GRK1 and GRK7: Unique cellular distribution and widely different activities of opsin phosphorylation in the zebrafish rods and cones

Yasutaka Wada, Junichi Sugiyama, Toshiyuki Okano, Yoshitaka Fukada

Research output: Contribution to journalArticle

37 Citations (Scopus)

Abstract

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 Vmax 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.

Original languageEnglish
Pages (from-to)824-837
Number of pages14
JournalJournal of neurochemistry
Volume98
Issue number3
DOIs
Publication statusPublished - 2006 Aug 1
Externally publishedYes

Keywords

  • Cone
  • G protein-coupled receptor kinase
  • Phototransduction
  • Rhodopsin
  • Rod
  • Zebrafish

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

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