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Zhou X, Septien-Gonzalez H, Husaini S, Ward RJ, Milligan G, Gradinaru CC. Diffusion and Oligomerization States of the Muscarinic M 1 Receptor in Live Cells─The Impact of Ligands and Membrane Disruptors. J Phys Chem B 2024; 128:4354-4366. [PMID: 38683784 PMCID: PMC11090110 DOI: 10.1021/acs.jpcb.4c01035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2024] [Revised: 03/25/2024] [Accepted: 03/27/2024] [Indexed: 05/02/2024]
Abstract
G protein-coupled receptors (GPCRs) are a major gateway to cellular signaling, which respond to ligands binding at extracellular sites through allosteric conformational changes that modulate their interactions with G proteins and arrestins at intracellular sites. High-resolution structures in different ligand states, together with spectroscopic studies and molecular dynamics simulations, have revealed a rich conformational landscape of GPCRs. However, their supramolecular structure and spatiotemporal distribution is also thought to play a significant role in receptor activation and signaling bias within the native cell membrane environment. Here, we applied single-molecule fluorescence techniques, including single-particle tracking, single-molecule photobleaching, and fluorescence correlation spectroscopy, to characterize the diffusion and oligomerization behavior of the muscarinic M1 receptor (M1R) in live cells. Control samples included the monomeric protein CD86 and fixed cells, and experiments performed in the presence of different orthosteric M1R ligands and of several compounds known to change the fluidity and organization of the lipid bilayer. M1 receptors exhibit Brownian diffusion characterized by three diffusion constants: confined/immobile (∼0.01 μm2/s), slow (∼0.04 μm2/s), and fast (∼0.14 μm2/s), whose populations were found to be modulated by both orthosteric ligands and membrane disruptors. The lipid raft disruptor C6 ceramide led to significant changes for CD86, while the diffusion of M1R remained unchanged, indicating that M1 receptors do not partition in lipid rafts. The extent of receptor oligomerization was found to be promoted by increasing the level of expression and the binding of orthosteric ligands; in particular, the agonist carbachol elicited a large increase in the fraction of M1R oligomers. This study provides new insights into the balance between conformational and environmental factors that define the movement and oligomerization states of GPCRs in live cells under close-to-native conditions.
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Affiliation(s)
- Xiaohan Zhou
- Department
of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
- Department
of Chemical & Physical Sciences, University
of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Horacio Septien-Gonzalez
- Department
of Chemical & Physical Sciences, University
of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Sami Husaini
- Department
of Chemical & Physical Sciences, University
of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
| | - Richard J. Ward
- Centre
for Translational Pharmacology, School of Molecular Biosciences, College
of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
| | - Graeme Milligan
- Centre
for Translational Pharmacology, School of Molecular Biosciences, College
of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, Scotland, U.K.
| | - Claudiu C. Gradinaru
- Department
of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
- Department
of Chemical & Physical Sciences, University
of Toronto Mississauga, Mississauga, Ontario L5L 1C6, Canada
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van der Westhuizen ET, Choy KHC, Valant C, McKenzie-Nickson S, Bradley SJ, Tobin AB, Sexton PM, Christopoulos A. Fine Tuning Muscarinic Acetylcholine Receptor Signaling Through Allostery and Bias. Front Pharmacol 2021; 11:606656. [PMID: 33584282 PMCID: PMC7878563 DOI: 10.3389/fphar.2020.606656] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 11/30/2020] [Indexed: 12/18/2022] Open
Abstract
The M1 and M4 muscarinic acetylcholine receptors (mAChRs) are highly pursued drug targets for neurological diseases, in particular for Alzheimer's disease and schizophrenia. Due to high sequence homology, selective targeting of any of the M1-M5 mAChRs through the endogenous ligand binding site has been notoriously difficult to achieve. With the discovery of highly subtype selective mAChR positive allosteric modulators in the new millennium, selectivity through targeting an allosteric binding site has opened new avenues for drug discovery programs. However, some hurdles remain to be overcome for these promising new drug candidates to progress into the clinic. One challenge is the potential for on-target side effects, such as for the M1 mAChR where over-activation of the receptor by orthosteric or allosteric ligands can be detrimental. Therefore, in addition to receptor subtype selectivity, a drug candidate may need to exhibit a biased signaling profile to avoid such on-target adverse effects. Indeed, recent studies in mice suggest that allosteric modulators for the M1 mAChR that bias signaling toward specific pathways may be therapeutically important. This review brings together details on the signaling pathways activated by the M1 and M4 mAChRs, evidence of biased agonism at these receptors, and highlights pathways that may be important for developing new subtype selective allosteric ligands to achieve therapeutic benefit.
