Orthosteric binding of ρ-Da1a, a natural peptide of snake venom interacting selectively with the α1A-adrenoceptor.
ρ-Da1a is a three-finger fold toxin from green mamba venom that is highly selective for the α1A-adrenoceptor. This toxin has atypical pharmacological properties, including incomplete inhibition of (3)H-prazosin or (125)I-HEAT binding and insurmountable antagonist action. We aimed to clarify its mode...
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2013
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oai:doaj.org-article:ea1b5de2a53b4c798bdec40a54b07f162021-11-18T09:02:59ZOrthosteric binding of ρ-Da1a, a natural peptide of snake venom interacting selectively with the α1A-adrenoceptor.1932-620310.1371/journal.pone.0068841https://doaj.org/article/ea1b5de2a53b4c798bdec40a54b07f162013-01-01T00:00:00Zhttps://www.ncbi.nlm.nih.gov/pmc/articles/pmid/23935897/pdf/?tool=EBIhttps://doaj.org/toc/1932-6203ρ-Da1a is a three-finger fold toxin from green mamba venom that is highly selective for the α1A-adrenoceptor. This toxin has atypical pharmacological properties, including incomplete inhibition of (3)H-prazosin or (125)I-HEAT binding and insurmountable antagonist action. We aimed to clarify its mode of action at the α1A-adrenoceptor. The affinity (pKi 9.26) and selectivity of ρ-Da1a for the α1A-adrenoceptor were confirmed by comparing binding to human adrenoceptors expressed in eukaryotic cells. Equilibrium and kinetic binding experiments were used to demonstrate that ρ-Da1a, prazosin and HEAT compete at the α1A-adrenoceptor. ρ-Da1a did not affect the dissociation kinetics of (3)H-prazosin or (125)I-HEAT, and the IC50 of ρ-Da1a, determined by competition experiments, increased linearly with the concentration of radioligands used, while the residual binding by ρ-Da1a remained stable. The effect of ρ-Da1a on agonist-stimulated Ca(2+) release was insurmountable in the presence of phenethylamine- or imidazoline-type agonists. Ten mutations in the orthosteric binding pocket of the α1A-adrenoceptor were evaluated for alterations in ρ-Da1a affinity. The D106(3.32)A and the S188(5.42)A/S192(5.46)A receptor mutations reduced toxin affinity moderately (6 and 7.6 times, respectively), while the F86(2.64)A, F288(6.51)A and F312(7.39)A mutations diminished it dramatically by 18- to 93-fold. In addition, residue F86(2.64) was identified as a key interaction point for (125)I-HEAT, as the variant F86(2.64)A induced a 23-fold reduction in HEAT affinity. Unlike the M1 muscarinic acetylcholine receptor toxin MT7, ρ-Da1a interacts with the human α1A-adrenoceptor orthosteric pocket and shares receptor interaction points with antagonist (F86(2.64), F288(6.51) and F312(7.39)) and agonist (F288(6.51) and F312(7.39)) ligands. Its selectivity for the α1A-adrenoceptor may result, at least partly, from its interaction with the residue F86(2.64), which appears to be important also for HEAT binding.Arhamatoulaye MaïgaJon MerlinElodie MarconCéline RougetMaud LarregolaBernard GilquinCarole Fruchart-GaillardEvelyne LajeunesseCharles MarchettiAlain LorphelinLaurent BellangerRoger J SummersDana S HutchinsonBronwyn A EvansDenis ServentNicolas GillesPublic Library of Science (PLoS)articleMedicineRScienceQENPLoS ONE, Vol 8, Iss 7, p e68841 (2013) |
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Medicine R Science Q Arhamatoulaye Maïga Jon Merlin Elodie Marcon Céline Rouget Maud Larregola Bernard Gilquin Carole Fruchart-Gaillard Evelyne Lajeunesse Charles Marchetti Alain Lorphelin Laurent Bellanger Roger J Summers Dana S Hutchinson Bronwyn A Evans Denis Servent Nicolas Gilles Orthosteric binding of ρ-Da1a, a natural peptide of snake venom interacting selectively with the α1A-adrenoceptor. |
