Protein toxins of the Echis coloratus viper venom directly activate TRPV1.
Biochim Biophys Acta Gen Subj 2017;
1861:615-623. [PMID:
28063984 DOI:
10.1016/j.bbagen.2017.01.004]
[Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2016] [Revised: 12/13/2016] [Accepted: 01/03/2017] [Indexed: 12/23/2022]
Abstract
BACKGROUND
Peptide and protein toxins are essential tools to dissect and probe the biology of their target receptors. Venoms target vital physiological processes to evoke pain. Snake venoms contain various factors with the ability to evoke, enhance and sustain pain sensation. While a number of venom-derived toxins were shown to directly target TRPV1 channels expressed on somatosensory nerve terminals to evoke pain response, such toxins were yet to be identified in snake venoms.
METHODS
We screened Echis coloratus saw-scaled viper venom's protein fractions isolated by reversed phase HPLC for their ability to activate TRPV1 channels. To this end, we employed heterologous systems to analyze TRPV1 and NGF pathways by imaging and electrophysiology, combined with molecular biology, biochemical, and pharmacological tools.
RESULTS
We identified TRPV1 activating proteins in the venom of Echis coloratus that produce a channel-dependent increase in intracellular calcium and outwardly rectifying currents in neurons and heterologous systems. Interestingly, channel activation was not mediated by any of its known toxin binding sites. Moreover, although NGF neurotropic activity was detected in this venom, TRPV1 activation was independent of NGF receptors.
CONCLUSIONS
Echis coloratus venom contains proteins with the ability to directly activate TRPV1. This activity is independent of the NGF pathway and is not mediated by known TRPV1 toxins' binding sites.
GENERAL SIGNIFICANCE
Our results could facilitate the discovery of new toxins targeting TRPV1 to enhance current understanding of this receptor activation mechanism. Furthermore, the findings of this study provide insight into the mechanism through which snakes' venom elicit pain.
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