Phosphorylation of EBP50 negatively regulates β-PIX-dependent Rac1 activity in anoikis
Phosphorylation of EBP50 negatively regulates β-PIX-dependent Rac1 activity in anoikis
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DOI：
10.1038/cdd.2012.4
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发表时间：
2012-06-01
影响因子：
12.4
通讯作者：
Jou, T-S
中科院分区：
文献类型：
--
作者：
Chen, J-Y;Lin, Y-Y;Jou, T-S
我们证明了一个蛋白激酶C（PKC）依赖性磷酸化的犬埃兹蛋白/radixin/膜突蛋白（ERM）结合磷蛋白50（EBP 50）在丝氨酸347/348的定点诱变和磷酸化特异性抗体。细胞分级和共聚焦成像显示EBP 50从质膜到胞质溶胶的迁移伴随着这一磷酸化事件。这些丝氨酸残基磷酸化的增加导致EBP 50从ezrin和β-PIX（Rac 1激活的两个上游调节因子）上解离。细胞过度表达EBP 50突变体，模仿丝氨酸347/348磷酸化，成为难治性肝细胞生长因子诱导的细胞扩散和散射，这通常是由Rac 1激活介导的。细胞从基质中分离也引起EBP 50磷酸化的增加，这显然是由于PKC和蛋白磷酸酶2A的抵消活性，从而导致Rac 1活化减少和失巢凋亡的诱导。细胞过度表达的EBP 50突变体的丝氨酸347/348磷酸化缺陷没有发生细胞凋亡的悬浮培养。这些研究揭示了一个信号级联，其中不同的磷酸化状态和亚细胞定位的EBP 50调节Rac 1功能。Cell Death and Differentiation（2012）19，1027-1037; doi：10.1038/cdd.2012.4; 2012年2月3日在线发表
We demonstrated a protein kinase C (PKC)-dependent phosphorylation of canine ezrin/radixin/moesin (ERM)-binding phosphoprotein 50 (EBP50) at serine 347/348 by site-directed mutagenesis and a phospho-specific antibody. Cell fractionation and confocal imaging revealed the relocation of EBP50 from the plasma membrane to cytosol that accompanied this phosphorylation event. Increased phosphorylation at these serine residues led to the dissociation of EBP50 from ezrin and beta-PIX, which are two upstream regulators of Rac1 activation. Cells overexpressing an EBP50 mutant, mimicking serine 347/348 phosphorylation, became refractory to hepatocyte growth factor-induced cell spreading and scattering, which is normally mediated by Rac1 activation. Detachment of cells from the substratum also elicited an increase in EBP50 phosphorylation, apparently due to counteracting activities of PKC and protein phosphastase 2A, which resulted in decreased Rac1 activation and induction of anoikis. Cells overexpressing an EBP50 mutant defective in serine 347/348 phosphorylation did not undergo apoptosis in suspension culture. These studies reveal a signaling cascade in which different phosphorylation states and subcellular localization of EBP50 regulate Rac1 function. Cell Death and Differentiation (2012) 19, 1027-1037; doi:10.1038/cdd.2012.4; published online 3 February 2012