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Fan W, Xu Y, He X, Luo P, Zhu J, Li J, Wang R, Yuan Q, Wu K, Hu W, Zhao Y, Xu S, Cheng X, Wang Y, Xu HE, Zhuang Y. Molecular basis for the activation of PAF receptor by PAF. Cell Rep 2024; 43:114422. [PMID: 38943642 DOI: 10.1016/j.celrep.2024.114422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2024] [Revised: 05/07/2024] [Accepted: 06/14/2024] [Indexed: 07/01/2024] Open
Abstract
Platelet-activating factor (PAF) is a potent phospholipid mediator crucial in multiple inflammatory and immune responses through binding and activating the PAF receptor (PAFR). However, drug development targeting the PAFR has been limited, partly due to an incomplete understanding of its activation mechanism. Here, we present a 2.9-Å structure of the PAF-bound PAFR-Gi complex. Structural and mutagenesis analyses unveil a specific binding mode of PAF, with the choline head forming cation-π interactions within PAFR hydrophobic pocket, while the alkyl tail penetrates deeply into an aromatic cleft between TM4 and TM5. Binding of PAF modulates conformational changes in key motifs of PAFR, triggering the outward movement of TM6, TM7, and helix 8 for G protein coupling. Molecular dynamics simulation suggests a membrane-side pathway for PAF entry into PAFR via the TM4-TM5 cavity. By providing molecular insights into PAFR signaling, this work contributes a foundation for developing therapeutic interventions targeting PAF signal axis.
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Affiliation(s)
- Wenjia Fan
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing 210046, China; The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Youwei Xu
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Xinheng He
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Ping Luo
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Jingpeng Zhu
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Junrui Li
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Ruolan Wang
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Qingning Yuan
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; The Shanghai Advanced Electron Microscope Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Kai Wu
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; The Shanghai Advanced Electron Microscope Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Wen Hu
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; The Shanghai Advanced Electron Microscope Center, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Yuxi Zhao
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing 210046, China; The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Shiqi Xu
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China
| | - Xi Cheng
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yue Wang
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China.
| | - H Eric Xu
- School of Chinese Materia Medica, Nanjing University of Chinese Medicine, Nanjing 210046, China; The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Youwen Zhuang
- The State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, China; Medicinal Bioinformatics Center, School of Medicine, Shanghai Jiao Tong University, Shanghai 200025, China.
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Coelho FS, Oliveira MM, Vieira DP, Torres PHM, Moreira ICF, Martins-Duarte ES, Gonçalves IC, Cabanelas A, Pascutti PG, Fragoso SP, Lopes AH. A novel receptor for platelet-activating factor and lysophosphatidylcholine in Trypanosoma cruzi. Mol Microbiol 2021; 116:890-908. [PMID: 34184334 DOI: 10.1111/mmi.14778] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 06/24/2021] [Accepted: 06/26/2021] [Indexed: 01/12/2023]
Abstract
The lipid mediators, platelet-activating factor (PAF) and lysophosphatidylcholine (LPC), play relevant pathophysiological roles in Trypanosoma cruzi infection. Several species of LPC, including C18:1 LPC, which mimics the effects of PAF, are synthesized by T. cruzi. The present study identified a receptor in T. cruzi, which was predicted to bind to PAF, and found it to be homologous to members of the progestin and adiponectin family of receptors (PAQRs). We constructed a three-dimensional model of the T. cruzi PAQR (TcPAQR) and performed molecular docking to predict the interactions of the TcPAQR model with C16:0 PAF and C18:1 LPC. We knocked out T. cruzi PAQR (TcPAQR) gene and confirmed the identity of the expressed protein through immunoblotting and immunofluorescence assays using an anti-human PAQR antibody. Wild-type and knockout (KO) parasites were also used to investigate the in vitro cell differentiation and interactions with peritoneal mouse macrophages; TcPAQR KO parasites were unable to react to C16:0 PAF or C18:1 LPC. Our data are highly suggestive that PAF and LPC act through TcPAQR in T. cruzi, triggering its cellular differentiation and ability to infect macrophages.
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Affiliation(s)
- Felipe S Coelho
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Mauricio M Oliveira
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | | | - Pedro H M Torres
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Isabel C F Moreira
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Erica S Martins-Duarte
- Departmento de Parasitologia, Universidade Federal de Minas Gerais, Belo Horizonte, Brazil
| | - Inês C Gonçalves
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Adriana Cabanelas
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Pedro G Pascutti
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Stenio P Fragoso
- Laboratório de Biologia Molecular e Sistêmica de Tripanossomatídeos, Instituto Carlos Chagas, Curitiba, Brazil
| | - Angela H Lopes
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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Rozo-Lugo C, Cuca-Suárez LE, Schmidt TJ, Coy-Barrera E. Tetrahydrobenzofuran-6(2 H)-one Neolignans from Ocotea heterochroma: Their Platelet Activating Factor (PAF) Antagonistic Activity and in Silico Insights into the PAF Receptor Binding Mode. JOURNAL OF NATURAL PRODUCTS 2018; 81:1968-1975. [PMID: 30188730 DOI: 10.1021/acs.jnatprod.8b00189] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Three new tetrahydrobenzofuran-6(2 H)-one-type neolignans, heterochromins A-C (1-3), along with a bicyclo[3.2.1]octane neolignan, cinerin C (4), were isolated from an ethanol extract from the leaves of Ocotea heterochroma, a native plant growing in the Colombo-Ecuadorian region of the Andes. The chemical structures of 1-3 were elucidated by spectroscopic methods. The platelet activating factor (PAF) antagonistic activity was tested in vitro for these compounds. Additionally, their binding mode to the PAF receptor was studied by molecular docking and molecular dynamics simulations in order to rationalize such activity. Heterochromin A (1) was found to be a potent PAF antagonist with a favorable molecular profile for interacting with the PAF receptor binding site.
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Affiliation(s)
- Catalina Rozo-Lugo
- Laboratorio de Investigación en Productos Naturales Vegetales, Departamento de Química , Universidad Nacional de Colombia, Ciudad Universitaria , 111321 , Bogotá D.C. , Colombia
- Laboratorio de Química Bioorgánica, Departamento de Química, Facultad de Ciencias Básicas y Aplicadas , Universidad Militar Nueva Granada , 250247 , Cajicá , Colombia
| | - Luis Enrique Cuca-Suárez
- Laboratorio de Investigación en Productos Naturales Vegetales, Departamento de Química , Universidad Nacional de Colombia, Ciudad Universitaria , 111321 , Bogotá D.C. , Colombia
| | - Thomas J Schmidt
- Institut für Pharmazeutische Biologie und Phytochemie (IPBP) , University of Münster, PharmaCampus , Corrensstraße 48 , D-48149 , Münster , Germany
| | - Ericsson Coy-Barrera
- Laboratorio de Química Bioorgánica, Departamento de Química, Facultad de Ciencias Básicas y Aplicadas , Universidad Militar Nueva Granada , 250247 , Cajicá , Colombia
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4
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Hyland IK, O'Toole RF, Smith JA, Bissember AC. Progress in the Development of Platelet-Activating Factor Receptor (PAFr) Antagonists and Applications in the Treatment of Inflammatory Diseases. ChemMedChem 2018; 13:1873-1884. [DOI: 10.1002/cmdc.201800401] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2018] [Revised: 07/08/2018] [Indexed: 11/10/2022]
Affiliation(s)
- Isabel K. Hyland
- School of Natural Sciences Chemistry; University of Tasmania; Hobart Australia
| | | | - Jason A. Smith
- School of Natural Sciences Chemistry; University of Tasmania; Hobart Australia
| | - Alex C. Bissember
- School of Natural Sciences Chemistry; University of Tasmania; Hobart Australia
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Jasamai M, Jalil J, Jantan I. Molecular docking study on platelet-activating factor antagonistic activity of bioactive compounds isolated from Guttiferae andArdisiaspecies. Nat Prod Res 2014; 29:1055-8. [DOI: 10.1080/14786419.2014.971317] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Caboni P, Liori B, Kumar A, Santoru ML, Asthana S, Pieroni E, Fais A, Era B, Cacace E, Ruggiero V, Atzori L. Metabolomics analysis and modeling suggest a lysophosphocholines-PAF receptor interaction in fibromyalgia. PLoS One 2014; 9:e107626. [PMID: 25238064 PMCID: PMC4169547 DOI: 10.1371/journal.pone.0107626] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2014] [Accepted: 08/13/2014] [Indexed: 12/18/2022] Open
Abstract
Fibromyalgia Syndrome (FMS) is a chronic disease characterized by widespread pain, and difficult to diagnose and treat. We analyzed the plasma metabolic profile of patients with FMS by using a metabolomics approach combining Liquid Chromatography-Quadrupole-Time Of Flight/Mass Spectrometry (LC-Q-TOF/MS) with multivariate statistical analysis, aiming to discriminate patients and controls. LC-Q-TOF/MS analysis of plasma (FMS patients: n = 22 and controls: n = 21) identified many lipid compounds, mainly lysophosphocholines (lysoPCs), phosphocholines and ceramides. Multivariate statistical analysis was performed to identify the discriminating metabolites. A protein docking and molecular dynamic (MD) study was then performed, using the most discriminating lysoPCs, to validate the binding to Platelet Activating Factor (1-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) Receptor (PAFr). Discriminating metabolites between FMS patients and controls were identified as 1-tetradecanoyl-sn-glycero-3-phosphocholine [PC(14∶0/0∶0)] and 1-hexadecanoyl-sn-glycero-3-phosphocholine [PC(16∶0/0∶0)]. MD and docking indicate that the ligands investigated have similar potentialities to activate the PAFr receptor. The application of a metabolomic approach discriminated FMS patients from controls, with an over-representation of PC(14∶0/0∶0) and PC(16∶0/0∶0) compounds in the metabolic profiles. These results and the modeling of metabolite-PAFr interaction, allowed us to hypothesize that lipids oxidative fragmentation might generate lysoPCs in abundance, that in turn will act as PAF-like bioactivators. Overall results suggest disease biomarkers and potential therapeutical targets for FMS.
