1
|
Tutkus M, Lundgaard CV, Veshaguri S, Tønnesen A, Hatzakis N, Rasmussen SGF, Stamou D. Probing Activation and Conformational Dynamics of the Vesicle-Reconstituted β 2 Adrenergic Receptor at the Single-Molecule Level. J Phys Chem B 2024; 128:2124-2133. [PMID: 38391238 PMCID: PMC10926102 DOI: 10.1021/acs.jpcb.3c08349] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2024]
Abstract
G-protein-coupled receptors (GPCRs) are structurally flexible membrane proteins that mediate a host of physiological responses to extracellular ligands like hormones and neurotransmitters. Fine features of their dynamic structural behavior are hypothesized to encode the functional plasticity seen in GPCR activity, where ligands with different efficacies can direct the same receptor toward different signaling phenotypes. Although the number of GPCR crystal structures is increasing, the receptors are characterized by complex and poorly understood conformational landscapes. Therefore, we employed a fluorescence microscopy assay to monitor conformational dynamics of single β2 adrenergic receptors (β2ARs). To increase the biological relevance of our findings, we decided not to reconstitute the receptor in detergent micelles but rather lipid membranes as proteoliposomes. The conformational dynamics were monitored by changes in the intensity of an environmentally sensitive boron-dipyrromethene (BODIPY 493/503) fluorophore conjugated to an endogenous cysteine (located at the cytoplasmic end of the sixth transmembrane helix of the receptor). Using total internal reflection fluorescence microscopy (TIRFM) and a single small unilamellar liposome assay that we previously developed, we followed the real-time dynamic properties of hundreds of single β2ARs reconstituted in a native-like environment─lipid membranes. Our results showed that β2AR-BODIPY fluctuates between several states of different intensity on a time scale of seconds, compared to BODIPY-lipid conjugates that show almost entirely stable fluorescence emission in the absence and presence of the full agonist BI-167107. Agonist stimulation changes the β2AR dynamics, increasing the population of states with higher intensities and prolonging their durations, consistent with bulk experiments. The transition density plot demonstrates that β2AR-BODIPY, in the absence of the full agonist, interconverts between states of low and moderate intensity, while the full agonist renders transitions between moderate and high-intensity states more probable. This redistribution is consistent with a mechanism of conformational selection and is a promising first step toward characterizing the conformational dynamics of GPCRs embedded in a lipid bilayer.
Collapse
Affiliation(s)
- Marijonas Tutkus
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
- Institute of Biotechnology, Life Sciences Center, Vilnius University, Saulėtekio Ave. 7, LT-10257 Vilnius, Lithuania
- Department of Molecular Compound Physics, Center for Physical Sciences and Technology, Saulėtekio Ave. 3, LT-10257 Vilnius, Lithuania
| | - Christian V Lundgaard
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Salome Veshaguri
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Asger Tønnesen
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Nikos Hatzakis
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
- Department of Chemistry and Nanoscience Center, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| | - Søren G F Rasmussen
- Department of Neuroscience and Pharmacology, Panum, University of Copenhagen, Blegdamsvej 3, DK-2200 Copenhagen, Denmark
| | - Dimitrios Stamou
- Department of Chemistry, University of Copenhagen, Universitetsparken 5, DK-2100 Copenhagen, Denmark
- Center for Geometrically Engineered Cellular Systems, Universitetsparken 5, DK-2100 Copenhagen, Denmark
| |
Collapse
|
2
|
Cullum SA, Veprintsev DB, Hill SJ. Kinetic analysis of endogenous β 2 -adrenoceptor-mediated cAMP GloSensor™ responses in HEK293 cells. Br J Pharmacol 2023; 180:1304-1315. [PMID: 36495270 PMCID: PMC10952559 DOI: 10.1111/bph.16008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 11/01/2022] [Accepted: 12/02/2022] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND AIM Standard pharmacological analysis of agonist activity utilises measurements of receptor-mediated responses at a set time-point, or at the peak response level, to characterise ligands. However, the occurrence of non-equilibrium conditions may dramatically impact the properties of the response being measured. Here we have analysed the initial kinetic phases of cAMP responses to β2 -adrenoceptor agonists in HEK293 cells expressing the endogenous β2 -adrenoceptor at extremely low levels. EXPERIMENTAL APPROACH The kinetics of β2 -adrenoceptor agonist-stimulated cAMP responses were monitored in real-time, in the presence and absence of antagonists, in HEK293 cells expressing the cAMP GloSensor™ biosensor. Potency (EC50 ) and efficacy (Emax ) values were determined at the peak of the agonist GloSensor™ response and compared to kinetic parameters L50 and IRmax values derived from initial response rates. KEY RESULTS The partial agonists salbutamol and salmeterol displayed reduced relative IRmax values (with respect to isoprenaline) when compared with their Emax values. Except for the fast dissociating bisoprolol, preincubation with β2 -adrenoceptor antagonists produced a large reduction in the isoprenaline peak response due to a state of hemi-equilibrium in this low receptor reserve system. This effect was exacerbated when IRmax parameters were measured. Furthermore, bisoprolol produced a large reduction in isoprenaline IRmax consistent with its short residence time. CONCLUSIONS AND IMPLICATIONS Kinetic analysis of real-time signalling data can provide valuable insights into the hemi-equilibria that can occur in low receptor reserve systems with agonist-antagonist interactions, due to incomplete dissociation of antagonist whilst the peak agonist response is developing.
Collapse
Affiliation(s)
- Sean A. Cullum
- Division of Physiology, Pharmacology and Neuroscience, School of Life SciencesUniversity of NottinghamNottinghamUK
- Centre of Membrane Proteins and ReceptorsUniversity of Birmingham and NottinghamNottinghamUK
| | - Dmitry B. Veprintsev
- Division of Physiology, Pharmacology and Neuroscience, School of Life SciencesUniversity of NottinghamNottinghamUK
- Centre of Membrane Proteins and ReceptorsUniversity of Birmingham and NottinghamNottinghamUK
| | - Stephen J. Hill
- Division of Physiology, Pharmacology and Neuroscience, School of Life SciencesUniversity of NottinghamNottinghamUK
- Centre of Membrane Proteins and ReceptorsUniversity of Birmingham and NottinghamNottinghamUK
| |
Collapse
|
3
|
Heng J, Hu Y, Pérez-Hernández G, Inoue A, Zhao J, Ma X, Sun X, Kawakami K, Ikuta T, Ding J, Yang Y, Zhang L, Peng S, Niu X, Li H, Guixà-González R, Jin C, Hildebrand PW, Chen C, Kobilka BK. Function and dynamics of the intrinsically disordered carboxyl terminus of β2 adrenergic receptor. Nat Commun 2023; 14:2005. [PMID: 37037825 PMCID: PMC10085991 DOI: 10.1038/s41467-023-37233-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 03/07/2023] [Indexed: 04/12/2023] Open
Abstract
Advances in structural biology have provided important mechanistic insights into signaling by the transmembrane core of G-protein coupled receptors (GPCRs); however, much less is known about intrinsically disordered regions such as the carboxyl terminus (CT), which is highly flexible and not visible in GPCR structures. The β2 adrenergic receptor's (β2AR) 71 amino acid CT is a substrate for GPCR kinases and binds β-arrestins to regulate signaling. Here we show that the β2AR CT directly inhibits basal and agonist-stimulated signaling in cell lines lacking β-arrestins. Combining single-molecule fluorescence resonance energy transfer (FRET), NMR spectroscopy, and molecular dynamics simulations, we reveal that the negatively charged β2AR-CT serves as an autoinhibitory factor via interacting with the positively charged cytoplasmic surface of the receptor to limit access to G-proteins. The stability of this interaction is influenced by agonists and allosteric modulators, emphasizing that the CT plays important role in allosterically regulating GPCR activation.
Collapse
Affiliation(s)
- Jie Heng
- School of Medicine, Tsinghua University, Beijing, 100084, China
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, 100084, China
- Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Yunfei Hu
- Beijing Nuclear Magnetic Resonance Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
- Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Science, Wuhan, 430071, China
| | - Guillermo Pérez-Hernández
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Charitéplatz 1, 10117, Berlin, Germany
| | - Asuka Inoue
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Jiawei Zhao
- Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Xiuyan Ma
- School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Xiaoou Sun
- School of Medicine, Tsinghua University, Beijing, 100084, China
| | - Kouki Kawakami
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Tatsuya Ikuta
- Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Miyagi, 980-8578, Japan
| | - Jienv Ding
- Beijing Nuclear Magnetic Resonance Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
- College of Life Sciences, Peking University, Beijing, 100871, China
| | - Yujie Yang
- Beijing Nuclear Magnetic Resonance Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Lujia Zhang
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Sijia Peng
- School of Life Sciences, Tsinghua University, Beijing, 100084, China
| | - Xiaogang Niu
- Beijing Nuclear Magnetic Resonance Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Hongwei Li
- Beijing Nuclear Magnetic Resonance Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Ramon Guixà-González
- Condensed Matter Theory Group, Paul Scherrer Institute, CH-5232, Villigen, PSI, Switzerland
| | - Changwen Jin
- Beijing Nuclear Magnetic Resonance Center, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China
| | - Peter W Hildebrand
- Charité Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Medical Physics and Biophysics, Charitéplatz 1, 10117, Berlin, Germany
- Institute of Medical Physics and Biophysics, University Leipzig, 04107, Leipzig, Germany
- Berlin Institute of Health, 10178, Berlin, Germany
| | - Chunlai Chen
- Beijing Advanced Innovation Center for Structural Biology, Tsinghua University, Beijing, 100084, China.
- Beijing Frontier Research Center for Biological Structure, Tsinghua University, Beijing, 100084, China.
- Tsinghua-Peking Joint Center for Life Sciences, Tsinghua University, Beijing, 100084, China.
- School of Life Sciences, Tsinghua University, Beijing, 100084, China.
| | - Brian K Kobilka
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, 94305, USA.
| |
Collapse
|
4
|
Peña KA. Endosomal parathyroid hormone receptor signaling. Am J Physiol Cell Physiol 2022; 323:C783-C790. [PMID: 35912987 PMCID: PMC9467467 DOI: 10.1152/ajpcell.00452.2021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2021] [Revised: 07/20/2022] [Accepted: 07/25/2022] [Indexed: 11/22/2022]
Abstract
The canonical model for G protein-coupled receptors (GPCRs) activation assumes that stimulation of heterotrimeric G protein signaling upon ligand binding occurs solely at the cell surface and that duration of the stimulation is transient to prevent overstimulation. In this model, GPCR signaling is turned-off by receptor phosphorylation via GPCR kinases (GRKs) and subsequent recruitment of β-arrestins, resulting in receptor internalization into endosomes. Internalized receptors can then recycle back to the cell surface or be trafficked to lysosomes for degradation. However, over the last decade, this model has been extended by discovering that some internalized GPCRs continue to signal via G proteins from endosomes. This is the case for the parathyroid hormone (PTH) type 1 receptor (PTHR), which engages on sustained cAMP signaling from endosomes upon PTH stimulation. Accumulative evidence shows that the location of signaling has an impact on the physiological effects of GPCR signaling. This mini-review discusses recent insights into the mechanisms of PTHR endosomal signaling and its physiological impact.
