1
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Nikte SV, Joshi M, Sengupta D. State-dependent dynamics of extramembrane domains in the β 2 -adrenergic receptor. Proteins 2024; 92:317-328. [PMID: 37864328 DOI: 10.1002/prot.26613] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 08/22/2023] [Accepted: 09/25/2023] [Indexed: 10/22/2023]
Abstract
G protein-coupled receptors (GPCRs) are membrane-bound signaling proteins that play an essential role in cellular signaling processes. Due to their intrinsic function of transmitting internal signals in response to external cues, these receptors are adapted to be highly dynamic in nature. The β2 -adrenergic receptor (β2 AR) is a representative member of the family that has been extensively analyzed in terms of its structure and activation. Although the structure of the transmembrane domain has been characterized in the different functional states of the receptor, the conformational dynamics of the extramembrane domains, especially the intrinsically disordered regions are still emerging. In this study, we analyze the state-dependent dynamics of extramembrane domains of β2 AR using atomistic molecular dynamics simulations. We introduce a parameter, the residue excess dynamics that allows us to better quantify receptor dynamics. Using this measure, we show that the dynamics of the extramembrane domains are sensitive to the receptor state. Interestingly, the ligand-bound intermediateR ' state shows the maximal dynamics compared to either the active R*G or inactive R states. Ligand binding appears to be correlated with high residue excess dynamics that are dampened upon G protein coupling. The intracellular loop-3 (ICL3) domain has a tendency to flip towards the membrane upon ligand binding, which could contribute to receptor "priming." We highlight an important ICL1-helix-8 interplay that is broken in the ligand-bound state but is retained in the active state. Overall, our study highlights the importance of characterizing the functional dynamics of the GPCR loop domains.
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Affiliation(s)
- Siddhanta V Nikte
- Physical and Materials Chemistry Division, National Chemical Laboratory, Pune, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
| | - Manali Joshi
- Bioinformatics Center, Savitribai Phule Pune University, Pune, India
| | - Durba Sengupta
- Physical and Materials Chemistry Division, National Chemical Laboratory, Pune, India
- Academy of Scientific and Innovative Research (AcSIR), Ghaziabad, India
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2
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Paulussen F, Kulkarni CP, Stolz F, Lescrinier E, De Graeve S, Lambin S, Marchand A, Chaltin P, In't Veld P, Mebis J, Tavernier J, Van Dijck P, Luyten W, Thevelein JM. The β2-adrenergic receptor in the apical membrane of intestinal enterocytes senses sugars to stimulate glucose uptake from the gut. Front Cell Dev Biol 2023; 10:1041930. [PMID: 36699012 PMCID: PMC9869975 DOI: 10.3389/fcell.2022.1041930] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Accepted: 12/14/2022] [Indexed: 01/12/2023] Open
Abstract
The presence of sugar in the gut causes induction of SGLT1, the sodium/glucose cotransporter in intestinal epithelial cells (enterocytes), and this is accompanied by stimulation of sugar absorption. Sugar sensing was suggested to involve a G-protein coupled receptor and cAMP - protein kinase A signalling, but the sugar receptor has remained unknown. We show strong expression and co-localization with SGLT1 of the β2-adrenergic receptor (β 2-AR) at the enterocyte apical membrane and reveal its role in stimulating glucose uptake from the gut by the sodium/glucose-linked transporter, SGLT1. Upon heterologous expression in different reporter systems, the β 2-AR responds to multiple sugars in the mM range, consistent with estimated gut sugar levels after a meal. Most adrenergic receptor antagonists inhibit sugar signaling, while some differentially inhibit epinephrine and sugar responses. However, sugars did not inhibit binding of I125-cyanopindolol, a β 2-AR antagonist, to the ligand-binding site in cell-free membrane preparations. This suggests different but interdependent binding sites. Glucose uptake into everted sacs from rat intestine was stimulated by epinephrine and sugars in a β 2-AR-dependent manner. STD-NMR confirmed direct physical binding of glucose to the β 2-AR. Oral administration of glucose with a non-bioavailable β 2-AR antagonist lowered the subsequent increase in blood glucose levels, confirming a role for enterocyte apical β 2-ARs in stimulating gut glucose uptake, and suggesting enterocyte β 2-AR as novel drug target in diabetic and obese patients. Future work will have to reveal how glucose sensing by enterocytes and neuroendocrine cells is connected, and whether β 2-ARs mediate glucose sensing also in other tissues.
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Affiliation(s)
- Frederik Paulussen
- 1Center for Microbiology, VIB, Leuven-Heverlee, Belgium,2Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
| | - Chetan P. Kulkarni
- 1Center for Microbiology, VIB, Leuven-Heverlee, Belgium,3Functional Genomics and Proteomics Research Unit, Department of Biology, KU Leuven, Leuven, Belgium
| | - Frank Stolz
- 1Center for Microbiology, VIB, Leuven-Heverlee, Belgium,2Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
| | - Eveline Lescrinier
- 4Medicinal Chemistry, Rega Institute for Medical Research, KU Leuven, Leuven, Belgium
| | - Stijn De Graeve
- 1Center for Microbiology, VIB, Leuven-Heverlee, Belgium,2Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
| | - Suzan Lambin
- 1Center for Microbiology, VIB, Leuven-Heverlee, Belgium,2Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
| | | | | | - Peter In't Veld
- 6Department of Pathology, Free University of Brussels, Brussels, Belgium
| | - Joseph Mebis
- 7Department of Pathology, KU Leuven, Flanders, Belgium
| | - Jan Tavernier
- 8Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium,9Center for Medical Biotechnology, VIB, Ghent, Belgium
| | - Patrick Van Dijck
- 1Center for Microbiology, VIB, Leuven-Heverlee, Belgium,2Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium
| | - Walter Luyten
- 3Functional Genomics and Proteomics Research Unit, Department of Biology, KU Leuven, Leuven, Belgium
| | - Johan M. Thevelein
- 1Center for Microbiology, VIB, Leuven-Heverlee, Belgium,2Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, KU Leuven, Leuven-Heverlee, Belgium,10NovelYeast bv, Bio-Incubator BIO4, Gaston Geenslaan 3, Leuven-Heverlee,, Belgium,*Correspondence: Johan M. Thevelein,
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3
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Madhu MK, Debroy A, Murarka RK. Molecular Insights into Phosphorylation-Induced Allosteric Conformational Changes in a β 2-Adrenergic Receptor. J Phys Chem B 2022; 126:1917-1932. [PMID: 35196859 DOI: 10.1021/acs.jpcb.1c08610] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The large conformational flexibility of G protein-coupled receptors (GPCRs) has been a puzzle in structural and pharmacological studies for the past few decades. Apart from structural rearrangements induced by ligands, enzymatic phosphorylations by GPCR kinases (GRKs) at the carboxy-terminal tail (C-tail) of a GPCR also make conformational alterations to the transmembrane helices and facilitates the binding of one of its transducer proteins named β-arrestin. The phosphorylation-induced conformational transition of the receptor that causes specific binding to β-arrestin but prevents the association of other transducers such as G proteins lacks atomistic understanding and is elusive to experimental studies. Using microseconds of all-atom conventional and Gaussian accelerated molecular dynamics (GaMD) simulations, we investigate the allosteric mechanism of phosphorylation induced-conformational changes in β2-adrenergic receptor, a well-characterized GPCR model system. Free energy profiles reveal that the phosphorylated receptor samples a new conformational state in addition to the canonical active state corroborating with recent nuclear magnetic resonance experimental findings. The new state has a smaller intracellular cavity that is likely to accommodate β-arrestin better than G protein. Using contact map and inter-residue interaction energy calculations, we found the phosphorylated C-tail adheres to the cytosolic surface of the transmembrane domain of the receptor. Transfer entropy calculations show that the C-tail residues drive the correlated motions of TM residues, and the allosteric signal is relayed via several residues at the cytosolic surface. Our results also illustrate how the redistribution of inter-residue nonbonding interaction couples with the allosteric communication from the phosphorylated C-tail to the transmembrane. Atomistic insight into phosphorylation-induced β-arrestin specific conformation is therapeutically important to design drugs with higher efficacy and fewer side effects. Our results, therefore, open novel opportunities to fine-tune β-arrestin bias in GPCR signaling.
