Composition of mamba's venom is quite atypical and characterized by the presence of a large diversity of three-finger fold toxins (3FTx) interacting with various enzymes, receptors and ion channels. In particular, 3FTx from mambas display the unique property to interact with class A GPCRs, sometimes with a high affinity and selectivity. A screening of five of these toxins (MT1, MT3, MT7, ρ-Da1a and ρ-Da1b) on 29 different subtypes of bioaminergic receptors, using competition binding experiments, highlights the diversity of their pharmacological profiles. These toxins may display either absolute selectivity for one receptor subtype or a polypharmacological property for various bioaminergic receptors. Nevertheless, adrenoceptor is the main receptor family targeted by these toxins. Furthermore, a new receptor target was identified for 3FTx and toxins in general, the ρ-Da1b interacting competitively with the human dopamine D3 receptor in the micromolar range. This result expands the diversity of GPCRs targeted by toxins and more generally highlights the multipotent interacting property of 3FTx. Phylogenic analyzes of these toxins show that muscarinic, adrenergic and dopaminergic toxins may be pooled in one family called aminergic toxins, this family coming probably from a specific radiation of ligands present in mamba venoms.
Keywords: Aminergic toxins; GPCRs; Mamba venoms; Three-finger fold toxins.
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