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Affiliation(s)
- Pierluigi Caboni
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Barbara Liori
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Amit Kumar
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
- Biomedicine Department, CRS4, Cagliari, Italy
| | | | - Shailendra Asthana
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
| | | | - Antonella Fais
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Benedetta Era
- Department of Life and Environmental Sciences, University of Cagliari, Cagliari, Italy
| | - Enrico Cacace
- Department of Medical Sciences “Mario Aresu”, University of Cagliari, Cagliari, Italy
| | - Valeria Ruggiero
- Department of Medical Sciences “Mario Aresu”, University of Cagliari, Cagliari, Italy
| | - Luigi Atzori
- Department of Biomedical Sciences, University of Cagliari, Cagliari, Italy
- * E-mail:
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Gazos-Lopes F, Oliveira MM, Hoelz LVB, Vieira DP, Marques AF, Nakayasu ES, Gomes MT, Salloum NG, Pascutti PG, Souto-Padrón T, Monteiro RQ, Lopes AH, Almeida IC. Structural and functional analysis of a platelet-activating lysophosphatidylcholine of Trypanosoma cruzi. PLoS Negl Trop Dis 2014; 8:e3077. [PMID: 25101628 PMCID: PMC4125143 DOI: 10.1371/journal.pntd.0003077] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2013] [Accepted: 06/13/2014] [Indexed: 12/15/2022] Open
Abstract
Background Trypanosoma cruzi is the causative agent of the life-threatening Chagas disease, in which increased platelet aggregation related to myocarditis is observed. Platelet-activating factor (PAF) is a potent intercellular lipid mediator and second messenger that exerts its activity through a PAF-specific receptor (PAFR). Previous data from our group suggested that T. cruzi synthesizes a phospholipid with PAF-like activity. The structure of T. cruzi PAF-like molecule, however, remains elusive. Methodology/Principal findings Here, we have purified and structurally characterized the putative T. cruzi PAF-like molecule by electrospray ionization-tandem mass spectrometry (ESI-MS/MS). Our ESI-MS/MS data demonstrated that the T. cruzi PAF-like molecule is actually a lysophosphatidylcholine (LPC), namely sn-1 C18:1(delta 9)-LPC. Similar to PAF, the platelet-aggregating activity of C18:1-LPC was abrogated by the PAFR antagonist, WEB 2086. Other major LPC species, i.e., C16:0-, C18:0-, and C18:2-LPC, were also characterized in all T. cruzi stages. These LPC species, however, failed to induce platelet aggregation. Quantification of T. cruzi LPC species by ESI-MS revealed that intracellular amastigote and trypomastigote forms have much higher levels of C18:1-LPC than epimastigote and metacyclic trypomastigote forms. C18:1-LPC was also found to be secreted by the parasite in extracellular vesicles (EV) and an EV-free fraction. A three-dimensional model of PAFR was constructed and a molecular docking study was performed to predict the interactions between the PAFR model and PAF, and each LPC species. Molecular docking data suggested that, contrary to other LPC species analyzed, C18:1-LPC is predicted to interact with the PAFR model in a fashion similar to PAF. Conclusions/Significance Taken together, our data indicate that T. cruzi synthesizes a bioactive C18:1-LPC, which aggregates platelets via PAFR. We propose that C18:1-LPC might be an important lipid mediator in the progression of Chagas disease and its biosynthesis could eventually be exploited as a potential target for new therapeutic interventions. Chagas disease, caused by the parasite Trypanosoma cruzi, was exclusively confined to Latin America but it has recently spread to other regions of the world. Chagas disease affects 8–10 million people and kills thousands of them every year. Lysophosphatidylcholine (LPC) is a major bioactive phospholipid of human plasma low-density lipoproteins (LDL). Platelet-activating factor (PAF) is a phospholipid similar to LPC and a potent intercellular mediator. Both PAF and LPC have been reported to act on mammalian cells through PAF receptor (PAFR). Previous data from our group suggested that T. cruzi produces a phospholipid with PAF activity. Here, we describe the structural and functional analysis of different species of LPC from T. cruzi, including a LPC with a fatty acid chain of 18 carbon atoms and one double bond (C18:1-LPC). We also show that C18:1-LPC is able to induce rabbit platelet aggregation, which is abrogated by a PAFR antagonist. In addition, a three-dimensional model of human PAFR was constructed. Contrary to other T. cruzi LPC molecules, C18:1-LPC is predicted to interact with the PAFR model in a fashion similar to PAF. Further studies are needed to validate the biosynthesis of T. cruzi C18:1-LPC as a potential drug target in Chagas disease.
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Affiliation(s)
- Felipe Gazos-Lopes
- The Border Biomedical Research Center, Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, Texas, United States of America
| | - Mauricio M. Oliveira
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Ciências da Saúde, Bloco I, Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Lucas V. B. Hoelz
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Ciências da Saúde, Bloco G, Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Danielle P. Vieira
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Ciências da Saúde, Bloco I, Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Alexandre F. Marques
- The Border Biomedical Research Center, Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, Texas, United States of America
- Universidade Federal de Minas Gerais, Instituto de Ciências Biológicas, Departamento de Parasitologia, Pampulha, Belo Horizonte, Minas Gerais, Brazil
| | - Ernesto S. Nakayasu
- The Border Biomedical Research Center, Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, Texas, United States of America
| | - Marta T. Gomes
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Ciências da Saúde, Bloco I, Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brazil
- Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Ciências da Saúde, Bloco H, Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Nasim G. Salloum
- The Border Biomedical Research Center, Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, Texas, United States of America
| | - Pedro G. Pascutti
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Ciências da Saúde, Bloco G, Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Thaïs Souto-Padrón
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Ciências da Saúde, Bloco I, Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Robson Q. Monteiro
- Instituto de Bioquímica Médica, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Ciências da Saúde, Bloco H, Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brazil
| | - Angela H. Lopes
- Instituto de Microbiologia Paulo de Góes, Universidade Federal do Rio de Janeiro, Cidade Universitária, Centro de Ciências da Saúde, Bloco I, Ilha do Fundão, Rio de Janeiro, Rio de Janeiro, Brazil
- * E-mail: (AHL); (ICA)
| | - Igor C. Almeida
- The Border Biomedical Research Center, Department of Biological Sciences, University of Texas at El Paso (UTEP), El Paso, Texas, United States of America
- * E-mail: (AHL); (ICA)
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Saravanan K, Krishnaswamy S. Analysis of dihedral angle preferences for alanine and glycine residues in alpha and beta transmembrane regions. J Biomol Struct Dyn 2014; 33:552-62. [DOI: 10.1080/07391102.2014.895678] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
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Fenelon JC, Shaw G, O'Neill C, Frankenberg S, Renfree MB. Paf receptor expression in the marsupial embryo and endometrium during embryonic diapause. Reproduction 2014; 147:21-31. [DOI: 10.1530/rep-13-0140] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The control of reactivation from embryonic diapause in the tammar wallaby (Macropus eugenii) involves sequential activation of the corpus luteum, secretion of progesterone that stimulates endometrial secretion and subsequent changes in the uterine environment that activate the embryo. However, the precise signals between the endometrium and the blastocyst are currently unknown. In eutherians, both the phospholipid Paf and its receptor, platelet-activating factor receptor (PTAFR), are present in the embryo and the endometrium. In the tammar, endometrial Paf releasein vitroincreases around the time of the early progesterone pulse that occurs around the time of reactivation, but whether Paf can reactivate the blastocyst is unknown. We cloned and characterised the expression of PTAFR in the tammar embryo and endometrium at entry into embryonic diapause, during its maintenance and after reactivation. Tammar PTAFR sequence and protein were highly conserved with mammalian orthologues. In the endometrium, PTAFR was expressed at a constant level in the glandular epithelium across all stages and in the luminal epithelium during both diapause and reactivation. Thus, the presence of the receptor appears not to be a limiting factor for Paf actions in the endometrium. However, the low levels of PTAFR in the embryo during diapause, together with its up-regulation and subsequent internalisation at reactivation, supports earlier results suggesting that endometrial Paf could be involved in reactivation of the tammar blastocyst from embryonic diapause.
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10
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Tsoupras AB, Papakyriakou A, Demopoulos CA, Philippopoulos AI. Synthesis, biochemical evaluation and molecular modeling studies of novel rhodium complexes with nanomolar activity against Platelet Activating Factor. J Inorg Biochem 2012; 120:63-73. [PMID: 23318288 DOI: 10.1016/j.jinorgbio.2012.12.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Revised: 12/10/2012] [Accepted: 12/10/2012] [Indexed: 12/18/2022]
Abstract
Two square planar Rh(I) organometallic complexes namely [Rh(L(1))(cod)]Cl (cod = cycloocta-1,5-diene, L(1)=2,2'-pyridylquinoxaline (1-Cl), [Rh(L1)(cod)](NO3) (1-NO(3)) and a series of novel octahedral rhodium(III) complexes of the general formulae mer-[Rh(L(1))Cl(3)(MeOH)] (2) and cis-[Rh(L(2))(2)Cl(2)]Cl (L(2)=4 carboxy 2 (2' pyridyl)quinoline (3), L(3)=2,2' bipyridine 4,4' dicarboxylic acid (4) were synthesized and characterized spectroscopically. All the synthesized compounds including the previously prepared cis-[Rh(L(1))(2)Cl(2)]Cl complex (5) were biologically evaluated as potential inhibitors of the Platelet Activation Factor (PAF) and thrombin induced aggregation. In particular compounds 1-Cl and 1-NO(3) were found to be strong inhibitors of PAF with IC(50) values in the range of 16 nM and 15 nM rendering them good candidates for further investigation. Their potency is comparable to that of the widely used PAF receptor antagonists WEB2170, BN52021, and Rupatadine (IC(50) of 20, 30 and 260 nM respectively). Molecular docking calculations suggest that 1-Cl, 1-NO3 and 2 can be accommodated within the ligand-binding site of PAF receptor and block the activity of PAF. On the other hand, the octahedral rhodium(III) complexes 3-5 that cannot fit the ligand-binding domain, could potentially exhibit their activity at the extracellular domain of the receptor.