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Affiliation(s)
- Midhun K Madhu
- Department of Biological Sciences, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462066, MP, India
| | - Annesha Debroy
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462066, MP, India
| | - Rajesh K Murarka
- Department of Chemistry, Indian Institute of Science Education and Research Bhopal, Bhopal Bypass Road, Bhopal 462066, MP, India
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4
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Reconstitution of β-adrenergic regulation of Ca V1.2: Rad-dependent and Rad-independent protein kinase A mechanisms. Proc Natl Acad Sci U S A 2021; 118:2100021118. [PMID: 34001616 DOI: 10.1073/pnas.2100021118] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
L-type voltage-gated CaV1.2 channels crucially regulate cardiac muscle contraction. Activation of β-adrenergic receptors (β-AR) augments contraction via protein kinase A (PKA)-induced increase of calcium influx through CaV1.2 channels. To date, the full β-AR cascade has never been heterologously reconstituted. A recent study identified Rad, a CaV1.2 inhibitory protein, as essential for PKA regulation of CaV1.2. We corroborated this finding and reconstituted the complete pathway with agonist activation of β1-AR or β2-AR in Xenopus oocytes. We found, and distinguished between, two distinct pathways of PKA modulation of CaV1.2: Rad dependent (∼80% of total) and Rad independent. The reconstituted system reproduces the known features of β-AR regulation in cardiomyocytes and reveals several aspects: the differential regulation of posttranslationally modified CaV1.2 variants and the distinct features of β1-AR versus β2-AR activity. This system allows for the addressing of central unresolved issues in the β-AR-CaV1.2 cascade and will facilitate the development of therapies for catecholamine-induced cardiac pathologies.
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5
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Sarkar P, Mozumder S, Bej A, Mukherjee S, Sengupta J, Chattopadhyay A. Structure, dynamics and lipid interactions of serotonin receptors: excitements and challenges. Biophys Rev 2020; 13:10.1007/s12551-020-00772-8. [PMID: 33188638 PMCID: PMC7930197 DOI: 10.1007/s12551-020-00772-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2020] [Accepted: 11/05/2020] [Indexed: 12/13/2022] Open
Abstract
Serotonin (5-hydroxytryptamine, 5-HT) is an intrinsically fluorescent neurotransmitter found in organisms spanning a wide evolutionary range. Serotonin exerts its diverse actions by binding to distinct cell membrane receptors which are classified into many groups. Serotonin receptors are involved in regulating a diverse array of physiological signaling pathways and belong to the family of either G protein-coupled receptors (GPCRs) or ligand-gated ion channels. Serotonergic signaling appears to play a key role in the generation and modulation of various cognitive and behavioral functions such as sleep, mood, pain, anxiety, depression, aggression, and learning. Serotonin receptors act as drug targets for a number of diseases, particularly neuropsychiatric disorders. The signaling mechanism and efficiency of serotonin receptors depend on their amazing ability to rapidly access multiple conformational states. This conformational plasticity, necessary for the wide variety of functions displayed by serotonin receptors, is regulated by binding to various ligands. In this review, we provide a succinct overview of recent developments in generating and analyzing high-resolution structures of serotonin receptors obtained using crystallography and cryo-electron microscopy. Capturing structures of distinct conformational states is crucial for understanding the mechanism of action of these receptors, which could provide important insight for rational drug design targeting serotonin receptors. We further provide emerging information and insight from studies on interactions of membrane lipids (such as cholesterol) with serotonin receptors. We envision that a judicious combination of analysis of high-resolution structures and receptor-lipid interaction would allow a comprehensive understanding of GPCR structure, function and dynamics, thereby leading to efficient drug discovery.
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Affiliation(s)
- Parijat Sarkar
- CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500 007, India
| | - Sukanya Mozumder
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Kolkata, 700 032, India
- Academy of Scientific and Innovative Research, Ghaziabad, 201 002, India
| | - Aritra Bej
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Kolkata, 700 032, India
| | - Sujoy Mukherjee
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Kolkata, 700 032, India
| | - Jayati Sengupta
- Structural Biology and Bioinformatics Division, CSIR-Indian Institute of Chemical Biology, 4, Raja S.C. Mullick Road, Kolkata, 700 032, India
- Academy of Scientific and Innovative Research, Ghaziabad, 201 002, India
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6
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A Systematic Review of Inverse Agonism at Adrenoceptor Subtypes. Cells 2020; 9:cells9091923. [PMID: 32825009 PMCID: PMC7564766 DOI: 10.3390/cells9091923] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Revised: 08/16/2020] [Accepted: 08/18/2020] [Indexed: 12/18/2022] Open
Abstract
As many, if not most, ligands at G protein-coupled receptor antagonists are inverse agonists, we systematically reviewed inverse agonism at the nine adrenoceptor subtypes. Except for β3-adrenoceptors, inverse agonism has been reported for each of the adrenoceptor subtypes, most often for β2-adrenoceptors, including endogenously expressed receptors in human tissues. As with other receptors, the detection and degree of inverse agonism depend on the cells and tissues under investigation, i.e., they are greatest when the model has a high intrinsic tone/constitutive activity for the response being studied. Accordingly, they may differ between parts of a tissue, for instance, atria vs. ventricles of the heart, and within a cell type, between cellular responses. The basal tone of endogenously expressed receptors is often low, leading to less consistent detection and a lesser extent of observed inverse agonism. Extent inverse agonism depends on specific molecular properties of a compound, but inverse agonism appears to be more common in certain chemical classes. While inverse agonism is a fascinating facet in attempts to mechanistically understand observed drug effects, we are skeptical whether an a priori definition of the extent of inverse agonism in the target product profile of a developmental candidate is a meaningful option in drug discovery and development.
