Serine 59 Phosphorylation of αB-Crystallin Down-regulates Its Anti-apoptotic Function by Binding and Sequestering Bcl-2 in Breast Cancer Cells
Serine 59 Phosphorylation of αB-Crystallin Down-regulates Its Anti-apoptotic Function by Binding and Sequestering Bcl-2 in Breast Cancer Cells
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DOI：
10.1074/jbc.m110.124388
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发表时间：
2010-11-26
影响因子：
4.8
通讯作者：
Lilienbaum, Alain
中科院分区：
文献类型：
--
作者：
Launay, Nathalie;Tarze, Agathe;Lilienbaum, Alain
小热休克蛋白（sHSP）α B-晶状体蛋白是乳腺癌中的一种新的癌蛋白，可预测乳腺癌的不良临床结局。然而，尽管一些报道已经证明sHSP的磷酸化改变了它们的结构和功能特性，但尚未研究α B-晶体蛋白磷酸化在癌细胞中的意义。在这项研究中，我们的特点是磷酸化状态的α B-晶体蛋白在乳腺上皮癌细胞系MCF 7提交抗癌药物，如长春碱。我们已经表明，在长春碱反应的α B-晶体蛋白的主要磷酸化位点是丝氨酸59，并确定了这种翻译后修饰和更高的凋亡水平之间的相关性。丝氨酸59“假磷酸化”突变体（S59 E）的过表达诱导长春碱处理的MCF 7细胞的凋亡水平显著增加。相反，野生型α B-晶体蛋白或“非磷酸化”突变体（S59 A）的过表达导致对这种微管解聚剂的抗性，而通过表达shRNA抑制内源性α B-晶体蛋白水平降低了它。进一步分析这种现象的分子机制，我们首次报道磷酸化α B-晶体蛋白优先与Bcl-2相互作用，一种抗凋亡蛋白，这种相互作用阻止Bcl-2易位到线粒体。因此，本研究确定丝氨酸59磷酸化是乳腺癌中α B-晶状体蛋白抗凋亡功能下调的重要关键，并提出了改善抗癌治疗的新策略。
The small heat shock protein (sHSP) alpha B-crystallin is a new oncoprotein in breast carcinoma that predicts poor clinical outcome in breast cancer. However, although several reports have demonstrated that phosphorylation of sHSPs modify their structural and functional properties, the significance of alpha B-crystallin phosphorylation in cancer cells has not yet been investigated. In this study, we have characterized the phosphorylation status of alpha B-crystallin in breast epithelial carcinoma cells line MCF7 submitted to anti-cancer agents like vinblastine. We have showed that the main phosphorylation site of alpha B-crystallin in response to vinblastine is serine 59 and determined a correlation between this post-translational modification and higher apoptosis level. The overexpression of the serine 59 "pseudophosphorylated" mutant (S59E) induces a significant increase in the apoptosis level of vinblastine-treated MCF7 cells. In contrast, overexpression of wild-type alpha B-crystallin or "nonphosphorylatable" mutant (S59A) result in a resistance to this microtubule-depolymerizing agent, while inhibition of endogenous levels of alpha B-crystallin by expression of shRNA lowers it. Analyzing further the molecular mechanism of this phenomenon, we report for the first time that phosphorylated alpha B-crystallin preferentially interacts with Bcl-2, an anti-apoptotic protein, and this interaction prevents the translocation of Bcl-2 to mitochondria. Hence, this study identifies serine 59 phosphorylation as an important key in the down-regulation of alpha B-crystallin antiapoptotic function in breast cancer and suggests new strategies to improve anti-cancer treatments.