51
|
Westergren HU, Svedlund S, Momo RA, Blomster JI, Wåhlander K, Rehnström E, Greasley PJ, Fritsche-Danielson R, Oscarsson J, Gan LM. Insulin resistance, endothelial function, angiogenic factors and clinical outcome in non-diabetic patients with chest pain without myocardial perfusion defects. Cardiovasc Diabetol 2016; 15:36. [PMID: 26892461 PMCID: PMC4759743 DOI: 10.1186/s12933-016-0353-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2016] [Accepted: 02/09/2016] [Indexed: 12/24/2022] Open
Abstract
Background Patients with angina-like symptoms without myocardial perfusion scintigram (MPS)-verified abnormality may still be at risk for cardiovascular events. We hypothesized that insulin resistance could play a role in this population even without diagnosed diabetes. We further explored physiological and blood biomarkers, as well as global gene expression patterns that could be closely related to impaired glucose homeostasis to deepen our mechanistic understanding. Methods A total of 365 non-diabetic patients with suspected myocardial ischemia referred to MPS were enrolled and followed up regarding event-free survival with a median time of 5.1 years. All patients underwent endothelial function assessment by reactive hyperemic index (RHI) using EndoPAT and extensive biomarker analysis. Whole blood global gene expression pathway analysis was performed in a subset of patients. Results Homeostasis model assessment of insulin resistance (HOMA-IR) added independent prognostic value in patients without myocardial perfusion defects. In a multivariable analysis, HOMA-IR was inversely associated with low RHI. Furthermore, elevated HOMA-IR was associated with decreased levels of vascular endothelial growth factor D, stem cell factor and endocan as well as to increased level of interleukin-6. Global gene expression pathway analysis of whole blood cells showed that high HOMA-IR and impaired endothelial function were associated with upregulated pro-inflammatory pathways and down-regulated eukaryotic initiation factor-2 pathway. Conclusions Insulin resistance measured by HOMA-IR is associated with endothelial dysfunction and confers independent prognostic information in non-diabetic patients with chest pain without myocardial perfusion defects. Increased systemic pro-inflammatory state and decreased levels of pro-angiogenic vascular growth factors may be important underlying molecular mechanisms.
Collapse
Affiliation(s)
- Helena U Westergren
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden.
| | - Sara Svedlund
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden. .,Department of Clinical Physiology, Sahlgrenska University Hospital, Gothenburg, Sweden.
| | | | - Juuso I Blomster
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden. .,AstraZeneca R&D, Gothenburg, Sweden.
| | | | | | | | | | | | - Li-Ming Gan
- Department of Molecular and Clinical Medicine, Institute of Medicine, Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden. .,Department of Clinical Physiology, Sahlgrenska University Hospital, Gothenburg, Sweden. .,AstraZeneca R&D, Gothenburg, Sweden.
| |
Collapse
|
52
|
Walsh SK, Hepburn CY, Keown O, Åstrand A, Lindblom A, Ryberg E, Hjorth S, Leslie SJ, Greasley PJ, Wainwright CL. Pharmacological profiling of the hemodynamic effects of cannabinoid ligands: a combined in vitro and in vivo approach. Pharmacol Res Perspect 2015; 3:e00143. [PMID: 26236485 PMCID: PMC4492759 DOI: 10.1002/prp2.143] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2015] [Accepted: 03/14/2015] [Indexed: 11/24/2022] Open
Abstract
The receptors mediating the hemodynamic responses to cannabinoids are not clearly defined due to the multifarious pharmacology of many commonly used cannabinoid ligands. While both CB1 and TRPV1 receptors are implicated, G protein-coupled receptor 55 (GPR55) may also mediate some of the hemodynamic effects of several atypical cannabinoid ligands. The present studies attempted to unravel the pharmacology underlying the in vivo hemodynamic responses to ACEA (CB1 agonist), O-1602 (GPR55 agonist), AM251 (CB1 antagonist), and cannabidiol (CBD; GPR55 antagonist). Agonist and antagonist profiles of each ligand were determined by ligand-induced GTPγS binding in membrane preparations expressing rat and mouse CB1 and GPR55 receptors. Blood pressure responses to ACEA and O-1602 were recorded in anesthetized and conscious mice (wild type, CB1−/− and GPR55−/−) and rats in the absence and presence of AM251 and CBD. ACEA demonstrated GTPγS activation at both receptors, while O-1602 only activated GPR55. AM251 exhibited antagonist activity at CB1 and agonist activity at GPR55, while CBD demonstrated selective antagonist activity at GPR55. The depressor response to ACEA was blocked by AM251 and attenuated by CBD, while O-1602 did not induce a depressor response. AM251 caused a depressor response that was absent in GPR55−/− mice but enhanced by CBD, while CBD caused a small vasodepressor response that persisted in GPR55−/− mice. Our findings show that assessment of the pharmacological profile of receptor activation by cannabinoid ligands in in vitro studies alongside in vivo functional studies is essential to understand the role of cannabinoids in hemodynamic control.
