Differential regulation of phosphatidylcholine-derived signaling pathways in synaptic membrane rafts

MATEOS, MELINA VALERIA; SALVADOR, GABRIELA ALEJANDRA; GIUSTO, NORMA MARÍA

San Miguel de Tucumán, Tucumán, Argentina

Congreso; XLV Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2009

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB)

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 membrane rafts (SMR) isolated from adult and aged rats. The SMR isolation was based on their relative insolubility in cold Triton X-100 (1%). Western blot assays showed that SMR were enriched in Caveolin and c-Src. In addition, SMR presented significant higher sphingomyelin and cholesterol content than purified synaptic endings (Syn). Moreover, SMR phospholipids presented a more saturated fatty acid composition. The presence of PC-specific phospholipase C (PC-PLC) and phospholipase D (PLD) in Syn was previously reported (Mateos et al., 2006 and 2008). Both signaling pathways generate the lipid messenger diacylglycerol (DAG) by catalyzing PC hydrolysis. DAG generated by PC-PLC was measured in the presence of 2% ethanol yielding a specific activity 60% higher in SMR than that found in Syn. PLD1 localization was also increased in SMR; however, GTPãS only stimulated PLD activity in SMR from aged rats.  On the other hand, PLD2 was excluded from the SMR fraction. Our results show a selective localization and an age-dependent regulation of PC-derived signaling in SMR and Syn.