Stereoselective inhibition of muscarinic receptor subtypes by the eight stereoisomers related to rociverine

Barbier, P; Renzetti, Ar; Turbanti, L; Bugno, Cristina Di; Fornai, Francesco; Vaglini, Francesca; Maggio, Roberto; Corsini, Giovanni

doi:10.1016/0922-4106(95)90024-1

Cited by 15 publications

(7 citation statements)

References 28 publications

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“…Normally, the binding of classical antagonists to muscarinic receptors is well described by the simple Langmuir isotherm, indicating a Hill coefficient close to unity (46). Low Hill coefficients are often attributed to either recognition by the antagonist of more than 1 receptor site or conformation, or to interaction of the antagonist with a second binding site on the receptor molecule, which causes a negative cooperative effect on the first site (30,47,48). None of these seems to apply in our situation.…”

Section: Resultsmentioning

confidence: 49%

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Receptor binding studies of soft anticholinergic agents

et al. 2001

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Section: Resultsmentioning

confidence: 49%

“…Cloned receptors have been used to determine the potency of novel compounds and to determine the subtype selectivity of antimuscarinic agents (30)(31)(32). Currently, several muscarinic receptor subtype-selective agents are in advanced clinical trials (33,34).…”

Section: Introductionmentioning

confidence: 99%

Receptor binding studies of soft anticholinergic agents

et al. 2001

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“…Cells were harvested ϳ72 h after transfection. Radioligand binding studies were carried out with membrane homogenates as described (17). CHO-K1 stable cell lines expressing the m3 and m3-short muscarinic receptors were obtained by transformation with plasmid DNAs containing the human m3 and m3-short receptors, in accordance with the procedure previously described (17).…”

Section: Preparation Of Mutantmentioning

confidence: 99%

Functional Role of the Third Cytoplasmic Loop in Muscarinic Receptor Dimerization

Maggio

Barbier

Fornai

et al. 1996

Journal of Biological Chemistry

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In the present study we tested the hypothesis that interaction between receptors might depend on the presence of a long third intracellular (i3) loop and that shortening this loop could impair the capability of receptors to form dimers. To address this question, we initially created short chimeric ␣ 2 adrenergic/m3 muscarinic receptors in which 196 amino acids were deleted from the i3 loop (␣ 2 /m3-short and m3/␣ 2 -short). Although co-transfection of ␣ 2 /m3 and m3/␣ 2 resulted in the appearance of specific binding, the co-expression of the two short constructs (␣ 2 /m3-short and m3/␣ 2 -short), either together or in combination, respectively, with m3/␣ 2 and ␣ 2 /m3 did not result in any detectable binding activity. In another set of experiments, a mutant m3 receptor, m3/m2(16aa), containing 16 amino acids of the m2 receptor sequence at the amino terminus of the third cytoplasmic loop, which was capable of binding muscarinic ligands but was virtually unable to stimulate phosphatidylinositol hydrolysis, was also mutated in the i3 loop, resulting in the m3/m2(16aa)-short receptor. Although co-transfection of m3/m2(16aa) with a truncated form of the m3 receptor (m3-trunc, containing an in frame stop codon after amino acid codon 272 of the rat m3 sequence) resulted in a considerable carbachol-stimulated phosphatidylinositol breakdown, the co-transfection of m3/m2(16aa)-short with the truncated form of the m3 receptor did not result in any recovery of the functional activity. Thus, these data suggest that intermolecular interaction between muscarinic receptors, involving the exchange of amino-terminal (containing TM domains I-V) and carboxyl-terminal (containing TM domains VI and VII) receptor fragments depends on the presence of a long i3 loop. One may speculate that when alternative forms of receptors with a different length of the i3 loop exist, they could have a different propensity to dimerize.Transmembrane receptors recognize and integrate external signals modifying the metabolism or the ionic equilibrium of the cell milieu. Muscarinic receptors belong to the G-proteincoupled class of receptors (2). Molecular cloning studies have revealed the existence of five structurally related muscarinic receptor proteins (m1-m5; Refs. 3 and 4). The five muscarinic receptors are predicted to be composed of seven hydrophobic transmembrane domains (TM domains I-VII) 1 connected by alternating cytoplasmic and extracellular loops, an extracellular amino-terminal domain and an intracellular carboxyl-terminal segment. These receptors couple to a varied group of effectors, including membrane-associated phospholipases, adenylate and guanylate cyclases, and ion channels (5-8). The third intracellular (i3) loop of these receptors confers specificity for G-protein coupling (9). Moreover, it has been suggested that this segment of the receptor is involved in the phenomenon of internalization and down-regulation (10 -12).In a previous article, Maggio et al. (13) showed that muscarinic receptors behave structurally in a fashion analog...

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“…Rociverine is an anticholinergic agent that exerts both antimuscarinic (atropine‐like) and direct antispasmodic (papaverine‐like) actions on smooth muscle, commonly used for the treatment of functional disorders of the gastroenteric, biliary and urinary tracts (20,21). The use of rociverine to speed up labor has been in midwifery practice for many decades in several countries, more on the basis of strongly advocated opinions and anecdotal information rather than on evidence‐based data.…”

Section: Introductionmentioning

confidence: 99%