Insulin-stimulated phosphatidic acid (PA) formation in rat CC synaptosomes. Is DAGKe activated?

ZULIAN, S.E.; ILINCHETA DE BOSCHERO, M.; GIUSTO, N.M.

Mar del Plata

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular; 2007

Insulin (I) plus vanadate (V) increased DAGK activity in rat CC synaptosomes. A phospholipase-dependent activation and a phospholipase-independent effect (PIE) was reported. PIE was studied with ATPg32P in a micellar assay using octylglucoside (OG) and di 16:0 or 18:0-20:4 DAG (250 mM). It was suggested that DAGKe participates in IR signaling (SAIB 2006). DAGKe has been reported to be negatively modulated by PIP2. Potential regulators of PIP2 levels through G protein activation (GTPgS and NaF) were used. R59022 and R59949, type I DAGK inhibitors, were also employed to evaluate another DAGK activities involving. In assays performed with DMSO, PA synthesized with 18:0-20:4 DAG (PA-u) or di-16:0 DAG (PA-s) represented 966 and 177 % respectively with respect to endogenous DAG. I+V stimulated similarly PA-u or PA-s synthesis. In the presence of DAGK inhibitors, PA synthesis was unchanged. GTPgS and NaF, are potent stimulators of PA-u or PA-s synthesis. However, they failed to stimulate the increased PA-u or PA-s synthesis when they were added after 5 min exposure to I+V. PIP2 labeling was increased by GTPgS and NaF when PA-u was increased. However, although PA-s was increased, PIP2 labeling was strongly decreased. I+V increased PA formation through predominant DAGKe activity that could be modulated by PIP2 depletion. A potential role in PIP2 resynthesis is suggested.