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Agnati LF, Guidolin D, Cervetto C, Maura G, Marcoli M. Brain Structure and Function: Insights from Chemical Neuroanatomy. Life (Basel) 2023; 13:life13040940. [PMID: 37109469 PMCID: PMC10142941 DOI: 10.3390/life13040940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 02/24/2023] [Accepted: 03/31/2023] [Indexed: 04/07/2023] Open
Abstract
We present a brief historical and epistemological outline of investigations on the brain’s structure and functions. These investigations have mainly been based on the intermingling of chemical anatomy, new techniques in the field of microscopy and computer-assisted morphometric methods. This intermingling has enabled extraordinary investigations to be carried out on brain circuits, leading to the development of a new discipline: “brain connectomics”. This new approach has led to the characterization of the brain’s structure and function in physiological and pathological conditions, and to the development of new therapeutic strategies. In this context, the conceptual model of the brain as a hyper-network with a hierarchical, nested architecture, arranged in a “Russian doll” pattern, has been proposed. Our investigations focused on the main characteristics of the modes of communication between nodes at the various miniaturization levels, in order to describe the brain’s integrative actions. Special attention was paid to the nano-level, i.e., to the allosteric interactions among G protein-coupled receptors organized in receptor mosaics, as a promising field in which to obtain a new view of synaptic plasticity and to develop new, more selective drugs. The brain’s multi-level organization and the multi-faceted aspects of communication modes point to an emerging picture of the brain as a very peculiar system, in which continuous self-organization and remodeling take place under the action of external stimuli from the environment, from peripheral organs and from ongoing integrative actions.
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Affiliation(s)
- Luigi F. Agnati
- Department of Biochemical, Metabolic Sciences and Neuroscience, University of Modena and Reggio Emilia, 41125 Modena, Italy
| | - Diego Guidolin
- Department of Neuroscience, University of Padova, 35121 Padova, Italy
| | - Chiara Cervetto
- Department of Pharmacy, University of Genova, 16148 Genova, Italy
- Center for Promotion of 3Rs in Teaching and Research (Centro 3R), 56122 Pisa, Italy
| | - Guido Maura
- Department of Pharmacy, University of Genova, 16148 Genova, Italy
| | - Manuela Marcoli
- Department of Pharmacy, University of Genova, 16148 Genova, Italy
- Center for Promotion of 3Rs in Teaching and Research (Centro 3R), 56122 Pisa, Italy
- Center of Excellence for Biomedical Research, University of Genova, 16132 Genova, Italy
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Marcoli M, Agnati LF, Franco R, Cortelli P, Anderlini D, Guidolin D, Cervetto C, Maura G. Modulating brain integrative actions as a new perspective on pharmacological approaches to neuropsychiatric diseases. Front Endocrinol (Lausanne) 2022; 13:1038874. [PMID: 36699033 PMCID: PMC9868467 DOI: 10.3389/fendo.2022.1038874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 12/20/2022] [Indexed: 01/11/2023] Open
Abstract
A critical aspect of drug development in the therapy of neuropsychiatric diseases is the "Target Problem", that is, the selection of a proper target after not simply the etiopathological classification but rather the detection of the supposed structural and/or functional alterations in the brain networks. There are novel ways of approaching the development of drugs capable of overcoming or at least reducing the deficits without triggering deleterious side effects. For this purpose, a model of brain network organization is needed, and the main aspects of its integrative actions must also be established. Thus, to this aim we here propose an updated model of the brain as a hyper-network in which i) the penta-partite synapses are suggested as key nodes of the brain hyper-network and ii) interacting cell surface receptors appear as both decoders of signals arriving to the network and targets of central nervous system diseases. The integrative actions of the brain networks follow the "Russian Doll organization" including the micro (i.e., synaptic) and nano (i.e., molecular) levels. In this scenario, integrative actions result primarily from protein-protein interactions. Importantly, the macromolecular complexes arising from these interactions often have novel structural binding sites of allosteric nature. Taking G protein-coupled receptors (GPCRs) as potential targets, GPCRs heteromers offer a way to increase the selectivity of pharmacological treatments if proper allosteric drugs are designed. This assumption is founded on the possible selectivity of allosteric interventions on G protein-coupled receptors especially when organized as "Receptor Mosaics" at penta-partite synapse level.
