Larger inhibition of visual pigment kinase in cones than in rods.
In the carp retina, visual pigment kinase, GRK1 (G-protein coupled receptor kinase 1) in rods and GRK7 in cones, is inhibited by a photoreceptor neuronal Ca(2+)-sensor protein, S-modulin (or recoverin) in rods and visinin (formerly named s26) in cones. Here, we compared Ca(2+)-dependent inhibition of GRK1 by S-modulin and that of GRK7 by visinin. First, the concentrations of S-modulin and visinin in the outer segment were estimated: the concentration of visinin (1.2 mM) was 20 times higher than that of S-modulin (53 μM). Based on the determined concentrations of the Ca(2+)-sensor proteins and the known dark Ca(2+) concentrations, we estimated that in situ Ca(2+)-dependent inhibition on GRK in cones would be 2.5 times higher than that in rods at the Ca(2+) concentration in the dark. Because GRK activity is approximately 100 times higher in cones than in rods [Proc. Natl Acad. Sci. USA 102 (2005) 21359], the range of Ca(2+)-dependent inhibition on GRK activity is more than 100 times wider in cones than in rods. The inhibitory effects of S-modulin and visinin on photoreceptor GRKs were indistinguishable, although these Ca(2+)-sensor proteins are expressed in a cell-type specific manner. The inhibition by these Ca(2+)-sensor proteins was slightly higher on GRK7 than GRK1 probably because of a characteristic specific to GRK7.
Arinobu
Daisuke
D
Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan.
Tachibanaki
Shuji
S
Kawamura
Satoru
S
D000465:Algorithms; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002347:Carps / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005455:Fluorescent Antibody Technique; D051606:G-Protein-Coupled Receptor Kinase 1 / Q000037:antagonists & inhibitors; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000494:pharmacology / Q000502:physiology; D010766:Phosphorylation; D051603:Recoverin / Q000096:biosynthesis / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology; D017949:Retinal Cone Photoreceptor Cells / Q000201:enzymology*; D017948:Retinal Rod Photoreceptor Cells / Q000201:enzymology*
D009419:Nerve Tissue Proteins; C045140:visinin; D051603:Recoverin; D051606:G-Protein-Coupled Receptor Kinase 1; D002118:Calcium