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7
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Nakashima N, Nakashima K, Nakashima A, Takano M. Olfactory marker protein elevates basal cAMP concentration. Biochem Biophys Res Commun 2020; 531:203-208. [PMID: 32792198 DOI: 10.1016/j.bbrc.2020.07.087] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2020] [Revised: 07/08/2020] [Accepted: 07/19/2020] [Indexed: 01/25/2023]
Abstract
Olfactory marker protein (OMP), which is expressed abundantly in mature olfactory receptor neurons, operates as a cAMP-binding protein. OMP captures phasic cAMP surges induced by sensory stimuli and punctuates the downstream signalling in the cilia. On the other hand, OMP is also abundant in the soma. At equilibrium, OMP should exhibit association/dissociation reactions with cAMP. To examine the steady-state function of OMP, we expressed OMP in an HEK293 heterologous expression system and measured the activity of cAMP-dependent protein kinase (PKA) using a cAMP response element/luciferase reporter assay. In the presence of OMP, the basal activity level of PKA was elevated to approximately twice as much as that in the absence of OMP. Upon tonic stimulation by membrane-permeable cAMP, the PKA activity increased in a dose-dependent manner and was greater in the presence of OMP at all doses until saturation. These results indicate that OMP, a cytosolic cAMP-binding protein, operates as a cAMP reservoir by increases the basal cAMP concentration and enhances tonic cAMP actions. Together with the previous finding that OMP acutely sequesters cAMP-related responses, these results indicate that OMP can buffer acute surges in cAMP and tonic production, which stabilizes the basal cAMP pool in the long run.
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Affiliation(s)
- Noriyuki Nakashima
- Department of Physiology, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka, 830-0011, Japan.
| | - Kie Nakashima
- Laboratory of Developmental Neurobiology, Graduate School of Biostudies, Kyoto University, Yoshida Hon-machi, Kyoto, 606-8501, Japan
| | - Akiko Nakashima
- Department of Physiology, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka, 830-0011, Japan
| | - Makoto Takano
- Department of Physiology, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka, 830-0011, Japan
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8
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Jiang W, Hu X, Li F, Li G, Wang Y. Adrenoceptor Responses in Human Embryonic Stem Cell-Derived Cardiomyocytes: a Special Focus on Electrophysiological Property. J Pharmacol Exp Ther 2020; 373:429-437. [PMID: 32217769 DOI: 10.1124/jpet.120.265686] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2020] [Accepted: 03/19/2020] [Indexed: 01/16/2023] Open
Abstract
Human embryonic stem cell-derived cardiomyocytes (hESC-CMs) have become a promising cell source for cardiovascular research. The electrophysiological characteristic of hESC-CMs has been generally studied, but little is known about electrophysiological response to adrenergic receptor (AR) activation. This study aims to characterize electrophysiological response of hESC-CMs to adrenergic stimulation in terms of the conduction velocity (CV) and action potential (AP) shape. The H9 hESC-CMs were acquired by a classic differentiation protocol and cultured to achieve confluent cell monolayers. The AP shape and CV among the monolayers were recorded using optical mapping during electrophysiological and pharmacological stimulation experiments. Quantitative real-time polymerase chain reaction and Western blot were adopted to determine the expression levels of Connexin and ion channel gene and protein. Chronic β-AR stimulation by isoproterenol for 24 hours in hESC-CM monolayers increased CV by approximately 50%, whereas α-AR or acute β-AR stimulation had no significant effect; chronic β-AR stimulation resulted in a significant Connexin (Cx) 43 and Nav1.5 upregulation at both protein and mRNA level. Isoproterenol-induced CV accelerating and Cx43 and Nav1.5 upregulation in hESC-CMs, which was attenuated by selective β1-adrenoceptor antagonist CGP 20712A but not selective β2-antagonist ICI 118551. Moreover, pretreatment with protein kinase A (PKA) inhibitor H89, mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (MEK) inhibitor SB203580, and MAPK inhibitor PD98059 suppressed the isoproterenol-induced CV accelerating and Cx43 upregulation, whereas it had no significant effect on Nav1.5 upregulation. The AP shape in hESC-CM monolayers was less susceptible by either β-AR or α-AR stimulation. It was β1-AR not β2-AR contributing to the modification of conduction velocity among hESC-CM monolayers. Chronic β1-AR stimulation accelerates CV by upregulating Cx43 via PKA/MEK/MAPK pathway. SIGNIFICANCE STATEMENT: These data provide new insight into the electrophysiological characteristics of human embryonic stem cell-derived cardiomyocytes (hESC-CMs) and depict a concise signaling pathway in the adrenergic receptor (AR) regulation of action potential shape and electrical propagation across hESC-CM monolayer. It is β1-AR not β2-AR contributing to the modification of conduction velocity in hESC-CMs and accelerating conduction velocity by upregulating Connexin 43 via protein kinase A/ mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase/MAPK pathway.
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Affiliation(s)
- Weiwei Jiang
- Departments of Cardiovascular Surgery (X.H., F.L., G.L., Y.W.) and Gastroenterology (W.J.), Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, Maryland (Y.W.)
| | - Xingjian Hu
- Departments of Cardiovascular Surgery (X.H., F.L., G.L., Y.W.) and Gastroenterology (W.J.), Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, Maryland (Y.W.)
| | - Fei Li
- Departments of Cardiovascular Surgery (X.H., F.L., G.L., Y.W.) and Gastroenterology (W.J.), Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, Maryland (Y.W.)
| | - Geng Li
- Departments of Cardiovascular Surgery (X.H., F.L., G.L., Y.W.) and Gastroenterology (W.J.), Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, Maryland (Y.W.)
| | - Yin Wang
- Departments of Cardiovascular Surgery (X.H., F.L., G.L., Y.W.) and Gastroenterology (W.J.), Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and Department of Biomedical Engineering, The Johns Hopkins University, Baltimore, Maryland (Y.W.)
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9
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Pal S, Chattopadhyay A. Extramembranous Regions in G Protein-Coupled Receptors: Cinderella in Receptor Biology? J Membr Biol 2019; 252:483-497. [DOI: 10.1007/s00232-019-00092-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Accepted: 08/20/2019] [Indexed: 12/22/2022]
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10
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Díaz Ó, Dalton JAR, Giraldo J. Revealing the Mechanism of Agonist-Mediated Cannabinoid Receptor 1 (CB1) Activation and Phospholipid-Mediated Allosteric Modulation. J Med Chem 2019; 62:5638-5654. [DOI: 10.1021/acs.jmedchem.9b00612] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Óscar Díaz
- Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM, 08193 Bellaterra, Spain
| | - James A. R. Dalton
- Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM, 08193 Bellaterra, Spain
| | - Jesús Giraldo
- Instituto de Salud Carlos III, Centro de Investigación Biomédica en Red de Salud Mental, CIBERSAM, 08193 Bellaterra, Spain
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11
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Sogunmez N, Akten ED. Intrinsic Dynamics and Causality in Correlated Motions Unraveled in Two Distinct Inactive States of Human β 2-Adrenergic Receptor. J Phys Chem B 2019; 123:3630-3642. [PMID: 30946584 DOI: 10.1021/acs.jpcb.9b01202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The alternative inactive state of the human β2-adrenergic receptor originally exposed in molecular dynamics simulations was investigated using various analysis tools to evaluate causality between correlated residue-pair fluctuations and suggest allosteric communication pathways. A major conformational shift observed in the third intracellular loop (ICL3) displayed a novel inactive state, featuring an inaccessible G protein binding site blocked by ICL3 and an expanded orthosteric ligand binding site. Residue-based mean-square fluctuation and stiffness calculations revealed a significant mobility decrease in ICL3, which induced a mobility increase in the remaining loop regions. This indicates conformational entropy loss in one mobile region being compensated by residual intermolecular motions in other mobile regions. Moreover, the extent of significantly correlated motions decreased, and correlations that once existed between transmembrane helices shifted toward regions with increased mobility. Conditional time-delayed cross-correlation analysis identified distinct driver-follower relationship profiles. Prior to its packing, freely moving ICL3 was markedly driven by transmembrane helix-8 whereas once packed, ICL3 controlled future fluctuations of nearby helices. Moreover, two transmembrane helices, (H5 and H6), started to control future fluctuations of a remote site, the extracellular loop, ECL2. This clearly suggests that allosteric coupling between extra- and intracellular parts intensified, in agreement with the receptor's well recognized feature, which is the inverse proportionality between activity and the degree of coupling.
