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Bhatia V, Maghsoudi S, Hinton M, Bhagirath AY, Singh N, Jaggupilli A, Chelikani P, Dakshinamurti S. Characterization of Adenylyl Cyclase Isoform 6 Residues Interacting with Forskolin. BIOLOGY 2023; 12:biology12040572. [PMID: 37106773 PMCID: PMC10135528 DOI: 10.3390/biology12040572] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/17/2023] [Revised: 03/26/2023] [Accepted: 04/03/2023] [Indexed: 04/29/2023]
Abstract
BACKGROUND The adenylyl cyclase (AC) pathway, crucial for pulmonary vasodilation, is inhibited by hypoxia. Forskolin (FSK) binds allosterically to AC, stimulating ATP catalysis. As AC6 is the primary AC isoform in the pulmonary artery, selective reactivation of AC6 could provide targeted reinstatement of hypoxic AC activity. This requires elucidation of the FSK binding site in AC6. METHODS HEK293T cells stably overexpressing AC 5, 6, or 7 were incubated in normoxia (21% O2) or hypoxia (10% O2) or exposed to s-nitrosocysteine (CSNO). AC activity was measured using terbium norfloxacin assay; AC6 structure built by homology modeling; ligand docking to examine FSK-interacting amino acids; roles of selected residues determined by site-directed mutagenesis; FSK-dependent cAMP generation measured in wild-type and FSK-site mutants by biosensor-based live cell assay. RESULTS Only AC6 is inhibited by hypoxia and nitrosylation. Homology modeling and docking revealed residues T500, N503, and S1035 interacting with FSK. Mutation of T500, N503, or S1035 decreased FSK-stimulated AC activity. FSK site mutants were not further inhibited by hypoxia or CSNO; however, mutation of any of these residues prevented AC6 activation by FSK following hypoxia or CSNO treatment. CONCLUSIONS FSK-interacting amino acids are not involved in the hypoxic inhibition mechanism. This study provides direction to design FSK derivatives for selective activation of hypoxic AC6.
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Affiliation(s)
- Vikram Bhatia
- Biology of Breathing Theme, Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada
- Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada
- Department of Pediatrics and Child Health, University of Manitoba, Winnipeg, MB R3A 1S1, Canada
| | - Saeid Maghsoudi
- Biology of Breathing Theme, Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - Martha Hinton
- Biology of Breathing Theme, Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - Anjali Y Bhagirath
- Biology of Breathing Theme, Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada
- Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada
| | - Nisha Singh
- Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada
| | | | - Prashen Chelikani
- Biology of Breathing Theme, Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada
- Department of Oral Biology, University of Manitoba, Winnipeg, MB R3E 0W2, Canada
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
- Department of Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
| | - Shyamala Dakshinamurti
- Biology of Breathing Theme, Children's Hospital Research Institute of Manitoba, Winnipeg, MB R3E 3P4, Canada
- Department of Pediatrics and Child Health, University of Manitoba, Winnipeg, MB R3A 1S1, Canada
- Department of Physiology and Pathophysiology, University of Manitoba, Winnipeg, MB R3E 0J9, Canada
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2
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Prostacyclin Analogues Inhibit Platelet Reactivity, Extracellular Vesicle Release and Thrombus Formation in Patients with Pulmonary Arterial Hypertension. J Clin Med 2021; 10:jcm10051024. [PMID: 33801460 PMCID: PMC7958838 DOI: 10.3390/jcm10051024] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2021] [Revised: 02/12/2021] [Accepted: 02/19/2021] [Indexed: 12/13/2022] Open
Abstract
(1) Background: Prostacyclin analogues (epoprostenol, treprostinil, and iloprost) induce vasodilation in pulmonary arterial hypertension (PAH) but also inhibit platelet function. (2) Objectives: We assessed platelet function in PAH patients treated with prostacyclin analogues and not receiving prostacyclin analogues. (3) Methods: Venous blood was collected from 42 patients treated with prostacyclin analogues (49.5 ± 15.9 years, 81% female) and 38 patients not receiving prostacyclin analogues (55.5 ± 15.6 years, 74% female). Platelet reactivity was analyzed by impedance aggregometry using arachidonic acid (AA; 0.5 mM), adenosine diphosphate (ADP; 6.5 µM), and thrombin receptor-activating peptide (TRAP; 32 µM) as agonists. In a subset of patients, concentrations of extracellular vesicles (EVs) from all platelets (CD61+), activated platelets (CD61+/CD62P+), leukocytes (CD45+), and endothelial cells (CD146+) were analyzed by flow cytometry. Platelet-rich thrombus formation was measured using a whole blood perfusion system. (4) Results: Compared to controls, PAH patients treated with prostacyclin analogues had lower platelet reactivity in response to AA and ADP (p = 0.01 for both), lower concentrations of platelet and leukocyte EVs (p ≤ 0.04), delayed thrombus formation (p ≤ 0.003), and decreased thrombus size (p = 0.008). Epoprostenol did not affect platelet reactivity but decreased the concentrations of platelet and leukocyte EVs (p ≤ 0.04). Treprostinil decreased platelet reactivity in response to AA and ADP (p ≤ 0.02) but had no effect on the concentrations of EVs. All prostacyclin analogues delayed thrombus formation and decreased thrombus size (p ≤ 0.04). (5) Conclusions: PAH patients treated with prostacyclin analogues had impaired platelet reactivity, EV release, and thrombus formation, compared to patients not receiving prostacyclin analogues.
