Moon Sungho, Kim Wantae, Kim Soyoung, Kim Youngeun, Song Yonghee, Bilousov Oleksii, Kim Jiyoung, Lee Taebok, Cha Boksik, Kim Minseong, Kim Hanjun, Katanaev Vladimir L, Jho Eek-Hoon
Department of Life Science, University of Seoul, Seoul, Korea.
Department of Pharmacology and Toxicology, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
EMBO Rep. 2017 Jan;18(1):61-71. doi: 10.15252/embr.201642683. Epub 2016 Dec 15.
Hippo signaling controls organ size by regulating cell proliferation and apoptosis. Yes-associated protein (YAP) is a key downstream effector of Hippo signaling, and LATS-mediated phosphorylation of YAP at Ser127 inhibits its nuclear localization and transcriptional activity. Here, we report that Nemo-like kinase (NLK) phosphorylates YAP at Ser128 both in vitro and in vivo, which blocks interaction with 14-3-3 and enhances its nuclear localization. Depletion of NLK increases YAP phosphorylation at Ser127 and reduces YAP-mediated reporter activity. These results suggest that YAP phosphorylation at Ser128 and at Ser127 may be mutually exclusive. We also find that with the increase in cell density, nuclear localization and the level of NLK are reduced, resulting in reduction in YAP phosphorylation at Ser128. Furthermore, knockdown of Nemo (the Drosophila NLK) in fruit fly wing imaginal discs results in reduced expression of the Yorkie (the Drosophila YAP) target genes expanded and DIAP1, while Nemo overexpression reciprocally increased the expression. Overall, our data suggest that NLK/Nemo acts as an endogenous regulator of Hippo signaling by controlling nuclear localization and activity of YAP/Yorkie.
河马信号通路通过调节细胞增殖和凋亡来控制器官大小。Yes相关蛋白（YAP）是河马信号通路的关键下游效应器，LATS介导的YAP在Ser127处的磷酸化会抑制其核定位和转录活性。在此，我们报告Nemo样激酶（NLK）在体外和体内均会使YAP在Ser128处磷酸化，这会阻断其与14-3-3的相互作用并增强其核定位。NLK的缺失会增加YAP在Ser127处的磷酸化，并降低YAP介导的报告基因活性。这些结果表明，YAP在Ser128和Ser127处的磷酸化可能相互排斥。我们还发现，随着细胞密度的增加，NLK的核定位和水平会降低，导致YAP在Ser128处的磷酸化减少。此外，在果蝇翅成虫盘中介导Nemo（果蝇NLK）的敲低会导致Yorkie（果蝇YAP）靶基因expanded和DIAP1的表达降低，而Nemo的过表达则会使表达相反地增加。总体而言，我们的数据表明NLK/Nemo通过控制YAP/Yorkie的核定位和活性，作为河马信号通路的内源性调节因子。