Collapse
Affiliation(s)
- Sarah K Walsh
- Institute for Health & Wellbeing Research, Robert Gordon University Riverside East, Aberdeen, AB10 7GJ, United Kingdom
| | - Claire Y Hepburn
- Institute for Health & Wellbeing Research, Robert Gordon University Riverside East, Aberdeen, AB10 7GJ, United Kingdom
| | - Oliver Keown
- Institute for Health & Wellbeing Research, Robert Gordon University Riverside East, Aberdeen, AB10 7GJ, United Kingdom ; Cardiac Unit, Raigmore Hospital Old Perth Road, Inverness, IV2 3UJ, United Kingdom
| | - Annika Åstrand
- Cardiovascular & Metabolic Disease IMED, AstraZeneca R&D Mölndal, Sweden
| | - Anna Lindblom
- Cardiovascular & Metabolic Disease IMED, AstraZeneca R&D Mölndal, Sweden
| | - Erik Ryberg
- Cardiovascular & Metabolic Disease IMED, AstraZeneca R&D Mölndal, Sweden
| | - Stephan Hjorth
- Cardiovascular & Metabolic Disease IMED, AstraZeneca R&D Mölndal, Sweden
| | - Stephan J Leslie
- Cardiac Unit, Raigmore Hospital Old Perth Road, Inverness, IV2 3UJ, United Kingdom
| | - Peter J Greasley
- Cardiovascular & Metabolic Disease IMED, AstraZeneca R&D Mölndal, Sweden
| | - Cherry L Wainwright
- Institute for Health & Wellbeing Research, Robert Gordon University Riverside East, Aberdeen, AB10 7GJ, United Kingdom
| |
Collapse
|
53
|
Sundström L, Greasley PJ, Engberg S, Wallander M, Ryberg E. Succinate receptor GPR91, a Gα(i) coupled receptor that increases intracellular calcium concentrations through PLCβ. FEBS Lett 2013; 587:2399-404. [PMID: 23770096 DOI: 10.1016/j.febslet.2013.05.067] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 05/30/2013] [Accepted: 05/30/2013] [Indexed: 11/15/2022]
Abstract
Succinate has been reported as the endogenous ligand for GPR91. In this study, succinate was confirmed to activate GPR91 resulting in both 3'-5'-cyclic adenosine monophosphate (cAMP) inhibition and inositol phosphate formation in a pertussis toxin (PTX)-sensitive manner. GPR91 agonist-mediated effects detected using dynamic mass redistribution (DMR) were inhibited with PTX, edelfosine and U73122 demonstrating the importance of not only the Gαi pathway but also PLCβ. These results show that GPR91 when expressed in HEK293s cells couples exclusively through the Gαi pathway and acts through Gαi not only to inhibit cAMP production but also to increase intracellular Ca(2+) in an inositol phosphate dependent mechanism via PLCβ activation.
Collapse
|
54
|
Kogej T, Blomberg N, Greasley PJ, Mundt S, Vainio MJ, Schamberger J, Schmidt G, Hüser J. Big pharma screening collections: more of the same or unique libraries? The AstraZeneca-Bayer Pharma AG case. Drug Discov Today 2012; 18:1014-24. [PMID: 23127858 DOI: 10.1016/j.drudis.2012.10.011] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2012] [Revised: 09/24/2012] [Accepted: 10/26/2012] [Indexed: 11/18/2022]
Abstract
In this study, the screening collections of two major pharmaceutical companies (AstraZeneca and Bayer Pharma AG) have been compared using a 2D molecular fingerprint by a nearest neighborhood approach. Results revealed a low overlap between both collections in terms of compound identity and similarity. This emphasizes the value of screening multiple compound collections to expand the chemical space that can be accessed by high-throughput screening (HTS).
Collapse
Affiliation(s)
- Thierry Kogej
- Chemistry Innovation Centre/Discovery Sciences, AstraZeneca R&D Mölndal, SE-43183 Mölndal, Sweden.
| | | | | | | | | | | | | | | |
Collapse
|
55
|
Cohen-Yeshurun A, Trembovler V, Alexandrovich A, Ryberg E, Greasley PJ, Mechoulam R, Shohami E, Leker RR. N-arachidonoyl-L-serine is neuroprotective after traumatic brain injury by reducing apoptosis. J Cereb Blood Flow Metab 2011; 31:1768-77. [PMID: 21505478 PMCID: PMC3170948 DOI: 10.1038/jcbfm.2011.53] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
N-arachidonoyl-L-serine (AraS) is a brain component structurally related to the endocannabinoid family. We investigated the neuroprotective effects of AraS following closed head injury induced by weight drop onto the exposed fronto-parietal skull and the mechanisms involved. A single injection of AraS following injury led to a significant improvement in functional outcome, and to reduced edema and lesion volume compared with vehicle. Specific antagonists to CB2 receptors, transient receptor potential vanilloid 1 (TRPV1) or large conductance calcium-activated potassium (BK) channels reversed these effects. Specific binding assays did not indicate binding of AraS to the GPR55 cannabinoid receptor. N-arachidonoyl-L-serine blocked the attenuation in phosphorylated extracellular-signal-regulated kinase 1/2 (ERK) levels and led to an increase in pAkt in both the ipsilateral and contralateral cortices. Increased levels of the prosurvival factor Bcl-xL were evident 24 hours after injury in AraS-treated mice, followed by a 30% reduction in caspase-3 activity, measured 3 days after injury. Treatment with a CB2 antagonist, but not with a CB1 antagonist, reversed this effect. Our results suggest that administration of AraS leads to neuroprotection via ERK and Akt phosphorylation and induction of their downstream antiapoptotic pathways. These protective effects are related mostly to indirect signaling via the CB2R and TRPV1 channels but not through CB1 or GPR55 receptors.
