Mammalian Ste20-like kinases 1 and 2 (MST1 and MST2) are activated in NIH3T3 cells exposed to okadaic acid. The Hippo pathway is a newly emerging signaling that functions as a tumor suppressor. MST1 and MST2 work as core kinases of the Hippo pathway and their activities depend on the autophosphorylation, which is negatively regulated by protein phosphatase 2A (PP2A). Okadaic acid has been frequently used to enhance the phosphorylation of MST1 and MST2 and to trigger the activation of the Hippo pathway. However other components of the Hippo pathway could also be targets of okadaic acid. In this review we first briefly summarize the molecular architecture of the Hippo pathway for the reference of researchers outside the field. We explain how MST kinases are regulated by PP2A and how okadaic acid activates MST2. Thereafter we discuss which components of the Hippo pathway are candidate substrates of protein phosphatases and which points we need to consider in the usage of okadaic acid to study the Hippo pathway.
References
[1]
Zhao, B.; Tumaneng, K.; Guan, K.L. The Hippo pathway in organ size control, tissue regeneration and stem cell self-renewal. Nat. Cell Biol. 2011, 13, 877–883, doi:10.1038/ncb2303.
[2]
Bao, Y.; Hata, Y.; Ikeda, M.; Withanage, K. Mammalian Hippo pathway: From development to cancer and beyond. J. Biochem. 2011, 149, 361–379, doi:10.1093/jb/mvr021.
[3]
Ramos, A.; Camargo, F.D. The Hippo signaling pathway and stem cell biology. Trends Cell Biol. 2012, 22, 339–346, doi:10.1016/j.tcb.2012.04.006.
[4]
Varelas, X.; Wrana, J.L. Coordinating developmental signaling: Novel roles for the Hippo pathway. Trends Cell Biol. 2012, 22, 88–96, doi:10.1016/j.tcb.2011.10.002.
[5]
Taylor, L.K.; Wang, H.-C.R.; Erikson, R.L. Newly identified stress-responsive protein kinases, Krs-1 and Krs-2. Proc. Natl. Acad. Sci. USA 1996, 93, 10099–10104, doi:10.1073/pnas.93.19.10099.
[6]
Hong, W.; Guan, K.L. The YAP and TAZ transcription co-activators: Key downstream effectors of the mammalian Hippo pathway. Semin. Cell Dev. Biol. 2012, 23, 785–793, doi:10.1016/j.semcdb.2012.05.004.
[7]
Bao, Y.; Nakagawa, K.; Yang, Z.; Ikeda, M.; Withanage, W.; Ishigami-Yuasa, M.; Okuno, Y.; Hata, S.; Nishina, H.; Hata, Y. A cell-based assay to screen stimulators of the Hippo pathway reveals the inhibitory effect of dobutamine on the YAP-dependent gene transcription. J. Biochem. 2011, 150, 199–208, doi:10.1093/jb/mvr063.
[8]
Yu, F.X.; Zhao, B.; Panupinthu, N.; Jewell, J.L.; Lian, I.; Wang, L.H.; Zhao, J.; Yuan, H.; Tumaneng, K.; Li, H.; et al. Regulation of the Hippo-YAP pathway by G-protein-coupled receptor signaling. Cell 2012, 150, 780–791, doi:10.1016/j.cell.2012.06.037.
[9]
Miller, E.; Yang, J.; DeRan, M.; Wu, C.; Su, A.I.; Bonamy, G.M.; Liu, J.; Peters, E.C.; Wu, X. Identification of serum-derived sphigosine-1-phosphate as a small molecule regulator YAP. Chem. Biol. 2012, 19, 955–962, doi:10.1016/j.chembiol.2012.07.005.
Delpire, E. The mammalian family of sterile 20p-like protein kinases. Pflugers Arch. 2009, 458, 953–967, doi:10.1007/s00424-009-0674-y.
[12]
Radu, M.; Chernoff, J. The DeMSTification of mammalian Ste20 kinases. Curr. Biol. 2009, 19, R421–R425, doi:10.1016/j.cub.2009.04.022.
[13]
O’Neill, E.; Rushworth, L.; Baccarini, M.; Kolch, W. Role of the kinase MST2 in suppression of apoptosis by the proto-oncogene product Raf-1. Science 2004, 306, 2267–2270, doi:10.1126/science.1103233.
