title: Transforming growth factor-beta1 (TGF-beta)-induced apoptosis of prostate cancer cells involves Smad7-dependent activation of p38 by TGF-beta-activated kinase 1 and mitogen-activated protein kinase kinase 3.
abstract: The inhibitory Smad7, a direct target gene for transforming growth factor-beta (TGF-beta), mediates TGF-beta1-induced apoptosis in several cell types. Herein, we report that apoptosis of human prostate cancer PC-3U cells induced by TGF-beta1 or Smad7 overexpression is caused by a specific activation of the p38 mitogen-activated protein kinase pathway in a TGF-beta-activated kinase 1 (TAK1)- and mitogen-activated protein kinase kinase 3 (MKK3)-dependent manner. Expression of dominant negative p38, dominant negative MKK3, or incubation with the p38 selective inhibitor [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole], prevented TGF-beta1-induced apoptosis. The expression of Smad7 was required for TGF-beta-induced activation of MKK3 and p38 kinases, and endogenous Smad7 was found to interact with phosphorylated p38 in a ligand-dependent manner. Ectopic expression of wild-type TAK1 promoted TGF-beta1-induced phosphorylation of p38 and apoptosis, whereas dominant negative TAK1 reduced TGF-beta1-induced phosphorylation of p38 and apoptosis. Endogenous Smad7 was found to interact with TAK1, and TAK1, MKK3, and p38 were coimmunoprecipitated with Smad7 in transiently transfected COS1 cells. Moreover, ectopically expressed Smad7 enhanced the coimmunoprecipitation of HA-MKK3 and Flag-p38, supporting the notion that Smad7 may act as a scaffolding protein and facilitate TAK1- and MKK3-mediated activation of p38.
authors.affiliation: Ludwig Institute for Cancer Research, Biomedical Centre, 75124 Uppsala, Sweden.
authors.forename: Sofia
authors.initials: S
authors.lastname: Edlund
authors.forename: Shizhong
authors.initials: S
authors.lastname: Bu
authors.forename: Norbert
authors.initials: N
authors.lastname: Schuster
authors.forename: Pontus
authors.initials: P
authors.lastname: Aspenström
authors.forename: Rainer
authors.initials: R
authors.lastname: Heuchel
authors.forename: Nils-Erik
authors.initials: NE
authors.lastname: Heldin
authors.forename: Peter
authors.initials: P
authors.lastname: ten Dijke
authors.forename: Carl-Henrik
authors.initials: CH
authors.lastname: Heldin
authors.forename: Maréne
authors.initials: M
authors.lastname: Landström
mesh_terms: D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D019556:COS Cells; D053938:DNA Fragmentation; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005799:Genes, Dominant; D006801:Humans; D020287:In Situ Nick-End Labeling; D048371:MAP Kinase Kinase 3; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D008297:Male; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D010766:Phosphorylation; D011233:Precipitin Tests; D011471:Prostatic Neoplasms / Q000473:pathology*; D011485:Protein Binding; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D051906:Smad7 Protein; D013997:Time Factors; D015534:Trans-Activators / Q000378:metabolism*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000502:physiology*; D053773:Transforming Growth Factor beta1; D014407:Tumor Cells, Cultured; D048051:p38 Mitogen-Activated Protein Kinases; D000099151:MAP Kinase Kinase Kinase 7
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D048371:MAP Kinase Kinase 3; D020930:MAP Kinase Kinase Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D011505:Protein-Tyrosine Kinases; D051906:Smad7 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D048051:p38 Mitogen-Activated Protein Kinases; D000099151:MAP Kinase Kinase Kinase 7; C497806:SMAD7 protein, human; C508960:TGFB1 protein, human; C482530:MAP2K3 protein, human