The signaling pathway in photoresponses that may be mediated by visual pigments in erythrophores of Nile tilapia.
The ability to increase the synthesis or vary the distribution of pigment in response to light is an important feature of many pigment cells. Unlike other light-sensitive pigment cells, erythrophores of Nile tilapia change the direction of pigment migration depending on the peak wavelength of incident light: light near 365, 400 or 600 nm induces pigment aggregation, while dispersion occurs in response to light at 500 nm. How these phenomena are achieved is currently unknown. In the present study, the phototransduction involved in the pigment dispersion caused by light at 500 nm or the aggregation by light at 600 nm was examined, using pertussis toxin, cholera toxin, blockers of ion channels, various chemicals affecting serial steps of signaling pathways and membrane-permeable cAMP analog. The results show that light-induced bidirectional movements in tilapia erythrophores may be controlled by cytosolic cAMP levels via Gi- or Gs-type G proteins. In addition, RT-PCR demonstrated for the first time the expression of mRNAs encoding red and green opsins in tilapia fins, only where erythrophores exist. Here, we suggest that multiple cone-type visual pigments may be present in the erythrophores, and that unique cascades in which such opsins couple to Gi or Gs-type G proteins are involved in the photoresponses in these pigment cells. Thus, tilapia erythrophore system seems to be a nice model for understanding the photoresponses of cells other than visual cells.
Ban
Eiko
E
Department of Biomolecular Science, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan.
Kasai
Akiko
A
Sato
Masako
M
Yokozeki
Akemi
A
Hisatomi
Osamu
O
Oshima
Noriko
N
D000818:Animals; D002478:Cells, Cultured; D002772:Cholera Toxin / Q000494:pharmacology; D002856:Chromatophores / Q000187:drug effects / Q000378:metabolism* / Q000528:radiation effects; D023681:Cichlids; D005576:Colforsin / Q000494:pharmacology; D003470:Culture Media; D000242:Cyclic AMP / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D008027:Light; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D012168:Retinal Pigments / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D017299:Rod Opsins / Q000235:genetics / Q000378:metabolism; D013806:Theophylline / Q000494:pharmacology; D013997:Time Factors; D014785:Vision, Ocular / Q000187:drug effects
D003470:Culture Media; D004791:Enzyme Inhibitors; D012333:RNA, Messenger; D012168:Retinal Pigments; D017299:Rod Opsins; C095855:long-wavelength opsin; C095854:middle-wavelength opsin; D005576:Colforsin; D002772:Cholera Toxin; D013806:Theophylline; D000242:Cyclic AMP