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Affiliation(s)
- Manuela Marcoli
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Genova, Italy
- Interuniversity Center for the Promotion of the 3Rs Principles in Teaching and Research (Centro 3R), Pisa, Italy
- Center of Excellence for Biomedical Research, University of Genova, Genova, Italy
- *Correspondence: Manuela Marcoli, ; Luigi F. Agnati,
| | - Luigi F. Agnati
- Department of Biomedical, Metabolic Sciences and Neuroscience, University of Modena and Reggio Emilia, Modena, Italy
- *Correspondence: Manuela Marcoli, ; Luigi F. Agnati,
| | - Rafael Franco
- CiberNed Network Center for Neurodegenerative diseases, National Spanish Health Institute Carlos III, Madrid, Spain
- Molecular Neurobiology laboratory, Department of Biochemistry and Molecular Biomedicine. Universitat de Barcelona, Barcelona, Spain
- School of Chemistry, Universitat de Barcelona, Barcelona, Spain
| | - Pietro Cortelli
- Department of Biomedical and NeuroMotor Sciences (DIBINEM), Alma Mater Studiorum, University of Bologna, Bologna, Italy
- Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
| | - Deanna Anderlini
- Centre for Sensorimotor Performance, The University of Queensland, Brisbane, QLD, Australia
| | - Diego Guidolin
- Department of Neuroscience, University of Padova, Padova, Italy
| | - Chiara Cervetto
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Genova, Italy
- Interuniversity Center for the Promotion of the 3Rs Principles in Teaching and Research (Centro 3R), Pisa, Italy
| | - Guido Maura
- Department of Pharmacy, Section of Pharmacology and Toxicology, University of Genova, Genova, Italy
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Guidolin D, Marcoli M, Tortorella C, Maura G, Agnati LF. G protein-coupled receptor-receptor interactions give integrative dynamics to intercellular communication. Rev Neurosci 2018; 29:703-726. [DOI: 10.1515/revneuro-2017-0087] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2017] [Accepted: 01/01/2018] [Indexed: 01/14/2023]
Abstract
Abstract
The proposal of receptor-receptor interactions (RRIs) in the early 1980s broadened the view on the role of G protein-coupled receptors (GPCR) in the dynamics of the intercellular communication. RRIs, indeed, allow GPCR to operate not only as monomers but also as receptor complexes, in which the integration of the incoming signals depends on the number, spatial arrangement, and order of activation of the protomers forming the complex. The main biochemical mechanisms controlling the functional interplay of GPCR in the receptor complexes are direct allosteric interactions between protomer domains. The formation of these macromolecular assemblies has several physiologic implications in terms of the modulation of the signaling pathways and interaction with other membrane proteins. It also impacts on the emerging field of connectomics, as it contributes to set and tune the synaptic strength. Furthermore, recent evidence suggests that the transfer of GPCR and GPCR complexes between cells via the exosome pathway could enable the target cells to recognize/decode transmitters and/or modulators for which they did not express the pertinent receptors. Thus, this process may also open the possibility of a new type of redeployment of neural circuits. The fundamental aspects of GPCR complex formation and function are the focus of the present review article.
