Selective localization and age-dependent regulation of phosphatidylcholine-derived signaling in detergent resistant membranes from synaptic endings

MATEOS M.V.; SALVADOR, G.; GIUSTO N.M.

BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES

ELSEVIER SCIENCE BV

Lugar: Oxford; Año: 2009

0005-2736

Membrane rafts are specialized microdomains that compartmentalize several signal transduction processes. In this work, we investigate the presence of phosphatidylcholine (PC)-derived signaling in synaptosomal detergent resistant membranes (DRMs) isolated from adult and aged rats. DRM isolation was based on their relative insolubility in cold Triton X-100 (1%). Western blot assays showed that DRMs were enriched in Caveolin and c-Src. In addition, DRMs presented significant higher sphingomyelin (SM) and cholesterol content than purified synaptic endings (Syn). Additionally, SM content increased by 36% in DRMs obtained from aged animals with respect to adults. Total phospholipid-fatty acid composition from DRMs presented an increase in 16:0 (35%), and a decrease in 20:4n-6 (67%) and 22:6n-3 (68%) content in adults. Similar changes in fatty acid composition were observed between DRMs and Syn obtained from aged rats. Nevertheless, the 20:4n-6 and 22:6n-3 content significantly decreased (80%) with respect to DRM from adults.  We have previously reported the presence of PC-specific phospholipase C (PC-PLC) and phospholipase D (PLD) in Syn. Both signaling pathways generate the lipid messenger diacylglycerol (DAG) by catalyzing PC hydrolysis. PC-PLC localization was augmented in DRMs and that was confirmed by a 60% increase in DAG generated in the presence of ethanol. PLD1 localization was also increased in DRMs; however, GTPãS only stimulated PLD activity in DRMs from aged rats.  On the other hand, PLD2 was excluded from the DRM fraction. Our results show a selective localization and an age-dependent regulation of PC-derived signaling in DRMs and synaptic endings.