Characterization and regulation of diacylglycerol lipase in isolated nuclei from rat cerebellum

GAVEGLIO, V.L., .; PASQUARÉ, S.J.; GIUSTO, N.M.

Florencia

Congreso; 8th IBRO World Congress of Neuroscience; 2011

IBRO

Lipids are present not only in the nuclear envelope but also inside the nucleus as a component of chromatin. Nuclear lipid metabolism differs from that in the plasma membrane or in other cellular organelles.  It gives rise to several lipid second messengers that seem to be involved in the regulation of nuclear structure and gene expression. We focus our study on the metabolic pathways for the degradation of PtdOH in isolated nuclei from central nervous system. Using [3H]PtdOH as substrate we demonstrated the existence of LPPs, DAGL, MAGL and phosphatidic acid-specific phospholipase type A (PtdOH-PLA) activities in rat cerebelar nuclei. We characterized the mentioned enzymatic activities and we evaluated the competitiveness between PA and other phosphorylated lipids by LPPs, as well as, the modulation of them by ions and detergents. These activities modulate changes in nuclear lipid composition, generating second messengers implicated in intranuclear signalling. The aim of the present work was to evaluate and characterize DAGL activity using exogenously added [3H] diacylglycerol ([3H]DAG) as substrate. We also studied its regulation by retinoic acid. To this end, adult (4 mo) rat cerebellum was homogenized and highly purified nuclei were isolated by sucrose-density ultracentrifugation. Our results indicate that MAG formation increased up to two minutes, 700 μM of substrate and about 50 µg of proteins. Interestingly, MAG production occurred at a higher DAG concentration (150 µM) than that used (60 µM) when DAG was generated from PtdOH. In addition, the nuclear membranes incubated with a nuclear receptor RAR/RXR agonist, all-trans retinoic acid (10 µM), showed a significant DAGL inhibition (70%). Taken together, our results demonstrate the presence of an important enzyme related to signalling pathways in rat cerebellum nuclei. Virginia Gaveglio is IBRO Alumni of the II IBRO-LARC Advanced School of Neuroscience. ?Signal Transduction in Central Nervous System: Facts and principles?.