51
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Shemarova IV. cAMP-dependent signal pathways in unicellular eukaryotes. Crit Rev Microbiol 2009; 35:23-42. [PMID: 19514907 DOI: 10.1080/10408410802645646] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
The review summarizes current data about mechanisms of signal transduction with participation of cAMP (cyclic adenosine monophosphate) and elements of the complex cAMP-protein kinase A (PKA) signal pathway in unicellular eukaryotes. Conceptions of evolutionary origin of eukaryotic signal transduction systems are developed.
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Affiliation(s)
- Irina V Shemarova
- Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg, Russia.
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52
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Chen C, Li Z, Zhou Z, Yin Z, Chan SM, Yu XQ, Weng S, He J. Cloning, characterization and expression analysis of a CXCR1-like gene from mandarin fish Siniperca chuatsi. FISH PHYSIOLOGY AND BIOCHEMISTRY 2009; 35:489-499. [PMID: 19093223 DOI: 10.1007/s10695-008-9283-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2008] [Accepted: 10/16/2008] [Indexed: 05/27/2023]
Abstract
In this study we cloned and characterized a CXCR1-like gene (mfCXCR1) from mandarin fish (Siniperca chuatsi). The full-length cDNA of mfCXCR1 is 2,173 bp and contains a 1,056 bp open reading frame (ORF) that encodes a protein of 351 amino acids. The 5' and 3' untranslated regions (UTR) are 57 and 1,080 bp in length, respectively. The coding region of the mfCXCR1 gene consists of a single exon with a 734 bp intron that is two nucleotides upstream of the ATG start codon in the 5' UTR. The mfCXCR1 protein shares a relatively high identity with the CXCR1 and CXCR2 proteins of other fishes (approximately 50-65%). Furthermore, phylogenetic analysis indicates a close relatedness of mfCXCR1 to CXCR1 of other fishes. Many binding sites for stress-inducible transcription factors were present in the promoter region of the mfCXCR1 gene, indicating that it might be activated by certain stressors. The level of mfCXCR1 mRNA, when normalized to that in liver (1-fold), was highest in spleen (approximately 192.9-fold), with intermediate levels in kidney (approximately 163.2-fold), blood (approximately 131.2-fold) and head kidney (approximately 109.4-fold), and relatively low levels in intestine (approximately 34.4-fold) and gill (approximately 16.4-fold) (P < 0.05). Expression of mfCXCR1 during the clinical stage of infectious spleen and kidney necrosis virus (ISKNV) infection showed that its expression was regulated over the course of infection. On day 4 after ISKNV challenge, mfCXCR1 expression was down-regulated in blood (approximately 0.91-fold), spleen (approximately 0.26-fold), head kidney (approximately 0.18-fold) and kidney (approximately 0.82-fold).
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Affiliation(s)
- Chao Chen
- State Key Laboratory for Biocontrol, School of Life Sciences, Sun Yat-Sen University, 135 Xingang Road West, Guangzhou, 510275, People's Republic of China
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53
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Qiu JD, Huang JH, Liang RP, Lu XQ. Prediction of G-protein-coupled receptor classes based on the concept of Chou’s pseudo amino acid composition: An approach from discrete wavelet transform. Anal Biochem 2009; 390:68-73. [DOI: 10.1016/j.ab.2009.04.009] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2009] [Revised: 03/27/2009] [Accepted: 04/06/2009] [Indexed: 10/20/2022]
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54
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Dhillon SS, Gingerich S, Belsham DD. Neuropeptide Y induces gonadotropin-releasing hormone gene expression directly and through conditioned medium from mHypoE-38 NPY neurons. ACTA ACUST UNITED AC 2009; 156:96-103. [PMID: 19371763 DOI: 10.1016/j.regpep.2009.04.005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2009] [Revised: 03/10/2009] [Accepted: 04/05/2009] [Indexed: 11/16/2022]
Abstract
Neuropeptide Y (NPY) regulates reproductive function at the level of the hypothalamus through control of GnRH secretion. However, the direct control of GnRH gene expression by NPY has not yet been studied. GT1-7 neurons were treated with 100 nM of NPY over a 36 h time course. GnRH mRNA levels were significantly increased by NPY up to 12 h. We determined that GT1-7 neurons expressed Y1, Y2, and Y4 NPY receptors, but not Y5. Functional analysis of NPY receptor activation indicated that the Y1/Y4/Y5 receptor agonist [Leu31, Pro34] significantly induced cAMP accumulation in the GT1-7 neurons. Western blot studies demonstrated changes in the phosphorylation status of AKT, ERK1/2, CREB and ATF-1 after NPY exposure. Pharmacological inhibitors of the MAPK and PKA signal transduction pathways attenuated the NPY-mediated increase in GnRH transcription. This NPY-mediated increase in GnRH mRNA was also inhibited with the Y1-receptor specific antagonist BIBP-3226. The mHypoE-38 neurons secrete detectable levels of NPY and can be used as an endogenous source of NPY. Conditioned medium from mHypoE-38 neurons induced an increase in GnRH mRNA, which was inhibited by the Y1 receptor antagonist BIBP-3226. Together, these studies strengthen the evidence for the importance of NPY in the regulation of reproductive function.
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Affiliation(s)
- Sandeep S Dhillon
- Department of Physiology, University of Toronto, Medical Sciences Building 3247A, 1 Kings College Circle, Toronto, ON, Canada M5S 1A8
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55
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Abstract
Deciphering olfactory encoding requires a thorough description of the ligands that activate each odorant receptor (OR). In mammalian systems, however, ligands are known for fewer than 50 of more than 1400 human and mouse ORs, greatly limiting our understanding of olfactory coding. We performed high-throughput screening of 93 odorants against 464 ORs expressed in heterologous cells and identified agonists for 52 mouse and 10 human ORs. We used the resulting interaction profiles to develop a predictive model relating physicochemical odorant properties, OR sequences, and their interactions. Our results provide a basis for translating odorants into receptor neuron responses and for unraveling mammalian odor coding.
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Affiliation(s)
- Harumi Saito
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
| | - Qiuyi Chi
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
| | - Hanyi Zhuang
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
| | - Hiro Matsunami
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
- Department of Neurobiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
| | - Joel D. Mainland
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Research Drive, Durham NC 27710, USA
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56
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Ho SC, Goh SS, Li S, Khoo DHC, Paterson M. Effects of mutations involving cysteine residues distal to the S281HCC motif at the C-terminus on the functional characteristics of a truncated ectodomain-only thyrotropin receptor anchored on glycosylphosphatidyl-inositol. Thyroid 2008; 18:1313-9. [PMID: 18976165 DOI: 10.1089/thy.2008.0240] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
BACKGROUND Cysteine (Cys) residues pair to form disulfide bonds that are important in maintaining structure and function of the thyrotropin receptor (TSHR). There are 11 Cys residues in the ectodomain (ECD). Cys 41 at the N-terminus and Cys 283 at the SHCC motif have been identified as important for ligand binding. The present study evaluated the effects of mutating Cys distal to the S281HCC motif at the C-terminus of the ECD on the functional characteristics of TSHR. METHODS We introduced (i) individual Cys and (ii) consecutive cumulative Cys mutations into the starting template SHCS-TSHR, a truncated TSHR-ECD moiety previously shown to behave like the wild-type TSHR. Each mutant receptor was evaluated for relative specific binding (RSB), calculated as a measure of TSH-binding ability after normalization with receptor surface expression. RESULTS In the first approach, RSB was severely affected when Cys 390 and Cys 398 were individually switched to serine. Failed receptor trafficking occurred with Cys 408 mutation. These findings were likely results of altered receptor conformation due to illegitimate disulfide bridge formation. Only SHCS-301 TSHR bound TSH in a specific manner, and it formed the base for sequential Cys mutations. Through this second approach, both Cys 301 and 390 could be removed simultaneously without hindering TSH binding significantly. Cys 398, however, was shown to be critical. Its absence resulted in huge loss of TSH binding. Leaving Cys 283 and 398 as the only Cys pair in the C-terminus alone could support 40% of the total ligand-binding capacity. CONCLUSIONS From these data, we proposed Cys 398 as a stable disulfide bond partner of Cys 283, corroborating with a model based on evolutionary history of TSHR across species. This pairing of Cys 283 and Cys 398 also provides an objective alternative to conventional hypotheses on Cys coupling based on other predictive models.
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Affiliation(s)
- Su-Chin Ho
- SingHealth Research, Singapore Health Service, Singapore, Republic of Singapore.
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57
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Mechaly AS, Viñas J, Piferrer F. Identification of two isoforms of the Kisspeptin-1 receptor (kiss1r) generated by alternative splicing in a modern teleost, the Senegalese sole (Solea senegalensis). Biol Reprod 2008; 80:60-9. [PMID: 18815354 DOI: 10.1095/biolreprod.108.072173] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The KISSPEPTIN-1 receptor (KISS1R) and its ligands (KISSPEPTINS) are implicated in the regulation of the onset of puberty. We report the coding region and genomic structure of the kiss1r gene of a modern teleost, the Senegalese sole (Ss). Ss kiss1r cDNA contained an opening frame of 1137 bp, which results in a predicted 378 amino acid protein. Searching genomic databases allowed the identification of kiss1r orthologues in six new species belonging to three vertebrate groups and established the evolutionary relationships of all KISS1R sequences available to date. Analysis of Ss kiss1r revealed for the first time in any vertebrate KISS1R gene the presence of features that are characteristic of a mechanism of alternative splicing. This was confirmed by the identification of two transcripts, Ss kiss1r_v1 and Ss kiss1r_v2. The latter, arising from intron III retention, contained a 27 codons insert in transmembrane region 4 with two stop codons, suggesting it may lead to a truncated protein. The mRNA of the two variants was differently expressed in several tissues. In the brain, levels of the Ss kiss1r_v1 were higher than those of Ss kiss1r_v2. In the gonads, the opposite was observed. Both isoforms exhibited changes depending on sex and maturity stage. The presence of two variants may help to explain some discrepancies observed in past studies regarding KISS1R expression during puberty. Thus, the existence of alternative splicing for the KISS1R gene may contribute to our understanding of the many physiological functions suspected to be mediated by KISSPEPTIN-KISS1R signaling.
