Abstract
Increased β-catenin transcriptional activity downstream of the Wnt/Wingless signaling pathway has been observed in many human tumors, most notably colorectal carcinomas. However, β-catenin activation is also observed in many human malignancies with no observable Wnt activity. Wnt-independent pathways that activate β-catenin remain undefined, yet have the potential to play a significant role during tumorigenesis. Here, we report that phosphotidylinositol phosphate kinase Iγ (PIPKIγ), an enzyme that generates phosphoinositide messengers in vivo, directly associates with β-catenin and increases β-catenin activity downstream of growth factor stimulation. PIPKIγ expression and kinase activity enhance β-catenin phosphorylation on residues that promote nuclear importation and transcriptional activity. Lastly, we show that β-catenin is required for PIPKIγ-dependent increased cell proliferation. These results reveal a novel mechanism in which PIPKIγ expression and catalytic activity enhance β-catenin nuclear translocation and expression of its target genes to promote tumorigenic phenotypes.
©2011 AACR.
Publication types
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Research Support, N.I.H., Extramural
MeSH terms
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Cadherins / physiology
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Cell Nucleus / metabolism
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Cell Transformation, Neoplastic / drug effects
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Cell Transformation, Neoplastic / genetics
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Cell Transformation, Neoplastic / metabolism
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Gene Expression Regulation, Neoplastic / drug effects
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Gene Knockdown Techniques
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HeLa Cells
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Humans
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Phosphotransferases (Alcohol Group Acceptor) / antagonists & inhibitors
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Phosphotransferases (Alcohol Group Acceptor) / genetics
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Phosphotransferases (Alcohol Group Acceptor) / metabolism
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Phosphotransferases (Alcohol Group Acceptor) / physiology*
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Protein Transport / physiology
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RNA, Small Interfering / pharmacology
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Receptors, Growth Factor / genetics
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Receptors, Growth Factor / metabolism*
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Receptors, Growth Factor / physiology
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Signal Transduction / drug effects
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Signal Transduction / genetics
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Signal Transduction / physiology
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Transcription, Genetic / drug effects
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Transcriptional Activation* / drug effects
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Transcriptional Activation* / physiology
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Transfection
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beta Catenin / metabolism
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beta Catenin / physiology*
Substances
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Cadherins
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RNA, Small Interfering
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Receptors, Growth Factor
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beta Catenin
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Phosphotransferases (Alcohol Group Acceptor)
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1-phosphatidylinositol-4-phosphate 5-kinase