Structure of the human M2 muscarinic acetylcholine receptor bound to an antagonist (original) (raw)
Related papers
Distribution and function of the muscarinic receptor subtypes in the cardiovascular system
Physiological Genomics, 2018
Muscarinic acetylcholine receptors belong to the G protein-coupled receptor superfamily and are widely known to mediate numerous functions within the central and peripheral nervous system. Thus, they have become attractive therapeutic targets for various disorders. It has long been known that the parasympathetic system, governed by acetylcholine, plays an essential role in regulating cardiovascular function. Unfortunately, due to the lack of pharmacologic selectivity for any one muscarinic receptor, there was a minimal understanding of their distribution and function within this region. However, in recent years, advancements in research have led to the generation of knockout animal models, better antibodies, and more selective ligands enabling a more thorough understanding of the unique role muscarinic receptors play in the cardiovascular system. These advances have shown muscarinic receptor 2 is no longer the only functional subtype found within the heart and muscarinic receptors 1 and 3 mediate both dilation and constriction in the vasculature. Although muscarinic receptors 4 and 5 are still not well characterized in the cardiovascular system, the recent generation of knockout animal models will hopefully generate a better understanding of their function. This mini review aims to summarize recent findings and advances of muscarinic involvement in the cardiovascular system.
Muscarinic Receptors—Characterization, coupling and function
Pharmacology & Therapeutics, 1993
At least five muscarinic receptor genes have been cloned and expressed. Muscarinic receptors act via activation of G proteins: ml, m3 and m5 muscarinic receptors couple to stimulate phospholipase C, while m2 and m4 muscarinic receptors inhibit adenylyl cyclase. This review describes the localization, pharmacology and function of the five muscarinic receptor subtypes. The actions of muscarinic receptors on the heart, smooth muscle, glands and on neurons (both presynaptic and postsynaptic) in the autonomic nervous system and the central nervous system are analyzed in terms of subtypes, biochemical mechanisms and effects on ion channels, including K + channels and Ca 2+ channels. References
Muscarinic acetylcholine receptors: novel opportunities for drug development
Nature Reviews Drug Discovery, 2014
The muscarinic acetylcholine receptors (mAChRs) comprise a family of five related G protein-coupled receptors (GPCRs) belonging to the α-branch of class A GPCRs 1 . The mAChR family consists of five distinct subtypes, denoted M 1 to M 5 (and encoded by the genes CHRM1 to CHRM5). Three of these receptor subtypes (M 1 , M 3 and M 5 ) have been shown to couple to G proteins of the G q/11 family, whereas the remaining two subtypes (M 2 and M 4 ) preferentially signal through the G i/o family of G proteins 2 . The mAChRs have a central role in human physiology, regulating heart rate, smooth muscle contraction, glandular secretion and many fundamental functions of the central nervous system (CNS) 3 .
Functional M3 muscarinic acetylcholine receptors in mammalian hearts
British Journal of Pharmacology, 2004
In contrast to most peripheral tissues where multiple subtypes of muscarinic acetylcholine receptor (mAChR) coexist, with each of them playing its part in the orchestra of parasympathetic innervation, the myocardium has been traditionally considered to possess a single mAChR subtype. Although there is much evidence to support the notion that one receptor subtype (M2) orchestrates myocardial muscarinic transduction, there is emerging evidence that M1 and M3 receptors are also expressed and are of potential physiological, pathophysiological and pharmacological relevance. Clarifying this issue has a profound impact on our thinking about the cholinergic control of the heart function and disease and approaches to new drug development for the treatment of heart disease associated with parasympathetic dysfunction. This review article presents evidence for the presence of the M3 receptor subtype in the heart, and analyzes the controversial data from published pharmacological, functional and...
Partial functional reconstitution of the cardiac muscarinic cholinergic receptor
Journal of Biological Chemistry
~ Digitonin-solubilized cardiac muscarinic receptors were reconstituted by dialysis into human erythrocyte acceptor membranes which lack high-affinity muscarinic receptors. The number of receptors reconstituted was proportional to the quantity of soluble receptors added to the reconstitution system.
Biochemical Pharmacology, 1983
The affinities of atropine, scopolamine, 3-quinuclidinyl benzilate and twelve analogues of 3-quinuclidinyl benzilate were determined for the muscarinic acetylcholine receptor (m-AChR) using membrane preparations from caudate/putamen. The affinity constants thus obtained were compared with affinities previously reported for the m-AChR obtained from ventricular muscle. The affinities differed significantly for six of the compounds, the largest difference being 1Bfold. Neither solubilization nor variation of physiologically significant salts led to a significant change in the affinity of that compound. These results are interpreted as supporting the subclassification of the muscarinic acetylcholine receptor.
