Abstract
Purpose: :
Arrestin domain-containing (ArrDC) proteins are early ancestors of the visual arrestins, and have been shown to have a role in guiding endocytosis in yeast. The purpose of this project is to determine the expression of these ArrDC proteins in the mammalian retina using reverse-transcription PCR and immunohistochemistry.
Methods: :
mRNA was isolated from murine retinal tissue and used to prepare cDNA via first-strand synthesis. PCR was performed using this cDNA, and the reaction products were cloned into Escherichia coli expression vectors, and sequenced. Purified protein and synthetic peptides were used to generate monoclonal antibodies, which were used to probe retinal sections. A commercial antibody was used to probe for thioredoxin-interacting protein (TXNIP). Visualization was performed via laser confocal fluorescence microscopy.
Results: :
Arrestin-domain containing (ArrDC) proteins were identified in multiple layers of the retina. ArrDC1 was identified in Muller cells and horizontal cells, co-localizing with glutamine synthetase in the Muller cells. ArrDC2 was identified predominately in ganglion cells and, to a lesser extent, in the inner plexiform layer. ArrDC3 was identified in vesicles of the retinal pigment epithelium (RPE). ArrDC4 was identified in ganglion cells and the inner plexiform layer (similar to ArrDC2), as well as in horizontal cells. TXNIP was identified in apical processes of the RPE. ArrDC5 was not present in retinal tissue.
Conclusions: :
All ArrDC proteins, except ArrDC5, are present throughout the mammalian retina. The different distributions observed for the various ArrDC proteins suggest varied functions in retina. The localization of TXNIP and ArrDC3 in RPE apical processes and vesicles suggests a role in outer segment phagocytosis.
Keywords: gene/expression • in situ hybridization • retina: distal (photoreceptors, horizontal cells, bipolar cells)