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Affiliation(s)
- Alexandros B Tsoupras
- Laboratory of Biochemistry, Faculty of Chemistry, National and Kapodistrian University of Athens, Athens 15771, Greece
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11
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Cöster M, Wittkopf D, Kreuchwig A, Kleinau G, Thor D, Krause G, Schöneberg T. Using ortholog sequence data to predict the functional relevance of mutations in G‐protein‐coupled receptors. FASEB J 2012; 26:3273-81. [DOI: 10.1096/fj.12-203737] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Maxi Cöster
- Molecular Biochemistry, Institute of Biochemistry, Medical FacultyUniversity of Leipzig Leipzig Germany
| | - Doreen Wittkopf
- Molecular Biochemistry, Institute of Biochemistry, Medical FacultyUniversity of Leipzig Leipzig Germany
| | | | - Gunnar Kleinau
- Institute of Experimental Pediatric EndocrinologyCharité Universitätsmedizin Berlin Berlin Germany
| | - Doreen Thor
- Molecular Biochemistry, Institute of Biochemistry, Medical FacultyUniversity of Leipzig Leipzig Germany
| | - Gerd Krause
- Leibniz Institute for Molecular Pharmacology Berlin Germany
| | - Torsten Schöneberg
- Molecular Biochemistry, Institute of Biochemistry, Medical FacultyUniversity of Leipzig Leipzig Germany
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Abstract
G protein-coupled receptors (GPCRs) comprise a large class of transmembrane proteins that play critical roles in both normal physiology and pathophysiology. These critical roles offer targets for therapeutic intervention, as exemplified by the substantial fraction of current pharmaceutical agents that target members of this family. Tremendous contributions to our understanding of GPCR structure and dynamics have come from both indirect and direct structural characterization techniques. Key features of GPCR conformations derived from both types of characterization techniques are reviewed.
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Affiliation(s)
- Abby L. Parrill
- Department of Chemistry, The University of Memphis, Memphis, TN 38152, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-901-678-2638; Fax: +1-901-678-3447
| | - Debra L. Bautista
- Christian Brothers High School, 5900 Walnut Grove Road, Memphis, TN 38120, USA; E-Mail: (D.L.B.)
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13
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Bestebroer J, de Haas CJ, van Strijp JA. How microorganisms avoid phagocyte attraction. FEMS Microbiol Rev 2010; 34:395-414. [DOI: 10.1111/j.1574-6976.2009.00202.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
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14
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Hirota N, Yasuda D, Hashidate T, Yamamoto T, Yamaguchi S, Nagamune T, Nagase T, Shimizu T, Nakamura M. Amino acid residues critical for endoplasmic reticulum export and trafficking of platelet-activating factor receptor. J Biol Chem 2009; 285:5931-40. [PMID: 20007715 DOI: 10.1074/jbc.m109.066282] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Several residues are conserved in the transmembrane domains (TMs) of G-protein coupled receptors. Here we demonstrate that a conserved proline, Pro(247), in TM6 of platelet-activating factor receptor (PAFR) is required for endoplasmic reticulum (ER) export and trafficking after agonist-induced internalization. Alanine-substituted mutants of the conserved residues of PAFRs, including P247A, were retained in the ER. Because a PAFR antagonist, Y-24180, acted as a pharmacological chaperone to rescue ER retention, this retention is due to misfolding of PAFR. Methylcarbamyl (mc)-PAF, a PAFR agonist, did not increase the cell surface expression of P247A, even though another ER-retained mutant, D63A, was effectively trafficked. Signaling and accumulation of the receptors in the early endosomes were observed in the mc-PAF-treated P247A-expressing cells, suggesting that P247A was trafficked to the cell surface by mc-PAF, and thereafter disappeared from the surface due to aberrant trafficking, e.g. enhanced internalization, deficiency in recycling, and/or accelerated degradation. The aberrant trafficking was confirmed with a sortase-A-mediated method for labeling cell surface proteins. These results demonstrate that the conserved proline in TM6 is crucial for intracellular trafficking of PAFR.
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Affiliation(s)
- Nobuaki Hirota
- Department of Biochemistry and Molecular Biology, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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15
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McMahon KA, Zajicek H, Li WP, Peyton MJ, Minna JD, Hernandez VJ, Luby-Phelps K, Anderson RGW. SRBC/cavin-3 is a caveolin adapter protein that regulates caveolae function. EMBO J 2009; 28:1001-15. [PMID: 19262564 DOI: 10.1038/emboj.2009.46] [Citation(s) in RCA: 158] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2008] [Accepted: 01/21/2009] [Indexed: 11/09/2022] Open
Abstract
Caveolae are a major membrane domain common to most cells. One of the defining features of this domain is the protein caveolin. The exact function of caveolin, however, is not clear. One possible function is to attract adapter molecules to caveolae in a manner similar to how clathrin attracts molecules to coated pits. Here, we characterize a candidate adapter molecule called SRBC. SRBC binds PKCdelta and is a member of the STICK (substrates that interact with C-kinase) superfamily of PKC-binding proteins. We also show it co-immunoprecipitates with caveolin-1. A leucine zipper in SRBC is essential for both co-precipitation with caveolin and localization to caveolae. SRBC remains associated with caveolin when caveolae bud to form vesicles (cavicles) that travel on microtubules to different regions of the cell. In the absence of SRBC, intracellular cavicle traffic is markedly impaired. We conclude that SRBC (sdr-related gene product that binds to c-kinase) and two other family members [PTRF (Pol I and transcription release factor) and SDPR] function as caveolin adapter molecules that regulate caveolae function.
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Affiliation(s)
- Kerrie-Ann McMahon
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA
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16
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Abstract
Staphylococcus aureus secretes several virulence factors modulating immune responses. Staphylococcal superantigen-like (SSL) proteins are a family of 14 exotoxins with homology to superantigens, but with generally unknown function. Recently, we showed that SSL5 binds to P-selectin glycoprotein ligand 1 dependently of sialyl Lewis X and inhibits P-selectin-dependent neutrophil rolling. Here, we show that SSL5 potently and specifically inhibits leukocyte activation by anaphylatoxins and all classes of chemokines. SSL5 inhibited calcium mobilization, actin polymerization, and chemotaxis induced by chemokines and anaphylatoxins but not by other chemoattractants. Antibody competition experiments showed that SSL5 targets several chemokine and anaphylatoxin receptors. In addition, transfection studies showed that SSL5 binds glycosylated N-termini of all G protein-coupled receptors (GPCRs) but only inhibits stimuli of protein nature that require the receptor N-terminus for activation. Furthermore, SSL5 increased binding of chemokines to cells independent of chemokine receptors through their common glycosaminoglycan-binding site. Importance of glycans was shown for both GPCR and chemokine binding. Thus, SSL5 is an important immunomodulatory protein of S aureus that targets several crucial, initial stages of leukocyte extravasation. It is therefore a potential new antiinflammatory compound for diseases associated with chemoattractants and their receptors and disorders characterized by excessive recruitment of leukocytes.
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17
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Ryan SD, Harris CS, Carswell CL, Baenziger JE, Bennett SA. Heterogeneity in the sn-1 carbon chain of platelet-activating factor glycerophospholipids determines pro- or anti-apoptotic signaling in primary neurons. J Lipid Res 2008; 49:2250-8. [DOI: 10.1194/jlr.m800263-jlr200] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
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18
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Li X, Jia Z, Shen Y, Ichikawa H, Jarvik J, Nagele RG, Goldberg GS. Coordinate suppression of Sdpr and Fhl1 expression in tumors of the breast, kidney, and prostate. Cancer Sci 2008; 99:1326-33. [PMID: 18422756 PMCID: PMC11158056 DOI: 10.1111/j.1349-7006.2008.00816.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
The Src tyrosine kinase associates with the focal adhesion adaptor protein Cas (Crk-associated substrate) to suppress the expression of potential tumor suppressor genes. For example, Src utilizes Cas to suppress the expression of the LIM-only protein Fhl1 (four and a half LIM domains 1), in order to promote non-anchored tumor-cell growth and migration. Here, we report that the promoter region of the Fhl1 gene was methylated more in Src-transformed cells than non-transformed cells. In addition, global expression analysis indicates that Fhl1 induced expression of serum deprivation response factor (Sdpr) in Src-transformed cells. Moreover, Fhl1 and Sdpr was expressed in approximately 87% and 40% of samples obtained from non-transformed breast, 100% of samples obtained from non-transformed kidney, and over 60% of samples obtained from non-transformed prostate. In contrast, Fhl1 and Sdpr was detected in approximately 40% and 7% of matched samples from mammary carcinoma, less than 11% of matched samples from kidney carcinoma, and in less than 22% of matched samples from prostate carcinoma. These data indicate that Fhl1 and Sdpr expression was significantly reduced in tumors of the breast (P < 0.02 and P < 0.001), kidney (P < 0.01), and prostate (P < 0.05). In addition, although Src can activate mitogen-activated protein kinase (MAPK) to promote tumor-cell growth, our data indicate that Src did not rely on MAPK activity to suppress the expression of Fhl1 and Sdpr in transformed cells. Thus, Src induced methylation of the promoter region of the Fhl1 gene; Src suppressed Fhl1 and Sdpr expression independent of mitogen-activated protein kinase (MAPK) activity; Fhl1 induced the expression of Sdpr in Src-transformed cells; and Fhl1 and Sdpr expression was suppressed in tumors of the breast, kidney, and prostate.
