Abstract
Phosphorylation of proteins on serine or threonine residues that immediately precede proline (pSer/Thr-Pro) is specifically catalyzed by the peptidyl-prolyl cis-trans isomerase Pin1 and is a central signaling mechanism in cell proliferation and transformation. Although Pin1 is frequently overexpressed in hepatocellular carcinoma (HCC), the molecular mechanism of Pin1 in HCC has not been completely elucidated. Here, we show that Pin1 interacts with p70S6K in vitro and ex vivo. Overexpression of Pin1 resulted in enhanced p70S6K phosphorylation induced by insulin in SK-HEP-1 cells. In contrast, Pin1(-/-) mouse embryonic fibroblasts (MEFs) exhibited significantly decreased insulin-induced p70S6K phosphorylation compared with Pin1(+/+) MEFs. Furthermore, Pin1 enhanced the insulin-induced extracellular signal-regulated protein kinase (ERK)1/2 phosphorylation through its interaction with p70S6K, whereas the inhibition of p70S6K activity by rapamycin suppressed insulin-induced ERK1/2 phosphorylation in SK-HEP-1 cells. Hence, Pin1 affected activator protein-1 activity through p70S6K-ERK1/2 signaling in SK-HEP-1 cells. Most importantly, Pin1-overexpressing JB6 Cl41 cells enhanced neoplastic cell transformation promoted by insulin much more than green fluorescent protein-overexpressing JB6 Cl41 control cells. These results imply that Pin1 amplifies insulin signaling in hepatocarcinoma cells through its interaction with p70S6K, suggesting that Pin1 plays an important role in insulin-induced tumorigenesis and is a potential therapeutic target in hepatocarcinoma.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Animals
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Antineoplastic Agents / pharmacology
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Carcinoma, Hepatocellular / drug therapy
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Carcinoma, Hepatocellular / metabolism
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Carcinoma, Hepatocellular / pathology
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Cell Transformation, Neoplastic*
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Cells, Cultured
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Drug Synergism
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Embryo, Mammalian / cytology
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Embryo, Mammalian / drug effects
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Embryo, Mammalian / metabolism
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Fibroblasts / cytology
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Fibroblasts / metabolism
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Gene Expression Regulation, Neoplastic
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Green Fluorescent Proteins / metabolism
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Humans
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Hypoglycemic Agents / pharmacology*
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Immunoblotting
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Immunosuppressive Agents / pharmacology
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Insulin / pharmacology*
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Liver Neoplasms, Experimental / drug therapy
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Liver Neoplasms, Experimental / metabolism
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Liver Neoplasms, Experimental / pathology
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Mice
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Mice, Knockout
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Mitogen-Activated Protein Kinase 1 / metabolism
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Mitogen-Activated Protein Kinase 3 / metabolism
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NIMA-Interacting Peptidylprolyl Isomerase
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Naphthoquinones / pharmacology
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Peptidylprolyl Isomerase / antagonists & inhibitors
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Peptidylprolyl Isomerase / metabolism*
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Phosphorylation / drug effects
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RNA, Small Interfering / pharmacology
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Ribosomal Protein S6 Kinases, 70-kDa / antagonists & inhibitors
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Ribosomal Protein S6 Kinases, 70-kDa / genetics
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Ribosomal Protein S6 Kinases, 70-kDa / metabolism*
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Signal Transduction
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Sirolimus / pharmacology
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Transcription Factor AP-1 / metabolism*
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Two-Hybrid System Techniques
Substances
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Antineoplastic Agents
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Hypoglycemic Agents
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Immunosuppressive Agents
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Insulin
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NIMA-Interacting Peptidylprolyl Isomerase
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Naphthoquinones
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RNA, Small Interfering
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Transcription Factor AP-1
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enhanced green fluorescent protein
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Green Fluorescent Proteins
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Ribosomal Protein S6 Kinases, 70-kDa
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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PIN1 protein, human
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Peptidylprolyl Isomerase
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Pin1 protein, mouse
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Sirolimus
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juglone