title: Regulation of fibronectin by thyroid hormone receptors.
abstract: Thyroid hormones regulate growth, development, differentiation, and metabolic processes by interacting with and activating thyroid hormone receptors and associated pathways. We investigated the triiodothyronine (T3) modulation of gene expression, in human hepatocellular carcinoma cell lines, via a PCR-based cDNA subtraction method. Here we present further data on one of the T3-upregulated genes, fibronectin (FN). We demonstrate that the induction of FN protein expression by T3 in TRalpha1 and TRbeta1 over-expressing cells was time and dose-dependent at the mRNA and protein levels. Blockade of protein synthesis by cycloheximide almost completely inhibited the concomitant induction of FN mRNA by T3, indicating that T3 indirectly regulates FN. Furthermore, nuclear-run on and FN promoter assay clearly can specifically increase the number of FN transcriptional demonstrated that the presence of T3 initiations. In addition, we further confirmed that the up-regulation of FN by T3 was mediated, at least in part, by transforming growth factor-beta (TGF-beta), because the induction of FN was blocked in a dose-dependent manner by the addition of TGF-beta neutralizing antibody. In an effort to elucidate the we demonstrated the involvement of the signaling pathways involved in the activation of FN by T3, mitogen activated protein kinase/c-Jun N-terminal kinase/p38 MAPK (MAPK/JNK/p38) pathway. Although T3 induces the expression of TGF-beta, neither wild-type nor dominant-negative Smad3 or Smad4 over-expression affected the activation of FN by T3. Thus, we demonstrate that T3 regulates FN gene expression indirectly at the transcriptional level, with the participation of the MAPK/JNK/p38 pathway and the TGF-beta signaling pathway but independent of Smad3/4.
authors.affiliation: Department of Biochemistry, Chang-Gung University, Taoyuan, Taiwan, Republic of China. khlin@mail.cgu.edu.tw
authors.forename: Kwang-Huei
authors.initials: KH
authors.lastname: Lin
authors.forename: Chia-yu
authors.initials: CY
authors.lastname: Chen
authors.forename: Shen-Liang
authors.initials: SL
authors.lastname: Chen
authors.forename: Chun-Che
authors.initials: CC
authors.lastname: Yen
authors.forename: Ya-Hui
authors.initials: YH
authors.lastname: Huang
authors.forename: Chung-hsuan
authors.initials: CH
authors.lastname: Shih
authors.forename: Jiann-Jong
authors.initials: JJ
authors.lastname: Shen
authors.forename: Rong-Chi
authors.initials: RC
authors.lastname: Yang
authors.forename: Chia-Siu
authors.initials: CS
authors.lastname: Wang
mesh_terms: D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005353:Fibronectins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051900:Smad3 Protein; D051901:Smad4 Protein; D037021:Thyroid Hormone Receptors alpha / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D037042:Thyroid Hormone Receptors beta / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000187:drug effects / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D014284:Triiodothyronine / Q000378:metabolism / Q000494:pharmacology; D014407:Tumor Cells, Cultured
chemical_list: D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D005353:Fibronectins; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; D051900:Smad3 Protein; D051901:Smad4 Protein; D037021:Thyroid Hormone Receptors alpha; D037042:Thyroid Hormone Receptors beta; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D014284:Triiodothyronine; D003513:Cycloheximide; D020928:Mitogen-Activated Protein Kinases