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Li S, Liu Y, Weng L, Zhao Y, Zhang Y, Zhang Z, Yang Y, Chen Q, Liu X, Zhang H. The F 1F o-ATP synthase α subunit of Candida albicans induces inflammatory responses by controlling amino acid catabolism. Virulence 2023; 14:2190645. [PMID: 36914568 PMCID: PMC10072111 DOI: 10.1080/21505594.2023.2190645] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2022] [Revised: 02/08/2023] [Accepted: 03/09/2023] [Indexed: 03/15/2023] Open
Abstract
Sepsis is a leading cause of fatality in invasive candidiasis. The magnitude of the inflammatory response is a determinant of sepsis outcomes, and inflammatory cytokine imbalances are central to the pathophysiological processes. We previously demonstrated that a Candida albicans F1Fo-ATP synthase α subunit deletion mutant was nonlethal to mice. Here, the potential effects of the F1Fo-ATP synthase α subunit on host inflammatory responses and the mechanism were studied. Compared with wild-type strain, the F1Fo-ATP synthase α subunit deletion mutant failed to induce inflammatory responses in Galleria mellonella and murine systemic candidiasis models and significantly decreased the mRNA levels of the proinflammatory cytokines IL-1β, IL-6 and increased those of the anti-inflammatory cytokine IL-4 in the kidney. During C. albicans-macrophage co-culture, the F1Fo-ATP synthase α subunit deletion mutant was trapped inside macrophages in yeast form, and its filamentation, a key factor in inducing inflammatory responses, was inhibited. In the macrophage-mimicking microenvironment, the F1Fo-ATP synthase α subunit deletion mutant blocked the cAMP/PKA pathway, the core filamentation-regulating pathway, because it failed to alkalinize environment by catabolizing amino acids, an important alternative carbon source inside macrophages. The mutant downregulated Put1 and Put2, two essential amino acid catabolic enzymes, possibly due to severely impaired oxidative phosphorylation. Our findings reveal that the C. albicans F1Fo-ATP synthase α subunit induces host inflammatory responses by controlling its own amino acid catabolism and it is significant to find drugs that inhibit F1Fo-ATP synthase α subunit activity to control the induction of host inflammatory responses.
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Affiliation(s)
- Shuixiu Li
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
| | - Yuting Liu
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
| | - Luobei Weng
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
| | - Yajing Zhao
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
| | - Yishan Zhang
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
| | - Zhanpeng Zhang
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
| | - Yang Yang
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
| | - Qiaoxin Chen
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
| | - Xiaocong Liu
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
| | - Hong Zhang
- Department of Dermatology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
- Institute of Mycology, Jinan University, Guangzhou, Guangdong, China
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Li S, Shen W, Lian S, Wu Y, Qu Y, Deng Y. DARHD: A sequence database for aromatic ring-hydroxylating dioxygenase analysis and primer evaluation. J Hazard Mater 2022; 436:129230. [PMID: 35739750 DOI: 10.1016/j.jhazmat.2022.129230] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 05/19/2022] [Accepted: 05/23/2022] [Indexed: 06/15/2023]
Abstract
Biodegradation of aromatic compounds is ubiquitous in the environment and important for controlling organic pollutants. Aromatic ring-hydroxylating dioxygenases (ARHDs) are responsible for the first and rate-limiting step of aerobic biodegradation of aromatic compounds. The ARHD α subunit is a good biomarker for studying functional microorganisms in the environment, however their diversity and corresponding primer coverage are unclear, both of which require a comprehensive sequence database for the ARHD α subunit. Here amino acid sequences of the ARHD α subunit were collected, and a total of 103 sequences were selected as seed sequences that were distributed in 72 bacterial genera with 34 gene names. Based on both homolog search and keyword confirmation against the GenBank, a sequence database of ARHD (DARHD) has been established and 6367 highly credible sequences were retrieved. DARHD contained 407 bacterial genera capable of degrading 38 aromatic substrates, and intricate relationships among the gene name, aromatic substrate and microbial taxa were observed. Thereafter, a total of 136 pairs of primers were collected and assessed. Results showed coverages of most published primers were low. Our research provides new insights for understanding the diversity of ARHD α subunit, and gives guidance on the design and application of primers in the future.
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Affiliation(s)
- Shuzhen Li
- CAS Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Aquatic EcoHealth Group, Fujian Key Laboratory of Watershed Ecology, Key Laboratory of Urban Environment and Health, Institute of Urban Environment, Chinese Academy of Sciences, Xiamen 361021, China
| | - Wenli Shen
- Institute for Marine Science and Technology, Shandong University, Qingdao 266237, China
| | - Shengyang Lian
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education) and Dalian POCT Laboratory, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Yueni Wu
- CAS Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Yuanyuan Qu
- Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education) and Dalian POCT Laboratory, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China
| | - Ye Deng
- CAS Key Laboratory of Environmental Biotechnology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; Institute for Marine Science and Technology, Shandong University, Qingdao 266237, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China.
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Li LL, Ke XY, Jiang C, Qin SQ, Liu YY, Xian XH, Liu LZ, He JC, Chen YM, An HF, Sun N, Hu YH, Wang Y, Zhang LN, Lu QY. Na + , K + -ATPase participates in the protective mechanism of rat cerebral ischemia-reperfusion through the interaction with glutamate transporter-1. Fundam Clin Pharmacol 2021; 35:870-881. [PMID: 33481320 DOI: 10.1111/fcp.12652] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 01/19/2021] [Indexed: 11/30/2022]
Abstract
Glutamate excitotoxicity in cerebral ischemia/reperfusion is an important cause of neurological damage. The aim of this study was to investigate the mechanism of Na+, K+-ATPase (NKA) involved in l ow concentration of ouabain (Oua, activating NKA)-induced protection of rat cerebral ischemia-reperfusion injury. The 2,3,5-triphenyltetrazolium chloride (TTC) staining and neurological deficit scores (NDS) were performed to evaluate rat cerebral injury degree respectively at 2 h, 6 h, 1 d and 3 d after reperfusion of middle cerebral artery occlusion (MCAO) 2 h in rats. NKA α1/α2 subunits and glutamate transporter-1 (GLT-1) protein expression were investigated by Western blotting. The cerebral infarct volume ratio were evidently decreased in Oua group vs MCAO/R group at 1 d and 3 d after reperfusion of 2 h MCAO in rats (*p < 0.05 ). Moreover, NDS were not significantly different (p > 0.05 ). NKA α1 was decreased at 6 h and 1 d after reperfusion of 2 h MCAO in rats, and was improved in Oua group. However, NKA α1 and α2 were increased at 3 d after reperfusion of 2 h MCAO in rats, and was decreased in Oua group. GLT-1 was decreased at 6 h, 1 d and 3 d after reperfusion of 2 h MCAO in rats, and was improved in Oua group. These data indicated that l ow concentration of Oua could improve MCAO/R injury through probably changing NKA α1/α2 and GLT-1 protein expression, then increasing GLT-1 function and promoting Glu transport and absorption, which could be useful to determine potential therapeutic strategies for patients with stroke. Low concentration of Oua improved rat MCAO/R injury via NKA α1/α2 and GLT-1.
