Background light produces a recoverin-dependent modulation of activated-rhodopsin lifetime in mouse rods.
The Ca(2+)-binding protein recoverin is thought to regulate rhodopsin kinase and to modulate the lifetime of the photoexcited state of rhodopsin (Rh*), the visual pigment of vertebrate rods. Recoverin has been postulated to inhibit the kinase in darkness, when Ca(2+) is high, and to be released from the disk membrane in light when Ca(2+) is low, accelerating rhodopsin phosphorylation and shortening the lifetime of Rh*. This proposal has remained controversial, in part because the normally rapid turnoff of Rh* has made Rh* modulation difficult to study in an intact rod. To circumvent this problem, we have made mice that underexpress rhodopsin kinase so that Rh* turnoff is rate limiting for the decay of the rod light response. We show that background light speeds the decay of Rh* turnoff, and that this no longer occurs in mice that have had recoverin knocked out. This is the first demonstration in an intact rod that light accelerates Rh* inactivation and that the Ca(2+)-binding protein recoverin may be required for the light-dependent modulation of Rh* lifetime.
Chen
Ching-Kang
CK
Department of Biochemistry and Molecular Biology, Virginia Commonwealth University, Richmond, Virginia 23298-0614, USA.
Woodruff
Michael L
ML
Chen
Frank S
FS
Chen
Desheng
D
Fain
Gordon L
GL
D000818:Animals; D002118:Calcium / Q000378:metabolism; D020013:Calcium Signaling / Q000502:physiology / Q000528:radiation effects; D051606:G-Protein-Coupled Receptor Kinase 1 / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D051603:Recoverin / Q000378:metabolism / Q000528:radiation effects*; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism* / Q000528:radiation effects*; D012243:Rhodopsin / Q000378:metabolism / Q000528:radiation effects*; D013997:Time Factors; D014785:Vision, Ocular / Q000502:physiology / Q000528:radiation effects*
D051603:Recoverin; D012243:Rhodopsin; D051606:G-Protein-Coupled Receptor Kinase 1; D002118:Calcium