title: PIN1 inhibits apoptosis in hepatocellular carcinoma through modulation of the antiapoptotic function of survivin.
abstract: PIN1, a peptidyl-prolyl-isomerase, binds a specific motif comprising a phosphorylated serine or threonine preceding a proline (p-Ser/Thr-Pro) residue in proteins. Through cis-trans isomerization, it induces conformational changes and modulates functions of many proteins that are involved in cell cycle progression, cell proliferation, and oncogenesis. PIN1 is overexpressed in hepatocellular carcinomas (HCC) and contributes to hepatocarcinogenesis. We investigated the role of PIN1 and the significance of its interaction with the inhibitor of apoptosis protein survivin in evading apoptosis in HCC cells. Using cell line and xenograft models, we determined that PIN1 overexpression inhibits apoptosis through suppression of caspase-3 and caspase-9 activity. In addition, down-regulation of survivin in PIN1-overexpressing cells attenuated the antiapoptotic effect induced by PIN1, suggesting that the inhibition of apoptosis is mediated through PIN1-survivin interaction. Coimmunoprecipitation assays showed that PIN1 interacted with survivin via the phosphorylated Thr34-Pro35 motif and enhanced binding among survivin phosphorylated at Thr34, hepatitis B X-interacting protein (HBXIP), and pro-caspase-9. Taken together, these results suggest that the inhibition of apoptosis by PIN1 in HCC cells is mediated through modulation of the antiapoptotic function of survivin by increasing its binding to pro-caspase-9 via HBXIP. Such functional interaction between PIN1 and survivin may therefore play an important role in hepatocarcinogenesis and chemoresistance.
authors: Division of Haematology and Medical Oncology, Department of Medicine, University of Hong Kong, Queen Mary Hospital, Hong Kong, China.
authors: Chi-Wai
authors: CW
authors: Cheng
authors: Ariel K M
authors: AK
authors: Chow
authors: Roberta
authors: R
authors: Pang
authors: Elaine W S
authors: EW
authors: Fok
authors: Yok-Lam
authors: YL
authors: Kwong
authors: Eric
authors: E
authors: Tse
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D006528:Carcinoma, Hepatocellular / Q000201:enzymology* / Q000473:pathology*; D053453:Caspase 9 / Q000378:metabolism; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D015536:Down-Regulation; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism*; D008113:Liver Neoplasms / Q000201:enzymology* / Q000473:pathology*; D051379:Mice; D008819:Mice, Nude; D008954:Models, Biological; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019696:Peptidylprolyl Isomerase / Q000737:chemistry / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D013347:Subcellular Fractions / Q000378:metabolism; D000077022:Survivin
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C107489:BIRC5 protein, human; D051034:Inhibitor of Apoptosis Proteins; C110719:LAMTOR5 protein, human; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D000077022:Survivin; D053453:Caspase 9; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase; C000606850:Pin1 protein, mouse