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12
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Wold EA, Chen J, Cunningham KA, Zhou J. Allosteric Modulation of Class A GPCRs: Targets, Agents, and Emerging Concepts. J Med Chem 2019; 62:88-127. [PMID: 30106578 PMCID: PMC6556150 DOI: 10.1021/acs.jmedchem.8b00875] [Citation(s) in RCA: 90] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
G-protein-coupled receptors (GPCRs) have been tractable drug targets for decades with over one-third of currently marketed drugs targeting GPCRs. Of these, the class A GPCR superfamily is highly represented, and continued drug discovery for this family of receptors may provide novel therapeutics for a vast range of diseases. GPCR allosteric modulation is an innovative targeting approach that broadens the available small molecule toolbox and is proving to be a viable drug discovery strategy, as evidenced by recent FDA approvals and clinical trials. Numerous class A GPCR allosteric modulators have been discovered recently, and emerging trends such as the availability of GPCR crystal structures, diverse functional assays, and structure-based computational approaches are improving optimization and development. This Perspective provides an update on allosterically targeted class A GPCRs and their disease indications and the medicinal chemistry approaches toward novel allosteric modulators and highlights emerging trends and opportunities in the field.
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Affiliation(s)
- Eric A. Wold
- Department of Pharmacology and Toxicology, Chemical Biology Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Jianping Chen
- Department of Pharmacology and Toxicology, Chemical Biology Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Kathryn A. Cunningham
- Department of Pharmacology and Toxicology, Chemical Biology Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas 77555, United States
| | - Jia Zhou
- Department of Pharmacology and Toxicology, Chemical Biology Program, University of Texas Medical Branch, Galveston, Texas 77555, United States
- Department of Pharmacology and Toxicology, Center for Addiction Research, University of Texas Medical Branch, Galveston, Texas 77555, United States
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13
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Constrained dynamics of the sole tryptophan in the third intracellular loop of the serotonin 1A receptor. Biophys Chem 2018; 240:34-41. [PMID: 29885563 DOI: 10.1016/j.bpc.2018.05.008] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2018] [Revised: 05/24/2018] [Accepted: 05/27/2018] [Indexed: 12/19/2022]
Abstract
G protein-coupled receptors (GPCRs) are major signaling proteins in eukaryotic cells and are important drug targets. In spite of their role in GPCR function, the extramembranous regions of GPCRs are relatively less appreciated. The third intracellular loop (ICL3), which connects transmembrane helices V and VI, is important in this context since its crucial role in signaling has been documented for a number of GPCRs. Unfortunately, the structure of this loop is generally not visualized in x-ray crystallographic studies since this flexible loop is either stabilized using a monoclonal antibody or replaced with lysozyme. In this work, we expressed and purified the ICL3 region of the serotonin1A receptor and monitored its motional restriction and organization utilizing red edge excitation shift (REES) of its sole tryptophan and circular dichroism (CD) spectroscopy. Our results show that the tryptophan in ICL3 exhibits REES of 4 nm, implying that it is localized in a restricted microenvironment. These results are further supported by wavelength-selective changes in fluorescence anisotropy and lifetime. This constrained dynamics was relaxed upon denaturation of the peptide, thereby suggesting the involvement of the peptide secondary structure in the observed motional restriction, as evident from CD spectroscopy and apparent rotational correlation time. To the best of our knowledge, these results constitute one of the first measurements of motional constraint in the ICL3 region of GPCRs. Our results are relevant in the context of the reported intrinsically disordered nature of ICL3 and its role in providing functional diversity to GPCRs due to conformational plasticity.
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14
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Structural insights into positive and negative allosteric regulation of a G protein-coupled receptor through protein-lipid interactions. Sci Rep 2018. [PMID: 29535353 PMCID: PMC5849739 DOI: 10.1038/s41598-018-22735-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Lipids are becoming known as essential allosteric modulators of G protein-coupled receptor (GPCRs). However, how they exert their effects on GPCR conformation at the atomic level is still unclear. In light of recent experimental data, we have performed several long-timescale molecular dynamics (MD) simulations, totalling 24 μs, to rigorously map allosteric modulation and conformational changes in the β2 adrenergic receptor (β2AR) that occur as a result of interactions with three different phospholipids. In particular, we identify different sequential mechanisms behind receptor activation and deactivation, respectively, mediated by specific lipid interactions with key receptor regions. We show that net negatively charged lipids stabilize an active-like state of β2AR that is able to dock Gsα protein. Clustering of anionic lipids around the receptor with local distortion of membrane thickness is also apparent. On the other hand, net-neutral zwitterionic lipids inactivate the receptor, generating either fully inactive or intermediate states, with kinetics depending on lipid headgroup charge distribution and hydrophobicity. These chemical differences alter membrane thickness and density, which differentially destabilize the β2AR active state through lateral compression effects.
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15
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Nakashima N, Nakashima K, Nakayama T, Takaku A, Kanamori R. Dual expression of constitutively active Gα s-protein-coupled receptors differentially establishes the resting activity of the cAMP-gated HCN2 channel in a single compartment. Biochem Biophys Res Commun 2017; 494:76-81. [PMID: 29054409 DOI: 10.1016/j.bbrc.2017.10.082] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 10/16/2017] [Indexed: 11/24/2022]
Abstract
The hyperpolarization-activated cyclic nucleotide-gated 2 (HCN2) channel is a major subtype of the HCN channel family expressed in the nervous system that sets the membrane potential, regulates cell excitability and senses changes in the extracellular environment. Neurons express various Gαs-protein-coupled receptors (GPCRs), many of which show ligand-independent constitutive activity. These membrane-bound proteins are expressed in various subcellular compartments of neurons. Therefore, some proportion of HCN2 channels opens in response to the basal cAMP pool size produced by constitutively active GPCRs. Here, we employed an exogenous HEK293 expression system and voltage-clamp patch-clamp recordings to investigate basal HCN2 channel activity in the presence of two GPCRs with diverse basal activities in a single compartment. We utilized the β2-adrenoceptor (β2AR) together with odorant receptors (ORs), as both GPCR families are known to show strong basal activity. Consequently, β2AR alone strongly enhanced the activity of HCN2 channels, and co-expression of ORs further diversified the HCN2 channel activity, which was totally abolished by an adenylate cyclase inhibitor. Thus, we conclude that the dual expression of constitutively active GPCRs establishes the diverse range of the basal cAMP pool size in resting cells through mutual additive or suppressive interactions, even in the absence of external stimulation.
