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X. Zhu, K. Wu, L. Rife, B. Brown, C.M. Craft; Rod Arrestin Expression and Function in Cone Photoreceptors . Invest. Ophthalmol. Vis. Sci. 2005;46(13):1179.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose:Rod arrestin (Arr) is highly expressed in retinal photoreceptors, and its signal shutoff function in rods has been extensively studied. When a cone photoreceptor–specific arrestin, named cone arrestin (CAR), was discovered, it was postulated that Arr is rod–specific and CAR cone–specific. Recently, in the pure–cone retina of the Nrl knockout (KO, –/–) mice, prominent co–expression of these two distinct visual arrestins was observed. This study was initiated to determine if Arr may have a functional role in Nrl–/– cones and if both visual arrestins are co–expressed in normal retinal cone photoreceptors. Methods:Retinal dissociation and immunofluorescence double labeling with an Arr–specific monoclonal antibody and a CAR–specific polyclonal antibody were used to determine the potential co–expression of Arr and CAR in wildtype cone photoreceptors. To explore the potential roles of Arr in cones, Nrl–/–Arr–/– double KO and Nrl–/–Grk1–/–Arr–/– triple KO mice were generated by crossing the Arr–/– mice (provided by J. Chen, Nature 1997, 389:505) with the Nrl–/–Grk1–/– double KO mice (Zhu et al., J. Neurosci. 2003, 23:6152). Paired flash electroretinography (ERG) with different inter–stimulus intervals was used under either mesopic or photopic conditions to measure the photoresponse recovery of the double and triple KO mice. Results: Co–expression of Arr and CAR was confirmed in normal wildtype mouse cones. Paired flash ERG recordings show that the photoreceptors of the Nrl–/–Arr–/– and Nrl–/–Grk1–/–Arr–/– mice had only slightly slowed recovery, compared to the Nrl–/– and the Nrl–/–Grk1–/– mice, respectively, while the Nrl–/–Grk1–/– mice had a more dramatically slowed recovery. Interestingly, a 6–fc background light that could fully suppress rod response in the wildtype mouse retina also partially suppressed the cone response in the Nrl–/–Arr–/–, Nrl–/–Grk1–/– and Nrl–/–Grk1–/–Arr–/– mouse retinas in the sequence of Nrl–/–Grk1–/–Arr–/–>Nrl–/–Grk1–/–>Nrl–/–Arr–/–>Nrl–/–. Also, ERG response of the Nrl–/–Arr–/– mice had significantly delayed implicit time, compared to that of the Nrl–/–, Nrl–/–Grk1–/– and Nrl–/–Grk1–/–Arr–/– mice under both mesopic and photopic conditions, whereas ERG of the Nrl–/–Grk1–/– mice had shortened implicit time, compared to the Nrl–/– mice, only under photopic conditions. Conclusions:Our results suggest that Arr is expressed and functioning in cone photoreceptors, in addition to rod photoreceptors, in the mouse retina.
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