[14]
Kilili, G.K.; Kyrias, J.M. Mammalian Ste20-like kinase (Mst2) indirectly supports Raf-1/ERK pathway activity via maintenance of protein phosphatase-2A catalytic subunit levels and consequent suppression of inhibitory Raf-1 phosphorylation. J. Biol. Chem. 2010, 285, 15076–15087, doi:10.1074/jbc.M109.078915.
[15]
Ribeiro, P.S.; Josue, F.; Wepf, A.; Wehr, M.C.; Rinner, O.; Kelly, G.; Tapon, N.; Gstaiger, M. Combined functional genomic and proteomic approaches identify a PP2A complex as a negative regulator of Hippo signaling. Mol. Cell 2010, 39, 521–534, doi:10.1016/j.molcel.2010.08.002.
[16]
Matallanas, D.; Romano, D.; Yee, K.; Meissl, K.; Kucerova, L.; Piazzolla, D.; Baccarini, M.; Vass, J.K.; Kolch, W.; O’Neill, E. RASSF1A elicits apoptosis through an MST2 pathway directing proapoptotic transcription by the p73 tumor suppressor protein. Mol. Cell 2007, 27, 962–975, doi:10.1016/j.molcel.2007.08.008.
[17]
Guo, C.; Zhang, X.; Pfeifer, G.P. The tumor suppressor RASSF1A prevents dephosphorylation of the mammalian STE20-like kinases MST1 and MST2. J. Biol. Chem. 2011, 286, 6253–6261, doi:10.1074/jbc.M110.178210.
[18]
Schlegelmilch, K.; Mohseni, M.; Kirak, O.; Pruszak, J.; Rodriguez, J.R.; Zhou, D.; Kreger, B.T.; Vasioukhin, V.; Avruch, J.; Brummlkamp, T.R.; et al. Yap1 acts downstream of α-catenin to control epidermal proliferation. Cell 2011, 144, 782–795, doi:10.1016/j.cell.2011.02.031.
[19]
Liu, C.-Y.; Lv, X.; Li, T.; Xu, Y.; Zhou, X.; Zhao, S.; Xiong, Y.; Lei, Q.-Y.; Guan, K.-L. PP1 cooperates with ASPP2 to dephosphorylate and activate TAZ. J. Biol. Chem. 2011, 286, 5558–5566.
Bao, Y.; Sumita, K.; Kudo, T.; Withanage, K.; Nakagawa, K.; Ikeda, M.; Ohno, K.; Wang, Y.; Hata, Y. Roles of mammalian sterile 20-like kinase 2-dependent phosphorylations of Mps one binder 1B in the activation of nuclear Dbf2-related kinases. Genes Cells 2009, 14, 1369–1381, doi:10.1111/j.1365-2443.2009.01354.x.
[22]
Hergovich, A. MOB control: Reviewing a conserved family of kinase regulators. Cell Signal. 2011, 23, 1433–1440, doi:10.1016/j.cellsig.2011.04.007.
[23]
Avruch, J.; Zhou, D.; Fitamant, J.; Bardeesy, N.; Mou, F.; Barrufet, L.R. Protein kinases of the Hippo pathway: Regulation and substrates. Semin. Cell Dev. Biol. 2012, 23, 770–784, doi:10.1016/j.semcdb.2012.07.002.
[24]
Moreno, C.S.; Lane, W.S.; Pallas, D.C. A mammalian homolog of yeast MOB1 is both a member and a putative substrate of striatin family-protein phosphatase 2A complexes. J. Biol. Chem. 2001, 276, 24253–24260, doi:10.1074/jbc.M102398200.
[25]
Xiao, L.; Chen, Y.; Ji, M.; Volle, D.J.; Lewis, R.E.; Tsai, M.-Y.; Dong, J. KIBRA protein phosphorylation is regulated by mitotic kinase Aurora and protein phosphatase 1. J. Biol. Chem. 2011, 286, 36304–36315.
[26]
Lee, K.-K.; Yonehara, S. Phosphorylation and dimerization regulate nucleocytoplasmic shuttling of mammalian STE20-like kinase (MST). J. Biol. Chem. 2002, 27, 12351–12358.
[27]
Praskova, M.; Khoklatchev, A.; Ortiz-Vega, S.; Avruch, J. Regulation of the MST1 kinase by autophosphorylation, by the growth inhibitory proteins, RASSF1 and NORE1, and by Ras. Biochem. J. 2004, 381, 453–462, doi:10.1042/BJ20040025.