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Affiliation(s)
- Noriyuki Nakashima
- Division of Integrated Autonomic Function, Department of Physiology, School of Medicine, Kurume University, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan; Department of Physiology and Neurobiology, Faculty of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501, Japan.
| | - Kie Nakashima
- Department of Physiology and Neurobiology, Faculty of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501, Japan; Laboratory of Developmental Neurobiology, Graduate School of Biostudies, Kyoto University, Yoshida Hon-machi, Kyoto 606-8501, Japan
| | - Takeo Nakayama
- Department of Physiology and Neurobiology, Faculty of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501, Japan
| | - Akiko Takaku
- Department of Physiology and Neurobiology, Faculty of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501, Japan; Medical Scientist Training Program, Faculty of Medical Sciences, University of Fukui, 23-3 Matsuokashimoaizuki, Eiheiji-cho, Yoshida-gun, Fukui 910-1193, Japan
| | - Ryosuke Kanamori
- Department of Physiology and Neurobiology, Faculty of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501, Japan
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16
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Stewart MJ, Harding BI, Adamson KJ, Wang T, Storey KB, Cummins SF. Characterisation of two conopressin precursor isoforms in the land snail, Theba pisana. Peptides 2016; 80:32-39. [PMID: 26752717 DOI: 10.1016/j.peptides.2015.12.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Revised: 11/22/2015] [Accepted: 12/28/2015] [Indexed: 12/15/2022]
Abstract
Increased understanding of the molecular components involved in mollusc reproduction may assist in understanding the evolutionary adaptations used by animals, including hermaphrodites, to produce offspring. The neuropeptide conopressin, a member of the vasopressin/oxytocin-like peptide family, can modulate various reproductive activities in invertebrates. In this study, we used the hermaphroditic land snail, Theba pisana, to investigate the presence and tissue-specific distribution of a conopressin gene. Our transcriptomic analysis of T. pisana CNS sheath tissue has revealed two conopressin gene transcripts (Tpi-conopressin-1 and Tpi-conopressin-2), each encoding for precursors containing an identical conopressin nonapeptide and a variable neurophysin. T. pisana conopressins share high identity with other land snails and slugs, as well as other mollusc and vertebrate vasopressin/oxytocin, supported by phylogenetic analysis. Conserved residues in the T. pisana neurophysin are important for peptide binding, and we present molecular dynamic models demonstrating the most likely stable structure of the Tpi-conopressin-1 peptide when associated with neurophysin. RT-PCR shows that Tpi-conopressin-1 is additionally expressed in reproductive tissues, including the dart sac, where abundant spatial expression throughout the sac region is found; this implies a role in 'love' dart synthesis or dart injection during mating. The presence of a conopressin receptor in the CNS sheath indicates CNS neural excitation. In summary, this study represents a detailed molecular analysis of conopressin in a land snail.
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Affiliation(s)
- M J Stewart
- Genecology Research Centre, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia
| | - B I Harding
- Genecology Research Centre, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia
| | - K J Adamson
- Genecology Research Centre, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia
| | - T Wang
- Genecology Research Centre, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia
| | - K B Storey
- Institute of Biochemistry & Department of Biology, Carleton University, 1125 Colonel By Drive, Ottawa, ON K1 S 5B6, Canada
| | - S F Cummins
- Genecology Research Centre, Faculty of Science, Health, Education and Engineering, University of the Sunshine Coast, Maroochydore DC, Queensland 4558, Australia.
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Merz C, Saller S, Kunz L, Xu J, Yeoman RR, Ting AY, Lawson MS, Stouffer RL, Hennebold JD, Pau F, Dissen GA, Ojeda SR, Zelinski MB, Mayerhofer A. Expression of the beta-2 adrenergic receptor (ADRB-2) in human and monkey ovarian follicles: a marker of growing follicles? J Ovarian Res 2015; 8:8. [PMID: 25824473 PMCID: PMC4356150 DOI: 10.1186/s13048-015-0136-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Accepted: 02/23/2015] [Indexed: 12/03/2022] Open
Abstract
Background ADRB-2 was implicated in rodent ovarian functions, including initial follicular growth. In contrast, ADRB-2 expression and function in nonhuman primate and human ovary were not fully known but innervation and significant levels of norepinephrine (NE), which is a ligand at the ADRB-2, were reported in the ovary. Methods We studied expression of ADRB-2 in human and rhesus monkey ovary (RT-PCR, immunohistochemistry; laser micro dissection) and measured levels of norepinephrine (NE; ELISA) in monkey follicular fluid (FF). 3D cultures of monkey follicles (4 animals) were exposed to NE or the ADRB-2 agonist isoproterenol (ISO), and follicular development (size) was monitored. Upon termination expression of ADRB-2, FSH receptor and aromatase genes were examined. Results Immunohistochemistry and RT-PCR of either human follicular granulosa cells (GCs) obtained by laser micro dissection or isolated monkey follicles revealed ADRB-2 in GCs of primordial, primary, secondary and tertiary follicles. Staining of GCs in primordial and primary follicles was intense. In large preantral and antral follicles the staining was heterogeneous, with positive and negative GCs present but GCs lining the antrum of large follicles were generally strongly immunopositive. Theca, interstitial, and ovarian surface epithelial cells were also positive. NE was detected in FF of preovulatory antral monkey follicles (0.37 + 0.05 ng/ml; n = 7; ELISA) but not in serum. We examined preantral follicles ranging from 152 to 366 μm in diameter in a 3D culture in media supplemented with follicle stimulating hormone (FSH). Under these conditions, neither NE, nor ISO, influenced growth rate in a period lasting up to one month. Upon termination of the cultures, all surviving follicles expressed aromatase and FSH receptors, but only about half of them also co-expressed ADRB-2. The ADRB-2 expression was not correlated with the treatment but was positively correlated with the follicular size at the beginning and at the end of the culture period. Hence, expression of ADRB-2 was found in the largest and fastest-in vitro growing follicles. Conclusions The results imply ADRB-2-mediated actions in the development of primate follicles. Drugs interfering with ADRB-2 are used to treat medical conditions and may have unexplored effects in the human ovary.
