodic pulses during specific stages of development. Similar oscillatory processes may occur in cells of many different species.
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Affiliation(s)
- Mineko Maeda
- Department of Biology, Graduate School of Science, Osaka University, Machikaneyama-cho 1-16, Toyonaka, Osaka 560-0043, Japan
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Liu M, Tolstorukov M, Zhurkin V, Garges S, Adhya S. A mutant spacer sequence between -35 and -10 elements makes the Plac promoter hyperactive and cAMP receptor protein-independent. Proc Natl Acad Sci U S A 2004; 101:6911-6. [PMID: 15118087 PMCID: PMC406441 DOI: 10.1073/pnas.0401929101] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To determine whether the spacer region between the -35 and -10 elements plays any sequence-specific role, we randomized the GC-rich sequence ((-20)CCGGCTCG(-13)) within the spacer region of the cAMP-dependent lac promoter and selected an activator-independent mutant, which showed extraordinarily high intrinsic activity. The hyperactive promoter is obtained by incorporation of a specific 10-bp-long AT-rich DNA sequence within the spacer, referred to as the -15 sequence, which must be juxtaposed to the upstream end of the -10 sequence for the hyperactivity. The transcription enhancement functions only in the presence of a -35 element. The spacer sequence enhanced both RNA polymerase binding and open complex formation. Isolated in the lac promoter, it also enhanced transcription when placed at two other unrelated promoters. Sequence analysis shows a low GC content and an abundance of stereochemically flexible TG:CA and TA:TA dimeric steps in the -18/-9 region and a strong correlation between the presence of flexible dimeric steps in this region and the intrinsic strength of the promoter.
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Affiliation(s)
- Mofang Liu
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA
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44
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Affiliation(s)
- Mark A Landree
- Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, MD, USA
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45
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Brock DA, Ehrenman K, Ammann R, Tang Y, Gomer RH. Two components of a secreted cell number-counting factor bind to cells and have opposing effects on cAMP signal transduction in Dictyostelium. J Biol Chem 2003; 278:52262-72. [PMID: 14557265 DOI: 10.1074/jbc.m309101200] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
A secreted 450-kDa complex of proteins called counting factor (CF) is part of a negative feedback loop that regulates the size of the groups formed by developing Dictyostelium cells. Two components of CF are countin and CF50. Both recombinant countin and recombinant CF50 decrease group size in Dictyostelium. countin- cells have a decreased cAMP-stimulated cAMP pulse, whereas recombinant countin potentiates the cAMP pulse. We find that CF50 cells have an increased cAMP pulse, whereas recombinant CF50 decreases the cAMP pulse, suggesting that countin and CF50 have opposite effects on cAMP signal transduction. In addition, countin and CF50 have opposite effects on cAMP-stimulated Erk2 activation. However, like recombinant countin, recombinant CF50 increases cell motility. We previously found that cells bind recombinant countin with a Hill coefficient of approximately 2, a KH of 60 pm, and approximately 53 sites/cell. We find here that cells also bind 125I-recombinant CF50, with a Hill coefficient of approximately 2, a KH of approximately 15 ng/ml (490 pm), and approximately 56 sites/cell. Countin and CF50 require each other's presence to affect group size, but the presence of countin is not necessary for CF50 to bind to cells, and CF50 is not necessary for countin to bind to cells. Our working hypothesis is that a signal transduction pathway activated by countin binding to cells modulates a signal transduction pathway activated by CF50 binding to cells and vice versa and that these two pathways can be distinguished by their effects on cAMP signal transduction.
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Affiliation(s)
- Debra A Brock
- Howard Hughes Medical Institute, Rice University, Houston, Texas 77005-1892, USA
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46
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Abstract
Cyclic AMP (cAMP) has traditionally been thought to act exclusively through cAMP-dependent protein kinase (cAPK, PKA), but a growing number of cAMP effects are not attributable to general activation of cAPK. At present, cAMP is known also to directly regulate ion channels and the ubiquitous Rap guanine exchange factors Epac 1 and 2. Adding to the sophistication of cAMP signaling is the fact that (1) the cAPK holoenzyme is incompletely dissociated even at saturating cAMP, the level of free R subunit of cAPK being able to regulate the maximal activity of cAPK, (2) cAPK activity can be modulated by oxidative glutathionylation, and (3) cAPK is anchored close to relevant substrates, other signaling enzymes, and local compartments of cAMP. Finally, we will demonstrate an example of fine-tuning of cAMP signaling through synergistic induction of neurite extensions by cAPK and Epac.
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Affiliation(s)
- Reidun Kopperud
- Department of Anatomy and Cell Biology, University of Bergen, Jonas Lies vei 91, N-5009 Bergen, Norway
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47
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Abstract
Cells migrating directionally toward a chemoattractant source display a highly polarized cytoskeletal organization, with F-actin localized predominantly at the anterior and myosin II at the lateral and posterior regions. Dictyostelium discoideum has proven a useful system for elucidating signaling pathways that regulate this chemotactic response. During development, extracellular adenosine 3', 5' monophosphate (cAMP) functions as a primary signal to activate cell surface cAMP receptors (cARs). These receptors transduce different signals depending on whether or not they are coupled to heterotrimeric guanine nucleotide-binding proteins (G proteins) (see the STKE Connections Maps). Multiple G protein-stimulated pathways interact to establish polarity in chemotaxing D. discoideum cells by localizing F-actin at their leading edge and by regulating the phosphorylation state and assembly of myosin II. Many of the molecular interactions described are fundamental to the regulation of chemotaxis in other eukaryotic cells.