Collapse
Affiliation(s)
- Ayelet Cohen-Yeshurun
- Department of Pharmacology, Institute of Drug Research, Medical Faculty, Hebrew University of Jerusalem, Jerusalem, Israel
| | | | | | | | | | | | | | | |
Collapse
|
56
|
Pertwee RG, Howlett AC, Abood ME, Alexander SPH, Di Marzo V, Elphick MR, Greasley PJ, Hansen HS, Kunos G, Mackie K, Mechoulam R, Ross RA. International Union of Basic and Clinical Pharmacology. LXXIX. Cannabinoid receptors and their ligands: beyond CB₁ and CB₂. Pharmacol Rev 2011; 62:588-631. [PMID: 21079038 DOI: 10.1124/pr.110.003004] [Citation(s) in RCA: 1164] [Impact Index Per Article: 89.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
There are at least two types of cannabinoid receptors (CB(1) and CB(2)). Ligands activating these G protein-coupled receptors (GPCRs) include the phytocannabinoid Δ(9)-tetrahydrocannabinol, numerous synthetic compounds, and endogenous compounds known as endocannabinoids. Cannabinoid receptor antagonists have also been developed. Some of these ligands activate or block one type of cannabinoid receptor more potently than the other type. This review summarizes current data indicating the extent to which cannabinoid receptor ligands undergo orthosteric or allosteric interactions with non-CB(1), non-CB(2) established GPCRs, deorphanized receptors such as GPR55, ligand-gated ion channels, transient receptor potential (TRP) channels, and other ion channels or peroxisome proliferator-activated nuclear receptors. From these data, it is clear that some ligands that interact similarly with CB(1) and/or CB(2) receptors are likely to display significantly different pharmacological profiles. The review also lists some criteria that any novel "CB(3)" cannabinoid receptor or channel should fulfil and concludes that these criteria are not currently met by any non-CB(1), non-CB(2) pharmacological receptor or channel. However, it does identify certain pharmacological targets that should be investigated further as potential CB(3) receptors or channels. These include TRP vanilloid 1, which possibly functions as an ionotropic cannabinoid receptor under physiological and/or pathological conditions, and some deorphanized GPCRs. Also discussed are 1) the ability of CB(1) receptors to form heteromeric complexes with certain other GPCRs, 2) phylogenetic relationships that exist between CB(1)/CB(2) receptors and other GPCRs, 3) evidence for the existence of several as-yet-uncharacterized non-CB(1), non-CB(2) cannabinoid receptors; and 4) current cannabinoid receptor nomenclature.
Collapse
Affiliation(s)
- R G Pertwee
- School of Medical Sciences, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen, Scotland, UK.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
57
|
Boström J, Olsson RI, Tholander J, Greasley PJ, Ryberg E, Nordberg H, Hjorth S, Cheng L. Novel thioamide derivatives as neutral CB1 receptor antagonists. Bioorg Med Chem Lett 2010; 20:479-82. [DOI: 10.1016/j.bmcl.2009.11.125] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2009] [Revised: 11/19/2009] [Accepted: 11/21/2009] [Indexed: 11/16/2022]
|
58
|
Whyte LS, Ryberg E, Sims NA, Ridge SA, Mackie K, Greasley PJ, Ross RA, Rogers MJ. The putative cannabinoid receptor GPR55 affects osteoclast function in vitro and bone mass in vivo. Proc Natl Acad Sci U S A 2009; 106:16511-6. [PMID: 19805329 PMCID: PMC2737440 DOI: 10.1073/pnas.0902743106] [Citation(s) in RCA: 234] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2009] [Indexed: 11/18/2022] Open
Abstract
GPR55 is a G protein-coupled receptor recently shown to be activated by certain cannabinoids and by lysophosphatidylinositol (LPI). However, the physiological role of GPR55 remains unknown. Given the recent finding that the cannabinoid receptors CB(1) and CB(2) affect bone metabolism, we examined the role of GPR55 in bone biology. GPR55 was expressed in human and mouse osteoclasts and osteoblasts; expression was higher in human osteoclasts than in macrophage progenitors. Although the GPR55 agonists O-1602 and LPI inhibited mouse osteoclast formation in vitro, these ligands stimulated mouse and human osteoclast polarization and resorption in vitro and caused activation of Rho and ERK1/2. These stimulatory effects on osteoclast function were attenuated in osteoclasts generated from GPR55(-/-) macrophages and by the GPR55 antagonist cannabidiol (CBD). Furthermore, treatment of mice with this non-psychoactive constituent of cannabis significantly reduced bone resorption in vivo. Consistent with the ability of GPR55 to suppress osteoclast formation but stimulate osteoclast function, histomorphometric and microcomputed tomographic analysis of the long bones from male GPR55(-/-) mice revealed increased numbers of morphologically inactive osteoclasts but a significant increase in the volume and thickness of trabecular bone and the presence of unresorbed cartilage. These data reveal a role of GPR55 in bone physiology by regulating osteoclast number and function. In addition, this study also brings to light an effect of both the endogenous ligand, LPI, on osteoclasts and of the cannabis constituent, CBD, on osteoclasts and bone turnover in vivo.
Collapse
MESH Headings
- Animals
- Animals, Newborn
- Bone Density
- Bone Resorption/prevention & control
- Bone and Bones/cytology
- Bone and Bones/metabolism
- Cannabidiol/pharmacology
- Cell Line, Tumor
- Cells, Cultured
- Dose-Response Relationship, Drug
- Female
- Fluorescent Antibody Technique
- Humans
- Lysophospholipids/pharmacology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Osteoblasts/cytology
- Osteoblasts/drug effects
- Osteoblasts/metabolism
- Osteoclasts/cytology
- Osteoclasts/drug effects
- Osteoclasts/metabolism
- Osteogenesis/drug effects
- Receptors, Cannabinoid/genetics
- Receptors, Cannabinoid/metabolism
- Receptors, G-Protein-Coupled/genetics
- Receptors, G-Protein-Coupled/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
Collapse
Affiliation(s)
- Lauren S. Whyte
- Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| | | | | | - Susan A. Ridge
- Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| | - Ken Mackie
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN 47401
| | | | - Ruth A. Ross
- Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| | - Michael J. Rogers
- Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, United Kingdom
| |
Collapse
|
59
|
VAN Giezen JJJ, Nilsson L, Berntsson P, Wissing BM, Giordanetto F, Tomlinson W, Greasley PJ. Ticagrelor binds to human P2Y(12) independently from ADP but antagonizes ADP-induced receptor signaling and platelet aggregation. J Thromb Haemost 2009; 7:1556-65. [PMID: 19552634 DOI: 10.1111/j.1538-7836.2009.03527.x] [Citation(s) in RCA: 210] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND P2Y(12) plays an important role in regulating platelet aggregation and function. This receptor is the primary target of thienopyridine antiplatelet agents, the active metabolites of which bind irreversibly to the receptor, and of newer agents that can directly and reversibly modulate receptor activity. OBJECTIVE To characterize the receptor biology of the first reversibly binding oral P2Y(12) antagonist, ticagrelor (AZD6140), a member of the new cyclopentyltriazolopyrimidine (CPTP) class currently in phase III development. METHODS Ticagrelor displayed apparent non-competitive or insurmountable antagonism of ADP-induced aggregation in human washed platelets. This was investigated using competition binding against [(3)H]ADP, [(33)P]2MeS-ADP and the investigational CPTP compound [(125)I]AZ11931285 at recombinant human P2Y(12). Functional receptor inhibition studies were performed using a GTPgammaS-binding assay, and further binding studies were performed using membranes prepared from washed human platelets. RESULTS Radioligand-binding studies demonstrated that ticagrelor binds potently and reversibly to human P2Y(12) with K(on) and K(off) of (1.1 +/- 0.2) x 10(-4) nm(-1) s(-1) and (8.7 +/- 1.4) x 10(-4) s(-1), respectively. Ticagrelor does not displace [(3)H]ADP from the receptor (K(i) > 10 mum) but binds competitively with [(33)P]2MeS-ADP (K(i) = 4.3 +/- 1.3 nm) and [(125)I]AZ11931285 (K(i) = 0.33 +/- 0.04 nm), and shows apparent non-competitive inhibition of ADP-induced signaling but competitive inhibition of 2MeS-ADP-induced signaling. Binding studies on membranes prepared from human washed platelets demonstrated similar non-competitive binding for ADP and ticagrelor. CONCLUSIONS These data indicate that P2Y(12) is targeted by ticagrelor via a mechanism that is non-competitive with ADP, suggesting the existence of an independent receptor-binding site for CPTPs.