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Nakashima N, Ishii TM, Bessho Y, Kageyama R, Ohmori H. Hyperpolarisation-activated cyclic nucleotide-gated channels regulate the spontaneous firing rate of olfactory receptor neurons and affect glomerular formation in mice. J Physiol 2013; 591:1749-69. [PMID: 23318872 DOI: 10.1113/jphysiol.2012.247361] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Olfactory receptor neurons (ORNs), which undergo lifelong neurogenesis, have been studied extensively to understand how neurons form precise topographical networks. Neural projections from ORNs are principally guided by the genetic code, which directs projections from ORNs that express a specific odorant receptor to the corresponding glomerulus in the olfactory bulb. In addition, ORNs utilise spontaneous firing activity to establish and maintain the neural map. However, neither the process of generating this spontaneous activity nor its role as a guidance cue in the olfactory bulb is clearly understood. Utilising extracellular unit-recordings in mouse olfactory epithelium slices, we demonstrated that the hyperpolarisation-activated cyclic nucleotide-gated (HCN) channels in the somas of ORNs depolarise their membranes and boost their spontaneous firing rates by sensing basal cAMP levels; the odorant-sensitive cyclic nucleotide-gated (CNG) channels in cilia do not. The basal cAMP levels were maintained via the standing activation of β-adrenergic receptors. Using a Tet-off system to over-express HCN4 channels resulted in the enhancement of spontaneous ORN activity and dramatically reduced both the size and number of glomeruli in the olfactory bulb. This phenotype was rescued by the administration of doxycycline. These findings suggest that cAMP plays different roles in cilia and soma and that basal cAMP levels in the soma are directly converted via HCN channels into a spontaneous firing frequency that acts as an intrinsic guidance cue for the formation of olfactory networks.
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Affiliation(s)
- Noriyuki Nakashima
- Department of Physiology, Faculty of Medicine, Kyoto University, Yoshida-Konoe, Sakyo-ku, Kyoto 606-8501, Japan.
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19
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Jiang X, Xu C, Wang Y, Gao L, Yan C, Li D, Sun H. β2-adrenoceptor transfection enhances contractile reserve of isolated rat ventricular myocytes exposed to chronic isoprenaline stimulation by improving β1-adrenoceptor responsiveness. J Recept Signal Transduct Res 2012; 32:36-41. [PMID: 22216755 DOI: 10.3109/10799893.2011.610107] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
CONTEXT Heart failure (HF) is a progressive deterioration in heart function associated with overactivity of the sympathetic nervous system. Elevated sympathetic nervous system activity down regulates the β-adrenergic signal system, suppressing β-adrenoceptors (β-ARs)-mediated contractile support in the failing heart. OBJECTIVE We investigated the effects of β(2)-AR gene transfer on shortening amplitude of isolated ventricular myocytes under chronic exposure to isoprenaline (ISO), and further determine the contributions of β(1)-AR and β(2)-AR to the contraction. MATERIALS AND METHODS Cardiomyocytes were isolated from adult rat hearts and then transfected with β(2)-AR gene using an adenovirus vector. Four hours after the infection, cardiomyocytes were treated with ISO for another 24 hours to imitate high levels of circulating catecholamines in HF. Western blotting was performed to measure myocardial protein expression of β(2)-AR. Video-based edge-detection system was used to evaluate basal and ISO-stimulated shortening amplitudes of cardiomyocytes. RESULTS β(2)-AR gene transfer increased β(2)-AR protein content. Chronic ISO stimulation produced a negative inotropic response, whereas acute ISO stimulation showed a positive inotropic response. β(2)-AR gene transfer had no significant effects on shortening amplitude of cardiomyocytes under normal conditions, but enhanced the blunted contraction of cardiomyocytes under pathological conditions induced by chronic ISO stimulation, and the effect was inhibited by β(1)-AR antagonist, CGP 20712A, instead of β(2)-AR antagonist, ICI 118,551. DISCUSSION AND CONCLUSIONS We conclude that β(2)-AR gene transfer in isolated ventricular myocytes under chronic ISO stimulation improves cellular contraction, and the beneficial effects might be mediated by improving β(1)-adrenoceptor responsiveness.
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Affiliation(s)
- XinWei Jiang
- Department of Physiology, Xuzhou Medical College, Xuzhou, China
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20
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Carrel D, Simon A, Emerit MB, Rivals I, Leterrier C, Biard M, Hamon M, Darmon M, Lenkei Z. Axonal Targeting of the 5-HT1B Serotonin Receptor Relies on Structure-Specific Constitutive Activation. Traffic 2011; 12:1501-20. [DOI: 10.1111/j.1600-0854.2011.01260.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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21
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Yan L, Jia Z, Cui J, Yang H, Yang H, Zhang Y, Zhou C. Beta-adrenergic signals regulate cardiac differentiation of mouse embryonic stem cells via mitogen-activated protein kinase pathways. Dev Growth Differ 2011; 53:772-9. [PMID: 21711454 DOI: 10.1111/j.1440-169x.2011.01284.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
As embryonic stem cell-derived cardiomyocytes (ESC-CMs) have the potential to be used in cell replacement therapy, an understanding of the signaling mechanisms that regulate their terminal differentiation is imperative. In previous studies, we discovered the presence of adrenergic and muscarinic receptors in mouse embryonic stem cells (ESCs). However, little is known about the role of these receptors in cardiac differentiation and development, which is critically important in cardiac physiology and pharmacology. Here, we demonstrated that a β-adrenergic receptor (β-AR) agonist significantly enhanced cardiac differentiation as indicated by a higher percentage of beating embryoid bodies and a higher expression level of cardiac markers. Application of β1-AR and β2-AR antagonists partly abolished the effect of the β-AR agonist. In addition, by administering selective inhibitors we found that the effect of β-AR was driven via p38 mitogen-activated protein kinase and extracellular-signal regulated kinase pathway. These findings suggest that ESCs are also a target for β-adrenergic regulation and β-adrenergic signaling plays a role in ESC cardiac differentiation.
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Affiliation(s)
- Lihui Yan
- Department of Cardiology, Peking University Third Hospital, Haidian District, Beijing, China
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22
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Xiao K, Shenoy SK. Beta2-adrenergic receptor lysosomal trafficking is regulated by ubiquitination of lysyl residues in two distinct receptor domains. J Biol Chem 2011; 286:12785-95. [PMID: 21330366 DOI: 10.1074/jbc.m110.203091] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Agonist stimulation of the β2-adrenergic receptors (β2ARs) leads to their ubiquitination and lysosomal degradation. Inhibition of lysosomal proteases results in the stabilization and retention of internalized full-length β2ARs in the lysosomes, whereas inhibition of proteasomal proteases stabilizes newly synthesized β2ARs in nonlysosomal compartments. Additionally, a lysine-less β2AR (0K-β2AR) that is deficient in ubiquitination and degradation is not sorted to lysosomes unlike the WT β2AR, which is sorted to lysosomes. Thus, lysosomes are the primary sites for the degradation of agonist-activated, ubiquitinated β2ARs. To identify the specific site(s) of ubiquitination required for lysosomal sorting of the β2AR, four mutants, with lysines only in one intracellular domain, namely, loop 1, loop 2, loop 3, and carboxyl tail were generated. All of these receptor mutants coupled to G proteins, recruited β-arrestin2, and internalized just as the WT β2AR. However, only loop 3 and carboxyl tail β2ARs with lysines in the third intracellular loop or in the carboxyl tail were ubiquitinated and sorted for lysosomal degradation. As a complementary approach, we performed MS-based proteomic analyses to directly identify ubiquitination sites within the β2AR. We overexpressed and purified the β2AR from HEK-293 cells with or without prior agonist exposure and subjected trypsin-cleaved β2AR to LC-MS/MS analyses. We identified ubiquitinated lysines in the third intracellular loop (Lys-263 and Lys-270) and in the carboxyl tail (Lys-348, Lys-372, and Lys-375) of the β2AR. These findings introduce a new concept that two distinct domains in the β2AR are involved in ubiquitination and lysosomal degradation, contrary to the generalization that such regulatory mechanisms occur mainly at the carboxyl tails of GPCRs and other transmembrane receptors.
