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Jayakody T, Inoue A, Kannan S, Nakamura G, Kawakami K, Mendis K, Nguyen TB, Li J, Herr DR, Verma CS, Dawe GS. Mechanisms of biased agonism by Gα i/o-biased stapled peptide agonists of the relaxin-3 receptor. Sci Signal 2024; 17:eabl5880. [PMID: 38349968 DOI: 10.1126/scisignal.abl5880] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2021] [Accepted: 01/26/2024] [Indexed: 02/15/2024]
Abstract
The neuropeptide relaxin-3 is composed of an A chain and a B chain held together by disulfide bonds, and it modulates functions such as anxiety and food intake by binding to and activating its cognate receptor RXFP3, mainly through the B chain. Biased ligands of RXFP3 would help to determine the molecular mechanisms underlying the activation of G proteins and β-arrestins downstream of RXFP3 that lead to such diverse functions. We showed that the i, i+4 stapled relaxin-3 B chains, 14s18 and d(1-7)14s18, were Gαi/o-biased agonists of RXFP3. These peptides did not induce recruitment of β-arrestin1/2 to RXFP3 by GPCR kinases (GRKs), in contrast to relaxin-3, which enabled the GRK2/3-mediated recruitment of β-arrestin1/2 to RXFP3. Relaxin-3 and the previously reported peptide 4 (an i, i+4 stapled relaxin-3 B chain) did not exhibit biased signaling. The staple linker of peptide 4 and parts of both the A chain and B chain of relaxin-3 interacted with extracellular loop 3 (ECL3) of RXFP3, moving it away from the binding pocket, suggesting that unbiased ligands promote a more open conformation of RXFP3. These findings highlight roles for the A chain and the N-terminal residues of the B chain of relaxin-3 in inducing conformational changes in RXFP3, which will help in designing selective biased ligands with improved therapeutic efficacy.
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Affiliation(s)
- Tharindunee Jayakody
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Neurobiology Programme, Life Sciences Institute, National University of Singapore, Singapore
- Department of Chemistry, University of Colombo, P.O. Box 1490, Colombo 00300, Sri Lanka
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
| | | | - Gaku Nakamura
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
| | - Kouki Kawakami
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai 980-8578, Japan
| | - Krishan Mendis
- Department of Chemistry, University of Colombo, P.O. Box 1490, Colombo 00300, Sri Lanka
| | - Thanh-Binh Nguyen
- Bioinformatics Institute, A*STAR, 30 Biopolis Street, #07-01 Matrix, Singapore 138671
| | - Jianguo Li
- Bioinformatics Institute, A*STAR, 30 Biopolis Street, #07-01 Matrix, Singapore 138671
| | - Deron R Herr
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
| | - Chandra S Verma
- Bioinformatics Institute, A*STAR, 30 Biopolis Street, #07-01 Matrix, Singapore 138671
- Department of Biological Sciences, National University of Singapore, 6 Science Drive 4, Singapore 117558
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Dr., Singapore 637551
| | - Gavin S Dawe
- Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Neurobiology Programme, Life Sciences Institute, National University of Singapore, Singapore
- Healthy Longevity Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
- Precision Medicine Translational Research Programme, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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Love CR, Gautam S, Lama C, Le NH, Dauwalder B. The Drosophila dopamine 2-like receptor D2R (Dop2R) is required in the blood brain barrier for male courtship. GENES, BRAIN, AND BEHAVIOR 2023; 22:e12836. [PMID: 36636829 PMCID: PMC9994173 DOI: 10.1111/gbb.12836] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 12/11/2022] [Accepted: 12/22/2022] [Indexed: 01/14/2023]
Abstract
The blood brain barrier (BBB) has the essential function to protect the brain from potentially hazardous molecules while also enabling controlled selective uptake. How these processes and signaling inside BBB cells control neuronal function is an intense area of interest. Signaling in the adult Drosophila BBB is required for normal male courtship behavior and relies on male-specific molecules in the BBB. Here we show that the dopamine receptor D2R is expressed in the BBB and is required in mature males for normal mating behavior. Conditional adult male knockdown of D2R in BBB cells causes courtship defects. The courtship defects observed in genetic D2R mutants can be rescued by expression of normal D2R specifically in the BBB of adult males. Drosophila BBB cells are glial cells. Our findings thus identify a specific glial function for the DR2 receptor and dopamine signaling in the regulation of a complex behavior.