Collapse
Affiliation(s)
- J J J VAN Giezen
- Department of BioScience, AstraZeneca R&D Mölndal, Mölndal, Sweden.
| | | | | | | | | | | | | |
Collapse
|
60
|
Abstract
Four years ago, the first acoustic droplet ejectors (ADEs) were launched on the market, providing a new generation of high-throughput noncontact liquid handlers that outclassed traditional contact instruments in almost every respect. This introduction of noncontact dispensing has triggered radical changes to the screening/compound management interface. Higher quality is achieved through greater accuracy and precision, whereas lower sample volumes can be used, and 1536 plate formats have become a reliable reality. Prior to the ADE instrument launch, 1536 assay-ready plate preparation was a high-effort enterprise requiring users to spend time developing liquid-handling methods along with daily fine-tuning of instruments to reach the desired level of performance. By overcoming the nanoliter dispensing hurdle and successfully transferring assays to high-density formats, a new dimension for cutting costs has emerged. Once the screening customer has adapted to this new world, the rules of supply can also change, with the traditional automated plate store no longer being necessary when the compound library can be stored in 1536 plates. Processing efficiency recently has been further supported by innovative new automation-friendly solutions such as plate desealers, prolonging the life span of working plate copies. Both cost and waste control have never had a higher profile, and noncontact dispensing contributes to these important areas. In some processes (e.g., when piercing septa), contact dispensing remains the best option, but cost control is still essential, and an innovative solution to minimize DMSO consumption from tip washing has had a big impact on consumable budget without compromising quality. ( Journal of Biomolecular Screening 2009:509-514)
Collapse
Affiliation(s)
| | - Hans Eriksson
- Department of Lead Generation, AstraZeneca R&D, Mölndal, Sweden
| | - Mattias Rohman
- Department of Lead Generation, AstraZeneca R&D, Mölndal, Sweden
| | | |
Collapse
|
61
|
Ryberg E, Larsson N, Sjögren S, Hjorth S, Hermansson NO, Leonova J, Elebring T, Nilsson K, Drmota T, Greasley PJ. The orphan receptor GPR55 is a novel cannabinoid receptor. Br J Pharmacol 2007; 152:1092-101. [PMID: 17876302 PMCID: PMC2095107 DOI: 10.1038/sj.bjp.0707460] [Citation(s) in RCA: 1101] [Impact Index Per Article: 64.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
BACKGROUND The endocannabinoid system functions through two well characterized receptor systems, the CB1 and CB2 receptors. Work by a number of groups in recent years has provided evidence that the system is more complicated and additional receptor types should exist to explain ligand activity in a number of physiological processes. EXPERIMENTAL APPROACH Cells transfected with the human cDNA for GPR55 were tested for their ability to bind and to mediate GTPgammaS binding by cannabinoid ligands. Using an antibody and peptide blocking approach, the nature of the G-protein coupling was determined and further demonstrated by measuring activity of downstream signalling pathways. KEY RESULTS We demonstrate that GPR55 binds to and is activated by the cannabinoid ligand CP55940. In addition endocannabinoids including anandamide and virodhamine activate GTPgammaS binding via GPR55 with nM potencies. Ligands such as cannabidiol and abnormal cannabidiol which exhibit no CB1 or CB2 activity and are believed to function at a novel cannabinoid receptor, also showed activity at GPR55. GPR55 couples to Galpha13 and can mediate activation of rhoA, cdc42 and rac1. CONCLUSIONS These data suggest that GPR55 is a novel cannabinoid receptor, and its ligand profile with respect to CB1 and CB2 described here will permit delineation of its physiological function(s).
