CDK1 phosphorylation of TAZ in mitosis inhibits its oncogenic activity

Abstract

The transcriptional co-activator with PDZ-binding motif (TAZ) is a downstream effector of the Hippo tumor suppressor pathway, which plays important roles in cancer and stem cell biology. Hippo signaling inactivates TAZ through phosphorylation (mainly at S89). In the current study, we define a new layer of regulation of TAZ activity that is critical for its oncogenic function. We found that TAZ is phosphorylated in vitro and in vivo by the mitotic kinase CDK1 at S90, S105, T326, and T346 during the G2/M phase of the cell cycle. Interestingly, mitotic phosphorylation inactivates TAZ oncogenic activity, as the non-phosphorylatable mutant (TAZ-S89A/S90A/S105A/T326A/T346A, TAZ-5A) possesses higher activity in epithelial-mesenchymal transition, anchorage-independent growth, cell migration, and invasion when compared to the TAZ-S89A mutant. Accordingly, TAZ-5A has higher transcriptional activity compared to the TAZ-S89A mutant. Finally, we show that TAZ-S89A or TAZ-5A (to a greater extent) was sufficient to induce spindle and centrosome defects, and chromosome misalignment/missegregation in immortalized epithelial cells. Together, our results reveal a previously unrecognized connection between TAZ oncogenicity and mitotic phospho-regulation.

Ajuba Phosphorylation by CDK1 Promotes Cell Proliferation and Tumorigenesis

“…As expected, the mobility of KIBRA, YAP, and TAZ were all significantly retarded due to phosphorylation during G2/M arrest (Fig. 1A) (12,15,30,31). Taxol or Nocodazole treatment did not cause any evident change in the mobility/phosphorylation for PTPN14, NF2, or EX (which are all upstream regulators of the Hippo-YAP pathway), for WW45 or TEAD1 (Fig.…”

“…Interestingly, we also found that several Hippo core members (Lats1, Lats2, and Mst2) (Fig. 1) or their upstream regulator (KIBRA) (30,31) or downstream effectors (YAP and TAZ) (12,13,15) are phosphorylated during mitosis. Importantly, mitotic phosphorylation is critical for their oncogenic or tumor suppressive functions (12,13,15).…”

“…1) or their upstream regulator (KIBRA) (30,31) or downstream effectors (YAP and TAZ) (12,13,15) are phosphorylated during mitosis. Importantly, mitotic phosphorylation is critical for their oncogenic or tumor suppressive functions (12,13,15). These observations suggest that in addition to their expression levels, the phosphorylation status of these proteins must also be finely controlled, adding another layer of regulation for Hippo-YAP activity during tumorigenesis.…”

“…This core kinase signaling subsequently phosphorylates and inactivates the downstream effectors, oncoproteins YAP and TAZ, by sequestering them in the cytoplasm and promoting ubiquitination-dependent degradation (5). During past years, many regulators and input signals have been identified that influence Hippo-YAP signaling activity, such as the cell polarity and adherens junctions proteins, mechanical force, actin cytoskeleton (6 -8), hypoxia (9), energy stress (10,11), and mitosis/cytokinesis stress (12)(13)(14)(15). The downstream effectors YAP/TAZ also cross-talk with, or function as, mediators of many other signaling pathways, such as the G-protein coupled receptor, Wnt/␤-catenin, TGF-␤/SMAD, EGF, Notch, Hedgehog, and KRas/MAPK pathways (16).…”

“…We have shown that KIBRA (an upstream regulator of the Hippo pathway) (30,31), YAP (12, 13), and TAZ (15) are phosphorylated by mitotic kinases. Importantly, mitotic phosphorylation of YAP/ TAZ is critical for proper mitotic progression and for their oncogenic activity in cancer cells (12,13,15). These studies prompted us to further examine whether other components or regulators of the Hippo pathway are regulated by phosphorylation during mitosis.…”