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Affiliation(s)
- Emma T. van der Westhuizen
- Drug Discovery Biology, Monash Institute for Pharmaceutical Research, Monash University, Parkville, VIC, Australia
| | - K. H. Christopher Choy
- Drug Discovery Biology, Monash Institute for Pharmaceutical Research, Monash University, Parkville, VIC, Australia
| | - Celine Valant
- Drug Discovery Biology, Monash Institute for Pharmaceutical Research, Monash University, Parkville, VIC, Australia
| | - Simon McKenzie-Nickson
- Drug Discovery Biology, Monash Institute for Pharmaceutical Research, Monash University, Parkville, VIC, Australia
| | - Sophie J. Bradley
- Centre for Translational Pharmacology, Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Andrew B. Tobin
- Centre for Translational Pharmacology, Institute of Molecular Cell and Systems Biology, University of Glasgow, Glasgow, United Kingdom
| | - Patrick M. Sexton
- Drug Discovery Biology, Monash Institute for Pharmaceutical Research, Monash University, Parkville, VIC, Australia
| | - Arthur Christopoulos
- Drug Discovery Biology, Monash Institute for Pharmaceutical Research, Monash University, Parkville, VIC, Australia
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Adisa R, Omitogun TI. Awareness, knowledge, attitude and practice of adverse drug reaction reporting among health workers and patients in selected primary healthcare centres in Ibadan, southwestern Nigeria. BMC Health Serv Res 2019; 19:926. [PMID: 31796034 PMCID: PMC6889459 DOI: 10.1186/s12913-019-4775-9] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2019] [Accepted: 11/22/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Higher incidence of adverse drug reactions (ADRs) is a global health problem requiring attention of all stakeholders regardless of the practice settings. This study therefore aimed to evaluate awareness, knowledge, attitude and practice of ADR reporting among health workers and patients in 10 primary healthcare centres (PHCs) in Ibadan, southwestern Nigeria. METHODS Questionnaire-guided cross-sectional survey among 80 health workers and 360 patients enrolled from the selected PHCs between October and December 2018. The semi-structured questionnaires generally comprised open-ended and closed-ended questions to explore general knowledge and awareness of ADRs and pharmacovigilance, while other question-items evaluated attitude towards ADR reporting and ADR reporting practice. Overall percent score in the knowledge and attitude domains for the health workers was developed into binary categories of > 80 versus ≤80% for "adequate" and "inadequate" knowledge, as well as "positive" and "negative" attitude, respectively. Data were summarised using descriptive statistics, while Chi-square test was used to evaluate categorical variables at p < 0.05. RESULTS Overall, 58(72.5%) health workers had heard of pharmacovigilance, but only 3(5.2%) correctly understood the pharmacovigilance concept. Twelve (15.0%) showed adequate knowledge of ADRs, while 37(46.2%) demonstrated positive attitude towards ADR reporting. Thirty (37.5%) health workers had come across ADR reporting form, while 79(98.8%) expressed willingness to report all ADRs encountered. Of the patients, 31(8.6%) had heard of pharmacovigilance, 143(39.7%) correctly cited ADR definition, while 67(18.6%) reported the previously experienced ADRs. Informing healthcare professional (38; 38.8%) was the most common measure taken by patients when they experienced reaction(s). Nurses significantly had adequate knowledge of ADRs (p < 0.001) compared to other cadres. CONCLUSIONS Health workers in the selected PHCs were largely aware of pharmacovigilance but show low level of knowledge about ADRs and pharmacovigilance concept, with moderately positive attitude towards ADR reporting. Patients on the other hand demonstrate low level of awareness of pharmacovigilance and ADR reporting, with less than one-fifth who reported the previously experienced ADRs. This perhaps underscores a need for regular mandatory education and training on ADRs/pharmacovigilance concept among the PHC health workers, while continuous public enlightenment and awareness campaign on spontaneous reporting of ADRs is advocated in order to enhance reporting rate.
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Affiliation(s)
- Rasaq Adisa
- Department of Clinical Pharmacy and Pharmacy Administration, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria
| | - Tomilayo I. Omitogun
- Department of Clinical Pharmacy and Pharmacy Administration, Faculty of Pharmacy, University of Ibadan, Ibadan, Nigeria
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Remesic M, Hruby VJ, Porreca F, Lee YS. Recent Advances in the Realm of Allosteric Modulators for Opioid Receptors for Future Therapeutics. ACS Chem Neurosci 2017; 8:1147-1158. [PMID: 28368571 DOI: 10.1021/acschemneuro.7b00090] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Opioids, and more specifically μ-opioid receptor (MOR) agonists such as morphine, have long been clinically used as therapeutics for severe pain states but often come with serious side effects such as addiction and tolerance. Many studies have focused on bringing about analgesia from the MOR with attenuated side effects, but its underlying mechanism is not fully understood. Recently, focus has been geared toward the design and elucidation of the orthosteric site with ligands of various biological profiles and mixed subtype opioid activities and selectivities, but targeting the allosteric site is an area of increasing interest. It has been shown that allosteric modulators play key roles in influencing receptor function such as its tolerance to a ligand and affect downstream pathways. There has been a high variance of chemical structures that provide allosteric modulation at a given receptor, but recent studies and reviews tend to focus on the altered cellular mechanisms instead of providing a more rigorous description of the allosteric ligand's structure-function relationship. In this review, we aim to explore recent developments in the structural motifs that potentiate orthosteric binding and their influences on cellular pathways in an effort to present novel approaches to opioid therapeutic design.