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Affiliation(s)
- Xun Li
- Molecular Biology Department, University of Medicine and Dentistry of New Jersey, Stratford, NJ 08084, USA
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19
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Gui C, Zhu W, Chen G, Luo X, Liew OW, Puah CM, Chen K, Jiang H. Understanding the regulation mechanisms of PAF receptor by agonists and antagonists: Molecular modeling and molecular dynamics simulation studies. Proteins 2007; 67:41-52. [PMID: 17243151 DOI: 10.1002/prot.21213] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Platelet-activating factor receptor (PAFR) is a member of G-protein coupled receptor (GPCR) superfamily. Understanding the regulation mechanisms of PAFR by its agonists and antagonists at the atomic level is essential for designing PAFR antagonists as drug candidates for treating PAF-mediated diseases. In this study, a 3D model of PAFR was constructed by a hierarchical approach integrating homology modeling, molecular docking and molecular dynamics (MD) simulations. Based on the 3D model, regulation mechanisms of PAFR by agonists and antagonists were investigated via three 8-ns MD simulations on the systems of apo-PAFR, PAFR-PAF and PAFR-GB. The simulations revealed that binding of PAF to PAFR triggers the straightening process of the kinked helix VI, leading to its activated state. In contrast, binding of GB to PAFR locks PAFR in its inactive state.
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Affiliation(s)
- Chunshan Gui
- Drug Discovery and Design Centre, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai 201203, People's Republic of China
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20
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Perez DM. Structure-function of alpha1-adrenergic receptors. Biochem Pharmacol 2006; 73:1051-62. [PMID: 17052695 PMCID: PMC2034198 DOI: 10.1016/j.bcp.2006.09.010] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2006] [Revised: 09/07/2006] [Accepted: 09/11/2006] [Indexed: 11/17/2022]
Abstract
The Easson-Stedman hypothesis provided the rationale for the first studies of drug design for the alpha(1)-adrenergic receptor. Through chemical modifications of the catecholamine core structure, the need was established for a protonated amine, a beta-hydroxyl on a chiral center, and an aromatic ring with substitutions capable of hydrogen bonding. After the receptors were cloned and three alpha(1)-adrenergic receptor subtypes were discovered, drug design became focused on the analysis of receptor structure and new interactions were uncovered. It became clear that alpha(1)- and beta-adrenergic receptors did not share stringent homology in the ligand-binding pocket but this difference has allowed for more selective drug design. Novel discoveries on allosterism and agonist trafficking may be used in the future design of therapeutics with fewer side effects. This review will explore past and current knowledge of the structure-function of the alpha(1)-adrenergic receptor subtypes.
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Affiliation(s)
- Dianne M Perez
- Department of Molecular Cardiology, NB5, The Cleveland Clinic Foundation, Lerner Research Institute, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
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21
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Abstract
Studies have been amassed in the past several years indicating that an agonist can conform a receptor into an activation state that is dependent upon an intrinsic property of the agonist usually based upon its chemical composition. Theoretically, each different agonist could impart its own unique activation state. Evidence for multiple signaling states for the G-protein-coupled receptors will be reviewed and is derived from many different pharmacological behaviors: efficacy, kinetics, protean agonism, differential desensitization and internalization, inverse agonism, and fusion chimeras. A recent extension of the ternary complex model is suggested by evidence that the different processes that govern deactivation, such as desensitization and internalization, is also regulated by conformers specific to the agonist. Rhodopsin may serve as a primer for the study of multiple activation states. Therapeutic implications that utilize multiple signaling states hold vast promise in the rationale design of drugs.
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Affiliation(s)
- Dianne M Perez
- Department of Molecular Cardiology, Lerner Research Institute, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195, USA.
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22
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Zhu W, Chen G, Hu L, Luo X, Gui C, Luo C, Puah CM, Chen K, Jiang H. QSAR analyses on ginkgolides and their analogues using CoMFA, CoMSIA, and HQSAR. Bioorg Med Chem 2005; 13:313-22. [PMID: 15598554 DOI: 10.1016/j.bmc.2004.10.027] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2004] [Revised: 10/10/2004] [Accepted: 10/10/2004] [Indexed: 11/22/2022]
Abstract
Ginkgolides, isolated from ginkgo balba leaves, were found to be powerful as natural antagonists of human platelet activating factor (PAF) in treatment of some diseases such as acute inflammation, tissue rejection, asthma, and ischemic injury. Ginkgolides have a cage skeleton consisting of six five-membered rings, therefore, are very tough to be synthesized. For finding new powerful substitutes of the natural ginkgolides for treating those diseases, three methods, viz. CoMFA, CoMSIA, and HQSAR, were used to investigate the relationship between 117 ginkgolide analogues with great structural diversity and their bioactivities against PAF receptor. The high q2 released from the different QSAR methods, ranging from 0.583 to 0.684, suggests that three rational and predictive QSAR models were successfully built. These models also show clearly how steric, electrostatic, hydrophobicity, and individual atom affect molecular bioactivity as antagonists of PAF. These results could also be used to account for the unusually higher bioactivity of ginkgolide B than other ginkgolides. The possible binding mechanism between ginkgolides and human PAF receptor was also deduced based on the QSAR models. Therefore, this study should be very helpful in discovering new drugs as PAF antagonists in fighting against various diseases related to PAF and PAF receptor.
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Affiliation(s)
- Weiliang Zhu
- Drug Discovery and Design Centre, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Pudong, Shanghai, PR China
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23
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Kristiansen K. Molecular mechanisms of ligand binding, signaling, and regulation within the superfamily of G-protein-coupled receptors: molecular modeling and mutagenesis approaches to receptor structure and function. Pharmacol Ther 2004; 103:21-80. [PMID: 15251227 DOI: 10.1016/j.pharmthera.2004.05.002] [Citation(s) in RCA: 392] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The superfamily of G-protein-coupled receptors (GPCRs) could be subclassified into 7 families (A, B, large N-terminal family B-7 transmembrane helix, C, Frizzled/Smoothened, taste 2, and vomeronasal 1 receptors) among mammalian species. Cloning and functional studies of GPCRs have revealed that the superfamily of GPCRs comprises receptors for chemically diverse native ligands including (1) endogenous compounds like amines, peptides, and Wnt proteins (i.e., secreted proteins activating Frizzled receptors); (2) endogenous cell surface adhesion molecules; and (3) photons and exogenous compounds like odorants. The combined use of site-directed mutagenesis and molecular modeling approaches have provided detailed insight into molecular mechanisms of ligand binding, receptor folding, receptor activation, G-protein coupling, and regulation of GPCRs. The vast majority of family A, B, C, vomeronasal 1, and taste 2 receptors are able to transduce signals into cells through G-protein coupling. However, G-protein-independent signaling mechanisms have also been reported for many GPCRs. Specific interaction motifs in the intracellular parts of these receptors allow them to interact with scaffold proteins. Protein engineering techniques have provided information on molecular mechanisms of GPCR-accessory protein, GPCR-GPCR, and GPCR-scaffold protein interactions. Site-directed mutagenesis and molecular dynamics simulations have revealed that the inactive state conformations are stabilized by specific interhelical and intrahelical salt bridge interactions and hydrophobic-type interactions. Constitutively activating mutations or agonist binding disrupts such constraining interactions leading to receptor conformations that associates with and activate G-proteins.
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Affiliation(s)
- Kurt Kristiansen
- Department of Pharmacology, Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway.
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24
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Sparling ML. Echindoderm Gametes Make PAF; Artificial Activation by External PAF Bipasses Calcium Channels Regulated by 2APB Unlike Jelly Activation of Sperm. J CHIN CHEM SOC-TAIP 2004. [DOI: 10.1002/jccs.200400171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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25
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Stafforini DM, McIntyre TM, Zimmerman GA, Prescott SM. Platelet-activating factor, a pleiotrophic mediator of physiological and pathological processes. Crit Rev Clin Lab Sci 2004; 40:643-72. [PMID: 14708958 DOI: 10.1080/714037693] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Platelet-activating factor (PAF) is a potent proinflammatory phospholipid with diverse pathological and physiological effects. This bioactive phospholipid mediates processes as diverse as wound healing, physiological inflammation, apoptosis, angiogenesis, reproduction and long-term potentiation. Recent progress has demonstrated the participation of MAP kinase signaling pathways as modulators of the two critical enzymes, phospholipase A2 and acetyltransferase, involved in the remodeling pathway of PAF biosynthesis. The unregulated production of structural analogs of PAF by non-specific oxidative reactions has expanded this superfamily of signaling molecules to include "PAF-like" lipids whose mode of action is identical to that of authentic PAF. The action of members of this family is mediated by the PAF receptor, a G protein-coupled membrane-spanning molecule that can engage multiple signaling pathways in various cell types. Inappropriate activation of this signaling pathway is associated with many diseases in which inflammation is thought to be one of the underlying features. Inactivation of all members of the PAF superfamily occurs by a unique class of enzymes, the PAF acetylhydrolases, that have been characterized at the molecular level and that terminate signals initiated by both regulated and unregulated PAF production.
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Affiliation(s)
- Diana M Stafforini
- Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah 84112-5550, USA.
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26
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Kanthasamy AG, Kitazawa M, Kanthasamy A, Anantharam V. Role of proteolytic activation of protein kinase Cdelta in oxidative stress-induced apoptosis. Antioxid Redox Signal 2003; 5:609-20. [PMID: 14580317 DOI: 10.1089/152308603770310275] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Protein kinase Cdelta (PKCdelta), a member of the novel PKC family, is emerging as a redox-sensitive kinase in various cell types. Oxidative stress activates the PKCdelta kinase by translocation, tyrosine phosphorylation, or proteolysis. During proteolysis, caspase-3 cleaves the native PKCdelta (72-74 kDa) into 41-kDa catalytically active and 38-kDa regulatory fragments to persistently activate the kinase. The proteolytic activation of PKCdelta plays a key role in promoting apoptotic cell death in various cell types, including neuronal cells. Attenuation of PKCdelta proteolytic activation by antioxidants suggests that the cellular redox status can influence activation of the proapoptotic kinase. PKCdelta may also amplify apoptotic signaling via positive feedback activation of the caspase cascade. Thus, the dual role of PKCdelta as a mediator and amplifier of apoptosis may be important in the pathogenesis of major neurodegenerative disorders, such as Parkinson's disease, Alzheimer's disease, and Huntington disease.
