Parietal-eye phototransduction components and their potential evolutionary implications.
The parietal-eye photoreceptor is unique because it has two antagonistic light signaling pathways in the same cell-a hyperpolarizing pathway maximally sensitive to blue light and a depolarizing pathway maximally sensitive to green light. Here, we report the molecular components of these two pathways. We found two opsins in the same cell: the blue-sensitive pinopsin and a previously unidentified green-sensitive opsin, which we name parietopsin. Signaling components included gustducin-alpha and Galphao, but not rod or cone transducin-alpha. Single-cell recordings demonstrated that Go mediates the depolarizing response. Gustducin-alpha resembles transducin-alpha functionally and likely mediates the hyperpolarizing response. The parietopsin-Go signaling pair provides clues about how rod and cone phototransduction might have evolved.
Su
Chih-Ying
CY
Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. chih-ying.su@yale.edu
Luo
Dong-Gen
DG
Terakita
Akihisa
A
Shichida
Yoshinori
Y
Liao
Hsi-Wen
HW
Kazmi
Manija A
MA
Sakmar
Thomas P
TP
Yau
King-Wai
KW
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D005075:Biological Evolution; D002460:Cell Line; D006152:Cyclic GMP / Q000378:metabolism; D044385:GTP-Binding Protein alpha Subunits / Q000235:genetics / Q000502:physiology; D006801:Humans; D008116:Lizards / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009799:Ocular Physiological Phenomena; D018408:Patch-Clamp Techniques; D020419:Photoreceptor Cells, Vertebrate / Q000737:chemistry / Q000502:physiology*; D017299:Rod Opsins / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D015293:Transducin / Q000235:genetics / Q000502:physiology; D014785:Vision, Ocular
D044385:GTP-Binding Protein alpha Subunits; D017299:Rod Opsins; D015106:3',5'-Cyclic-GMP Phosphodiesterases; D015293:Transducin; D006152:Cyclic GMP