| description |
ρ-Da1a is a three-finger fold toxin from green mamba venom that is highly selective for the α1A-adrenoceptor. This toxin has atypical pharmacological properties, including incomplete inhibition of (3)H-prazosin or (125)I-HEAT binding and insurmountable antagonist action. We aimed to clarify its mode of action at the α1A-adrenoceptor. The affinity (pKi 9.26) and selectivity of ρ-Da1a for the α1A-adrenoceptor were confirmed by comparing binding to human adrenoceptors expressed in eukaryotic cells. Equilibrium and kinetic binding experiments were used to demonstrate that ρ-Da1a, prazosin and HEAT compete at the α1A-adrenoceptor. ρ-Da1a did not affect the dissociation kinetics of (3)H-prazosin or (125)I-HEAT, and the IC50 of ρ-Da1a, determined by competition experiments, increased linearly with the concentration of radioligands used, while the residual binding by ρ-Da1a remained stable. The effect of ρ-Da1a on agonist-stimulated Ca(2+) release was insurmountable in the presence of phenethylamine- or imidazoline-type agonists. Ten mutations in the orthosteric binding pocket of the α1A-adrenoceptor were evaluated for alterations in ρ-Da1a affinity. The D106(3.32)A and the S188(5.42)A/S192(5.46)A receptor mutations reduced toxin affinity moderately (6 and 7.6 times, respectively), while the F86(2.64)A, F288(6.51)A and F312(7.39)A mutations diminished it dramatically by 18- to 93-fold. In addition, residue F86(2.64) was identified as a key interaction point for (125)I-HEAT, as the variant F86(2.64)A induced a 23-fold reduction in HEAT affinity. Unlike the M1 muscarinic acetylcholine receptor toxin MT7, ρ-Da1a interacts with the human α1A-adrenoceptor orthosteric pocket and shares receptor interaction points with antagonist (F86(2.64), F288(6.51) and F312(7.39)) and agonist (F288(6.51) and F312(7.39)) ligands. Its selectivity for the α1A-adrenoceptor may result, at least partly, from its interaction with the residue F86(2.64), which appears to be important also for HEAT binding. |
| format |
article |
| author |
Arhamatoulaye Maïga Jon Merlin Elodie Marcon Céline Rouget Maud Larregola Bernard Gilquin Carole Fruchart-Gaillard Evelyne Lajeunesse Charles Marchetti Alain Lorphelin Laurent Bellanger Roger J Summers Dana S Hutchinson Bronwyn A Evans Denis Servent Nicolas Gilles |
| author_facet |
Arhamatoulaye Maïga Jon Merlin Elodie Marcon Céline Rouget Maud Larregola Bernard Gilquin Carole Fruchart-Gaillard Evelyne Lajeunesse Charles Marchetti Alain Lorphelin Laurent Bellanger Roger J Summers Dana S Hutchinson Bronwyn A Evans Denis Servent Nicolas Gilles |
| author_sort |
Arhamatoulaye Maïga |
| title |
Orthosteric binding of ρ-Da1a, a natural peptide of snake venom interacting selectively with the α1A-adrenoceptor. |
| title_short |
Orthosteric binding of ρ-Da1a, a natural peptide of snake venom interacting selectively with the α1A-adrenoceptor. |
| title_full |
Orthosteric binding of ρ-Da1a, a natural peptide of snake venom interacting selectively with the α1A-adrenoceptor. |
| title_fullStr |
Orthosteric binding of ρ-Da1a, a natural peptide of snake venom interacting selectively with the α1A-adrenoceptor. |
| title_full_unstemmed |
Orthosteric binding of ρ-Da1a, a natural peptide of snake venom interacting selectively with the α1A-adrenoceptor. |
| title_sort |
orthosteric binding of ρ-da1a, a natural peptide of snake venom interacting selectively with the α1a-adrenoceptor. |
| publisher |
Public Library of Science (PLoS) |
| publishDate |
2013 |
| url |
https://doaj.org/article/ea1b5de2a53b4c798bdec40a54b07f16 |
| work_keys_str_mv |
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