This study is dedicated to honour the memory of our colleague Professor André Ménez, who was involved in the original design of this study.
Isolation and pharmacological characterization of AdTx1, a natural peptide displaying specific insurmountable antagonism of the α1A-adrenoceptor
Article first published online: 15 DEC 2009
Journal compilation © 2009 The British Pharmacological Society. No claim to original French government works
British Journal of Pharmacology
Volume 159, Issue 2, pages 316–325, January 2010
How to Cite
Quinton, L., Girard, E., Maiga, A., Rekik, M., Lluel, P., Masuyer, G., Larregola, M., Marquer, C., Ciolek, J., Magnin, T., Wagner, R., Molgó, J., Thai, R., Fruchart-Gaillard, C., Mourier, G., Chamot-Rooke, J., Ménez, A., Palea, S., Servent, D. and Gilles, N. (2010), Isolation and pharmacological characterization of AdTx1, a natural peptide displaying specific insurmountable antagonism of the α1A-adrenoceptor. British Journal of Pharmacology, 159: 316–325. doi: 10.1111/j.1476-5381.2009.00532.x
- Issue published online: 26 JAN 2010
- Article first published online: 15 DEC 2009
- Received 12 March 2009; revised 18 May 2009; accepted 3 August 2009
- binding experiments;
- snake toxin;
- venom fractionation;
- mass fragmentation;
- benign prostatic hyperplasia;
Background and purpose: Venoms are a rich source of ligands for ion channels, but very little is known about their capacity to modulate G-protein coupled receptor (GPCR) activity. We developed a strategy to identify novel toxins targeting GPCRs.
Experimental approach: We studied the interactions of mamba venom fractions with α1-adrenoceptors in binding experiments with 3H-prazosin. The active peptide (AdTx1) was sequenced by Edman degradation and mass spectrometry fragmentation. Its synthetic homologue was pharmacologically characterized by binding experiments using cloned receptors and by functional experiments on rabbit isolated prostatic smooth muscle.
Key results: AdTx1, a 65 amino-acid peptide stabilized by four disulphide bridges, belongs to the three-finger-fold peptide family. It has subnanomolar affinity (Ki= 0.35 nM) and high specificity for the human α1A-adrenoceptor subtype. We showed high selectivity and affinity (Kd= 0.6 nM) of radio-labelled AdTx1 in direct binding experiments and revealed a slow association constant (kon= 6 × 106·M−1·min−1) with an unusually stable α1A-adrenoceptor/AdTx1 complex (t1/2diss= 3.6 h). AdTx1 displayed potent insurmountable antagonism of phenylephrine's actions in vitro (rabbit isolated prostatic muscle) at concentrations of 10 to 100 nM.
Conclusions and implications: AdTx1 is the most specific and selective peptide inhibitor for the α1A-adrenoceptor identified to date. It displays insurmountable antagonism, acting as a potent relaxant of smooth muscle. Its peptidic nature can be exploited to develop new tools, as a radio-labelled-AdTx1 or a fluoro-labelled-AdTx1. Identification of AdTx1 thus offers new perspectives for developing new drugs for treating benign prostatic hyperplasia.