Collapse
Affiliation(s)
- Karina A Peña
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvania
| |
Collapse
|
5
|
Examination of Intracellular GPCR-Mediated Signaling with High Temporal Resolution. Int J Mol Sci 2022; 23:ijms23158516. [PMID: 35955656 PMCID: PMC9369311 DOI: 10.3390/ijms23158516] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 07/28/2022] [Accepted: 07/29/2022] [Indexed: 11/17/2022] Open
Abstract
The GTP-binding protein-coupled receptors (GPCRs) play important roles in physiology and neuronal signaling. More than a thousand genes, excluding the olfactory receptors, have been identified that encode these integral membrane proteins. Their pharmacological and functional properties make them fascinating targets for drug development, since various disease states can be treated and overcome by pharmacologically addressing these receptors and/or their downstream interacting partners. The activation of the GPCRs typically causes transient changes in the intracellular second messenger concentrations as well as in membrane conductance. In contrast to ion channel-mediated electrical signaling which results in spontaneous cellular responses, the GPCR-mediated metabotropic signals operate at a different time scale. Here we have studied the kinetics of two common GPCR-induced signaling pathways: (a) Ca2+ release from intracellular stores and (b) cyclic adenosine monophosphate (cAMP) production. The latter was monitored via the activation of cyclic nucleotide-gated (CNG) ion channels causing Ca2+ influx into the cell. Genetically modified and stably transfected cell lines were established and used in stopped-flow experiments to uncover the individual steps of the reaction cascades. Using two homologous biogenic amine receptors, either coupling to Go/q or Gs proteins, allowed us to determine the time between receptor activation and signal output. With ~350 ms, the release of Ca2+ from intracellular stores was much faster than cAMP-mediated Ca2+ entry through CNG channels (~6 s). The measurements with caged compounds suggest that this difference is due to turnover numbers of the GPCR downstream effectors rather than the different reaction cascades, per se.
Collapse
|
6
|
Reiter E. [β-arrestins, their mechanisms of action and multiple roles in the biology of G protein-coupled receptors]. Biol Aujourdhui 2022; 215:107-118. [PMID: 35275055 DOI: 10.1051/jbio/2021010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Indexed: 06/14/2023]
Abstract
The stimulation of G protein-coupled receptors (GPCRs) induces biological responses to a wide range of extracellular cues. The heterotrimeric G proteins, which are recruited to the active conformation of GPCRs, lead to the generation of various diffusible second messengers. Only two other families of proteins exhibit the remarkable characteristic of recognizing and binding to the active conformation of most GPCRs: GPCR kinases (GRKs) and β-arrestins. These two families of proteins were initially identified as key players in the desensitization of G protein activation by GPCRs. Over the years, β-arrestins have been implicated in an increasing number of interactions with non-receptor proteins, expanding the range of cellular functions in which they are involved. It is now well established that β-arrestins, by scaffolding and recruiting protein complexes in an agonist-dependent manner, directly regulate the trafficking and signaling of GPCRs. Remarkable advances have been made in recent years which have made it possible i) to identify biased ligands capable, by stabilizing particular conformations of a growing number of GPCRs, of activating or blocking the action of β-arrestins independently of that of G proteins, some of these ligands holding great therapeutic interest; ii) to demonstrate β-arrestins' role in the compartmentalization of GPCR signaling within the cell, and iii) to understand the molecular details of their interaction with GPCRs and of their activation through structural and biophysical approaches.
Collapse
Affiliation(s)
- Eric Reiter
- CNRS, IFCE, INRAE, Université de Tours, PRC, 37380 Nouzilly, France - Inria, Centre de recherche Inria Saclay-Île-de-France, 91120 Palaiseau, France
| |
Collapse
|
7
|
Hoare SRJ, Tewson PH, Sachdev S, Connor M, Hughes TE, Quinn AM. Quantifying the Kinetics of Signaling and Arrestin Recruitment by Nervous System G-Protein Coupled Receptors. Front Cell Neurosci 2022; 15:814547. [PMID: 35110998 PMCID: PMC8801586 DOI: 10.3389/fncel.2021.814547] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Accepted: 12/17/2021] [Indexed: 11/13/2022] Open
Abstract
Neurons integrate inputs over different time and space scales. Fast excitatory synapses at boutons (ms and μm), and slow modulation over entire dendritic arbors (seconds and mm) are all ultimately combined to produce behavior. Understanding the timing of signaling events mediated by G-protein-coupled receptors is necessary to elucidate the mechanism of action of therapeutics targeting the nervous system. Measuring signaling kinetics in live cells has been transformed by the adoption of fluorescent biosensors and dyes that convert biological signals into optical signals that are conveniently recorded by microscopic imaging or by fluorescence plate readers. Quantifying the timing of signaling has now become routine with the application of equations in familiar curve fitting software to estimate the rates of signaling from the waveform. Here we describe examples of the application of these methods, including (1) Kinetic analysis of opioid signaling dynamics and partial agonism measured using cAMP and arrestin biosensors; (2) Quantifying the signaling activity of illicit synthetic cannabinoid receptor agonists measured using a fluorescent membrane potential dye; (3) Demonstration of multiplicity of arrestin functions from analysis of biosensor waveforms and quantification of the rates of these processes. These examples show how temporal analysis provides additional dimensions to enhance the understanding of GPCR signaling and therapeutic mechanisms in the nervous system.
Collapse
Affiliation(s)
- Sam R. J. Hoare
- Pharmechanics LLC, Owego, NY, United States
- *Correspondence: Sam R. J. Hoare
| | | | - Shivani Sachdev
- Department of Biomedical Sciences, Macquarie University, Sydney, NSW, Australia
| | - Mark Connor
- Department of Biomedical Sciences, Macquarie University, Sydney, NSW, Australia
| | | | | |
Collapse
|
8
|
Yang Y, Zhang L, Yu J, Ma Z, Li M, Wang J, Hu P, Zou J, Liu X, Liu Y, An S, Xiang C, Guo X, Hao Q, Xu TR. A Novel 5-HT 1B Receptor Agonist of Herbal Compounds and One of the Therapeutic Uses for Alzheimer's Disease. Front Pharmacol 2021; 12:735876. [PMID: 34552493 PMCID: PMC8450432 DOI: 10.3389/fphar.2021.735876] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2021] [Accepted: 08/23/2021] [Indexed: 12/30/2022] Open
Abstract
The serotonin receptor 5-HT1B is widely expressed in the central nervous system and has been considered a drug target in a variety of cognitive and psychiatric disorders. The anti-inflammatory effects of 5-HT1B agonists may present a promising approach for Alzheimer's disease (AD) treatment. Herbal antidepressants used in the treatment of AD have shown functional overlap between the active compounds and 5-HT1B receptor stimulation. Therefore, compounds in these medicinal plants that target and stimulate 5-HT1B deserve careful study. Molecular docking, drug affinity responsive target stability, cellular thermal shift assay, fluorescence resonance energy transfer (FRET), and extracellular regulated protein kinases (ERK) 1/2 phosphorylation tests were used to identify emodin-8-O-β-d-glucopyranoside (EG), a compound from Chinese medicinal plants with cognitive deficit attenuating and antidepressant effects, as an agonist of 5-HT1B. EG selectively targeted 5-HT1B and activated the 5-HT1B-induced signaling pathway. The activated 5-HT1B pathway suppressed tumor necrosis factor (TNF)-α levels, thereby protecting neural cells against beta-amyloid (Aβ)-induced death. Moreover, the agonist activity of EG towards 5-HT1B receptor, in FRET and ERK1/2 phosphorylation, was antagonized by SB 224289, a 5-HT1B antagonist. In addition, EG relieved AD symptoms in transgenic worm models. These results suggested that 5-HT1B receptor activation by EG positively affected Aβ-related inflammatory process regulation and neural death resistance, which were reversed by antagonist SB 224289. The active compounds such as EG might act as potential therapeutic agents through targeting and stimulating 5-HT1B receptor for AD and other serotonin-related disorders. This study describes methods for identification of 5-HT1B agonists from herbal compounds and for evaluating agonists with biological functions, providing preliminary information on medicinal herbal pharmacology.
Collapse
Affiliation(s)
- Yang Yang
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Lijing Zhang
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Jiaojiao Yu
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Zhaobin Ma
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Moxiang Li
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Jin Wang
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Pengcheng Hu
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Jia Zou
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Xueying Liu
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Ying Liu
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Su An
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Cheng Xiang
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Xiaoxi Guo
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Qian Hao
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Tian-Rui Xu
- Center for Pharmaceutical Sciences and Engineering, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| |
Collapse
|
9
|
Urakubo H, Yagishita S, Kasai H, Kubota Y, Ishii S. The critical balance between dopamine D2 receptor and RGS for the sensitive detection of a transient decay in dopamine signal. PLoS Comput Biol 2021; 17:e1009364. [PMID: 34591840 PMCID: PMC8483376 DOI: 10.1371/journal.pcbi.1009364] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 08/18/2021] [Indexed: 12/19/2022] Open
Abstract
In behavioral learning, reward-related events are encoded into phasic dopamine (DA) signals in the brain. In particular, unexpected reward omission leads to a phasic decrease in DA (DA dip) in the striatum, which triggers long-term potentiation (LTP) in DA D2 receptor (D2R)-expressing spiny-projection neurons (D2 SPNs). While this LTP is required for reward discrimination, it is unclear how such a short DA-dip signal (0.5-2 s) is transferred through intracellular signaling to the coincidence detector, adenylate cyclase (AC). In the present study, we built a computational model of D2 signaling to determine conditions for the DA-dip detection. The DA dip can be detected only if the basal DA signal sufficiently inhibits AC, and the DA-dip signal sufficiently disinhibits AC. We found that those two requirements were simultaneously satisfied only if two key molecules, D2R and regulators of G protein signaling (RGS) were balanced within a certain range; this balance has indeed been observed in experimental studies. We also found that high level of RGS was required for the detection of a 0.5-s short DA dip, and the analytical solutions for these requirements confirmed their universality. The imbalance between D2R and RGS is associated with schizophrenia and DYT1 dystonia, both of which are accompanied by abnormal striatal LTP. Our simulations suggest that D2 SPNs in patients with schizophrenia and DYT1 dystonia cannot detect short DA dips. We finally discussed that such psychiatric and movement disorders can be understood in terms of the imbalance between D2R and RGS.
Collapse
Affiliation(s)
- Hidetoshi Urakubo
- Integrated Systems Biology Laboratory, Department of Systems Science, Graduate School of Informatics, Kyoto University, Kyoto, Japan
- Section of Electron Microscopy, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
| | - Sho Yagishita
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan
- International Research Center for Neurointelligence (WPI-IRCN), University of Tokyo Institutes for Advanced Study (UTIAS), Tokyo, Japan
| | - Haruo Kasai
- Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan
- International Research Center for Neurointelligence (WPI-IRCN), University of Tokyo Institutes for Advanced Study (UTIAS), Tokyo, Japan
| | - Yoshiyuki Kubota
- Section of Electron Microscopy, National Institute for Physiological Sciences, Okazaki, Aichi, Japan
- Department of Physiological Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki, Aichi, Japan
| | - Shin Ishii
- Integrated Systems Biology Laboratory, Department of Systems Science, Graduate School of Informatics, Kyoto University, Kyoto, Japan
- International Research Center for Neurointelligence (WPI-IRCN), University of Tokyo Institutes for Advanced Study (UTIAS), Tokyo, Japan
| |
Collapse
|
10
|
Nicoll JX, Fry AC, Mosier EM. Androgen and glucocorticoid receptor phosphorylation following resistance exercise and pre-workout supplementation. Steroids 2021; 172:108859. [PMID: 33974920 DOI: 10.1016/j.steroids.2021.108859] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 03/05/2021] [Accepted: 04/24/2021] [Indexed: 11/17/2022]
Abstract
PURPOSE Consumption of caffeine or caffeine containing pre-workout supplements (SUPP) augments steroid hormone responses to resistance exercise (RE). However, the activation of glucocorticoid (GR) and androgen receptors (AR) following RE SUPP has not been investigated. The purpose of this study was to determine the influence of a pre-workout supplement on AR and GR phosphorylation following RE. METHODS In a randomized, counter-balanced, double-blind, placebo-controlled, within-subject crossover study, ten resistance-trained males ((X¯±SD, age = 22 ± 2.4 yrs, hgt = 175 ± 7 cm, body mass = 84.1 ± 11.8 kg) performed four sets of 8 repetitions of barbell back squats at 75% of their 1-repetition maximum (1-RM) with two minutes of rest between sets and a fifth set of barbell back squats at 60% of 1-RM until concentric failure. A SUPP or flavor and color matched placebo (PL) was consumed 60-minutes prior to RE. Vastus lateralis muscle biopsies were obtained prior to supplementation at rest (BL), and ten minutes post-exercise (POST). Biopsies were analyzed for phosphorylated GR (ser134, ser211, and ser226) and phosphorylated AR (ser81, ser213, ser515, ser650) via western blotting. RESULTS pGRser134 decreased, and pGRser226 increased following RE (p < 0.05) with no difference between conditions (p > 0.05). pGRser211 was unchanged after RE (p > 0.05). pARser515 increased, and total AR expression decreased after RE (p < 0.05) in SUPP only. Testosterone and cortisol were not different between SUPP and PL at POST (p > 0.05). CONCLUSION RE influences AR and GR phosphorylation, and SUPP minimally influences this response in the early recovery period.