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Affiliation(s)
- Lin-Lin Li
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Xue-Ying Ke
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Chen Jiang
- Forensic Medical College, Hebei Medical University, Hebei, China
| | - Shi-Qi Qin
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Yang-Yang Liu
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Xiao-Hui Xian
- Department of Pathophysiology, Hebei Medical University, Hebei, China
| | - Li-Zhe Liu
- Department of Pathophysiology, Hebei Medical University, Hebei, China
| | - Jin-Chen He
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Ya-Meng Chen
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Hong-Fei An
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Nan Sun
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Yue-Hua Hu
- Basic Medical College, Hebei Medical University, Hebei, China
| | - Yan Wang
- North China University of Science and Technology Affiliated Hospital, Hebei, China
| | - Li-Nan Zhang
- Department of Pathophysiology, Hebei Medical University, Hebei, China
| | - Qi-Yong Lu
- Department of Neurosurgery, Hengshui Fifth People's Hospital, Hebei, China
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Mattei C, Taly A, Soualah Z, Saulais O, Henrion D, Guérineau NC, Verleye M, Legros C. Involvement of the GABA A receptor α subunit in the mode of action of etifoxine. Pharmacol Res 2019; 145:104250. [PMID: 31059790 DOI: 10.1016/j.phrs.2019.04.034] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2018] [Revised: 03/21/2019] [Accepted: 04/27/2019] [Indexed: 12/31/2022]
Abstract
Etifoxine (EFX) is a non-benzodiazepine psychoactive drug which exhibits anxiolytic effects through a dual mechanism, by directly binding to GABAA receptors (GABAARs) and to the mitochondrial 18-kDa translocator protein, resulting in the potentiation of the GABAergic function. The β subunit subtype plays a key role in the EFX-GABAAR interaction, however this does not explain the anxiolytic effects of this drug. Here, we combined behavioral and electrophysiological experiments to challenge the role of the GABAAR α subunit in the EFX mode of action. After single administrations of anxiolytic doses (25-50 mg/kg, intraperitoneal), EFX did not induce any neurological nor locomotor impairments, unlike the benzodiazepine bromazepam (0.5-1 mg/kg, intraperitoneal). We established the EFX pharmacological profile on heteropentameric GABAARs constructed with α1 to α6 subunit expressed in Xenopus oocyte. Unlike what is known for benzodiazepines, neither the γ nor δ subunits influenced EFX-mediated potentiation of GABA-evoked currents. EFX acted first as a partial agonist on α2β3γ2S, α3β3γ2S, α6β3γ2S and α6β3δ GABAARs, but not on α1β3γ2S, α4β3γ2S, α4β3δ nor α5β3γ2S GABAARs. Moreover, EFX exhibited much higher positive allosteric modulation towards α2β3γ2S, α3β3γ2S and α6β3γ2S than for α1β3γ2S, α4β3γ2S and α5β3γ2S GABAARs. At 20 μM, corresponding to brain concentration at anxiolytic doses, EFX increased GABA potency to the highest extent for α3β3γ2S GABAARs. We built a docking model of EFX on α3β3γ2S GABAARs, which is consistent with a binding site located between α and β subunits in the extracellular domain. In conclusion, EFX preferentially potentiates α2β3γ2S and α3β3γ2S GABAARs, which might support its advantageous anxiolytic/sedative balance.
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Affiliation(s)
- César Mattei
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France.
| | - Antoine Taly
- Theoretical Biochemistry Laboratory, Institute of Physico-Chemical Biology, CNRS UPR9080, University of Paris Diderot Sorbonne Paris Cité, 75005 Paris, France
| | - Zineb Soualah
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France
| | - Ophélie Saulais
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France
| | - Daniel Henrion
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France
| | - Nathalie C Guérineau
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France
| | - Marc Verleye
- Biocodex, Department of Pharmacology, Zac de Mercières, 60200 Compiègne, France
| | - Christian Legros
- Institut MITOVASC, UMR CNRS 6015 - UMR INSERM U1083, Université d'Angers, 3 Rue Roger Amsler 49100 ANGERS, France.
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Hikida M, Shimada S, Kurata R, Shigetou S, Ihara M, Sattelle DB, Matsuda K. Combined effects of mutations in loop C and the loop D-E-G triangle on neonicotinoid interactions with Drosophila Dα1/chicken β2 hybrid nAChRs. Pestic Biochem Physiol 2018; 151:47-52. [PMID: 30704712 DOI: 10.1016/j.pestbp.2018.03.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 03/01/2018] [Accepted: 03/21/2018] [Indexed: 06/09/2023]
Abstract
Neonicotinoid insecticides interact with the orthosteric sites of nicotinic acetylcholine receptors (nAChRs) formed at the interfaces of (a) two adjacent α subunits and (b) α and non-α subunits. However, little is known of the detailed contributions of these two orthosteric sites to neonicotinoid actions. We therefore applied voltage-clamp electrophysiology to the Dα1/chicken β2 hybrid nAChR expressed in Xenopus laevis oocytes to explore the agonist actions of imidacloprid and thiacloprid on wild type receptors and following binding site mutations. First, we studied the S221E mutation in loop C of the ACh binding site of the Dα1 subunit. Secondly, we explored the impact of combining this mutation in loop C with others in the loop D-E-G triangle (R57S; E78K; K140T; S221E). The S221E loop C mutation alone reduced the affinity of the neonicotinoids tested, while hardly affecting the concentration-response curve for acetylcholine. Addition of the three R57S; E78K; K140T mutations in the loop D-E-G triangle led to a further reduction in neonicotinoid sensitivity, suggesting that all four binding site loops (C, D, E, G) in the Dα1 subunit, which are located upstream of loop B in the N-terminal, extracellular domain, contribute to the selective actions of neonicotinoid insecticides.
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Affiliation(s)
- Mai Hikida
- Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan
| | - Shota Shimada
- Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan
| | - Ryo Kurata
- Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan
| | - Sho Shigetou
- Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan
| | - Makoto Ihara
- Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan
| | - David B Sattelle
- Centre for Respiratory Biology, UCL Respiratory, Rayne Building, University College London, London WC1E 6JF, United Kingdom
| | - Kazuhiko Matsuda
- Department of Applied Biological Chemistry, Faculty of Agriculture, Kindai University, 3327-204 Nakamachi, Nara 631-8505, Japan.
