Phosphorylation of tumour suppressor Amotl2 by IKBKE kinase promotes YAP1 signalling, enhancing glioblastoma growth

Gaochao Guo, Yan Sun, Rujun Hong, Yalin Lu, Xingjie Chen, Liming Zhao, Chaoyue Li, Yang Liu, Qiang Huang

Inhibitor of nuclear factor kappa-B kinase subunit epsilon (IKBKE), a member of the serine/threonine kinase family, is an important oncogene in glioblastoma. IKBKE is involved in the progression of multiple tumours in glioblastoma (GBM), including tumour invasion, migration, and proliferation. Here, we report an IKBKE–angiomotin-like protein 2 (Amotl2)–yes-associated protein 1 (YAP1) axis in which IKBKE inhibits the protein expression of Amotl2, while Amotl2 regulates the nuclear transport of the YAP1 protein, which has been implicated in brain tumour development and progression. Data analysis of multiple IKBKE mRNA databases of glioma and immunohistochemical analysis of a tissue chip indicated that higher IKBKE expression was associated with higher malignancy and shorter survival in glioma patients. IKBKE downregulation significantly inhibited GBM cell proliferation and restrained tumour growth in a GBM mouse model. Moreover, IKBKE phosphorylates Amotl2, promoting Amotl2 ubiquitination and degradation, leading to YAP1 entry into the nucleus and the activation of downstream genes. In summary, our results are the first to show that IKBKE phosphorylates Amotl2 and that GBM cell proliferation is regulated by the IKBKE↑–Amotl2↓–YAP1↑ axis.