Akt is efficiently activated by PIF-pocket- and PtdIns(3,4,5)P-3-dependent mechanisms leading to resistance to PDK1 inhibitors

Ayaz Najafov, Natalia Shpiro, Dario R. Alessi

    Research output: Contribution to journalArticle

    45 Citations (Scopus)

    Abstract

    Mutations leading to inappropriate activation of Akt isoforms contribute to proliferation and survival of a significant proportion of human cancers. Akt is activated by phosphorylation of its T-loop residue (Thr308) by PDK1 (3-phosphoinositide-dependent kinase-1) and its C-terminal hydrophobic motif (Ser473) by mTORC2 [mTOR (mammalian target of rapamycin) complex 2]. Potent PDK1 inhibitors such as GSK2334470 have recently been elaborated as potential anti-cancer agents. However, these compounds were surprisingly ineffective at suppressing Akt activation. In the present study we demonstrate that resistance to PDK1 inhibitors results from Akt being efficiently recruited to PDK1 via two alternative mechanisms. The first involves ability of Akt and PDK1 to mutually interact with the PI3K (phosphoinositide 3-kinase) second messenger PtdIns(3,4,5)P3. The second entails recruitment of PDK1 to Akt after its phosphorylation at Ser473 by mTORC2, via a substrate-docking motif termed the PIF-pocket. We find that disruption of either the PtdIns(3,4,5)P3 or the Ser473 phosphorylation/PIF- pocket mechanism only moderately impacts on Akt activation, but induces marked sensitization to PDK1 inhibitors. These findings suggest that suppression of Ser473 phosphorylation by using mTOR inhibitors would disrupt the PIF-pocket mechanism and thereby sensitize Akt to PDK1 inhibitors. Consistent with this, we find combing PDK1 and mTOR inhibitors reduced Akt activation to below basal levels andmarkedly inhibited proliferation of all of the cell lines tested. Our results suggest further work is warranted to explore the utility of combining PDK1 and mTOR inhibitors as a therapeutic strategy for treatment of cancers that harbour mutations elevating Akt activity.

    Original languageEnglish
    Pages (from-to)285-295
    Number of pages11
    JournalBiochemical Journal
    Volume448
    Issue number2
    DOIs
    Publication statusPublished - Dec 2012

    Fingerprint

    3-Phosphoinositide-Dependent Protein Kinases
    Phosphatidylinositols
    Phosphorylation
    Chemical activation
    Neoplasms
    Mutation
    1-Phosphatidylinositol 4-Kinase
    Second Messenger Systems
    Ports and harbors
    Protein Isoforms

    Cite this

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    title = "Akt is efficiently activated by PIF-pocket- and PtdIns(3,4,5)P-3-dependent mechanisms leading to resistance to PDK1 inhibitors",
    abstract = "Mutations leading to inappropriate activation of Akt isoforms contribute to proliferation and survival of a significant proportion of human cancers. Akt is activated by phosphorylation of its T-loop residue (Thr308) by PDK1 (3-phosphoinositide-dependent kinase-1) and its C-terminal hydrophobic motif (Ser473) by mTORC2 [mTOR (mammalian target of rapamycin) complex 2]. Potent PDK1 inhibitors such as GSK2334470 have recently been elaborated as potential anti-cancer agents. However, these compounds were surprisingly ineffective at suppressing Akt activation. In the present study we demonstrate that resistance to PDK1 inhibitors results from Akt being efficiently recruited to PDK1 via two alternative mechanisms. The first involves ability of Akt and PDK1 to mutually interact with the PI3K (phosphoinositide 3-kinase) second messenger PtdIns(3,4,5)P3. The second entails recruitment of PDK1 to Akt after its phosphorylation at Ser473 by mTORC2, via a substrate-docking motif termed the PIF-pocket. We find that disruption of either the PtdIns(3,4,5)P3 or the Ser473 phosphorylation/PIF- pocket mechanism only moderately impacts on Akt activation, but induces marked sensitization to PDK1 inhibitors. These findings suggest that suppression of Ser473 phosphorylation by using mTOR inhibitors would disrupt the PIF-pocket mechanism and thereby sensitize Akt to PDK1 inhibitors. Consistent with this, we find combing PDK1 and mTOR inhibitors reduced Akt activation to below basal levels andmarkedly inhibited proliferation of all of the cell lines tested. Our results suggest further work is warranted to explore the utility of combining PDK1 and mTOR inhibitors as a therapeutic strategy for treatment of cancers that harbour mutations elevating Akt activity.",
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    year = "2012",
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    doi = "10.1042/BJ20121287",
    language = "English",
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    Akt is efficiently activated by PIF-pocket- and PtdIns(3,4,5)P-3-dependent mechanisms leading to resistance to PDK1 inhibitors. / Najafov, Ayaz; Shpiro, Natalia; Alessi, Dario R.