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Affiliation(s)
- Alejandro S Mechaly
- Institut de Ciències del Mar, Consejo Superior de Investigaciones Científicas (CSIC), 08003 Barcelona, Spain
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58
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Co-evolving stability and conformational homogeneity of the human adenosine A2a receptor. Proc Natl Acad Sci U S A 2008; 105:10744-9. [PMID: 18664584 DOI: 10.1073/pnas.0804396105] [Citation(s) in RCA: 180] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Structural studies on mammalian integral membrane proteins have long been hampered by their instability in detergent. This is particularly true for the agonist conformation of G protein-coupled receptors (GPCRs), where it is thought that the movement of helices that occurs upon agonist binding results in a looser and less stable packing in the protein. Here, we show that mutagenesis coupled to a specific selection strategy can be used to stabilize the agonist and antagonist conformations of the adenosine A(2a) receptor. Of the 27 mutations identified that improve the thermostability of the agonist conformation, only three are also present in the 17 mutations identified that improve the thermostability of the antagonist conformation, suggesting that the selection strategies used were specific for each conformation. Combination of the stabilizing mutations for the antagonist- or agonist-binding conformations resulted in mutants that are more stable at higher temperatures than the wild-type receptor by 17 degrees C and 9 degrees C, respectively. The mutant receptors both showed markedly improved stability in short-chain alkyl-glucoside detergents compared with the wild-type receptor, which will facilitate their structural analysis.
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59
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Grus WE, Zhang J. Distinct evolutionary patterns between chemoreceptors of 2 vertebrate olfactory systems and the differential tuning hypothesis. Mol Biol Evol 2008; 25:1593-601. [PMID: 18460446 DOI: 10.1093/molbev/msn107] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Most tetrapod vertebrates have 2 olfactory systems, the main olfactory system (MOS) and the vomeronasal system (VNS). According to the dual olfactory hypothesis, the MOS detects environmental odorants, whereas the VNS recognizes intraspecific pheromonal cues. However, this strict functional distinction has been blurred by recent reports that both systems can perceive both types of signals. Studies of a limited number of receptors suggest that MOS receptors are broadly tuned generalists, whereas VNS receptors are narrowly tuned specialists. However, whether this distinction applies to all MOS and VNS receptors remains unknown. The differential tuning hypothesis predicts that generalist MOS receptors detect an overlapping set of ligands and thus are more likely to be conserved over evolutionary time than specialist VNS receptors, which would evolve in a more lineage-specific manner. Here we test this prediction for all olfactory chemoreceptors by examining the evolutionary patterns of MOS-expressed odorant receptors (ORs) and trace amine-associated receptors (TAARs) and VNS-expressed vomeronasal type 1 receptors (V1Rs) and vomeronasal type 2 receptors (V2Rs) in 7 tetrapods (mouse, rat, dog, opossum, platypus, chicken, and frog). The phylogenies of V1Rs and V2Rs show abundant lineage-specific gene gains/losses and virtually no one-to-one orthologs between species. Opposite patterns are found for ORs and TAARs. Analysis of functional data and ligand-binding sites of ORs confirms that paralogous chemoreceptors are more likely than orthologs to have different ligands and that functional divergence between paralogous chemoreceptors is established relatively quickly following gene duplication. Together, these results strongly suggest that the functional profile of the VNS chemoreceptor repertoire evolves much faster than that of the MOS chemoreceptor repertoire and that the differential tuning hypothesis applies to the majority, if not all, of MOS and VNS receptors.
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Affiliation(s)
- Wendy E Grus
- Department of Ecology and Evolutionary Biology, University of Michigan, USA
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60
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Chaturvedi K, Sarkar DK. Alteration in G proteins and prolactin levels in pituitary after ethanol and estrogen treatment. Alcohol Clin Exp Res 2008; 32:806-13. [PMID: 18336630 PMCID: PMC2869483 DOI: 10.1111/j.1530-0277.2008.00638.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Chronic administration of ethanol increases plasma prolactin levels and enhances estradiol's mitogenic action on the lactotropes of the pituitary gland. The present study was conducted to determine the changes in the pituitary levels of G proteins during the tumor development following alcohol and ethanol treatments. METHODS Using ovariectomized Fischer-344 female rats, we have determined ethanol and estradiol actions at 2 and 4 weeks on pituitary weight and pituitary cell contents of prolactin, Gs. Gq11, Gi1, Gi2, and Gi3 proteins. Western blots were employed to measure protein contents. RESULTS Ethanol increased basal and estradiol-enhanced wet weight and the prolactin content in the pituitary in a time-dependent manner. Chronic exposure of estradiol increased the levels of Gs protein in the pituitary. Unlike estradiol, ethanol exposure did not show significant effect on the basal level of Gs protein, but moderately increased the estradiol-induced levels of this protein. Estradiol exposure enhanced Gq11 protein levels in the pituitary after 2 and 4 weeks, while ethanol treatment failed to alter these protein levels in the pituitary in control-treated or estradiol-treated ovariectomized rats. In the case of Gi1, estradiol but not ethanol increased the level of this protein at 4 weeks of treatment. However, estradiol and ethanol alone reduced the levels of both Gi2 and Gi3 proteins at 2 and 4 weeks of treatment. Ethanol also significantly reduced the estradiol-induced Gi2 levels at 4 weeks and Gi3 level at 2 and 4 weeks. CONCLUSIONS These results confirm ethanol's and estradiol's growth-promoting and prolactin stimulating actions on lactotropes of the pituitary and further provide evidence that ethanol and estradiol may control lactotropic cell functions by altering expression of specific group of G proteins in the pituitary.
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Affiliation(s)
- Kirti Chaturvedi
- Endocrine Program, Center of Alcohol Studies and Department of Animal Sciences, Rutgers, The State University of New Jersey, New Brunswick, New Jersey, USA
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61
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Silvestri R, Cascio MG, La Regina G, Piscitelli F, Lavecchia A, Brizzi A, Pasquini S, Botta M, Novellino E, Di Marzo V, Corelli F. Synthesis, Cannabinoid Receptor Affinity, and Molecular Modeling Studies of Substituted 1-Aryl-5-(1H-pyrrol-1-yl)-1H-pyrazole-3-carboxamides. J Med Chem 2008; 51:1560-76. [DOI: 10.1021/jm070566z] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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62
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Mah TL, Szundi I, Lewis JW, Jager S, Kliger DS. The Effects of Octanol on the Late Photointermediates of Rhodopsin. Photochem Photobiol 2008. [DOI: 10.1111/j.1751-1097.1998.tb02542.x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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63
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Cappellacci L, Franchetti P, Vita P, Petrelli R, Lavecchia A, Costa B, Spinetti F, Martini C, Klotz KN, Grifantini M. 5′-Carbamoyl derivatives of 2′-C-methyl-purine nucleosides as selective A1 adenosine receptor agonists: Affinity, efficacy, and selectivity for A1 receptor from different species. Bioorg Med Chem 2008; 16:336-53. [DOI: 10.1016/j.bmc.2007.09.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2007] [Revised: 09/11/2007] [Accepted: 09/19/2007] [Indexed: 10/22/2022]
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64
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Bell GI, Yasuda K, Kong H, Law SF, Raynor K, Reisine T. Molecular biology of somatostatin receptors. CIBA FOUNDATION SYMPOSIUM 2007; 190:65-79; discussion 80-8. [PMID: 7587653 DOI: 10.1002/9780470514733.ch5] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The diverse physiological effects of somatostatin are mediated by a family of cell surface receptors that bind somatostatin selectively and with high affinity. The somatostatin receptors are members of the seven transmembrane segment receptor superfamily and molecular cloning studies have identified five types, designated sstr1-5. The human somatostatin receptors vary in size from 364 (sstr5) to 418 (sstr3) amino acids with 46-61% amino acid identity between receptors, and 105 amino acids are invariant. The sequences of the seven putative alpha-helical membrane-spanning domains are more highly conserved than those of the extracellular N- and intracellular C-terminal domains. Two forms of sstr2 have been identified in the mouse, sstr2A and sstr2B, which differ in size and sequence of the intracellular C-terminal domain. These two forms of sstr2 are products of a common gene and are generated by alternative splicing with sstr2A and sstr2B being the products of the unspliced and spliced forms, respectively, of sstr2 mRNA. Thus, functional diversity within the somatostatin receptor family may result from the expression of multiple types as well as from alternative splicing. The five somatostatin receptors have distinct patterns of expression in the central nervous system and peripheral tissues. They have also been expressed in vitro and shown to have different pharmacological properties. Somatostatin analogues selective for sstr2, sstr3 and sstr5 have been identified which will facilitate in vivo studies of the functions of these somatostatin receptors. Such studies to date suggest that sstr2 mediates inhibition of growth hormone secretion and sstr5 mediates inhibition of insulin secretion. The molecular cloning and functional characterization of the somatostatin receptor family is a first step in elucidating the diverse effects of somatostatin on cellular functions.
