PRESENCE OF ERK2 IN RAT RETINAL CELLS

Purpose. Extracellular signal-regulated kinase 2 (ERK2) participates i n the phosphorylation cascade that is activated in the an early intrac ellular response to various hormones and growth factors. We examined t he expression and distribution of the ERK2 protein and mRNA in the rat retina before and after light exposure. Methods. Rats were held on a 12 hr light/dark cycle and their retinas were removed and examined eit her just before or 2 or 30 min after light exposure. The tissue was pr ocessed for West ern blotting to evaluate the presence of the protein for ERK2, and for in situ hybridization to evaluate the mRNA of ERK2. Results. The Western blotting method showed a strong specific staining of a 42 kDa protein band in the retinal samples. This band correspond ed to the expected size of p42 MAP kinase (ERK2). In situ hybridizatio n histochemistry showed an intense localization of ERK2 mRNA in the ou ter nuclear layer (ONL), the inner nuclear layer (INL), and the gangli on cell layer (GCL) of the retina. The intensity and distribution of t hese signals did not differ among the animals, regardless of exposure io light. Conclusions. While ERK2 may be involved in the signal transd uction system activated in retinal cells by light exposure, its precis e role remains to be defined.