EXPRESSION OF SOLUBLE PHOTOTRANSDUCTION-ASSOCIATED PROTEINS IN-GROUNDSQUIRREL RETINA

Purpose. This study describes the expression and distribution of arres tin, phosducin, and recoverin in the cone-dominant retina of the groun d squirrel Spermophilus tridecemlineatus. Methods. mRNA expression was studied by blot hybridization of ground squirrel retinal RNA, with hu man and murine RNA as controls. The distribution of the gene products in the ground squirrel retina was investigated by immunocytochemistry using radial and consecutive tangential sections. Results. Northern bl ot hybridization showed messages for arrestin (1.9 kb), phosducin (1.4 kb), and recoverin (1.2 kb) in ground squirrel retinal RNA. Both cont rols showed transcripts of the same or similar sizes. Rod-like cells a nd blue cones were stained by antibodies against arrestin and phosduci n. The arrestin antiserum stained the whole cell bodies, most intensel y in the myoid region, whereas phosducin immunoreactivity was confined to the outer and inner segments, which were stained with approximatel y equal intensity. The strongest immunoreaction was found in the photo receptor plasma membrane. Recoverin antibodies recognized the entire s oma of all photoreceptor cells. The myoid region and the synaptic pedi cles were most heavily stained. No light-dependent migration was obser ved with either antiserum in any photoreceptor type. Conclusion. The p resence of arrestin immunoreactivity in rod-like cells and blue cones is consistent with previous reports on other mammals. However, it has not been reported previously that phosducin immunoreactivity is distri buted in the same way. The colocalization of arrestin and phosducin in rod-like cells and blue cones is yet another trait distinguishing blu e cones from red and green cones.