Buratta S, Migliorati G, Marchetti C, Mambrini R, Riccardi C, Mozzi R
Department of Internal Medicine and Endocrine and Metabolic Sciences-Biochemistry Laboratory, University of Perugia, Italy.
Mol Cell Biochem. 2000 Aug;211(1-2):61-7. doi: 10.1023/a:1007102531404.
The exposure of phosphatidylserine toward the external surface of the membrane is a well-established event of programmed cell death. The possibility that an apoptotic stimulus influences the metabolism of this phospholipid could be relevant not only in relation to the previously mentioned event but also in relation to the capability of membrane phosphatidylserine to influence PKC activity. The present investigation demonstrates that treatment of mouse thymocytes with the apoptotic stimulus dexamethasone, enhances the incorporation of [3H]serine into phosphatidylserine. Cell treatment with dexamethasone also enhanced the activity of serine base exchange enzyme, assayed in thymocyte lysate. Both the effects were observed at periods of treatment preceding DNA fragmentation. The addition of unlabelled ethanolamine, together with [3H]serine to the medium containing dexamethasone-treated thymocytes lowered the radioactivity into phosphatidylserine. Serine base exchange enzyme activity was influenced by the procedure used to prepare thymocyte lysate and was lowered by the addition of fluoroaluminate, that is widely used as a G-protein activator. The increase of serine base exchange enzyme activity induced by dexamethasone treatment was observed independently by the procedure used to prepare cell lysate and by the presence or absence of fluoroaluminate.
磷脂酰丝氨酸暴露于细胞膜外表面是程序性细胞死亡中一个已被充分证实的现象。凋亡刺激影响这种磷脂代谢的可能性不仅与上述现象相关，还与膜磷脂酰丝氨酸影响蛋白激酶C（PKC）活性的能力有关。本研究表明，用凋亡刺激物地塞米松处理小鼠胸腺细胞，可增强[3H]丝氨酸掺入磷脂酰丝氨酸的过程。用地塞米松处理细胞还增强了在胸腺细胞裂解物中检测到的丝氨酸碱基交换酶的活性。这两种效应在DNA片段化之前的处理阶段就已观察到。在含有经地塞米松处理的胸腺细胞的培养基中，加入未标记的乙醇胺和[3H]丝氨酸，可降低磷脂酰丝氨酸中的放射性。丝氨酸碱基交换酶活性受制备胸腺细胞裂解物所用方法的影响，并且加入广泛用作G蛋白激活剂的氟铝酸盐后活性降低。无论制备细胞裂解物所用方法如何，也无论是否存在氟铝酸盐，均可观察到地塞米松处理诱导的丝氨酸碱基交换酶活性增加。
