scholarly journals Toward an understanding of the structural basis of allostery in muscarinic acetylcholine receptors

2018 ◽  
Vol 150 (10) ◽  
pp. 1360-1372 ◽  
Author(s):  
Wessel A.C. Burger ◽  
Patrick M. Sexton ◽  
Arthur Christopoulos ◽  
David M. Thal
Keyword(s):  
Crystal Structures ◽  
Acetylcholine Receptors ◽  
Allosteric Modulation ◽  
Muscarinic Acetylcholine Receptors ◽  
Therapeutic Interventions ◽  
Structural Basis ◽  
Muscarinic Acetylcholine ◽  
Subtype Selectivity ◽  
Gpcr Activation ◽  
Allosteric Mechanisms

Recent breakthroughs and developments in structural biology have led to a spate of crystal structures for G protein–coupled receptors (GPCRs). This is the case for the muscarinic acetylcholine receptors (mAChRs) where inactive-state structures for four of the five subtypes and two active-state structures for one subtype are available. These mAChR crystal structures have provided new insights into receptor mechanisms, dynamics, and allosteric modulation. This is highly relevant to the mAChRs given that these receptors are an exemplar model system for the study of GPCR allostery. Allosteric mechanisms of the mAChRs are predominantly consistent with a two-state model, albeit with some notable recent exceptions. Herein, we discuss the mechanisms for positive and negative allosteric modulation at the mAChRs and compare and contrast these to evidence offered by pharmacological, biochemical, and computational approaches. This analysis provides insight into the fundamental pharmacological properties exhibited by GPCR allosteric modulators, such as enhanced subtype selectivity, probe dependence, and biased modulation while highlighting the current challenges that remain. Though complex, enhanced molecular understanding of allosteric mechanisms will have considerable influence on our understanding of GPCR activation and signaling and development of therapeutic interventions.

scholarly journals Role of Muscarinic Acetylcholine Receptors in Breast Cancer: Design of Metronomic Chemotherapy

2019 ◽  
Vol 14 (2) ◽  
pp. 91-100 ◽  
Author(s):  
María E. Sales ◽  
Alejandro J. Español ◽  
Agustina R. Salem ◽  
Paola M. Pulido ◽  
Y. Sanchez ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Progression ◽  
Acetylcholine Receptors ◽  
Metronomic Chemotherapy ◽  
Chemotherapeutic Agents ◽  
Muscarinic Acetylcholine Receptors ◽  
Therapeutic Interventions ◽  
Dependent Manner ◽  
Muscarinic Agonists ◽  
Muscarinic Acetylcholine

Background: muscarinic acetylcholine receptors (mAChRs) have attracted interest as targets for therapeutic interventions in different illnesses like Alzheimer´s disease, viral infections and different tumors. Regarding the latter, many authors have studied each subtype of mAChRs, which seem to be involved in the progression of distinct types of malignancies. Methods: We carefully revised research literature focused on mAChRs expression and signaling as well as in their involvement in cancer progression and treatment. The characteristics of screened papers were described using the mentioned conceptual framework. Results: Muscarinic antagonists and agonists have been assayed for the treatment of tumors established in lung, brain and breast with beneficial effects. We described an up-regulation of mAChRs in mammary tumors and the lack of expression in non-tumorigenic breast cells and normal mammary tissues. We and others demonstrated that muscarinic agonists can trigger anti-tumor actions in a dose-dependent manner on tumors originated in different organs like brain or breast. At pharmacological concentrations, they exert similar effects to traditional chemotherapeutic agents. Metronomic chemotherapy refers to the administration of anti-cancer drugs at low doses with short intervals among them, and it is a different regimen applied in cancer treatment reducing malignant growth and angiogenesis, and very low incidence of adverse effects. Conclusion: The usage of subthreshold concentrations of muscarinic agonists combined with conventional chemotherapeutic agents could be a promising tool for breast cancer therapy.

scholarly journals Allosteric Modulation of Muscarinic Acetylcholine Receptors

2007 ◽  
Vol 5 (3) ◽  
pp. 157-167 ◽  
Author(s):  
Karen Gregory ◽  
Patrick Sexton ◽  
Arthur Christopoulos
Keyword(s):  
Acetylcholine Receptors ◽  
Allosteric Modulation ◽  
Muscarinic Acetylcholine Receptors ◽  
Muscarinic Acetylcholine

scholarly journals Control of Cardiac Function in vivo with a Light-Regulated Drug