Collapse
Affiliation(s)
- Justin X Nicoll
- California State University, Northridge, Department of Kinesiology, Northridge, CA, USA.
| | - Andrew C Fry
- University of Kansas, Department of Health, Sport, and Exercise Sciences, Lawrence, KS, USA.
| | - Eric M Mosier
- Northwest Missouri State University, School of Health Science and Wellness, Maryville, MO, USA.
| |
Collapse
|
11
|
Heuninck J, Perpiñá Viciano C, Işbilir A, Caspar B, Capoferri D, Briddon SJ, Durroux T, Hill SJ, Lohse MJ, Milligan G, Pin JP, Hoffmann C. Context-Dependent Signaling of CXC Chemokine Receptor 4 and Atypical Chemokine Receptor 3. Mol Pharmacol 2019; 96:778-793. [PMID: 31092552 DOI: 10.1124/mol.118.115477] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 03/21/2019] [Indexed: 02/06/2023] Open
Abstract
G protein-coupled receptors (GPCRs) are regulated by complex molecular mechanisms, both in physiologic and pathologic conditions, and their signaling can be intricate. Many factors influence their signaling behavior, including the type of ligand that activates the GPCR, the presence of interacting partners, the kinetics involved, or their location. The two CXC-type chemokine receptors, CXC chemokine receptor 4 (CXCR4) and atypical chemokine receptor 3 (ACKR3), both members of the GPCR superfamily, are important and established therapeutic targets in relation to cancer, human immunodeficiency virus infection, and inflammatory diseases. Therefore, it is crucial to understand how the signaling of these receptors works to be able to specifically target them. In this review, we discuss how the signaling pathways activated by CXCR4 and ACKR3 can vary in different situations. G protein signaling of CXCR4 depends on the cellular context, and discrepancies exist depending on the cell lines used. ACKR3, as an atypical chemokine receptor, is generally reported to not activate G proteins but can broaden its signaling spectrum upon heteromerization with other receptors, such as CXCR4, endothelial growth factor receptor, or the α 1-adrenergic receptor (α 1-AR). Also, CXCR4 forms heteromers with CC chemokine receptor (CCR) 2, CCR5, the Na+/H+ exchanger regulatory factor 1, CXCR3, α 1-AR, and the opioid receptors, which results in differential signaling from that of the monomeric subunits. In addition, CXCR4 is present on membrane rafts but can go into the nucleus during cancer progression, probably acquiring different signaling properties. In this review, we also provide an overview of the currently known critical amino acids involved in CXCR4 and ACKR3 signaling.
Collapse
Affiliation(s)
- Joyce Heuninck
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Cristina Perpiñá Viciano
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Ali Işbilir
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Birgit Caspar
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Davide Capoferri
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Stephen J Briddon
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Thierry Durroux
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Stephen J Hill
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Martin J Lohse
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Graeme Milligan
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Jean-Philippe Pin
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| | - Carsten Hoffmann
- IGF, CNRS, Inserm, Université de Montpellier, Montpellier, France (J.H., T.D., J.-P.P.); Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany (C.P.V., A.I., M.J.L., C.H.); Institute for Molecular Cell Biology, Centre for Molecular Biomedicine, University Hospital Jena, Friedrich Schiller University Jena, Jena, Germany (C.P.V., C.H.); Max Delbrück Center for Molecular Medicine, Berlin, Germany (A.I., M.J.L.); Centre for Translational Pharmacology, Institute of Molecular, Cell, and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom (D.C., G.M.); Division of Physiology, Pharmacology and Neuroscience, School of Life Sciences, University of Nottingham, Nottingham, United Kingdom (B.C., S.J.B., S.J.H.); and Centre of Membrane Proteins and Receptors, University of Birmingham and University of Nottingham, The Midlands, United Kingdom (B.C., S.J.B., S.J.H.)
| |
Collapse
|
12
|
Optical approaches for single-cell and subcellular analysis of GPCR-G protein signaling. Anal Bioanal Chem 2019; 411:4481-4508. [PMID: 30927013 DOI: 10.1007/s00216-019-01774-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Revised: 03/05/2019] [Accepted: 03/08/2019] [Indexed: 01/05/2023]
Abstract
G protein-coupled receptors (GPCRs), G proteins, and their signaling associates are major signal transducers that control the majority of cellular signaling and regulate key biological functions including immune, neurological, cardiovascular, and metabolic processes. These pathways are targeted by over one-third of drugs on the market; however, the current understanding of their function is limited and primarily derived from cell-destructive approaches providing an ensemble of static, multi-cell information about the status and composition of molecules. Spatiotemporal behavior of molecules involved is crucial to understanding in vivo cell behaviors both in health and disease, and the advent of genetically encoded fluorescence proteins and small fluorophore-based biosensors has facilitated the mapping of dynamic signaling in cells with subcellular acuity. Since we and others have developed optogenetic methods to regulate GPCR-G protein signaling in single cells and subcellular regions using dedicated wavelengths, the desire to develop and adopt optogenetically amenable assays to measure signaling has motivated us to take a broader look at the available optical tools and approaches compatible with measuring single-cell and subcellular GPCR-G protein signaling. Here we review such key optical approaches enabling the examination of GPCR, G protein, secondary messenger, and downstream molecules such as kinase and lipid signaling in living cells. The methods reviewed employ both fluorescence and bioluminescence detection. We not only further elaborate the underlying principles of these sensors but also discuss the experimental criteria and limitations to be considered during their use in single-cell and subcellular signal mapping.
Collapse
|
13
|
Mouro FM, Rombo DM, Dias RB, Ribeiro JA, Sebastião AM. Adenosine A 2A receptors facilitate synaptic NMDA currents in CA1 pyramidal neurons. Br J Pharmacol 2018; 175:4386-4397. [PMID: 30220081 PMCID: PMC6240125 DOI: 10.1111/bph.14497] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 07/18/2018] [Accepted: 08/21/2018] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND AND PURPOSE NMDA receptors play a key role in both synaptic plasticity and neurodegeneration. Adenosine is an endogenous neuromodulator and through membrane receptors of the A2A subtype can influence both synaptic plasticity and neuronal death. The present work was designed to evaluate the influence of adenosine A2A receptors upon NMDA receptor activity in CA1 hippocampal neurons. We discriminated between modulation of synaptic versus extrasynaptic receptors, since extrasynaptic NMDA receptors are mostly associated with neurodegeneration while synaptic NMDA receptors are linked to plasticity phenomena. EXPERIMENTAL APPROACH Whole-cell patch-clamp recordings were obtained to evaluate NMDA receptor actions on CA1 pyramidal neurons of young adult (5-10 weeks) male Wistar rat hippocampus. KEY RESULTS Activation of A2A receptors with CGS 21680 (30 nM) consistently facilitated chemically-evoked NMDA receptor-currents (NMDA-PSCs) and afferent-evoked NMDA-currents (NMDA-EPSCs), an action prevented by an A2A receptor antagonist (SCH58261, 100 nM) and a PKA inhibitor, H-89 (1 μM). These actions did not reflect facilitation in glutamate release since there was no change in NMDA-EPSCs paired pulse ratio. A2A receptor actions were lost in the presence of an open-channel NMDA receptor blocker, MK-801 (10 μM), but persisted in the presence of memantine, at a concentration (10 μM) known to preferentially block extrasynaptic NMDA receptors. CONCLUSION AND IMPLICATIONS These results show that A2A receptors exert a positive postsynaptic modulatory effect over synaptic, but not extrasynaptic, NMDA receptors in CA1 neurons and, therefore, under non-pathological conditions may contribute to shift the dual role of NMDA receptors towards enhancement of synaptic plasticity.
Collapse
Affiliation(s)
- Francisco M Mouro
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Diogo M Rombo
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Raquel B Dias
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Joaquim A Ribeiro
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Ana M Sebastião
- Instituto de Farmacologia e Neurociências, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal.,Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| |
Collapse
|
14
|
Hoare SRJ, Pierre N, Moya AG, Larson B. Kinetic operational models of agonism for G-protein-coupled receptors. J Theor Biol 2018; 446:168-204. [PMID: 29486201 DOI: 10.1016/j.jtbi.2018.02.014] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 02/07/2018] [Accepted: 02/13/2018] [Indexed: 01/06/2023]
Abstract
The application of kinetics to research and therapeutic development of G-protein-coupled receptors has become increasingly valuable. Pharmacological models provide the foundation of pharmacology, providing concepts and measurable parameters such as efficacy and potency that have underlain decades of successful drug discovery. Currently there are few pharmacological models that incorporate kinetic activity in such a way as to yield experimentally-accessible drug parameters. In this study, a kinetic model of pharmacological response was developed that provides a kinetic descriptor of efficacy (the transduction rate constant, kτ) and allows measurement of receptor-ligand binding kinetics from functional data. The model assumes: (1) receptor interacts with a precursor of the response ("Transduction potential") and converts it to the response. (2) The response can decay. Familiar response vs time plots emerge, depending on whether transduction potential is depleted and/or response decays. These are the straight line, the "association" exponential curve, and the rise-and-fall curve. Convenient, familiar methods are described for measuring the model parameters and files are provided for the curve-fitting program Prism (GraphPad Software) that can be used as a guide. The efficacy parameter kτ is straightforward to measure and accounts for receptor reserve; all that is required is measurement of response over time at a maximally-stimulating concentration of agonist. The modular nature of the model framework allows it to be extended. Here this is done to incorporate antagonist-receptor binding kinetics and slow agonist-receptor equilibration. In principle, the modular framework can incorporate other cellular processes, such as receptor desensitization. The kinetic response model described here can be applied to measure kinetic pharmacological parameters than can be used to advance the understanding of GPCR pharmacology and optimize new and improved therapeutics.