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Affiliation(s)
- Kunhong Xiao
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710, USA.
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23
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Tao YX. Constitutive activation of G protein-coupled receptors and diseases: insights into mechanisms of activation and therapeutics. Pharmacol Ther 2008; 120:129-48. [PMID: 18768149 DOI: 10.1016/j.pharmthera.2008.07.005] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Accepted: 07/22/2008] [Indexed: 01/17/2023]
Abstract
The existence of constitutive activity for G protein-coupled receptors (GPCRs) was first described in 1980s. In 1991, the first naturally occurring constitutively active mutations in GPCRs that cause diseases were reported in rhodopsin. Since then, numerous constitutively active mutations that cause human diseases were reported in several additional receptors. More recently, loss of constitutive activity was postulated to also cause diseases. Animal models expressing some of these mutants confirmed the roles of these mutations in the pathogenesis of the diseases. Detailed functional studies of these naturally occurring mutations, combined with homology modeling using rhodopsin crystal structure as the template, lead to important insights into the mechanism of activation in the absence of crystal structure of GPCRs in active state. Search for inverse agonists on these receptors will be critical for correcting the diseases cause by activating mutations in GPCRs. Theoretically, these inverse agonists are better therapeutics than neutral antagonists in treating genetic diseases caused by constitutively activating mutations in GPCRs.
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Affiliation(s)
- Ya-Xiong Tao
- Department of Anatomy, Physiology and Pharmacology, 212 Greene Hall, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, USA.
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Bongers G, Krueger KM, Miller TR, Baranowski JL, Estvander BR, Witte DG, Strakhova MI, van Meer P, Bakker RA, Cowart MD, Hancock AA, Esbenshade TA, Leurs R. An 80-amino acid deletion in the third intracellular loop of a naturally occurring human histamine H3 isoform confers pharmacological differences and constitutive activity. J Pharmacol Exp Ther 2007; 323:888-98. [PMID: 17855474 DOI: 10.1124/jpet.107.127639] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In this article, we pharmacologically characterized two naturally occurring human histamine H3 receptor (hH3R) isoforms, hH3R(445) and hH3R(365). These abundantly expressed splice variants differ by a deletion of 80 amino acids in the intracellular loop 3. In this report, we show that the hH3R(365) is differentially expressed compared with the hH3R(445) and has a higher affinity and potency for H3R agonists and conversely a lower potency and affinity for H3R inverse agonists. Furthermore, we show a higher constitutive signaling of the hH3R(365) compared with the hH3R(445) in both guanosine-5'-O-(3-[35S]thio) triphosphate binding and cAMP assays, likely explaining the observed differences in hH3R pharmacology of the two isoforms. Because H3R ligands are beneficial in animal models of obesity, epilepsy, and cognitive diseases such as Alzheimer's disease and attention deficit hyperactivity disorder and currently entered clinical trails, these differences in H3R pharmacology of these two isoforms are of great importance for a detailed understanding of the action of H3R ligands.
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Affiliation(s)
- Gerold Bongers
- Leiden/Amsterdam Center for Drug Research, Department of Medicinal Chemistry, Vrije Universiteit Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands
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25
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Kinzer-Ursem TL, Linderman JJ. Both ligand- and cell-specific parameters control ligand agonism in a kinetic model of g protein-coupled receptor signaling. PLoS Comput Biol 2007; 3:e6. [PMID: 17222056 PMCID: PMC1769407 DOI: 10.1371/journal.pcbi.0030006] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2006] [Accepted: 11/30/2006] [Indexed: 12/17/2022] Open
Abstract
G protein–coupled receptors (GPCRs) exist in multiple dynamic states (e.g., ligand-bound, inactive, G protein–coupled) that influence G protein activation and ultimately response generation. In quantitative models of GPCR signaling that incorporate these varied states, parameter values are often uncharacterized or varied over large ranges, making identification of important parameters and signaling outcomes difficult to intuit. Here we identify the ligand- and cell-specific parameters that are important determinants of cell-response behavior in a dynamic model of GPCR signaling using parameter variation and sensitivity analysis. The character of response (i.e., positive/neutral/inverse agonism) is, not surprisingly, significantly influenced by a ligand's ability to bias the receptor into an active conformation. We also find that several cell-specific parameters, including the ratio of active to inactive receptor species, the rate constant for G protein activation, and expression levels of receptors and G proteins also dramatically influence agonism. Expressing either receptor or G protein in numbers several fold above or below endogenous levels may result in system behavior inconsistent with that measured in endogenous systems. Finally, small variations in cell-specific parameters identified by sensitivity analysis as significant determinants of response behavior are found to change ligand-induced responses from positive to negative, a phenomenon termed protean agonism. Our findings offer an explanation for protean agonism reported in β2--adrenergic and α2A-adrenergic receptor systems. G protein–coupled receptors (GPCRs) are transmembrane proteins involved in physiological functions ranging from vasodilation and immune response to memory. The binding of both endogenous ligands (e.g., hormones, neurotransmitters) and exogenous ligands (e.g., pharmaceuticals) to these receptors initiates intracellular events that ultimately lead to cell responses. We describe a dynamic model for G protein activation, an immediate outcome of GPCR signaling, and use it together with efficient parameter variation and sensitivity analysis techniques to identify the key cell- and ligand-specific parameters that influence G protein activation. Our results show that although ligand-specific parameters do strongly influence cell response (either causing increases or decreases in G protein activation), cellular parameters may also dictate the magnitude and direction of G protein activation. We apply our findings to describe how protean agonism, a phenomenon in which the same ligand may induce both positive and negative responses, may result from changes in cell-specific parameters. These findings may be used to understand the molecular basis of different responses of cell types and tissues to pharmacological treatment. In addition, these methods may be applied generally to models of cellular signaling and will help guide experimental resources toward further characterization of the key parameters in these networks.