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Affiliation(s)
- G I Bell
- Howard Hughes Medical Institute, University of Chicago, IL 60637, USA
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65
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D'Andrea P, Romanello M, Bicego M, Steinberg TH, Tell G. H(2)O(2) modulates purinergic-dependent calcium signalling in osteoblast-like cells. Cell Calcium 2007; 43:457-68. [PMID: 17825906 DOI: 10.1016/j.ceca.2007.07.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2007] [Revised: 07/02/2007] [Accepted: 07/28/2007] [Indexed: 10/22/2022]
Abstract
Reactive oxygen species (ROS) have long been considered as toxic by-products of aerobic metabolism and appear involved in the pathogenesis of degenerative diseases. The physiological role of ROS as second messengers in cell signal transduction is, on the other hand, increasingly recognized. Here we investigated the effects of H(2)O(2) and extracellular nucleotides on calcium signalling in four osteoblastic cell lines. In the highly differentiated HOBIT cells, sensitive to nanomolar concentrations of ADP and UTP, millimolar H(2)O(2) induced oscillatory increases of the cytosolic calcium concentration followed by a steady and sustained calcium increase. Long lasting rhythmic calcium activity was induced by micromolar H(2)O(2) doses. The H(2)O(2)-induced calcium signals, due to both release from intracellular stores and influx from the extracellular milieu, were totally prevented by incubating the cells with the P2 receptor antagonist suramin or with the ATP/ADP hydrolyzing enzyme apyrase. In the osteosarcoma SaOS-2 cells micromolar H(2)O(2) failed to evoke calcium signals and millimolar H(2)O(2) induced a slowly developing calcium influx which was unaffected by suramin and apyrase. These cells responded to micromolar concentrations of ATP and ADP, but were largely insensitive to UTP. ROS 17/2.8 osteosarcoma cells were totally insensitive to ATP, ADP and UTP in keeping with the evidence that these cells lack functional purinergic receptors. In these cells, H(2)O(2) up to 1mM did not increase the cytosolic calcium concentration. In ROS/P2Y(2) cells, stably expressing the P2Y(2) receptor, spontaneous calcium oscillations were observed in 38% of the population and nanomolar concentration of extracellular ATP or UTP activated oscillations in quiescent cells. Spontaneous calcium signals were inhibited by suramin and apyrase. In these cells H(2)O(2) induced oscillatory calcium activity that was blocked by suramin and apyrase. The sensitivity of ROS/P2Y(2) cells to UTP decreased significantly in the presence of DTT, which was effective also in inhibiting spontaneous calcium oscillations. On the other hand, the membrane-impermeant thiol oxidant DTNB induced calcium oscillations that were inhibited by incubating the cells with suramin or apyrase. Since peroxide did not increase extracellular ATP in these cell lines, we propose that, in osteoblasts, mild oxidative conditions could activate purinergic signalling through the sensitization of P2Y(2) receptor.
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Affiliation(s)
- Paola D'Andrea
- Dipartimento di Biochimica, Biofisica e Chimica delle Macromolecole, Università degli Studi di Trieste, Trieste, Italy.
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66
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Blakeney JS, Reid RC, Le GT, Fairlie DP. Nonpeptidic Ligands for Peptide-Activated G Protein-Coupled Receptors. Chem Rev 2007; 107:2960-3041. [PMID: 17622179 DOI: 10.1021/cr050984g] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Jade S Blakeney
- Centre for Drug Design and Development, Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland 4072, Australia
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67
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Eo HS, Choi JP, Noh SJ, Hur CG, Kim W. A combined approach for the classification of G protein-coupled receptors and its application to detect GPCR splice variants. Comput Biol Chem 2007; 31:246-56. [PMID: 17631418 DOI: 10.1016/j.compbiolchem.2007.05.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Accepted: 05/07/2007] [Indexed: 11/22/2022]
Abstract
G protein-coupled receptors (GPCRs) constitute the largest family of cell surface receptors and play a central role in cellular signaling pathways. The importance of GPCRs has led to their becoming the targets of more than 50% of prescription drugs. However, drug compounds that do not differentiate between receptor subtypes can have considerable side effects and efficacy problems. An accurate classification of GPCRs can solve the side effect problems and raise the efficacy of drugs. Here, we introduce an approach that combines a fingerprint method, statistical profiles and physicochemical properties of transmembrane (TM) domains for a highly accurate classification of the receptors. The approach allows both the recognition and classification for GPCRs at the subfamily and subtype level, and allows the identification of splice variants. We found that the approach demonstrates an overall accuracy of 97.88% for subfamily classification, and 94.57% for subtype classification.
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Affiliation(s)
- Hae-Seok Eo
- School of Biological Sciences, Seoul National University, Seoul 151-742, Republic of Korea
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68
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Schrader T, Maue M, Ellermann M. Entirely artificial signal transduction with adrenaline. J Recept Signal Transduct Res 2007; 26:473-85. [PMID: 17118794 DOI: 10.1080/10799890600950545] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Multifunctional transmembrane-building blocks with recognition sites for adrenaline on one end and the reaction partners for an SN2 reaction on the opposite end have been embedded in DPPC-liposomes. These doped vesicles can be quantitatively reduced at their disulfide head groups by externally added reducing agents; their composition and chemical processes taking place within can be monitored by NMR spectroscopy and--with limitations--by UV/Vis spectroscopy. Attempted release of thiopyridine as a second messenger into the interior of the liposome on external adrenaline addition could not be proven unambiguously because the detection system does not fulfill the necessary rigorous specificity and sensitivity requirements.
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Affiliation(s)
- Thomas Schrader
- Department of Chemistry, Philipps University of Marburg, Marburg, Germany.
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69
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Genomic organization and sequence analysis of the vomeronasal receptor V2R genes in mouse genome. ACTA ACUST UNITED AC 2007. [DOI: 10.1007/s11434-007-0059-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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70
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Rajagopalan L, Rajarathnam K. Structural basis of chemokine receptor function--a model for binding affinity and ligand selectivity. Biosci Rep 2006; 26:325-39. [PMID: 17024562 PMCID: PMC2671010 DOI: 10.1007/s10540-006-9025-9] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Chemokine receptors play fundamental roles in human physiology from embryogenesis to inflammatory response. The receptors belong to the G-protein coupled receptor class, and are activated by chemokine ligands with a range of specificities and affinities that result in a complicated network of interactions. The molecular basis for function is largely a black box, and can be directly attributed to the lack of structural information on the receptors. Studies to date indicate that function can be best described by a two-site model, that involves interactions between the receptor N-domain and ligand N-terminal loop residues (site-I), and between receptor extracellular loop and the ligand N-terminal residues (site-II). In this review, we describe how the two-site model could modulate binding affinity and ligand selectivity, and also highlight some of the unique chemokine receptor features, and their role in function.
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Affiliation(s)
- Lavanya Rajagopalan
- Department of Biochemistry and Molecular Biology and Sealy Center for Structural Biology, The University of Texas Medical Branch, Galveston, TX 77555-1055, USA, e-mail:
| | - Krishna Rajarathnam
- Department of Biochemistry and Molecular Biology and Sealy Center for Structural Biology, The University of Texas Medical Branch, Galveston, TX 77555-1055, USA, e-mail:
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Thiagaraj HV, Ortiz TC, Devereaux MC, Seaver B, Hall B, Parker KK. Regulation of G proteins by human 5-HT1a receptor TM3/i2 and TM5/i3 loop peptides. Neurochem Int 2006; 50:109-18. [PMID: 16973243 DOI: 10.1016/j.neuint.2006.07.017] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2006] [Accepted: 07/11/2006] [Indexed: 12/15/2022]
Abstract
A bioactive synthetic 11 amino acid peptide probe (P11) was constructed according to the published sequence of the human 5HT1a receptor. The probe was used to enhance understanding of cytoplasmic loop 2/G protein coupling and activation. Additionally, two peptides (P8, P9) from the cytoplasmic loop 3 region were synthesized and studied. These probes were tested in a model system of human 5HT1a receptor stably expressed in Chinese Hamster Ovary cells. In agonist inhibition studies, P11 was active in all three receptor preparations tested: whole cells, membrane bound, and solubilized. In analyses of the membrane bound receptor system, P11 demonstrated uncompetitive inhibition characteristics. When forskolin-stimulated cAMP levels were measured, P11 was inactive in this negatively coupled system. Utilizing a [35S]gamma-S-GTP incorporation assay, P11 was unable to stimulate G protein incorporation of GTP. While P8 and P9 were also broadly active as non-competitive agonist inhibitors, their characteristics differed in the signal transduction system. P8 and P9 did not significantly change forskolin-stimulated cAMP levels. However, P8 increased [35S]gamma-S-GTP incorporation, while P9 decreased incorporation. Thus, P11, a synthetic peptide from the TM3/i2 region of the receptor, provides suggestive evidence that this receptor region is involved in G protein coupling but not activation. On the other hand, P8 and P9 activities suggest that the TM5/i3 region is involved in both coupling to and regulation of G protein activity. The current evidence from these cytoplasmic loop regions is discussed in the overall context of an emerging model for human 5HT1a receptor-G protein interactions.
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Affiliation(s)
- Harish V Thiagaraj
- Department of Biomedical and Pharmaceutical Sciences (MPH I02), Skaggs School of Pharmacy, The University of Montana, 32 Campus Drive #1552, Missoula, MT 59812-1552, United States
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72
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Pucadyil TJ, Chattopadhyay A. Role of cholesterol in the function and organization of G-protein coupled receptors. Prog Lipid Res 2006; 45:295-333. [PMID: 16616960 DOI: 10.1016/j.plipres.2006.02.002] [Citation(s) in RCA: 225] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Cholesterol is an essential component of eukaryotic membranes and plays a crucial role in membrane organization, dynamics and function. The modulatory role of cholesterol in the function of a number of membrane proteins is well established. This effect has been proposed to occur either due to a specific molecular interaction between cholesterol and membrane proteins or due to alterations in the membrane physical properties induced by the presence of cholesterol. The contemporary view regarding heterogeneity in cholesterol distribution in membrane domains that sequester certain types of membrane proteins while excluding others has further contributed to its significance in membrane protein function. The seven transmembrane domain G-protein coupled receptors (GPCRs) are among the largest protein families in mammals and represent approximately 2% of the total proteins coded by the human genome. Signal transduction events mediated by this class of proteins are the primary means by which cells communicate with and respond to their external environment. GPCRs therefore represent major targets for the development of novel drug candidates in all clinical areas. In view of their importance in cellular signaling, the interaction of cholesterol with such receptors represents an important determinant in functional studies of such receptors. This review focuses on the effect of cholesterol on the membrane organization and function of GPCRs from a variety of sources, with an emphasis on the more contemporary role of cholesterol in maintaining a domain-like organization of such receptors on the cell surface. Importantly, the recently reported role of cholesterol in the function and organization of the neuronal serotonin(1A) receptor, a representative of the GPCR family which is present endogenously in the hippocampal region of the brain, will be highlighted.