Collapse
Affiliation(s)
- Samuel R J Hoare
- Pharmechanics, LLC, 14 Sunnyside Drive South, Owego NY 13827, USA.
| | | | | | - Brad Larson
- BioTek Instruments, Inc, 100 Tigan Street, Winooski, VT 05404, USA
| |
Collapse
|
15
|
Reiter E, Ayoub MA, Pellissier LP, Landomiel F, Musnier A, Tréfier A, Gandia J, De Pascali F, Tahir S, Yvinec R, Bruneau G, Poupon A, Crépieux P. β-arrestin signalling and bias in hormone-responsive GPCRs. Mol Cell Endocrinol 2017; 449:28-41. [PMID: 28174117 DOI: 10.1016/j.mce.2017.01.052] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/25/2016] [Revised: 01/31/2017] [Accepted: 01/31/2017] [Indexed: 12/14/2022]
Abstract
G protein-coupled receptors (GPCRs) play crucial roles in the ability of target organs to respond to hormonal cues. GPCRs' activation mechanisms have long been considered as a two-state process connecting the agonist-bound receptor to heterotrimeric G proteins. This view is now challenged as mounting evidence point to GPCRs being connected to large arrays of transduction mechanisms involving heterotrimeric G proteins as well as other players. Amongst the G protein-independent transduction mechanisms, those elicited by β-arrestins upon their recruitment to the active receptors are by far the best characterized and apply to most GPCRs. These concepts, in conjunction with remarkable advances made in the field of GPCR structural biology and biophysics, have supported the notion of ligand-selective signalling also known as pharmacological bias. Interestingly, recent reports have opened intriguing prospects to the way β-arrestins control GPCR-mediated signalling in space and time within the cells. In the present paper, we review the existing evidence linking endocrine-related GPCRs to β-arrestin recruitement, signalling, pathophysiological implications and selective activation by biased ligands and/or receptor modifications. Emerging concepts surrounding β-arrestin-mediated transduction are discussed in the light of the peculiarities of endocrine systems.
Collapse
Affiliation(s)
- Eric Reiter
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France.
| | - Mohammed Akli Ayoub
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France; LE STUDIUM(®) Loire Valley Institute for Advanced Studies, 45000, Orléans, France; Biology Department, College of Science, United Arab Emirates University, Al Ain, United Arab Emirates
| | | | - Flavie Landomiel
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Astrid Musnier
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Aurélie Tréfier
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Jorge Gandia
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | | | - Shifa Tahir
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Romain Yvinec
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Gilles Bruneau
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Anne Poupon
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| | - Pascale Crépieux
- PRC, INRA, CNRS, IFCE, Université de Tours, 37380, Nouzilly, France
| |
Collapse
|
16
|
Bondar A, Lazar J. The G protein G i1 exhibits basal coupling but not preassembly with G protein-coupled receptors. J Biol Chem 2017; 292:9690-9698. [PMID: 28438833 DOI: 10.1074/jbc.m116.768127] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Revised: 04/21/2017] [Indexed: 11/06/2022] Open
Abstract
The Gi/o protein family transduces signals from a diverse group of G protein-coupled receptors (GPCRs). The observed specificity of Gi/o-GPCR coupling and the high rate of Gi/o signal transduction have been hypothesized to be enabled by the existence of stable associates between Gi/o proteins and their cognate GPCRs in the inactive state (Gi/o-GPCR preassembly). To test this hypothesis, we applied the recently developed technique of two-photon polarization microscopy (2PPM) to Gαi1 subunits labeled with fluorescent proteins and four GPCRs: the α2A-adrenergic receptor, GABAB, cannabinoid receptor type 1 (CB1R), and dopamine receptor type 2. Our experiments with non-dissociating mutants of fluorescently labeled Gαi1 subunits (exhibiting impaired dissociation from activated GPCRs) showed that 2PPM is capable of detecting GPCR-G protein interactions. 2PPM experiments with non-mutated fluorescently labeled Gαi1 subunits and α2A-adrenergic receptor, GABAB, or dopamine receptor type 2 receptors did not reveal any interaction between the Gi1 protein and the non-stimulated GPCRs. In contrast, non-stimulated CB1R exhibited an interaction with the Gi1 protein. Further experiments revealed that this interaction is caused solely by CB1R basal activity; no preassembly between CB1R and the Gi1 protein could be observed. Our results demonstrate that four diverse GPCRs do not preassemble with non-active Gi1 However, we also show that basal GPCR activity allows interactions between non-stimulated GPCRs and Gi1 (basal coupling). These findings suggest that Gi1 interacts only with active GPCRs and that the well known high speed of GPCR signal transduction does not require preassembly between G proteins and GPCRs.
Collapse
Affiliation(s)
- Alexey Bondar
- From the Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, 37333 Nove Hrady,
| | - Josef Lazar
- From the Center for Nanobiology and Structural Biology, Institute of Microbiology, Academy of Sciences of the Czech Republic, 37333 Nove Hrady.,the Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 16610 Prague, and.,the Faculty of Science, University of South Bohemia, 37005 Ceske Budejovice, Czech Republic
| |
Collapse
|
17
|
Ayoub MA, Yvinec R, Crépieux P, Poupon A. Computational modeling approaches in gonadotropin signaling. Theriogenology 2016; 86:22-31. [DOI: 10.1016/j.theriogenology.2016.04.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Revised: 01/27/2016] [Accepted: 04/13/2016] [Indexed: 01/14/2023]
|
18
|
van Unen J, Rashidfarrokhi A, Hoogendoorn E, Postma M, Gadella TWJ, Goedhart J. Quantitative Single-Cell Analysis of Signaling Pathways Activated Immediately Downstream of Histamine Receptor Subtypes. Mol Pharmacol 2016; 90:162-76. [PMID: 27358232 DOI: 10.1124/mol.116.104505] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 06/28/2016] [Indexed: 01/09/2023] Open
Abstract
Genetically encoded biosensors based on Förster resonance energy transfer (FRET) can visualize responses of individual cells in real time. Here, we evaluated whether FRET-based biosensors provide sufficient contrast and specificity to measure activity of G-protein-coupled receptors. The four histamine receptor subtypes (H1R, H2R, H3R, and H4R) respond to the ligand histamine by activating three canonical heterotrimeric G-protein-mediated signaling pathways with a reported high degree of specificity. Using FRET-based biosensors, we demonstrate that H1R activates Gαq. We also observed that H1R activates Gαi, albeit at a 10-fold lower potency. In addition to increasing cAMP levels, most likely via Gαs, we found that the H2R induces Gαq-mediated calcium release. The H3R and H4R activated Gαi with high specificity and a high potency. We demonstrate that a number of FRET sensors provide sufficient contrast to: 1) analyze the specificity of the histamine receptor subtypes for different heterotrimeric G-protein families with single-cell resolution, 2) probe for antagonist specificity, and 3) allow the measurement of single-cell concentration-response curves.
Collapse
Affiliation(s)
- Jakobus van Unen
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, Amsterdam, The Netherlands
| | - Ali Rashidfarrokhi
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, Amsterdam, The Netherlands
| | - Eelco Hoogendoorn
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, Amsterdam, The Netherlands
| | - Marten Postma
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, Amsterdam, The Netherlands
| | - Theodorus W J Gadella
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, Amsterdam, The Netherlands
| | - Joachim Goedhart
- Swammerdam Institute for Life Sciences, Section of Molecular Cytology, van Leeuwenhoek Centre for Advanced Microscopy, University of Amsterdam, Amsterdam, The Netherlands
| |
Collapse
|
19
|
Lyga S, Volpe S, Werthmann RC, Götz K, Sungkaworn T, Lohse MJ, Calebiro D. Persistent cAMP Signaling by Internalized LH Receptors in Ovarian Follicles. Endocrinology 2016; 157:1613-21. [PMID: 26828746 DOI: 10.1210/en.2015-1945] [Citation(s) in RCA: 57] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
A crucial event in female reproduction occurs at midcycle, when a LH peak induces the final maturation of ovarian follicles. LH signals via a G protein-coupled receptor selectively expressed in the outermost follicular cell layers. However, how LH signals are relayed inside these cells and finally to the oocyte is incompletely understood. Here, we monitored LH signaling in intact ovarian follicles of transgenic mice expressing a fluorescent cAMP sensor. We found that LH stimulation induces 2 phases of cAMP signaling in all cell layers surrounding the oocyte. Interfering with LH receptor internalization abolished the second, persistent cAMP phase and partially inhibited oocyte meiosis resumption. These data suggest that persistent cAMP signals from internalized LH receptors contribute to transmitting LH effects inside follicle cells and ultimately to the oocyte. Thus, this study indicates that the recently proposed paradigm of cAMP signaling by internalized G protein-coupled receptors is implicated in receptor function and is physiologically relevant.
Collapse
Affiliation(s)
- Sandra Lyga
- Institute of Pharmacology and Toxicology, University of Würzburg, and Rudolf Virchow Center, Bio-Imaging Center, 97078 Würzburg, Germany
| | - Silvia Volpe
- Institute of Pharmacology and Toxicology, University of Würzburg, and Rudolf Virchow Center, Bio-Imaging Center, 97078 Würzburg, Germany
| | - Ruth C Werthmann
- Institute of Pharmacology and Toxicology, University of Würzburg, and Rudolf Virchow Center, Bio-Imaging Center, 97078 Würzburg, Germany
| | - Konrad Götz
- Institute of Pharmacology and Toxicology, University of Würzburg, and Rudolf Virchow Center, Bio-Imaging Center, 97078 Würzburg, Germany
| | - Titiwat Sungkaworn
- Institute of Pharmacology and Toxicology, University of Würzburg, and Rudolf Virchow Center, Bio-Imaging Center, 97078 Würzburg, Germany
| | - Martin J Lohse
- Institute of Pharmacology and Toxicology, University of Würzburg, and Rudolf Virchow Center, Bio-Imaging Center, 97078 Würzburg, Germany
| | - Davide Calebiro
- Institute of Pharmacology and Toxicology, University of Würzburg, and Rudolf Virchow Center, Bio-Imaging Center, 97078 Würzburg, Germany
| |
Collapse
|
20
|
β-Arrestin biosensors reveal a rapid, receptor-dependent activation/deactivation cycle. Nature 2016; 531:661-4. [PMID: 27007855 DOI: 10.1038/nature17198] [Citation(s) in RCA: 154] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 02/02/2016] [Indexed: 02/08/2023]
Abstract
(β-)Arrestins are important regulators of G-protein-coupled receptors (GPCRs). They bind to active, phosphorylated GPCRs and thereby shut off 'classical' signalling to G proteins, trigger internalization of GPCRs via interaction with the clathrin machinery and mediate signalling via 'non-classical' pathways. In addition to two visual arrestins that bind to rod and cone photoreceptors (termed arrestin1 and arrestin4), there are only two (non-visual) β-arrestin proteins (β-arrestin1 and β-arrestin2, also termed arrestin2 and arrestin3), which regulate hundreds of different (non-visual) GPCRs. Binding of these proteins to GPCRs usually requires the active form of the receptors plus their phosphorylation by G-protein-coupled receptor kinases (GRKs). The binding of receptors or their carboxy terminus as well as certain truncations induce active conformations of (β-)arrestins that have recently been solved by X-ray crystallography. Here we investigate both the interaction of β-arrestin with GPCRs, and the β-arrestin conformational changes in real time and in living human cells, using a series of fluorescence resonance energy transfer (FRET)-based β-arrestin2 biosensors. We observe receptor-specific patterns of conformational changes in β-arrestin2 that occur rapidly after the receptor-β-arrestin2 interaction. After agonist removal, these changes persist for longer than the direct receptor interaction. Our data indicate a rapid, receptor-type-specific, two-step binding and activation process between GPCRs and β-arrestins. They further indicate that β-arrestins remain active after dissociation from receptors, allowing them to remain at the cell surface and presumably signal independently. Thus, GPCRs trigger a rapid, receptor-specific activation/deactivation cycle of β-arrestins, which permits their active signalling.
