Diacylglyceride lipase activity in rod outer segments depends on the illumination state of the retina

PASQUARÉ, S.J.; GIUSTO, N.M.

NEUROCHEMISTRY INTERNATIONAL

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2008 vol. 53 p. 382 - 388

0197-0186

We have demonstrated that the competition between phosphatidic acid (PA) and lysophosphatidic acid(LPA), sphingosine 1-phosphate (S1P) and ceramide 1-phosphate (C1P) for lipid phosphate phosphatases(LPP) generates different levels of diacylglycerol (DAG) depending on the illumination state of the retina.The aim of the present research was to determine the diacylglyceride lipase (DAGL) activity in purifiedrod outer segments (ROS) obtained fromdark-adapted retinas (DROS) or light-adapted retinas (BLROS) aswell as in ROS membrane preparations depleted of soluble and peripheral proteins. [2-3H]mono-acylglycerol (MAG), the product of DAGL, was evaluated from [2-3H]DAG generated by LPP action on[2-3H]PA in the presence of either LPA, S1P or C1P.MAG productionwas inhibited by 55% in BLROS and by25% when the enzymatic assay was carried out in ROS obtained fromdark-adapted retinas and incubatedunder room light (LROS). The most important events occurred in DROS where co-incubation of [2-3H]PAwith LPA, S1P or C1P diminished MAG production. A higher level of DAGL activity was observed in LROSthan in BLROS, though this difference was not apparent in the presence of LPA, S1P or C1P. DAGL activityin depleted DROS was diminished with respect to that in entire DROS. LPA, S1P and C1P produced asimilar decrease in MAG production in depleted DROS whereas only C1P significantly diminished MAGgeneration in depleted BLROS. Sphingosine and ceramide inhibited MAG production in entire DROS andstimulated its generation in BLROS. Sphingosine and ceramide stimulated MAG generation in bothdepleted DROS and BLROS. Under our experimental conditions the degree of MAG production dependedon the illumination state of the retina. We therefore suggest that proteins related to phototransductionphenomena are involved in the effects observed in the presence of S1P/sphingosine or C1P/ceramide. 2008 Elsevier Ltd. All rights reserved.