Article

Evolutionary diversification of TTX-resistant sodium channels in a predator-prey interaction

Department of Biology, Utah State University, Logan, Utah 84322-5305, USA.
Nature (Impact Factor: 41.46). 05/2005; 434(7034):759-63. DOI: 10.1038/nature03444
Source: PubMed

ABSTRACT

Understanding the molecular genetic basis of adaptations provides incomparable insight into the genetic mechanisms by which evolutionary diversification takes place. Whether the evolution of common traits in different lineages proceeds by similar or unique mutations, and the degree to which phenotypic evolution is controlled by changes in gene regulation as opposed to gene function, are fundamental questions in evolutionary biology that require such an understanding of genetic mechanisms. Here we identify novel changes in the molecular structure of a sodium channel expressed in snake skeletal muscle, tsNa(V)1.4, that are responsible for differences in tetrodotoxin (TTX) resistance among garter snake populations coevolving with toxic newts. By the functional expression of tsNa(V)1.4, we show how differences in the amino-acid sequence of the channel affect TTX binding and impart different levels of resistance in four snake populations. These results indicate that the evolution of a physiological trait has occurred through a series of unique functional changes in a gene that is otherwise highly conserved among vertebrates.

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    • "are also venomous (see Weinstein et al., 2011). In addition, some North American garter snakes (Thamnophis spp., Natricidae) found in the Pacific Northwest have evolved a voltage-gated sodium channel with point mutations (Na V 1.4) that confers resistance to the potent sodium channel antagonist, tetrodotoxin (Geffeney et al., 2005). Thus, these could be considered potentially poisonous on ingestion as they might be accumulating toxin in their visceral organs such as occurs in other tetrodotoxin-resistant animals (e.g. "
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    ABSTRACT: The ancient perceptions of "venomous" and "poisonous snakes", as well as the Indo-European (IE) etymological origins of the term "venom" specifically associated with snakes are considered. Although several ancient cultures perceived snakes as symbols of fecundity and renewal, concurrent beliefs also associated venomous snakes with undesirable human characteristics or as portending non-propitious events. The respective IE roots of the terms "venom" and "poison", "wen" and "poi" refer to desire or the act of ingesting liquids. The origin of the term, "venom", is associated with polytheistic cults that emphasized attainment of desires sometimes assisted by "love potions", a term later interpolated with the word, "poison". Specific interpretation of the term, venom, has varied since its first probable use in the mid-Thirteenth Century. The definition of snake venom has long been contended, and interpretations have often reflected emphasis on the pharmacological or experimental toxicity of medically relevant snake venoms with less regard for the basic biological bases of these venoms, as well as those from snakes with no known medical significance. Several definitions of "snake venom" and their defining criteria are reviewed, and critical consideration is given to traditional criteria that might facilitate the future establishment of a biologically accurate definition. Copyright © 2015. Published by Elsevier Ltd.
    Full-text · Article · Jul 2015 · Toxicon
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    • "are also venomous (see Weinstein et al., 2011). In addition, some North American garter snakes (Thamnophis spp., Natricidae) found in the Pacific Northwest have evolved a voltage-gated sodium channel with point mutations (Na V 1.4) that confers resistance to the potent sodium channel antagonist, tetrodotoxin (Geffeney et al., 2005). Thus, these could be considered potentially poisonous on ingestion as they might be accumulating toxin in their visceral organs such as occurs in other tetrodotoxin-resistant animals (e.g. "

    Full-text · Article · Jul 2015
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    • "The DIII lysine in the Na v selectivity filter is also integral to the binding of TTX [20]. Another principal TTX binding determinant is a DI aromatic phenylalanine or tyrosine residue, located adjacent to the aspartate of the selectivity filter [21], and substitution with a non-aromatic amino acid at this position accounts for TTX-insensitivity in the majority of tetrodotoxic animals [22] [23] [24] [25] [26]. Significantly, both aphid channel sequences have an asparagine at this position (Fig. 2b). "
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    ABSTRACT: We describe the identification in aphids of a unique heterodimeric voltage-gated sodium channel which has an atypical ion selectivity filter and, unusually for insect channels, is highly insensitive to tetrodotoxin. We demonstrate that this channel has most likely arisen by adaptation (gene fission or duplication) of an invertebrate ancestral mono(hetero)meric channel. This is the only identifiable voltage-gated sodium channel homologue in the aphid genome(s), and the channel’s novel selectivity filter motif (DENS instead of the usual DEKA found in other eukaryotes) may result in a loss of sodium selectivity, as indicated experimentally in mutagenised Drosophila channels.
    Full-text · Article · Jan 2015 · FEBS Letters
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