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Affiliation(s)
- Diego Guidolin
- Department of Neuroscience , University of Padova, via Gabelli 65 , I-35121 Padova , Italy
| | - Manuela Marcoli
- Department of Pharmacy and Center of Excellence for Biomedical Research , University of Genova , I-16126 Genova , Italy
| | - Cinzia Tortorella
- Department of Neuroscience , University of Padova, via Gabelli 65 , I-35121 Padova , Italy
| | - Guido Maura
- Department of Pharmacy and Center of Excellence for Biomedical Research , University of Genova , I-16126 Genova , Italy
| | - Luigi F. Agnati
- Department of Biomedical Sciences , University of Modena and Reggio Emilia , I-41121 Modena , Italy
- Department of Neuroscience , Karolinska Institutet , S-17177 Stockholm , Sweden
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Farran B. An update on the physiological and therapeutic relevance of GPCR oligomers. Pharmacol Res 2017; 117:303-327. [PMID: 28087443 DOI: 10.1016/j.phrs.2017.01.008] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2016] [Revised: 01/06/2017] [Accepted: 01/09/2017] [Indexed: 01/17/2023]
Abstract
The traditional view on GPCRs held that they function as single monomeric units composed of identical subunits. This notion was overturned by the discovery that GPCRs can form homo- and hetero-oligomers, some of which are obligatory, and can further assemble into receptor mosaics consisting of three or more protomers. Oligomerisation exerts significant impacts on receptor function and physiology, offering a platform for the diversification of receptor signalling, pharmacology, regulation, crosstalk, internalization and trafficking. Given their involvement in the modulation of crucial physiological processes, heteromers could constitute important therapeutic targets for a wide range of diseases, including schizophrenia, Parkinson's disease, substance abuse or obesity. This review aims at depicting the current developments in GPCR oligomerisation research, documenting various class A, B and C GPCR heteromers detected in vitro and in vivo using biochemical and biophysical approaches, as well as recently identified higher-order oligomeric complexes. It explores the current understanding of dimerization dynamics and the possible interaction interfaces that drive oligomerisation. Most importantly, it provides an inventory of the wide range of physiological processes and pathophysiological conditions to which GPCR oligomers contribute, surveying some of the oligomers that constitute potential drug targets. Finally, it delineates the efforts to develop novel classes of ligands that specifically target and tether to receptor oligomers instead of a single monomeric entity, thus ameliorating their ability to modulate GPCR function.
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Affiliation(s)
- Batoul Farran
- Department of Structural and Molecular Biology, University College London, Gower Street, London, WC1E 6BT, United Kingdom.
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Agnati LF, Marcoli M, Maura G, Fuxe K, Guidolin D. The multi-facet aspects of cell sentience and their relevance for the integrative brain actions: role of membrane protein energy landscape. Rev Neurosci 2016; 27:347-63. [DOI: 10.1515/revneuro-2015-0049] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2015] [Accepted: 11/11/2015] [Indexed: 12/14/2022]
Abstract
AbstractSeveral ion channels can be randomly and spontaneously in an open state, allowing the exchange of ion fluxes between extracellular and intracellular environments. We propose that the random changes in the state of ion channels could be also due to proteins exploring their energy landscapes. Indeed, proteins can modify their steric conformation under the effects of the physicochemical parameters of the environments with which they are in contact, namely, the extracellular, intramembrane and intracellular environments. In particular, it is proposed that the random walk of proteins in their energy landscape is towards attractors that can favor the open or close condition of the ion channels and/or intrinsic activity of G-protein-coupled receptors. The main aspect of the present proposal is that some relevant physicochemical parameters of the environments (e.g. molecular composition, temperature, electrical fields) with which some signaling-involved plasma membrane proteins are in contact alter their conformations. In turn, these changes can modify their information handling via a modulatory action on their random walk towards suitable attractors of their energy landscape. Thus, spontaneous and/or signal-triggered electrical activities of neurons occur that can have emergent properties capable of influencing the integrative actions of brain networks. Against this background, Cook’s hypothesis on ‘cell sentience’ is developed by proposing that physicochemical parameters of the environments with which the plasma-membrane proteins of complex cellular networks are in contact fulfill a fundamental role in their spontaneous and/or signal-triggered activity. Furthermore, it is proposed that a specialized organelle, the primary cilium, which is present in most cells (also neurons and astrocytes), could be of peculiar importance to pick up chemical signals such as ions and transmitters and to detect physical signals such as pressure waves, thermal gradients, and local field potentials.
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Affiliation(s)
| | - Manuela Marcoli
- 3University of Genova, Department of Pharmacy and Center of Excellence for Biomedical Research, Viale Cembrano 4, I-16148 Genova, Italy
| | - Guido Maura
- 3University of Genova, Department of Pharmacy and Center of Excellence for Biomedical Research, Viale Cembrano 4, I-16148 Genova, Italy
| | - Kjell Fuxe
- 2Karolinska Institutet, Department of Neuroscience, S-17177 Stockholm, Sweden
| | - Diego Guidolin
- 4University of Padova, Department of Molecular Medicine, I-35122 Padova, Italy
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Guidolin D, Ciruela F, Genedani S, Guescini M, Tortorella C, Albertin G, Fuxe K, Agnati LF. Bioinformatics and mathematical modelling in the study of receptor–receptor interactions and receptor oligomerization. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1808:1267-83. [DOI: 10.1016/j.bbamem.2010.09.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/03/2010] [Revised: 08/31/2010] [Accepted: 09/26/2010] [Indexed: 10/19/2022]
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Agnati LF, Guidolin D, Vilardaga JP, Ciruela F, Fuxe K. On the expanding terminology in the GPCR field: the meaning of receptor mosaics and receptor heteromers. J Recept Signal Transduct Res 2010; 30:287-303. [PMID: 20429829 PMCID: PMC3595533 DOI: 10.3109/10799891003786226] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The oligomerization of G protein-coupled receptors (GPCRs) is a fact that deserves further attention as increases both the complexity and diversity of the receptor-mediated signal transduction, thus enriching the cell signaling. Consequently, in the present review we tackle among others the problems concerning the terminology used to describe aspects surrounding the GPCRs oligomerization phenomenon. Therefore, the theoretical implications of the GPCR oligomerization will be briefly discussed together with possible implications of this phenomenon especially for new strategies in drug development.