2018 ◽  
Author(s):  
Fabio Riefolo ◽  
Carlo Matera ◽  
Aida Garrido-Charles ◽  
Alexandre M. J. Gomila ◽  
Luca Agnetta ◽  
...  
Keyword(s):  
Cardiac Function ◽  
Mammalian Cells ◽  
Acetylcholine Receptors ◽  
Genetic Manipulation ◽  
Muscarinic Acetylcholine Receptors ◽  
Therapeutic Interventions ◽  
Muscarinic Acetylcholine ◽  
First Time

<p>Remote control of physiological functions with light offers the promise of unveiling their complex spatiotemporal dynamics in vivo, and enabling highly focalized therapeutic interventions with reduced systemic toxicity. Optogenetic methods have been implemented in the heart, but the need of genetic manipulation jeopardizes clinical applicability. This study aims at developing, testing and validating the first light-regulated drug with cardiac effects, in order to avoid the requirement of genetic manipulation offered by optogenetic methods. A M2 muscarinic acetylcholine receptors (mAChRs) light-regulated drug (PAI) was designed, synthesized and pharmacologically characterized. The design was based on the orthosteric mAChRs agonist Iperoxo, an allosteric M2 ligand, and a photoswitchable azobenzene linker. PAI can be reversibly photoisomerized between <i>cis</i> and <i>trans</i> configurations under ultraviolet (UV) and visible light, respectively, and it reversibly photoswitches the activity of M2 muscarinic acetylcholine receptors. We have evaluated <i>in vitro</i> photoresponses using a calcium imaging assay in genetically unmodified receptors overexpressed in mammalian cells. Furthermore, using this new chemical tool, we demonstrate for the first time photoregulation of cardiac function <i>in vivo</i> in wildtype frog tadpoles and in rats with a method that does not require genetic manipulation. Such a new approach may enable enhanced spatial and temporal selectivity for cardiovascular drugs.</p>

scholarly journals Structure-based discovery of selective positive allosteric modulators of antagonists for the M2 muscarinic acetylcholine receptor

2018 ◽  
Vol 115 (10) ◽  
pp. E2419-E2428 ◽  
Author(s):  
Magdalena Korczynska ◽  
Mary J. Clark ◽  
Celine Valant ◽  
Jun Xu ◽  
Ee Von Moo ◽  
...  
Keyword(s):  
Acetylcholine Receptors ◽  
Muscarinic Acetylcholine Receptor ◽  
Dissociation Rate ◽  
Muscarinic Acetylcholine Receptors ◽  
Neonatal Rat ◽  
Rat Cardiomyocytes ◽  
Muscarinic Acetylcholine ◽  
Adult Rat ◽  
Subtype Selectivity ◽  
Subtype Selective

Subtype-selective antagonists for muscarinic acetylcholine receptors (mAChRs) have long been elusive, owing to the highly conserved orthosteric binding site. However, allosteric sites of these receptors are less conserved, motivating the search for allosteric ligands that modulate agonists or antagonists to confer subtype selectivity. Accordingly, a 4.6 million-molecule library was docked against the structure of the prototypical M2 mAChR, seeking molecules that specifically stabilized antagonist binding. This led us to identify a positive allosteric modulator (PAM) that potentiated the antagonist N-methyl scopolamine (NMS). Structure-based optimization led to compound ’628, which enhanced binding of NMS, and the drug scopolamine itself, with a cooperativity factor (α) of 5.5 and a KB of 1.1 μM, while sparing the endogenous agonist acetylcholine. NMR spectral changes determined for methionine residues reflected changes in the allosteric network. Moreover, ’628 slowed the dissociation rate of NMS from the M2 mAChR by 50-fold, an effect not observed at the other four mAChR subtypes. The specific PAM effect of ’628 on NMS antagonism was conserved in functional assays, including agonist stimulation of [35S]GTPγS binding and ERK 1/2 phosphorylation. Importantly, the selective allostery between ’628 and NMS was retained in membranes from adult rat hypothalamus and in neonatal rat cardiomyocytes, supporting the physiological relevance of this PAM/antagonist approach. This study supports the feasibility of discovering PAMs that confer subtype selectivity to antagonists; molecules like ’628 can convert an armamentarium of potent but nonselective GPCR antagonist drugs into subtype-selective reagents, thus reducing their off-target effects.

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