Negative regulator of Yorkie (Yki) in the Hippo/SWH (Sav/Wts/Hpo) signaling pathway that plays a pivotal role in organ size control and tumor suppression by restricting proliferation and promoting apoptosis. The core of this pathway is composed of a kinase cascade wherein Hippo (Hpo), in complex with its regulatory protein Salvador (Sav), phosphorylates and activates Warts (Wts) in complex with its regulatory protein Mats, which in turn phosphorylates and inactivates the Yorkie (Yki) oncoprotein. The Hippo/SWH signaling pathway inhibits the activity of the transcriptional complex formed by Scalloped (sd) and Yki and the target genes of this pathway include cyclin-E (cycE), diap1 and bantam. Inhibits nuclear localization of Yki. Regulates salivary gland degradation in a PI3K-dependent manner and Yki- and Sd-independent, mechanism. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with yki. Interacts with jub. Colocalizes with mats and cyclin E at the centrosome. Belongs to the protein kinase superfamily. AGC Ser/Thr protein kinase family.