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Agnati LF, Fuxe K, Baluška F, Guidolin D. Implications of the ‘Energide’ concept for communication and information handling in the central nervous system. J Neural Transm (Vienna) 2009; 116:1037-52. [DOI: 10.1007/s00702-009-0193-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Accepted: 01/28/2009] [Indexed: 12/11/2022]
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Structural plasticity in G-protein coupled receptors as demonstrated by the allosteric actions of homocysteine and computer-assisted analysis of disordered domains. ACTA ACUST UNITED AC 2008; 58:459-74. [DOI: 10.1016/j.brainresrev.2007.10.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2007] [Revised: 10/09/2007] [Accepted: 10/15/2007] [Indexed: 01/30/2023]
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Nikolov S, Vera J, Kotev V, Wolkenhauer O, Petrov V. Dynamic properties of a delayed protein cross talk model. Biosystems 2008; 91:51-68. [PMID: 17709175 DOI: 10.1016/j.biosystems.2007.07.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Revised: 07/03/2007] [Accepted: 07/04/2007] [Indexed: 11/26/2022]
Abstract
In this paper we investigate how the inclusion of time delay alters the dynamical properties of the Jacob-Monod model, describing the control of the beta-galactosidase synthesis by the lac repressor protein in E. coli. The consequences of a time delay on the dynamics of this system are analysed using Hopf's theorem and Lyapunov-Andronov's theory applied to the original mathematical model and to an approximated version. Our analytical calculations predict that time delay acts as a key bifurcation parameter. This is confirmed by numerical simulations. A critical value of time delay, which depends on the values of the model parameters, is analytically established. Around this critical value, the properties of the system change drastically, allowing under certain conditions the emergence of stable limit cycles, that is self-sustained oscillations. In addition, the features of the end product repression play an essential role in the characterisation of these limit cycles: if cooperativity is considered in the end product repression, time delay higher than the mentioned critical value induce differentiated responses during the oscillations, provoking cycles of all-or-nothing response in the concentration of the species.
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Affiliation(s)
- Svetoslav Nikolov
- Institute of Mechanics and Biomechanics-BAS, Acad. G. Bonchev Str., Bl. 4, 1113 Sofia, Bulgaria
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Guidolin D, Fuxe K, Neri G, Nussdorfer GG, Agnati LF. On the role of receptor–receptor interactions and volume transmission in learning and memory. ACTA ACUST UNITED AC 2007; 55:119-33. [PMID: 17408566 DOI: 10.1016/j.brainresrev.2007.02.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2006] [Revised: 02/13/2007] [Accepted: 02/14/2007] [Indexed: 11/16/2022]
Abstract
Learning and memory seem to be inherent to a biological neural network. To emerge, they need an extensive functional connectivity, enabling a large repertoire of possible responses to stimuli, and sensitivity of the connectivity to activity, allowing for the selection of adaptive responses. According to the classical view about the organization of the CNS, the connectivity issue is realized by the huge amount of synaptic contacts each neuron establishes, while the adaptation of the network to specific tasks is obtained by mechanisms of activity-dependent synaptic plasticity. The discovery of direct receptor-receptor interactions at the level of the plasma membrane and the existence in the brain of two main modes of communication, the wiring transmission (such as the synaptic transmission) and the volume transmission (based on the diffusion of signals in the extracellular space), provided a broader view of the functional organization of the CNS with potential important consequences on the understanding of learning and memory processes. Owing to receptor-receptor interactions clusters of receptors, the receptor mosaics (RM), can be formed at the plasma membrane where they can work as collective functional units. As a consequence, the connections between the cells become themselves networks (molecular networks) able to adapt their function according to the stimuli they receive. Learning, therefore, can occur also at the level of RMs. Thus, memory formation seems not only to be a distributed process, but also to follow a hierarchical morpho-functional organization. Furthermore, the combination of the two different forms of transmission could allow processes of correlation and coordination to be established between networks and network elements without the need of additional physical connections, leading to a significant increase of the degrees of freedom available to the CNS for learning.
