Cloning, chromosomal localization and functional expression of the gene encoding the alpha-subunit of the cGMP-gated channel in human cone photoreceptors.
Cyclic nucleotide-gated (CNG) ion channels serve as final targets of signal transduction in vertebrate photoreceptors. While the basic mechanisms of phototransduction are similar in rod and cone photoreceptors, both cell types express distinct sets of components of the transduction pathway. We report here the cloning of the cDNA encoding the alpha-subunit of the cGMP-gated channel of human cone photoreceptors. The open reading frame predicts a polypeptide of 694 amino acid residues with conserved functional parts and amino acid positions typical for the alpha-subunit of CNG-channels. Heterologous expression of the cDNA in Xenopus oocytes gave rise to cGMP-gated channel activity. Antiserum directed against the C-terminus of the bovine cone CNG channel alpha-subunit crossreacted specifically with the heterologously expressed polypeptide and stained cone photoreceptors and weakly also the outer plexiform layer in human retinal sections. Northern blot analysis detected a prominent mRNA species of approximately 3.8 kb in human retina. The entire gene spans approximately 30 kb of genomic sequence and is located on the pericentric band q11.2 of human chromosome 2. The gene is composed of seven exons, with introns located at positions which are preserved with respect to the human rod gene, indicating a common ancestral gene structure. RT-PCR analysis gave no evidence for alternatively spliced transcripts.
Wissinger
B
B
Molekulargenetisches Labor, Universitäts-Augenklinik Abteilung II, Tübingen, Germany.
Müller
F
F
Weyand
I
I
Schuffenhauer
S
S
Thanos
S
S
Kaupp
U B
UB
Zrenner
E
E
D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D002889:Chromosomes, Human, Pair 2; D003001:Cloning, Molecular; D003118:Color Perception / Q000235:genetics; D006152:Cyclic GMP / Q000502:physiology*; D054815:Cyclic Nucleotide-Gated Cation Channels; D018076:DNA, Complementary; D005091:Exons / Q000235:genetics; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D015640:Ion Channel Gating / Q000502:physiology; D007473:Ion Channels / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D009865:Oocytes / Q000502:physiology; D015183:Restriction Mapping; D017949:Retinal Cone Photoreceptor Cells / Q000737:chemistry* / Q000502:physiology; D017386:Sequence Homology, Amino Acid; D014981:Xenopus
D054815:Cyclic Nucleotide-Gated Cation Channels; D018076:DNA, Complementary; D007473:Ion Channels; D006152:Cyclic GMP