Phylogenetic shadowing of a histamine-gated chloride channel involved in insect vision.
A recently identified gene, hclA (synonym: ort), codes for an ionotrophic histamine receptor subunit in Drosophila melanogaster, and known hclA mutations lead to defects in the visual system, neurologic disorders and changed responsiveness to neurotoxins. To investigate whether this novel class of receptors is common across the Insecta, we analysed the genomes of 15 other insect species (Diptera, Hymenoptera, Coleoptera, Lepidoptera) and revealed orthologs of hclA in all of them. The predicted receptor domain of HCLA is extensively conserved (86-100% of identity) among the 16 proteins. Minor changes in the amino acid sequence that includes the putative transmembrane domains (TMs) 1-3 were found in non-drosophilid species only. Substantial amino acid variability was observed in the signal polypeptides, the intracellular loop domains and in TM4, in good accordance with known data on sequence variations in ligand-gated ion channels. Pairwise comparisons revealed three consensus sequences for N-glycosylation, conserved in HCLAs of all species studied, as well as a drosophilid-specific putative phosphorylation site. Real-time PCR analysis demonstrated that hclA-mRNA is abundant in heads of adult Drosophila. However, species- and sex-specific variations of the hclA expression levels were also observed.
Iovchev
Mladen
M
Institute of Molecular Biology, Department of Molecular Neurobiology, Sofia 1113, Bulgaria.
Boutanaev
Alexander
A
Ivanov
Ivaylo
I
Wolstenholme
Adrian
A
Nurminsky
Dmitry
D
Semenov
Eugene
E
D000595:Amino Acid Sequence; D000818:Animals; D018118:Chloride Channels / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000235:genetics / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D017344:Genes, Insect / Q000235:genetics*; D014644:Genetic Variation; D016678:Genome; D006632:Histamine / Q000494:pharmacology*; D007313:Insecta / Q000235:genetics / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects*; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014785:Vision, Ocular / Q000235:genetics / Q000502:physiology*
D018118:Chloride Channels; D006632:Histamine