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Biringer RG. A Review of Prostanoid Receptors: Expression, Characterization, Regulation, and Mechanism of Action. J Cell Commun Signal 2020; 15:155-184. [PMID: 32970276 DOI: 10.1007/s12079-020-00585-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2020] [Accepted: 09/15/2020] [Indexed: 12/22/2022] Open
Abstract
Prostaglandin signaling controls a wide range of biological processes from blood pressure homeostasis to inflammation and resolution thereof to the perception of pain to cell survival. Disruption of normal prostanoid signaling is implicated in numerous disease states. Prostaglandin signaling is facilitated by G-protein-coupled, prostanoid-specific receptors and the array of associated G-proteins. This review focuses on the expression, characterization, regulation, and mechanism of action of prostanoid receptors with particular emphasis on human isoforms.
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Affiliation(s)
- Roger G Biringer
- College of Osteopathic Medicine, Lake Erie College of Osteopathic Medicine, 5000 Lakewood Ranch Blvd, Bradenton, FL, 34211, USA.
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4
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Connolly A, Holleran BJ, Simard É, Baillargeon JP, Lavigne P, Leduc R. Interplay between intracellular loop 1 and helix VIII of the angiotensin II type 2 receptor controls its activation. Biochem Pharmacol 2019; 168:330-338. [PMID: 31348898 DOI: 10.1016/j.bcp.2019.07.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 07/19/2019] [Indexed: 01/09/2023]
Abstract
The signaling mechanisms of the angiotensin II type 2 receptor (AT2R), a heptahelical receptor, have not yet been clearly and completely defined. In the present contribution, we set out to identify the molecular determinants involved in AT2R activation. Although AT2R has not been shown to engage Gq/11, G12, Gi2, and β-arrestin (βarr) pathways as does the AT1R upon angiotensin II (AngII) stimulation, the atypical positioning of helix VIII in the recently published AT2R structure may play a role in the receptor's capacity to couple to downstream effectors. In the AT2R structure, helix VIII points inwards and towards intracellular loop 3 (ICL3) to form tertiary interactions with transmembrane domain 6 (TM6), possibly impeding access to signaling effectors. On the other hand, in most class A GPCRs, helix VIII is found to be engaged in tertiary interactions with ICL1 and away from the effector binding site. Upon closer examination of the AT2R structure, we found that the residues contained within intracellular loop 1 (ICL1) may be involved in driving this unusual conformation of helix VIII. To explore this hypothesis, we designed a series of AT1R/AT2R receptor chimeras to validate the roles of ICL1 and helix VIII in AT2R signaling. Substituting the AT1R ICL1 into AT2R led to a mutant receptor that coupled to Gi2. The substitution of the helix VIII and C-terminal domains of AT2R into the AT1R backbone led to a mutant receptor that retained AT1R-like signaling properties. These results suggest that the C-terminal portion of AT2R is compatible with canonical GPCR signaling and that ICL1 of AT2R is involved in repositioning helix VIII, which impedes engagement of classical GPCR effectors such as G proteins or βarrs.
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Affiliation(s)
- Alexandre Connolly
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de Pharmacologie de Sherbrooke, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Brian J Holleran
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de Pharmacologie de Sherbrooke, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Élie Simard
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de Pharmacologie de Sherbrooke, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Jean-Patrice Baillargeon
- Division of Endocrinology, Department of Medicine, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke J1H 5N4, Québec, Canada
| | - Pierre Lavigne
- Institut de Pharmacologie de Sherbrooke, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada; Department of Biochemistry, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Richard Leduc
- Department of Pharmacology-Physiology, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada; Institut de Pharmacologie de Sherbrooke, Faculty of Medicine and Health Sciences, Université de Sherbrooke, Sherbrooke, Québec, Canada.