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Affiliation(s)
- Anumantha G Kanthasamy
- Parkinson's Disorders Research Program, Department of Biomedical Sciences, Iowa State University, Ames, IA 50011, USA.
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27
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Schulz A, Schöneberg T. The structural evolution of a P2Y-like G-protein-coupled receptor. J Biol Chem 2003; 278:35531-41. [PMID: 12835326 DOI: 10.1074/jbc.m303346200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Based on the now available crystallographic data of the G-protein-coupled receptor (GPCR) prototype rhodopsin, many studies have been undertaken to build or verify models of other GPCRs. Here, we mined evolution as an additional source of structural information that may guide GPCR model generation as well as mutagenesis studies. The sequence information of 61 cloned orthologs of a P2Y-like receptor (GPR34) enabled us to identify motifs and residues that are important for maintaining the receptor function. The sequence data were compared with available sequences of 77 rhodopsin orthologs. Under a negative selection mode, only 17% of amino acid residues were preserved during 450 million years of GPR34 evolution. On the contrary, in rhodopsin evolution approximately 43% residues were absolutely conserved between fish and mammals. Despite major differences in their structural conservation, a comparison of structural data suggests that the global arrangement of the transmembrane core of GPR34 orthologs is similar to rhodopsin. The evolutionary approach was further applied to functionally analyze the relevance of common scaffold residues and motifs found in most of the rhodopsin-like GPCRs. Our analysis indicates that, in contrast to other GPCRs, maintaining the unique function of rhodopsin requires a more stringent network of relevant intramolecular constrains.
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Affiliation(s)
- Angela Schulz
- Institute of Pharmacology, Medical Faculty, Free University Berlin, 14195 Berlin, Germany
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28
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Proudfoot JM, Croft KD, Puddey IB, Beilin LJ. Angiotensin II type 1 receptor antagonists inhibit basal as well as low-density lipoprotein and platelet-activating factor-stimulated human monocyte chemoattractant protein-1. J Pharmacol Exp Ther 2003; 305:846-53. [PMID: 12626661 DOI: 10.1124/jpet.102.047795] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Monocyte chemoattractant protein-1 (MCP-1) is a potent chemotactic agent for monocytes and other cells and is thought to be involved in atherosclerosis, recruiting monocytes to the subendothelial space or to the site of inflammation. Angiotensin II has been demonstrated, at least in animal models, to stimulate MCP-1 expression. We investigated the effect of the angiotensin II type 1 (AT1) receptor antagonists irbesartan and losartan on MCP-1 production by freshly isolated human monocytes. Irbesartan and losartan inhibited basal MCP-1 production in a dose-dependent manner. Low-density lipoprotein (LDL) stimulated MCP-1 in a concentration-dependent manner, with 200 microg/ml LDL protein giving a 2-fold increase in MCP-1. Irbesartan and losartan dose dependently blocked LDL-stimulated MCP-1. An angiotensin II type 2 receptor antagonist, S-(+)-1-([4-(dimethylamino)-3-methylphenyl]methyl)-5-(diphenylacetyl)-4,5,6,7-tetrahydro-1H-imidazo(4,5-c)pyridine-6-carboxylic acid (PD123319), had no significant effect on basal MCP-1 levels or LDL-stimulated MCP-1. After noting homology between the AT1 receptor and the platelet-activating factor (PAF) receptor, we showed that irbesartan inhibited both [3H]PAF binding to human monocytes and carbamyl-PAF stimulation of MCP-1. However, irbesartan affinity for the PAF receptor was 700 times less than PAF, suggesting that there may be another mechanism for irbesartan inhibition of PAF-stimulated MCP-1. This is the first report showing that AT1 receptor antagonists inhibit basal as well as LDL- and PAF-stimulated MCP-1 production in freshly isolated human monocytes.
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Affiliation(s)
- Julie M Proudfoot
- Department of Medicine, University of Western Australia and the West Australian Institute for Medical Research, Perth, Australia.
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29
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Le MT, Vanderheyden PML, Szaszák M, Hunyady L, Kersemans V, Vauquelin G. Peptide and nonpeptide antagonist interaction with constitutively active human AT1 receptors. Biochem Pharmacol 2003; 65:1329-38. [PMID: 12694873 DOI: 10.1016/s0006-2952(03)00072-8] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Wild type human AT(1) receptors (WT-AT(1)) and mutant receptors, in which Asn(111) was replaced by glycine (N111G), alanine (N111A) and serine (N111S), or in which Asp(281) was replaced by alanine (D281A) or in which N111G and D281A replacements were combined, were transiently expressed in CHO-K1 cells. While the biphenyltetrazole compound candesartan dissociated slowly and behaved as an insurmountable antagonist for WT-AT(1), it dissociated swiftly and only produced a rightward shift of the angiotensin Ang II- and -IV dose-response curves for inositol phosphate (IP) accumulation in cells expressing N111G. [3H]candesartan competition binding yielded the same potency order of the related biphenyltetrazoles for WT-AT(1) and mutated receptors, i.e. candesartan>EXP3174>irbesartan>losartan. Affinities were equal for WT-AT(1) and D281A and 40- to 400-fold lower for all Asn(111) mutants. Mutations did not affect the affinity of the peptide antagonist [Sar(1)Ile(8)]Ang II (SARILE). Basal IP accumulation in cells with WT-AT(1) was not affected by any biphenyltetrazole antagonists and was increased by SARILE to 19% of the maximal Ang II stimulation. Basal IP accumulation was higher for cells expressing the Asn(111)-mutated receptors. For N111G, this accumulation was partially inhibited by all the biphenyltetrazoles upon long-term (18hr) exposure. In these cells SARILE produced the same maximal stimulation as Ang II. Asn(111)-mutated AT(1) receptors are thought to mimic the pre-activated state of the wild type receptor and comparing the efficacy and affinity of ligands for such mutated receptors facilitate the distinction of partial (SARILE) and inverse (biphenyltetrazoles) agonists from true antagonists.
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Affiliation(s)
- Minh Tam Le
- Department of Molecular and Biochemical Pharmacology, Institute for Molecular Biology and Biotechnology, Vrije Universiteit Brussel (VUB), Pleinlaan 2, Belgium.
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30
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Hunyady L, Vauquelin G, Vanderheyden P. Agonist induction and conformational selection during activation of a G-protein-coupled receptor. Trends Pharmacol Sci 2003; 24:81-6. [PMID: 12559772 DOI: 10.1016/s0165-6147(02)00050-0] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Substitutions of Asn111 of the AT(1) angiotensin receptor and mutations of the corresponding amino acids in other G-protein-coupled receptors (GPCRs) cause constitutive receptor activation. Ligand binding and signalling of constitutively active mutant GPCRs are discussed and similarities and differences during the activation of amine and peptide GPCRs are identified. Studies using the AT(1) receptor suggest that conformational selection is not sufficient to explain the mechanism of receptor activation, and that agonist binding to the receptor provides energy to induce activation of the receptor. Because agonist binding also actively facilitates the conformational rearrangements leading to activation of other GPCRs we propose that agonist induction should be considered as a general mechanism of GPCR activation.
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Affiliation(s)
- László Hunyady
- Department of Physiology, Semmelweis University, Faculty of Medicine, Budapest, Hungary
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31
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Marrache AM, Gobeil F, Bernier SG, Stankova J, Rola-Pleszczynski M, Choufani S, Bkaily G, Bourdeau A, Sirois MG, Vazquez-Tello A, Fan L, Joyal JS, Filep JG, Varma DR, Ribeiro-Da-Silva A, Chemtob S. Proinflammatory gene induction by platelet-activating factor mediated via its cognate nuclear receptor. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2002; 169:6474-81. [PMID: 12444157 DOI: 10.4049/jimmunol.169.11.6474] [Citation(s) in RCA: 97] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
It has been postulated that intracellular binding sites for platelet-activating factor (PAF) contribute to proinflammatory responses to PAF. Isolated nuclei from porcine cerebral microvascular endothelial cells (PCECs) produced PAF-molecular species in response to H(2)O(2). Using FACS analysis, we demonstrated the expression of PAF receptors on cell and nuclear surfaces of PCECs. Confocal microscopy studies performed on PCECs, Chinese hamster ovary cells stably overexpressing PAF receptors, and isolated nuclei from PCECs also showed a robust nuclear distribution of PAF receptors. Presence of PAF receptors at the cell nucleus was further revealed in brain endothelial cells by radioligand binding experiments, immunoblotting, and in situ in brain by immunoelectron microscopy. Stimulation of nuclei with methylcarbamate-PAF evoked a decrease in cAMP production and a pertussis toxin-sensitive rise in nuclear calcium, unlike observations in plasma membrane, which exhibited a pertussis toxin-insensitive elevation in inositol phosphates. Moreover, on isolated nuclei methylcarbamate-PAF evoked the expression of proinflammatory genes inducible nitric oxide synthase and cyclooxygenase-2 (COX-2) and was associated with augmented extracellular signal-regulated kinase 1/2 phosphorylation and NF-kappaB binding to the DNA consensus sequence. COX-2 expression was prevented by mitogen-activated protein kinase kinase/extracellular signal-regulated kinase 1/2 and NF-kappaB inhibitors. This study describes for the first time the nucleus as a putative organelle capable of generating PAF and expresses its receptor, which upon stimulation induces the expression of the proinflammatory gene COX-2.