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Jiang Y, Xiao Y, Zhang X, Shu Y. Activation of axon initial segmental GABA A receptors inhibits action potential generation in neocortical GABAergic interneurons. Neuropharmacology 2018; 138:97-105. [PMID: 29883765 DOI: 10.1016/j.neuropharm.2018.05.026] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 05/14/2018] [Accepted: 05/20/2018] [Indexed: 10/16/2022]
Abstract
Ionotropic GABAA receptors expressing at the axon initial segment (AIS) of glutamatergic pyramidal cell (PC) in the cortex plays critical roles in regulating action potential generation. However, it remains unclear whether these receptors also express at the AIS of cortical GABAergic interneurons. In mouse prefrontal cortical slices, we performed experiments at the soma and AIS of the two most abundant GABAergic interneurons: parvalbumin (PV) and somatostatin (SST) positive neurons. Local application of GABA at the perisomatic axonal regions could evoke picrotoxin-sensitive currents with a reversal potential near the Cl- equilibrium potential. Puffing agonists to outside-out patches excised from AIS confirmed the expression of GABAA receptors. Further pharmacological experiments revealed that GABAA receptors in AIS of PV neurons contain α1 subunits, different from those containing α2/3 in AIS and α4 in axon trunk of layer-5 PCs. Cell-attached recording at the soma of PV and SST neurons revealed that the activation of AIS GABAA receptors inhibits the action potential generation induced by synaptic stimulation. Together, our results demonstrate that the AIS of PV and SST neurons express GABAA receptors with distinct subunit composition, which exert an inhibitory effect on neuronal excitability in these inhibitory interneurons.
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Affiliation(s)
- Yanbo Jiang
- Institute of Neuroscience and State Key Laboratory of Neuroscience, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences and University of Chinese Academy of Sciences, Shanghai 200031, China
| | - Yujie Xiao
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, Beijing Normal University, Beijing 100875, China
| | - Xiaoxue Zhang
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, Beijing Normal University, Beijing 100875, China
| | - Yousheng Shu
- State Key Laboratory of Cognitive Neuroscience and Learning, IDG/McGovern Institute for Brain Research, School of Brain and Cognitive Sciences, Beijing Normal University, Beijing 100875, China.
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Li SX, Song YJ, Zhang YS, Wu HT, Guo H, Zhu KJ, Li DM, Zhang H. Mitochondrial Complex V α Subunit Is Critical for Candida albicans Pathogenicity through Modulating Multiple Virulence Properties. Front Microbiol 2017; 8:285. [PMID: 28280492 PMCID: PMC5322696 DOI: 10.3389/fmicb.2017.00285] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2017] [Accepted: 02/13/2017] [Indexed: 11/22/2022] Open
Abstract
The α subunit (ATP1) is a vital component of mitochondrial complex V which counts for the majority of cellular ATP production in a living organism. Nevertheless, how the α subunit influences other cellular processes such as pathogenicity in Candida albicans remains poorly understood. To address this question, ATP1 mutant (atp1Δ/Δ) and the gene-reconstituted strain (atp1Δ/ATP1) have been constructed in this study and their pathogenicity-related traits are compared to those of wild type (WT). In a murine model of disseminated candidiasis, atp1Δ/Δ infected mice have a significantly higher survival rate and experience a lower fungal burden in tissues. In in vitro studies atp1Δ/Δ lose a capability to damage or destroy macrophages and endothelial cells. Furthermore, atp1Δ/Δ is not able to grow under either glucose-denial conditions or high H2O2 conditions, both of which are associated with the potency of the macrophages to kill C. albicans. Defects in filamentation and biofilm formation may impair the ability of atp1Δ/Δ to penetrate host cells and establish robust colonies in the host tissues. In concert with these pathogenic features, intracellular ATP levels of atp1Δ/Δ can drop to 1/3 of WT level. These results indicate that the α subunit of Complex V play important roles in C. albicans pathogenicity.
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Affiliation(s)
- Shui-Xiu Li
- The First Affiliated Hospital of Jinan UniversityGuangzhou, China; Institute of Mycology, Jinan UniversityGuangzhou, China
| | - Yan-Jun Song
- The First Affiliated Hospital of Jinan UniversityGuangzhou, China; Institute of Mycology, Jinan UniversityGuangzhou, China
| | - Yi-Shan Zhang
- The First Affiliated Hospital of Jinan UniversityGuangzhou, China; Institute of Mycology, Jinan UniversityGuangzhou, China
| | - Hao-Tian Wu
- The First Affiliated Hospital of Jinan UniversityGuangzhou, China; Institute of Mycology, Jinan UniversityGuangzhou, China
| | - Hui Guo
- The First Affiliated Hospital of Jinan UniversityGuangzhou, China; Institute of Mycology, Jinan UniversityGuangzhou, China
| | - Kun-Ju Zhu
- The First Affiliated Hospital of Jinan UniversityGuangzhou, China; Institute of Mycology, Jinan UniversityGuangzhou, China
| | - Dong-Mei Li
- Department of Microbiology and Immunology, Georgetown University Medical Center Washington, DC, USA
| | - Hong Zhang
- The First Affiliated Hospital of Jinan UniversityGuangzhou, China; Institute of Mycology, Jinan UniversityGuangzhou, China
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Abstract
Voltage-gated sodium channels are protein complexes comprised of one pore forming α subunit and two, non-pore forming, β subunits. The voltage-gated sodium channel β subunits were originally identified to function as auxiliary subunits, which modulate the gating, kinetics, and localization of the ion channel pore. Since that time, the five β subunits have been shown to play crucial roles as multifunctional signaling molecules involved in cell adhesion, cell migration, neuronal pathfinding, fasciculation, and neurite outgrowth. Here, we provide an overview of the evidence implicating the β subunits in their conducting and non-conducting roles. Mutations in the β subunit genes (SCN1B-SCN4B) have been linked to a variety of diseases. These include cancer, epilepsy, cardiac arrhythmias, sudden infant death syndrome/sudden unexpected death in epilepsy, neuropathic pain, and multiple neurodegenerative disorders. β subunits thus provide novel therapeutic targets for future drug discovery.
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Affiliation(s)
- Alexandra A Bouza
- Department of Pharmacology, University of Michigan Medical School, 2200 MSRBIII, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109-5632, USA
| | - Lori L Isom
- Department of Pharmacology, University of Michigan Medical School, 2301 MSRB III, 1150 W. Medical Center Dr., Ann Arbor, MI, 48109-5632, USA.