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5
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Abstract
Platelet activity is regulated by a number of surface expressed G protein-coupled receptors (GPCRs) including the α isoform of the thromboxane receptor (TPα receptor). With the advance of genomic technologies, there has been a substantial increase in the identification of naturally occurring rare GPCR variants including in the TBXA2R gene, which encodes the TPα receptor. The study of patients with naturally occurring variants within TBXA2R associated with bleeding and abnormal TPα receptor function has provided a powerful insight in defining the critical role of TPα in thrombus formation. This review will highlight how the identification of these function-disrupting variants of the platelet TPα has contributed important structure-function information about these GPCRs. Further we discuss the potential implications these findings have for understanding the molecular basis of mild platelet based bleeding disorders.
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Affiliation(s)
- Stuart James Mundell
- a School of Physiology, Pharmacology and Neuroscience , University of Bristol , Bristol , UK
| | - Andrew Mumford
- b School of Clinical Science and School of Cellular and Molecular Medicine , University of Bristol , Bristol , UK
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6
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Cheng Y, Vanhoutte PM, Leung SWS. Apolipoprotein E favours the blunting by high-fat diet of prostacyclin receptor activation in the mouse aorta. Br J Pharmacol 2018; 175:3453-3469. [PMID: 29859010 DOI: 10.1111/bph.14386] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 05/21/2018] [Accepted: 05/29/2018] [Indexed: 11/27/2022] Open
Abstract
BACKGROUND AND PURPOSE NO-mediated, endothelium-dependent relaxations of isolated arteries are blunted by ageing and high-fat diets, as well as by apolipoprotein E deletion. The present study was designed to test the hypothesis that apolipoprotein E deletion impairs endothelium-dependent responses to prostacyclin (IP) receptor activation. EXPERIMENTAL APPROACH Five-week-old ApoE+/+ and ApoE-/- mice were fed normal chow or high-fat diet for 29 weeks. The aortae were isolated for the measurements of isometric tension in Halpern-Mulvany myographs. Levels of proteins were assessed by Western blotting and immunofluorescence, and cyclic nucleotide levels by elisa. KEY RESULTS The IP receptor agonist, iloprost, induced endothelium-, NO-synthase- and IP-dependent relaxations in aortae of young ApoE+/+ mice. High-fat diet favoured activation of thromboxane receptors by iloprost, causing contraction. Apolipoprotein E was present in aortae of ApoE+/+ mice, especially in endothelium. Its presence was augmented by high-fat diet. Its deletion potentiated iloprost-induced relaxations in aortae of young mice and prevented the blunting of this response by high-fat diet. Levels of cAMP were higher, but those of cGMP were lower in the aorta of ApoE-/- than in ApoE+/+ mice of the same age. The levels of IP receptor protein were not different between ApoE+/+ and ApoE-/- mice. CONCLUSIONS AND IMPLICATIONS Iloprost induced an endothelium-dependent relaxation in the aorta of young healthy mice which involved both the cGMP and cAMP pathways. This response was blunted by prolonged exposure to a high-fat diet. Apolipoprotein E deletion potentiated relaxations to IP receptor activation, independently of age and diet.
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Affiliation(s)
- Yanhua Cheng
- Department of Pharmacology and Pharmacy, The University of Hong Kong, Hong Kong, SAR, China
| | - Paul M Vanhoutte
- Department of Pharmacology and Pharmacy, The University of Hong Kong, Hong Kong, SAR, China
| | - Susan W S Leung
- Department of Pharmacology and Pharmacy, The University of Hong Kong, Hong Kong, SAR, China
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7
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Chakraborty R, Sikarwar AS, Hinton M, Dakshinamurti S, Chelikani P. Characterization of GPCR signaling in hypoxia. Methods Cell Biol 2018; 142:101-110. [PMID: 28964329 DOI: 10.1016/bs.mcb.2017.07.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
G protein-coupled receptors (GPCRs) signal in response to various external stimuli including stress. GPCR signaling has been shown to play a critical role in the adaptation of cell response to limited oxygen supply. Hypoxia has been implicated in cardiovascular diseases, human pulmonary arterial responses, and persistent pulmonary hypertension in newborns. One of the key GPCRs implicated in hypoxia is the prostanoid receptor, thromboxane A2 receptor (TP). Hypoxia can affect TP localization, stability, and activity both in vivo and in vitro. To elucidate hypoxia-mediated GPCR signaling in vitro, we lay out a general strategy to perform hypoxic experiments using both primary pulmonary artery smooth muscle cells and TP expressed in HEK293T cells. We describe assay for measuring moderate tissue hypoxia using static cell cultures, monitoring pericellular media oxygen content, and signaling of TP.
