Insulin receptor: Presence and activation in photoreceptor nuclei from bovine retina.

NATALINI, P.N.; MATEOS, M.V.; GIUSTO, N.M.; ILINCHETA, M.

Rosario

Congreso; Reunión anual SAIB 2014; 2014

We have recently reported a novel light-dependent activation of diacylglycerol kinase (DAGK) and protein kinase C at the nuclear level of photoreceptor cells. We have also observed that ex-vivo light exposure of bovine retinas modulates insulin-related signaling pathways, such as PI3K-Akt and MAPK pathways, in photoreceptor nuclei. The aim of the present study was to analyze the presence of insulin receptor (IR) in photoreceptor nuclei and the possible DAGK modulation by insulin. A nuclear fraction enriched in small nucleus from photoreceptor cells (PNF) was obtained for the study of IR presence and phosphorylation state as well as local insulin action in lipid kinases in PNF. Immunofluorescence and western blot studies revealed the presence of IR in PNF and a light-dependent increase of nuclear IR. Polyphosphoinositides and phosphatidic acid (PA) formation were found to be increased when isolated nuclei were exposed to 0.8 µM insulin plus 0.2 mM vanadate in nuclei from retinas exposed to light with respect to the darkness condition. Our results i) demonstrate the presence and the functional state of IR in PNF from bovine retinas, ii) suggest a light-mediated localization of IR in PNF and iii) reveal local insulin effects on nuclear lipid enzymes involved in the regulation of lipid second messengers, such as DAG and PA.