title: Asymmetric divergence in structure and function of HCN channel duplicates in Ciona intestinalis.
abstract: Hyperpolarization-activated Cyclic Nucleotide (HCN) channels are voltage-gated cation channels and are critical for regulation of membrane potential in electrically active cells. To understand the evolution of these channels at the molecular level, we cloned and examined two of three HCN homologs of the urochordate Ciona intestinalis (ciHCNa and ciHCNb). ciHCNa is like mammalian HCNs in that it possesses similar electrical function and undergoes N-glycosylation of a sequon near the pore. ciHCNb lacks the pore-associated N-glycosylation sequon and is predictably not N-glycosylated, and it also has an unusual gating phenotype in which the channel's voltage-sensitive gate appears to close incompletely. Together with previous findings, the data support an evolutionary trajectory in which an HCN ancestor underwent lineage-specific duplication in Ciona, to yield one HCN with most features that are conserved with the mammalian HCNs and another HCN that has been uniquely altered.
authors.affiliation: Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada.
authors.forename: Heather A
authors.initials: HA
authors.lastname: Jackson
authors.forename: Andrew
authors.initials: A
authors.lastname: Hegle
authors.forename: Hamed
authors.initials: H
authors.lastname: Nazzari
authors.forename: Timothy
authors.initials: T
authors.lastname: Jegla
authors.forename: Eric A
authors.initials: EA
authors.lastname: Accili
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D016466:CHO Cells; D019070:Cell Lineage; D002938:Ciona intestinalis / Q000378:metabolism*; D003001:Cloning, Molecular; D006224:Cricetinae; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000737:chemistry* / Q000378:metabolism; D000939:Epitopes / Q000737:chemistry; D005260:Female; D006031:Glycosylation; D008969:Molecular Sequence Data; D009865:Oocytes / Q000166:cytology; D010641:Phenotype; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D054815:Cyclic Nucleotide-Gated Cation Channels; D000939:Epitopes