Li Zheng-Wei, Zhu Yun-Rong, Zhou Xiao-Zhong, Zhuo Bao-Biao, Wang Xiao-Dong
The Center of Diagnosis and Treatment for Children's Bone Diseases, The Children's Hospital Affiliated to Soochow University, Suzhou, China.
Department of Orthopedics, The Affiliated Jiangyin Hospital of Medical College of Southeast University, Jiangyin City, China.
Oncotarget. 2017 Apr 18;8(16):26424-26433. doi: 10.18632/oncotarget.15477.
Forced-activation of AMP-activated protein kinase (AMPK) can possibly inhibit osteoblastoma cells. Here, we aim to provoke AMPK activation via microRNA silencing its phosphatase Ppm1e (protein phosphatase Mg2+/Mn2+-dependent 1e). We showed that microRNA-135b-5p ("miR-135b-5p"), the anti-Ppm1e microRNA, was significantly downregulated in human osteoblastoma tissues. It was correlated with Ppm1e upregulation and AMPKα1 de-phosphorylation. Forced-expression of miR-135b-5p in human osteoblastoma cells (MG-63 and U2OS lines) silenced Ppm1e, and induced a profound AMPKα1 phosphorylation (at Thr-172). Osteoblastoma cell proliferation was inhibited after miR-135b-5p expression. Intriguingly, Ppm1e shRNA knockdown similarly induced AMPKα1 phosphorylation, causing osteoblastoma cell proliferation. Reversely, AMPKα1 shRNA knockdown or dominant negative mutation almost abolished miR-135b-5p's actions in osteoblastoma cells. Further in vivo studies demonstrated that U2OS tumor growth in mice was dramatically inhibited after expressing miR-135b-5p or Ppm1e shRNA. Together, our results suggest that miR-135b-induced Ppm1e silence induces AMPK activation to inhibit osteoblastoma cell proliferation.
激活蛋白激酶（AMPK）的强制激活可能会抑制成骨细胞瘤细胞。在此，我们旨在通过微小RNA沉默其磷酸酶Ppm1e（镁离子/锰离子依赖性蛋白磷酸酶1e）来激发AMPK的激活。我们发现，抗Ppm1e微小RNA——微小RNA-135b-5p（“miR-135b-5p”）在人成骨细胞瘤组织中显著下调。它与Ppm1e上调和AMPKα1去磷酸化相关。在人成骨细胞瘤细胞（MG-63和U2OS细胞系）中强制表达miR-135b-5p可使Ppm1e沉默，并诱导深度的AMPKα1磷酸化（在苏氨酸172位点）。miR-135b-5p表达后，成骨细胞瘤细胞增殖受到抑制。有趣的是，Ppm1e的短发夹RNA（shRNA）敲低同样诱导了AMPKα1磷酸化，导致成骨细胞瘤细胞增殖。相反，AMPKα1的shRNA敲低或显性负突变几乎消除了miR-135b-5p在成骨细胞瘤细胞中的作用。进一步的体内研究表明，在小鼠中表达miR-135b-5p或Ppm1e shRNA后，U2OS肿瘤生长受到显著抑制。总之，我们的结果表明，miR-135b诱导的Ppm1e沉默可诱导AMPK激活，从而抑制成骨细胞瘤细胞增殖。
