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

Abstract

The small GTPase H-Ras is a proto-oncogene that activates a variety of different pathways including the extracellular-signal-regulated kinase mitogen-activated protein kinase (ERK/MAPK) pathway. H-Ras is mutated in many human malignancies and these mutations cause the protein to be constitutively active. 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 can alternatively enhance tumorigenesis in the context of active Ras.

PEA15 Regulates the DNA Damage-Induced Cell Cycle Checkpoint and Oncogene-Directed Transformation

“…A previous study reported that PEA15 enhanced the growth of RAS-transformed mouse kidney epithelial cells (45). However, there are many differences between that study and the experiments described here.…”

Phospholipase D Signaling Pathways and Phosphatidic Acid as Therapeutic Targets in Cancer

“…PEA15 overexpressed in epithelial cells that express constitutively active Ras is hyperphosphorylated at S116 and the overexpression potentiates Ras-mediated transformation. Interestingly, disruption of the PEA15/PLD1 complex or PLD1 enzyme inhibition with butanol or smallmolecule PLD inhibitors blocks the PEA15 potentiation of Ras-mediated tumorigenesis, suggesting that the PEA15 enhancement of PLD activity in this system drives ERK activation and anchorage-independent growth downstream of Ras (Sulzmaier et al, 2012). These studies strongly suggest that PLD and PtdOH transduce the signals required for Ras-induced oncogenesis, potentially through downstream activation of Raf and the MAPK pathway.…”

FGFR2 signaling underlies p63 oncogenic function in squamous cell carcinoma

“…This analysis also uncovered a functional signature associated with Ras/MAPK signaling, involving genes including Dusp6, Egr1, and Etv4, and Pld1 (Table 1 and Figure 3C). Notably, this transcriptional program has not been previously ascribed to p63, but may contribute to p63 function in SCC, given that each of these genes has functional links to RAS/MAPK pathway activation in cancer (41,42). A third p63-dependent transcriptional program emerging from this analysis involved genes associated with FGF signaling, including Fgfr2 and Fgfr3 (Table 1 and Figure 3C).…”