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Affiliation(s)
- Thomas J Pucadyil
- Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad 500007, India
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73
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Mazna P, Berka K, Jelinkova I, Balik A, Svoboda P, Obsilova V, Obsil T, Teisinger J. Ligand binding to the human MT2 melatonin receptor: the role of residues in transmembrane domains 3, 6, and 7. Biochem Biophys Res Commun 2005; 332:726-34. [PMID: 15913560 DOI: 10.1016/j.bbrc.2005.05.017] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2005] [Accepted: 05/03/2005] [Indexed: 12/15/2022]
Abstract
To better understand the mechanism of interactions between G-protein-coupled melatonin receptors and their ligands, our previously reported homology model of human MT2 receptor with docked 2-iodomelatonin was further refined and used to select residues within TM3, TM6, and TM7 potentially important for receptor-ligand interactions. Selected residues were mutated and radioligand-binding assay was used to test the binding affinities of hMT2 receptors transiently expressed in HEK293 cells. Our data demonstrate that residues N268 and A275 in TM6 as well as residues V291 and L295 in TM7 are essential for 2-iodomelatonin binding to the hMT2 receptor, while TM3 residues M120, G121, V124, and I125 may participate in binding of other receptor agonists and/or antagonists. Presented data also hint at possible specific interaction between the side-chain of Y188 in second extracellular loop and N-acetyl group of 2-iodomelatonin.
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Affiliation(s)
- Petr Mazna
- Institute of Physiology, Academy of Sciences of the Czech Republic, Videnska 1083, 142 20 Prague, Czech Republic
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74
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Nelson LE, Sheridan MA. Regulation of somatostatins and their receptors in fish. Gen Comp Endocrinol 2005; 142:117-33. [PMID: 15862556 DOI: 10.1016/j.ygcen.2004.12.002] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 12/02/2004] [Accepted: 12/13/2004] [Indexed: 01/12/2023]
Abstract
The multifunctional nature of the somatostatin (SS) family of peptides results from a multifaceted signaling system consisting of many forms of SS peptides that bind to a variety of receptor (SSTR) subtypes. Research in fish has contributed important information about the components, function, evolution, and regulation of this system. Somatostatins or mRNAs encoding SSs have been isolated from over 20 species of fish. Peptides and deduced peptides differ in their amino acid chain length and/or composition, and most species of fish possess more than one form of SS. The structural heterogeneity of SSs results from differential processing of the hormone precursor, preprosomatostatin (PPSS), and from the existence of multiple genes that give rise to multiple PPSSs. The PPSS genes appear to have arisen through a series of gene duplication events over the course of vertebrate evolution. The numerous PPSSs of fish are differentially expressed, both in terms of the distribution among tissues and in terms of the relative abundance within a tissue. Accumulated evidence suggests that nutritional state, season/stage of sexual maturation, and many hormones [insulin (INS), glucagon, growth hormone (GH), insulin-like growth factor-I (IGF-I), and 17beta-estradiol (E2)] regulate the synthesis and release of particular SSs. Fish and mammals possess multiple SSTRs; four different SSTRs have been described in fish and several of these occur as isoforms. SSTRs are also wide spread and are differentially expressed, both in terms of distribution of tissues as well as in terms of relative abundance within tissues. The pattern of distribution of SSTRs may underlie tissue-specific responses of SSs. The synthesis of SSTR mRNA and SS-binding capacity are regulated by nutritional state and numerous hormones (INS, GH, IGF-I, and E2). Accumulated evidence suggests the possibility of both tissue- and subtype-specific mechanisms of regulation. In many instances, there appears to be coordinate regulation of PPSS and of SSTR; such regulation may prove important for many processes, including nutrient homeostasis and growth control.
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Affiliation(s)
- Laura E Nelson
- Department of Biological Sciences, North Dakota State University, Fargo, ND 58105, USA
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75
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Cappellacci L, Franchetti P, Pasqualini M, Petrelli R, Vita P, Lavecchia A, Novellino E, Costa B, Martini C, Klotz KN, Grifantini M. Synthesis, biological evaluation, and molecular modeling of ribose-modified adenosine analogues as adenosine receptor agonists. J Med Chem 2005; 48:1550-62. [PMID: 15743197 DOI: 10.1021/jm049408n] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A number of 3'-C-methyl analogues of selective adenosine receptor agonists such as CPA, CHA, CCPA, 2'-Me-CCPA, NECA, and IB-MECA was synthesized to further investigate the subdomain of the receptor that binds the ribose moiety of the ligands. Affinity data at A(1), A(2A), and A(3) receptors in bovine brain membranes showed that the 3'-C-modification in adenosine resulted in a decrease of the affinity at all three receptor subtypes. When this modification was combined with N(6)-substitution with groups that induce high potency and selectivity at A(1) receptor, the affinity and selectivity were increased. However, all 3'-C-methyl derivatives proved to be very less active than the corresponding 2'-C-methyl analogues. The most active compound was found to be 3'-Me-CPA which displayed a K(i) value of 0.35 microM at A(1) receptor and a selectivity for A(1) vs A(2A) and A(3) receptors higher than 28-fold. 2'-Me-CCPA was confirmed to be the most selective, high affinity agonist so far known also at human A(1) receptor with a K(i) value of 3.3 nM and 2903- and 341-fold selective vs human A(2A) and A(3) receptors, respectively. In functional assay, 3'-Me-CPA, 3'-Me-CCPA, and 2-Cl-3'-Me-IB-MECA inhibited forskolin-stimulated adenylyl cyclase activity with IC(50) values ranging from 0.3 to 4.9 microM, acting as full agonists. A rhodopsin-based model of the bovine A(1)AR was built to rationalize the higher affinity and selectivity of 2'-C-methyl derivatives of N(6)-substituted-adenosine compared to that of 3'-C-methyl analogues. In the docking exploration, it was found that 2'-Me-CCPA was able to form a number of interactions with several polar residues in the transmembrane helices TM-3, TM-6, and TM-7 of bA(1)AR which were not preserved in the molecular dynamics simulation of 3'-Me-CCPA/bA(1)AR complex.
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76
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Kim TK, Zhang R, Feng W, Cai J, Pierce W, Song ZH. Expression and characterization of human CB1 cannabinoid receptor in methylotrophic yeast Pichia pastoris. Protein Expr Purif 2005; 40:60-70. [PMID: 15721772 DOI: 10.1016/j.pep.2004.10.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2004] [Revised: 10/13/2004] [Indexed: 10/26/2022]
Abstract
For the purpose of purification and structural characterization, the CB1 cannabinoid receptors are expressed in methylotrophic yeast Pichia pastoris. The expression plasmid was constructed in which the CB1 gene is under the control of the highly inducible promoter of P. pastoris alcohol oxidase I gene. To facilitate easy detection and purification, a FLAG tag was introduced at the N-terminal, a c-myc epitope and a hexahistidine tag were introduced at the C-terminal of the CB1. In membrane preparations of CB1 gene transformed yeast cells, Western blot analysis detected the expression of CB1 proteins. Radioligand binding assays demonstrated that the tagged CB1 receptors expressed in P. pastoris have a pharmacological profile similar to that of the untagged CB1 receptors expressed in mammalian systems. Furthermore, the tagged CB1 receptors were purified by anti-FLAG M2 affinity chromatography and the identity of the purified CB1 receptor proteins was confirmed by Western blot analysis. MALDI/TOF mass spectrometry analysis of the peptides extracted from tryptic digestions of purified CB1 preparations detected 17 peptide fragments derived from the CB1, thus further confirming the identity of the purified receptor. In conclusion, these data demonstrated for the first time that epitope tagged, functional CB1 cannabinoid receptors can be expressed in P. pastoris for purification and mass spectrometry characterization.
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Affiliation(s)
- Tae-Kang Kim
- Department of Pharmacology and Toxicology, School of Medicine, University of Louisville, Louisville, KY 40292, USA
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77
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Lavecchia A, Cosconati S, Novellino E. Architecture of the Human Urotensin II Receptor: Comparison of the Binding Domains of Peptide and Non-Peptide Urotensin II Agonists. J Med Chem 2005; 48:2480-92. [PMID: 15801838 DOI: 10.1021/jm049110x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The human urotensin II receptor (h-UTR) is a member of the family of rhodopsin-like G-protein-coupled receptors (GPCRs) involved in the modulation of the functionality of many tissues and organs. Recently the urotensin-II (UII) neuropeptide, which is a potent vasoconstrictor in mammals and it is postulated to play a central role in cardiovascular homeostasis, has been identified as an agonist of the UII receptor. To elucidate the receptor's molecular recognition, a h-UTR model was constructed by homology modeling using the 2.6 A crystal structure of bovine rhodopsin as a template and subsequently refined by molecular dynamics simulations. The molecular recognition of h-UTR was probed by automated docking of P5U, a potent UII peptide agonist, as well as of the non-peptide compounds 1-4. We believe that this new model of the h-UTR provides the means for understanding the ligand's potency and for facilitating the design of novel and more potent UII ligands.
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Affiliation(s)
- Antonio Lavecchia
- Dipartimento di Chimica Farmaceutica e Tossicologica, Università di Napoli Federico II, Via D. Montesano 49, 80131 Napoli, Italy.
