Zhao Lixia, Brinton Roberta Diaz
Department of Molecular Pharmacology and Toxicology, University of Southern California, Pharmaceutical Sciences Center, Los Angeles, CA 90089, USA.
Brain Res. 2002 Jul 5;943(1):117-31. doi: 10.1016/s0006-8993(02)02484-8.
We sought to determine whether vasopressin V(1a) receptor (V(1a)R) mRNA detected in cortical astrocytes [Brain Res. Mol. Brain Res. 45 (1997) 138] was translated into functional receptors by investigating the effector calcium signaling cascade associated with the vasopressin V(1a) receptor subtype. Analysis of intracellular calcium dynamics using the calcium-sensitive dye fura-2 AM indicated that exposure of cortical astrocytes to V(1) vasopressin receptor agonist, [Phe(2),Orn(8)]-oxytocin, induced a marked dose-dependent increase in intracellular calcium which was abolished by depletion of extracellular calcium. V(1) agonist treatment induced a rapid increase in calcium signal in both the cytoplasm and nucleus, which was followed by an accumulation of the calcium signal in the nucleus, suggesting translocation of cytoplasmic calcium into the nucleus. The nuclear calcium signal was sustained for several seconds followed by translocation back to the cytoplasm. Following the nuclear-to-cytoplasmic calcium translocation, total free intracellular calcium concentration decreased. The dynamic calcium cytoplasmic and nuclear localization was confirmed by laser scanning confocal microscopy coupled with the calcium-sensitive dye fluo-3 AM. To determine the source of calcium, V(1) agonist-induced (45)Ca(2+) uptake and [(3)H]IP(1) accumulation were investigated. V(1) agonist induced significant and rapid uptake of (45)Ca(2+) and a significant dose-dependent increase in [(3)H]IP(1) accumulation in cortical astrocytes. To our knowledge, this is the first documentation of a vasopressin receptor-induced calcium signaling cascade in cortical astrocytes and the first documentation of vasopressin receptor induction of nuclear calcium signaling.
我们试图通过研究与血管加压素V(1a)受体亚型相关的效应钙信号级联反应，来确定在皮质星形胶质细胞中检测到的血管加压素V(1a)受体（V(1a)R）mRNA是否被翻译成功能性受体。使用钙敏染料fura-2 AM对细胞内钙动力学进行分析表明，将皮质星形胶质细胞暴露于V(1)血管加压素受体激动剂[Phe(2),Orn(8)]-催产素中，可诱导细胞内钙显著的剂量依赖性增加，而细胞外钙耗竭可消除这种增加。V(1)激动剂处理可诱导细胞质和细胞核中的钙信号迅速增加，随后细胞核中钙信号积累，提示细胞质钙向细胞核转运。细胞核钙信号持续数秒，随后转运回细胞质。细胞核到细胞质的钙转运后，细胞内总游离钙浓度降低。激光扫描共聚焦显微镜结合钙敏染料fluo-3 AM证实了钙在细胞质和细胞核中的动态定位。为了确定钙的来源，研究了V(1)激动剂诱导的(^{45})Ca(^{2 +})摄取和[(^{3})H]IP(1)积累。V(1)激动剂可诱导皮质星形胶质细胞中(^{45})Ca(^{2 +})的显著快速摄取以及[(^{3})H]IP(1)积累的显著剂量依赖性增加。据我们所知，这是首次记录到血管加压素受体在皮质星形胶质细胞中诱导的钙信号级联反应，也是首次记录到血管加压素受体诱导的细胞核钙信号。
