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Prohibitin regulates TGF-beta induced apoptosis as a downstream effector of Smad-dependent and -independent signaling.

BACKGROUND: Prohibitin (PHB), a protein located on the inner mitochondrial membrane and nuclei, is an intracellular effector of transforming growth factor-beta (TGF-beta) signaling in prostate cancer cells. This study investigated the involvement of PHB in the apoptosis and survival outcomes of human prostate cancer cell to TGF-beta. shRNA PHB loss of function in prostate cancer cells led to enhanced apoptotic response to TGF-beta via Smad-dependent mechanism. METHOD: TGF-beta activation of Raf-Erk intracellular signaling, led to PHB phosphorylation, decreased inner mitochondrial permeability, and increased cell survival. Calcein-based immunofluorescence studies revealed the functional involvement of PHB in maintaining inner mitochondrial membrane permeability as an integral component of TGF-beta induced apoptosis in prostate cancer cells. RESULTS: These finding indicates that induction of TGF-beta apoptosis is mediated by Smad-dependent and Smad-independent signaling (MAPK) converging at PHB as a downstream effector regulating inner mitochondrial permeability. Putative PHB associated proteins were identified by subjecting TGF-beta treated cells to immunoprecipitation with anti-PHB, and mass spectrometry. A screen for the kinase specific phosphorylation sites of PHB revealed three protein kinase (PKC) binding sites. CONCLUSION: Our results demonstrate that TGF-beta led to upregulation of the PKC inhibitor 14-3-3 protein and promoted its association with PHB, while PHB association with PKC-delta, was inhibited by the MEK1 inhibitor, documenting a critical interdependence between the MEK-ERK signaling and prohibitin phosphorylation. These findings suggest a dual role for PHB as a downstream determinant of the cellular response to TGF-beta via Smad-dependent pathway (apoptosis) and MAPK intracellular signaling (survival).

Pubmed ID: 19725029

Authors

  • Zhu B
  • Zhai J
  • Zhu H
  • Kyprianou N

Journal

The Prostate

Publication Data

January 1, 2010

Associated Grants

  • Agency: NCRR NIH HHS, Id: 1P20RR020171-010005
  • Agency: NIDDK NIH HHS, Id: DK53525-09
  • Agency: NCRR NIH HHS, Id: P20 RR020171
  • Agency: NCRR NIH HHS, Id: P20 RR020171-010005
  • Agency: NCRR NIH HHS, Id: P20 RR020171-020005
  • Agency: NCRR NIH HHS, Id: P20 RR020171-037551
  • Agency: NCRR NIH HHS, Id: P20 RR020171-057026
  • Agency: NIDDK NIH HHS, Id: R01 DK053525
  • Agency: NIDDK NIH HHS, Id: R01 DK053525-07
  • Agency: NIDDK NIH HHS, Id: R01 DK083761

Mesh Terms

  • Amino Acid Sequence
  • Apoptosis
  • Cell Line, Tumor
  • Down-Regulation
  • Humans
  • MAP Kinase Signaling System
  • Male
  • Mitochondrial Membranes
  • Molecular Sequence Data
  • Permeability
  • Repressor Proteins
  • Smad Proteins
  • Transforming Growth Factor beta