Phospholipid metabolism is regulated by growth factors in bovine rod outer segments

GIUSTO, NORMA; SALVADOR, GABRIELA; PASQUARÉ, SUSANA; URANGA, ROMINA; MATEOS, MELINA

Buenos Aires, Argentina.

Congreso; XVII International Congress of Eye Research; 2006

Eye Research Association

Bovine rod outer segments (ROS) contain Insulin (I) and Insulin-like growth factor (IGF-1) receptors. It has been previously demonstrated that Insulin receptor can be tyrosine-phosphorylated by light. However, the activity and function of these receptors in non-bleached ROS have not been fully elucidated to date. The aim of the present work was to characterize phospholipid metabolism in ROS incubated with different growth factors (Insulin, IGF-1, and Nerve Growth Factor) under darkness condition. Phospholipid metabolism was measured in ROS preincubated with the above-mentioned factors in the presence of either exogenous phosphatidylcholine ([14C ]PC) or phosphatidic acid ([3H] PA) or [g32P ATP]. Western blot analyses using anti-phosphotyrosine antibodies indicated that Insulin and IGF-1 increased tyrosine phosphorylation of several ROS proteins. No description of NFG receptors in purified ROS was carried out, still it could be observed that this growth factor stimulates tyrosine phosphorylation of ROS protein. NGF and IGF-1 stimulated monoacylglycerol (MAG) formation from [14C ]PC. DAG generation was also stimulated by NGF using either [3H]PA or [14C]PC as precursors. The generation of free fatty acids from PC was increased by Insulin and NGF. Additionally, phosphoinositide metabolism measured using endogenous phosphatidylinositols (PIs) and exogenous [g32P]ATP was stimulated by Insulin and NGF. Our work demonstrates that growth factors regulate phospholipid metabolism in non-illuminated ROS .