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Affiliation(s)
- Michael Remesic
- Department
of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Victor J. Hruby
- Department
of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
| | - Frank Porreca
- Department
of Pharmacology, University of Arizona, Tucson, Arizona 85719, United States
| | - Yeon Sun Lee
- Department
of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721, United States
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Shamim S, Sharib SM, Malhi SM, Muntaha SU, Raza H, Ata S, Farooq AS, Hussain M. Adverse drug reactions (ADRS) reporting: awareness and reasons of under-reporting among health care professionals, a challenge for pharmacists. SPRINGERPLUS 2016; 5:1778. [PMID: 27795920 PMCID: PMC5061681 DOI: 10.1186/s40064-016-3337-4] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 01/17/2016] [Accepted: 09/21/2016] [Indexed: 11/23/2022]
Abstract
OBJECTIVES To measure awareness about adverse drug reaction (ADRs) reporting among doctors, pharmacists and nurses and to determine reasons of ADRs under-reporting in Pakistan. METHODS In present study, a self-administered questionnaire was used to measure the awareness level about ADRs reporting among health care professionals (HCPs) of Pakistan. This was a cross sectional study. RESULTS Out of the respondents 51 % were physicians, 29.7 % pharmacists and 19.3 % were nurses. 65.5 % of HCP population observed ADRs, out of which only 57.4 % reported these in their respective hospitals. About 77.3 % of population understood the importance of reporting ADRs while 67.3 % of population agrees that pharmacists are chief personnel for the development of system. 71.8 % of HCPs agrees that ADRs are not reported because Community pharmacy lacks legally qualified pharmacists. Only 14.3 % of HCPs population knows that there is any ADR reporting organization in Pakistan. CONCLUSION The study recommends the need of such reporting system and more than half of the studied population agreed that pharmacists are required in developing such system.
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Affiliation(s)
- Sumbul Shamim
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Dow College of Pharmacy, Dow University of Health Sciences, Ojha Campus, Karachi, Pakistan
| | - Syed Muhammad Sharib
- Dow College of Pharmacy, Dow University of Health Sciences, Ojha Campus, Karachi, Pakistan
| | - Saima Mahmood Malhi
- Department of Pharmacology, Faculty of Pharmaceutical Sciences, Dow College of Pharmacy, Dow University of Health Sciences, Ojha Campus, Karachi, Pakistan
| | - Sidrat-Ul Muntaha
- Dow College of Pharmacy, Dow University of Health Sciences, Ojha Campus, Karachi, Pakistan
| | - Hassan Raza
- Dow College of Pharmacy, Dow University of Health Sciences, Ojha Campus, Karachi, Pakistan
| | - Saniya Ata
- Dow College of Pharmacy, Dow University of Health Sciences, Ojha Campus, Karachi, Pakistan
| | - Ali Salman Farooq
- Dow College of Pharmacy, Dow University of Health Sciences, Ojha Campus, Karachi, Pakistan
| | - Mehwish Hussain
- Department of Research, Dow University of Health Sciences, Ojha Campus, Karachi, Pakistan
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The distribution of muscarinic M1 receptors in the human hippocampus. J Chem Neuroanat 2016; 77:187-192. [PMID: 27435807 DOI: 10.1016/j.jchemneu.2016.07.006] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2016] [Revised: 07/13/2016] [Accepted: 07/15/2016] [Indexed: 11/21/2022]
Abstract
The muscarinic M1 receptor plays a significant role in cognition, probably by modulating information processing in key regions such as the hippocampus. To understand how the muscarinic M1 receptor achieves these functions in the hippocampus, it is critical to know the distribution of the receptor within this complex brain region. To date, there are limited data on the distribution of muscarinic M1 receptors in the human hippocampus which may also be confounded because some anti-muscarinic receptor antibodies have been shown to lack specificity. Initially, using Western blotting and immunohistochemistry, we showed the anti-muscarinic M1 receptor antibody to be used in our study bound to a single 62kDa protein that was absent in mice lacking the muscarinic M1 receptor gene. Then, using immunohistochemistry, we determined the distribution of muscarinic M1 receptors in human hippocampus from 10 subjects with no discernible history of a neurological or psychiatric disorder. Our data shows the muscarinic M1 receptor to be predominantly on pyramidal cells in the hippocampus. Muscarinic M1 receptor positive cells were most apparent in the deep polymorphic layer of the dentate gyrus, the pyramidal cell layer of cornu ammonis region 3, the cellular layers of the subiculum, layer II of the presubiculum and layer III and V of the parahippocampal gyrus. Positive cells were less numerous and less intensely stained in the pyramidal layer of cornu ammonis region 2 and were sparse in the molecular layer of the dentate gyrus as well as cornu ammonis region 1. Although immunoreactivity was present in the granular layer of the dentate gyrus, it was difficult to identity individual immunopositive cells, possibly due to the density of cells. This distribution of the muscarinic M1 receptors in human hippocampus, and its localisation on glutamatergic cells, would suggest the receptor has a significant role in modulating excitatory hippocampal neurotransmission.