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78
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Datta A, Stone MJ. Soluble mimics of a chemokine receptor: chemokine binding by receptor elements juxtaposed on a soluble scaffold. Protein Sci 2004; 12:2482-91. [PMID: 14573861 PMCID: PMC2366953 DOI: 10.1110/ps.03254303] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Despite the broad biological importance of G protein-coupled receptors (GPCRs), ligand recognition by GPCRs remains poorly understood. To explore the roles of GPCR extracellular elements in ligand binding and to provide a tractable system for structural analyses of GPCR/ligand interactions, we have developed a soluble protein that mimics ligand recognition by a GPCR. This receptor analog, dubbed CROSS5, consists of the N-terminal and third extracellular loop regions of CC chemokine receptor 3 (CCR3) displayed on the surface of a small soluble protein, the B1 domain of Streptococcal protein G. CROSS5 binds to the CCR3 ligand eotaxin with a dissociation equilibrium constant of 2.9 +/- 0.8 microM and competes with CCR3 for eotaxin binding. Control proteins indicate that juxtaposition of both CCR3 elements is required for optimal binding to eotaxin. Moreover, the affinities of CROSS5 for a series of eotaxin mutants are highly correlated with the apparent affinities of CCR3 for the same mutants, demonstrating that CROSS5 uses many of the same interactions as does the native receptor. The strategy used to develop CROSS5 could be applied to many other GPCRs, with a variety of potential applications.
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Affiliation(s)
- Amita Datta
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-0001, USA
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79
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Han KH, Seo JA, Yu JH. A putative G protein-coupled receptor negatively controls sexual development in Aspergillus nidulans. Mol Microbiol 2004; 51:1333-45. [PMID: 14982628 DOI: 10.1111/j.1365-2958.2003.03940.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
G protein-coupled receptors (GPCRs) are key components of heterotrimeric G protein-mediated signalling pathways that detect environmental signals and confer rapid cellular responses. To broaden our understanding of signalling mechanisms in the filamentous fungus Aspergillus nidulans, intensive analyses of the Aspergillus nidulans genome have been carried out and nine genes (gprA approximately gprI) that are predicted to encode seven transmembrane spanning GPCRs have been identified. Six of nine putative GPCRs have been disrupted and the gprD gene was found to play a central role in coordinating hyphal growth and sexual development. Deletion of gprD (Delta gprD) causes extremely restricted hyphal growth, delayed conidial germination and uncontrolled activation of sexual development resulting in a small colony covered by sexual fruiting bodies. Genetic studies indicate that GprD may not signal through the FadA (G alpha)-protein kinase A (PKA) pathway. Elimination of sexual development rescues both growth and developmental abnormalities caused by Delta gprD, suggesting that the primary role of GprD is to negatively regulate sexual development. This is supported by the fact that environmental conditions inhibiting sexual development suppress growth defects of the Delta gprD mutant. We propose that the GprD-mediated signalling cascade negatively regulates sexual development, which is required for proper proliferation of A. nidulans.
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Affiliation(s)
- Kap-Hoon Han
- Department of Food Microbiology and Toxicology and Food Research Institute, Molecular and Environmental Toxicology Center, 1925 Willow Drive, University of Wisconsin, Madison, 53706, USA
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80
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Man O, Gilad Y, Lancet D. Prediction of the odorant binding site of olfactory receptor proteins by human-mouse comparisons. Protein Sci 2004; 13:240-54. [PMID: 14691239 PMCID: PMC2286516 DOI: 10.1110/ps.03296404] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Olfactory receptors (ORs) are a large family of proteins involved in the recognition and discrimination of numerous odorants. These receptors belong to the G-protein coupled receptor (GPCR) hyperfamily, for which little structural data are available. In this study we predict the binding site residues of OR proteins by analyzing a set of 1441 OR protein sequences from mouse and human. The central insight utilized is that functional contact residues would be conserved among pairs of orthologous receptors, but considerably less conserved among paralogous pairs. Using judiciously selected subsets of 218 ortholog pairs and 518 paralog pairs, we have identified 22 sequence positions that are both highly conserved among the putative orthologs and variable among paralogs. These residues are disposed on transmembrane helices 2 to 7, and on the second extracellular loop of the receptor. Strikingly, although the prediction makes no assumption about the location of the binding site, these amino acid positions are clustered around a pocket in a structural homology model of ORs, mostly facing the inner lumen. We propose that the identified positions constitute the odorant binding site. This conclusion is supported by the observation that all but one of the predicted binding site residues correspond to ligand-contact positions in other rhodopsin-like GPCRs.
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Affiliation(s)
- Orna Man
- Department of Molecular Genetics and the Crown Human Genome Center, The Weizmann Institute of Science, Rehovot 76100, Israel
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81
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Shim JY, Welsh WJ, Howlett AC. Homology model of the CB1 cannabinoid receptor: sites critical for nonclassical cannabinoid agonist interaction. Biopolymers 2004; 71:169-89. [PMID: 12767117 DOI: 10.1002/bip.10424] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Association of cannabimimetic compounds such as cannabinoids, aminoalkylindoles (AAIs), and arachidonylethanolamide (anandamide) with the brain cannabinoid (CB(1)) receptor activates G-proteins and relays signals to regulate neuronal functions. A CB(1) receptor homology model was constructed using the published x-ray crystal structure of bovine rhodopsin (Palczewski et al., Science, 2000, Vol. 289, pp. 739-745) in the conformation most likely to represent the "high-affinity" state for agonist binding to G-protein coupled receptors (GPCRs). A molecular docking approach that combined Monte Carlo and molecular dynamics simulations was used to identify the putative binding conformations of nonclassical cannabinoid agonists, including AC-bicyclic CP47497 and CP55940, and ACD-tricyclic CP55244. Placement of these ligands was based upon the assumption of a critical hydrogen bond between the A-ring OH and the side chain N of Lys192 in transmembrane helix 3. We evaluated two alternative binding conformations, C3-in and C3-out, denoting the directionality of the ligand C3 side chain within the receptor with respect to the inside or the outside of the cell. Assuming both the C3-in or C3-out conformation, the calculated ligand-receptor binding energy (DeltaE(bind)) was correlated with the experimentally observed binding affinity (K(i)) for a series of nonclassical cannabinoid agonists. The C3-in conformation was marginally better than the alternative C3-out conformation in predicting the rank order of the tested nonclassical cannabinoid analogs. Adopting the C3-in conformation due to the greater number of receptor interactions with known pharmacophoric elements of the ligand, key residues were identified comprising the presumed hydrophobic pocket that interacts with the C3 side chain of cannabinoid agonists. Key hydrogen bonds would form between both K3.28(192) and E(258) and the A-ring OH, and between Q(261) and the C-ring C-12 hydroxypropyl. In summary, the present study represents one of the first attempts to construct a homology model of the CB(1) cannabinoid receptor based upon the published bovine rhodopsin x-ray crystal structure and to elucidate the putative ligand binding site for nonclassical cannabinoid agonists. We postulated sites of the CB(1) receptor critical for the ligand interaction, including the hydrophobic pocket interacting with the key pharmacophoric moiety, the C3 side chain. More work is needed to delineate between two alternative (and possibly other) binding conformations of the nonclassical cannabinoid ligands within the CB(1) receptor. The present study provides a consistent framework for further investigation of the CB(1) receptor-ligand interaction and for the study of CB(1) receptor activation.
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Affiliation(s)
- Joong-Youn Shim
- Department of Basic Pharmaceutical Sciences, College of Pharmacy, University of South Carolina, Columbia, SC 29208, USA.
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82
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Gupte J, Cutler G, Chen JL, Tian H. Elucidation of signaling properties of vasopressin receptor-related receptor 1 by using the chimeric receptor approach. Proc Natl Acad Sci U S A 2004; 101:1508-13. [PMID: 14757815 PMCID: PMC341764 DOI: 10.1073/pnas.0308250100] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The identification of endogenous or surrogate ligands for orphan G protein-coupled receptors (GPCRs) represents one of the most important tasks in GPCR biology and pharmacology. The challenge lies in choosing an appropriate assay in the absence of ways to activate the receptor of interest. We investigated the signaling pathway for an orphan GPCR referred to here as vasopressin receptor-related receptor 1 (VRR1) by generating a chimeric receptor, V1a/VRR1. The engineered construct contained vasopressin V1a receptor with all three intracellular loops and C terminus replaced by those of VRR1. The chimera behaved like a typical GPCR when transiently and stably expressed in mammalian cell lines based on radioligand binding and receptor internalization studies. Upon arginine vasopressin stimulation, this chimeric receptor induced robust calcium mobilization and increase of adenylate cyclase activity. The observed signaling activities are through the activation of the chimera instead of endogenously expressed receptors, as single amino acid changes in the second transmembrane regions of the chimera drastically reduced receptor efficacy and potency. Our results suggest that VRR1 has dual signaling properties in coupling to both G(q) and G(S) pathways. Analysis of native VRR1 receptor signaling pathway by using a recently identified ligand for VRR1 confirmed this conclusion and therefore validated the utility of the chimeric receptor approach for signaling pathway identification.