Collapse
|
21
|
Lu J, Li J. Label-Free Imaging of Dynamic and Transient Calcium Signaling in Single Cells. Angew Chem Int Ed Engl 2015; 54:13576-80. [PMID: 26337802 DOI: 10.1002/anie.201505991] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Indexed: 01/12/2023]
Abstract
Cell signaling consists of diverse events that occur at various temporal and spatial scales, ranging from milliseconds to hours and from single biomolecules to cell populations. The pathway complexities require the development of new techniques that detect the overall signaling activities and are not limited to quantifying a single event. A plasmonic-based electrochemical impedance microscope (P-EIM) that can provide such data with excellent temporal and spatial resolution and does not require the addition of any labels for detection has now been developed. The highly dynamic and transient calcium signaling activities at the early stage of G-protein-coupled receptor (GPCR) stimulation were thus studied. It could be shown that a subpopulation of cells is more responsive towards agonist stimulation, and the heterogeneity of the local distributions and the transient activities of the ion channels during agonist-activated calcium flux in single HeLa cells were investigated.
Collapse
Affiliation(s)
- Jin Lu
- Department of Chemistry, Beijing Key Laboratory for Microanalytical Methods and Instrumentation, Tsinghua University, Beijing 100084 (China)
| | - Jinghong Li
- Department of Chemistry, Beijing Key Laboratory for Microanalytical Methods and Instrumentation, Tsinghua University, Beijing 100084 (China).
| |
Collapse
|
22
|
Lu J, Li J. Label-Free Imaging of Dynamic and Transient Calcium Signaling in Single Cells. Angew Chem Int Ed Engl 2015. [DOI: 10.1002/ange.201505991] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
|
23
|
Abstract
Adrenergic signaling, in particular signaling in the sympathetic nervous system, is a prime example of the control of an essential physiological system. It has served as a model system both for the control of mediator release and for receptor signaling and regulation. This review covers the historical development of the field and then addresses issues that represent key fields of ongoing research: the mechanisms and kinetics of receptor activation, temporal patterns of downstream signaling and signal bias, receptor mobility and aggregation, and signal compartmentation and specificity. The available evidence suggests that adrenergic signaling may involve complex spatiotemporal patterns, which give texture to the signaling process and may contain additional biological information.
Collapse
Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Str. 9, 97078, Würzburg, Germany.
- Rudolf Virchow Center, University of Würzburg, Versbacher Str. 9, 97078, Würzburg, Germany.
- Comprehensive Heart Failure Center, University of Würzburg, Versbacher Str. 9, 97078, Würzburg, Germany.
| |
Collapse
|
24
|
Lohse MJ, Hofmann KP. Spatial and Temporal Aspects of Signaling by G-Protein-Coupled Receptors. Mol Pharmacol 2015; 88:572-8. [PMID: 26184590 DOI: 10.1124/mol.115.100248] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2015] [Accepted: 07/10/2015] [Indexed: 01/07/2023] Open
Abstract
Signaling by G-protein-coupled receptors is often considered a uniform process, whereby a homogeneously activated proportion of randomly distributed receptors are activated under equilibrium conditions and produce homogeneous, steady-state intracellular signals. While this may be the case in some biologic systems, the example of rhodopsin with its strictly local single-quantum mode of function shows that homogeneity in space and time cannot be a general property of G-protein-coupled systems. Recent work has now revealed many other systems where such simplicity does not prevail. Instead, a plethora of mechanisms allows much more complex patterns of receptor activation and signaling: different mechanisms of protein-protein interaction; temporal changes under nonequilibrium conditions; localized receptor activation; and localized second messenger generation and degradation-all of which shape receptor-generated signals and permit the creation of multiple signal types. Here, we review the evidence for such pleiotropic receptor signaling in space and time.
Collapse
Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, Rudolf Virchow Center, and Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany (M.J.L.); Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Berlin, Germany (K.P.H.); and Zentrum für Biophysik und Bioinformatik, Humboldt-Universität zu Berlin, Berlin, Germany (K.P.H.)
| | - Klaus Peter Hofmann
- Institute of Pharmacology and Toxicology, Rudolf Virchow Center, and Comprehensive Heart Failure Center, University of Würzburg, Würzburg, Germany (M.J.L.); Institut für Medizinische Physik und Biophysik (CC2), Charité-Universitätsmedizin Berlin, Berlin, Germany (K.P.H.); and Zentrum für Biophysik und Bioinformatik, Humboldt-Universität zu Berlin, Berlin, Germany (K.P.H.)
| |
Collapse
|
25
|
Dascal N, Kahanovitch U. The Roles of Gβγ and Gα in Gating and Regulation of GIRK Channels. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2015; 123:27-85. [DOI: 10.1016/bs.irn.2015.06.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
|
26
|
Calebiro D, Maiellaro I. cAMP signaling microdomains and their observation by optical methods. Front Cell Neurosci 2014; 8:350. [PMID: 25389388 PMCID: PMC4211404 DOI: 10.3389/fncel.2014.00350] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 10/07/2014] [Indexed: 11/22/2022] Open
Abstract
The second messenger cyclic AMP (cAMP) is a major intracellular mediator of many hormones and neurotransmitters and regulates a myriad of cell functions, including synaptic plasticity in neurons. Whereas cAMP can freely diffuse in the cytosol, a growing body of evidence suggests the formation of cAMP gradients and microdomains near the sites of cAMP production, where cAMP signals remain apparently confined. The mechanisms responsible for the formation of such microdomains are subject of intensive investigation. The development of optical methods based on fluorescence resonance energy transfer (FRET), which allow a direct observation of cAMP signaling with high temporal and spatial resolution, is playing a fundamental role in elucidating the nature of such microdomains. Here, we will review the optical methods used for monitoring cAMP and protein kinase A (PKA) signaling in living cells, providing some examples of their application in neurons, and will discuss the major hypotheses on the formation of cAMP/PKA microdomains.
Collapse
Affiliation(s)
- Davide Calebiro
- Institute of Pharmacology and Toxicology, University of Würzburg Würzburg, Germany ; Bio-Imaging Center/Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg Würzburg, Germany
| | - Isabella Maiellaro
- Institute of Pharmacology and Toxicology, University of Würzburg Würzburg, Germany ; Bio-Imaging Center/Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg Würzburg, Germany
| |
Collapse
|
27
|
Abstract
It has been widely assumed that the production of the ubiquitous second messenger cyclic AMP, which is mediated by cell surface G protein–coupled receptors (GPCRs), and its termination take place exclusively at the plasma membrane. Recent studies reveal that diverse GPCRs do not always follow this conventional paradigm. In the new model, GPCRs mediate G-protein signaling not only from the plasma membrane but also from endosomal membranes. This model proposes that following ligand binding and activation, cell surface GPCRs internalize and redistribute into early endosomes, where trimeric G protein signaling can be maintained for an extended period of time. This Perspective discusses the molecular and cellular mechanistic subtleties as well as the physiological consequences of this unexpected process, which is considerably changing how we think about GPCR signaling and regulation and how we study drugs that target this receptor family.
Collapse
|
28
|
Asymmetric perturbations of signalling oligomers. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2014; 114:153-69. [PMID: 24650570 DOI: 10.1016/j.pbiomolbio.2014.03.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2013] [Revised: 02/26/2014] [Accepted: 03/04/2014] [Indexed: 01/06/2023]
Abstract
This review focuses on rapid and reversible noncovalent interactions for symmetric oligomers of signalling proteins. Symmetry mismatch, transient symmetry breaking and asymmetric perturbations via chemical (ligand binding) and physical (electric or mechanic) effects can initiate the signalling events. Advanced biophysical methods can reveal not only structural symmetries of stable membrane-bound signalling proteins but also asymmetric functional transition states. Relevant techniques amenable to distinguish between symmetric and asymmetric architectures are discussed including those with the capability of capturing low-populated transient conformational states. Typical examples of signalling proteins are overviewed for symmetry breaking in dimers (GPCRs, growth factor receptors, transcription factors); trimers (acid-sensing ion channels); tetramers (voltage-gated cation channels, ionotropic glutamate receptor, CNG and CHN channels); pentameric ligand-gated and mechanosensitive channels; higher order oligomers (gap junction channel, chaperonins, proteasome, virus capsid); as well as primary and secondary transporters. In conclusion, asymmetric perturbations seem to play important functional roles in a broad range of communicating networks.
Collapse
|
29
|
Cahill E, Salery M, Vanhoutte P, Caboche J. Convergence of dopamine and glutamate signaling onto striatal ERK activation in response to drugs of abuse. Front Pharmacol 2014; 4:172. [PMID: 24409148 PMCID: PMC3884214 DOI: 10.3389/fphar.2013.00172] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2013] [Accepted: 12/19/2013] [Indexed: 12/31/2022] Open
Abstract
Despite their distinct targets, all addictive drugs commonly abused by humans evoke increases in dopamine (DA) concentration within the striatum. The main DA Guanine nucleotide binding protein couple receptors (GPCRs) expressed by medium-sized spiny neurons of the striatum are the D1R and D2R, which are positively and negatively coupled to cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling, respectively. These two DA GPCRs are largely segregated into distinct neuronal populations, where they are co-expressed with glutamate receptors in dendritic spines. Direct and indirect interactions between DA GPCRs and glutamate receptors are the molecular basis by which DA modulates glutamate transmission and controls striatal plasticity and behavior induced by drugs of abuse. A major downstream target of striatal D1R is the extracellular signal-regulated kinase (ERK) kinase pathway. ERK activation by drugs of abuse behaves as a key integrator of D1R and glutamate NMDAR signaling. Once activated, ERK can trigger chromatin remodeling and induce gene expression that permits long-term cellular alterations and drug-induced morphological and behavioral changes. Besides the classical cAMP/PKA pathway, downstream of D1R, recent evidence implicates a cAMP-independent crosstalk mechanism by which the D1R potentiates NMDAR-mediated calcium influx and ERK activation. The mounting evidence of reciprocal modulation of DA and glutamate receptors adds further intricacy to striatal synaptic signaling and is liable to prove relevant for addictive drug-induced signaling, plasticity, and behavior. Herein, we review the evidence that built our understanding of the consequences of this synergistic signaling for the actions of drugs of abuse.
Collapse
Affiliation(s)
- Emma Cahill
- UMRS 952, INSERM, Physiopathologie des Maladies du Système Nerveux Central Paris, France ; UMR7224, CNRS, Physiopathologie des Maladies du Système Nerveux Central Paris, France ; University Pierre and Marie Curie-Paris 6 Paris, France
| | - Marine Salery
- UMRS 952, INSERM, Physiopathologie des Maladies du Système Nerveux Central Paris, France ; UMR7224, CNRS, Physiopathologie des Maladies du Système Nerveux Central Paris, France ; University Pierre and Marie Curie-Paris 6 Paris, France
| | - Peter Vanhoutte
- UMRS 952, INSERM, Physiopathologie des Maladies du Système Nerveux Central Paris, France ; UMR7224, CNRS, Physiopathologie des Maladies du Système Nerveux Central Paris, France ; University Pierre and Marie Curie-Paris 6 Paris, France
| | - Jocelyne Caboche
- UMRS 952, INSERM, Physiopathologie des Maladies du Système Nerveux Central Paris, France ; UMR7224, CNRS, Physiopathologie des Maladies du Système Nerveux Central Paris, France ; University Pierre and Marie Curie-Paris 6 Paris, France
| |
Collapse
|
30
|
Sridharan R, Zuber J, Connelly SM, Mathew E, Dumont ME. Fluorescent approaches for understanding interactions of ligands with G protein coupled receptors. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1838:15-33. [PMID: 24055822 PMCID: PMC3926105 DOI: 10.1016/j.bbamem.2013.09.005] [Citation(s) in RCA: 86] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2013] [Revised: 09/03/2013] [Accepted: 09/08/2013] [Indexed: 11/18/2022]
Abstract
G protein coupled receptors are responsible for a wide variety of signaling responses in diverse cell types. Despite major advances in the determination of structures of this class of receptors, the underlying mechanisms by which binding of different types of ligands specifically elicits particular signaling responses remain unclear. The use of fluorescence spectroscopy can provide important information about the process of ligand binding and ligand dependent conformational changes in receptors, especially kinetic aspects of these processes that can be difficult to extract from X-ray structures. We present an overview of the extensive array of fluorescent ligands that have been used in studies of G protein coupled receptors and describe spectroscopic approaches for assaying binding and probing the environment of receptor-bound ligands with particular attention to examples involving yeast pheromone receptors. In addition, we discuss the use of fluorescence spectroscopy for detecting and characterizing conformational changes in receptors induced by the binding of ligands. Such studies have provided strong evidence for diversity of receptor conformations elicited by different ligands, consistent with the idea that GPCRs are not simple on and off switches. This diversity of states constitutes an underlying mechanistic basis for biased agonism, the observation that different stimuli can produce different responses from a single receptor. It is likely that continued technical advances will allow fluorescence spectroscopy to play an important role in continued probing of structural transitions in G protein coupled receptors. This article is part of a Special Issue entitled: Structural and biophysical characterisation of membrane protein-ligand binding.