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Induction of Anti-Hebbian LTP in CA1 Stratum Oriens Interneurons: Interactions between Group I Metabotropic Glutamate Receptors and M1 Muscarinic Receptors. J Neurosci 2016; 35:13542-54. [PMID: 26446209 DOI: 10.1523/jneurosci.0956-15.2015] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
UNLABELLED An anti-Hebbian form of LTP is observed at excitatory synapses made with some hippocampal interneurons. LTP induction is facilitated when postsynaptic interneurons are hyperpolarized, presumably because Ca(2+) entry through Ca(2+)-permeable glutamate receptors is enhanced. The contribution of modulatory transmitters to anti-Hebbian LTP induction remains to be established. Activation of group I metabotropic receptors (mGluRs) is required for anti-Hebbian LTP induction in interneurons with cell bodies in the CA1 stratum oriens. This region receives a strong cholinergic innervation from the septum, and muscarinic acetylcholine receptors (mAChRs) share some signaling pathways and cooperate with mGluRs in the control of neuronal excitability.We therefore examined possible interactions between group I mGluRs and mAChRs in anti-Hebbian LTP at synapses which excite oriens interneurons in rat brain slices. We found that blockade of either group I mGluRs or M1 mAChRs prevented the induction of anti-Hebbian LTP by pairing presynaptic activity with postsynaptic hyperpolarization. Blocking either receptor also suppressed long-term effects of activation of the other G-protein coupled receptor on interneuron membrane potential. However, no crossed blockade was detected for mGluR or mAchR effects on interneuron after-burst potentials or on the frequency of miniature EPSPs. Paired recordings between pyramidal neurons and oriens interneurons were obtained to determine whether LTP could be induced without concurrent stimulation of cholinergic axons. Exogenous activation of mAChRs led to LTP, with changes in EPSP amplitude distributions consistent with a presynaptic locus of expression. LTP, however, required noninvasive presynaptic and postsynaptic recordings. SIGNIFICANCE STATEMENT In the hippocampus, a form of NMDA receptor-independent long-term potentiation (LTP) occurs at excitatory synapses made on some inhibitory neurons. This is preferentially induced when postsynaptic interneurons are hyperpolarized, depends on Ca(2+) entry through Ca(2+)-permeable AMPA receptors, and has been labeled anti-Hebbian LTP. Here we show that this form of LTP also depends on activation of both group I mGluR and M1 mAChRs. We demonstrate that these G-protein coupled receptors (GPCRs) interact, because the blockade of one receptor suppresses long-term effects of activation of the other GPCR on both LTP and interneuron membrane potential. This LTP was also detected in paired recordings, although only when both presynaptic and postsynaptic recordings did not perturb the intracellular medium. Changes in EPSP amplitude distributions in dual recordings were consistent with a presynaptic locus of expression.
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Burford NT, Wehrman T, Bassoni D, O'Connell J, Banks M, Zhang L, Alt A. Identification of selective agonists and positive allosteric modulators for µ- and δ-opioid receptors from a single high-throughput screen. ACTA ACUST UNITED AC 2014; 19:1255-65. [PMID: 25047277 DOI: 10.1177/1087057114542975] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Hetero-oligomeric complexes of G protein-coupled receptors (GPCRs) may represent novel therapeutic targets exhibiting different pharmacology and tissue- or cell-specific site of action compared with receptor monomers or homo-oligomers. An ideal tool for validating this concept pharmacologically would be a hetero-oligomer selective ligand. We set out to develop and execute a 1536-well high-throughput screen of over 1 million compounds to detect potential hetero-oligomer selective ligands using a β-arrestin recruitment assay in U2OS cells coexpressing recombinant µ- and δ-opioid receptors. Hetero-oligomer selective ligands may bind to orthosteric or allosteric sites, and we might anticipate that the formation of hetero-oligomers may provide novel allosteric binding pockets for ligand binding. Therefore, our goal was to execute the screen in such a way as to identify positive allosteric modulators (PAMs) as well as agonists for µ, δ, and hetero-oligomeric receptors. While no hetero-oligomer selective ligands were identified (based on our selection criteria), this single screen did identify numerous µ- and δ-selective agonists and PAMs as well as nonselective agonists and PAMs. To our knowledge, these are the first µ- and δ-opioid receptor PAMs described in the literature.
