Regulation of Phosphatidic Acid Metabolism by Sphingolipids in the Central Nervous System

Figure 2

Modulation of lipid enzymatic activities by sphingolipids in two experimental models of isolated rod outer segments from vertebrate retinas under dark (DROS) and light (BLROS) conditions. Under dark condition Cer, Sph, and their phosphorylated products, S1P and C1P, diminish LPPs and DAGL activities. Under light condition, both Sph and Cer stimulate DAGL activity. These effects depend on the presence of soluble and peripherial proteins, as was observed in depleted DROS and BLROS where LPPs’ inhibition produced by sphingolipids is higher than in entire ROS. Interestingly, in depleted DROS, the absence of these proteins produces an increase in DAGL activity. These results indicate that protein translocation (transducin and arrestin) between inner and outer segment or protein activation, caused by light exposure, could modulate enzymatic activities involved in PA metabolism. The relative size of arrows indicates the different degree of PA metabolism in DROS and BLROS.