ZFIN ID: ZDB-PUB-060623-22
GRK1 and GRK7: Unique cellular distribution and widely different activities of opsin phosphorylation in the zebrafish rods and cones
Wada, Y., Sugiyama, J., Okano, T., and Fukada, Y.
Date: 2006
Source: Journal of neurochemistry   98(3): 824-837 (Journal)
Registered Authors: Fukada, Yoshitaka
Keywords: none
MeSH Terms:
  • Animals
  • Cell Line
  • Eye Proteins/analysis
  • Eye Proteins/biosynthesis
  • Eye Proteins/genetics
  • G-Protein-Coupled Receptor Kinase 1/biosynthesis*
  • G-Protein-Coupled Receptor Kinase 1/genetics
  • G-Protein-Coupled Receptor Kinases
  • Humans
  • Molecular Sequence Data
  • Phosphorylation
  • Protein-Serine-Threonine Kinases/biosynthesis*
  • Protein-Serine-Threonine Kinases/genetics
  • Retinal Cone Photoreceptor Cells/chemistry
  • Retinal Cone Photoreceptor Cells/metabolism*
  • Retinal Rod Photoreceptor Cells/chemistry
  • Retinal Rod Photoreceptor Cells/metabolism*
  • Rod Opsins/chemistry
  • Rod Opsins/metabolism*
  • Zebrafish
  • Zebrafish Proteins/biosynthesis*
  • Zebrafish Proteins/genetics
PubMed: 16787417 Full text @ J. Neurochem.
Retinal cone cells exhibit distinctive photoresponse with a more restrained sensitivity to light and a more rapid shutoff kinetics than those of rods. To understand the molecular basis for these characteristics of cone responses, we focused on the opsin deactivation process initiated by G protein-coupled receptor kinase (GRK) 1 and GRK7 in the zebrafish, an animal model suitable for studies on retinal physiology and biochemistry. Screening of the ocular cDNAs identified two homologs for each of GRK1 (1A and 1B) and GRK7 (7-1 and 7-2), and they were classified into three GRK subfamilies, 1 A, 1B and 7 by phylogenetic analysis. In situ hybridization and immunohistochemical studies localized both GRK1B and GRK7-1 in the cone outer segments and GRK1A in the rod outer segments. The opsin/GRKs molar ratio was estimated to be 569 in the rod and 153 in the cone. The recombinant GRKs phosphorylated light-activated rhodopsin, and the V(max) value of the major cone subtype, GRK7-1, was 32-fold higher than that of the rod kinase, GRK1A. The reinforced activity of the cone kinase should provide a strengthened shutoff mechanism of the light-signaling in the cone and contribute to the characteristics of the cone responses by reducing signal amplification efficiency.