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Affiliation(s)
- Neil T Burford
- Leads Discovery and Optimization, Bristol-Myers Squibb Company, Wallingford, CT, USA
| | | | | | | | - Martyn Banks
- Leads Discovery and Optimization, Bristol-Myers Squibb Company, Wallingford, CT, USA
| | - Litao Zhang
- Leads Discovery and Optimization, Bristol-Myers Squibb Company, Wallingford, CT, USA
| | - Andrew Alt
- Leads Discovery and Optimization, Bristol-Myers Squibb Company, Wallingford, CT, USA
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Cohen LS, Fracchiolla KE, Becker J, Naider F. Invited review GPCR structural characterization: Using fragments as building blocks to determine a complete structure. Biopolymers 2014; 102:223-43. [DOI: 10.1002/bip.22490] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2014] [Revised: 03/24/2014] [Accepted: 03/27/2014] [Indexed: 12/30/2022]
Affiliation(s)
- Leah S. Cohen
- Department of Chemistry; The College of Staten Island, City University of New York (CUNY); Staten Island NY 10314
| | - Katrina E. Fracchiolla
- Department of Chemistry; The College of Staten Island, City University of New York (CUNY); Staten Island NY 10314
| | - Jeff Becker
- Department of Microbiology; University of Tennessee; Knoxville TN 37996
| | - Fred Naider
- Department of Chemistry; The College of Staten Island, City University of New York (CUNY); Staten Island NY 10314
- Department of Biochemistry; The Graduate Center; CUNY NY 10016-4309
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Šantrůčková E, Doležal V, El-Fakahany EE, Jakubík J. Long-term activation upon brief exposure to xanomleline is unique to M1 and M4 subtypes of muscarinic acetylcholine receptors. PLoS One 2014; 9:e88910. [PMID: 24558448 PMCID: PMC3928307 DOI: 10.1371/journal.pone.0088910] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Accepted: 01/14/2014] [Indexed: 11/19/2022] Open
Abstract
Xanomeline is an agonist endowed with functional preference for M1/M4 muscarinic acetylcholine receptors. It also exhibits both reversible and wash-resistant binding to and activation of these receptors. So far the mechanisms of xanomeline selectivity remain unknown. To address this question we employed microfluorometric measurements of intracellular calcium levels and radioligand binding to investigate differences in the short- and long-term effects of xanomeline among muscarinic receptors expressed individually in Chinese hamster ovary cells. 1/One-min exposure of cells to xanomeline markedly increased intracellular calcium at hM1 and hM4, and to a lesser extent at hM2 and hM3 muscarinic receptors for more than 1 hour. 2/Unlike the classic agonists carbachol, oxotremorine, and pilocarpine 10-min exposure to xanomeline did not cause internalization of any receptor subtype. 3/Wash-resistant xanomeline selectively prevented further increase in intracellular calcium by carbachol at hM1 and hM4 receptors. 4/After transient activation xanomeline behaved as a long-term antagonist at hM5 receptors. 5/The antagonist N-methylscopolamine (NMS) reversibly blocked activation of hM1 through hM4 receptors by xanomeline. 6/NMS prevented formation of xanomeline wash-resistant binding and activation at hM2 and hM4 receptors and slowed them at hM1, hM3 and hM5 receptors. Our results show commonalities of xanomeline reversible and wash-resistant binding and short-time activation among the five muscarinic receptor subtypes. However long-term receptor activation takes place in full only at hM1 and hM4 receptors. Moreover xanomeline displays higher efficacy at hM1 and hM4 receptors in primary phasic intracellular calcium release. These findings suggest the existence of particular activation mechanisms specific to these two receptors.
