Light stimulates a transducin-independent increase of cytoplasmic Ca2+ and suppression of current in cones from the zebrafish mutant nof.
Transducins couple visual pigments to cGMP hydrolysis, the only recognized phototransduction pathway in vertebrate photoreceptors. Here we describe a zebrafish mutant, no optokinetic response f(w21) (nof), with a nonsense mutation in the gene encoding the alpha subunit of cone transducin. Retinal morphology and levels of phototransduction enzymes are normal in nof retinas, but cone transducin is undetectable. Dark current in nof cones is also normal, but it is insensitive to moderate intensity light. The nof cones do respond, however, to bright light. These responses are produced by a light-stimulated, but transducin-independent, release of Ca2+ into the cone cytoplasm. Thus, in addition to stimulating transducin, light also independently induces release of Ca2+ into the photoreceptor cytoplasm.
Brockerhoff
Susan E
SE
Department of Biochemistry, University of Washington, Seattle, Washington 98195, USA. sbrocker@u.washington.edu
Rieke
Fred
F
Matthews
Hugh R
HR
Taylor
Michael R
MR
Kennedy
Breandan
B
Ankoudinova
Irina
I
Niemi
Gregory A
GA
Tucker
Chandra L
CL
Xiao
Ming
M
Cilluffo
Marianne C
MC
Fain
Gordon L
GL
Hurley
James B
JB
D000221:Adaptation, Ocular / Q000235:genetics / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006152:Cyclic GMP / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D006720:Homozygote; D017403:In Situ Hybridization; D007814:Larva; D008027:Light; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009928:Organ Specificity; D020161:Physical Chromosome Mapping; D017354:Point Mutation; D012333:RNA, Messenger / Q000096:biosynthesis; D017949:Retinal Cone Photoreceptor Cells / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D015398:Signal Transduction / Q000502:physiology; D015293:Transducin / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D014785:Vision, Ocular / Q000235:genetics / Q000502:physiology; D015027:Zebrafish
D012333:RNA, Messenger; D019204:GTP-Binding Proteins; D015293:Transducin; D006152:Cyclic GMP; D002118:Calcium