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Affiliation(s)
- Raja Chakraborty
- College of Dentistry, Winnipeg, MB, Canada; Manitoba Chemosensory Biology (MCSB) Research Group, University of Manitoba, Winnipeg, MB, Canada; Biology of Breathing Group, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
| | - Anurag Singh Sikarwar
- College of Dentistry, Winnipeg, MB, Canada; Manitoba Chemosensory Biology (MCSB) Research Group, University of Manitoba, Winnipeg, MB, Canada; Biology of Breathing Group, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada
| | - Martha Hinton
- Biology of Breathing Group, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada; College of Medicine, University of Manitoba, Winnipeg, MB, Canada
| | - Shyamala Dakshinamurti
- Manitoba Chemosensory Biology (MCSB) Research Group, University of Manitoba, Winnipeg, MB, Canada; Biology of Breathing Group, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada; College of Medicine, University of Manitoba, Winnipeg, MB, Canada
| | - Prashen Chelikani
- College of Dentistry, Winnipeg, MB, Canada; Manitoba Chemosensory Biology (MCSB) Research Group, University of Manitoba, Winnipeg, MB, Canada; Biology of Breathing Group, Children's Hospital Research Institute of Manitoba, Winnipeg, MB, Canada.
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8
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Abstract
The Reggio group has constructed computer models of the inactive and G-protein-activated states of the cannabinoid CB1 and CB2 receptors, as well as, several orphan receptors that recognize a subset of cannabinoid compounds, including GPR55 and GPR18. These models have been used to design ligands, mutations, and covalent labeling studies. The resultant second-generation models have been used to design ligands with improved affinity, efficacy, and subtype selectivity. Herein, we provide a guide for the development of GPCR models using the most recent orphan receptor studied in our lab, GPR3. GPR3 is an orphan receptor that belongs to the Class A family of G-protein-coupled receptors. It shares high sequence similarity with GPR6, GPR12, the lysophospholipid receptors, and the cannabinoid receptors. GPR3 is predominantly expressed in mammalian brain and oocytes and it is known as a Gαs-coupled receptor activated constitutively in cells. GPR3 represents a possible target for the treatment of different pathological conditions such as Alzheimer's disease, oocyte maturation, or neuropathic pain. However, the lack of potent and selective GPR3 ligands is delaying the exploitation of this promising therapeutic target. In this context, we aim to develop a homology model that helps us to elucidate the structural determinants governing ligand-receptor interactions at GPR3. In this chapter, we detail the methods and rationale behind the construction of the GPR3 active-and inactive-state models. These homology models will enable the rational design of novel ligands, which may serve as research tools for further understanding of the biological role of GPR3.
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Affiliation(s)
- Paula Morales
- University of North Carolina at Greensboro, Greensboro, NC, United States.
| | - Dow P Hurst
- University of North Carolina at Greensboro, Greensboro, NC, United States
| | - Patricia H Reggio
- University of North Carolina at Greensboro, Greensboro, NC, United States
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9
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Pluchart H, Khouri C, Blaise S, Roustit M, Cracowski JL. Targeting the Prostacyclin Pathway: Beyond Pulmonary Arterial Hypertension. Trends Pharmacol Sci 2017; 38:512-523. [DOI: 10.1016/j.tips.2017.03.003] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2016] [Revised: 03/03/2017] [Accepted: 03/06/2017] [Indexed: 01/08/2023]
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10
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Bhagirath AY, Pydi SP, Li Y, Lin C, Kong W, Chelikani P, Duan K. Characterization of the Direct Interaction between Hybrid Sensor Kinases PA1611 and RetS That Controls Biofilm Formation and the Type III Secretion System in Pseudomonas aeruginosa. ACS Infect Dis 2017; 3:162-175. [PMID: 27957853 DOI: 10.1021/acsinfecdis.6b00153] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
One of the leading causes of morbidity and mortality in cystic fibrosis (CF) patients is pulmonary infection with Pseudomonas aeruginosa, and the pathophysiology of pulmonary infection in CF is affected by the lifestyle of this micro-organism. RetS-GacS/A-RsmA is a key regulatory pathway in P. aeruginosa that determines the bacterium's lifestyle choice. Previously, we identified PA1611, a hybrid sensor kinase, as a new player in this pathway that interacts with RetS and influences biofilm formation and type III secretion system. In this study, we explored the structural and mechanistic basis of the interaction between PA1611 and RetS. We identified the amino acid residues critical for PA1611-RetS interactions by molecular modeling. These residues were then targeted for site-directed mutagenesis. Amino acid substitutions were carried out at seven key positions in PA1611 and at six corresponding key positions in RetS. The influence of such substitutions in PA1611 on the interaction was analyzed by bacterial two-hybrid assays. We carried out functional analysis of these mutants in P. aeruginosa for their effect on specific phenotypes. Two residues, F269 and E276, located within the histidine kinase A and histidine kinase-like ATPase domains of PA1611 were found to play crucial roles in the PA1611-RetS interaction and had profound effects on phenotypes. Corresponding mutations in RetS demonstrated similar results. We further confirmed that these mutations in PA1611 function through the GacS/GacA-RsmY/Z signaling pathway. Collectively, our findings provide a noncognate sensor kinase direct interaction model for a signaling pathway, key for lifestyle selection in P. aeruginosa, and targeting such interaction may serve as a novel way of controlling infections with P. aeruginosa.
