PEA-15 potentiates H-Ras mediated epithelial cell transformation through Phospholipase D

Cancer Biology Program, University of Hawaii Cancer Center, University of Hawaii at Manoa, Honolulu, HI 96813, USA.
Oncogene (Impact Factor: 8.46). 11/2011; 31(30):3547-60. DOI: 10.1038/onc.2011.514
Source: PubMed

ABSTRACT The small GTPase H-Ras is a proto-oncogene that activates a variety of different pathways including the extracellular-signal-regulated kinase (ERK)/mitogen-activated protein kinase pathway. H-Ras is mutated in many human malignancies, and these mutations cause the protein to be constitutively active. Phosphoprotein enriched in astrocytes, 15 kDa (PEA-15) blocks ERK-dependent gene transcription and inhibits proliferation by sequestering ERK in the cytoplasm. We therefore investigated whether PEA-15 influences H-Ras-mediated transformation. We found that PEA-15 does not block H-Ras-activated proliferation when H-Ras is constitutively active. We show instead that in H-Ras-transformed mouse kidney epithelial cells, co-expression of PEA-15 resulted in enhanced soft agar colony growth and increased tumor growth in vivo. Overexpression of both H-Ras and PEA-15 resulted in accelerated G1/S cell cycle transition and increased activation of the ERK signaling pathway. PEA-15 mediated these effects through activation of its binding partner phospholipase D1 (PLD1). Inhibition of PLD1 or interference with PEA-15/PLD1 binding blocked PEA-15's ability to increase ERK activation. Our findings reveal a novel mechanism by which PEA-15 positively regulates Ras/ERK signaling and increases the proliferation of H-Ras-transformed epithelial cells through enhanced PLD1 expression and activation. Thus, our work provides a surprising mechanism by which PEA-15 augments H-Ras-driven transformation. These data reveal that PEA-15 not only suppresses ERK signaling and tumorigenesis but also alternatively enhances tumorigenesis in the context of active Ras.

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Available from: Dirk Geerts, Sep 26, 2015
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    • "This binding occurs in the N-terminal of PEA-15 which contains a D-peptide-binding motif targeted by protein which contain a D-motif including enzymes such as PLD1 (Viparelli et al., 2008). This interaction is not dependent on the phosphorylation state of PEA-15 (Sulzmaier et al., 2012b). Studies have demonstrated that PLD1 activity is increased when PEA-15 is present, and this is via elevated PLD1 expression (a potential effect on increased PLD1 protein stability) (Zhang et al., 2000). "
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    ABSTRACT: Phosphoprotein enriched in astrocytes-15 (PEA-15) is a cytoplasmic protein that sits at an important junction in intracellular signalling and can regulate diverse cellular processes, such as proliferation and apoptosis, dependent upon stimulation. Regulation of these processes occurs by virtue of the unique interaction of PEA-15 with other signalling proteins. PEA-15 acts as a cytoplasmic tether for the mitogen-activated protein kinases, extracellular signal-regulated kinase 1/2 (ERK1/2) preventing nuclear localisation. In order to release ERK1/2, PEA-15 requires to be phosphorylated via several potential pathways. PEA-15 (and its phosphorylation state) therefore regulates many ERK1/2-dependent processes, including proliferation, via regulating ERK1/2 nuclear translocation. In addition, PEA-15 contains a death effector domain (DED) which allows interaction with other DED-containing proteins. PEA-15 can bind the DED-containing apoptotic adaptor molecule, Fas-associated death domain protein (FADD) which is also dependent on the phosphorylation status of PEA-15. PEA-15 binding of FADD can inhibit apoptosis as bound FADD cannot participate in the assembly of apoptotic signalling complexes. Through these protein-protein interactions, PEA-15-regulated cellular effects have now been investigated in a number of disease-related studies. Changes in PEA-15 expression and regulation have been observed in diabetes mellitus, cancer, neurological disorders and the cardiovascular system. These changes have been suggested to contribute to the pathology related to each of these disease states. As such, new therapeutic targets based around PEA-15 and its associated interactions are now being uncovered and could provide novel avenues for treatment strategies in multiple diseases.
    Pharmacology [?] Therapeutics 03/2014; 143(3). DOI:10.1016/j.pharmthera.2014.03.006 · 9.72 Impact Factor
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    • "It was found that PLD2 binds to Ras and acts as a GEF, which can cause increased cell growth (Henkels et al., 2013b). Ras signaling was due to increased PLD1 activity which was the result of phosphoprotein enriched in astrocytes 15 kDa (PEA-15) expression (Sulzmaier et al., 2012). PEA-15 promotes G1-to S-phase transition in cells. "
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    ABSTRACT: Phospholipase D (PLD) is a membrane protein with a double role: maintenance of the structural integrity of cellular or intracellular membranes and involvement in cell signaling through the product of the catalytic reaction, PA, and through protein-protein interaction with a variety of partners. Cross-talk during PLD signaling occurs with other cancer regulators (Ras, PDGF, TGF and kinases). Elevation of either PLD1 or PLD2 (the two mammalian isoforms of PLD) is able to transform fibroblasts and contribute to cancer progression. Elevated total PLD activity, as well as overexpression, is present in a wide variety of cancers such as gastric, colorectal, renal, stomach, esophagus, lung and breast. PLD provides survival signals and is involved in migration, adhesion and invasion of cancer cells, and all are increased during PLD upregulation or, conversely, they are decreased during PLD loss of function. Eventhough the end results of PLD action as relates to downstream signaling mechanisms are still currently being elucidated, invasion, a pre-requisite for metastasis, is directly affected by PLD. This review will introduce the classical mammalian PLD's, PLD1 and PLD2, followed by the mechanisms of intracellular regulation and a status of current investigation in the crucial involvement of PLD in cancer, mostly through its role in cell migration, invasion and metastasis, that has grown exponentially in the last few years.
    09/2013; 54(1). DOI:10.1016/j.jbior.2013.08.006
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    ABSTRACT: Abnormal ERK signaling is implicated in many human diseases including cancer. This signaling cascade is a good target for the therapy of certain malignancies because of its important role in regulating cell proliferation and survival. The small phosphoprotein PEA-15 is a potent regulator of the ERK signaling cascade, and, by acting on this pathway, has been described to have both tumor-suppressor and tumor-promoter functions. However, the exact mechanism by which PEA-15 drives the outcome one way or the other remains unclear. We propose that the cellular environment is crucial in determining PEA-15 protein function by affecting the protein's phosphorylation state. We hypothesize that only unphosphorylated PEA-15 can act as a tumor-suppressor and that phosphorylation alters the interaction with binding partners to promote tumor development. In order to use PEA-15 as a prognostic marker or therapeutic target it is therefore important to evaluate its phosphorylation status.
    Small GTPases 07/2012; 3(3):173-7. DOI:10.4161/sgtp.20021
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