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Anurima Majumder, Kimberly K. Boyd, Vasily Kerov, Saravanan Kolandaivelu, Visvanathan Ramamurthy, Nikolai O. Artemyev; Slow Retinal Degeneration in a Transgenic Mouse with N-acylated S-palmitoylated Transducin-α in Rods. Invest. Ophthalmol. Vis. Sci. 2012;53(14):758.
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The light-dependent translocation of transducin has been proposed to serve as an important mechanism of neuroprotection. Yet, direct evidence supporting this hypothesis is lacking. We have generated a transgenic mouse model with impaired light-induced translocation of transducin to probe its physiological significance. In transgenic mice, the native transducin α-subunit (Gαt1) was replaced with the Gαt1A3C mutant that is predicted to be N-acylated and S-palmitoylated.
S-palmitoylation of Gαt1A3C in mutant mice was assessed by a resin-assisted capture technique. Association of Gαt1A3C with ROS membranes was examined using extraction with GTPγS. Subcellular localization of Gαt1A3C in dark- and light-adapted rods was visualized using immunofluorescence. Retinal morphology of Gαt1A3C and control mice at various ages was evaluated by H&E staining of retina sections.
At least 40%-50% of Gαt1A3C was S-palmitoylated in transgenic mouse retina. The A3C mutant associated with ROS membranes more tightly than the wild-type Gαt1. Gαt1A3C was correctly targeted to the rod OS in darkness, but the light-dependent translocation of the mutant transducin was impaired. The retinal morphology of A3C mice appeared normal at the age of 2 months. However, 7-month old A3C mice maintained on a 12-hr light/dark cycle displayed distinct retinal degeneration (RD) with ~2-fold thinning of the outer nuclear layer. Examination of 10- and 12-months old A3C mice showed slow progression of RD. Moreover, 2-month old A3C mice kept under constant light conditions (700 lux) also developed signs of RD not seen in control mice.
Transgenic Gαt1A3C mice show impaired light-dependent translocation of transducin apparently due to enhanced affinity of the mutant Gαt1 to ROS membranes. These mice develop slow light-dependent RD.
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