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Affiliation(s)
- Tamara L Kinzer-Ursem
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
| | - Jennifer J Linderman
- Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America
- * To whom correspondence should be addressed. E-mail:
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26
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Zhu WZ, Chakir K, Zhang S, Yang D, Lavoie C, Bouvier M, Hébert TE, Lakatta EG, Cheng H, Xiao RP. Heterodimerization of beta1- and beta2-adrenergic receptor subtypes optimizes beta-adrenergic modulation of cardiac contractility. Circ Res 2005; 97:244-51. [PMID: 16002745 DOI: 10.1161/01.res.0000176764.38934.86] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Intermolecular interactions between members of both similar and divergent G protein-coupled receptor subfamilies have been shown in various experimental systems. Here, we demonstrate heterodimerization of predominant beta-adrenergic receptor (betaAR) subtypes expressed in the heart, beta1AR, and beta2AR, and its physiological relevance. In intact adult-mouse cardiac myocytes lacking native beta1AR and beta2AR, coexpression of both betaAR subtypes led to receptor heterodimerization, as evidenced by their coimmunoprecipitation, colocalization at optical resolution, and markedly increased binding affinity for subtype-selective ligands. As a result, the dose-response curve of myocyte contraction to betaAR agonist stimulation with isoproterenol (ISO) was shifted leftward by approximately 1.5 orders of magnitude, and the response of cellular cAMP formation to ISO was enhanced concomitantly, indicating that intermolecular interactions of betaAR subtypes resulted in sensitization of these receptors in response to agonist stimulation. In contrast, the presence of beta1AR greatly suppressed ligand-independent spontaneous activity of coexisting beta2ARs. Thus, heterodimerization of beta1AR and beta2AR in intact cardiac myocytes creates a novel population of betaARs with distinct functional and pharmacological properties, resulting in enhanced signaling efficiency in response to agonist stimulation while silencing ligand-independent receptor activation, thereby optimizing beta-adrenergic modulation of cardiac contractility.
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MESH Headings
- Adrenergic beta-Agonists/pharmacology
- Animals
- Cyclic AMP/physiology
- Dimerization
- Immunoprecipitation
- Ligands
- Male
- Mice
- Mice, Knockout
- Myocardial Contraction/drug effects
- Myocytes, Cardiac/chemistry
- Receptors, Adrenergic, beta-1/analysis
- Receptors, Adrenergic, beta-1/chemistry
- Receptors, Adrenergic, beta-1/physiology
- Receptors, Adrenergic, beta-2/analysis
- Receptors, Adrenergic, beta-2/chemistry
- Receptors, Adrenergic, beta-2/physiology
- Receptors, G-Protein-Coupled/chemistry
- Signal Transduction
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Affiliation(s)
- Wei-Zhong Zhu
- Laboratory of Cardiovascular Science, Gerontology Research Center, National Institute on Aging, NIH, 5600 Nathan Shock Dr, Baltimore, MD 21224, USA
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27
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Wang W, Zhu W, Wang S, Yang D, Crow MT, Xiao RP, Cheng H. Sustained beta1-adrenergic stimulation modulates cardiac contractility by Ca2+/calmodulin kinase signaling pathway. Circ Res 2004; 95:798-806. [PMID: 15375008 DOI: 10.1161/01.res.0000145361.50017.aa] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
A tenet of beta1-adrenergic receptor (beta1AR) signaling is that stimulation of the receptor activates the adenylate cyclase-cAMP-protein kinase A (PKA) pathway, resulting in positive inotropic and relaxant effects in the heart. However, recent studies have suggested the involvement of Ca2+/calmodulin-dependent protein kinase II (CaMKII) in beta1AR-stimulated cardiac apoptosis. In this study, we determined roles of CaMKII and PKA in sustained versus short-term beta1AR modulation of excitation-contraction (E-C) coupling in cardiac myocytes. Short-term (10-minute) and sustained (24-hour) beta1AR stimulation with norepinephrine similarly enhanced cell contraction and Ca2+ transients, in contrast to anticipated receptor desensitization. More importantly, the sustained responses were largely PKA-independent, and were sensitive to specific CaMKII inhibitors or adenoviral expression of a dominant-negative CaMKII mutant. Biochemical assays revealed that a progressive and persistent CaMKII activation was associated with a rapid desensitization of the cAMP/PKA signaling. Concomitantly, phosphorylation of phospholamban, an SR Ca2+ cycling regulatory protein, was shifted from its PKA site (16Ser) to CaMKII site (17Thr). Thus, beta1AR stimulation activates dual signaling pathways mediated by cAMP/PKA and CaMKII, the former undergoing desensitization and the latter exhibiting sensitization. This finding may bear important etiological and therapeutical ramifications in understanding beta1AR signaling in chronic heart failure.
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MESH Headings
- Adrenergic alpha-Agonists/pharmacology
- Animals
- Calcium Signaling/drug effects
- Calcium Signaling/physiology
- Calcium-Binding Proteins/metabolism
- Calcium-Calmodulin-Dependent Protein Kinase Type 2
- Calcium-Calmodulin-Dependent Protein Kinases/antagonists & inhibitors
- Calcium-Calmodulin-Dependent Protein Kinases/genetics
- Calcium-Calmodulin-Dependent Protein Kinases/physiology
- Cell Size/drug effects
- Cells, Cultured/drug effects
- Cells, Cultured/physiology
- Cyclic AMP/physiology
- Cyclic AMP-Dependent Protein Kinases/physiology
- Humans
- Male
- Mutagenesis, Site-Directed
- Myocardial Contraction/drug effects
- Myocardial Contraction/physiology
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/physiology
- Norepinephrine/pharmacology
- Phosphorylation
- Prazosin/pharmacology
- Protein Processing, Post-Translational
- Rats
- Rats, Sprague-Dawley
- Receptors, Adrenergic, beta-1/drug effects
- Receptors, Adrenergic, beta-1/physiology
- Recombinant Fusion Proteins/physiology
- Second Messenger Systems/drug effects
- Second Messenger Systems/physiology
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Affiliation(s)
- Wang Wang
- Laboratory of Cardiovascular Sciences, National Institute on Aging, National Institutes of Health, Baltimore, MD 21224, USA
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28
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Chen KH, Guo X, Ma D, Guo Y, Li Q, Yang D, Li P, Qiu X, Wen S, Xiao RP, Tang J. Dysregulation of HSG triggers vascular proliferative disorders. Nat Cell Biol 2004; 6:872-83. [PMID: 15322553 DOI: 10.1038/ncb1161] [Citation(s) in RCA: 286] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2004] [Accepted: 07/08/2004] [Indexed: 11/09/2022]
Abstract
Vascular proliferative disorders, such as atherosclerosis and restenosis, are the most common causes of severe cardiovascular diseases, but a common molecular mechanism remains elusive. Here, we identify and characterize a novel hyperplasia suppressor gene, named HSG (later re-named rat mitofusin-2). HSG expression was markedly reduced in hyper-proliferative vascular smooth muscle cells (VSMCs) from spontaneously hypertensive rat arteries, balloon-injured Wistar Kyoto rat arteries, or ApoE-knockout mouse atherosclerotic arteries. Overexpression of HSG overtly suppressed serum-evoked VSMC proliferation in culture, and blocked balloon injury induced neointimal VSMC proliferation and restenosis in rat carotid arteries. The HSG anti-proliferative effect was mediated by inhibition of ERK/MAPK signalling and subsequent cell-cycle arrest. Deletion of the p21(ras) signature motif, but not the mitochondrial targeting domain, abolished HSG-induced growth arrest, indicating that rHSG-induced anti-proliferation was independent of mitochondrial fusion. Thus, rHSG functions as a cell proliferation suppressor, whereas dysregulation of rHSG results in proliferative disorders.
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Affiliation(s)
- Kuang-Hueih Chen
- The Institute of Cardiovascular Science & The Institute of Molecular Medicine, Peking University, Beijing 100083, China
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