Collapse
Affiliation(s)
- E Ryberg
- Department of Lead Generation, AstraZeneca R&D Mölndal, Sweden
| | - N Larsson
- Department of Lead Generation, AstraZeneca R&D Mölndal, Sweden
| | - S Sjögren
- Department of Medical Sciences, AstraZeneca R&D Mölndal, Sweden
| | - S Hjorth
- Department of Integrative PharmacologyAstraZeneca R&D Mölndal, Sweden
| | - N-O Hermansson
- Department of Lead Generation, AstraZeneca R&D Mölndal, Sweden
| | - J Leonova
- Department of Lead Generation, AstraZeneca R&D Mölndal, Sweden
| | - T Elebring
- Department of Medicinal Chemistry, AstraZeneca R&D Mölndal, Sweden
| | - K Nilsson
- Department of Medicinal Chemistry, AstraZeneca R&D Mölndal, Sweden
| | - T Drmota
- Department of Lead Generation, AstraZeneca R&D Mölndal, Sweden
| | - P J Greasley
- Department of Lead Generation, AstraZeneca R&D Mölndal, Sweden
- Author for correspondence:
| |
Collapse
|
62
|
Boström J, Berggren K, Elebring T, Greasley PJ, Wilstermann M. Scaffold hopping, synthesis and structure-activity relationships of 5,6-diaryl-pyrazine-2-amide derivatives: a novel series of CB1 receptor antagonists. Bioorg Med Chem 2007; 15:4077-84. [PMID: 17433696 DOI: 10.1016/j.bmc.2007.03.075] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2006] [Revised: 02/23/2007] [Accepted: 03/27/2007] [Indexed: 10/23/2022]
Abstract
A scaffold hopping approach has been exploited to design a novel class of cannabinoid (CB1) receptor antagonists for the treatment of obesity. On the basis of shape-complementarity and synthetic feasibility the central fragment, a methylpyrazole, in Rimonabant was replaced by a pyrazine. The synthesis and CB1 antagonistic activities of a new series of 5,6-diaryl-pyrazine-2-amide derivatives are described. Several compounds showed antagonist potency below 10nM for the CB1 receptor.
Collapse
Affiliation(s)
- Jonas Boström
- Lead Generation Department, AstraZeneca R&D Mölndal, S-431 83 Mölndal, Sweden.
| | | | | | | | | |
Collapse
|
63
|
Greasley PJ, Clapham JC. Inverse agonism or neutral antagonism at G-protein coupled receptors: A medicinal chemistry challenge worth pursuing? Eur J Pharmacol 2006; 553:1-9. [PMID: 17081515 DOI: 10.1016/j.ejphar.2006.09.032] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Revised: 09/08/2006] [Accepted: 09/11/2006] [Indexed: 11/15/2022]
Abstract
The identification of constitutive, or intrinsic, activity of G-protein coupled receptors has had major impact on receptor theory, the identification of agents that inhibit this ligand-independent receptor activity has led, in turn, to the concept of inverse agonism. It has subsequently emerged that the majority, around 85%, of all known G-protein coupled receptor antagonists are, in fact, inverse agonists. Agents that affect only ligand-dependent receptor activation, i.e. have no effect on constitutive receptor signalling, are termed neutral antagonists and turn out to be relatively rare in pharmacology. Is this relevant for medicinal chemistry? That question is difficult to answer with certainty because there has been little or no effort to understand the structure activity relationships of neutral antagonist vs. inverse agonist molecules. In this review, we suggest that these pharmacological differences may well be translated to differential effects in the whole animal and in medicine. We argue that having either option to inhibit a particular receptor may reveal differences in efficacy and tolerability thus increasing the potential value of a G-protein coupled receptor inhibitor programme. However, since inverse agonists appear to constitute a default inhibitor mode, a systematic survey of the structure activity relationships around what makes a neutral antagonist will be an essential first step towards this goal.
Collapse
Affiliation(s)
- Peter J Greasley
- Department of Molecular Pharmacology, AstraZeneca R&D Mölndal, Sweden
| | | |
Collapse
|
64
|
Ryberg E, Vu HK, Larsson N, Groblewski T, Hjorth S, Elebring T, Sjögren S, Greasley PJ. Identification and characterisation of a novel splice variant of the human CB1 receptor. FEBS Lett 2005; 579:259-64. [PMID: 15620723 DOI: 10.1016/j.febslet.2004.11.085] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2004] [Revised: 11/17/2004] [Accepted: 11/21/2004] [Indexed: 12/01/2022]
Abstract
Cannabinoid ligands are implicated in many physiological processes and to date two receptors have been identified. However, a growing body of evidence exists that suggests the presence of additional receptors. Whilst cloning the previously described hCB1a, we have identified a novel variant that we call hCB1b. Characterising these two splice variants demonstrates that they have a unique pharmacological profile and that their RNA's are expressed at low levels in a variety of tissues.
Collapse
Affiliation(s)
- Erik Ryberg
- Department of Molecular Pharmacology, AstraZeneca R&D, Mölndal, Sweden
| | | | | | | | | | | | | | | |
Collapse
|
65
|
Abstract
The choice of assay for high throughput screening (HTS) is of strategic importance to the successful identification of chemical entities that can be developed into drugs. During the past decade several technologies have emerged permitting large compound collections to be screened against biologically relevant models in a high throughput fashion. In this review, we summarise the technologies that are available for screening G-protein-coupled receptors (GPCRs) and discuss the issues that impact upon the choice of screening methodology.:
Collapse
Affiliation(s)
- Peter J Greasley
- Lead Discovery Sciences, Department of Molecular Pharmacology, AstraZeneca R&D, SE43183 Mölndal, Sweden.
| | - Frank P Jansen
- Lead Discovery Sciences, Department of Molecular Pharmacology, AstraZeneca R&D, SE43183 Mölndal, Sweden
| |
Collapse
|
66
|
Greasley PJ, Fanelli F, Rossier O, Abuin L, Cotecchia S. Mutagenesis and modelling of the alpha(1b)-adrenergic receptor highlight the role of the helix 3/helix 6 interface in receptor activation. Mol Pharmacol 2002; 61:1025-32. [PMID: 11961120 DOI: 10.1124/mol.61.5.1025] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Computer simulations on a new model of the alpha1b-adrenergic receptor based on the crystal structure of rhodopsin have been combined with experimental mutagenesis to investigate the role of residues in the cytosolic half of helix 6 in receptor activation. Our results support the hypothesis that a salt bridge between the highly conserved arginine (R143(3.50)) of the E/DRY motif of helix 3 and a conserved glutamate (E289(6.30)) on helix 6 constrains the alpha1b-AR in the inactive state. In fact, mutations of E289(6.30) that weakened the R143(3.50)-E289(6.30) interaction constitutively activated the receptor. The functional effect of mutating other amino acids on helix 6 (F286(6.27), A292(6.33), L296(6.37), V299(6.40,) V300(6.41), and F303(6.44)) correlates with the extent of their interaction with helix 3 and in particular with R143(3.50) of the E/DRY sequence.