Collapse
Affiliation(s)
- Rajashri Sridharan
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
| | - Jeffrey Zuber
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
| | - Sara M. Connelly
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
| | - Elizabeth Mathew
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
| | - Mark E. Dumont
- Department of Biochemistry and Biophysics, P.O. Box 712, University of Rochester Medical Center, Rochester, NY 14642
- Department of Pediatrics, P.O. Box 777, University of Rochester Medical Center, Rochester, NY 14642
| |
Collapse
|
31
|
Abstract
G-protein-coupled receptors (GPCRs) are the primary interaction partners for arrestins. The visual arrestins, arrestin1 and arrestin4, physiologically bind to only very few receptors, i.e., rhodopsin and the color opsins, respectively. In contrast, the ubiquitously expressed nonvisual variants β-arrestin1 and 2 bind to a large number of receptors in a fairly nonspecific manner. This binding requires two triggers, agonist activation and receptor phosphorylation by a G-protein-coupled receptor kinase (GRK). These two triggers are mediated by two different regions of the arrestins, the "phosphorylation sensor" in the core of the protein and a less well-defined "activation sensor." Binding appears to occur mostly in a 1:1 stoichiometry, involving the N-terminal domain of GPCRs, but in addition a second GPCR may loosely bind to the C-terminal domain when active receptors are abundant.Arrestin binding initially uncouples GPCRs from their G-proteins. It stabilizes receptors in an active conformation and also induces a conformational change in the arrestins that involves a rotation of the two domains relative to each other plus changes in the polar core. This conformational change appears to permit the interaction with further downstream proteins. The latter interaction, demonstrated mostly for β-arrestins, triggers receptor internalization as well as a number of nonclassical signaling pathways.Open questions concern the exact stoichiometry of the interaction, possible specificity with regard to the type of agonist and of GRK involved, selective regulation of downstream signaling (=biased signaling), and the options to use these mechanisms as therapeutic targets.
Collapse
Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, University of Würzburg, Versbacher Straße 9, 97078, Würzburg, Germany,
| | | |
Collapse
|
32
|
Lohse MJ, Maiellaro I, Calebiro D. Kinetics and mechanism of G protein-coupled receptor activation. Curr Opin Cell Biol 2013; 27:87-93. [PMID: 24530699 DOI: 10.1016/j.ceb.2013.11.009] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Accepted: 11/24/2013] [Indexed: 10/25/2022]
Abstract
The activation of a G protein-coupled receptor is generally triggered by binding of an agonist to the receptor's binding pocket, or, in the case of rhodopsin, by light-induced changes of the pre-bound retinal. This is followed by a series of a conformational changes towards an active receptor conformation, which is capable of signalling to G proteins and other downstream proteins. In the past few years, a number of new techniques have been employed to analyze the kinetics of this activation process, including X-ray crystallographic three-dimensional structures of receptors in the inactive and the active states, NMR studies of labelled receptors, molecular simulations, and optical analyses with fluorescence resonance energy transfer (FRET). Here we review our current understanding of the activation process of GPCRs as well as open questions in the sequence of events ranging from (sub-)microsecond activation by light or agonist binding to millisecond activation of receptors by soluble ligands and the subsequent generation of an intracellular signal.
Collapse
Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, University of Würzburg, 97078 Würzburg, Germany; Rudolf Virchow Center, DFG-Research Center for Experimental Biomedicine, University of Würzburg, 97078 Würzburg, Germany.
| | - Isabella Maiellaro
- Institute of Pharmacology and Toxicology, University of Würzburg, 97078 Würzburg, Germany; Rudolf Virchow Center, DFG-Research Center for Experimental Biomedicine, University of Würzburg, 97078 Würzburg, Germany
| | - Davide Calebiro
- Institute of Pharmacology and Toxicology, University of Würzburg, 97078 Würzburg, Germany; Rudolf Virchow Center, DFG-Research Center for Experimental Biomedicine, University of Würzburg, 97078 Würzburg, Germany
| |
Collapse
|
33
|
Croker DE, Halai R, Fairlie DP, Cooper MA. C5a, but not C5a-des Arg, induces upregulation of heteromer formation between complement C5a receptors C5aR and C5L2. Immunol Cell Biol 2013; 91:625-33. [PMID: 24060963 DOI: 10.1038/icb.2013.48] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2013] [Revised: 08/21/2013] [Accepted: 08/22/2013] [Indexed: 11/09/2022]
Abstract
Receptors for C5a have an important role in innate immunity and inflammation where their expression and activation is tightly regulated. There are two known receptors for C5a: the C5a receptor (C5aR) and the C5a receptor like-2 (C5L2) receptor. Here we hypothesized that activation of C5aR might lead to heteromer formation with C5L2, as a downregulatory mechanism for C5aR signaling. To investigate this experimentally, bioluminescent resonance energy transfer (BRET) was implemented and supported by wide-field microscopy to analyze receptor localization in transfected HEK293 cells and human monocyte-derived macrophages (HMDM). BRET experiments indicated the presence of constitutive C5aR-C5L2 heteromers, where C5a, but not C5a-des Arg, was able to induce further heteromer formation, which was inhibited by a C5aR-specific antagonist. The data obtained suggest that C5aR-C5L2 can form heteromers in a process enhanced by C5a, but not by C5a-des Arg. There was also a significant difference in the levels of the anti-inflammatory cytokine IL-10 detected in HMDM following exposure to C5a compared with that seen for C5a-des Arg but no differences in the pro-inflammatory cytokines TNFα and IL-6. These subtle differences in C5a and C5a-des Arg induced receptor function may be of benefit in understanding the regulation of C5a in acute inflammation.
Collapse
Affiliation(s)
- Daniel E Croker
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, Queensland, Australia
| | | | | | | |
Collapse
|
34
|
Bubnell J, Pfister P, Sapar ML, Rogers ME, Feinstein P. β2 adrenergic receptor fluorescent protein fusions traffic to the plasma membrane and retain functionality. PLoS One 2013; 8:e74941. [PMID: 24086401 PMCID: PMC3781101 DOI: 10.1371/journal.pone.0074941] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2013] [Accepted: 08/07/2013] [Indexed: 11/29/2022] Open
Abstract
Green fluorescent protein (GFP) has proven useful for the study of protein interactions and dynamics for the last twenty years. A variety of new fluorescent proteins have been developed that expand the use of available excitation spectra. We have undertaken an analysis of seven of the most useful fluorescent proteins (XFPs), Cerulean (and mCerulean3), Teal, GFP, Venus, mCherry and TagRFP657, as fusions to the archetypal G-protein coupled receptor, the β2 adrenergic receptor (β2AR). We have characterized these β2AR::XFP fusions in respect to membrane trafficking and G-protein activation. We noticed that in the mouse neural cell line, OP 6, that membrane bound β2AR::XFP fusions robustly localized in the filopodia identical to gap::XFP fusions. All β2AR::XFP fusions show responses indistinguishable from each other and the non-fused form after isoprenaline exposure. Our results provide a platform by which G-protein coupled receptors can be dissected for their functionality.
Collapse
Affiliation(s)
- Jaclyn Bubnell
- Department of Biological Sciences, Hunter College and The Graduate Center Biochemistry, Biology and Biopsychology and Behavioral Neuroscience Programs, CUNY, New York, New York, United States of America
| | - Patrick Pfister
- Corporate Research and Development, Firmenich Inc., Plainsboro, New Jersey, United States of America
| | - Maria L. Sapar
- Department of Biological Sciences, Hunter College and The Graduate Center Biochemistry, Biology and Biopsychology and Behavioral Neuroscience Programs, CUNY, New York, New York, United States of America
| | - Matthew E. Rogers
- Corporate Research and Development, Firmenich Inc., Plainsboro, New Jersey, United States of America
| | - Paul Feinstein
- Department of Biological Sciences, Hunter College and The Graduate Center Biochemistry, Biology and Biopsychology and Behavioral Neuroscience Programs, CUNY, New York, New York, United States of America
- * E-mail:
| |
Collapse
|
35
|
Zhang XC, Sun K, Zhang L, Li X, Cao C. GPCR activation: protonation and membrane potential. Protein Cell 2013; 4:747-60. [PMID: 24057762 DOI: 10.1007/s13238-013-3073-2] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2013] [Accepted: 09/11/2013] [Indexed: 12/22/2022] Open
Abstract
GPCR proteins represent the largest family of signaling membrane proteins in eukaryotic cells. Their importance to basic cell biology, human diseases, and pharmaceutical interventions is well established. Many crystal structures of GPCR proteins have been reported in both active and inactive conformations. These data indicate that agonist binding alone is not sufficient to trigger the conformational change of GPCRs necessary for binding of downstream G-proteins, yet other essential factors remain elusive. Based on analysis of available GPCR crystal structures, we identified a potential conformational switch around the conserved Asp2.50, which consistently shows distinct conformations between inactive and active states. Combining the structural information with the current literature, we propose an energy-coupling mechanism, in which the interaction between a charge change of the GPCR protein and the membrane potential of the living cell plays a key role for GPCR activation.
