Lee Hae Kyung, Finniss Susan, Cazacu Simona, Xiang Cunli, Poisson Laila M, Blumberg Peter M, Brodie Chaya
Davidson Laboratory of Cell Signaling and Tumorigenesis, Department of Neurosurgery, Hermelin Brain Tumor Center, Henry Ford Hospital, Detroit, MI, USA.
Hermelin Brain Tumor Center, Henry Ford Hospital, Detroit, MI, USA.
Oncotarget. 2015 Jan 30;6(3):1850-64. doi: 10.18632/oncotarget.2575.
Glioblastoma (GBM), the most aggressive primary brain tumors, are highly infiltrative. Although GBM express high Ras activity and Ras proteins have been implicated in gliomagenesis, Ras-activating mutations are not frequent in these tumors. RasGRP3, an important signaling protein responsive to diacylglycerol (DAG), increases Ras activation. Here, we examined the expression and functions of RasGRP3 in GBM and glioma cells. RasGRP3 expression was upregulated in GBM specimens and glioma stem cells compared with normal brains and neural stem cells, respectively. RasGRP3 activated Ras and Rap1 in glioma cells and increased cell migration and invasion partially via Ras activation. Using pull-down assay and mass spectroscopy we identified the actin-related protein, Arp3, as a novel interacting protein of RasGRP3. The interaction of RasGRP3 and Arp3 was validated by immunofluorescence staining and co-immunoprecipitation, and PMA, which activates RasGRP3 and induces its translocation to the peri-nuclear region, increased the association of Arp3 and RasGRP3. Arp3 was upregulated in GBM, regulated cell spreading and migration and its silencing partially decreased these effects of RasGRP3 in glioma cells. In summary, RasGRP3 acts as an important integrating signaling protein of the DAG and Ras signaling pathways and actin polymerization and represents an important therapeutic target in GBM.
胶质母细胞瘤（GBM）是最具侵袭性的原发性脑肿瘤，具有高度浸润性。尽管GBM表现出高Ras活性，且Ras蛋白与胶质瘤发生有关，但Ras激活突变在这些肿瘤中并不常见。RasGRP3是一种对二酰甘油（DAG）有反应的重要信号蛋白，可增加Ras激活。在此，我们研究了RasGRP3在GBM和胶质瘤细胞中的表达及功能。与正常脑和神经干细胞相比，RasGRP3在GBM标本和胶质瘤干细胞中的表达分别上调。RasGRP3在胶质瘤细胞中激活Ras和Rap1，并部分通过Ras激活增加细胞迁移和侵袭。通过下拉实验和质谱分析，我们鉴定出肌动蛋白相关蛋白Arp3是RasGRP3的一种新型相互作用蛋白。RasGRP3与Arp3的相互作用通过免疫荧光染色和免疫共沉淀得到验证，激活RasGRP3并诱导其转位至核周区域的佛波酯（PMA）增加了Arp3与RasGRP3的结合。Arp3在GBM中上调，调节细胞铺展和迁移，其沉默部分降低了RasGRP3在胶质瘤细胞中的这些作用。总之，RasGRP3作为DAG和Ras信号通路以及肌动蛋白聚合的重要整合信号蛋白，是GBM中的一个重要治疗靶点。