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Affiliation(s)
- Anjali Y. Bhagirath
- Department of Oral
Biology and Manitoba Chemosensory Biology Research Group, College
of Dentistry, Rady Faculty of Health Sciences, 780 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W2, Canada
- Biology of Breathing
Group, Children’s Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg, Manitoba R3E 3P4, Canada
| | - Sai P. Pydi
- Department of Oral
Biology and Manitoba Chemosensory Biology Research Group, College
of Dentistry, Rady Faculty of Health Sciences, 780 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W2, Canada
| | - Yanqi Li
- Department of Oral
Biology and Manitoba Chemosensory Biology Research Group, College
of Dentistry, Rady Faculty of Health Sciences, 780 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W2, Canada
- Biology of Breathing
Group, Children’s Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg, Manitoba R3E 3P4, Canada
| | - Chen Lin
- Department of Oral
Biology and Manitoba Chemosensory Biology Research Group, College
of Dentistry, Rady Faculty of Health Sciences, 780 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W2, Canada
| | - Weina Kong
- Department of Oral
Biology and Manitoba Chemosensory Biology Research Group, College
of Dentistry, Rady Faculty of Health Sciences, 780 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W2, Canada
| | - Prashen Chelikani
- Department of Oral
Biology and Manitoba Chemosensory Biology Research Group, College
of Dentistry, Rady Faculty of Health Sciences, 780 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W2, Canada
- Biology of Breathing
Group, Children’s Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg, Manitoba R3E 3P4, Canada
| | - Kangmin Duan
- Department of Oral
Biology and Manitoba Chemosensory Biology Research Group, College
of Dentistry, Rady Faculty of Health Sciences, 780 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0W2, Canada
- Department of Medical
Microbiology and Infectious Diseases, Max Rady College of Medicine, Rady Faculty of Health Sciences, 745 Bannatyne Avenue, Winnipeg, Manitoba, R3E 0J9, Canada
- Biology of Breathing
Group, Children’s Hospital Research Institute of Manitoba, 715 McDermot Avenue, Winnipeg, Manitoba R3E 3P4, Canada
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11
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Molecular mechanisms of target recognition by lipid GPCRs: relevance for cancer. Oncogene 2015; 35:4021-35. [DOI: 10.1038/onc.2015.467] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 11/02/2015] [Accepted: 11/02/2015] [Indexed: 12/18/2022]
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12
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Zhang B, Yang X, Tiberi M. Functional importance of two conserved residues in intracellular loop 1 and transmembrane region 2 of Family A GPCRs: insights from ligand binding and signal transduction responses of D1 and D5 dopaminergic receptor mutants. Cell Signal 2015; 27:2014-25. [PMID: 26186971 DOI: 10.1016/j.cellsig.2015.07.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Revised: 06/30/2015] [Accepted: 07/10/2015] [Indexed: 12/31/2022]
Abstract
For many G protein-coupled receptors (GPCRs), the role of the first intracellular loop (IL1) and its connections with adjacent transmembrane (TM) regions have not been investigated. Notably, these regions harbor several polar residues such as Ser and Thr. To begin uncovering how these polar residues may contribute to the structural basis for GPCR functionality, we have designed human D1-class receptor mutants (hD1-ST1 and hD5-ST1) whereby all Ser and Thr of IL1 and IL1/TM2 juncture have been replaced by Ala and Val, respectively. Both ST1 mutants exhibited a loss of dopamine affinity but similar binding properties for inverse agonists compared to their parent receptors. As well, these mutations diminished receptor activation for both subtypes, as indicated by an ablated constitutive activity and a pronounced decrease in dopamine potency. Interestingly, both mutants exhibited enhanced dopamine-mediated maximal stimulation (Emax) of adenylyl cyclase that was at least two-fold higher than wild-type. Point mutations for hD1R revealed that the loss in dopamine affinity and potency was attributed to Thr59, while the enhanced Emax of adenylyl cyclase was directly influenced by Ser65. These two residues are conserved among many Family A GPCRs and have recurring molecular interactions among crystallized structures. As such, their functional roles for IL1 and its transition into TM2 reported herein may also be applicable to other GPCRs. Our work thus potentially highlights a structural role of Thr59 and Ser65 in the formation of critical intramolecular interactions for ligand binding and signal transduction of D1-class dopaminergic receptors.