Collapse
Affiliation(s)
- Xuejun C Zhang
- National Laboratory of Macromolecules, National Center for Protein Science-Beijing, Institute of Biophysics, Chinese Academy of Sciences, Beijing, 100101, China,
| | | | | | | | | |
Collapse
|
36
|
Deng H, Sun H, Fang Y. Label-free cell phenotypic assessment of the biased agonism and efficacy of agonists at the endogenous muscarinic M3 receptors. J Pharmacol Toxicol Methods 2013; 68:323-33. [PMID: 23933114 DOI: 10.1016/j.vascn.2013.07.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 07/26/2013] [Accepted: 07/30/2013] [Indexed: 01/14/2023]
Abstract
INTRODUCTION Efficacy describes the property of a ligand that enables the receptor to change its behavior towards the host cell, while biased agonism defines the ability of a ligand to differentially activate some of the vectorial pathways over others mediated through the receptor. However, little is known about the molecular basis defining the efficacy of ligands at G protein-coupled receptors. Here we characterize the biased agonism and cell phenotypic efficacy of seven agonists at the endogenous muscarinic M3 receptors in six different cell lines including HT-29, PC-3, HeLa, SF268, CCRF-CEM and HCT-15 cells. METHODS Quantitative real-time PCR and multiple label-free whole cell dynamic mass redistribution (DMR) assays were used to determine the functional muscarinic receptors in each cell line. DMR pathway deconvolution assay was used to determine the pathway biased activity of the muscarinic agonists. Operational agonism model was used to quantify the pathway bias, while macro-kinetic data reported in literature was used to analyze the biochemical mechanism of action of these agonists. RESULTS Quantitative real-time PCR and ligand pharmacology studies showed that all the native cell lines endogenously express functional M3 receptors. Furthermore, different agonists triggered distinct DMR signals in a specific cell line as well as in different cell lines. DMR pathway deconvolution using known G protein modulators revealed that the M3 receptor in all the six cell lines signals through multiple G protein-mediated pathways, and certain agonists display biased agonism in a cell line-dependent manner. The whole cell efficacy and potency of these agonists were found to be sensitive to the assay time as well as the cell background. Correlation analysis suggested that the whole cell efficacy of agonists is correlated well with their macro-dissociation rate constants. DISCUSSION This study implicates that the endogenous M3 receptors are coupled to multiple pathways, and the muscarinic agonists can display distinct biased agonism and whole cell phenotypic efficacy.
Collapse
Affiliation(s)
- Huayun Deng
- Biochemical Technologies, Science and Technology Division, Corning Incorporated, Corning, NY 14831, United States
| | | | | |
Collapse
|
37
|
Illuminating the activation mechanisms and allosteric properties of metabotropic glutamate receptors. Proc Natl Acad Sci U S A 2013; 110:E1416-25. [PMID: 23487753 DOI: 10.1073/pnas.1215615110] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In multimeric cell-surface receptors, the conformational changes of the extracellular ligand-binding domains (ECDs) associated with receptor activation remain largely unknown. This is the case for the dimeric metabotropic glutamate receptors even though a number of ECD structures have been solved. Here, using an innovative approach based on cell-surface labeling and FRET, we demonstrate that a reorientation of the ECDs is associated with receptor and G-protein activation. Our approach helps identify partial agonists and highlights allosteric interactions between the effector and binding domains. Any approach expected to stabilize the active conformation of the effector domain increased the agonist potency in stabilizing the active ECDs conformation. These data provide key information on the structural dynamics and drug action at metabotropic glutamate receptors and validate an approach for tackling such analysis on other receptors.
Collapse
|
38
|
Vilardaga JP, Romero G, Feinstein TN, Wehbi VL. Kinetics and dynamics in the G protein-coupled receptor signaling cascade. Methods Enzymol 2013; 522:337-63. [PMID: 23374192 DOI: 10.1016/b978-0-12-407865-9.00016-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
We describe optical and microscopy methods based on Förster resonance energy transfer, fluorescence recovery after photobleaching, and imaging cross-correlation spectroscopy that permit to determine kinetic and dynamic properties of key reactions involved G protein-coupled receptor (GPCR) signaling from the initial ligand binding step to the generation of the second messenger, cAMP. Well suited to determine rate-limiting reactions taking place along a GPCR signaling cascade in live cells, these techniques have also uncovered new concepts in GPCR signaling as well as many interesting mechanistic subtleties by which GPCRs transmit neurotransmitter and hormone signals into cells.
Collapse
Affiliation(s)
- Jean-Pierre Vilardaga
- Laboratory for GPCR Biology, Department of Pharmacology and Chemical Biology, University of Pittsburgh, School of Medicine, Pittsburgh, Pennsylvania, USA.
| | | | | | | |
Collapse
|
39
|
Single-molecule analysis of fluorescently labeled G-protein-coupled receptors reveals complexes with distinct dynamics and organization. Proc Natl Acad Sci U S A 2012; 110:743-8. [PMID: 23267088 DOI: 10.1073/pnas.1205798110] [Citation(s) in RCA: 329] [Impact Index Per Article: 27.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
G-protein-coupled receptors (GPCRs) constitute the largest family of receptors and major pharmacological targets. Whereas many GPCRs have been shown to form di-/oligomers, the size and stability of such complexes under physiological conditions are largely unknown. Here, we used direct receptor labeling with SNAP-tags and total internal reflection fluorescence microscopy to dynamically monitor single receptors on intact cells and thus compare the spatial arrangement, mobility, and supramolecular organization of three prototypical GPCRs: the β(1)-adrenergic receptor (β(1)AR), the β(2)-adrenergic receptor (β(2)AR), and the γ-aminobutyric acid (GABA(B)) receptor. These GPCRs showed very different degrees of di-/oligomerization, lowest for β(1)ARs (monomers/dimers) and highest for GABA(B) receptors (prevalently dimers/tetramers of heterodimers). The size of receptor complexes increased with receptor density as a result of transient receptor-receptor interactions. Whereas β(1)-/β(2)ARs were apparently freely diffusing on the cell surface, GABA(B) receptors were prevalently organized into ordered arrays, via interaction with the actin cytoskeleton. Agonist stimulation did not alter receptor di-/oligomerization, but increased the mobility of GABA(B) receptor complexes. These data provide a spatiotemporal characterization of β(1)-/β(2)ARs and GABA(B) receptors at single-molecule resolution. The results suggest that GPCRs are present on the cell surface in a dynamic equilibrium, with constant formation and dissociation of new receptor complexes that can be targeted, in a ligand-regulated manner, to different cell-surface microdomains.
Collapse
|
40
|
Araç D, Aust G, Calebiro D, Engel FB, Formstone C, Goffinet A, Hamann J, Kittel RJ, Liebscher I, Lin HH, Monk KR, Petrenko A, Piao X, Prömel S, Schiöth HB, Schwartz TW, Stacey M, Ushkaryov YA, Wobus M, Wolfrum U, Xu L, Langenhan T. Dissecting signaling and functions of adhesion G protein-coupled receptors. Ann N Y Acad Sci 2012; 1276:1-25. [PMID: 23215895 DOI: 10.1111/j.1749-6632.2012.06820.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
G protein-coupled receptors (GPCRs) comprise an expanded superfamily of receptors in the human genome. Adhesion class G protein-coupled receptors (adhesion-GPCRs) form the second largest class of GPCRs. Despite the abundance, size, molecular structure, and functions in facilitating cell and matrix contacts in a variety of organ systems, adhesion-GPCRs are by far the most poorly understood GPCR class. Adhesion-GPCRs possess a unique molecular structure, with extended N-termini containing various adhesion domains. In addition, many adhesion-GPCRs are autoproteolytically cleaved into an N-terminal fragment (NTF, NT, α-subunit) and C-terminal fragment (CTF, CT, β-subunit) at a conserved GPCR autoproteolysis-inducing (GAIN) domain that contains a GPCR proteolysis site (GPS). These two features distinguish adhesion-GPCRs from other GPCR classes. Though active research on adhesion-GPCRs in diverse areas, such as immunity, neuroscience, and development and tumor biology has been intensified in the recent years, the general biological and pharmacological properties of adhesion-GPCRs are not well known, and they have not yet been used for biomedical purposes. The "6th International Adhesion-GPCR Workshop," held at the Institute of Physiology of the University of Würzburg on September 6-8, 2012, assembled a majority of the investigators currently actively pursuing research on adhesion-GPCRs, including scientists from laboratories in Europe, the United States, and Asia. The meeting featured the nascent mechanistic understanding of the molecular events driving the signal transduction of adhesion-GPCRs, novel models to evaluate their functions, and evidence for their involvement in human disease.
Collapse
Affiliation(s)
- Demet Araç
- Stanford University, Stanford, California, USA
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Lane JR, Canals M. Sequential conformational rearrangements dictate the dynamics of class C GPCR activation. Sci Signal 2012; 5:pe51. [PMID: 23169816 DOI: 10.1126/scisignal.2003503] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Heterotrimeric GTP-binding protein (G protein)-coupled receptors (GPCRs) are the largest family of cell surface receptors; they allow cells to respond to a wide range of endogenous and environmental signals. Class C GPCRs represent a discrete group within the GPCR family, with distinct structural characteristics. Receptors belonging to this class--such as γ-aminobutyric acid type B (GABA(B)) receptors or metabotropic glutamate receptors (mGluRs)--form constitutive dimers. However, the conformational changes within such a dimeric receptor that are associated with agonist activation are still not well understood. A study by Hlavackova et al. investigates the role of dimer formation in mGluR1 activation. Using fluorescence resonance energy transfer approaches to assess inter- and intrasubunit conformational changes, the authors present an elegant study that sheds light on the kinetics of domain rearrangements in a class C GPCR upon ligand binding.
Collapse
Affiliation(s)
- J Robert Lane
- Drug Discovery Biology, Monash Institute of Pharmaceutical Sciences, and Department of Pharmacology, Monash University, Parkville, Victoria 3052, Australia
| | | |
Collapse
|
42
|
Billington CK, Hall IP. Novel cAMP signalling paradigms: therapeutic implications for airway disease. Br J Pharmacol 2012; 166:401-10. [PMID: 22013890 DOI: 10.1111/j.1476-5381.2011.01719.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Since its discovery over 50 years ago, cAMP has been the archetypal second messenger introducing students to the concept of cell signalling at the simplest level. As explored in this review, however, there are many more facets to cAMP signalling than the path from Gs-coupled receptor to adenylyl cyclase (AC) to cAMP to PKA to biological effect. After a brief description of this canonical cAMP signalling pathway, a snapshot is provided of the novel paradigms of cAMP signalling. As in the airway the cAMP pathway relays the major bronchorelaxant signal and as such is the target for frontline therapy for asthma and COPD, particular emphasis is given to airway disease and therapy. Areas discussed include biased agonism, continued signalling following internalization, modulation of cAMP by AC, control of cAMP degradation, cAMP and calcium crosstalk, Epac-mediated signalling and finally the implications of altered genotypes will be considered. LINKED ARTICLES This article is part of a themed section on Novel cAMP Signalling Paradigms. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2012.166.issue-2.
Collapse
Affiliation(s)
- Charlotte K Billington
- Division of Therapeutics and Molecular Medicine, Nottingham Respiratory Biomedical Research Unit, The University of Nottingham, Nottingham, UK.
| | | |
Collapse
|
43
|
Hlavackova V, Zabel U, Frankova D, Bätz J, Hoffmann C, Prezeau L, Pin JP, Blahos J, Lohse MJ. Sequential inter- and intrasubunit rearrangements during activation of dimeric metabotropic glutamate receptor 1. Sci Signal 2012; 5:ra59. [PMID: 22894836 DOI: 10.1126/scisignal.2002720] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The metabotropic glutamate receptor 1 (mGluR1), a class C member of the heterotrimeric guanine nucleotide-binding protein (G protein)-coupled receptor family, is a constitutive dimer that regulates excitatory neurotransmission. We investigated the role of homodimer formation in mGluR1 activation by examining activation-dependent inter- and intrasubunit conformational changes by fluorescence resonance energy transfer (FRET). We inserted yellow and cyan fluorescent proteins in the second intracellular loop and at the carboxyl terminus of mGluR1 to act as FRET sensors and expressed these proteins in human embryonic kidney 293 cells. Agonist-dependent activation of these mGluR1 chimeras rapidly increased the intersubunit FRET, suggesting rapid movement of the subunits relative to each other. After intersubunit movement, the intrasubunit FRET decreased, reflecting conformational changes within a subunit. Cotransfection of chimeric receptor subunits that were capable or incapable of G protein coupling revealed that only a single subunit assumes an active state in an mGluR1 receptor dimer.
