Positive allosteric interactions on cardiac muscarinic receptors: effects of chemical modifications of disulphide and carboxyl groups
Language English Country Netherlands Media print
Document type Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.
Grant support
1 RO3 TW00171-01A1
FIC NIH HHS - United States
- MeSH
- Alcuronium pharmacology MeSH
- Allosteric Site MeSH
- Time Factors MeSH
- Dithiothreitol pharmacology MeSH
- Rats MeSH
- Rats, Wistar MeSH
- Radioligand Assay MeSH
- Receptors, Muscarinic drug effects MeSH
- Scopolamine pharmacology MeSH
- Heart drug effects MeSH
- Dose-Response Relationship, Drug MeSH
- Animals MeSH
- Check Tag
- Rats MeSH
- Male MeSH
- Female MeSH
- Animals MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
- Research Support, U.S. Gov't, P.H.S. MeSH
- Names of Substances
- Alcuronium MeSH
- Dithiothreitol MeSH
- Receptors, Muscarinic MeSH
- Scopolamine MeSH
Changes in the allosteric effects of alcuronium on rat cardiac muscarinic receptors were investigated after chemical modifications of S-S bonds or free carboxyl groups. In membranes pretreated with dithiothreitol, alcuronium lost its positive action on the binding of [3H]methyl-N-scopolamine while its inhibitory effect on radioligand dissociation was preserved. In membranes pretreated with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC), known to modify free carboxyl groups in proteins, the ability to bind [3H]methyl-N-scopolamine was preserved if the pretreatment had been performed in the presence of alcuronium, methyl-N-scopolamine or carbachol, while the positive cooperative effect of alcuronium on [3H]methyl-N-scopolamine binding was only preserved in membranes that had been exposed to EDC in the presence of alcuronium. Methyl-N-scopolamine, carbachol and alcuronium differed in their ability to protect (against EDC) the action of alcuronium on the rate of [3H]methyl-N-scopolamine dissociation. The results suggest that the disulphide bridge connecting the first two extracellular loops of muscarinic receptors is important for the positive allosteric action of alcuronium and that three carboxyl groups (presumably aspartate residues) are involved in receptor interactions with alcuronium and methyl-N-scopolamine. The first group is important for the effect of alcuronium on the affinity for methyl-N-scopolamine, the second is critical for the effect of alcuronium on the rate of methyl-N-scopolamine dissociation, and the third is critical for methyl-N-scopolamine binding. Presumably, the two charged nitrogens of alcuronium associate with the first and the second of the three groups involved.
References provided by Crossref.org
Allosteric Modulation of Muscarinic Acetylcholine Receptors
Activation of muscarinic acetylcholine receptors via their allosteric binding sites