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Affiliation(s)
- Boyang Zhang
- Ottawa Hospital Research Institute, Neuroscience Program, Ottawa, Ontario K1H 8M5, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario K1H 8M5, Canada; Departments of Medicine, Cellular & Molecular Medicine, and Psychiatry, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Xiaodi Yang
- Ottawa Hospital Research Institute, Neuroscience Program, Ottawa, Ontario K1H 8M5, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario K1H 8M5, Canada; Departments of Medicine, Cellular & Molecular Medicine, and Psychiatry, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
| | - Mario Tiberi
- Ottawa Hospital Research Institute, Neuroscience Program, Ottawa, Ontario K1H 8M5, Canada; University of Ottawa Brain and Mind Research Institute, Ottawa, Ontario K1H 8M5, Canada; Departments of Medicine, Cellular & Molecular Medicine, and Psychiatry, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada.
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13
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14
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Pulmonary vascular changes in asthma and COPD. Pulm Pharmacol Ther 2014; 29:144-55. [DOI: 10.1016/j.pupt.2014.09.003] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Revised: 09/10/2014] [Accepted: 09/12/2014] [Indexed: 12/11/2022]
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15
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Nisar SP, Jones ML, Cunningham MR, Mumford AD, Mundell SJ. Rare platelet GPCR variants: what can we learn? Br J Pharmacol 2014; 172:3242-53. [PMID: 25231155 DOI: 10.1111/bph.12941] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2014] [Revised: 09/05/2014] [Accepted: 09/09/2014] [Indexed: 12/31/2022] Open
Abstract
Platelet-expressed GPCRs are critical regulators of platelet function. Pharmacological blockade of these receptors forms a powerful therapeutic tool in the treatment and prevention of arterial thrombosis associated with coronary atherosclerosis and ischaemic stroke. However, anti-thrombotic drug therapy is associated with high inter-patient variability in therapeutic response and adverse bleeding side effects. In order to optimize the use of existing anti-platelet drugs and to develop new therapies, more detailed knowledge is required relating to the molecular mechanisms that regulate GPCR and therefore platelet function. One approach has been to identify rare, function-disrupting mutations within key platelet proteins in patients with bleeding disorders. In this review, we describe how an integrated functional genomics strategy has contributed important structure-function information about platelet GPCRs with specific emphasis upon purinergic and thromboxane A2 receptors. We also discuss the potential implications these findings have for pharmacotherapy and for understanding the molecular basis of mild bleeding disorders.
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Affiliation(s)
- S P Nisar
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - M L Jones
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - M R Cunningham
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
| | - A D Mumford
- School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - S J Mundell
- School of Physiology and Pharmacology, University of Bristol, Bristol, UK
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Upadhyaya JD, Singh N, Sikarwar AS, Chakraborty R, Pydi SP, Bhullar RP, Dakshinamurti S, Chelikani P. Dextromethorphan mediated bitter taste receptor activation in the pulmonary circuit causes vasoconstriction. PLoS One 2014; 9:e110373. [PMID: 25340739 PMCID: PMC4207743 DOI: 10.1371/journal.pone.0110373] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2014] [Accepted: 09/11/2014] [Indexed: 12/14/2022] Open
Abstract
Activation of bitter taste receptors (T2Rs) in human airway smooth muscle cells leads to muscle relaxation and bronchodilation. This finding led to our hypothesis that T2Rs are expressed in human pulmonary artery smooth muscle cells and might be involved in regulating the vascular tone. RT-PCR was performed to reveal the expression of T2Rs in human pulmonary artery smooth muscle cells. Of the 25 T2Rs, 21 were expressed in these cells. Functional characterization was done by calcium imaging after stimulating the cells with different bitter agonists. Increased calcium responses were observed with most of the agonists, the largest increase seen for dextromethorphan. Previously in site-directed mutational studies, we have characterized the response of T2R1 to dextromethorphan, therefore, T2R1 was selected for further analysis in this study. Knockdown with T2R1 specific shRNA decreased mRNA levels, protein levels and dextromethorphan-induced calcium responses in pulmonary artery smooth muscle cells by up to 50%. To analyze if T2Rs are involved in regulating the pulmonary vascular tone, ex vivo studies using pulmonary arterial and airway rings were pursued. Myographic studies using porcine pulmonary arterial and airway rings showed that stimulation with dextromethorphan led to contraction of the pulmonary arterial and relaxation of the airway rings. This study shows that dextromethorphan, acting through T2R1, causes vasoconstrictor responses in the pulmonary circuit and relaxation in the airways.
