Relationships among visual cycle retinoids, rhodopsin phosphorylation, and phototransduction in mouse eyes during light and dark adaptation.
Phosphorylation and regeneration of rhodopsin, the prototypical G-protein-coupled receptor, each can influence light and dark adaptation. To evaluate their relative contributions, we quantified rhodopsin, retinoids, phosphorylation, and photosensitivity in mice during a 90 min illumination followed by dark adaptation. During illumination, all-trans-retinyl esters and, to a lesser extent, all-trans-retinal accumulate and reach the steady state in <1 h. Each major phosphorylation site on rhodopsin reaches a steady state level of phosphorylation at a different time during illumination. The dominant factor that limits dark adaptation is isomerization of retinal. During dark adaptation, dephosphorylation of rhodopsin occurs in two phases. The faster phase corresponds to rapid dephosphorylation of regenerated rhodopsin present at the end of the illumination period. The slower phase corresponds to dephosphorylation of rhodopsin as it forms by regeneration. We conclude that rhodopsin phosphorylation has three physiological functions: it quenches phototransduction, reduces sensitivity during light adaptation, and suppresses bleached rhodopsin activity during dark adaptation.
Department of Biochemistry (Box 357350), University of Washington, Seattle, Washington 98195, USA.
Kimberly A
KA
Lee
Maria
M
Nawrot
Gregory G
GG
Garwin
John C
JC
Saari
James B
JB
Hurley
D000818:Animals; D003623:Dark Adaptation / Q000528:radiation effects*; D003624:Darkness; D004952:Esters / Q000737:chemistry / Q000378:metabolism; D005123:Eye / Q000166:cytology / Q000378:metabolism* / Q000528:radiation effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D009799:Ocular Physiological Phenomena / Q000528:radiation effects; D010766:Phosphorylation; D017948:Retinal Rod Photoreceptor Cells / Q000378:metabolism / Q000528:radiation effects; D012176:Retinoids / Q000378:metabolism*; D012243:Rhodopsin / Q000378:metabolism*; D013997:Time Factors; D014785:Vision, Ocular / Q000528:radiation effects*; D019745:cis-trans-Isomerases / Q000378:metabolism; D000099178:Retinoid Isomerohydrolase
D004952:Esters; D012176:Retinoids; D012243:Rhodopsin; D019745:cis-trans-Isomerases; D000099178:Retinoid Isomerohydrolase