Phosphorylation of PP2Ac by PKC is a key regulatory step in the PP2A-switch-dependent AKT dephosphorylation that leads to apoptosis

Guy Nadel, Zhong Yao, Avital Hacohen-Lev-Ran, Ehud Wainstein, Galia Maik-Rachline, Tamar Ziv, Zvi Naor, Arie Admon, Rony Seger*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Although GqPCR activation often leads to cell survival by activating the PI3K/AKT pathway, it was previously shown that in several cell types AKT activity is reduced and leads to JNK activation and apoptosis. The mechanism of AKT inactivation in these cells involves an IGBP1-coupled PP2Ac switch that induces the dephosphorylation and inactivation of both PI3K and AKT. However, the machinery involved in the initiation of PP2A switch is not known. Methods: We used phospho-mass spectrometry to identify the phosphorylation site of PP2Ac, and raised specific antibodies to follow the regulation of this phosphorylation. Other phosphorylations were monitored by commercial antibodies. In addition, we used coimmunoprecipitation and proximity ligation assays to follow protein–protein interactions. Apoptosis was detected by a TUNEL assay as well as PARP1 cleavage using SDS-PAGE and Western blotting. Results: We identified Ser24 as a phosphorylation site in PP2Ac. The phosphorylation is mediated mainly by classical PKCs (PKCα and PKCβ) but not by novel PKCs (PKCδ and PKCε). By replacing the phosphorylated residue with either unphosphorylatable or phosphomimetic residues (S24A and S24E), we found that this phosphorylation event is necessary and sufficient to mediate the PP2A switch, which ultimately induces AKT inactivation, and a robust JNK-dependent apoptosis. Conclusion: Our results show that the PP2A switch is induced by PKC-mediated phosphorylation of Ser24-PP2Ac and that this phosphorylation leads to apoptosis upon GqPCR induction of various cells. We propose that this mechanism may provide an unexpected way to treat some cancer types or problems in the endocrine machinery.

Original languageEnglish
Article number154
JournalCell Communication and Signaling
Volume22
Issue number1
DOIs
StatePublished - Dec 2024

Funding

FundersFunder number
Samuil and Petr Polsky Prostate Cancer Research Fund
Israel Science Foundation

    Keywords

    • Apoptosis
    • JNK
    • PKC
    • PP2A phosphorylation
    • PP2A switch

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