Collapse
Affiliation(s)
- Peter J Greasley
- Institut de Pharmacologie et Toxicologie, Université de Lausanne, Lausanne, Switzerland
| | | | | | | | | |
Collapse
|
67
|
Björklöf K, Lundström K, Abuin L, Greasley PJ, Cotecchia S. Co- and posttranslational modification of the alpha(1B)-adrenergic receptor: effects on receptor expression and function. Biochemistry 2002; 41:4281-91. [PMID: 11914074 DOI: 10.1021/bi015790j] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have characterized the maturation, co- and posttranslational modifications, and functional properties of the alpha(1B)-adrenergic receptor (AR) expressed in different mammalian cells transfected using conventional approaches or the Semliki Forest virus system. We found that the alpha(1B)-AR undergoes N-linked glycosylation as demonstrated by its sensitivity to endoglycosidases and by the effect of tunicamycin on receptor maturation. Pulse-chase labeling experiments in BHK-21 cells demonstrate that the alpha(1B)-AR is synthesized as a 70 kDa core glycosylated precursor that is converted to the 90 kDa mature form of the receptor with a half-time of approximately 2 h. N-Linked glycosylation of the alpha(1B)-AR occurs at four asparagines on the N-terminus of the receptor. Mutations of the N-linked glycosylation sites did not have a significant effect on receptor function or expression. Surprisingly, receptor mutants lacking N-linked glycosylation migrated as heterogeneous bands in SDS-PAGE. Our findings demonstrate that N-linked glycosylation and phosphorylation, but not palmitoylation or O-linked glycosylation, contribute to the structural heterogeneity of the alpha(1B)-AR as it is observed in SDS-PAGE. The modifications found are similar in the different mammalian expression systems explored. Our findings indicate that the Semliki Forest virus system can provide large amounts of functional and fully glycosylated alpha(1B)-AR protein suitable for biochemical and structural studies. The results of this study contribute to elucidate the basic steps involved in the processing of G protein-coupled receptors as well as to optimize strategies for their overexpression.
Collapse
MESH Headings
- Amino Acid Sequence
- Animals
- Binding Sites
- Blotting, Western
- Cell Line
- Cell Membrane/metabolism
- Cricetinae
- DNA, Complementary/metabolism
- Electrophoresis, Polyacrylamide Gel
- Glycosylation
- Green Fluorescent Proteins
- Inositol Phosphates/metabolism
- Kinetics
- Luminescent Proteins/metabolism
- Microscopy, Fluorescence
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Mutation
- Palmitic Acids/chemistry
- Phosphorylation
- Precipitin Tests
- Protein Binding
- Protein Biosynthesis
- Protein Conformation
- Protein Processing, Post-Translational
- Receptors, Adrenergic, alpha/chemistry
- Receptors, Adrenergic, alpha/metabolism
- Recombinant Fusion Proteins/metabolism
- Semliki forest virus/metabolism
- Sequence Homology, Amino Acid
- Time Factors
- Transfection
- Tunicamycin/pharmacology
Collapse
Affiliation(s)
- Katja Björklöf
- Institut de Pharmacologie et Toxicologie, Université de Lausanne, 1005 Lausanne, Switzerland, and F. Hoffmann-La Roche Reasearch Laboratories, 4070 Basel, Switzerland
| | | | | | | | | |
Collapse
|
68
|
Greasley PJ, Fanelli F, Scheer A, Abuin L, Nenniger-Tosato M, DeBenedetti PG, Cotecchia S. Mutational and computational analysis of the alpha(1b)-adrenergic receptor. Involvement of basic and hydrophobic residues in receptor activation and G protein coupling. J Biol Chem 2001; 276:46485-94. [PMID: 11585821 DOI: 10.1074/jbc.m105791200] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
To investigate their role in receptor coupling to G(q), we mutated all basic amino acids and some conserved hydrophobic residues of the cytosolic surface of the alpha(1b)-adrenergic receptor (AR). The wild type and mutated receptors were expressed in COS-7 cells and characterized for their ligand binding properties and ability to increase inositol phosphate accumulation. The experimental results have been interpreted in the context of both an ab initio model of the alpha(1b)-AR and of a new homology model built on the recently solved crystal structure of rhodopsin. Among the twenty-three basic amino acids mutated only mutations of three, Arg(254) and Lys(258) in the third intracellular loop and Lys(291) at the cytosolic extension of helix 6, markedly impaired the receptor-mediated inositol phosphate production. Additionally, mutations of two conserved hydrophobic residues, Val(147) and Leu(151) in the second intracellular loop had significant effects on receptor function. The functional analysis of the receptor mutants in conjunction with the predictions of molecular modeling supports the hypothesis that Arg(254), Lys(258), as well as Leu(151) are directly involved in receptor-G protein interaction and/or receptor-mediated activation of the G protein. In contrast, the residues belonging to the cytosolic extensions of helices 3 and 6 play a predominant role in the activation process of the alpha(1b)-AR. These findings contribute to the delineation of the molecular determinants of the alpha(1b)-AR/G(q) interface.