Journal of Molecular and Cellular Cardiology, 2013
M 2 muscarinic acetylcholine receptors modulate cardiac rhythm via regulation of the inward potassium current. To increase our understanding of M 2 receptor physiology we used Total Internal Reflection Fluorescence Microscopy to visualize individual receptors at the plasma membrane of transformed CHO M2 cells, a cardiac cell line (HL-1), primary cardiomyocytes and tissue slices from pre-and post-natal mice. Receptor expression levels between individual cells in dissociated cardiomyocytes and heart slices were highly variable and only 10% of murine cardiomyocytes expressed muscarinic receptors. M 2 receptors were evenly distributed across individual cells and their density in freshly isolated embryonic cardiomyocytes was~1 μm −2 , increasing at birth (to~3 μm −2 ) and decreasing back to~1 μm −2 after birth. M 2 receptors were primarily monomeric but formed reversible dimers. They diffused freely at the plasma membrane, moving approximately 4-times faster in heart slices than in cultured cardiomyocytes. Knowledge of receptor density and mobility has allowed receptor collision rate to be modeled by Monte Carlo simulations. Our estimated encounter rate of 5-10 collisions per second, may explain the latency between acetylcholine application and GIRK channel opening.
Naunyn-Schmiedeberg's Archives of Pharmacology, 1992
The non-selective labelled antagonist [3H]Nmethyl-scopolamine ([3H]NMS) was used to identify muscarinic acetylcholine receptors in rat duodenum smooth muscle membranes. Saturation and kinetic experiments revealed a binding site with a Ko-value of 0.2-0.3nmol/1 and a receptor concentration (Bmax) of 100 fmol/mg protein. The affinities of eight selective muscarinic antagonists were determined and compared with those at M1 (rat cerebral cortex), M2 (rat heart), M3 (rat submandibular gland) and M4 (data from D6rje et al. 1991) receptors. The "M2-selective" agent AF-DX 116, the group of "M2/M4-selective" compounds himbacine, AF-DX 384, AQ-RA 741 and methoctramine but also the "M3-selective" HHSiD showed affinities corresponding to M2 and/or M~ sites. The intermediate affinity of 4-DAMP favours a mixed Mz/M¢ receptor population mainly containing M2 receptors. Two compounds, pirenzepine and AQ-RA 741, displayed biphasic displacement curves indicating the presence of a small population of putative M 1 receptors. The rat duodenum antagonist binding profile, however, is not consistent with the presence of M3 receptors. We further demonstrate a concentration-dependent stimulation of [35S]GTP[S] binding to duodenal G proteins by the muscarinic agonist oxotremorine. Estimation of the binding parameters of GTP[S] in absence and presence of oxotremorine provided evidence for a catalytic activation of G proteins by agonist-activated muscarinic receptors in rat duodenal membranes and a strong signal amplification on the G protein level.
… , and vascular biology, 2004
Objective-Determining the role of specific muscarinic (M) receptor subtypes mediating responses to acetylcholine (ACh) has been limited by the specificity of pharmacological agents. Deletion of the gene for M 5 receptors abolished response to ACh in cerebral blood vessels but did not affect dilation of coronary arteries. The goal of this study was to determine the M receptors mediating responses to ACh in coronary circulation using mice deficient in M 2 or M 3 receptors (M 2 Ϫ/Ϫ, M 3 Ϫ/Ϫ, respectively). Methods and Results-Coronary arteries from respective wild-type, M 2 Ϫ/Ϫ, or M 3 Ϫ/Ϫ mice were isolated, cannulated, and pressurized. Diameter was measured with video microscopy. After preconstriction with U46619, ACh produced dose-dependent dilation of coronary arteries that was similar in wild-type and M 2 Ϫ/Ϫ mice. In contrast, dilation of coronary arteries from M 3 Ϫ/Ϫ mice to ACh was reduced by Ϸ80% compared with wild type. The residual response to ACh was atropine insensitive. Relaxation of coronary arteries to other stimuli was similar in M 2 Ϫ/Ϫ and M 3 Ϫ/Ϫ mice. Similar results were obtained in aorta rings. Conclusion-These findings provide the first direct evidence that relaxation to ACh in coronary circulation is mediated predominantly by activation of M 3 receptors.