Nuclear localization and pro-apoptotic signaling of YAP2 require intact PDZ-binding motif.

The Hippo signaling pathway regulates the intrinsic size of organs by controlling two opposing processes, proliferation and apoptosis. The nuclear effector of this pathway is Yes kinase-associated protein (YAP) which is a WW domain-containing transcriptional co-activator. In addition to WW domains, YAP2 has a Post-synaptic density, Discs large, Zonula occludens-1 (PDZ)-binding motif that is located at its COOH terminus. To determine whether the localization of YAP2 in cells is PDZ-binding motif dependent, we generated a delta C mutant of YAP2 lacking the five most COOH terminal amino acids, -FLTWL, which constitute a well-conserved PDZ-binding motif. We report here that the PDZ-binding motif is necessary for YAP2 localization in the nucleus, for the stabilization of p73, and for promoting apoptosis of HEK293 cells maintained at low concentration of serum. We suggest that an unknown PDZ domain-containing protein (or proteins) functions as a shuttle, facilitating YAP2 translocation from the cytoplasm to the nucleus. Since the Hippo pathway acts as a tumor suppressor pathway, the PDZ complex of YAP represents a potential target of cancer therapy.