Diversity of Voltage-Gated Sodium Channels in the Ascidian Larval Nervous System

Nagahora, Hitoshi; Okada, Toshiaki; Yahagi, Naoya; Chong, Jayhong A.; Mandel, Gail; Okamura, Yasushi

doi:10.1006/bbrc.2000.3290

Cited by 29 publications

(25 citation statements)

References 33 publications

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“…We sequenced the entire ORF of an mRNA transcript from Monosiga and partial transcripts from the two genes in Trichoplax, thereby demonstrating that these genes are expressed. The genes have a pore motif D/E/E/A that is intermediate between Ca v and Na v channels and is the same as some previously described invertebrate channels (21,23).…”

Section: Resultsmentioning

confidence: 94%

“…Because of the differences in the amino acids responsible for ion selectivity, and because proteins are likely to be under strong evolutionary constraints along every point of their evolution (20), it has been suggested that channels with intermediate pore sequences may exist in extant taxa (3,21), and some invertebrate channels have been proposed as representatives of these intermediate states (21,22). The phylogenetic relationships of these channels are not clear however (22)(23)(24), and no suggestion of an ancestral metazoan pore state has been put forth.…”

mentioning

confidence: 99%

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Evolution of sodium channels predates the origin of nervous systems in animals

Liebeskind¹,

Hillis²,

Zakon

2011

Proc. Natl. Acad. Sci. U.S.A.

136

151

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Voltage-dependent sodium channels are believed to have evolved from calcium channels at the origin of the nervous system. A search of the genome of a single-celled choanoflagellate (the sister group of animals) identified a gene that is homologous to animal sodium channels and has a putative ion selectivity filter intermediate between calcium and sodium channels. Searches of a wide variety of animal genomes, including representatives of each basal lineage, revealed that similar homologs were retained in most lineages. One of these, the Placozoa, does not possess a nervous system. We cloned and sequenced the full choanoflagellate channel and parts of two placozoan channels from mRNA, showing that they are expressed. Phylogenetic analysis clusters the genes for these channels with other known sodium channels. From this phylogeny we infer ancestral states of the ion selectivity filter and show that this state has been retained in the choanoflagellate and placozoan channels. We also identify key gene duplications and losses and show convergent amino acid replacements at important points along the animal lineage.eumetazoan | inactivation gate | pore motif

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Section: Resultsmentioning

confidence: 94%

mentioning

confidence: 99%

Evolution of sodium channels predates the origin of nervous systems in animals

Liebeskind¹,

Hillis²,

Zakon

2011

Proc. Natl. Acad. Sci. U.S.A.

136

151

View full text Add to dashboard Cite

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“…The flatworm BcNa v 1 channel also has a threonine in domain III as in VdNa v , but a histidine residue instead of aspartic acid in domain IV, giving rise to an EETH variant motif. In addition, an alanine instead of an aspartic acid is found in an ascidian sodium channel (HrNa v of Halocynthia roretzi) (30). Our experimental demonstration of TTX resistance in VdNa v 1a channels caused by sequence polymorphisms in the EEMD motif spurred our interest in examining the role in TTX sensitivity of the sequence polymorphisms identified in other invertebrate sodium channels.…”

Section: Ttx Resistance Conferred By Substitutions With Residues Corrmentioning

confidence: 90%

Functional Expression of an Arachnid Sodium Channel Reveals Residues Responsible for Tetrodotoxin Resistance in Invertebrate Sodium Channels

Nomura

Liu

et al. 2009

Journal of Biological Chemistry

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Tetrodotoxin (TTX) is a potent blocker of voltage-gated sodium channels, but not all sodium channels are equally sensitive to inhibition by TTX. The molecular basis of differential TTX sensitivity of mammalian sodium channels has been largely elucidated. In contrast, our knowledge about the sensitivity of invertebrate sodium channels to TTX remains poor, in part because of limited success in functional expression of these channels. In this study, we report the functional characterization in Xenopus oocytes of the first non-insect, invertebrate voltage-gated sodium channel from the varroa mite (Varroa destructor), an ecto-parasite of the honeybee. This arachnid sodium channel activates and inactivates rapidly with half-maximal activation at ؊18 mV and half-maximal fast inactivation at ؊29 mV. Interestingly, this arachnid channel showed surprising TTX resistance. TTX blocked this channel with an IC 50 of 1 M. Subsequent site-directed mutagenesis revealed two residues, Thr-1674 and Ser-1967, in the pore-forming region of domains III and IV, respectively, which were responsible for the observed resistance to inhibition by TTX. Furthermore, sequence comparison and additional amino acid substitutions suggested that sequence polymorphisms at these two positions could be a widespread mechanism for modulating TTX sensitivity of sodium channels in diverse invertebrates.

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“…The simplest organism express-390 ing a four-domain calcium channel is yeast, which has a single calcium channel gene (De Hertogh et al, 2002). To date, only multicellular organisms have been found to express four-domain sodium channels, including jellyfish, cnidarians, squid, and fruit fly (but not the roundworm Caenorhabditis elegans) (Loughney et al, 1989;Sato and Matsumoto, 1992;Anderson et al, 1993;Nagahora et al, 2000). These four-domain channels may have arisen by two cycles of gene duplication and fusion from an ancestral bacterial one-domain sodium channel.…”

Section: Molecular and Evolutionary Relationships In The Voltage-gatementioning

confidence: 99%

Overview of Molecular Relationships in the Voltage-Gated Ion Channel Superfamily

et al. 2005

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Diversity of Voltage-Gated Sodium Channels in the Ascidian Larval Nervous System

Cited by 29 publications

References 33 publications

Evolution of sodium channels predates the origin of nervous systems in animals

Evolution of sodium channels predates the origin of nervous systems in animals

Functional Expression of an Arachnid Sodium Channel Reveals Residues Responsible for Tetrodotoxin Resistance in Invertebrate Sodium Channels

Overview of Molecular Relationships in the Voltage-Gated Ion Channel Superfamily

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