β3-Adrenoceptor agonists have recently been introduced for the treatment of the overactive urinary bladder syndrome.
Their target, the β3-adrenoceptor, was discovered much later than β1- and β2-adrenoceptors and exhibits unique properties which make extrapolation of findings from the other two subtypes difficult and the β3-adrenoceptor a less understood subtype. This article discusses three aspects of β3-adrenoceptor pharmacology. Firstly, the ligand-recognition profile of β3-adrenoceptors differs considerably from that of the other two subtypes, i.e. many antagonists considered as non-selective actually are β3-sparing including propranolol or nadolol. Many agonists and antagonists classically considered as being 3-selective actually are not, including BRL 37,344 or SR 59,230. Moreover, the binding pocket apparently differs between the human and rodent β3-adrenoceptor, yielding considerable species differences in potency. Second, the expression pattern of β3-adrenoceptors is more restricted than that of other subtypes, particularly in humans; while this makes extrapolation of rodent findings to the human situation difficult, it may result in a smaller potential for side effects. The role of β3-adrenoceptor gene polymorphisms has insufficiently been explored and may differ even between primate species. Third, β3-adrenoceptors lack the phosphorylation sites involved in agonist-induced desensitization of the other two subtypes. Thus, they exhibit down-regulation and/or desensitization in only some but not other cell types and tissues. When desensitization occurs, it most often is at the level of mRNA or signaling molecule expression. All three of these factors have implications for future studies to better understand the β3-adrenoceptor as a novel pharmacological target.
Written by:
Cernecka H, Sand C, Michel MC. Are you the author?
Dept. of Molecular Pharmacology, University of Groningenn, Groningen, The Netherlands; University of Duisburg-Essen; Boehringer Ingelheim;
Reference: Mol Pharmacol. 2014 Jun 2. pii: mol.114.092817.
doi: 10.1124/mol.114.092817
PubMed Abstract
PMID: 24890609
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