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Affiliation(s)
- Eva Šantrůčková
- Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Minneapolis, United States of America
| | - Vladimír Doležal
- Institute of Physiology Academy of Sciences of the Czech Republic, Prague, Czech Republic
| | - Esam E El-Fakahany
- Department of Experimental and Clinical Pharmacology, University of Minnesota College of Pharmacy, Minneapolis, United States of America
| | - Jan Jakubík
- Institute of Physiology Academy of Sciences of the Czech Republic, Prague, Czech Republic
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Discovery of positive allosteric modulators and silent allosteric modulators of the μ-opioid receptor. Proc Natl Acad Sci U S A 2013; 110:10830-5. [PMID: 23754417 DOI: 10.1073/pnas.1300393110] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
μ-Opioid receptors are among the most studied G protein-coupled receptors because of the therapeutic value of agonists, such as morphine, that are used to treat chronic pain. However, these drugs have significant side effects, such as respiratory suppression, constipation, allodynia, tolerance, and dependence, as well as abuse potential. Efforts to fine tune pain control while alleviating the side effects of drugs, both physiological and psychological, have led to the development of a wide variety of structurally diverse agonist ligands for the μ-opioid receptor, as well as compounds that target κ- and δ-opioid receptors. In recent years, the identification of allosteric ligands for some G protein-coupled receptors has provided breakthroughs in obtaining receptor subtype-selectivity that can reduce the overall side effect profiles of a potential drug. However, positive allosteric modulators (PAMs) can also have the specific advantage of only modulating the activity of the receptor when the orthosteric agonist occupies the receptor, thus maintaining spatial and temporal control of receptor signaling in vivo. This second advantage of allosteric modulators may yield breakthroughs in opioid receptor research and could lead to drugs with improved side-effect profiles or fewer tolerance and dependence issues compared with orthosteric opioid receptor agonists. Here, we describe the discovery and characterization of μ-opioid receptor PAMs and silent allosteric modulators, identified from high-throughput screening using a β-arrestin-recruitment assay.
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Lane JR, Abdul-Ridha A, Canals M. Regulation of G protein-coupled receptors by allosteric ligands. ACS Chem Neurosci 2013; 4:527-34. [PMID: 23398684 PMCID: PMC3629737 DOI: 10.1021/cn400005t] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2013] [Accepted: 02/12/2013] [Indexed: 01/14/2023] Open
Abstract
Topographically distinct, druggable, allosteric sites may be present on all G protein-coupled receptors (GPCRs). As such, targeting these sites with synthetic small molecules offers an attractive approach to develop receptor-subtype selective chemical leads for the development of novel therapies. A crucial part of drug development is to understand the acute and chronic effects of such allosteric modulators at their corresponding GPCR target. Key regulatory processes including cell-surface delivery, endocytosis, recycling, and down-regulation tightly control the number of receptors at the surface of the cell. As many GPCR therapeutics will be administered chronically, understanding how such ligands modulate these regulatory pathways forms an essential part of the characterization of novel GPCR ligands. This is true for both orthosteric and allosteric ligands. In this Review, we summarize our current understanding of GPCR regulatory processes with a particular focus on the effects and implications of allosteric targeting of GPCRs.
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Affiliation(s)
- J. Robert Lane
- E-mail: (J.R.L.); (M.C.). Mailing
address: Drug Discovery Biology, Monash Institute of Pharmaceutical
Sciences, 399 Royal Parade, Parkville, Victoria, 3052 Australia. Telephone: +61 3 99039094
| | - Alaa Abdul-Ridha
- Drug Discovery Biology, Monash Institute of Pharmaceutical
Sciences and Department of Pharmacology, Monash University, Parkville, Victoria, 3052, Australia
| | - Meritxell Canals
- E-mail: (J.R.L.); (M.C.). Mailing
address: Drug Discovery Biology, Monash Institute of Pharmaceutical
Sciences, 399 Royal Parade, Parkville, Victoria, 3052 Australia. Telephone: +61 3 99039094
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Humbert-Claude M, Davenas E, Gbahou F, Vincent L, Arrang JM. Involvement of histamine receptors in the atypical antipsychotic profile of clozapine: a reassessment in vitro and in vivo. Psychopharmacology (Berl) 2012; 220:225-41. [PMID: 21912901 DOI: 10.1007/s00213-011-2471-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Accepted: 08/24/2011] [Indexed: 12/11/2022]
Abstract
RATIONALE The basis of the unique clinical profile of the antipsychotic clozapine is not yet elucidated. Brain histamine receptors may play a role in schizophrenia and its treatment, but their involvement in the profile of clozapine remained unknown. OBJECTIVES We explored the properties of clozapine and its two metabolites, N-desmethylclozapine (NDMC) and clozapine N-oxide, at the four human histaminergic receptors. We compared their active concentrations with their blood concentrations in patients treated by clozapine. We investigated the changes in receptor densities induced in rat brain by repeated administration of a therapeutic dose of clozapine. RESULTS Clozapine and NDMC behaved as very potent, and partial, H(1)-receptor inverse agonists, weak, and full, H(2)-receptor inverse agonists, moderate, and protean, H(3)-receptor agonists, and moderate, and partial, H(4)-receptor agonists. Taking into account their micromolar mean blood concentrations found in 75 treated patients, and assuming that they are enriched in human brain as they are in rat brain, a full occupation of H(1)-, H(3)-, and H(4)-receptors, and a partial occupation of H(2) receptors, is expected. In agreement, repeated administration of clozapine at a therapeutic dose (20 mg/kg/day for 20 days) induced an up-regulation of H(1)- and H(2)-receptors in rat brain. CONCLUSIONS Clozapine and its active metabolite NDMC interact with the four human histamine receptors at clinically relevant concentrations. This interaction may substantiate, at least in part, the atypical antipsychotic profile of clozapine, as well as its central and peripheral side effects such as sedation and weight gain.