Collapse
Affiliation(s)
- P J Greasley
- Institut de Pharmacologie et Toxicologie, Université de Lausanne, 1005 Lausanne, Switzerland
| | | | | | | | | | | | | |
Collapse
|
69
|
Hasler U, Greasley PJ, von Heijne G, Geering K. Determinants of topogenesis and glycosylation of type II membrane proteins. Analysis of Na,K-ATPase beta 1 AND beta 3 subunits by glycosylation mapping. J Biol Chem 2000; 275:29011-22. [PMID: 10887183 DOI: 10.1074/jbc.m002867200] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The structural and molecular determinants that govern the correct membrane insertion and folding of membrane proteins are still ill-defined. By following the addition of sugar chains to engineered glycosylation sites (glycosylation mapping) in Na,K-ATPase beta isoforms expressed in vitro and in Xenopus oocytes, in combination with biochemical techniques, we have defined the C-terminal end of the transmembrane domain of these type II proteins. N-terminal truncation and the removal of a single charged residue at the N-terminal start of the putative transmembrane domain influence the proper positioning of the transmembrane domain in the membrane as reflected by a repositioning of the transmembrane domain, the exposure of a putative cryptic signal peptidase cleavage site, and the production of protein species unable to insert into the membrane. Glycosylation mapping in vivo revealed that the degree of glycosylation at acceptor sites located close to the membrane increases with the time proteins spend in the endoplasmic reticulum. Furthermore, core sugars added to such acceptor sites cannot be processed to fully glycosylated species even when the protein is transported to the cell surface. Thus, the glycosylation mapping strategy applied in intact cells is a useful tool for the study of determinants for the correct membrane insertion of type II and probably other membrane proteins, as well as for the processing of sugar chains in glycoproteins.
Collapse
Affiliation(s)
- U Hasler
- Institut de Pharmacologie and Toxicologie de l'Université, 27 rue du Bugnon, CH-1005 Lausanne, Switzerland
| | | | | | | |
Collapse
|
70
|
Greasley PJ, Bonnard C, Amati B. Myc induces the nucleolin and BN51 genes: possible implications in ribosome biogenesis. Nucleic Acids Res 2000; 28:446-53. [PMID: 10606642 PMCID: PMC102507 DOI: 10.1093/nar/28.2.446] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/1999] [Revised: 11/11/1999] [Accepted: 11/11/1999] [Indexed: 01/26/2023] Open
Abstract
The c-Myc oncoprotein and its dimerization partner Max bind the DNA core consensus sequence CACGTG (E-box) and activate gene transcription. However, the low levels of induction have hindered the identification of novel Myc target genes by differential screening techniques. Here, we describe a computer-based pre-selection of candidate Myc/Max target genes, based on two restrictive criteria: an extended E-box consensus sequence for Myc/Max binding and the occurrence of this sequence within a potential genomic CpG island. Candidate genes selected by these criteria were evaluated experimentally for their response to Myc. Two Myc target genes are characterized here in detail. These encode nucleolin, an abundant nucleolar protein, and BN51, a co-factor of RNA polymerase III. Myc activates transcription of both genes via E-boxes located in their first introns, as seen for several well-characterized Myc targets. For both genes, mutation of the E-boxes abolishes transcriptional activation by Myc as well as repression by Mad1. In addition, the BN51 promoter is selectively activated by Myc and not by USF, another E-box-binding factor. Both nucleolin and BN51 are implicated in the maturation of ribosomal RNAs, albeit in different ways. We propose that Myc, via regulation of these and probably many other transcriptional targets, may be an important regulator of ribosome biogenesis.
Collapse
Affiliation(s)
- P J Greasley
- Cellular Growth Control Unit, Swiss Institute for Experimental Cancer Research (ISREC), 155 ch. des Boveresses, CH-1066 Epalinger, Switzerland
| | | | | |
Collapse
|
71
|
Thorne MR, Rees-Milton KJ, Greasley PJ, Gore MG. Bovine inositol monophosphatase: metal-binding interactions at two different sites. Biochem Soc Trans 1997; 25:39S. [PMID: 9056937 DOI: 10.1042/bst025039s] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Affiliation(s)
- M R Thorne
- Department of Biochemistry, University of Southampton, United Kingdom
| | | | | | | |
Collapse
|
72
|
Thorne MR, Greasley PJ, Gore MG. Bovine inositol monophosphatase: enzyme-metal-ion interactions studied by pre-equilibrium fluorescence spectroscopy. Biochem J 1996; 315 ( Pt 3):989-94. [PMID: 8645188 PMCID: PMC1217305 DOI: 10.1042/bj3150989] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Stopped-flow fluorescence spectroscopy has been used to determine the on-rate (kass) and the off-rate (kdiss) for the equilibrium between inositol monophosphatase and Mg2+ ions. The dissociation constant (Kd) for the equilibrium calculated from these constants suggests that the ions interact at site 1 on the enzyme with a Kd typically around 450 microM, close to values determined by equilibrium studies (270-300 microM). The affinity of this site on the wild-type enzyme for Mg2+ ions increases as the pH is increased. This is mediated almost entirely by change in the rate kdiss. A slow increase occurs in the fluorescence intensity of the pyrene-labelled enzyme after the initial, fast, increase in fluorescence caused by the binding of the Mg2+ ion. The rate of this change is independent of the concentration of the metal ion, implying that it may be a structural change in the enzyme-Mg2+ complex. Neither the fast nor the slow change in fluorescence intensity occurs when enzyme subjected to limited proteolysis by trypsin, which removes the N-terminal 36 residues, is mixed with Mg2+ ions. The data suggest that interaction with Mg2+ ions at a high-affinity site leads to a structural change in inositol monophosphatase. The data further confirm the importance of the presence of two metal ions in the structure/function of this enzyme, and show that the binding of the metal ions is not competitive with that of H+ ions and that the variation in Kd with pH is mediated almost totally by changes in kdiss.
Collapse
Affiliation(s)
- M R Thorne
- Department of Biochemistry, University of Southampton, UK
| | | | | |
Collapse
|
73
|
Abstract
Inositol monophosphatase can be modified at two sites by pyrene maleimide. These sites have been identified as Cys141 and Cys218. Stoichiometric addition of pyrene maleimide allows the sole modification of Cys218. The fluorescence of the pyrene moiety on the modified protein can be excited directly or by resonance energy transfer. The fluorescence properties of the pyrene group on Cys218 allows the interaction of ligands with the enzyme to be monitored. This feature has allowed dissociation constants for various metal ions to be determined and allowed the formation of various enzyme/ligand complexes to be observed. These studies have demonstrated that Mg2+ is required to support Pi binding and that Li+ interacts with a post-catalytic complex which is only formed in the forward reaction.