Collapse
Affiliation(s)
- Veronika Hlavackova
- Institute of Pharmacology and Toxicology, University of Würzburg, 97078 Würzburg, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Heitzler D, Durand G, Gallay N, Rizk A, Ahn S, Kim J, Violin JD, Dupuy L, Gauthier C, Piketty V, Crépieux P, Poupon A, Clément F, Fages F, Lefkowitz RJ, Reiter E. Competing G protein-coupled receptor kinases balance G protein and β-arrestin signaling. Mol Syst Biol 2012; 8:590. [PMID: 22735336 PMCID: PMC3397412 DOI: 10.1038/msb.2012.22] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Accepted: 05/23/2012] [Indexed: 01/14/2023] Open
Abstract
The molecular mechanisms and hidden dynamics governing ERK activation by the angiotensin II type 1A receptor are studied and deciphered, revealing a signal balancing mechanism that is found to be relevant to a range of other seven transmembrane receptors. ![]()
An ODE-based dynamical model of ERK activation by the prototypical angiotensin II type-1A seven transmembrane receptor has been built and validated. In order to deal with a limited number of experimental read-outs, unknown parameters have been inferred by simultaneously fitting control and perturbed conditions. In addition to its well-established function in G-protein uncoupling, G protein-coupled receptor kinase 2 has been shown to exert a strong negative effect on β-arrestin-dependent signaling and by doing so, to balance G-protein and β-arrestin signaling. This novel function of G protein-coupled receptor kinase 2 has also been evidenced in primary vascular smooth muscle cells naturally expressing the AT1AR and in HEK293 cells expressing other 7TMRs.
Seven-transmembrane receptors (7TMRs) are involved in nearly all aspects of chemical communications and represent major drug targets. 7TMRs transmit their signals not only via heterotrimeric G proteins but also through β-arrestins, whose recruitment to the activated receptor is regulated by G protein-coupled receptor kinases (GRKs). In this paper, we combined experimental approaches with computational modeling to decipher the molecular mechanisms as well as the hidden dynamics governing extracellular signal-regulated kinase (ERK) activation by the angiotensin II type 1A receptor (AT1AR) in human embryonic kidney (HEK)293 cells. We built an abstracted ordinary differential equations (ODE)-based model that captured the available knowledge and experimental data. We inferred the unknown parameters by simultaneously fitting experimental data generated in both control and perturbed conditions. We demonstrate that, in addition to its well-established function in the desensitization of G-protein activation, GRK2 exerts a strong negative effect on β-arrestin-dependent signaling through its competition with GRK5 and 6 for receptor phosphorylation. Importantly, we experimentally confirmed the validity of this novel GRK2-dependent mechanism in both primary vascular smooth muscle cells naturally expressing the AT1AR, and HEK293 cells expressing other 7TMRs.
Collapse
Affiliation(s)
- Domitille Heitzler
- BIOS Group, INRA, UMR85, Unité Physiologie de la Reproduction et des Comportements, Nouzilly, France
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Lohse MJ, Nuber S, Hoffmann C. Fluorescence/bioluminescence resonance energy transfer techniques to study G-protein-coupled receptor activation and signaling. Pharmacol Rev 2012; 64:299-336. [PMID: 22407612 DOI: 10.1124/pr.110.004309] [Citation(s) in RCA: 251] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Fluorescence and bioluminescence resonance energy transfer (FRET and BRET) techniques allow the sensitive monitoring of distances between two labels at the nanometer scale. Depending on the placement of the labels, this permits the analysis of conformational changes within a single protein (for example of a receptor) or the monitoring of protein-protein interactions (for example, between receptors and G-protein subunits). Over the past decade, numerous such techniques have been developed to monitor the activation and signaling of G-protein-coupled receptors (GPCRs) in both the purified, reconstituted state and in intact cells. These techniques span the entire spectrum from ligand binding to the receptors down to intracellular second messengers. They allow the determination and the visualization of signaling processes with high temporal and spatial resolution. With these techniques, it has been demonstrated that GPCR signals may show spatial and temporal patterning. In particular, evidence has been provided for spatial compartmentalization of GPCRs and their signals in intact cells and for distinct physiological consequences of such spatial patterning. We review here the FRET and BRET technologies that have been developed for G-protein-coupled receptors and their signaling proteins (G-proteins, effectors) and the concepts that result from such experiments.
Collapse
Affiliation(s)
- Martin J Lohse
- Institute of Pharmacology and Toxicology, Versbacher Str. 9, 97078 Würzburg, Germany.
| | | | | |
Collapse
|
46
|
Xu TR, Ward RJ, Pediani JD, Milligan G. Intramolecular fluorescence resonance energy transfer (FRET) sensors of the orexin OX1 and OX2 receptors identify slow kinetics of agonist activation. J Biol Chem 2012; 287:14937-49. [PMID: 22389503 DOI: 10.1074/jbc.m111.334300] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
Intramolecular fluorescence resonance energy transfer (FRET) sensors able to detect changes in distance or orientation between the 3rd intracellular loop and C-terminal tail of the human orexin OX(1) and OX(2) G protein-coupled receptors following binding of agonist ligands were produced and expressed stably. These were directed to the plasma membrane and, despite the substantial sequence alterations introduced, in each case were able to elevate [Ca(2+)](i), promote phosphorylation of the ERK1/2 MAP kinases and become internalized effectively upon addition of the native orexin peptides. Detailed characterization of the OX(1) sensor demonstrated that it was activated with rank order of potency orexin A > orexin B > orexin A 16-33, that it bound antagonist ligands with affinity similar to the wild-type receptor, and that mutation of a single residue, D203A, greatly reduced the binding and function of orexin A but not antagonist ligands. Addition of orexin A to individual cells expressing an OX(1) sensor resulted in a time- and concentration-dependent reduction in FRET signal consistent with mass-action and potency/affinity estimates for the peptide. Compared with the response kinetics of a muscarinic M(3) acetylcholine receptor sensor upon addition of agonist, response of the OX(1) and OX(2) sensors to orexin A was slow, consistent with a multistep binding and activation process. Such sensors provide means to assess the kinetics of receptor activation and how this may be altered by mutation and sequence variation of the receptors.
Collapse
Affiliation(s)
- Tian-Rui Xu
- Molecular Pharmacology Group, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, United Kingdom
| | | | | | | |
Collapse
|
47
|
Ambrosio M, Lohse MJ. Nonequilibrium activation of a G-protein-coupled receptor. Mol Pharmacol 2012; 81:770-7. [PMID: 22379120 DOI: 10.1124/mol.112.077693] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
G-protein-coupled receptor activation is generally analyzed under equilibrium conditions. However, real-life receptor functions are often dependent on very short, transient stimuli that may not allow the achievement of a steady state. This is particularly true for synaptic receptors such as the α(2A)-adrenergic receptor (α(2A)-AR). Therefore, we developed a fluorescence resonance energy transfer-based technology to study nonequilibrium α(2A)-AR function in living cells. To examine the effects of increasing concentrations of the endogenous agonist norepinephrine on the speed and extent of α(2A)-AR activation with very high temporal resolution, we took advantage of a fluorophore-containing α(2A)-AR sensor. The results indicated that the efficacy of norepinephrine in eliciting receptor activation increased in a time-dependent way, reaching the maximum with a half-life of ~60 ms. The EC(50) values under nonequilibrium conditions start at ~26 μM (at 40 ms) and show a 10-fold decrease until the steady state is achieved. To analyze the ability of norepinephrine to trigger a downstream intracellular response after α(2A)-AR stimulation, we monitored the kinetics and amplitude of G(i) activation in real time by using a fluorophore-containing G(i) sensor. The results show that both the efficacy and the potency of norepinephrine in inducing G(i) activation achieve a steady state more slowly, compared with receptor activation, and that the initial EC(50) value of ~100 nM decreases in an exponential way, reaching the minimal value of ~10 nM at equilibrium. Therefore, both the efficacy and the potency of norepinephrine increase ~10-fold over a few seconds of agonist stimulation, which illustrates that receptor and G-protein signaling and signal amplification are highly time-dependent phenomena.
Collapse
Affiliation(s)
- Manuela Ambrosio
- Institute of Pharmacology and Toxicology, University of Würzburg, Würzburg, Germany
| | | |
Collapse
|
48
|
Prakash A, Luthra PM. Insilico study of the A2AR–D2R kinetics and interfacial contact surface for heteromerization. Amino Acids 2012; 43:1451-64. [DOI: 10.1007/s00726-012-1218-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Accepted: 01/04/2012] [Indexed: 12/28/2022]
|
49
|
Markovic D, Holdich J, Al-Sabah S, Mistry R, Krasel C, Mahaut-Smith MP, Challiss RAJ. FRET-based detection of M1 muscarinic acetylcholine receptor activation by orthosteric and allosteric agonists. PLoS One 2012; 7:e29946. [PMID: 22272263 PMCID: PMC3260180 DOI: 10.1371/journal.pone.0029946] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2011] [Accepted: 12/07/2011] [Indexed: 01/30/2023] Open
Abstract
Background and Objective Muscarinic acetylcholine receptors (mAChRs) are 7-transmembrane, G protein-coupled receptors that regulate a variety of physiological processes and represent potentially important targets for therapeutic intervention. mAChRs can be stimulated by full and partial orthosteric and allosteric agonists, however the relative abilities of such ligands to induce conformational changes in the receptor remain unclear. To gain further insight into the actions of mAChR agonists, we have developed a fluorescently tagged M1 mAChR that reports ligand-induced conformational changes in real-time by changes in Förster resonance energy transfer (FRET). Methods Variants of CFP and YFP were inserted into the third intracellular loop and at the end of the C-terminus of the mouse M1 mAChR, respectively. The optimized FRET receptor construct (M1-cam5) was expressed stably in HEK293 cells. Results The variant CFP/YFP-receptor chimera expressed predominantly at the plasma membrane of HEK293 cells and displayed ligand-binding affinities comparable with those of the wild-type receptor. It also retained an ability to interact with Gαq/11 proteins and to stimulate phosphoinositide turnover, ERK1/2 phosphorylation and undergo agonist-dependent internalization. Addition of the full agonist methacholine caused a reversible decrease in M1 FRET (FEYFP/FECFP) that was prevented by atropine pre-addition and showed concentration-dependent amplitude and kinetics. Partial orthosteric agonists, arecoline and pilocarpine, as well as allosteric agonists, AC-42 and 77-LH-28-1, also caused atropine-sensitive decreases in the FRET signal, which were smaller in amplitude and significantly slower in onset compared to those evoked by methacholine. Conclusion The M1 FRET-based receptor chimera reports that allosteric and orthosteric agonists induce similar conformational changes in the third intracellular loop and/or C-terminus, and should prove to be a valuable molecular reagent for pharmacological and structural investigations of M1 mAChR activation.
Collapse
Affiliation(s)
- Danijela Markovic
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, United Kingdom
| | - Jonathan Holdich
- Department of Physiology, Development & Neuroscience, University of Cambridge, Cambridge, United Kingdom
| | - Suleiman Al-Sabah
- School of Pharmacy, University of Reading, Whiteknights, Reading, United Kingdom
| | - Rajendra Mistry
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, United Kingdom
| | - Cornelius Krasel
- School of Pharmacy, University of Reading, Whiteknights, Reading, United Kingdom
| | - Martyn P. Mahaut-Smith
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, United Kingdom
- Department of Physiology, Development & Neuroscience, University of Cambridge, Cambridge, United Kingdom
- * E-mail: (MPM-S); (RAJC)
| | - R. A. John Challiss
- Department of Cell Physiology and Pharmacology, University of Leicester, Leicester, United Kingdom
- * E-mail: (MPM-S); (RAJC)
| |
Collapse
|
50
|
|