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Randi L, Perrone A, Maturi M, Dal Piaz F, Camerani M, Hochkoeppler A. The DnaE polymerase from Deinococcus radiodurans features RecA-dependent DNA polymerase activity. Biosci Rep 2016; 36:e00419. [PMID: 27789781 DOI: 10.1042/BSR20160364] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2016] [Revised: 10/25/2016] [Accepted: 10/27/2016] [Indexed: 12/25/2022] Open
Abstract
We report in the present study on the catalytic properties of Deinococcus radiodurans DnaE polymerase, whose DNA elongation efficiency was compared with the homologous Escherichia coli polymerase. Contrary to the latter, the deinococcal enzyme was found to be strictly dependent on RecA recombinase. We report in the present study on the catalytic properties of the Deinococcus radiodurans DNA polymerase III α subunit (αDr). The αDr enzyme was overexpressed in Escherichia coli, both in soluble form and as inclusion bodies. When purified from soluble protein extracts, αDr was found to be tightly associated with E. coli RNA polymerase, from which αDr could not be dissociated. On the contrary, when refolded from inclusion bodies, αDr was devoid of E. coli RNA polymerase and was purified to homogeneity. When assayed with different DNA substrates, αDr featured slower DNA extension rates when compared with the corresponding enzyme from E. coli (E. coli DNA Pol III, αEc), unless under high ionic strength conditions or in the presence of manganese. Further assays were performed using a ssDNA and a dsDNA, whose recombination yields a DNA substrate. Surprisingly, αDr was found to be incapable of recombination-dependent DNA polymerase activity, whereas αEc was competent in this action. However, in the presence of the RecA recombinase, αDr was able to efficiently extend the DNA substrate produced by recombination. Upon comparing the rates of RecA-dependent and RecA-independent DNA polymerase activities, we detected a significant activation of αDr by the recombinase. Conversely, the activity of αEc was found maximal under non-recombination conditions. Overall, our observations indicate a sharp contrast between the catalytic actions of αDr and αEc, with αDr more performing under recombination conditions, and αEc preferring DNA substrates whose extension does not require recombination events.
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Tsunoda F, Lamon-Fava S, Asztalos BF, Iyer LK, Richardson K, Schaefer EJ. Effects of oral eicosapentaenoic acid versus docosahexaenoic acid on human peripheral blood mononuclear cell gene expression. Atherosclerosis 2015; 241:400-8. [PMID: 26074314 DOI: 10.1016/j.atherosclerosis.2015.05.015] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Revised: 05/08/2015] [Accepted: 05/12/2015] [Indexed: 12/20/2022]
Abstract
OBJECTIVE Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) have beneficial effects on inflammation and cardiovascular disease (CVD). Our aim was to assess the effect of a six-week supplementation with either olive oil, EPA, or DHA on gene expression in peripheral blood mononuclear cells (PBMC). METHODS Subjects were sampled at baseline and six weeks after receiving either: olive oil 6.0 g/day (n = 16), EPA 1.8 g/day (n = 16), or DHA 1.8 g/day (n = 18). PBMC were subjected to gene expression analysis by microarray with key findings confirmed by quantitative real-time polymerase chain reaction (Q-PCR). RESULTS Plasma phospholipid EPA increased 3 fold in the EPA group, and DHA increased 63% in the DHA group (both p < 0.01), while no effects were observed in the olive oil group. Microarray analysis indicated that EPA but not DHA or olive oil significantly affected the gene expression in the following pathways: 1) interferon signaling, 2) receptor recognition of bacteria and viruses, 3) G protein signaling, glycolysis and glycolytic shunting, 4) S-adenosyl-l-methionine biosynthesis, and 5) cAMP-mediated signaling including cAMP responsive element protein 1 (CREB1), as well as many other individual genes including hypoxia inducible factor 1, α subunit (HIF1A). The findings for CREB1 and HIF1A were confirmed by Q-PCR analysis. CONCLUSIONS Our data indicate that EPA supplementation was associated with significant effects on gene expression involving the interferon pathway as well as down-regulation of CREB1 and HIF1A, which may relate to its beneficial effect on CVD risk reduction.
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Affiliation(s)
- Fumiyoshi Tsunoda
- Cardiovascular Nutrition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA
| | - Stefania Lamon-Fava
- Cardiovascular Nutrition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA
| | - Bela F Asztalos
- Cardiovascular Nutrition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA
| | - Lakshmanan K Iyer
- Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA, USA; Center for Neuroscience Research, Tufts University School of Medicine, Boston, MA, USA
| | - Kris Richardson
- Nutrition and Genomics Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA
| | - Ernst J Schaefer
- Cardiovascular Nutrition Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging, Tufts University, Boston, MA, USA.
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11
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Meng X, Zhang Y, Guo B, Sun H, Liu C, Liu Z. Identification of key amino acid differences contributing to neonicotinoid sensitivity between two nAChR α subunits from Pardosa pseudoannulata. Neurosci Lett 2015; 584:123-8. [PMID: 25459289 DOI: 10.1016/j.neulet.2014.10.013] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2014] [Revised: 09/26/2014] [Accepted: 10/09/2014] [Indexed: 10/24/2022]
Abstract
Chemical insecticides are still primary methods to control rice planthoppers in China, which not only cause environmental pollution, insecticide residue and insecticide resistance, but also have negative effects on natural enemies, such as Pardosa pseudoannulata (the pond wolf spider), an important predatory enemy of rice planthoppers. Neonicotinoids insecticides, such as imidacloprid and thiacloprid, are insect-selective nAChRs agonists that are used extensively in the areas of crop protection and animal health, but have hypotoxicity to P. pseudoannulata. In the present study, two nAChR α subunits, Ppα1 or Ppα8, were found to be successfully expressed with rβ2 in Xenopus oocytes, but with much different sensitivity to imidacloprid and thiacloprid on two recombinant receptors Ppα1/rβ2 and Ppα8/rβ2. Key amino acid differences were found in and between the important loops for ligand binding. In order to well understand the relationship between the amino acid differences and neonicotinoid sensitivities, different segments in Ppα8 or Ppα1 with key amino acid differences were introduced into the corresponding regions of Ppα1 or Ppα8 to construct chimeras and then co-expressed with rβ2 subunit in Xenopus oocytes. The results from chimeras of both Ppα8 and Ppα1 showed that segments Δ5, Δ6, and Δ7 contributed to neonicotinoid sensitivities directly between two receptors. Although the segment Δ4 including all loop B region had no direct influences on neonicotinoid sensitivities, it could more remarkably influence neonicotinoid sensitivities when co-introductions with Δ5, Δ6 or Δ7. So, key amino acid differences in these four segments were important to neonicotinoid sensitivities, but the difference in Δ4 was likely ignored because of its indirect effects.