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Affiliation(s)
- Diego Guidolin
- Department of Human Anatomy and Physiology, Section of Anatomy, University of Padova Medical School, via Gabelli 65, I-35121 Padua, Italy.
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Goncharova LB, Tarakanov AO. Molecular networks of brain and immunity. ACTA ACUST UNITED AC 2007; 55:155-66. [PMID: 17408562 DOI: 10.1016/j.brainresrev.2007.02.003] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2006] [Revised: 02/13/2007] [Accepted: 02/14/2007] [Indexed: 11/22/2022]
Abstract
Exciting complexity of natural phenomena can be based on rather simple biophysical principles. For example, the genetic code is based on a double-helix of DNA formed by planar geometry of weak hydrogen bounds. On the examples of cytokine networks, immune synapse, psychoneuroimmunology and systems biology, this review paper attempts to show how molecular networks both in brain and immunity can be studied using common principles of protein-protein interactions.
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Affiliation(s)
- Larisa B Goncharova
- Institute Pasteur of St. Petersburg, ul. Mira 14, St. Petersburg 197101, Russia
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Agnati LF, Genedani S, Leo G, Rivera A, Guidolin D, Fuxe K. One century of progress in neuroscience founded on Golgi and Cajal's outstanding experimental and theoretical contributions. ACTA ACUST UNITED AC 2007; 55:167-89. [PMID: 17467058 DOI: 10.1016/j.brainresrev.2007.03.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2007] [Accepted: 03/09/2007] [Indexed: 11/16/2022]
Abstract
Since the discovery and mapping of the neuronal circuits of the brain by Golgi and Cajal neuroscientists have clearly spelled the fundamental questions which should be answered to delineate the arena for a scientific understanding of brain function: How neurons communicate with each other in a network? Is there some basic principle according to which brain networks are organised? Is it possible to map out brain regions specialised in carrying out some specific task? As far as the first point is concerned it is well known that Golgi and Cajal had opposite views on the interneuronal communication. Golgi suggested protoplasmic continuity and/or electrotonic spreading of currents between neurons. Cajal proposed the so-called "neuron doctrine", which maintained that neurons could communicate only via a specialised region of contiguity, namely the synapse. The present paper has the first and second points as main topics and last century progresses in these fields are viewed as developments of Golgi and Cajal's findings and above all, hypotheses. Thus, we will briefly discuss these topics moving from the transmitter based mapping, which brought neurochemistry into the Golgi-Cajal mapping of the brain with silver impregnation techniques. The mapping of transmitter-identified neurons in the brain represents one of the major foundations for neuropsychopharmacology and a reference frame for the biochemical and behavioural investigations of brain function. Biochemical techniques allowed giving evidence for multiple transmission lines in synapses interacting via receptor-receptor interactions postulated to be based on supramolecular aggregates, called receptor mosaics. Immunocytochemical and autoradiographic mapping techniques allowed the discovery of extra-synaptic receptors and of transmitter-receptor mismatches leading to the introduction of the volume transmission concept by Agnati-Fuxe teams. The Volume Transmission theory proposed the existence of a three-dimensional diffusion of e.g. transmitter and ion signals, released by any type of cell, in the extra-cellular space and the cerebrospinal fluid of the brain. Thus, a synthesis between Golgi and Cajal's views became possible, by considering two main modes of intercellular communication: volume transmission (VT) and wiring transmission (WT) (a prototype of the latter one is synaptic transmission) and two types of networks (cellular and molecular networks) in the central nervous system. This was the basis for the suggestion of two fundamental principles in brain morphological and functional organisation, the miniaturisation and hierarchic organisation. Finally, moving from Apathy's work, a new model of brain networks has recently been proposed. In fact, it has been proposed that a network of fibrils enmeshes the entire CNS forming a global molecular network (GMN) superimposed on the cellular networks.