Collapse
Affiliation(s)
- P J Greasley
- Department of Biochemistry, University of Southampton, England
| | | | | |
Collapse
|
74
|
Abstract
Rapid equilibrium dialysis has been used to show that recombinant bovine brain inositol monophosphatase binds one equivalent of Pi per subunit of enzyme. Pi is only bound in the presence of Mg2+ ions. The dissociation constant for the equilibrium is approximately 50 microM. This value of Kd is independent of the concentration of the Mg2+ ions and of the presence or absence of Li+ ions. Lithium ions which inhibit the enzyme uncompetitively are not able to support the binding of the Pi to the enzyme. The observation that Pi only binds in the presence of Mg2+ ions supports similar conclusions made in experiments which studied the protection of the enzyme from proteolytic degradation and chemical modification.
Collapse
Affiliation(s)
- P J Greasley
- Department of Biochemistry, University of Southampton, UK
| | | |
Collapse
|
75
|
Rees-Milton KJ, Greasley PJ, Ragan CI, Gore MG. Bovine inositol monophosphatase. The identification of a histidine residue reactive to diethylpyrocarbonate. FEBS Lett 1993; 321:37-40. [PMID: 8385629 DOI: 10.1016/0014-5793(93)80616-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The inositol monophosphatase from bovine brain is inactivated by the histidine-specific reagent diethylpyrocarbonate. Using 4 mM reagent at pH 6.5, the reaction results in the modification of 3 equivalents of histidine per polypeptide chain. The loss of activity occurs at the same rate as the slowest reacting of these residues. Site directed mutagenesis studies have been used to generate a mutated enzyme species bearing a His-217-->Gln replacement and have shown that it is the modification of histidine 217 which results in the inactivation of the enzyme.
Collapse
|
76
|
Abstract
Bovine brain inositol monophosphatase is inactivated when trypsin catalyses the cleavage of a single peptide bond between Lys-36 and Ser-37. This proteolysis is closely followed by cleavage at two other sites in the protein between Lys-78 and Ser-79 and between Lys-156 and Ser-157 suggesting that all of these sites are exposed in the native conformation of the protein. All of these residues are predicted to lie at the ends of alpha helices. The most susceptible bond (Lys-36--Ser-37) is predicted to lie in a highly flexible region of the protein. Circular dichroism studies suggest that approximately 40% of the secondary structure of this protein is helical which is similar to that predicted by the algorithm of Garnier et al. [(1978) J. Mol. Biol. 120, 97-120].
Collapse
Affiliation(s)
- P J Greasley
- Dept. of Biochemistry, School of Biological Sciences, University of Southampton, Bassett Crescent East, UK
| | | | | | | |
Collapse
|
77
|
Greasley PJ, Gore MG, Ragan CI, Knowles MR, Gee NS, McAllister G. Bovine inositol monophosphatase; observation of the modification of a cysteine residue using protein fluorescence. Biochem Soc Trans 1992; 20:290S. [PMID: 1330777 DOI: 10.1042/bst020290s] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- P J Greasley
- Department of Biochemistry, University of Southampton
| | | | | | | | | | | |
Collapse
|
78
|
Gore MG, Greasley PJ, Ragan CI. Bovine inositol monophosphatase: development of a continuous fluorescence assay of enzyme activity. J Biochem Biophys Methods 1992; 25:55-60. [PMID: 1331221 DOI: 10.1016/0165-022x(92)90036-a] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
This paper describes a continuous assay for the enzyme inositol monophosphatase which has been developed using a new substrate, the fluorescent compound 4-methylumbelliferyl phosphate. The hydrolysis of the phosphate group from this compound can be readily detected by a resultant large red shift in the emission spectrum from 390-450 nm. The kinetic constants for the enzyme using this new substrate are described.
Collapse
Affiliation(s)
- M G Gore
- Dept. of Biochemistry, School of Biological Sciences, University of Southampton, UK
| | | | | |
Collapse
|
79
|
Knowles MR, Gee N, McAllister G, Ragan CI, Greasley PJ, Gore MG. Bovine inositol monophosphatase. Modification, identification and mutagenesis of reactive cysteine residues. Biochem J 1992; 285 ( Pt 2):461-8. [PMID: 1322134 PMCID: PMC1132810 DOI: 10.1042/bj2850461] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
1. Bovine inositol monophosphatase reacts with thiol reagents such as 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB), N-ethylmaleimide (NEM) and iodoacetic acid (IAA). 2. Modification by NEM results in nearly total loss of enzyme activity, whereas modification by IAA causes a slight increase in activity. 3. The loss of activity caused by NEM can be prevented by the inclusion of Ins1P, or better Ins1P and LiCl in the reaction mixture. 4. Two equivalents of p-nitrothiobenzoate (NTB2-) are released from the native enzyme on reaction with DTNB, and six equivalents of NTB2- are released from the SDS-denatured enzyme, suggesting that none of the six cysteine residues per molecule of enzyme is involved in intra- or inter-molecular disulphide bridges. 5. Both NEM and IAA react with two cysteine residues (residues 141 and 184 in the sequence) in a mutually exclusive manner. 6. NEM also reacts stoichiometrically with residue 218. 7. The NEM-induced loss of enzyme activity is accompanied by a 15% decrease in protein fluorescence. 8. A mutant of the enzyme which has an Ala-218 replacement for Cys-218 has full activity and is not sensitive to NEM, showing that the modification of this cysteine by NEM causes inhibition of the native protein by steric effects and that Cys-218 is not essential for activity.
Collapse
Affiliation(s)
- M R Knowles
- Neuroscience Research Centre, Merck Sharp and Dohme, Harlow, Essex, U.K
| | | | | | | | | | | |
Collapse
|