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Affiliation(s)
- Xiangkun Meng
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Yixi Zhang
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Beina Guo
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Huahua Sun
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Chuanjun Liu
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China
| | - Zewen Liu
- Key Laboratory of Integrated Management of Crop Diseases and Pests (Ministry of Education), College of Plant Protection, Nanjing Agricultural University, Nanjing 210095, China.
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12
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Ren YP, Zhang MJ, Zhang T, Huang RW. Dual effects of ouabain on the regulation of proliferation and apoptosis in human umbilical vein endothelial cells: involvement of Na(+)-K(+)-ATPase α-subunits and NF-κB. Int J Clin Exp Med 2014; 7:1214-1222. [PMID: 24995076 PMCID: PMC4073737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2014] [Accepted: 04/10/2014] [Indexed: 06/03/2023]
Abstract
PURPOSE To elucidate the effect of ouabain on the regulation of proliferation and apoptosis of HUVECs and involvement of different Na(+)-K(+)-ATPase α-subunits and NF-κB. METHODS HUVECs were isolated by collagenase perfusion, and MTT assays and cell cycle analysis were performed to study proliferation. NF-κB expression and function were examined by immunohistochemical staining and western blotting. Na(+)-K(+)-ATPase activity was determined by measuring released ouabain inhibitable inorganic phosphate (Pi). The expression of different α-subunits was investigated by real RT-PCR, western blotting and cell immunofluorescence. RESULTS 0.3 nM ouabain treatment for 0.5 h triggered the proliferation of HUVECs, peaking at 1-2 h. At 1.8 nM for 0.5 h, ouabain induced an increase of cell proliferation for a short time, and then triggered a decrease after 1 h. Cell cycle analysis show that 37% of HUVECs were in G2/M phase of the cell cycle following incubation with 1.8 nM ouabain, compared with 18% with 0.3 nM ouabain. NF-κB activity was assessed by western blot analysis of IκB expression, which was significantly reduced with 0.3 nM ouabain treatment; there was no different between 1.8 nM ouabain treatment and untreated cells. Na(+)-K(+)-ATPase activity in HUVECs was markedly reduced after treatment with 0.3 nM and 1.8 nM ouabain. Real RT-PCR and western blotting indicated that Na(+)-K(+)-ATPase α1-subunit mRNA expression levels increased after 0.3 nM ouabain treatment and decreased after 1.8 nM ouabain treatment. However, α2- and α3-subunit mRNA decreased after 0.3 nM ouabain treatment and increased after 1.8 nM ouabain treatment. CONCLUSION Ouabain at different concentrations caused dual effects on proliferation and apoptosis in HUVECs.
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Affiliation(s)
- Yan-Ping Ren
- Department of Geriatric-Cardiovascular Diseases, The First Affiliated Hospital of Medical College in Xi’an Jiaotong UniversityXi’an 710061, China
| | - Ming-Juan Zhang
- Department of Cardiology, The Second Affiliated Hospital of Medical College in Xi’an Jiaotong UniversityXi’an 710004, China
| | - Ting Zhang
- Department of Geriatric-Cardiovascular Diseases, The First Affiliated Hospital of Medical College in Xi’an Jiaotong UniversityXi’an 710061, China
| | - Ruo-Wen Huang
- Department of Geriatric-Cardiovascular Diseases, The First Affiliated Hospital of Medical College in Xi’an Jiaotong UniversityXi’an 710061, China
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13
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Lara-González S, Birktoft JJ, Lawson CL. Structure of the Escherichia coli RNA polymerase alpha subunit C-terminal domain. Acta Crystallogr D Biol Crystallogr 2010; 66:806-12. [PMID: 20606261 PMCID: PMC2897699 DOI: 10.1107/s0907444910018470] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 05/18/2010] [Indexed: 11/10/2022]
Abstract
The alpha subunit C-terminal domain (alphaCTD) of RNA polymerase (RNAP) is a key element in transcription activation in Escherichia coli, possessing determinants responsible for the interaction of RNAP with DNA and with transcription factors. Here, the crystal structure of E. coli alphaCTD (alpha subunit residues 245-329) determined to 2.0 A resolution is reported. Crystals were obtained after reductive methylation of the recombinantly expressed domain. The crystals belonged to space group P2(1) and possessed both pseudo-translational symmetry and pseudo-merohedral twinning. The refined coordinate model (R factor = 0.193, R(free) = 0.236) has improved geometry compared with prior lower resolution determinations of the alphaCTD structure [Jeon et al. (1995), Science, 270, 1495-1497; Benoff et al. (2002), Science, 297, 1562-1566]. An extensive dimerization interface formed primarily by N- and C-terminal residues is also observed. The new coordinates will facilitate the improved modeling of alphaCTD-containing multi-component complexes visualized at lower resolution using X-ray crystallography and electron-microscopy reconstruction.
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Affiliation(s)
- Samuel Lara-González
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, USA
| | - Jens J. Birktoft
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, USA
| | - Catherine L. Lawson
- Department of Chemistry and Chemical Biology, Rutgers University, 610 Taylor Road, Piscataway, NJ 08854, USA
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14
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Laezza F, Gerber BR, Lou JY, Kozel MA, Hartman H, Marie Craig A, Ornitz DM, Nerbonne JM. The FGF14(F145S) mutation disrupts the interaction of FGF14 with voltage-gated Na+ channels and impairs neuronal excitability. J Neurosci 2007; 27:12033-44. [PMID: 17978045 PMCID: PMC6673376 DOI: 10.1523/jneurosci.2282-07.2007] [Citation(s) in RCA: 118] [Impact Index Per Article: 6.9] [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: 05/18/2007] [Revised: 09/10/2007] [Accepted: 09/16/2007] [Indexed: 12/19/2022] Open
Abstract
Fibroblast growth factor 14 (FGF14) belongs to the intracellular FGF homologous factor subfamily of FGF proteins (iFGFs) that are not secreted and do not activate tyrosine kinase receptors. The iFGFs, however, have been shown to interact with the pore-forming (alpha) subunits of voltage-gated Na+ (Na(v)) channels. The neurological phenotypes seen in Fgf14-/- mice and the identification of an FGF14 missense mutation (FGF14(F145S)) in a Dutch family presenting with cognitive impairment and spinocerebellar ataxia suggest links between FGF14 and neuronal functioning. Here, we demonstrate that the expression of FGF14(F145S) reduces Na(v) alpha subunit expression at the axon initial segment, attenuates Na(v) channel currents, and reduces the excitability of hippocampal neurons. In addition, and in contrast with wild-type FGF14, FGF14(F145S) does not interact directly with Na(v) channel alpha subunits. Rather, FGF14(F145S) associates with wild-type FGF14 and disrupts the interaction between wild-type FGF14 and Na(v) alpha subunits, suggesting that the mutant FGF14(F145S) protein acts as a dominant negative, interfering with the interaction between wild-type FGF14 and Na(v) channel alpha subunits and altering neuronal excitability.
