title: Convergent evolution of sodium ion selectivity in metazoan neuronal signaling.
abstract: Ion selectivity of metazoan voltage-gated Na(+) channels is critical for neuronal signaling and has long been attributed to a ring of four conserved amino acids that constitute the ion selectivity filter (SF) at the channel pore. Yet, in addition to channels with a preference for Ca(2+) ions, the expression and characterization of Na(+) channel homologs from the sea anemone Nematostella vectensis, a member of the early-branching metazoan phylum Cnidaria, revealed a sodium-selective channel bearing a noncanonical SF. Mutagenesis and physiological assays suggest that pore elements additional to the SF determine the preference for Na(+) in this channel. Phylogenetic analysis assigns the Nematostella Na(+)-selective channel to a channel group unique to Cnidaria, which diverged >540 million years ago from Ca(2+)-conducting Na(+) channel homologs. The identification of Cnidarian Na(+)-selective ion channels distinct from the channels of bilaterian animals indicates that selectivity for Na(+) in neuronal signaling emerged independently in these two animal lineages.
authors.affiliation: Department of Molecular Biology and Ecology of Plants, George S. Wise Faculty of Life Sciences, Tel-Aviv University, Israel.
authors.forename: Maya
authors.initials: M
authors.lastname: Gur Barzilai
authors.forename: Adam M
authors.initials: AM
authors.lastname: Reitzel
authors.forename: Johanna E M
authors.initials: JE
authors.lastname: Kraus
authors.forename: Dalia
authors.initials: D
authors.lastname: Gordon
authors.forename: Ulrich
authors.initials: U
authors.lastname: Technau
authors.forename: Michael
authors.initials: M
authors.lastname: Gurevitz
authors.forename: Yehu
authors.initials: Y
authors.lastname: Moran
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D019143:Evolution, Molecular; D017136:Ion Transport / Q000502:physiology; D008969:Molecular Sequence Data; D009474:Neurons / Q000378:metabolism; D012615:Sea Anemones / Q000235:genetics / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D009435:Synaptic Transmission / Q000502:physiology*; D061566:Voltage-Gated Sodium Channels / Q000235:genetics / Q000378:metabolism
chemical_list: D061566:Voltage-Gated Sodium Channels; D012964:Sodium; D002118:Calcium