Key result
Incubation of heart membranes with polymyxin B, a protein kinase C inhibitor, blocked the ATP/Mg2+-induced reduction in muscarinic acetylcholine receptors and increased their number by 74%.
Inhibition of protein kinase C by polymyxin B increases muscarinic acetylcholine receptor binding in heart membranes, suggesting a role for phosphorylation in receptor regulation.
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Supports PKC regulation of cardiac muscarinic receptors; hypothesis-generating for phosphorylation mechanisms, with no clinical implications yet.
The number of muscarinic acetylcholine receptors (MAChRs), as detected by binding of [3H]quinuclidinyl benzilate (QNB), was investigated under conditions which promote protein phosphorylation. Incubation of a crude heart membrane preparation in the presence of ATP/Mg2+ reduced MAChR number by 50%. Incubation with polymyxin B, an inhibitor of protein kinase C, blocked the effect of ATP/Mg2+ and increased MAChR number by 74%.
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Creazzo et al. (1988) studied this question. Polymyxin B vs. ATP/Mg2+ alone was evaluated on Number of muscarinic acetylcholine receptors (MAChRs). Incubation of heart membranes with polymyxin B, a protein kinase C inhibitor, blocked the ATP/Mg2+-induced reduction in muscarinic acetylcholine receptors and increased their number by 74%.
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