Dephosphorylation and inactivation of Akt/PKB is counteracted by protein kinase CK2 in HEK 293T cells |
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Authors: | Giovanni Di Maira Francesca Brustolon Lorenzo A Pinna Maria Ruzzene |
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Institution: | (1) Department of Biological Chemistry and CNR Neuroscience Institute, University of Padova, Viale G. Colombo, 3, 35131 Padova, Italy;(2) VIMM (Venetian Institute of Molecular Medicine), 35131 Padova, Italy; |
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Abstract: | Akt (PKB) is a critical kinase in cell-survival pathways. Its activity depends on the phosphorylation of Thr308 and Ser473,
by PDK1 and mTORC2, respectively. We found that Akt can be further stimulated through phosphorylation of Ser129 by another
kinase, CK2. Here we show that phosphorylation of Akt at Ser129 also facilitates its association with Hsp90 chaperone, thus
preventing Thr308 dephosphorylation. This is supported by the following observations: (1) phospho-Thr308 decreases when Ser129
is mutated to alanine, (2) this decrease is abolished by cell treatment with okadaic acid (to inactivate PP2A) or geldanamycin
(to inactivate Hsp90), (3) phosphorylation of Ser129 neither enhances the activity of PDK1 nor hampers the in vitro activity
of PP2A on Thr308, but increases the Hsp90 association to Akt. These data support the view that the antiapoptotic potential
of CK2 is at least in part mediated by its ability to maintain Akt in its active form. |
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