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Affiliation(s)
- Jamila Gupte
- Tularik Inc., 1120 Veterans Boulevard, South San Francisco, CA 94080, USA
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83
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Corleto VD, Nasoni S, Panzuto F, Cassetta S, Delle Fave G. Somatostatin receptor subtypes: basic pharmacology and tissue distribution. Dig Liver Dis 2004; 36 Suppl 1:S8-16. [PMID: 15077906 DOI: 10.1016/j.dld.2003.11.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The heptahelical receptor superfamily constitutes the largest single family of transmembrane-signalling molecules that regulate a wide range of physiological processes. The five somatostatin receptors represent a distinct subgroup of this seven transmembrane receptor superfamily. They range in size from 356 to 391 amino acids with 39-57% protein identity between the subtypes with 100 residues strictly conserved among the somatostatin receptor sequences. A high grade of mRNA homology exists in somatostatin receptor subtypes cloned from different species. Following somatostatin receptor binding and functional activity studies, two alternative models of ligand-binding interaction have been hypothesised. One relies on the presence of a binding pocket within the receptor structure constituted by specific amino acids residues, the other denies the presence of such binding structures and suggests that it is the interaction of agonists with specific extracellular and/or transmembrane domains that determine stable receptor structure conformation. Somatostatin receptors, as, indeed, all G-protein-coupled receptors are able to regulate their responsiveness to agonist exposure. This agonist-specific regulation includes three main events, namely, desensitisation, receptor internalisation and receptor degradation. The cell expression of somatostatin receptor subtypes, at the mRNA level, has been characterised in rodent and in human organs with multiple subtype expression in brain and peripheral tissues.
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Affiliation(s)
- V D Corleto
- Department of Digestive and Liver Diseases, II School of Medicine and Surgery, University of La Sapienza, S. Andrea Hospital, Via di Grottarossa 1035, 00189 Rome, Italy.
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84
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Madabushi S, Gross AK, Philippi A, Meng EC, Wensel TG, Lichtarge O. Evolutionary trace of G protein-coupled receptors reveals clusters of residues that determine global and class-specific functions. J Biol Chem 2003; 279:8126-32. [PMID: 14660595 DOI: 10.1074/jbc.m312671200] [Citation(s) in RCA: 151] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G protein-coupled receptor (GPCR) activation mediated by ligand-induced structural reorganization of its helices is poorly understood. To determine the universal elements of this conformational switch, we used evolutionary tracing (ET) to identify residue positions commonly important in diverse GPCRs. When mapped onto the rhodopsin structure, these trace residues cluster into a network of contacts from the retinal binding site to the G protein-coupling loops. Their roles in a generic transduction mechanism were verified by 211 of 239 published mutations that caused functional defects. When grouped according to the nature of the defects, these residues sub-divided into three striking sub-clusters: a trigger region, where mutations mostly affect ligand binding, a coupling region near the cytoplasmic interface to the G protein, where mutations affect G protein activation, and a linking core in between where mutations cause constitutive activity and other defects. Differential ET analysis of the opsin family revealed an additional set of opsin-specific residues, several of which form part of the retinal binding pocket, and are known to cause functional defects upon mutation. To test the predictive power of ET, we introduced novel mutations in bovine rhodopsin at a globally important position, Leu-79, and at an opsin-specific position, Trp-175. Both were functionally critical, causing constitutive G protein activation of the mutants and rapid loss of regeneration after photobleaching. These results define in GPCRs a canonical signal transduction mechanism where ligand binding induces conformational changes propagated through adjacent trigger, linking core, and coupling regions.
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Affiliation(s)
- Srinivasan Madabushi
- Program in Structural and Computational Biology and Molecular Biophysics, Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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85
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Robas N, Mead E, Fidock M. MrgX2 is a high potency cortistatin receptor expressed in dorsal root ganglion. J Biol Chem 2003; 278:44400-4. [PMID: 12915402 DOI: 10.1074/jbc.m302456200] [Citation(s) in RCA: 182] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
MrgX2 is a recently identified orphan G-protein-coupled receptor whose ligand and physiological function were unknown. Here we describe cortistatin, a neuropeptide for which no specific receptor has been identified previously, as a high potency ligand at MrgX2. Cortistatin has several biological functions including roles in sleep regulation, locomotor activity, and cortical function. Using a "reverse pharmacology" approach, we have identified a number of additional cyclic peptide agonists for MrgX2, determined their rank order of potency, and demonstrated that this receptor has a pharmacological profile distinct from the other characterized members of the Mrg (Mas-related genes) family. In MrgX2-expressing cells, cortistatin-stimulated increases in intracellular Ca2+ but had no effect on basal or forskolin-stimulated cAMP levels, suggesting that this receptor is Gq-coupled. Immunohistochemical and quantitative PCR studies show MrgX2 to have a limited expression profile, both peripheral and within the central nervous system, with highest levels in dorsal root ganglion.
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Affiliation(s)
- Nicola Robas
- Department of Target Genomics, Pfizer Global Research and Development, Sandwich, Kent, CT13 N9J, United Kingdom
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86
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Krebs A, Edwards PC, Villa C, Li J, Schertler GFX. The three-dimensional structure of bovine rhodopsin determined by electron cryomicroscopy. J Biol Chem 2003; 278:50217-25. [PMID: 14514682 DOI: 10.1074/jbc.m307995200] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
G-protein-coupled receptors are integral membrane proteins that respond to environmental signals and initiate signal transduction pathways, which activate cellular processes. Rhodopsin, a well known member of the G-protein-coupled receptor family, is located in the disk membranes of the rod outer segment, where it is responsible for the visualization of dim light. Rhodopsin is the most extensively studied G-protein-coupled receptor, and knowledge about its structure serves as a template for other related receptors. We have gained detailed structural knowledge from the crystal structure (1), which was solved by x-ray crystallography in 2000 using three-dimensional crystals. Here we report a three-dimensional density map of bovine rhodopsin determined by electron cryomicroscopy of two-dimensional crystals with p22(1)2(1) symmetry. The usage of relatively small and disordered crystals made the process of structure determination challenging. Special attention was paid to the extraction of amplitudes and phases, since usable raw data were limited to a maximum tilt of 45 degrees. In the refinement process, an improved unbending procedure was applied. This led to a final resolution of 5.5 A in the membrane plane and approximately 13 A perpendicular to it, making our electron density map the most accurate map of a G-protein-coupled receptor currently available by electron microscopy. Most important is the information we gain about the center of the membrane plane and the orientation of the molecule relative to the bilayer. This information cannot be retrieved from the three-dimensional crystals. In our electron density map, all seven transmembrane helices were identified, and their arrangement is in agreement with the arrangement known from the crystal structure (1). In the retinal binding pocket, a density peak adjacent to helix 3 suggests the position of the beta-ionine ring of the chromophore, and in its vicinity several of the bigger amino acids can be identified.
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Affiliation(s)
- Angelika Krebs
- Medical Research Council, Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, United Kingdom.
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87
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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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88
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Kotecha SA, MacDonald JF. Signaling molecules and receptor transduction cascades that regulate NMDA receptor-mediated synaptic transmission. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2003; 54:51-106. [PMID: 12785285 DOI: 10.1016/s0074-7742(03)54003-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Affiliation(s)
- Suhas A Kotecha
- Department of Physiology, Faculty of Medicine, University of Toronto, Canadian Institute of Health Research Group, The Synapse, Toronto, Ontario, Canada M5S 1A8
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89
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Fredriksson R, Lagerström MC, Lundin LG, Schiöth HB. The G-protein-coupled receptors in the human genome form five main families. Phylogenetic analysis, paralogon groups, and fingerprints. Mol Pharmacol 2003; 63:1256-72. [PMID: 12761335 DOI: 10.1124/mol.63.6.1256] [Citation(s) in RCA: 1992] [Impact Index Per Article: 94.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The superfamily of G-protein-coupled receptors (GPCRs) is very diverse in structure and function and its members are among the most pursued targets for drug development. We identified more than 800 human GPCR sequences and simultaneously analyzed 342 unique functional nonolfactory human GPCR sequences with phylogenetic analyses. Our results show, with high bootstrap support, five main families, named glutamate, rhodopsin, adhesion, frizzled/taste2, and secretin, forming the GRAFS classification system. The rhodopsin family is the largest and forms four main groups with 13 sub-branches. Positions of the GPCRs in chromosomal paralogons regions indicate the importance of tetraploidizations or local gene duplication events for their creation. We also searched for "fingerprint" motifs using Hidden Markov Models delineating the putative inter-relationship of the GRAFS families. We show several common structural features indicating that the human GPCRs in the GRAFS families share a common ancestor. This study represents the first overall map of the GPCRs in a single mammalian genome. Our novel approach of analyzing such large and diverse sequence sets may be useful for studies on GPCRs in other genomes and divergent protein families.