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Affiliation(s)
- Cameron R Love
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA.,Center for Advanced Biotechnology and Medicine, Rutgers University, Piscataway, New Jersey, USA
| | - Sumit Gautam
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
| | - Chamala Lama
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
| | - Nhu Hoa Le
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
| | - Brigitte Dauwalder
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, USA
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3
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Hoxha V, Lama C, Chang PL, Saurabh S, Patel N, Olate N, Dauwalder B. Sex-specific signaling in the blood-brain barrier is required for male courtship in Drosophila. PLoS Genet 2013; 9:e1003217. [PMID: 23359644 PMCID: PMC3554526 DOI: 10.1371/journal.pgen.1003217] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2012] [Accepted: 11/20/2012] [Indexed: 01/12/2023] Open
Abstract
Soluble circulating proteins play an important role in the regulation of mating behavior in Drosophila melanogaster. However, how these factors signal through the blood–brain barrier (bbb) to interact with the sex-specific brain circuits that control courtship is unknown. Here we show that male identity of the blood–brain barrier is necessary and that male-specific factors in the bbb are physiologically required for normal male courtship behavior. Feminization of the bbb of adult males significantly reduces male courtship. We show that the bbb–specific G-protein coupled receptor moody and bbb–specific Go signaling in adult males are necessary for normal courtship. These data identify sex-specific factors and signaling processes in the bbb as important regulators of male mating behavior. Complex behaviors such as mating behavior are controlled by the brain. Ensembles of brain cells work in networks to ensure proper behavior at the right time. While the state of these cells plays an important role in whether and how the behavior is displayed, information from outside the brain is also required. Often, this information is provided by hormones that are present in the circulating fluid (such as the blood). However, the brain is protected by a layer of very tight cells, the so-called blood–brain barrier, that keeps unwanted molecules out. So how then do hormones and other regulatory factors “talk” to the brain? We are studying this question by examining the mating behavior of males of a model organism, the fruit fly Drosophila melanogaster. We have found that the blood–brain barrier cells themselves contain male-specific molecules that play an important role. When they are absent, courtship behavior is compromised. We have also identified how outside factors talk to the brain: by using a cellular signaling protein and a particular signaling pathway. Together they are well suited to pass on outside information to the brain network that regulates mating behavior.
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Affiliation(s)
- Valbona Hoxha
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Chamala Lama
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Peter L. Chang
- Department of Biological Sciences, University of Southern California, Los Angeles, California, United States of America
| | - Sumit Saurabh
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Naiya Patel
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Nicole Olate
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
| | - Brigitte Dauwalder
- Department of Biology and Biochemistry, University of Houston, Houston, Texas, United States of America
- * E-mail:
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4
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Abstract
The deleterious and sometimes fatal outcomes of bacterial infectious diseases are the net result of the interactions between the pathogen and the host, and the genetically tractable fruit fly, Drosophila melanogaster, has emerged as a valuable tool for modeling the pathogen-host interactions of a wide variety of bacteria. These studies have revealed that there is a remarkable conservation of bacterial pathogenesis and host defence mechanisms between higher host organisms and Drosophila. This review presents an in-depth discussion of the Drosophila immune response, the Drosophila killing model, and the use of the model to examine bacterial-host interactions. The recent introduction of the Drosophila model into the oral microbiology field is discussed, specifically the use of the model to examine Porphyromonas gingivalis-host interactions, and finally the potential uses of this powerful model system to further elucidate oral bacterial-host interactions are addressed.
