Kim Yong-Chul, Gonzalez-Nieves Reyda, Cutler Mary L
Department of Pathology, F. Edward Hebert School of Medicine, Uniformed Services University of the Health Sciences, Rm B3124, 4301 Jones Bridge Road, Bethesda, MD, 20814, USA.
Directorate for Biological Sciences, National Science Foundation, Washington, DC, USA.
J Cell Commun Signal. 2019 Sep;13(3):331-341. doi: 10.1007/s12079-018-00504-4. Epub 2019 Jan 25.
The Rsu1 protein contributes to cell adhesion and migration via its association with the adaptor complex of Integrin linked kinase (ILK), PINCH, and Parvin (IPP), which binds to the cytoplasmic domain of β1 integrins joining integrins to the actin cytoskeleton. Rsu1 binding to PINCH in the IPP complex is required for EGF-induced adhesion, spreading and migration in MCF10A mammary epithelial cells. In addition, Rsu1 expression inhibits Jun kinase but is necessary for the activation of MKK4 and p38 Map kinase signaling essential for migration in MCF10A cells. The data reported here examines the links between MKK4-p38-ATF2 signaling and AKT regulation in MCF10A cells. Ectopic Rsu1 inhibited AKT1 phosphorylation while Rsu1 depletion induced AKT activation and AKT1 phosphorylation of MKK4 on serine 80, blocking MKK4 activity. Rsu1 depletion also reduced the RNA for lipid phosphatase PTEN thus implicating PTEN in modulating levels of activated AKT in these conditions. ChIP analysis of the PTEN promoter revealed that Rsu1 depletion prevented binding of ATF2 to a positive regulatory site in the PTEN promoter and the enhanced binding of cJun to a negatively regulatory PTEN promoter site. These results demonstrate a mechanism by which Rsu1 adhesion signaling alters the balance between MKK4-p38-ATF2 and cJun activation thus altering PTEN expression in MCF10A cells.
Rsu1蛋白通过与整合素连接激酶（ILK）、PINCH和Parvin（IPP）的衔接子复合物结合，促进细胞黏附和迁移，该复合物与β1整合素的胞质结构域结合，将整合素与肌动蛋白细胞骨架相连。在MCF10A乳腺上皮细胞中，EGF诱导的黏附、铺展和迁移需要Rsu1与IPP复合物中的PINCH结合。此外，Rsu1表达抑制Jun激酶，但对于激活MCF10A细胞迁移所必需的MKK4和p38丝裂原活化蛋白激酶信号是必要的。本文报道的数据研究了MCF10A细胞中MKK4 - p38 - ATF2信号与AKT调节之间的联系。异位表达的Rsu1抑制AKT1磷酸化，而Rsu1缺失诱导AKT活化以及MKK4丝氨酸80位点的AKT1磷酸化，从而阻断MKK4活性。Rsu1缺失还降低了脂质磷酸酶PTEN的RNA水平，表明在这些条件下PTEN参与调节活化的AKT水平。PTEN启动子的染色质免疫沉淀分析表明，Rsu1缺失阻止了ATF2与PTEN启动子中一个正调控位点的结合，并增强了cJun与PTEN启动子中一个负调控位点的结合。这些结果证明了一种机制，通过该机制Rsu1黏附信号改变了MKK4 - p38 - ATF2和cJun活化之间的平衡，从而改变了MCF10A细胞中PTEN的表达。
