Expression and subcellular localization of thymosin beta15 following kainic acid treatment in rat brain.

Thymosin beta15 (Tbeta15) is a pleiotropic factor which exerts multiple roles in the development of nervous system and brain diseases. In this study, we found that the expressions of Tbeta15 mRNA and protein were substantially increased in several brain regions including hippocampal formation and cerebral cortex, following kainic acid (KA)-evoked seizures in rat. Interestingly, a subset of cortex neurons exhibited nuclear Tbeta15 immunoreactivity upon KA treatment. Furthermore, translocation of Tbeta15 from cytosol to nuclei was observed in cultured neurons or HeLa cells during staurosporine (STS)-induced apoptosis, which was also verified by time-lapse imaging of YFP-tagged Tbeta15. It appeared that localization of Tbeta15 is restricted to the cytosol in normal condition by its G-actin-interacting domain, because site-directed mutagenesis of this region resulted in the nuclear localization of Tbeta15 in the absence of STS treatment. To explore the role of nuclear Tbeta15, we enforced Tbeta15 to localize in the nuclei by fusion of Tbeta15 with nuclear localization signal (NLS-Tbeta15). However, overexpression of NLS-Tbeta15 did not alter the viability of cells in response to STS treatment. Collectively, these results suggest that nuclear localization of Tbeta15 is a controlled process during KA or STS stimulation, although its functional significance is yet to be clarified.

海人酸处理后胸腺素β15在大鼠脑内的表达和亚细胞定位。

胸腺素β15(tβ15)是一种多效性因子，在神经系统和脑疾病的发展中发挥多种作用。在这项研究中，我们发现在红藻氨酸(KA)诱发的大鼠癫痫发作后，Tbeta15 mRNA和蛋白在包括海马结构和大脑皮质在内的几个脑区的表达显著增加。有趣的是，在KA处理后，一部分皮层神经元表现出核Tbeta15免疫反应性。此外，在星形孢菌素(STS)诱导的凋亡过程中，在培养的神经元或HeLa细胞中观察到Tbeta15从胞质溶胶向细胞核的转移，这也通过YFP标记的Tbeta15的延时成像得到了证实。在正常条件下，tβ15的定位似乎被其G-肌动蛋白相互作用结构域限制在胞质溶胶中，因为在没有STS处理的情况下，该区域的定点突变导致tβ15的核定位。为了探索核Tbeta15的作用，我们通过将Tbeta15与核定位信号(NLS-Tbeta15)融合，使Tbeta15定位于细胞核中。然而，NLS-tβ15的过度表达并没有改变细胞对STS治疗的反应。总的来说，这些结果表明Tbeta15的核定位在KA或STS刺激期间是一个受控过程，尽管其功能意义仍有待阐明。