αD-Conotoxins in Species of the Eastern Pacific: The Case of Conus princeps from Mexico.

Arisaí C Hernández-Sámano,César V.F Batista,Fernando Zamudio,Estuardo López-Vera,Andrés Falcón,Manuel B Aguilar,Jesús Emilio Michel-Morfín,Michael C Jeziorski,Víctor Landa-Jaime

doi:10.3390/toxins11070405

Arisaí C Hernández-Sámano, César V.F Batista + Show 7 more

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https://doi.org/10.3390/toxins11070405

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Abstract

Conus snails produce venoms containing numerous peptides such as the α-conotoxins (α-CTXs), which are well-known nicotinic acetylcholine receptor (nAChR) antagonists. Thirty-eight chromatographic fractions from Conus princeps venom extract were isolated by RP-HPLC. The biological activities of 37 fractions (0.07 µg/µL) were assayed by two-electrode voltage clamp on human α7 nAChRs expressed in Xenopus laevis oocytes. Fractions F7 and F16 notably inhibited the response elicited by acetylcholine by 52.7 ± 15.2% and 59.6 ± 2.5%, respectively. Fraction F7 was purified, and an active peptide (F7-3) was isolated. Using a combination of Edman degradation, mass spectrometry, and RNASeq, we determined the sequence of peptide F7-3: AVKKTCIRSTOGSNWGRCCLTKMCHTLCCARSDCTCVYRSGKGHGCSCTS, with one hydroxyproline (O) and a free C-terminus. The average mass of this peptide, 10,735.54 Da, indicates that it is a homodimer of identical subunits, with 10 disulfide bonds in total. This peptide is clearly similar to αD-CTXs from species of the Indo-Pacific. Therefore, we called it αD-PiXXA. This toxin slowly and reversibly inhibited the ACh-induced response of the hα7 nAChR subtype, with an IC50 of 6.2 μM, and it does not affect the hα3β2 subtype at 6.5 μM.

Highlights

IntroductionThe nicotinic acetylcholine receptors (nAChRs) play important roles in neuronal signaling
The nicotinic acetylcholine receptors play important roles in neuronal signaling.They modulate the release of neurotransmitters, such as dopamine, norepinephrine, γ-amino butyric acid, and acetylcholine (ACh)
The homomeric α7 nicotinic acetylcholine receptor (nAChR) is one of the predominant nAChR subtypes in the central nervous system. This nAChR subtype is mainly distributed in the hippocampus and the cerebral cortex, regions associated with learning and memory mechanisms [3]

Summary

Introduction

The nicotinic acetylcholine receptors (nAChRs) play important roles in neuronal signaling They modulate the release of neurotransmitters, such as dopamine, norepinephrine, γ-amino butyric acid, and acetylcholine (ACh). The α7 nAChR is capable of inducing downstream signaling mechanisms in non-neuronal cells and is thought to be an ancestral form evolved in lower organisms that do not rely on fast excitatory mechanisms [4]. In humans, another common and predominant nAChR subtype is the α3β2 nAChR, which is expressed in the cerebellum, dorsal root ganglia, and spinal cord, and is involved in pain sensation [3,5]

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