Shedding Light On Cones

Department of Biochemistry and Department of Molecular Biology and Ophthalmology, SUNY Upstate Medical University, Syracuse, NY 13210, USA.
The Journal of General Physiology (Impact Factor: 4.79). 05/2006; 127(4):355-8. DOI: 10.1085/jgp.200609528
Source: PubMed
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    ABSTRACT: Light-induced translocation of rod alpha-transducin (rTalpha, GNAT1) has been recognized as one of the mechanisms for light adaptation in rods. However, cone alpha-transducin (cTalpha, GNAT2) has not been shown to have such light-dependent redistribution. To investigate potential reasons for the restriction of cTalpha to the cone outer segment, the authors established a transient transgenic strategy to express cone Talpha within rod photoreceptor cells, and the location of the cone Talpha within rods and cones was examined under different light conditions. Vector DNA that expresses cTalpha and green fluorescent protein (GFP) bicistronically under control of the cytomegalovirus (CMV) promoter was injected subretinally into the eyes of neonatal rats, and this was followed by electroporation. The localization of cTalpha in rods and cones under different light conditions was determined by immunofluorescent techniques. Injection of the cDNA constructs resulted in the successful transient transfection of retinal cells. When cTalpha was exogenously expressed in rods, its localization paralleled that of endogenous rTalpha under light and dark conditions. Further experiments, with higher intensity light (7000 lux), demonstrated that endogenous cTalpha can also translocate in cone photoreceptor cells to the same extent it does in rods under 600 lux light. The authors successfully established an in vivo transient retinal transfection model. The demonstration of cTalpha translocation in rods indicates cTalpha is not inherently prevented from translocating. The novel observation of cTalpha translocation under high-intensity light suggests a light threshold regulates the redistribution of cTalpha possibly as a protective response against very bright light.
    Investigative Ophthalmology &amp Visual Science 08/2007; 48(7):3350-5. DOI:10.1167/iovs.07-0126 · 3.40 Impact Factor
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    ABSTRACT: Members of the G protein-coupled receptor kinase family play essential roles in signal turnoff for the majority of G protein-coupled receptors. GRK1, first identified almost 40 years ago, and GRK7, the most recently identified member of the GRK family, are retina-specific GRKs involved in the recovery and adaptation of rod and cone photoreceptors in the vertebrate retina. This report reviews the expression patterns of these two kinases, as well as the effect of their interaction with their substrates and binding partners. The phosphorylation of GRK1 and GRK7 by cAMP-dependent protein kinase (PKA) is also discussed.
    Advances in Experimental Medicine and Biology 01/2012; 723:821-7. DOI:10.1007/978-1-4614-0631-0_105 · 1.96 Impact Factor

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