Truxillic acid derivatives: High affinity, M2 selective allosteric modulators probes for mapping the muscarinic receptors

Abstract The membrane cholesterol was found to bind and modulate the function of several G-protein coupled receptors including muscarinic acetylcholine receptors. We investigated the binding of 20 steroidal compounds including neurosteroids and steroid hormones to muscarinic receptors. Corticosterone, progesterone, and some neurosteroids bound to muscarinic receptors with an affinity of 100 nM or greater. We established a structure-activity relationship for steroid-based allosteric modulators of muscarinic receptors. Further, we show that corticosterone and progesterone allosterically modulate the functional response of muscarinic receptors to acetylcholine at physiologically relevant concentrations. It can play a role in stress control or in pregnancy, conditions where levels of these hormones dramatically oscillate. Allosteric modulation of muscarinic receptors via the cholesterol-binding site represents a new pharmacological approach at diseases associated with altered cholinergic signalling.

Download Full-text

Exploring the binding mechanism of positive allosteric modulators in human metabotropic glutamate receptor 2 using molecular dynamics simulations

Physical Chemistry Chemical Physics ◽

10.1039/d1cp02157e ◽

2021 ◽

Author(s):

Panpan Wang ◽

Xiaonan Gao ◽

Ke Zhang ◽

Qinglan Pei ◽

Xiaobo Xu ◽

...

Keyword(s):

Molecular Dynamics ◽

Glutamate Receptor ◽

Metabotropic Glutamate Receptor ◽

Binding Mode ◽

Allosteric Modulators ◽

Binding Mechanism ◽

Metabotropic Glutamate ◽

High Affinity ◽

Dynamics Simulations ◽

High Electronegativity

Based on the binding mode and electrostatics, the features of high affinity PAMs were the reduced hydrophobicity with low electronegativity of R1, increased hydrophobicity with low electronegativity of R2 and with high electronegativity of linker.

Download Full-text

Characterization of muscarinic cholinergic receptors in cat tracheal gland cells

Journal of Applied Physiology ◽

10.1152/jappl.1986.61.4.1375 ◽

1986 ◽

Vol 61 (4) ◽

pp. 1375-1382 ◽

Cited By ~ 6

Author(s):

D. J. Culp ◽

M. G. Marin

Keyword(s):

Muscarinic Receptors ◽

Specific Binding ◽

Isolated Cells ◽

High Affinity ◽

Gland Cells ◽

Beta Adrenergic Agonists ◽

Muscarinic Cholinergic ◽

Dose Dependent ◽

Nanomolar Range

Studies of airway glands indicate a muscarinic cholinergic regulation of secretion. Because of the cellular complexity of the airways, receptor characterization in whole tissue is unfeasible. Therefore, we utilized homogenates of disaggregated gland cells isolated from cat trachea and the muscarinic antagonist [1–3H]quinuclidinyl benzilate ([3H]QNB) to characterize glandular muscarinic receptors. Receptors of isolated cells were functionally intact as assessed by carbachol (10(-4) M) stimulation of O2 consumption 86 +/- 6% (+/- SE, n = 20). Stimulation was dose dependent (mean effective concentration = 3.5 microM), inhibited by atropine [dissociation constant (KD) = 4.2 nM] but not phentolamine nor propranolol. Specific binding of [3H]QNB to cell homogenates was saturable, of high affinity (KD = 36 pM) and to a single population of receptors. Maximum binding was 58 fmol/10(6) cells or about 35,000 receptors per cell. Estimated affinities for muscarinic agents were in the micromolar range for agonists and nanomolar range for antagonists. Histamine, alpha-adrenergic, and beta-adrenergic agonists and antagonists did not inhibit specific binding. These results suggest that muscarinic receptors on tracheal gland cells are of high affinity and density.

Download Full-text

Development of cholinergic innervation and muscarinic receptor subtypes in piglet trachea

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1993.264.6.l606 ◽

1993 ◽

Vol 264 (6) ◽

pp. L606-L614 ◽

Cited By ~ 7

Author(s):

B. Haxhiu-Poskurica ◽

P. Ernsberger ◽

M. A. Haxhiu ◽

M. J. Miller ◽

L. Cattarossi ◽

...

Keyword(s):

Smooth Muscle ◽

G Protein ◽

Muscarinic Receptor ◽

Muscarinic Receptors ◽

Topical Application ◽

Vagal Stimulation ◽

Tracheal Smooth Muscle ◽

Cholinergic Innervation ◽

High Affinity

We studied physiological and pharmacological maturation of cholinergic innervation to tracheal smooth muscle in piglets at three ages: < 7 days, 2–3 wk, and 10 wk. Change in tracheal tension was measured in vivo from a tracheal segment and normalized for its size. Electrical vagal stimulation induced a significantly weaker increase in tracheal tension at < 7 days when compared with 2–3 and 10 wk. In vivo studies employing vagal stimulation before and after topical application of pirenzepine (an M1 muscarinic receptor blocker) and in vitro pharmacological studies evaluating the inhibition of [3H]quinuclidinyl benzilate (QNB) binding by pirenzepine demonstrated that immature M1-receptor function could not account for the weak tracheal smooth muscle responses in the first week. Topical application of the cholinergic agonist methacholine to the tracheal segment also induced a significantly weaker contractile response at < 7 days when compared with 2–3 and 10 wk. Total density of muscarinic receptors, as well as the M1 and M3 muscarinic subtypes, was not statistically different among > 7-day-old, 1- to 3-wk-old, and adult animals. Receptor binding studies in 1–3 wk and adult animals demonstrated biphasic dose-dependent inhibition of [3H]QNB binding in tracheal smooth muscle membranes by methacholine, with a high-affinity component dependent on the availability of G protein. These high-affinity muscarinic receptors coupled to G protein were absent in > 7-day-old piglets. We speculate that the weak tracheal smooth muscle contraction observed during the first week of life is in part secondary to immature G protein function.

Download Full-text