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Parietal-Eye Phototransduction Components and Their Potential Evolutionary Implications
Chih-Ying Su,1*Dong-Gen Luo,1Akihisa Terakita,2Yoshinori Shichida,2Hsi-Wen Liao,1Manija A. Kazmi,3Thomas P. Sakmar,3King-Wai Yau1*
The parietal-eye photoreceptor is unique because it has twoantagonistic light signaling pathways in the same cellahyperpolarizing pathway maximally sensitive to blue light anda depolarizing pathway maximally sensitive to green light. Here,we report the molecular components of these two pathways. Wefound two opsins in the same cell: the blue-sensitive pinopsinand a previously unidentified green-sensitive opsin, which wename parietopsin. Signaling components included gustducin- andGo, but not rod or cone transducin-. Single-cell recordingsdemonstrated that Go mediates the depolarizing response. Gustducin-resembles transducin- functionally and likely mediates the hyperpolarizingresponse. The parietopsin-Go signaling pair provides clues abouthow rod and cone phototransduction might have evolved.
1 Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA. 2 Department of Biophysics, Graduate School of Science, Kyoto University and Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Kyoto 606-8502, Japan. 3 Laboratory of Molecular Biology and Biochemistry, Rockefeller University, 1230 York Avenue, New York, NY 10021, USA.
Present address: Department of Molecular, Cellular, and DevelopmentalBiology, Yale University, New Haven, CT 06520, USA.
* To whom correspondence should be addressed. E-mail: chih-ying.su{at}yale.edu (C.-Y.S.); kwyau{at}mail.jhmi.edu (K.-W.Y.)