OPSIN EXPRESSION AND LIGHT RESPONSES IN RGC-5 CELLS

NIETO, P. S; VALDEZ, D. J; ACOSTA-RODRÍGUEZ, V. A; GUIDO M. E.

Cholula

Simposio; XI Latin American Symposium of Chronobiology; 2011

The vertebrate retina contains at least 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 work we investigated the potential capability of the rat RGC line (RGC-5) as intrinsic photosensitive cells 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. We observed that cultured RGC-5 cells express opsin mRNAs such as retinal G protein coupled receptor (RGR), encephalopsin/panopsin (Opn3), neuropsin (Opn5) and cone opsin but not melanopsin (Opn4) or rhodopsin. Furthermore, the expression of the OPN5 in RGC-5 cells was confirmed by inmunocitochemistry. In adition, we report for the first time the localization of this opsin within the mammalian (rat) retina: OPN5 is expressed in some neurons of the inner nuclear layer and in the ganglion cell layer. Strikingly, functional assays in RGC-5 cells showed significant changes in intracellular Ca2+ levels in subsets of RGC-5 cells 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. In summary, our results indicate that RGC-5 cells express diverse putative functional photopigments and display the intrinsic photic induction of c-Fos protein and changes in intracellular Ca2+ mobilization.