Convergent Evolution of Sodium Ion Selectivity in Metazoan Neuronal Signaling

• DOI: 10.1016/j.celrep.2012.06.016
• Publication Date: 2012-07-26T15:15:42Z
• Authors: Maya Gur Barzilai; Adam M. Reitzel; Johanna E.M. Kraus; Dalia Gordon; Ulrich Technau; Michael Gurevitz; Yehu Moran
• Keywords: Neurons; 0301 basic medicine; Ion Transport; 572; Evolution; QH301-705.5; Molecular Sequence Data; Sodium; Molecular; Voltage-Gated Sodium Channels; 106023 Molecular biology; 106025 Neurobiology; Synaptic Transmission; Evolution, Molecular; 03 medical and health sciences; Sea Anemones; 106023 Molekularbiologie; Report; Animals; Calcium; Amino Acid Sequence; Biology (General); 106025 Neurobiologie

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.