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Affiliation(s)
| | - Nisha Singh
- Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada
| | - Anurag S. Sikarwar
- Departments of Pediatrics, Physiology, University of Manitoba, Winnipeg, MB, Canada
| | - Raja Chakraborty
- Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada
| | - Sai P. Pydi
- Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada
| | | | - Shyamala Dakshinamurti
- Departments of Pediatrics, Physiology, University of Manitoba, Winnipeg, MB, Canada
- Manitoba Institute of Child Health, Winnipeg, MB, Canada
| | - Prashen Chelikani
- Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada
- Manitoba Institute of Child Health, Winnipeg, MB, Canada
- * E-mail:
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Park MK, Choi JK, Kim HJ, Nakahata N, Lim KM, Kim SY, Lee CH. Novel inhibitory effects of cardamonin on thromboxane A2-induced scratching response: Blocking of Gh/transglutaminase-2 binding to thromboxane A2 receptor. Pharmacol Biochem Behav 2014; 126:131-5. [PMID: 25285619 DOI: 10.1016/j.pbb.2014.09.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2014] [Revised: 08/15/2014] [Accepted: 09/13/2014] [Indexed: 12/12/2022]
Abstract
Alpinia katsumadai is known to suppress thromboxane A2 (TXA2) receptor agonist-induced scratching in mice. The specific components of A. katsumadai responsible for these biological effects, however, are not known. In the present study, we investigated whether cardamonin (CDN), one of major principles of A. katsumadai, has suppressive effects on TXA2-induced scratching in mice. Scratching induced by U46619 (the TXA2 receptor agonist) at a dose of 10nmol/site was shown to be suppressed by CDN (0.1nmol-0.5nmol/site). Suppression of the U46619-induced scratching response by CDN was found to be unrelated to competition with the ligand at the TXA2 receptor, since CDN did not suppress [(3)H] SQ29548 (the TXA2 receptor antagonist) binding to TXA2 receptor. TXA2 receptor expression in A549, HaCaT, and SH-SY5Y cell lines was examined and determined to be significant in the A549 and SH-SY5Y cell lines. Further, binding of high molecular G protein Gh/transglutaminase-2 (Gh/Tgase-2) to TXA2 receptor was confirmed in the A549 and SH-SY5Y cells by co-immunoprecipitation. CDN suppressed the binding of TXA2 receptor with Gh/Tgase-2, which also acts as a G protein involved in TXA2 signaling. These results suggested that CDN suppresses TXA2 receptor agonist-induced scratching by suppressing TXA2 signaling, specifically via blocking of the binding of Gh/Tgase-2 to TXA2 receptor.
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Affiliation(s)
- Mi Kyung Park
- BK21PLUS R-FIND Team, College of Pharmacy, Dongguk University, Seoul 100-715, Republic of Korea
| | - Jin Kyu Choi
- College of Veterinary Medicine, Seoul National University, 1 Gwanak-ro, Gwanak-gu, 151-742 Seoul, Republic of Korea
| | - Hyun Ji Kim
- BK21PLUS R-FIND Team, College of Pharmacy, Dongguk University, Seoul 100-715, Republic of Korea
| | - Norimichi Nakahata
- Dept. of Cellular Signaling, Graduate School of Pharmaceutical Science, Tohoku University, Japan
| | - Kyung Min Lim
- College of Pharmacy, Ewha Womans University, Seoul 151-742, Republic of Korea
| | - Soo Youl Kim
- National Cancer Center, Goyang 410-769, Republic of Korea
| | - Chang Hoon Lee
- BK21PLUS R-FIND Team, College of Pharmacy, Dongguk University, Seoul 100-715, Republic of Korea.
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18
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Chakraborty R, Bhullar RP, Dakshinamurti S, Hwa J, Chelikani P. Inverse agonism of SQ 29,548 and Ramatroban on Thromboxane A2 receptor. PLoS One 2014; 9:e85937. [PMID: 24465800 PMCID: PMC3900440 DOI: 10.1371/journal.pone.0085937] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Accepted: 12/03/2013] [Indexed: 12/30/2022] Open
Abstract
G protein-coupled receptors (GPCRs) show some level of basal activity even in the absence of an agonist, a phenomenon referred to as constitutive activity. Such constitutive activity in GPCRs is known to have important pathophysiological roles in human disease. The thromboxane A2 receptor (TP) is a GPCR that promotes thrombosis in response to binding of the prostanoid, thromboxane A2. TP dysfunction is widely implicated in pathophysiological conditions such as bleeding disorders, hypertension and cardiovascular disease. Recently, we reported the characterization of a few constitutively active mutants (CAMs) in TP, including a genetic variant A160T. Using these CAMs as reporters, we now test the inverse agonist properties of known antagonists of TP, SQ 29,548, Ramatroban, L-670596 and Diclofenac, in HEK293T cells. Interestingly, SQ 29,548 reduced the basal activity of both, WT-TP and the CAMs while Ramatroban was able to reduce the basal activity of only the CAMs. Diclofenac and L-670596 showed no statistically significant reduction in basal activity of WT-TP or CAMs. To investigate the role of these compounds on human platelet function, we tested their effects on human megakaryocyte based system for platelet activation. Both SQ 29,548 and Ramatroban reduced the platelet hyperactivity of the A160T genetic variant. Taken together, our results suggest that SQ 29,548 and Ramatroban are inverse agonists for TP, whereas, L-670596 and Diclofenac are neutral antagonists. Our findings have important therapeutic applications in the treatment of TP mediated pathophysiological conditions.