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MESH Headings
- Chromosome Mapping
- GTP-Binding Proteins/classification
- GTP-Binding Proteins/genetics
- Genome, Human
- Humans
- Membrane Glycoproteins
- Membrane Proteins/classification
- Membrane Proteins/genetics
- Phylogeny
- Platelet Glycoprotein GPIb-IX Complex
- Receptors, Cell Surface/classification
- Receptors, Cell Surface/genetics
- Receptors, G-Protein-Coupled
- Receptors, Gastrointestinal Hormone/classification
- Receptors, Gastrointestinal Hormone/genetics
- Receptors, Glutamate/classification
- Receptors, Glutamate/genetics
- Rhodopsin/classification
- Rhodopsin/genetics
- Sequence Analysis, Protein
- Sequence Homology, Amino Acid
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Affiliation(s)
- Robert Fredriksson
- Department of Neuroscience, Biomedical Center, Box 593, 75 124 Uppsala, Sweden
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90
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Rashid M, Manivet P, Nishio H, Pratuangdejkul J, Rajab M, Ishiguro M, Launay JM, Nagatomo T. Identification of the binding sites and selectivity of sarpogrelate, a novel 5-HT2 antagonist, to human 5-HT2A, 5-HT2B and 5-HT2C receptor subtypes by molecular modeling. Life Sci 2003; 73:193-207. [PMID: 12738034 DOI: 10.1016/s0024-3205(03)00227-3] [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: 10/27/2022]
Abstract
The aim of the present study was to investigate the binding sites interactions and the selectivity of sarpogrelate to human 5-HT(2) receptor family (5-HT(2A), 5-HT(2B) and 5-HT(2C) receptor subtypes) using molecular modeling. Rhodopsin (RH) crystal structures were used as template to build structural models of the human serotonin-2A and -2C receptors (5-HT(2A)R, 5-HT(2C)R), whereas for 5-HT(2B)R, we used our previously published three-dimensional (3D) models based on bacteriorhodopsin (BR). Sarpogrelate, a novel 5-HT(2)R antagonist, was docked to the receptors. Molecular dynamics (MD) simulations produced the strongest interaction for 5-HT(2A)R/sarpogrelate complex. Upon binding, sarpogrelate constraints aromatic residues network (Trp(3.28), Phe(5.47), Trp(6.48), Phe(6.51), Phe(6.52) in 5-HT(2A)R; Phe(3.35), Phe(6.51), Trp(7.40) in 5-HT(2B)R; Trp(3.28), Phe(3.35), Phe(5.47), Trp(6.48), Phe(6.51), Phe(6.52) in 5-HT(2C)R) in a stacked configuration, preventing activation of the receptor. The models suggest that the structural origin of the selectivity of sarpogrelate to 5-HT(2A)R vs both 5-HT(2B)R and 5-HT(2C)R comes from the following results: (1) The tight interaction between the antagonist and the transmembrane domain (TMD) 3. Asp(3.32) neutralizes the cationic head and interacts simultaneously with carboxylic group hydrogen of the antagonist molecule. (2) Due to steric hindrance, Ser(5.46) (vs Ala(5.46) in 5HT(2B) and 5HT(2C)) prevents sarpogrelate to enter deeply inside the hydrophobic core of the helix bundle and to interact with Pro(5.50). (3) The side chain of Ile(4.56) (vs Ile(4.56) in 5HT(2B)R and Val(4.56) in 5HT(2C)R) constraints sarpogrelate to adjust its position by translating toward the strongly attractive Asp(3.32). These results are in good agreement with binding affinities (pKi) of sarpogrelate for 5-HT(2) receptor family expressed in transfected cell.
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Affiliation(s)
- Mamunur Rashid
- Department of Pharmacology, Niigata University of Pharmacy and Applied Life Sciences, 5-13-2 Kamishinei-cho, Japan
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91
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Nicastro G, Peri F, Franzoni L, de Chiara C, Sartor G, Spisni A. Conformational features of a synthetic model of the first extracellular loop of the angiotensin II AT1A receptor. J Pept Sci 2003; 9:229-43. [PMID: 12725244 DOI: 10.1002/psc.449] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The angiotensin II AT1A receptor belongs to the G-protein coupled receptors (GPCRs). Like other membrane proteins, GPCRs are not easily amenable to direct structure determination by the currently available methods. The peptide encompassing the putative first extracellular loop of AT1A (residues Thr88-Leu100, el1) has been synthesized along with a cyclic model where the linear peptide has been covalently linked to a template designed to keep the distance between the peptide termini as expected in the receptor. The conformational features of the two molecules have been studied using circular dichroism and NMR techniques. The region W94PFG97 forms a type-II beta-turn and undergoes a Trp-Pro peptide bond cis-trans isomerization in both peptides confirming that these characteristics are intrinsic to el1. In addition, the presence of the spacer seems to modulate the flexibility of the peptide.
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Affiliation(s)
- Giuseppe Nicastro
- Department of Experimental Medicine, Section of Chemistry and Structural Biochemistry, University of Parma, 43100 Parma, Italy
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92
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Yu CJ, Butt CM, Debski EA. Bidirectional modulation of visual plasticity by cholinergic receptor subtypes in the frog optic tectum. Eur J Neurosci 2003; 17:1253-65. [PMID: 12670313 PMCID: PMC2267905 DOI: 10.1046/j.1460-9568.2003.02557.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Cholinergic input to the optic tectum is necessary for visual map maintenance. To understand why, we examined the effects of activation of the different cholinergic receptor subtypes in tectal brain slices and determined whether the retinotectal map was affected by manipulations of their activity in vivo. Both alpha-bungarotoxin sensitive and insensitive nicotinic receptor agonists increased spontaneous postsynaptic currents (sPSCs) in a subpopulation of patch-clamped tectal cells; application of subtype selective receptor antagonists reduced nicotine-induced increases in sPSCs. Activation of alpha-bungarotoxin insensitive nicotinic receptors also induced substantial inward current in some cells. Muscarinic receptor mediated outward current responses were blocked by the M2-like muscarinic receptor antagonists himbacine or AF-DX 384 and mimicked by application of the M2-like agonist oxotremorine. A less frequently observed muscarinic response involving a change in sPSC frequency appeared to be mediated by M1-like muscarinic receptors. In separate experiments, pharmacological manipulation of cholinergic receptor subtype activation led to changes in the activity-dependent visual map created in the tectum by retinal ganglion cell terminals. Chronic exposure of the tectum to either alpha-bungarotoxin insensitive, alpha-bungarotoxin sensitive or M1-like receptor antagonists resulted in map disruption. However, treatment with the M2-like receptor antagonist, AF-DX 384, compressed the map. We conclude that nicotinic or M1-like muscarinic receptors control input to tectal cells while alpha-bungarotoxin insensitive nicotinic receptors and M2-like muscarinic receptors change tectal cell responses to that input. Blockade of the different cholinergic receptor subtypes can have opposing effects on map topography that are consistent with expected effects on tectal cell activity levels.
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Affiliation(s)
- Chuan-Jiang Yu
- Department of Biology, University of Kentucky, Lexington, Kentucky 40506-0225, USA
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93
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Tsukada S, Iwai M, Nishiu J, Itoh M, Tomoike H, Horiuchi M, Nakamura Y, Tanaka T. Inhibition of experimental intimal thickening in mice lacking a novel G-protein-coupled receptor. Circulation 2003; 107:313-9. [PMID: 12538434 DOI: 10.1161/01.cir.0000043804.29963.b4] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Vascular restenosis attributable to intimal thickening remains a major problem after percutaneous transluminal coronary angioplasty (PTCA). METHODS AND RESULTS Through differential-display analysis, we have identified a novel gene whose expression was increased after catheter injury of rabbit aorta. The gene that is expressed predominantly in vascular smooth muscle cells encodes a novel protein with 7 transmembrane domains, and we termed it ITR (intimal thickness-related receptor). The ITR sequence contains a motif common to the Rhodopsin-like GPCR (G-protein-coupled receptor) superfamily. In vivo analyses of this gene revealed that expression of ITR protein increased with intimal thickening induced by cuff placement around murine femoral artery. Furthermore, ITR-knockout mice were found to be resistant to this experimental intimal thickening. CONCLUSIONS ITR thus seems to be a novel receptor that may play a role in vascular remodeling and that may represent a good target for development of drugs in the prevention of vascular restenosis.
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MESH Headings
- Amino Acid Sequence
- Animals
- Aorta/metabolism
- Aorta/pathology
- Base Sequence
- COS Cells
- Cell Line
- Chromosomes, Human, Pair 13/genetics
- Constriction, Pathologic/genetics
- Constriction, Pathologic/pathology
- Constriction, Pathologic/prevention & control
- Disease Models, Animal
- Femoral Artery/metabolism
- Femoral Artery/pathology
- GTP-Binding Proteins/metabolism
- Gene Targeting
- Humans
- Immunohistochemistry
- Mice
- Mice, Knockout
- Molecular Sequence Data
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Organ Specificity
- RNA, Messenger/metabolism
- Rabbits
- Rats
- Receptors, Cell Surface/biosynthesis
- Receptors, Cell Surface/deficiency
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Tunica Intima/metabolism
- Tunica Intima/pathology
- Tunica Media/metabolism
- Tunica Media/pathology
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Affiliation(s)
- Shuichi Tsukada
- Laboratory of Molecular Medicine, Human Genome Center, Institute of Medical Science, University of Tokyo, Japan
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94
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Lewerenz J, Leypoldt F, Methner A. Degenerate suppression PCR identifies the beta2-adrenergic receptor as upregulated by neuronal differentiation. Gene Expr 2003; 11:105-16. [PMID: 12837041 PMCID: PMC5991142 DOI: 10.3727/000000003108749008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Communication between cells is necessary for the functioning of a multicellular organism. Cells process a large amount of information through G-protein-coupled receptors, and activation of this receptor class has been implicated in neuronal differentiation. In this study, we used a method based on PCR with degenerated primers to identify G-protein-coupled receptors regulated by retinoic acid-induced differentiation of the human teratocarcinoma cell line NTera-2/D1. Subtracted cDNA libraries and control cDNA served as templates in half-sided PCR with a forward degenerate primer based on a conserved sequence from human serotonergic, adrenergic, and dopaminergic receptors and reverse primers on adaptors with long terminal repeats commonly employed in subtractive suppression hybridization. We developed conditions to amplify G-protein-coupled receptors from adaptor-ligated cDNA and found the beta2-adrenergic receptor to be upregulated fourfold. This seems to be physiologically relevant, as it could also be shown in rat primary cortical cultures maturing in vitro. The method presented here makes use of the otherwise unused control cDNA from subtractive suppression hybridization experiments and could be easily adapted to other gene families.