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Affiliation(s)
- A Marilise Marrache
- Department of Pharmacology and Therapeutics, McGill University, Montreal, Quebec, Canada
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Tabellini G, Bortul R, Aluigi M, Billi AM, Bareggi R, Grill V, Narducci P, Martelli AM. Binding of elements of protein kinase C-alpha regulatory domain to lamin B1. Cell Signal 2002; 14:819-27. [PMID: 12135703 DOI: 10.1016/s0898-6568(02)00021-9] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Previous results from our laboratory have demonstrated that lamin B1 is a protein kinase C (PKC)-binding protein. Here, we have identified the regions of PKC-alpha that are important for this binding. By means of overlay assays and fusion proteins made of glutathione-S-transferase (GST) fused to elements of the regulatory domain of rat PKC-alpha, we have established that binding occurs through both the V1 region and a portion of the C2 region (i.e., the calcium-dependent lipid binding [CaLB] domain) of the kinase. In particular, we have found that amino acids 200-217 of the CaLB domain are essential for binding lamin B1, as a synthetic peptide corresponding to this stretch of amino acids prevented the interaction between the CaLB domain of PKC-alpha and lamin B1. In agreement with the results of other investigators, we have determined that binding of regulatory elements of PKC-alpha to lamin B1 does not require the presence of cofactors such as PS and Ca(2+). We have also found that the binding site of lamin B1 for PKC-alpha is localized in the carboxyl-terminus of the lamin. Our findings may prove to be important in shedding more light on the mechanisms that regulate PKC functions within the nuclear compartment and may also lead to the synthesis of isozyme-specific pharmacological tools to attenuate or reverse PKC-dependent nuclear signalling pathways important for the pathogenesis of cancer.
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Affiliation(s)
- Giovanna Tabellini
- Dipartimento di Morfologia Umana Normale, Università di Trieste, via Manzoni 16, 34138 Trieste, Italy
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Ito N, Yokomizo T, Sasaki T, Kurosu H, Penninger J, Kanaho Y, Katada T, Hanaoka K, Shimizu T. Requirement of phosphatidylinositol 3-kinase activation and calcium influx for leukotriene B4-induced enzyme release. J Biol Chem 2002; 277:44898-904. [PMID: 12244116 DOI: 10.1074/jbc.m208051200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Leukotriene B(4) (LTB(4)) is a potent lipid mediator involved in host defense and inflammatory responses. It causes chemotaxis, generation of reactive oxygen species, and degranulation. However, only little is known of the molecular mechanisms by which LTB(4) induces these biological activities. To analyze the intracellular signaling pathways to mediate lysosomal enzyme release through the cloned LTB(4) receptor (BLT1), we transfected BLT1 to rat basophilic leukemia cells (RBL-2H3). LTB(4) dose-dependently released beta-hexosaminidase, and the release was mostly inhibited when the cells were pretreated with pertussis toxin, indicating that the degranulation is mediated by G(i) proteins. LTB(4) activated phosphatidylinositol 3-kinase (PI3-K) through G(i), and inhibition of PI3-K by wortmannin or LY290042 inhibited degranulation. Granulocytes from PI3-Kgamma-deficient mice showed reduced LTB(4)-induced degranulation, suggesting that this isozyme of PI3-K is involved in the degranulation. LTB(4) also caused calcium release from intracellular stores and calcium influx from the outside milieu through G(i), but only the calcium influx is critical for the lysosomal enzyme release. Calcium influx and PI3-K activation are both downstream events of G(i), since they were inhibited by pertussis toxin. These two events are in essence independent each other, because calcium depletion did not affect PI3-K, and inhibition of PI3-K did not attenuate calcium influx significantly. Thus, our results have clearly shown that LTB(4) binds BLT1 and activates G(i)-like protein, and both PI3-Kgamma activation and a sustained calcium elevation by calcium influx are necessary for enzyme release in these cells.
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Affiliation(s)
- Nobuko Ito
- Department of Biochemistry and Molecular Biology, University of Tokyo, Japan
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Ishii I, Ye X, Friedman B, Kawamura S, Contos JJA, Kingsbury MA, Yang AH, Zhang G, Brown JH, Chun J. Marked perinatal lethality and cellular signaling deficits in mice null for the two sphingosine 1-phosphate (S1P) receptors, S1P(2)/LP(B2)/EDG-5 and S1P(3)/LP(B3)/EDG-3. J Biol Chem 2002; 277:25152-9. [PMID: 12006579 DOI: 10.1074/jbc.m200137200] [Citation(s) in RCA: 194] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Five cognate G protein-coupled receptors (S1P(1-5)) have been shown to mediate various cellular effects of sphingosine 1-phosphate (S1P). Here we report the generation of mice null for S1P(2) and for both S1P(2) and S1P(3). S1P(2)-null mice were viable and fertile and developed normally. The litter sizes from S1P(2)S1P(3) double-null crosses were remarkably reduced compared with controls, and double-null pups often did not survive through infancy, although double-null survivors lacked any obvious phenotype. Mouse embryonic fibroblasts (MEFs) were examined for the effects of receptor deletions on S1P signaling pathways. Wild-type MEFs were responsive to S1P in activation of Rho and phospholipase C (PLC), intracellular calcium mobilization, and inhibition of forskolin-activated adenylyl cyclase. S1P(2)-null MEFs showed a significant decrease in Rho activation, but no effect on PLC activation, calcium mobilization, or adenylyl cyclase inhibition. Double-null MEFs displayed a complete loss of Rho activation and a significant decrease in PLC activation and calcium mobilization, with no effect on adenylyl cyclase inhibition. These data extend our previous findings on S1P(3)-null mice and indicate preferential coupling of the S1P(2) and S1P(3) receptors to Rho and PLC/Ca(2+) pathways, respectively. Although either receptor subtype supports embryonic development, deletion of both produces marked perinatal lethality, demonstrating an essential role for combined S1P signaling by these receptors.
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Affiliation(s)
- Isao Ishii
- Department of Pharmacology, School of Medicine, University of California at San Diego, La Jolla 92093-0636, USA
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Oka T, Sato K, Hori M, Ozaki H, Karaki H. FcepsilonRI cross-linking-induced actin assembly mediates calcium signalling in RBL-2H3 mast cells. Br J Pharmacol 2002; 136:837-46. [PMID: 12110608 PMCID: PMC1573417 DOI: 10.1038/sj.bjp.0704788] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
1. To determine the role of actin assembly in the Ca(2+) signalling of mast cells activated by cross-linking of FcepsilonRI, we examined the effects of cytochalasin D, an inhibitor of actin polymerization. 2. In the RBL-2H3 cells, F-actin content was increased by sensitization with anti-dinitrophenol (DNP) IgE. In these cells, cytochalasin D induced oscillatory increases in cytosolic Ca(2+) ([Ca(2+)](i)); these increase were inhibited by jasplakinolide, a stabilizer of actin filaments. 3. In the IgE-sensitized RBL-2H3 cells, DNP-human serum albumin (DNP-HSA) augmented actin assembly. DNP-HSA also increased the production of IP(3), [Ca(2+)](i) and degranulation. Cytochalasin D enhanced all of these DNP-HSA-induced effects. 4. In a Ca(2+)-free solution, DNP-HSA induced a transient increase in [Ca(2+)](i), and this increase was accelerated by cytochalasin D. After cessation of the DNP-HSA-induced Ca(2+) release, the re-addition of Ca(2+) induced a sustained increase in [Ca(2+)](i) through capacitative Ca(2+) entry (CCE), and this increase was enhanced by cytochalasin D. 5 The effect of cytochalasin D in enhancing the CCE activity was prevented by xestospongin C. 6. In contrast, neither the Ca(2+) release nor the CCE activation that was induced by thapsigargin was affected by cytochalasin D. 7. These results suggest that actin de-polymerization stimulates the FcepsilonRI-mediated signalling to augment the release of Ca(2+) from the endoplasmic reticulum in RBL-2H3 cells.
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Affiliation(s)
- Tatsuya Oka
- Department of Veterinary Pharmacology, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Koichi Sato
- Department of Radio Isotope Center, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Masatoshi Hori
- Department of Veterinary Pharmacology, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
| | - Hiroshi Ozaki
- Department of Veterinary Pharmacology, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
- Author for correspondence:
| | - Hideaki Karaki
- Department of Veterinary Pharmacology, The University of Tokyo, Bunkyo-Ku, Tokyo 113-8657, Japan
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Abstract
The CB1 cannabinoid receptor has been shown to couple with pertussis toxin (PTX)-sensitive Gi/o proteins and inhibit adenylyl cyclase. However, in certain conditions, CB1 mediates adenylyl cyclase activation, possibly through Gs-type G proteins. In rat B103 neuroblastoma cells in which CBI gene was endogenously expressed, anandamide inhibited forskolin-induced cAMP accumulation via PTX-sensitive pathways. When CB1 was heterologously over-expressed using a retroviral transfer, high concentrations of anandamide increased forskolin-induced cAMP accumulation, and this effect was more prominent when cells were pretreated with PTX. In CB1-over-expressing B103 cells, anandamide induced cell rounding via a PTX-insensitive/Rho kinase inhibitor-sensitive pathway. These results suggest that the CB1 receptor could couple with G proteins that activate Rho (possibly G12/13) as well as Gi/o and Gs.
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Affiliation(s)
- Isao Ishii
- Department of Molecular Genetics, National Institute of Neuroscience, NCNP, Ogawahigashi 4-1-1, Kodaira, Tokyo 187-8502, Japan
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37
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Marie J, Richard E, Pruneau D, Paquet JL, Siatka C, Larguier R, Poncé C, Vassault P, Groblewski T, Maigret B, Bonnafous JC. Control of conformational equilibria in the human B2 bradykinin receptor. Modeling of nonpeptidic ligand action and comparison to the rhodopsin structure. J Biol Chem 2001; 276:41100-11. [PMID: 11495910 DOI: 10.1074/jbc.m104875200] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
A prototypic study of the molecular mechanisms of activation or inactivation of peptide hormone G protein-coupled receptors was carried out on the human B2 bradykinin receptor. A detailed pharmacological analysis of receptor mutants possessing either increased constitutive activity or impaired activation or ligand recognition allowed us to propose key residues participating in intramolecular interaction networks stabilizing receptor inactive or active conformations: Asn(113) and Tyr(115) (TM III), Trp(256) and Phe(259) (TM VI), Tyr(295) (TM VII) which are homologous of the rhodopsin residues Gly(120), Glu(122), Trp(265), Tyr(268), and Lys(296), respectively. An essential experimental finding was the spatial proximity between Asn(113), which is the cornerstone of inactive conformations, and Trp(256) which plays a subtle role in controlling the balance between active and inactive conformations. Molecular modeling and mutagenesis data showed that Trp(256) and Tyr(295) constitute, together with Gln(288), receptor contact points with original nonpeptidic ligands. It provided an explanation for the ligand inverse agonist behavior on the WT receptor, with underlying restricted motions of TMs III, VI, and VII, and its agonist behavior on the Ala(113) and Phe(256) constitutively activated mutants. These data on the B2 receptor emphasize that conformational equilibria are controlled in a coordinated fashion by key residues which are located at strategic positions for several G protein-coupled receptors. They are discussed in comparison with the recently determined rhodopsin crystallographic structure.