    In: Biochemical Journal, Vol. 448, No. 2, 12.2012, p. 285-295.

    Research output: Contribution to journalArticle

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    AU - Najafov, Ayaz

    AU - Shpiro, Natalia

    AU - Alessi, Dario R.

    N1 - MEDLINE® is the source for the MeSH terms of this document.

    PY - 2012/12

    Y1 - 2012/12

    N2 - Mutations leading to inappropriate activation of Akt isoforms contribute to proliferation and survival of a significant proportion of human cancers. Akt is activated by phosphorylation of its T-loop residue (Thr308) by PDK1 (3-phosphoinositide-dependent kinase-1) and its C-terminal hydrophobic motif (Ser473) by mTORC2 [mTOR (mammalian target of rapamycin) complex 2]. Potent PDK1 inhibitors such as GSK2334470 have recently been elaborated as potential anti-cancer agents. However, these compounds were surprisingly ineffective at suppressing Akt activation. In the present study we demonstrate that resistance to PDK1 inhibitors results from Akt being efficiently recruited to PDK1 via two alternative mechanisms. The first involves ability of Akt and PDK1 to mutually interact with the PI3K (phosphoinositide 3-kinase) second messenger PtdIns(3,4,5)P3. The second entails recruitment of PDK1 to Akt after its phosphorylation at Ser473 by mTORC2, via a substrate-docking motif termed the PIF-pocket. We find that disruption of either the PtdIns(3,4,5)P3 or the Ser473 phosphorylation/PIF- pocket mechanism only moderately impacts on Akt activation, but induces marked sensitization to PDK1 inhibitors. These findings suggest that suppression of Ser473 phosphorylation by using mTOR inhibitors would disrupt the PIF-pocket mechanism and thereby sensitize Akt to PDK1 inhibitors. Consistent with this, we find combing PDK1 and mTOR inhibitors reduced Akt activation to below basal levels andmarkedly inhibited proliferation of all of the cell lines tested. Our results suggest further work is warranted to explore the utility of combining PDK1 and mTOR inhibitors as a therapeutic strategy for treatment of cancers that harbour mutations elevating Akt activity.

    AB - Mutations leading to inappropriate activation of Akt isoforms contribute to proliferation and survival of a significant proportion of human cancers. Akt is activated by phosphorylation of its T-loop residue (Thr308) by PDK1 (3-phosphoinositide-dependent kinase-1) and its C-terminal hydrophobic motif (Ser473) by mTORC2 [mTOR (mammalian target of rapamycin) complex 2]. Potent PDK1 inhibitors such as GSK2334470 have recently been elaborated as potential anti-cancer agents. However, these compounds were surprisingly ineffective at suppressing Akt activation. In the present study we demonstrate that resistance to PDK1 inhibitors results from Akt being efficiently recruited to PDK1 via two alternative mechanisms. The first involves ability of Akt and PDK1 to mutually interact with the PI3K (phosphoinositide 3-kinase) second messenger PtdIns(3,4,5)P3. The second entails recruitment of PDK1 to Akt after its phosphorylation at Ser473 by mTORC2, via a substrate-docking motif termed the PIF-pocket. We find that disruption of either the PtdIns(3,4,5)P3 or the Ser473 phosphorylation/PIF- pocket mechanism only moderately impacts on Akt activation, but induces marked sensitization to PDK1 inhibitors. These findings suggest that suppression of Ser473 phosphorylation by using mTOR inhibitors would disrupt the PIF-pocket mechanism and thereby sensitize Akt to PDK1 inhibitors. Consistent with this, we find combing PDK1 and mTOR inhibitors reduced Akt activation to below basal levels andmarkedly inhibited proliferation of all of the cell lines tested. Our results suggest further work is warranted to explore the utility of combining PDK1 and mTOR inhibitors as a therapeutic strategy for treatment of cancers that harbour mutations elevating Akt activity.

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