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Affiliation(s)
- Christina O Igboin
- Division of Oral Biology, College of Dentistry, The Ohio State University, Columbus, Ohio, USA
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5
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Abstract
STUDY OBJECTIVES Sleep is a fundamental physiological process and its biological mechanisms are poorly understood. In Drosophila melanogaster, heterotrimeric Go protein is abundantly expressed in the brain. However, its post-developmental function has not been extensively explored. DESIGN Locomotor activity was measured using the Drosophila Activity Monitoring System under a 12:12 LD cycle. Sleep was defined as periods of 5 min with no recorded activity. RESULTS Pan-neuronal elevation of Go signaling induced quiescence accompanied by an increased arousal threshold in flies. By screening region-specific GAL4 lines, we mapped the sleep-regulatory function of Go signaling to mushroom bodies (MBs), a central brain region which modulates memory, decision making, and sleep in Drosophila. Up-regulation of Go activity in these neurons consolidated sleep while inhibition of endogenous Go via expression of Go RNAi or pertussis toxin reduced and fragmented sleep, indicating that the Drosophila sleep requirement is affected by levels of Go activity in the MBs. Genetic interaction results showed that Go signaling serves as a neuronal transmission inhibitor in a cAMP-independent pathway. CONCLUSION Go signaling is a novel signaling pathway in MBs that regulates sleep in Drosophila.
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Affiliation(s)
- Fang Guo
- State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China
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Katanayeva N, Kopein D, Portmann R, Hess D, Katanaev VL. Competing activities of heterotrimeric G proteins in Drosophila wing maturation. PLoS One 2010; 5:e12331. [PMID: 20808795 PMCID: PMC2925898 DOI: 10.1371/journal.pone.0012331] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Accepted: 07/29/2010] [Indexed: 02/03/2023] Open
Abstract
Drosophila genome encodes six alpha-subunits of heterotrimeric G proteins. The Galphas alpha-subunit is involved in the post-eclosion wing maturation, which consists of the epithelial-mesenchymal transition and cell death, accompanied by unfolding of the pupal wing into the firm adult flight organ. Here we show that another alpha-subunit Galphao can specifically antagonize the Galphas activities by competing for the Gbeta13F/Ggamma1 subunits of the heterotrimeric Gs protein complex. Loss of Gbeta13F, Ggamma1, or Galphas, but not any other G protein subunit, results in prevention of post-eclosion cell death and failure of the wing expansion. However, cell death prevention alone is not sufficient to induce the expansion defect, suggesting that the failure of epithelial-mesenchymal transition is key to the folded wing phenotypes. Overactivation of Galphas with cholera toxin mimics expression of constitutively activated Galphas and promotes wing blistering due to precocious cell death. In contrast, co-overexpression of Gbeta13F and Ggamma1 does not produce wing blistering, revealing the passive role of the Gbetagamma in the Galphas-mediated activation of apoptosis, but hinting at the possible function of Gbetagamma in the epithelial-mesenchymal transition. Our results provide a comprehensive functional analysis of the heterotrimeric G protein proteome in the late stages of Drosophila wing development.
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Affiliation(s)
| | - Damir Kopein
- Department of Biology, University of Konstanz, Konstanz, Germany
| | - Reto Portmann
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Daniel Hess
- Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland
| | - Vladimir L. Katanaev
- Department of Biology, University of Konstanz, Konstanz, Germany
- Institute of Protein Research, Russian Academy of Science, Pushchino, Russia
- * E-mail:
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Gavin BA, Arruda SE, Dolph PJ. The role of carcinine in signaling at the Drosophila photoreceptor synapse. PLoS Genet 2008; 3:e206. [PMID: 18069895 PMCID: PMC2134947 DOI: 10.1371/journal.pgen.0030206] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2007] [Accepted: 10/05/2007] [Indexed: 12/02/2022] Open
Abstract
The Drosophila melanogaster photoreceptor cell has long served as a model system for researchers focusing on how animal sensory neurons receive information from their surroundings and translate this information into chemical and electrical messages. Electroretinograph (ERG) analysis of Drosophila mutants has helped to elucidate some of the genes involved in the visual transduction pathway downstream of the photoreceptor cell, and it is now clear that photoreceptor cell signaling is dependent upon the proper release and recycling of the neurotransmitter histamine. While the neurotransmitter transporters responsible for clearing histamine, and its metabolite carcinine, from the synaptic cleft have remained unknown, a strong candidate for a transporter of either substrate is the uncharacterized inebriated protein. The inebriated gene (ine) encodes a putative neurotransmitter transporter that has been localized to photoreceptor cells in Drosophila and mutations in ine result in an abnormal ERG phenotype in Drosophila. Loss-of-function mutations in ebony, a gene required for the synthesis of carcinine in Drosophila, suppress components of the mutant ine ERG phenotype, while loss-of-function mutations in tan, a gene necessary for the hydrolysis of carcinine in Drosophila, have no effect on the ERG phenotype in ine mutants. We also show that by feeding wild-type flies carcinine, we can