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MESH Headings
- Animals
- Blotting, Northern
- Cell Differentiation/physiology
- Cerebral Cortex/metabolism
- Cerebral Cortex/pathology
- DNA Primers/chemistry
- DNA, Complementary/genetics
- DNA, Complementary/metabolism
- Humans
- Neurons/cytology
- Neurons/metabolism
- Neurons/pathology
- Polymerase Chain Reaction
- Rats
- Rats, Wistar
- Receptors, Adrenergic, beta/genetics
- Receptors, Adrenergic, beta/metabolism
- Receptors, G-Protein-Coupled/genetics
- Subtraction Technique
- Teratocarcinoma/metabolism
- Teratocarcinoma/pathology
- Tumor Cells, Cultured
- Up-Regulation
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Affiliation(s)
- Jan Lewerenz
- Research Group Protective Signaling, Zentrum für Molekulare Neurobiologie and Department of Neurology, University Hospital Hamburg, Martinistr. 52, D-20246 Hamburg, Germany
| | - Frank Leypoldt
- Research Group Protective Signaling, Zentrum für Molekulare Neurobiologie and Department of Neurology, University Hospital Hamburg, Martinistr. 52, D-20246 Hamburg, Germany
| | - Axel Methner
- Research Group Protective Signaling, Zentrum für Molekulare Neurobiologie and Department of Neurology, University Hospital Hamburg, Martinistr. 52, D-20246 Hamburg, Germany
- Address correspondence to Axel Methner, Research Group Protective Signaling, Zentrum für Molekulare Neurobiologie Hamburg and Department of Neurology, University Hospital Hamburg, Martinistr. 52, D-20246 Hamburg, Germany. Tel: +49 40 4 28 03 66 26; Fax: +49 40 4 28 03 51 01; E-mail:
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95
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Pfleger KDG, Eidne KA. New technologies: bioluminescence resonance energy transfer (BRET) for the detection of real time interactions involving G-protein coupled receptors. Pituitary 2003; 6:141-51. [PMID: 14974443 DOI: 10.1023/b:pitu.0000011175.41760.5d] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The natural phenomenon of bioluminescence resonance energy transfer (BRET) has become an extremely useful tool for studying protein-protein interactions in the laboratory, including those involving G-protein coupled receptors (GPCRs). The technology involves fusion of donor and acceptor molecules to proteins of interest. Following assessment to ensure correct functionality, co-expression of fusion constructs in live cells enables their interaction to be studied in real time in a quantitative manner. Energy is transferred from the donor to the acceptor when in close proximity, resulting in fluorescence emission at a characteristic wavelength. The energy emitted by the acceptor relative to that emitted by the donor is termed the BRET signal. It is dependent upon the spectral properties, ratio, distance and relative orientation of the donor and acceptor molecules, as well as the strength and stability of the interaction between the proteins of interest. The ability to study interactions in live mammalian cells circumvents many of the problems associated with techniques such as co-immunoprecipitation and yeast two-hybrid screening. Furthermore, the high sensitivity of BRET enables the study of proteins at physiological concentrations, a significant advantage over techniques that require high levels of protein expression. BRET technology has already made a substantial contribution to our understanding of GPCRs and protein-protein interactions, in particular by providing strong evidence that GPCRs homo- and hetero-oligomerize. New BRET detection systems and the potential for novel high throughput screening applications means that BRET promises to play an important role in future research and drug discovery.
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Affiliation(s)
- Kevin Donald George Pfleger
- Molecular Endocrinology Research Group, Western Australian Institute for Medical Research, Centre for Medical Research, University of Western Australia
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96
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Abstract
To facilitate purification and structural characterization, the CB2 cannabinoid receptor is expressed in methylotrophic yeast Pichia pastoris. The expression plasmids were constructed in which the CB2 gene is under the control of the highly inducible promoter of P. pastoris alcohol oxidase 1 gene. A c-myc epitope and a hexahistidine tag were introduced at the C-terminal of the CB2 to permit easy detection and purification. In membrane preparations of CB2 gene transformed yeast cells, Western blot analysis detected the expression of CB2 proteins. Radioligand binding assays demonstrated that the CB2 receptors expressed in P. pastoris have a pharmacological profile similar to that of the receptors expressed in mammalian systems. Furthermore, the epitope-tagged receptor was purified by metal chelating chromatography and the purified CB2 preparations were subjected to digestion by trypsin. MALDI/TOF mass spectrometry analysis of the peptides extracted from tryptic digestions detected 14 peptide fragments derived from the CB2 receptor. ESI mass spectrometry was used to sequence one of these peptide fragments, thus, further confirming the identity of the purified receptor. In conclusion, these data demonstrated for the first time that epitope-tagged, functional CB2 cannabinoid receptor can be expressed in P. pastoris for purification.
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Affiliation(s)
- Wenke Feng
- Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY 40292, USA
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97
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Han SK, Dong X, Hwang JI, Zylka MJ, Anderson DJ, Simon MI. Orphan G protein-coupled receptors MrgA1 and MrgC11 are distinctively activated by RF-amide-related peptides through the Galpha q/11 pathway. Proc Natl Acad Sci U S A 2002; 99:14740-5. [PMID: 12397184 PMCID: PMC137489 DOI: 10.1073/pnas.192565799] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
MrgA1 and MrgC11 belong to a recently identified family of orphan G-protein coupled receptors, called mrgs (mas-related genes). They are only expressed in a specific subset of sensory neurons that are known to detect painful stimuli. However, the precise physiological function of Mrg receptors and their underlying mechanisms of signal transduction are not known. We therefore have screened a series of neuropeptides against human embryonic kidney (HEK) 293 cells that stably express either MrgA1 or MrgC11 to identify ligands and/or agonists. MrgA1- or MrgC11-specific agonists stimulated dose-dependent increases in intracellular free Ca(2+) in a pertussis toxin-insensitive manner, but failed to alter basal or forskolin-stimulated levels of intracellular cAMP. Furthermore, studies using embryonic fibroblasts derived from various Galpha protein knockout mice demonstrated that both the MrgA1 and MrgC11 receptors are coupled to the Galpha(q/11) signaling pathway. Screening of neuropeptides identified surrogate agonists, most of these peptides included a common C-terminal -RF(Y)G or -RF(Y) amide motif. Structure-function studies suggest that endogenous ligands of Mrg receptors are likely to be RF(Y)G and/or RF(Y) amide-related peptides and that postprocessing of these peptides may serve to determine Mrg receptor-ligand specificity. The differences in ligand specificity also suggest functional diversity amongst the Mrg receptors.
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Affiliation(s)
- Sang-Kyou Han
- Division of Biology 147-75, California Institute of Technology, Pasadena 91125, USA
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98
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Song ZH, Feng W. Absence of a conserved proline and presence of a conserved tyrosine in the CB2 cannabinoid receptor are crucial for its function. FEBS Lett 2002; 531:290-4. [PMID: 12417328 DOI: 10.1016/s0014-5793(02)03537-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A majority (84%) of G protein-coupled receptors have a proline (P5.50) in the middle of the fifth transmembrane domain. However, one of the unique structural features of cannabinoid receptors is the replacement of the conserved P5.50 by a leucine (L5.50). It has been shown that a conserved tyrosine (Y5.58), located at the cytoplasmic side of P5.50, is crucial for the signal transduction of several G protein-coupled receptors. We proposed that the replacement of P5.50 by L5.50 and the presence of the conserved Y5.58 in this context are important for the function of CB2. Mutating L5.50 to a proline abolished ligand binding, whereas mutating Y5.58 to an alanine resulted in a rightward shift of the competition binding curves. Both of these mutations led to a complete loss of the ability of cannabinoid agonists to inhibit forskolin-stimulated cAMP accumulation.
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Affiliation(s)
- Z H Song
- Department of Pharmacology and Toxicology, University of Louisville School of Medicine, Louisville, KY, USA.
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99
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Akal-Strader A, Khare S, Xu D, Naider F, Becker JM. Residues in the first extracellular loop of a G protein-coupled receptor play a role in signal transduction. J Biol Chem 2002; 277:30581-90. [PMID: 12058045 DOI: 10.1074/jbc.m204089200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The Saccharomyces cerevisiae pheromone, alpha-factor (WHWLQLKPGQPMY), and Ste2p, its G protein-coupled receptor, were used as a model system to study ligand-receptor interaction. Cys-scanning mutagenesis on each residue of EL1, the first extracellular loop of Ste2p, was used to generate a library of 36 mutants with a single Cys residue substitution. Mutation of most residues of EL1 had only negligible effects on ligand affinity and biological activity of the mutant receptors. However, five mutants were identified that were either partially (L102C and T114C) or severely (N105C, S108C, and Y111C) compromised in signaling but retained binding affinities similar to those of wild-type receptor. Three-dimensional modeling, secondary structure predictions, and subsequent circular dichroism studies on a synthetic peptide with amino acid sequence corresponding to EL1 suggested the presence of a helix corresponding to EL1 residues 106 to 114 followed by two short beta-strands (residues 126 to 135). The distinctive periodicity of the five residues with a signal-deficient phenotype combined with biophysical studies suggested a functional involvement in receptor activation of a face on a 3(10) helix in this region of EL1. These studies indicate that EL1 plays an important role in the conformational switch that activates the Ste2p receptor to initiate the mating pheromone signal transduction pathway.
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Affiliation(s)
- Ayça Akal-Strader
- Department of Biochemistry, Cellular and Molecular Biology, M407 Walters Life Sciences Building, University of Tennessee, Knoxville, TN 37996, USA
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Mellado M, Martínez-A C, Rodríguez-Frade JM. Analysis of G-protein-coupled receptor dimerization following chemokine signaling. Methods 2002; 27:349-57. [PMID: 12217651 DOI: 10.1016/s1046-2023(02)00093-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
An abundance of information has been generated in recent decades on the signaling events triggered through G-protein-coupled receptors (GPCRs). Nonetheless, the structural changes at the cell surface that provoke receptor activation are only now beginning to be understood. It is becoming clear that receptors are not isolated entities that are activated following ligand binding, but that they interact with other molecules already present or recruited to the vicinity, which results in a wide variety of new signaling possibilities. Understanding receptor interactions with relatives and/or friends on the cell surface is thus critical. The most important point is to determine which of these interactions are "casual" and which give rise to functional consequences.
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Affiliation(s)
- Mario Mellado
- Department of Immunology and Oncology, Centro Nacional de Biotecnologi;a, CSIC-Universidad Autónoma de Madrid, Campus de Cantoblanco, Spain
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