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Affiliation(s)
- J Marie
- INSERM U439, 70 rue de Navacelles 34090 Montpellier, France
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38
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Ishii I, Friedman B, Ye X, Kawamura S, McGiffert C, Contos JJ, Kingsbury MA, Zhang G, Brown JH, Chun J. Selective loss of sphingosine 1-phosphate signaling with no obvious phenotypic abnormality in mice lacking its G protein-coupled receptor, LP(B3)/EDG-3. J Biol Chem 2001; 276:33697-704. [PMID: 11443127 DOI: 10.1074/jbc.m104441200] [Citation(s) in RCA: 202] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Sphingosine 1-phosphate (S1P) exerts diverse physiological actions by activating its cognate G protein-coupled receptors. Five S1P receptors have been identified in mammals: LP(B1)/EDG-1, LP(B2)/H218/AGR16/EDG-5, LP(B3)/EDG-3, LP(B4)/NRG-1/EDG-8, and LP(C1)/EDG-6. One of these receptors, LP(B1), has recently been shown to be essential for mouse embryonic development. Here we disrupted the lp(B3) gene in mice, resulting in the complete absence of lp(B3) gene, transcript, and LP(B3) protein. LP(B3)-null mice were viable and fertile and developed normally with no obvious phenotypic abnormality. We prepared mouse embryonic fibroblast (MEF) cells to examine effects of LP(B3) deletion on S1P-induced signal transduction pathways. Wild-type MEF cells expressed lp(B1), lp(B2), and lp(B3) but neither lp(B4) nor lp(C1), and they were highly responsive to S1P in phospholipase C (PLC) activation, adenylyl cyclase inhibition, and Rho activation. Identically prepared LP(B3)-null MEF cells showed significant decreases in PLC activation, slight decreases in adenylyl cyclase inhibition, and no change in Rho activation. Retrovirus-mediated rescue of the LP(B3) receptor in LP(B3)-null MEF cells restored S1P-dependent PLC activation and adenylyl cyclase inhibition. These results indicate a nonessential role for LP(B3) in normal development of mouse but show nonredundant cellular signaling mediated by a single type of S1P receptor.
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Affiliation(s)
- I Ishii
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California 92093-0636, USA
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39
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Ballesteros JA, Shi L, Javitch JA. Structural Mimicry in G Protein-Coupled Receptors: Implications of the High-Resolution Structure of Rhodopsin for Structure-Function Analysis of Rhodopsin-Like Receptors. Mol Pharmacol 2001. [DOI: 10.1124/mol.60.1.1] [Citation(s) in RCA: 357] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
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40
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Prescott SM, Zimmerman GA, Stafforini DM, McIntyre TM. Platelet-activating factor and related lipid mediators. Annu Rev Biochem 2001; 69:419-45. [PMID: 10966465 DOI: 10.1146/annurev.biochem.69.1.419] [Citation(s) in RCA: 550] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Platelet-activating factor (PAF) is a phospholipid with potent, diverse physiological actions, particularly as a mediator of inflammation. The synthesis, transport, and degradation of PAF are tightly regulated, and the biochemical basis for many of these processes has been elucidated in recent years. Many of the actions of PAF can be mimicked by structurally related phospholipids that are derived from nonenzymatic oxidation, because such compounds can bind to the PAF receptor. This process circumvents much of the biochemical control and presumably is regulated primarily by the rate of degradation, which is catalyzed by PAF acetylhydrolase. The isolation of cDNA clones encoding most of the key proteins involved in regulating PAF has allowed substantial recent progress and will facilitate studies to determine the structural basis for substrate specificity and the precise role of PAF in physiological events.
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Affiliation(s)
- S M Prescott
- The Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah 84112, USA.
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41
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Abstract
G protein-coupled receptors (GPCRs) represent the largest family of signal-transducing molecules known. They convey signals for light and many extracellular regulatory molecules. GPCRs have been found to be dysfunctional/dysregulated in a growing number of human diseases and have been estimated to be the targets of more than 30% of the drugs used in clinical medicine today. Thus, understanding how GPCRs function at the molecular level is an important goal of biological research. In order to understand function at this level, it is necessary to delineate the 3D structure of these receptors. Recently, the 3D structure of rhodopsin has been resolved, but in the absence of experimentally determined 3D structures of other GPCRs, a powerful approach is to construct a theoretical model for the receptor and refine it based on experimental results. Computer-generated models for many GPCRs have been constructed. In this article, we will review these studies. We will place the greatest emphasis on an iterative, bi-directional approach in which models are used to generate hypotheses that are tested by experimentation and the experimental findings are, in turn, used to refine the model. The success of this approach is due to the synergistic interaction between theory and experiment.
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Affiliation(s)
- M C Gershengorn
- Division of Molecular Medicine (M.C.G.), Department of Medicine, Weill Medical College and Graduate School of Medical Sciences of Cornell University, New York, New York 10021, USA.
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Ishii I, Contos JJ, Fukushima N, Chun J. Functional comparisons of the lysophosphatidic acid receptors, LP(A1)/VZG-1/EDG-2, LP(A2)/EDG-4, and LP(A3)/EDG-7 in neuronal cell lines using a retrovirus expression system. Mol Pharmacol 2000; 58:895-902. [PMID: 11040035 DOI: 10.1124/mol.58.5.895] [Citation(s) in RCA: 168] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Lysophosphatidic acid (LPA) is a potent lipid mediator with diverse physiological actions on a wide variety of cells and tissues. Three cognate G-protein-coupled receptors have been identified as mammalian LPA receptors: LP(A1)/VZG-1/EDG-2, LP(A2)/EDG-4, and LP(A3)/EDG-7. The mouse forms of these genes were analyzed in rodent cell lines derived from nervous system cells that can express these receptors functionally. An efficient retrovirus expression system was used, and each receptor was heterologously expressed in B103 rat neuroblastoma cells that neither express these receptors nor respond to LPA in all assays tested. Comparative analyses of signaling pathways that are activated within minutes of ligand delivery were carried out. LPA induced cell rounding in LP(A1)- and LP(A2)-expressing cells. By contrast, LP(A3) expression resulted in neurite elongation in B103 cells and inhibited LPA-dependent cell rounding in TR mouse neuroblast cells that endogenously express LP(A1) and LP(A2) but not LP(A3). Each of the receptors could couple to multiple G-proteins and induced LPA-dependent inositol phosphate production, mitogen-activated protein kinase activation, and arachidonic acid release while inhibiting forskolin-induced cAMP accumulation, although the efficacy and potency of LPA varied from receptor to receptor. These results indicate both shared and distinct functions among the three mammalian LPA receptors. The retroviruses developed in this study should provide tools for addressing these functions in vivo.
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Affiliation(s)
- I Ishii
- Department of Pharmacology, School of Medicine, University of California, San Diego, La Jolla, California, USA
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43
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Iwasiow RM, Nantel MF, Tiberi M. Delineation of the structural basis for the activation properties of the dopamine D1 receptor subtypes. J Biol Chem 1999; 274:31882-90. [PMID: 10542214 DOI: 10.1074/jbc.274.45.31882] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To delineate the structural determinants involved in the constitutive activation of the D1 receptor subtypes, we have constructed chimeras between the D1A and D1B receptors. These chimeras harbored a cognate domain corresponding to transmembrane regions 6 and 7 as well as the third extracellular loop (EL3) and cytoplasmic tail, a domain referred herein to as the terminal receptor locus (TRL). A chimeric D1A receptor harboring the D1B-TRL (chimera 1) displays an increased affinity for dopamine that is indistinguishable from the wild-type D1B receptor. Likewise, a chimeric D1B receptor containing the D1A-TRL cassette (chimera 2) binds dopamine with a reduced affinity that is highly reminiscent of the dopamine affinity for the wild-type D1A receptor. Furthermore, we show that the agonist independent activity of chimera 1 is identical to the wild-type D1B receptor whereas the chimera 2 displays a low agonist independent activity that is indistinguishable from the wild-type D1A receptor. Dopamine potencies for the wild-type D1A and D1B receptor were recapitulated in cells expressing the chimera 2 or chimera 1, respectively. However, the differences observed in agonist-mediated maximal activation of adenylyl cyclase elicited by the D1A and D1B receptors remain unchanged in cells expressing the chimeric receptors. To gain further mechanistic insights into the structural determinants of the TRL involved in the activation properties of the D1 receptor subtypes, we have engineered two additional chimeric D1 receptors that contain the EL3 region of their respective cognate wild-type counterparts (hD1A-EL3B and hD1B-EL3A). In marked contrast to chimera 1 and 2, dopamine affinity and constitutive activation were partially modulated by the exchange of the EL3. Meanwhile, hD1A-EL3B and hD1B-EL3A mutant receptors display a full switch in the agonist-mediated maximal activation, which is reminiscent of their cognate wild-type counterparts. Overall, our studies suggest a fundamental role for the TRL in shaping the intramolecular interactions implicated in the constitutive activation and coupling properties of the dopamine D1 receptor subtypes.