duplicate components of mutant ine ERGs. Finally, we demonstrate that treatment with H3 receptor agonists or inverse agonists rescue several components of the mutant ine ERG phenotype. Here, we provide pharmacological and genetic epistatic evidence that ine encodes a carcinine neurotransmitter transporter. We also speculate that the oscillations observed in mutant ine ERG traces are the result of the aberrant activity of a putative H3 receptor. During signaling in the nervous system, individual nerve cells transfer information to one another by a complex process called synaptic transmission. This communication involves the release of a specific neurotransmitter into the synaptic cleft, which then triggers signaling in the downstream neuron by binding to and activating specific cell surface receptors. In order to terminate the neuronal signal, the neurotransmitter must be rapidly removed from the synaptic cleft. This is done by two mechanisms: the neurotransmitter can be degraded or modified, or the transmitter can be taken up by the presynaptic neuron and packaged into vesicles for reuse. In the compound eye of the fruitfly D. melanogaster, the photoreceptor cell responds to light and releases histamine into the synaptic cleft. This signal is terminated by the removal of histamine from the synapse and the enzymatic conversion of histamine to carcinine. We have shown that it is not sufficient just to modify the histamine neurotransmitter, but it is also important to remove carcinine from the photoreceptor synapse. The failure to adequately remove carcinine results in defects in the visual transduction process. Moreover, the work suggests that carcinine itself modulates vision by regulating histamine release into the synapse.
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Affiliation(s)
- Brendan A Gavin
- Department of Biology, Dartmouth College, Hanover, New Hampshire, United States of America
| | - Susan E Arruda
- Department of Biology, Franklin Pierce College, Rindge, New Hampshire, United States of America
| | - Patrick J Dolph
- Department of Biology, Dartmouth College, Hanover, New Hampshire, United States of America
- * To whom correspondence should be addressed. E-mail:
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8
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Ferris J, Ge H, Liu L, Roman G. G(o) signaling is required for Drosophila associative learning. Nat Neurosci 2006; 9:1036-40. [PMID: 16845387 DOI: 10.1038/nn1738] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2006] [Accepted: 06/14/2006] [Indexed: 11/09/2022]
Abstract
Heterotrimeric G(o) is one of the most abundant proteins in the brain, yet relatively little is known of its neural functions in vivo. Here we demonstrate that G(o) signaling is required for the formation of associative memory. In Drosophila melanogaster, pertussis toxin (PTX) is a selective inhibitor of G(o) signaling. The postdevelopmental expression of PTX within mushroom body neurons robustly and reversibly inhibits associative learning. The effect of G(o) inhibition is distributed in both gamma- and alpha/beta-lobe mushroom body neurons. However, the expression of PTX in neurons adjacent to the mushroom bodies does not affect memory. PTX expression also does not interact genetically with a rutabaga adenylyl cyclase loss-of-function mutation. Thus, G(o) defines a new signaling pathway required in mushroom body neurons for the formation of associative memory.
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Affiliation(s)
- Jacob Ferris
- Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, Texas 77030, USA
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9
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Tsitolovsky LE. Protection from neuronal damage evoked by a motivational excitation is a driving force of intentional actions. ACTA ACUST UNITED AC 2005; 49:566-94. [PMID: 16269320 DOI: 10.1016/j.brainresrev.2005.02.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2004] [Revised: 12/16/2004] [Accepted: 02/25/2005] [Indexed: 01/13/2023]
Abstract
Motivation may be understood as an organism's subjective attitude to its current physiological state, which somehow modulates generation of actions until the organism attains an optimal state. How does this subjective attitude arise and how does it modulate generation of actions? Diverse lines of evidence suggest that elemental motivational states (hunger, thirst, fear, drug-dependence, etc.) arise as the result of metabolic disturbances and are related to transient injury, while rewards (food, water, avoidance, drugs, etc.) are associated with the recovery of specific neurons. Just as motivation and the very life of an organism depend on homeostasis, i.e., maintenance of optimum performance, so a neuron's behavior depends on neuronal (i.e., ion) homeostasis. During motivational excitation, the conventional properties of a neuron, such as maintenance of membrane potential and spike generation, are disturbed. Instrumental actions may originate as a consequence of the compensational recovery of neuronal excitability after the excitotoxic damage induced by a motivation. When the extent of neuronal actions is proportional to a metabolic disturbance, the neuron theoretically may choose a beneficial behavior even, if at each instant, it acts by chance. Homeostasis supposedly may be directed to anticipating compensation of the factors that lead to a disturbance of the homeostasis and, as a result, participates in the plasticity of motivational behavior. Following this line of thought, I suggest that voluntary actions arise from the interaction between endogenous compensational mechanisms and excitotoxic damage of specific neurons, and thus anticipate the exogenous compensation evoked by a reward.