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MESH Headings
- Amino Acid Substitution
- Blood Platelets/drug effects
- Blood Platelets/metabolism
- Bridged Bicyclo Compounds, Heterocyclic
- Calcium Signaling/drug effects
- Carbazoles/pharmacology
- Drug Evaluation, Preclinical
- Fatty Acids, Unsaturated
- HEK293 Cells
- Humans
- Hydrazines/pharmacology
- Inositol 1,4,5-Trisphosphate/metabolism
- Mutagenesis, Site-Directed
- Receptors, Thromboxane A2, Prostaglandin H2/agonists
- Receptors, Thromboxane A2, Prostaglandin H2/genetics
- Receptors, Thromboxane A2, Prostaglandin H2/metabolism
- Sulfonamides/pharmacology
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Affiliation(s)
- Raja Chakraborty
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, Canada
- Biology of Breathing Group- Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada
| | - Rajinder P. Bhullar
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Shyamala Dakshinamurti
- Departments of Pediatrics, Physiology, University of Manitoba, Winnipeg, Manitoba, Canada
- Biology of Breathing Group- Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada
| | - John Hwa
- Department of Internal Medicine (Cardiology), Cardiovascular Research Center, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Prashen Chelikani
- Department of Oral Biology, University of Manitoba, Winnipeg, Manitoba, Canada
- Departments of Pediatrics, Physiology, University of Manitoba, Winnipeg, Manitoba, Canada
- Biology of Breathing Group- Manitoba Institute of Child Health, Winnipeg, Manitoba, Canada
- * E-mail:
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Pydi SP, Bhullar RP, Chelikani P. Constitutive Activity of Bitter Taste Receptors (T2Rs). ADVANCES IN PHARMACOLOGY 2014; 70:303-26. [DOI: 10.1016/b978-0-12-417197-8.00010-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Prasad Pydi S, Singh N, Upadhyaya J, Pal Bhullar R, Chelikani P. The third intracellular loop plays a critical role in bitter taste receptor activation. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:231-6. [DOI: 10.1016/j.bbamem.2013.08.009] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2013] [Revised: 08/12/2013] [Accepted: 08/14/2013] [Indexed: 10/26/2022]
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High-level expression, purification and characterization of a constitutively active thromboxane A2 receptor polymorphic variant. PLoS One 2013; 8:e76481. [PMID: 24086743 PMCID: PMC3781061 DOI: 10.1371/journal.pone.0076481] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2012] [Accepted: 08/27/2013] [Indexed: 01/06/2023] Open
Abstract
G protein-coupled receptors (GPCRs) exhibit some level of basal signaling even in the absence of a bound agonist. This basal or constitutive signaling can have important pathophysiological roles. In the past few years, a number of high resolution crystal structures of GPCRs have been reported, including two crystal structures of constitutively active mutants (CAM) of the dim-light receptor, rhodopsin. The structural characterizations of CAMs are impeded by the lack of proper expression systems. The thromboxane A2 receptor (TP) is a GPCR that mediates vasoconstriction and promotes thrombosis in response to the binding of thromboxane. Here, we report on the expression and purification of a genetic variant and CAM in TP, namely A160T, using tetracycline-inducible HEK293S-TetR and HEK293S (GnTI¯)-TetR cell lines. Expression of the TP and the A160T genes in these mammalian cell lines resulted in a 4-fold increase in expression to a level of 15.8 ±0.3 pmol of receptor/mg of membrane protein. The receptors expressed in the HEK293S (GnTI(-))-TetR cell line showed homogeneous glycosylation. The functional yield of the receptors using a single step affinity purification was 45 µg/10⁶ cells. Temperature- dependent secondary structure changes of the purified TP and A160T receptors were characterized using circular dichroism (CD) spectropolarimetry. The CD spectra shows that the loss of activity or thermal sensitivity that was previously observed for the A160T mutant, is not owing to large unfolding of the protein but rather to a more subtle effect. This is the first study to report on the successful high-level expression, purification, and biophysical characterization of a naturally occurring, diffusible ligand activated GPCR CAM.
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