Photoreceptor light-adaptation mediated by S-modulin, a member of a possible regulatory protein family of protein phosphorylation in signal transduction.
In vertebrate retinal photoreceptors, cytoplasmic [Ca2+] decreases upon exposure to light. A Ca(2+)-binding protein, S-modulin, detects this [Ca2+] decrease and reduces the light-sensitivity of the cell to induce light-adaptation. The reduction of the sensitivity is attained by disinhibition or facilitation of rhodopsin phosphorylation, a quenching mechanism of light-activated rhodopsin. S-modulin-like proteins are found in the brain as well. Several of these proteins show similar S-modulin effects, suggesting that these proteins also participate in the regulation of protein phosphorylation in the signal transduction in their host cells.
Kawamura
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Department of Physiology, Keio University School of Medicine, Tokyo, Japan.
D000222:Adaptation, Physiological; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000502:physiology*; D005136:Eye Proteins; D051597:Hippocalcin; D006801:Humans; D008027:Light; D008074:Lipoproteins; D009419:Nerve Tissue Proteins; D009994:Osmolar Concentration; D010750:Phosphoproteins / Q000378:metabolism*; D010786:Photoreceptor Cells / Q000502:physiology*; D051603:Recoverin; D015398:Signal Transduction
D002135:Calcium-Binding Proteins; D005136:Eye Proteins; D008074:Lipoproteins; D009419:Nerve Tissue Proteins; D010750:Phosphoproteins; C496731:RCVRN protein, human; D051603:Recoverin; D051597:Hippocalcin; D002118:Calcium