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Affiliation(s)
- R M Iwasiow
- Loeb Health Research Institute, Ottawa Hospital, Department of Medicine, University of Ottawa, Ottawa, Ontario K1Y 4K9, Canada
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44
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Hirabayashi T, Kume K, Hirose K, Yokomizo T, Iino M, Itoh H, Shimizu T. Critical duration of intracellular Ca2+ response required for continuous translocation and activation of cytosolic phospholipase A2. J Biol Chem 1999; 274:5163-9. [PMID: 9988766 DOI: 10.1074/jbc.274.8.5163] [Citation(s) in RCA: 138] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
When cells are exposed to certain external stimuli, arachidonic acid (AA) is released from the membrane and serves as a precursor of various types of eicosanoids. A Ca2+-regulated cytosolic phospholipase A2 (cPLA2) plays a dominant role in the release of AA. To closely examine the relation between Ca2+ response and AA release by stimulation of G protein-coupled receptors, we established several lines of Chinese hamster ovary cells expressing platelet-activating factor receptor or leukotriene B4 receptor. Measurement of intracellular Ca2+ concentration ([Ca2+]i) demonstrated that cell lines capable of releasing AA elicited a sustained [Ca2+]i increase when stimulated by agonists. The prolonged [Ca2+]i elevation is the result of Ca2+ entry, because this elevation was blocked by EGTA treatment or in the presence of Ca2+ channel blockers (SKF 96365 and methoxyverapamil). cPLA2 fused with a green fluorescent protein (cPLA2-GFP) translocated from the cytosol to the perinuclear region in response to increases in [Ca2+]i. When EGTA was added shortly after [Ca2+]i increase, the cPLA2-GFP returned to the cytosol, without liberating AA. After a prolonged [Ca2+]i increase, even by EGTA treatment, the enzyme was not readily redistributed to the cytosol. Thus, we propose that a critical time length of [Ca2+]i elevation is required for continuous membrane localization and full activation of cPLA2.
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Affiliation(s)
- T Hirabayashi
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Tokyo, Hongo, Toyko, Japan
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45
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Hirabayashi T, Kume K, Shimizu T. Conditional expression of the dual-specificity phosphatase PYST1/MKP-3 inhibits phosphorylation of cytosolic phospholipase A2 in Chinese hamster ovary cells. Biochem Biophys Res Commun 1998; 253:485-8. [PMID: 9878562 DOI: 10.1006/bbrc.1998.9807] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Stimulation of platelet-activating factor (PAF) receptor induces activation of extracellular signal-regulated kinase (ERK) and cytosolic phospholipase A2 (cPLA2) and release of arachidonic acid in Chinese hamster ovary cells. To determine whether the dual-specificity protein phosphatase PYST1/MKP-3 inhibits phosphorylation of cPLA2, we have generated a cell line that conditionally expresses PYST1 under the control of a tetracycline-regulated inducible system. We found that induction of PYST1 suppressed phosphorylation and activation of cPLA2 as well as ERK. Arachidonic acid release was also reduced by about 30%. Pretreatment of cells with an MEK inhibitor, PD98059, had similar effects on PAF-induced cPLA2 phosphorylation and arachidonic acid release. These experiments demonstrate that expression of PYST1 prevents phosphorylation of a cytoplasmic substrate for ERK. Thus, this inducible system may offer a valuable means of investigating physiological roles of ERK in vivo.
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Affiliation(s)
- T Hirabayashi
- Department of Biochemistry and Molecular Biology, University of Tokyo, Japan
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46
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Bläker M, Ren Y, Gordon MC, Hsu JE, Beinborn M, Kopin AS. Mutations within the cholecystokinin-B/gastrin receptor ligand 'pocket' interconvert the functions of nonpeptide agonists and antagonists. Mol Pharmacol 1998; 54:857-63. [PMID: 9804620 DOI: 10.1124/mol.54.5.857] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We have reported previously that the transmembrane domains of the cholecystokinin-B/gastrin receptor (CCK-BR) comprise a putative ligand binding pocket. In the present study, we examined whether amino acid substitutions within the CCK-BR pocket altered the affinities and/or functional activities of L-365,260 (the prototypical nonpeptide CCK-BR antagonist) and two structural derivatives, YM022 (a higher affinity antagonist) and L-740,093S (a partial agonist). Eight amino acids that project into the CCK-BR pocket were individually replaced by alanine, using site-directed mutagenesis. Affinities for the nonpeptide molecules, as well as ligand-induced inositol phosphate production, were assessed with the wild-type and mutant receptors. For each of the nonpeptide ligands examined, a distinct series of mutations altered the affinity, suggesting that each ligand possessed a characteristic pattern of interactions within the CCK-BR pocket. Basal signaling levels and inositol phosphate formation induced by the full agonist CCK octapeptide were comparable for the wild-type receptor and all of the mutant CCK-BR forms. In contrast to the peptide agonist CCK octapeptide, the functional activities of the nonpeptide molecules were selectively altered by single point mutations within the CCK-BR pocket, resulting in interconversion of agonists and antagonists. These findings suggest that interactions between nonpeptide molecules and transmembrane domain amino acids of the CCK-BR can determine the functional activity and affinity of the ligands.
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Affiliation(s)
- M Bläker
- Division of Gastroenterology and GRASP Digestive Disease Center, Tupper Research Institute, New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Ishii I, Izumi T, Ui M, Shimizu T. High and low affinity mutants of platelet-activating factor receptor. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1998; 433:249-53. [PMID: 9561146 DOI: 10.1007/978-1-4899-1810-9_53] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- I Ishii
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Tokyo, Japan
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Ishii I, Saito E, Izumi T, Ui M, Shimizu T. Agonist-induced sequestration, recycling, and resensitization of platelet-activating factor receptor. Role of cytoplasmic tail phosphorylation in each process. J Biol Chem 1998; 273:9878-85. [PMID: 9545329 DOI: 10.1074/jbc.273.16.9878] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Agonist-induced sequestration, recycling, and resensitization of platelet-activating factor (PAF) receptor were characterized in transfected Chinese hamster ovary cells. Exposure of the cells to PAF led to rapid sequestration of the receptors into the intracellular compartment and desensitization of the response to PAF. The sequestration was inhibited by pretreatments that perturbed the clathrin-mediated pathway. Subsequent removal of PAF by washing with receptor antagonists led to rapid recycling of the sequestered receptors to the cell surface accompanied by resensitization to PAF. To evaluate the potential role of phosphorylation in the receptor cytoplasmic tail during these processes, mutant receptors in which the tails were truncated or substituted, so as to lack serine/threonine residues, were created. PAF phosphorylated the wild-type receptor rapidly and strongly, but the mutants did not. The maximal extent of sequestration of each mutant was lower than that of the wild-type, and one of the substituted mutants showed no sequestration. Furthermore, the sequestration-defective mutant showed evidence of desensitization after agonist stimulation but not resensitization after agonist removal. Thus, agonist-induced phosphorylation of the cytoplasmic tail facilitates but is not essential for receptor sequestration, and sequestration/recycling appears important in receptor resensitization.
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Affiliation(s)
- I Ishii
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, The University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113, Japan
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Wonerow P, Schöneberg T, Schultz G, Gudermann T, Paschke R. Deletions in the third intracellular loop of the thyrotropin receptor. A new mechanism for constitutive activation. J Biol Chem 1998; 273:7900-5. [PMID: 9525885 DOI: 10.1074/jbc.273.14.7900] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Gain-of-function mutations of the thyrotropin receptor (TSHR) gene have been invoked as one of the major causes of toxic thyroid adenomas. In a toxic thyroid nodule, we recently identified a 9-amino acid deletion (amino acid positions 613-621) within the third intracellular (i3) loop of the TSHR resulting in constitutive receptor activity. This finding exemplifies a new mechanism of TSHR activation and raises new questions concerning the function of the i3 loop. Because the i3 loop is thought to be critical for receptor/G protein interaction in many receptors, we systematically reexamined the role of the TSHR's i3 loop for G protein coupling. Thus, various deletion mutants were generated and functionally characterized. We identified an optimal deletion length responsible for constitutive activity. If the number of deleted amino acids was reduced, elevated basal cAMP accumulation was found to be concomitantly diminished. Expansion of the deletion dramatically impaired cell surface expression of the receptor. Shifting the deletion toward the N terminus of the i3 loop resulted in unaltered strong constitutive receptor activity. In contrast, translocation of the deletion toward the C terminus led to significantly reduced basal cAMP formation, most probably due to destruction of a conserved cluster of amino acids. In this study, we show for the first time that amino acid deletions within the i3 loop of a G protein-coupled receptor result in constitutive receptor activity. In the TSHR, 75% of the i3 loop generally assumed to play an essential role in G protein coupling can be deleted without rendering the mutant receptor unresponsive to thyrotropin. These findings support a novel model explaining the molecular events accompanying receptor activation by agonist.
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Affiliation(s)
- P Wonerow
- Medizinische Klinik und Poliklinik III, Universität Leipzig, 04103 Leipzig, Germany
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Kume K, Shimizu T. Platelet-activating factor (PAF) induces growth stimulation, inhibition, and suppression of oncogenic transformation in NRK cells overexpressing the PAF receptor. J Biol Chem 1997; 272:22898-904. [PMID: 9278453 DOI: 10.1074/jbc.272.36.22898] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Platelet-activating factor (PAF) is a phospholipid mediator with various physiological functions, including cellular growth and transformation. PAF exerts biological activities through G-protein-coupled receptors. In normal rat fibroblasts overexpressing a cloned PAF receptor, PAF induced immediate early oncogene expression and mitogenic responses. On the other hand, PAF strongly inhibited the epidermal growth factor-induced mitogenic growth response, growth acceleration, and anchorage-independent cell growth in a soft agar. Furthermore, PAF suppressed v-src- or v-ras-induced oncogenic morphological changes and anchorage-independent growth. Our observations suggest that PAF is a unique growth regulator with apparently diverse functions. Dual actions of PAF may relate to the point of action in the cell cycle; PAF stimulates the mitogenic response in G0-arrested cells in a pertussis toxin-sensitive manner, while it inhibits the G1 to S transition through a pertussis toxin-resistant manner.
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Affiliation(s)
- K Kume
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, The University of Tokyo, Hongo, Bunkyo, Tokyo 113, Japan.
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