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Affiliation(s)
- Marie Humbert-Claude
- Laboratoire de Neurobiologie et Pharmacologie Moléculaire, Centre de Psychiatrie et Neurosciences (CPN, U 894), INSERM, 2 ter rue d'Alésia, 75014 Paris, France
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Decker M, Holzgrabe U. M1 muscarinic cetylcholine receptor allosteric modulators as potential therapeutic opportunities for treating Alzheimer's disease. MEDCHEMCOMM 2012. [DOI: 10.1039/c2md20025b] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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Abstract
Knowledge of the mechanisms responsible for the trafficking of neurotransmitter receptors away from the cell surface is of obvious importance in understanding what regulates their expression and function. This chapter will focus on the mechanisms responsible for the internalization and degradation of muscarinic receptors. There are both receptor subtype-specific and cell-type specific differences in muscarinic receptor trafficking. Studies on muscarinic receptor trafficking both in cells in culture and in vivo will be described, and the potential physiological consequences of this trafficking will be discussed.
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Affiliation(s)
- Cindy Reiner
- Department of Pharmacology, University of Washington, 357750, Seattle, WA 98195-7750, USA
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Burford NT, Watson J, Bertekap R, Alt A. Strategies for the identification of allosteric modulators of G-protein-coupled receptors. Biochem Pharmacol 2011; 81:691-702. [DOI: 10.1016/j.bcp.2010.12.012] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2010] [Revised: 12/09/2010] [Accepted: 12/10/2010] [Indexed: 11/15/2022]
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Grant MKO, Noetzel MJ, De Lorme KC, Jakubík J, Doležal V, El-Fakahany EE. Pharmacological evaluation of the long-term effects of xanomeline on the M(1) muscarinic acetylcholine receptor. PLoS One 2010; 5:e15722. [PMID: 21203415 PMCID: PMC3009740 DOI: 10.1371/journal.pone.0015722] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 11/28/2010] [Indexed: 11/19/2022] Open
Abstract
Xanomeline is a unique agonist of muscarinic receptors that possesses functional selectivity at the M1 and M4 receptor subtypes. It also exhibits wash-resistant binding to and activation of the receptor. In the present work we investigated the consequences of this type of binding of xanomeline on the binding characteristics and function of the M1 muscarinic receptor. Pretreatment of CHO cells that stably express the M1 receptor for 1 hr with increasing concentrations of xanomeline followed by washing and waiting for an additional 23 hr in control culture media transformed xanomeline-induced inhibition of [3H]NMS binding from monophasic to biphasic. The high-affinity xanomeline binding site exhibited three orders of magnitude higher affinity than in the case of xanomeline added directly to the binding assay medium containing control cells. These effects were associated with a marked decrease in maximal radioligand binding and attenuation of agonist-induced increase in PI hydrolysis and were qualitatively similar to those caused by continuous incubation of cells with xanomeline for 24 hr. Attenuation of agonist-induced PI hydrolysis by persistently-bound xanomeline developed with a time course that parallels the return of receptor activation by prebound xanomeline towards basal levels. Additional data indicated that blockade of the receptor orthosteric site or the use of a non-functional receptor mutant reversed the long-term effects of xanomeline, but not its persistent binding at an allosteric site. Furthermore, the long-term effects of xanomeline on the receptor are mainly due to receptor down-regulation rather than internalization.
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Affiliation(s)
- Marianne K. O. Grant
- Department of Psychiatry, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
| | - Meredith J. Noetzel
- Department of Psychiatry, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
| | - Kayla C. De Lorme
- Department of Psychiatry, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
| | - Jan Jakubík
- Department of Neurochemistry, Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
- * E-mail:
| | - Vladimír Doležal
- Department of Neurochemistry, Institute of Physiology, Czech Academy of Sciences, Prague, Czech Republic
| | - Esam E. El-Fakahany
- Department of Psychiatry, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
- Department of Pharmacology, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
- Department of Neuroscience, University of Minnesota Medical School, Minneapolis, Minnesota, United States of America
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18
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Whalen EJ, Rajagopal S, Lefkowitz RJ. Therapeutic potential of β-arrestin- and G protein-biased agonists. Trends Mol Med 2010; 17:126-39. [PMID: 21183406 DOI: 10.1016/j.molmed.2010.11.004] [Citation(s) in RCA: 418] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2010] [Revised: 11/13/2010] [Accepted: 11/17/2010] [Indexed: 12/21/2022]
Abstract
Members of the seven-transmembrane receptor (7TMR), or G protein-coupled receptor (GPCR), superfamily represent some of the most successful targets of modern drug therapy, with proven efficacy in the treatment of a broad range of human conditions and disease processes. It is now appreciated that β-arrestins, once viewed simply as negative regulators of traditional 7TMR-stimulated G protein signaling, act as multifunctional adapter proteins that regulate 7TMR desensitization and trafficking and promote distinct intracellular signals in their own right. Moreover, several 7TMR biased agonists, which selectively activate these divergent signaling pathways, have been identified. Here we highlight the diversity of G protein- and β-arrestin-mediated functions and the therapeutic potential of selective targeting of these in disease states.