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Affiliation(s)
- Fernanda Laezza
- Departments of Molecular Biology and Pharmacology and
- Anatomy and Neurobiology, Washington University Medical School, St. Louis, Missouri 63110, and
| | | | - Jun-Yang Lou
- Departments of Molecular Biology and Pharmacology and
| | | | - Hali Hartman
- Institute of Molecular Cardiology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21201
| | - Ann Marie Craig
- Anatomy and Neurobiology, Washington University Medical School, St. Louis, Missouri 63110, and
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15
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Ross W, Schneider DA, Paul BJ, Mertens A, Gourse RL. An intersubunit contact stimulating transcription initiation by E coli RNA polymerase: interaction of the alpha C-terminal domain and sigma region 4. Genes Dev 2003; 17:1293-307. [PMID: 12756230 PMCID: PMC196054 DOI: 10.1101/gad.1079403] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.1] [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] [Indexed: 11/24/2022]
Abstract
The C-terminal domain of the Escherichia coli RNA polymerase (RNAP) alpha subunit (alphaCTD) stimulates transcription initiation by interacting with upstream (UP) element DNA and a variety of transcription activators. Here we identify specific substitutions in region 4.2 of sigma 70 (sigma(70)) and in alphaCTD that decrease transcription initiation from promoters containing some, but not all, UP elements. This decrease in transcription derives from a decrease in the initial equilibrium constant for RNAP binding (K(B)). The open complexes formed by the mutant and wild-type RNAPs differ in DNAse I sensitivity at the junction of the alphaCTD and sigma DNA binding sites, correlating with the differences in transcription. A model of the DNA-alphaCTD-sigma region 4.2 ternary complex, constructed from the previously determined X-ray structures of the Thermus aquaticus sigma region 4.2-DNA complex and the E. coli alphaCTD-DNA complex, indicates that the residues identified by mutation in sigma region 4.2 and in alphaCTD are in very close proximity. Our results strongly suggest that alphaCTD, when bound to an UP element proximal subsite, contacts the RNAP sigma(70) subunit, increasing transcription. Previous data from the literature suggest that this same sigma-alphaCTD interaction also plays a role in transcription factor-mediated activation.
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Affiliation(s)
- Wilma Ross
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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16
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Kelly MD, Smith A, Banks G, Wingrove P, Whiting PW, Atack J, Seabrook GR, Maubach KA. Role of the histidine residue at position 105 in the human alpha 5 containing GABA(A) receptor on the affinity and efficacy of benzodiazepine site ligands. Br J Pharmacol 2002; 135:248-56. [PMID: 11786501 PMCID: PMC1573121 DOI: 10.1038/sj.bjp.0704459] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2001] [Revised: 09/21/2001] [Accepted: 10/25/2001] [Indexed: 11/09/2022] Open
Abstract
1. A histidine residue in the N-terminal extracellular region of alpha 1,2,3,5 subunits of the human GABA(A) receptor, which is replaced by an arginine in alpha 4 and alpha 6 subunits, is a major determinant for high affinity binding of classical benzodiazepine (BZ)-site ligands. The effect of mutating this histidine at position 105 in the alpha 5 subunit to an arginine (alpha 5H105R) on BZ-site pharmacology has been investigated using radioligand binding on HEK293 and L(tk-) cells and two electrode voltage clamp recording on Xenopus oocytes in which GABA(A) receptors of subtypes alpha 5, alpha 5H105R, alpha 4 and alpha 6 were co-expressed with beta 3 gamma 2s. 2. The classical BZs, diazepam and flunitrazepam (full agonists on the alpha 5 receptor) showed negligible affinity and therefore negligible efficacy on alpha 5H105R receptors. The beta-carbolines DMCM and beta CCE (inverse agonists on the alpha 5 receptor) retained some affinity but did not exhibit inverse agonist efficacy at alpha 5H105R receptors. Therefore, the alpha 5H105R mutation confers an alpha 4/alpha 6-like pharmacology to the classical BZs and beta-carbolines. 3. Ro15-4513, flumazenil, bretazenil and FG8094, which share a common imidazobenzodiazepine core structure, retained high affinity and were higher efficacy agonists on alpha 5H105R receptors than would be predicted from an alpha 4/alpha 6 pharmacological profile. This effect was antagonized by DMCM, which competes for the BZ-site and therefore is likely to be mediated via the BZ-site. 4. These data indicate that the conserved histidine residue in the alpha subunit is not only a key determinant in the affinity of BZ-site ligands on alpha 5 containing GABA(A) receptors, but also influences ligand efficacy.
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Affiliation(s)
- M D Kelly
- De Nova Pharmacauticals, St Andrews House, 59 St Andrews Street, Cambridge, CB2 3DD
| | - A Smith
- Neuroscience Research Centre, Merck Sharp and Dohme Research Laboratories, Harlow, Essex, CM20 2QR
| | - G Banks
- Neuroscience Research Centre, Merck Sharp and Dohme Research Laboratories, Harlow, Essex, CM20 2QR
| | - P Wingrove
- Neuroscience Research Centre, Merck Sharp and Dohme Research Laboratories, Harlow, Essex, CM20 2QR
| | - P W Whiting
- Neuroscience Research Centre, Merck Sharp and Dohme Research Laboratories, Harlow, Essex, CM20 2QR
| | - J Atack
- Neuroscience Research Centre, Merck Sharp and Dohme Research Laboratories, Harlow, Essex, CM20 2QR
| | - G R Seabrook
- Neuroscience Research Centre, Merck Sharp and Dohme Research Laboratories, Harlow, Essex, CM20 2QR
| | - K A Maubach
- Neuroscience Research Centre, Merck Sharp and Dohme Research Laboratories, Harlow, Essex, CM20 2QR
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17
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Abstract
The Escherichia coli NusA protein modulates pausing, termination, and antitermination by associating with the transcribing RNA polymerase core enzyme. NusA can be covalently cross-linked to nascent RNA within a transcription complex, but does not bind RNA on its own. We have found that deletion of the 79 carboxy-terminal amino acids of the 495-amino-acid NusA protein allows NusA to bind RNA in gel mobility shift assays. The carboxy-terminal domain (CTD) of the alpha subunit of RNA polymerase, as well as the bacteriophage lambda N gene antiterminator protein, bind to carboxy-terminal regions of NusA and enable full-length NusA to bind RNA. Binding of NusA to RNA in the presence of alpha or N involves an amino-terminal S1 homology region that is otherwise inactive in full-length NusA. The interaction of the alpha-CTD with full-length NusA stimulates termination. N may prevent termination by inducing NusA to interact with N utilization (nut) site RNA rather than RNA near the 3' end of the nascent transcript. Sequence analysis showed that the alpha-CTD contains a modified helix-hairpin-helix motif (HhH), which is also conserved in the carboxy-terminal regions of some eubacterial NusA proteins. These HhH motifs may mediate protein-protein interactions in NusA and the alpha-CTD.