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Affiliation(s)
- Luigi F Agnati
- Department of BioMedical Sciences, University of Modena and Reggio Emilia, via Campi 287, 41100 Modena, Italy.
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Springael JY, Urizar E, Costagliola S, Vassart G, Parmentier M. Allosteric properties of G protein-coupled receptor oligomers. Pharmacol Ther 2007; 115:410-8. [PMID: 17655934 DOI: 10.1016/j.pharmthera.2007.06.004] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Accepted: 06/07/2007] [Indexed: 11/18/2022]
Abstract
Allosteric regulation of ligand binding is a well-established mechanism regulating the function of G protein-coupled receptors (GPCR). Allosteric modulators have been considered so far as molecules binding to an allosteric site, distinct from that of the reference ligand (orthosteric site), and able to modulate the binding affinity at the orthosteric site and/or the signaling properties resulting from orthosteric site occupancy. Given that most GPCR are known to form dimers or higher order oligomers, we explored whether allosteric interactions could also occur between protomers within oligomeric arrays, thereby influencing binding and signaling receptor properties. Two main conclusions emerged from such studies. First, allosteric modulators can affect one receptor by binding to another receptor within a dimeric or oligomeric complex. Second, allosteric modulators might act on a given receptor by targeting the "orthosteric site" in another receptor of the complex. Allosteric regulation within di(oligo)mers thus implies that the pharmacological properties of a given receptor subtype can be influenced by the array of dimerization partners coexpressed in each particular cell type. Ligands could thus act as agonists or antagonists on 1 receptor, while modulating allosterically the function of a variety of other receptors to which they do not bind directly. Allosteric regulation across GPCR oligomeric interfaces is expected to greatly influence the practice of pharmacology. It will likely affect the design of drug discovery programs, which rely mostly on the overexpression of the receptor of interest in a cell line, thereby focusing on homo-oligomers and ignoring the potential effects of other partners.
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Affiliation(s)
- Jean-Yves Springael
- Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire (IRIBHM), Université Libre de Bruxelles, Campus Erasme, 808 Route de Lennik, Elsevier Inc, B-1070, Brussels, Belgium
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Angelone T, Goumon Y, Cerra MC, Metz-Boutigue MH, Aunis D, Tota B. The emerging cardioinhibitory role of the hippocampal cholinergic neurostimulating peptide. J Pharmacol Exp Ther 2006; 318:336-44. [PMID: 16608915 DOI: 10.1124/jpet.106.102103] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Hippocampal cholinergic neurostimulating peptide (HCNP), which derives from phosphatidylethanolamine-binding protein (also named Raf kinase inhibitor protein), enhances acetylcholine synthesis in the hippocampal medial septal nuclei. It is present in the chromaffin secretory granules of the adrenal cells and under stress is cosecreted with peptide hormones and catecholamines. Using the isolated rat heart perfused according to Langendorff to reveal the cardiotropic action of HCNP on the mammalian heart, we showed that rat HCNP exerts, at concentrations of 5x10(-13) to 10(-6) M, a negative inotropism under basal conditions (left ventricular pressure variations ranging from -8.34+/-0.94% to -21+/-3.5%) and enhances the cholinergic-mediated negative inotropy through direct interaction with G-protein-coupled muscarinic receptor pathway. Under adrenergic stimulation (isoproterenol), the peptide exerts an antiadrenergic action. The analysis of the percentage of rate pressure product variations in terms of EC50 values of isoproterenol alone (-8.5+/-0.3; r2=0.90) and in the presence of rat HCNP at 0.01 nM (-6.9+/-0.36; r2=0.88) revealed a competitive type of antagonism of the peptide. HCNP does not affect either heart rate or coronary pressure. The evidence that HCNP in mammals may play a novel role as an inhibitory cardiac modulator throughout an involvement of the myocardial G-protein-coupled receptor pathway provides new insights regarding the neurohumoral control of heart function under normal and physiopathological conditions.
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Affiliation(s)
- Tommaso Angelone
- Department of Pharmaco-Biology, University of Calabria, 87030 Arcavacata di Rende (CS), Italy
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