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Affiliation(s)
- Alan R Kimmel
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, Bethesda, MD 20892, USA
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48
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Abstract
Shewanella oneidensis is a metal reducer that can use several terminal electron acceptors for anaerobic respiration, including fumarate, nitrate, dimethyl sulfoxide (DMSO), trimethylamine N-oxide (TMAO), nitrite, and insoluble iron and manganese oxides. Two S. oneidensis mutants, SR-558 and SR-559, with Tn5 insertions in crp, were isolated and analyzed. Both mutants were deficient in Fe(III) and Mn(IV) reduction. They were also deficient in anaerobic growth with, and reduction of, nitrate, fumarate, and DMSO. Although nitrite reductase activity was not affected by the crp mutation, the mutants failed to grow with nitrite as a terminal electron acceptor. This growth deficiency may be due to the observed loss of cytochromes c in the mutants. In contrast, TMAO reduction and growth were not affected by loss of cyclic AMP (cAMP) receptor protein (CRP). Fumarate and Fe(III) reductase activities were induced in rich medium by the addition of cAMP to aerobically growing wild-type S. oneidensis. These results indicate that CRP and cAMP play a role in the regulation of anaerobic respiration, in addition to their known roles in catabolite repression and carbon source utilization in other bacteria.
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Affiliation(s)
- Daad A Saffarini
- Department of Biological Sciences, University of Wisconsin--Milwaukee, Milwaukee, Wisconsin 53211, USA.
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49
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Abstract
The activated Escherichia coli cAMP receptor protein, CRP, is capable of regulating the expression of more than 20 genes by binding to specific DNA sites. DNA bending is an important structural feature that has been observed in the regulatory mechanism of gene expression by CRP. On the basis of the results of the fluorescence energy transfer study of the gal P1 promoter, gal bends asymmetrically upon binding to CRP, although DNA bends symmetrically in the CRP-lac complex. The flanking sequence proximal to the TGTGA motif is involved in a sharper bend than the other side with an overall bending angle of approximately 90-125 degrees, without wrapping around the CRP molecule. To understand the factors that control the symmetry in DNA bending, a series of DNA sequences was tested to dissect the contribution of half-sites and flanking sequences, using the natural gal P1 and lac P1 sequences as initial targets. The extent of DNA bending induced by CRP was monitored by the difference in fluorescence anisotropy between free DNA and the DNA-CRP complex. The extent of bending was sequence-dependent, and most importantly, the symmetry of bending was a function of the symmetry of the DNA sequence. For example, in the lac promoter the two binding half-sites (TGTGA and TCACT) were almost symmetric as an inverted repeat. The recognition F-helices of the two CRP subunits would bind to these half-sites with a 2-fold symmetry. The flanking sequences (ATAAA and CATTA) were almost identical mirror images. Thus, they are expected to bend in a similar manner. Finally, the sequence symmetry properties of a series of natural CRP promoters were analyzed. A strong tendency for symmetry sequence was encoded in class I promoter sites but not in class II promoter sites. Results from this analysis support the conclusion that the geometry of the CRP-DNA complex plays a major role in determining the molecular mechanism in gene transcription.
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Affiliation(s)
- Shwu-Hwa Lin
- Department of Human Biological Chemistry and Genetics, The University of Texas Medical Branch at Galveston, Galveston, Texas 77555-1055, USA
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50
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Chen R, Lee JC. Functional roles of loops 3 and 4 in the cyclic nucleotide binding domain of cyclic AMP receptor protein from Escherichia coli. J Biol Chem 2003; 278:13235-43. [PMID: 12551924 DOI: 10.1074/jbc.m211551200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cyclic AMP is a ubiquitous secondary message that regulates a large variety of functions. The protein structural motif that binds cAMP is highly conserved with the exception of loops 3 and 4, whose structure and length are variable. The cAMP receptor protein of Escherichia coli, CRP, was employed as a model system to elucidate the functional roles of these loops. Based on the sequence differences between CRP and cyclic nucleotide gated channel, three mutants of CRP were constructed: deletion (residues 54-56 in loop 3 were deleted), insertion (loop 4 was lengthened by 5 residues between Glu-78 and Gly-79) and double mutants. The effects of these mutations on the structure and function of CRP were monitored. Results show that the deletion and insertion mutations do not significantly change the secondary structure of CRP, although the tertiary and quaternary structures are perturbed. The functional data indicate that loop 3 modulates the binding affinities of cAMP and DNA. Although the lengthened loop 4 may have some fine-tuning functions, the specific function of the original loop 4 of CRP remains uncertain. The function consequences of mutation in loop 3 of CRP are similar to that of site A and site B in the regulatory subunits of cyclic AMP-dependent protein kinases. Thus, the roles played by loop 3 in CRP may represent a more common mechanism employed by cyclic nucleotide binding domain in modulating ligand binding affinity and intramolecular communication.
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Affiliation(s)
- Ran Chen
- Department of Human Biological Chemistry and Genetics, University of Texas Medical Branch, Galveston, Texas 77555-1055, USA
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