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Affiliation(s)
- T F Mah
- Banting and Best Department of Medical Research and Department of Molecular and Medical Genetics, University of Toronto, Toronto, Ontario M5G 1L6, Canada
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18
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Ueno S, Lin A, Nikolaeva N, Trudell JR, Mihic SJ, Harris RA, Harrison NL. Tryptophan scanning mutagenesis in TM2 of the GABA(A) receptor alpha subunit: effects on channel gating and regulation by ethanol. Br J Pharmacol 2000; 131:296-302. [PMID: 10991923 PMCID: PMC1572307 DOI: 10.1038/sj.bjp.0703504] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.6] [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] [Indexed: 11/09/2022] Open
Abstract
1. Each residue in the second transmembrane segment (TM2) of the human GABA(A) receptor alpha(2) subunit was individually mutated to tryptophan. The wild-type or mutant alpha(2) subunits were expressed with the wild-type human GABA(A) receptor beta(2) subunit in Xenopus oocytes, and the effects of these mutations were investigated using two-electrode voltage-clamp recording. 2. Four mutations (V257W, T262W, T265W and S270W) produced receptors which were active in the absence of agonist, and this spontaneous open channel activity was blocked by both picrotoxin and bicuculline, except in the alpha(2)(V257W)beta(2) mutant receptor, which was not sensitive to picrotoxin. 3. Six mutations (V257W, V260W, T262W, T267W, S270W and A273W) enhanced the agonist sensitivity of the receptor, by 10 - 100 times compared with the wild-type alpha(2)beta(2) receptor. Other mutations (T261W, V263W, L269W, I271W and S272W) had little or no effect on the apparent affinity of the receptor to GABA. Eight of the tryptophan mutations (R255, T256, F258, G259, L264, T265, M266 or T268) resulted in undetectable GABA-induced currents. 4. The S270W mutation eliminated potentiation of GABA by ethanol, whereas T261W markedly increased the action of ethanol. The T262W mutation produced direct activation (10% of maximal GABA response) by ethanol in the absence of GABA, while other mutations did not alter the action of ethanol significantly. 5. These results are consistent with a unique role for S270 in the action of ethanol within the TM2 region, and with models of GABA(A) receptor channel function, in which specific residues within TM2 are critical for the regulation of channel gating (S270, L264), while other residues (L269, I271 and S272) have little effect on these functions and may be non-critical structural residues.
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Affiliation(s)
- Susumu Ueno
- Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, 2500 Speedway, MBB 1.124, Austin, Texas, TX 78712, U.S.A
- Department of Pharmacology, University of Occupational and Environmental Health, School of Medicine, Kitakyushu 807-8555, Japan
| | - Audrey Lin
- Department of Anesthesia and Critical Care, University of Chicago, Chicago, Illinois, IL 60637, U.S.A
- Department of Pediatrics, Yale University School of Medicine, New Haven, Connecticut, CT 06510, U.S.A
| | - Natalia Nikolaeva
- Department of Anesthesia and Critical Care, University of Chicago, Chicago, Illinois, IL 60637, U.S.A
- Department of Neurobiology, Pharmacology and Physiology, University of Chicago, Chicago, Illinois, IL 60637, U.S.A
| | - James R Trudell
- Department of Anesthesia and Program for Molecular and Genetic Medicine, Stanford University, Stanford, California, CA 94305, U.S.A
| | - S John Mihic
- Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, 2500 Speedway, MBB 1.124, Austin, Texas, TX 78712, U.S.A
- Department of Physiology & Pharmacology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, NC 27157, U.S.A
| | - R Adron Harris
- Waggoner Center for Alcohol and Addiction Research, University of Texas at Austin, 2500 Speedway, MBB 1.124, Austin, Texas, TX 78712, U.S.A
- Author for correspondence:
| | - Neil L Harrison
- Department of Anesthesiology, A-1050, Weill Medical College of Cornell University, New York, NY 10021, U.S.A
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19
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Okada M, Onodera K, Van Renterghem C, Sieghart W, Takahashi T. Functional correlation of GABA(A) receptor alpha subunits expression with the properties of IPSCs in the developing thalamus. J Neurosci 2000; 20:2202-8. [PMID: 10704495 PMCID: PMC6772493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
GABA(A) receptor alpha1 and alpha2 subunits are expressed differentially with ontogenic period in the brain, but their functional roles are not known. We have recorded GABA(A) receptor-mediated IPSCs from laterodorsal (LD) thalamic relay neurons in slices of rat brain at various postnatal ages and found that decay times of evoked IPSCs and spontaneous miniature IPSCs undergo progressive shortening during the first postnatal month. With a similar time course, expression of transcripts and proteins of GABA(A) receptor alpha2 subunit in LD thalamic region declined, being replaced by those of alpha1 subunit. To further address the causal relationship between alpha subunits and IPSC decay time kinetics, we have overexpressed GABA(A) receptor alpha1 subunit together with green fluorescent protein in LD thalamic neurons in organotypic culture using recombinant Sindbis virus vectors. Miniature IPSCs recorded from the LD thalamic neurons overexpressed with alpha1 subunit had significantly faster decay time compared with control expressed with beta-galactosidase. We conclude that the alpha2-to-alpha1 subunit switch underlies the developmental speeding in the decay time of GABAergic IPSCs.
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Affiliation(s)
- M Okada
- Department of Neurophysiology, University of Tokyo Faculty of Medicine, Tokyo 113-0033, Japan
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20
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Taylor PM, Connolly CN, Kittler JT, Gorrie GH, Hosie A, Smart TG, Moss SJ. Identification of residues within GABA(A) receptor alpha subunits that mediate specific assembly with receptor beta subunits. J Neurosci 2000; 20:1297-306. [PMID: 10662819 PMCID: PMC6772372] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
GABA(A) receptors can be constructed from a range of differing subunit isoforms: alpha, beta, gamma, delta, and epsilon. Expression studies have revealed that production of GABA-gated channels is achieved after coexpression of alpha and beta subunits. The expression of a gamma subunit isoform is essential to confer benzodiazepine sensitivity on the expressed receptor. However, how the specificity of subunit interactions is controlled during receptor assembly remains unknown. Here we demonstrate that residues 58-67 within alpha subunit isoforms are important in the assembly of receptors comprised of alphabeta and alphabetagamma subunits. Deletion of these residues from the alpha1 or alpha6 subunits results in retention of either alpha subunit isoform in the endoplasmic reticulum on coexpression with the beta3, or beta3 and gamma2 subunits. Immunoprecipitation revealed that residues 58-67 mediated oligomerization of the alpha1 and beta3 subunits, but were without affect on the production of alpha/gamma complexes. Within this domain, glutamine 67 was of central importance in mediating the production of functional alpha1beta3 receptors. Mutation of this residue resulted in a drastic decrease in the cell surface expression of alpha1beta3 receptors and the resulting expression of beta3 homomers. Sucrose density gradient centrifugation revealed that this residue was important for the production of a 9S alpha1beta3 complex representing functional GABA(A) receptors. Therefore, our studies detail residues that specify GABA(A) receptor alphabeta subunit interactions. This domain, which is conserved in all alpha subunit isoforms, will therefore play a critical role in the assembly of GABA(A) receptors composed of alphabeta and alphabetagamma subunits.
