Phospholipase D1 drives a positive feedback loop to reinforce the Wnt/beta-catenin/TCF signaling axis.
Activation of the Wnt signaling pathway occurs frequently in human cancers, but an understanding of the targets and regulation of this important pathway remains incomplete. In this study, we report that phospholipase D (PLD), a cell survival mediator that is upregulated in cancer, is an important target of the Wnt signaling pathway that functions in a positive feedback loop to reinforce pathway output. PLD1 expression and activity was enhanced by treatment with Wnt3a and glycogen synthase kinase-3 inhibitors, and the Wnt pathway-regulated transcription factors beta-catenin and TCF-4 were required for this effect. Three functional TCF-4-binding sites were identified within the PLD1 promoter. Interestingly, suppressing PLD1 blocked the ability of beta-catenin to transcriptionally activate PLD1 and other Wnt target genes by preventing beta-catenin/TCF-4 complex formation. Conversely, tactics to elevate intracellular levels of phosphatidic acid, the product of PLD1 enzyme activity, enhanced beta-catenin/TCF-4 complex formation as well as beta-catenin-dependent TCF transcriptional activity. In cell-based assays, PLD1 was necessary for the anchorage-independent growth driven by Wnt/beta-catenin signaling, whereas beta-catenin/TCF-4 was necessary for the anchorage-independent growth driven by PLD1 activation. Taken together, our findings define a function for PLD1 in a positive feedback loop of Wnt/beta-catenin/TCF-4 signaling that provides new mechanistic insights into cancer, with implications of novel strategies to disrupt Wnt signaling in cancer.
Kang
Dong Woo
DW
Department of Molecular Biology, College of Natural Science, Pusan National University, Busan, Republic of Korea.
Lee
Soung-Hoon
SH
Yoon
Jeong Whan
JW
Park
Won-Sang
WS
Choi
Kang-Yell
KY
Min
Do Sik
do S
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors / Q000235:genetics* / Q000378:metabolism; D015153:Blotting, Western; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002465:Cell Movement; D049109:Cell Proliferation; D047369:Chromatin Immunoprecipitation; D025461:Feedback, Physiological; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D047468:Immunoprecipitation; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D010739:Phospholipase D / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D000073940:Transcription Factor 4; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism*; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism*
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D012333:RNA, Messenger; C532096:TCF4 protein, human; D000073940:Transcription Factor 4; D014157:Transcription Factors; C555510:WNT3A protein, human; D051153:Wnt Proteins; D060508:Wnt3 Protein; D060509:Wnt3A Protein; D051176:beta Catenin; D010739:Phospholipase D; C106801:phospholipase D1