College of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Republic of Korea.
Biochem Biophys Res Commun. 2012 Oct 5;426(4):590-5. doi: 10.1016/j.bbrc.2012.08.132. Epub 2012 Sep 4.
We investigated the regulation of Hsp27 phosphorylation by protein kinase C δ (PKCδ) during etoposide-induced apoptosis. The phosphorylation of Hsp27 at Ser78 was temporally correlated with the proteolytic activation of PKCδ during apoptosis. Hsp27 phosphorylation was dependent on the activity of PKCδ since treatment with rottlerin, a chemical inhibitor of PKCδ, or overexpression of a PKCδ dominant negative mutant abolished the phosphorylation. In addition, recombinant PKCδ phosphorylated Hsp27 at Ser78 in vitro. Moreover, caspase-3 was specifically activated following Hsp27 phosphorylation at Ser78. Pull-down assays using a phosphomimetic Hsp27 mutant revealed that binding between Hsp27 and cytochrome c was abolished by the phosphorylation. These results suggest that Hsp27 dissociates from cytochrome c following PKCδ-mediated phosphorylation at Ser78, which allows formation of the apoptosome and stimulates apoptotic progression.
我们研究了蛋白激酶 C δ（PKCδ）在依托泊苷诱导细胞凋亡过程中对 Hsp27 磷酸化的调节作用。Hsp27 在丝氨酸 78 位的磷酸化与凋亡过程中 PKCδ 的蛋白水解激活在时间上相关。Hsp27 的磷酸化依赖于 PKCδ 的活性，因为用 PKCδ 的化学抑制剂罗特林或过表达 PKCδ 的显性失活突变体处理可消除磷酸化。此外，重组 PKCδ 在体外将 Hsp27 磷酸化于丝氨酸 78 位。此外，Hsp27 在丝氨酸 78 位磷酸化后，半胱天冬酶-3 被特异性激活。使用磷酸模拟 Hsp27 突变体进行的下拉实验表明，Hsp27 与细胞色素 c 之间的结合在 PKCδ 介导的丝氨酸 78 位磷酸化后被消除。这些结果表明，Hsp27 与细胞色素 c 解离后，PKCδ 介导的磷酸化，这允许凋亡小体的形成并刺激凋亡进程。
