EXPRESSION OF NOVEL OPSINS AND INTRINSIC LIGHT RESPONSES IN THE MAMMALIAN RETINAL GANGLION CELL LINE RGC-5. PRESENCE OF OPN5 IN THE RAT RETINA.

NIETO PS; VALDEZ DJ; ACOSTA-RODRÍGUEZ VICTORIA A.; GUIDO ME

PLOS ONE

PUBLIC LIBRARY SCIENCE

Año: 2011 vol. 6 p. 1 - 12

1932-6203

Abstract According to the current knowledge, the vertebrate retina contains three classes of photoreceptor cells: cones and rods responsible for vision, and intrinsically photoresponsive retinal ganglion cells (RGCs) involved in diverse non-visual functions such as photic entrainment of daily rhythms and pupillary light responses. In this paper we investigated the potential capability of the rat RGC line, RGC-5, as intrinsic photoreceptors by assessing the presence of visual and non-visual opsins as well as the responses to brief light pulses on the expression of the immediate-early gene protein c-Fos and intracellular Ca2+mobilization. Cultured RGC-5 cells express a number of photopigments such as retinal G protein coupled receptor (RGR), encephalopsin/panopsin (Opn3), neuropsin (Opn5) and cone opsin (Opn1mw) but not melanopsin (Opn4) or rhodopsin. Opn5 immunoreactivity was also observed in the inner retina of rat mainly localized in the ganglion cell layer (GCL). In addition, subsets of RGC-5 cells displayed significant sustained changes in intracellular Ca2+ levels after bright white light pulses of 30 to 60 sec of duration while cells exhibit the induction of the c-Fos protein by a 30 min-light pulse. The results demonstrate that RGC-5 cells expressing diverse putative functional photopigments display intrinsic photosensitivity which accounts for the photic induction of c-Fos protein and changes in intracellular Ca2+ mobilization. The presence of Opn5 in the GCL of the rat retina may suggest the existence of a novel type of photoreceptor cells. Key words: Retinal Ganglion Cells, c-Fos, calcium, photopigments, photosensitivity, non-visual opsins, phototransduction.