Study of mechanisms which control the mitosis entry and progress

 Thierry LORCA and Anna CASTRO

 CRBM - UMR 5237

 1919, route de Mende, 34293 Montpellier

Phones: +33 4 34 35 95 56

            + 33 4 34 35 95 58

Emails: thierry.lorca@crbm.cnrs.fr

            anna.castro@crbm.cnrs.fr

Website

To date, it was assumed that protein phosphorylation/dephosphoryaltion required for mitotic entry/exit was the direct consequence of the activation/inactivation of the mitotic kinase cyclin B-Cdk1. Our laboratory has recently demonstrated that besides cyclin B-Cdk1, the phosphatase PP2A must be also tightly regulated to promote a correct mitosis. Our results show that the Greatwall kinase (Gwl) promotes mitotic entry by inhibiting PP2A, the phosphatase that dephosphorylates cyclin B-Cdk1 substrates. Little is known about the mechanisms controlling Gwl activity and about the substrates of this kinase. We have recently characterized Arpp19 and ENSA as the two first substrates of Gwl that, once phosphorylated by this kinase, bind and inhibit PP2A. However, only Arpp19 is required for mitosis. By using two different models Xenopus egg extracts and human cells in culture we will study the mechanisms controlling Gwl and Arpp19 activities during mitosis. Either the regulation of these two proteins by post-translational modifications or by protein-protein interaction will be tested. We will also address the identification of the role of ENSA during cell cycle. Finally we will investigate whether a miss-regulation of this pathway can be involved in tumorogenesis.

Keywords: Greatwall, Arpp19, ENSA, PP2A, Mitosis

Main publications

• Ma S, Vigneron S, Robert P, Strub JM, Cianferani S, Castro A* and Lorca T*. Greatwall dephosphorylation and inactivation upon mitotic exit is triggered by PP1, (2016), J. Cell Sci. 129 : 1329-1339.
• Vera J, Lartigue L, Vigneron S, Gadea G, Gire V, Del Rio M, Soubeyran I, Chibon F, Lorca T*, Castro A*. Greatwall promotes cell transformation by hyperactivating AKT in human malignancies. (2015)  Elife. pii: e10115.
• McCloy RA, Parker BL, Rogers S, Chaudhuri R, Gayevskiy V, Hoffman NJ, Ali N, Watkins DN, Daly RJ, James DE, Lorca T, Castro A, Burgess A. Global Phosphoproteomic Mapping of Early Mitotic Exit in Human Cells Identifies Novel Substrate Dephosphorylation Motifs. (2015) Mol Cell Proteomics. 14 :2194-2212.
• Álvarez-Fernández M, Sánchez-Martínez R, Sanz-Castillo B, Gan PP, Sanz-Flores M, Trakala M, Ruiz-Torres M, Lorca T, Castro A, and Malumbres M Greatwall is essential to prevent mitotic collapse after nuclear envelope breakdown in mammals (2013). Proc Natl Acad Sci U 22;110(43):17374-9.
• Juanes MA, Khoueiry R, Kupka T, Castro A, Mudrak I, Ogris E, Lorca T and Piatti S. Budding yeast Greatwall and Endosulfines control activity and spatial regulation of PP2ACdc55 for timely mitotic progression (2013), Plos Genetics e1003575.
• Lorca T* and Castro A*. The Greatwall kinase: a new pathway in the control of the cell cycle. (2013) Oncogene, 32(5): 537-43.
• Lorca T* and Castro A*. Deciphering the New Role of the Greatwall/PP2A Pathway in Cell Cycle Control. (2012) Genes Cancer 3(11-12) 712-20.
• Vigneron S, Gharbi-Ayachi A, Raymond AA, Burgess A, Labbé JC, Labesse G, Monsarrat B, Lorca T* and Castro A*. Characterization of the mechanisms controlling Greatwall activity. (2011) Mol Cell Biol. 31(11):2262-75.
• Gharbi-Ayachi A., Labbé JC., Burgess A.,  Vigneron S., Strub JM.,  Brioudes E., Van-Dorsselaer A., Castro A. * and Lorca T*. The Greatwall substrate Arpp19 controls mitosis by inhibiting PP2A. Science (2010) 17:1673-7.
• Burgess A., Vigneron S., Brioudes, E., Labbé JC., Lorca T*. and Castro A*. Loss of human Greatwall results in multiple mitotic defects due to deregulation of the cyclin B-Cdc2/PP2A balance. P.N.A.S 107: 12564-12569.

          * Co-corresponding authors.