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Affiliation(s)
- P M Taylor
- The Medical Research Council Laboratory of Molecular Cell Biology, Department of Pharmacology, University College, London WC1E 6BT, United Kingdom
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21
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Tan Q, Linask KL, Ebright RH, Woychik NA. Activation mutants in yeast RNA polymerase II subunit RPB3 provide evidence for a structurally conserved surface required for activation in eukaryotes and bacteria. Genes Dev 2000; 14:339-48. [PMID: 10673505 PMCID: PMC316356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 12/01/1999] [Accepted: 12/14/1999] [Indexed: 02/15/2023]
Abstract
We have identified a mutant in RPB3, the third-largest subunit of yeast RNA polymerase II, that is defective in activator-dependent transcription, but not defective in activator-independent, basal transcription. The mutant contains two amino-acid substitutions, C92R and A159G, that are both required for pronounced defects in activator-dependent transcription. Synthetic enhancement of phenotypes of C92R and A159G, and of several other pairs of substitutions, is consistent with a functional relationship between residues 92-95 and 159-161. Homology modeling of RPB3 on the basis of the crystallographic structure of alphaNTD indicates that residues 92-95 and 159-162 are likely to be adjacent within the structure of RPB3. In addition, homology modeling indicates that the location of residues 159-162 within RPB3 corresponds to the location of an activation target within alphaNTD (the target of activating region 2 of catabolite activator protein, an activation target involved in a protein-protein interaction that facilitates isomerization of the RNA polymerase promoter closed complex to the RNA polymerase promoter open complex). The apparent finding of a conserved surface required for activation in eukaryotes and bacteria raises the possibility of conserved mechanisms of activation in eukaryotes and bacteria.
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Affiliation(s)
- Q Tan
- University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School, Department of Molecular Genetics and Microbiology, Piscataway, New Jersey 08854, USA
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22
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Boileau AJ, Czajkowski C. Identification of transduction elements for benzodiazepine modulation of the GABA(A) receptor: three residues are required for allosteric coupling. J Neurosci 1999; 19:10213-20. [PMID: 10575018 PMCID: PMC6782401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/14/2023] Open
Abstract
Modulation of GABA(A) receptors by benzodiazepines (BZDs) is believed to involve two distinct steps: a recognition step in which BZDs bind and a conformational transition step in which the affinity of the receptor for GABA changes. Previously, using gamma(2)/alpha(1) chimeric subunits (chi), we demonstrated that although the N-terminal 167 gamma(2) amino acid residues confer high-affinity BZD binding, other gamma(2) domains couple BZD binding to potentiation of the GABA-mediated Cl(-) current (I(GABA)). To determine which gamma(2) regions couple binding to potentiation, we generated chis with longer N-terminal gamma(2) segments for voltage-clamp experiments in Xenopus oocytes. Chimeras containing greater than the N-terminal 167 gamma(2) residues showed incremental gains in maximal potentiation for diazepam enhancement of I(GABA). Residues in gamma(2)199-236, gamma(2)224-236 (pre-M1), and particularly gamma(2)257-297 (M2 and surrounding loops) are important for BZD potentiation. For several positive BZD modulators tested, the same regions restored potentiation of I(GABA). In contrast, beta-carboline inverse-agonism was unaltered in chimeric receptors, suggesting that structural determinants for positive and negative BZD allosteric modulation are different. Dissection of the gamma(2)257-297 domain revealed that three residues in concert, gamma(2)T281, gamma(2)I282 (M2 channel vestibule), and gamma(2)S291 (M2-M3 loop) are necessary to impart full BZD potentiation to chimeric receptors. Thus, these residues participate in coupling distant BZD-binding events to conformational changes in the GABA(A) receptor. The location of these novel residues provides insight into the mechanisms underlying allosteric coupling for other members of the ligand-gated ion channel superfamily.
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Affiliation(s)
- A J Boileau
- Department of Physiology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Estrem ST, Ross W, Gaal T, Chen ZW, Niu W, Ebright RH, Gourse RL. Bacterial promoter architecture: subsite structure of UP elements and interactions with the carboxy-terminal domain of the RNA polymerase alpha subunit. Genes Dev 1999; 13:2134-47. [PMID: 10465790 PMCID: PMC316962 DOI: 10.1101/gad.13.16.2134] [Citation(s) in RCA: 156] [Impact Index Per Article: 6.2] [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] [Indexed: 11/25/2022]
Abstract
We demonstrate here that the previously described bacterial promoter upstream element (UP element) consists of two distinct subsites, each of which, by itself, can bind the RNA polymerase holoenzyme alpha subunit carboxy-terminal domain (RNAP alphaCTD) and stimulate transcription. Using binding-site-selection experiments, we identify the consensus sequence for each subsite. The selected proximal subsites (positions -46 to -38; consensus 5'-AAAAAARNR-3') stimulate transcription up to 170-fold, and the selected distal subsites (positions -57 to -47; consensus 5'-AWWWWWTTTTT-3') stimulate transcription up to 16-fold. RNAP has subunit composition alpha(2)betabeta'sigma and thus contains two copies of alphaCTD. Experiments with RNAP derivatives containing only one copy of alphaCTD indicate, in contrast to a previous report, that the two alphaCTDs function interchangeably with respect to UP element recognition. Furthermore, function of the consensus proximal subsite requires only one copy of alphaCTD, whereas function of the consensus distal subsite requires both copies of alphaCTD. We propose that each subsite constitutes a binding site for a copy of alphaCTD, and that binding of an alphaCTD to the proximal subsite region (through specific interactions with a consensus proximal subsite or through nonspecific interactions with a nonconsensus proximal subsite) is a prerequisite for binding of the other alphaCTD to the distal subsite.
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Affiliation(s)
- S T Estrem
- Department of Bacteriology, University of Wisconsin, Madison, Wisconsin 53706 USA
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