Related Experiment Video

Updated: Jun 30, 2026

Two Peeling Methods for the Isolation of Photoreceptor Cell Compartments in the Mouse Retina for Protein Analysis
11:08

Two Peeling Methods for the Isolation of Photoreceptor Cell Compartments in the Mouse Retina for Protein Analysis

Published on: December 7, 2021

Phosphorylation of GRK7 by PKA in cone photoreceptor cells is regulated by light

Shoji Osawa1, Rebecca Jo, Ellen R Weiss

  • 1Department of Cell and Developmental Biology, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7090, USA.

Journal of Neurochemistry
|September 23, 2008
PubMed

Insights

G protein-coupled receptor kinases (GRKs) regulate vision. This study shows GRK7 is phosphorylated by cAMP-dependent protein kinase (PKA) in cone cells, a process crucial for light adaptation.

Area of Science:

  • Retinal physiology
  • Molecular biology
  • Phototransduction

Background:

  • Retina-specific G protein-coupled receptor kinases (GRK1 and GRK7) are crucial for photoresponse regulation and light adaptation through opsin phosphorylation.
  • Cyclic AMP-dependent protein kinase (PKA) has been shown in vitro to phosphorylate amino termini of GRK1 and GRK7.

Purpose of the Study:

  • To investigate the in vivo phosphorylation of GRK7 by PKA.
  • To determine the cellular localization and light-dependent regulation of GRK7 phosphorylation.

Main Methods:

  • Generation of a phospho-specific antibody recognizing GRK7 phosphorylated at Ser36 (a PKA site).
  • Immunohistochemical analysis using the phospho-specific antibody in various species (mammalian, amphibian, fish).
  • Investigation of GRK7 phosphorylation in Xenopus laevis under different light conditions.

Main Results:

  • GRK7 is phosphorylated in vivo at Ser36, the PKA site, and localized to cone inner and outer segments across diverse species.
  • In Xenopus laevis, GRK7 phosphorylation occurs under dark-adapted conditions and decreases upon light exposure.
  • Phosphorylation at Ser36 is conserved across 400 million years of evolution and is regulated by light.

Conclusions:

  • PKA-mediated phosphorylation of GRK7 is a conserved, light-dependent regulatory mechanism in cone photoreceptors.
  • This finding reveals a novel regulatory pathway for retinal GRKs by PKA, impacting cone photoresponse and adaptation.
  • Demonstrates a role for cAMP in regulating cone photoresponse proteins.

More Related Videos

Desensitization and Recovery of Crayfish Photoreceptors Upon Delivery of a Light Stimulus06:43

Desensitization and Recovery of Crayfish Photoreceptors Upon Delivery of a Light Stimulus

Published on: November 9, 2019

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development09:32

Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development

Published on: June 15, 2017

Related Concept Videos

G-Protein Gated Ion Channels01:21

G-Protein Gated Ion Channels

GPCRs are primarily responsible for our sense of smell, taste, and vision.  The binding of a sensory stimulus activates GPCR to stimulate effector proteins, many of which are ion channels in the sensory organs. GPCRs modulate the opening and closing of the target ion channels either directly by binding them, or by releasing second messengers that activate these channels. As ions move across the membrane, the membrane potential is altered, which induces an appropriate response.
Sensory organs,...
Photoreceptors and Visual Pathways01:22

Photoreceptors and Visual Pathways

At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
cAMP-dependent Protein Kinase Pathways01:25

cAMP-dependent Protein Kinase Pathways

Cyclic Adenosine Monophosphate (cAMP) is an essential second messenger that activates protein kinase A (PKA) and regulates various biological processes. A single epinephrine molecule binds to GPCR and activates several heterotrimeric G proteins, each stimulating multiple adenylyl cyclase, amplifying the signal, and synthesizing large numbers of cAMP molecules. Small changes in cAMP concentration affect PKA activity. The binding of four cAMP molecules induces a conformational change in PKA,...
Channel Rhodopsins01:11

Channel Rhodopsins

Most organisms use photoreceptors to sense and respond to light. Examples of photoreceptors include bacteriorhodopsins and bacteriophytochromes in some bacteria, phytochromes in plants, and rhodopsins in the photoreceptor cells of the vertebral retina. The light-sensitive property of these receptors is because of the bound chromophores, such as bilin in the phytochromes and retinal in the rhodopsins.
Rhodopsins belong to the family of cell surface proteins called G-protein coupled receptors,...
Cell Signaling in Plants01:25

Cell Signaling in Plants

Plant cells communicate to coordinate their cycle of growth, flowering and fruiting, and activities in roots, shoots, and leaves in response to the changing environmental conditions. Plant signaling is distinct from animal signaling. Plants primarily utilize enzyme-linked receptors, whereas the largest class of cell-surface receptors in animals are G-protein coupled receptors (GPCRs). Unlike animals, receptor tyrosine kinases are rare in plants. Instead, plants have a diverse class of...
Activation and Inactivation of G Proteins01:22

Activation and Inactivation of G Proteins

Heterotrimeric G proteins are guanine nucleotide-binding proteins. As the name suggests, heterotrimeric G proteins are composed of three subunits: alpha, beta, and gamma. They remain GDP-bound or GTP-bound inside the cells and switch between inactive/active states. The Gα subunit possesses the nucleotide-binding pocket that binds guanine nucleotides and switches between GDP or GTP-bound states. In contrast, the Gꞵ and Gγ subunits are always bound together with high affinity and are together...