Salvador Gabriela A, Ilincheta de Boschero Monica G, Pasquaré Susana J, Giusto Norma M
Instituto de Investigaciones Bioquímicas de Bahía Blanca, Universidad Nacional del Sur-CONICET, Bahía Blanca, Argentina.
J Neurosci Res. 2005 Jul 15;81(2):244-52. doi: 10.1002/jnr.20565.
Insulin receptor associated with the cerebral cortex (CC) has been shown to be involved in brain cognitive functions. Furthermore, deterioration of insulin signaling has been associated with age-related brain degeneration. We have reported previously that aging stimulates phospholipase D/phosphatidate phosphohydrolase 2 (PLD/PAP2) pathway in CC synaptosomes from aged rats, generating a differential availability of their reaction products: diacylglycerol (DAG) and phosphatidic acid (PA). The aim of this work was to determine the effect of aging on DAG kinase (DAGK), as an alternative pathway for PA generation, and to evaluate the effect of insulin on PLD/PAP2 pathway and DAGK. PLD, PAP2, and DAGK activities were measured using specific radiolabeled substrates in CC synaptosomes from adult (4 months old) and aged rats (28 months old). In adult animals, in the presence of the tyrosine phosphatase inhibitor (sodium o-vanadate), insulin stimulated PLD activity at 5 min incubation. DAGK activity was also increased at the same time of incubation and PAP2 was inhibited. In aged animals, PLD activity was not modified by the presence of insulin plus vanadate, PAP2 was inhibited, and DAGK was stimulated by the hormone. Insulin, vanadate, and the combination of both induced protein tyrosine phosphorylation in adult CC synaptosomes. Aged rats showed a lower level of protein phosphorylation with respect to adult rats. Our results show that insulin modulates PA and DAG availability through the regulation of PLD/PAP2 and DAGK pathways in adult rat CC synaptosomes. Additionally, we demonstrated that PA and DAG generation is regulated differentially by insulin during aging.
与大脑皮层（CC）相关的胰岛素受体已被证明参与大脑认知功能。此外，胰岛素信号转导的恶化与年龄相关的脑退化有关。我们之前报道过，衰老会刺激老年大鼠CC突触体中的磷脂酶D/磷脂酸磷酸水解酶2（PLD/PAP2）途径，产生其反应产物二酰基甘油（DAG）和磷脂酸（PA）的不同可用性。这项工作的目的是确定衰老对作为PA生成替代途径的DAG激酶（DAGK）的影响，并评估胰岛素对PLD/PAP2途径和DAGK的影响。使用特定的放射性标记底物在成年（4个月大）和老年大鼠（28个月大）的CC突触体中测量PLD、PAP2和DAGK的活性。在成年动物中，在酪氨酸磷酸酶抑制剂（邻钒酸钠）存在的情况下，胰岛素在孵育5分钟时刺激PLD活性。在相同孵育时间，DAGK活性也增加，而PAP2受到抑制。在老年动物中，胰岛素加钒酸盐的存在并未改变PLD活性，PAP2受到抑制，并且激素刺激DAGK。胰岛素、钒酸盐以及两者的组合在成年CC突触体中诱导蛋白质酪氨酸磷酸化。与成年大鼠相比，老年大鼠的蛋白质磷酸化水平较低。我们的结果表明，胰岛素通过调节成年大鼠CC突触体中的PLD/PAP2和DAGK途径来调节PA和DAG的可用性。此外，我们证明了在衰老过程中，PA和DAG的生成受到胰岛素的不同调节。
