Isolation and pharmacological characterization of α-Elapitoxin-Na1a, a novel short-chain postsynaptic neurotoxin from the venom of the Chinese Cobra (Naja atra)
| Autor: | Qing Liang, Tam Minh Huynh, Wayne C. Hodgson, Geoffrey K. Isbister |
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| Rok vydání: | 2020 |
| Předmět: |
0301 basic medicine
Naja Antivenom Neurotoxins Venom Pharmacology Cholinergic Agonists complex mixtures Biochemistry 03 medical and health sciences 0302 clinical medicine Postsynaptic potential Tandem Mass Spectrometry Chinese cobra medicine Neurotoxin Animals Humans Snake antivenom Amino Acid Sequence Elapid Venoms biology Dose-Response Relationship Drug Chemistry Neurotoxicity Synaptic Potentials biology.organism_classification medicine.disease Acetylcholine 030104 developmental biology 030220 oncology & carcinogenesis Carbachol Chickens Chromatography Liquid Muscle Contraction |
| Zdroj: | Biochemical pharmacology. 181 |
| ISSN: | 1873-2968 |
| Popis: | The Chinese Cobra (Naja atra) is an elapid snake of major medical importance in southern China. Although previous studies have shown that postsynaptic neurotoxins account for 11–23% of N. atra venom, envenomed patients do not display marked signs of neurotoxicity. We have previously shown that the lack of clinical neurotoxicity following snake envenoming by some species with ‘neurotoxic’ venoms may be related to the high prevalence of short-chain postsynaptic neurotoxins in these venoms. In this study, we describe the isolation and characterization of α-Elapitoxin-Na1a (α-EPTX-Na1a; 6949 Da), a short-chain postsynaptic neurotoxin, which accounts for approximately 9% of N. atra crude venom. α-EPTX-Na1a (30–300 nM) produced concentration-dependent inhibition of indirect-twitches, with a t90 value of 17 ± 2 min at 300 nM, and abolished contractile responses to exogenous acetylcholine and carbachol, in the chick biventer cervicis nerve-muscle preparation. The prior addition of either Chinese N. atra monovalent antivenom (0.3 U/ml) or Australian polyvalent snake antivenom (2.4 U/ml), prevented the in vitro neurotoxic effects of α-EPTX-Na1a (30 nM). Addition of each of these antivenoms at the t90 time point partially reversed the in vitro neurotoxicity caused by α-EPTX-Na1a (30 nM). The inhibition of indirect twitches by α-EPTX-Na1a (30 nM) was not reversed by repeatedly washing the tissue. α-EPTX-Na1a displayed pseudo-irreversible antagonism of concentration-response curves to carbachol with a pA2 value of 8.21. De novo protein sequencing of α-EPTX-Na1a revealed a typical short-chain postsynaptic neurotoxin profile of 62 amino acids which shared >98% amino acid sequence similarity with short-chain postsynaptic neurotoxins from other Naja species. When compared to short-chain neurotoxins isolated from cobras in China, α-EPTX-Na1a contained novel residues K47Q (i.e. lysine to glutamine), N48T (i.e. asparagine to threonine) and G49A (i.e. glycine to alanine). In conclusion, α-EPTX-Na1a is a potent, pseudo-irreversible, short-chain neurotoxin. The high prevalence of α-EPTX-Na1a in Chinese N. atra venom is likely to explain the mild neurotoxicity experienced by envenomed patients. |
| Databáze: | OpenAIRE |
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