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Affiliation(s)
- Erin J Whalen
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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Digby GJ, Conn PJ, Lindsley CW. Orthosteric- and allosteric-induced ligand-directed trafficking at GPCRs. CURRENT OPINION IN DRUG DISCOVERY & DEVELOPMENT 2010; 13:587-594. [PMID: 20812150 PMCID: PMC3821179] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Many orthosteric agonists differentially activate downstream effectors of GPCRs. Such defined induction of signaling has strongly supported the hypothesis termed 'ligand-directed trafficking of receptor signaling' (LDTRS). More recently, subtype-selective GPCR activators, such as allosteric agonists and positive allosteric modulators, have also exhibited the capacity to activate specific signaling pathways. Based on this finding, it may be possible to achieve ligand-specific receptor active states that optimize the biological responses specific to GPCRs. This review discusses recent studies in which both orthosteric and allosteric compounds have been demonstrated to induce LDTRS.
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Affiliation(s)
- Gregory J Digby
- Vanderbilt University School of Medicine, Department of Pharmacology, 12415D MRBIV (Langford), Nashville, TN 37232, USA
| | - P Jeffrey Conn
- Vanderbilt University School of Medicine, Department of Pharmacology, 12415D MRBIV (Langford), Nashville, TN 37232, USA
- Vanderbilt University School of Medicine, Vanderbilt Program in Drug Discovery, 12415D MRBIV (Langford), Nashville, TN 37232, USA
| | - Craig W Lindsley
- Vanderbilt University School of Medicine, Department of Pharmacology, 12415D MRBIV (Langford), Nashville, TN 37232, USA
- Vanderbilt University School of Medicine, Vanderbilt Program in Drug Discovery, 12415D MRBIV (Langford), Nashville, TN 37232, USA
- Vanderbilt University, Department of Chemistry, 7330 Stevenson Center, Station B 351822, Nashville, TN 37235, USA
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Davis AA, Heilman CJ, Brady AE, Miller NR, Fuerstenau-Sharp M, Hanson BJ, Lindsley CW, Conn PJ, Lah JJ, Levey AI. Differential effects of allosteric M(1) muscarinic acetylcholine receptor agonists on receptor activation, arrestin 3 recruitment, and receptor downregulation. ACS Chem Neurosci 2010; 1:542-551. [PMID: 20835371 DOI: 10.1021/cn100011e] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Muscarinic acetylcholine receptors (mAChRs) are drug targets for multiple neurodegenerative and neuropsychiatric disorders, but the full therapeutic potential of mAChR-targeted drugs has not been realized, mainly because of a lack of subtype-selective agonists. Recent advances have allowed the development of highly selective agonists that bind to an allosteric site on the M(1) mAChR that is spatially distinct from the orthosteric acetylcholine binding site, but less is known about the profile of intracellular signals activated by orthosteric versus allosteric M(1) mAChR agonists. We investigated the activation and regulatory mechanisms of two structurally distinct allosteric M(1) mAChR agonists, AC260584 and TBPB. We show that allosteric agonists potently activate multiple signal transduction pathways linked to the M(1) mAChR receptor but, compared to orthosteric agonists, much less efficiently recruit arrestin 3, a protein involved in regulation of G-protein coupled receptor signaling. Consistent with decreased arrestin recruitment, both allosteric agonists showed blunted responses in measurements of receptor desensitization, internalization, and downregulation. These results advance the understanding of mAChR biology and may shed light on unanticipated differences in the pharmacology of orthosteric vs. allosteric agonists that might be capitalized upon for drug development for the treatment of CNS diseases.
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Affiliation(s)
- Albert A. Davis
- Center for Neurodegenerative Disease and Department of Neurology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Craig J. Heilman
- Center for Neurodegenerative Disease and Department of Neurology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Ashley E. Brady
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Nicole R. Miller
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | | | | | - Craig W. Lindsley
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
- Department of Chemistry, Vanderbilt University Medical Center, Nashville, Tennessee 37232
- Vanderbilt Program in Drug Discovery, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - P. Jeffrey Conn
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
- Department of Chemistry, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - James J. Lah
- Center for Neurodegenerative Disease and Department of Neurology, Emory University School of Medicine, Atlanta, Georgia 30322
| | - Allan I. Levey
- Center for Neurodegenerative Disease and Department of Neurology, Emory University School of Medicine, Atlanta, Georgia 30322
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