β-Arrestin-related proteins in ocular tissues

Purpose. Proteins of the arrestin family contribute to the regulation of G-protein-mediated transduction. In this study, the presence of β-arrestins in ocular tissues was investigated. Methods. Mouse monoclonal and rabbit polyclonal antibodies were raised against the peptide Val-Asp-Thr-Asn-Ile- Leu-Glu-Leu-Asp-Thr-Asn-Asp-Asp-Asp-Ile, a sequence present in β-arrestins 1 and 2 but absent from visual arrestin. These antibodies were used for the immunohistologic detection of β-arrestins in parafin sections of rodent eyes fixed in Bouin's solution. Reverse transcription-polymerase chain reaction (RT-PCR) analysis of RNA from bovine retina, retinal pigmented epithelial (RPE) cells, lens epithelial cells, and human corneal fibroblasts was performed using β-1 arrestin primers. Results. In the eye, β-arrestin staining predominated in RPE, inner segments of photoreceptors, synaptic spherules of rods, inner plexiform layer and ganglion cell fibers, epithelial cells from ciliary body, and vessels. RT-PCR amplified a 480 bp product, corresponding to the predicted length. The sequence of PCR products from bovine retina and RPE cells was identical with the bovine β-arrestin mRNA. Conclusions. β-arrestins were detected in several ocular tissues. In photoreceptor cells, their specific localization in the synaptic terminals and plexiform layer suggests a role of β-arrestin in synaptic transmission. In other ocular tissues, the presence of β-arrestin may be related either to adrenergic signal transduction or to signal transduction mediated by other C- protein-coupled receptors.