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Affiliation(s)
- Lev E Tsitolovsky
- Department of Life Science, Bar-Ilan University, Ramat-Gan 52900, Israel.
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10
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Abstract
Expressing a gene in cells in which it is not normally active is a powerful way of determining its function. The GAL4 system allows the selective expression of any cloned gene in a wide variety of cell- and tissue-specific patterns in Drosophila. A promoter (or enhancer) directs expression of the yeast transcriptional activator GAL4 in a particular pattern, and GAL4 in turn directs transcription of the GAL4-responsive (UAS) target gene in an identical pattern. The system's key feature is that the GAL4 gene and UAS-target gene are initially separated into two distinct transgenic lines. In the GAL4 line, the activator protein is present, but has no target gene to activate. In the UAS-target gene line, the target gene is silent because the activator is absent. It is only when the GAL4 line is crossed to the UAS-target gene line that the target gene is turned on in the progeny. In this article we describe, in detail, how to generate and characterize GAL4 lines and how to prepare UAS-target gene lines. Vector maps are provided for pGaTB, P[GawB], and pP[UAST]. In addition, we consider the range of UAS-reporters currently available and review several new modifications of the GAL4 system.
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Affiliation(s)
- C B Phelps
- Wellcome/CRC Institute, Cambridge University, United Kingdom
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Barritt GJ, Gregory RB. An evaluation of strategies available for the identification of GTP-binding proteins required in intracellular signalling pathways. Cell Signal 1997; 9:207-18. [PMID: 9218120 DOI: 10.1016/s0898-6568(96)00131-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Strategies which can be used to elucidate the nature of a GTP-binding regulatory protein (G-protein) involved in an intracellular pathway of interest in the complex environment of the cell are described and evaluated. A desirable strategy is considered to be one in which the first stage indicates a requirement for one or more G-proteins, provides information on whether a monomeric, trimeric or other type of G-protein is involved, and gives some idea of the G-protein sub-class. In the second stage the specific G-protein involved is identified. Approaches available for investigations in the first stage include the use of analogues of GTP and GDP, AlF4-, inhibitors of G-protein isoprenylation, bacterial toxins which covalently modify G-proteins, and the introduction of a purified GDP dissociation inhibitor, GDP exchange and/or GTP-ase activating protein. Identification of the specific G-protein in the second stage can be achieved using anti G-protein antibodies, G-protein-or receptor-derived peptides, antisense G-protein RNA and over-expressed, constitutively-active or dominant-negative G-protein mutants. The correct interpretation of results obtained with GTP and GDP analogues and AlF4- in the first stage is complex and often difficult, and requires a thorough understanding of the functions and mechanisms of activation of G-proteins. Nevertheless, it is important to reach the correct conclusion at this stage since considerable time and expense are usually required for investigations in the second stage.
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Affiliation(s)
- G J Barritt
- Department of Medical Biochemistry, School of Medicine, Flinders University, Adelaide, Australia
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12
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Abstract
The introduction of cloned and manipulated genetic material into the germline of an experimental organism is one of the most powerful tools of modern biology. In the case of the fruit fly, Drosophila melanogaster, there is also an unparalleled range of sophisticated genetic tools to facilitate subsequent analysis. In consequence, Drosophila remains a most favourable model organism for the dissection of gene structure and function in vivo. In this review we look at some of the achievements to date in Drosophila genome manipulation, and at what may be possible in the near future.
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Affiliation(s)
- L W Sentry
- Department of Genetics, University of Glasgow, UK
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