title: TRB3 interacts with SMAD3 promoting tumor cell migration and invasion.
abstract: Tribbles homolog 3 (TRB3, also known as TRIB3, NIPK and SKIP3), a human homolog of Drosophila Tribbles, has been found to interact with a variety of signaling molecules to regulate diverse cellular functions. Here, we report that TRB3 is a novel SMAD3-interacting protein. Expression of exogenous TRB3 enhanced the transcriptional activity of SMAD3, whereas knocking down endogenous TRB3 reduced the transcriptional activity of SMAD3. The kinase-like domain (KD) of TRB3 was responsible for the interaction with SMAD3 and the regulation of SMAD3-mediated transcriptional activity. In addition, TGF-β1 stimulation or overexpression of SMAD3 enhanced the TRB3 promoter activity and expression, suggesting that there is a positive feedback loop between TRB3 and TGF-β-SMAD3 signaling. Mechanistically, TRB3 was found to trigger the degradation of SMAD ubiquitin regulatory factor 2 (Smurf2), which resulted in a decrease in the degradation of SMAD2 and phosphorylated SMAD3. Moreover, TRB3-SMAD3 interaction promoted the nuclear localization of SMAD3 because of the interaction of TRB3 with the MH2 domain of SMAD3. These effects of TRB3 were responsible for potentiating the SMAD3-mediated activity. Furthermore, knockdown of endogenous TRB3 expression inhibited the migration and invasion of tumor cells in vitro, which were associated with an increase in the expression of E-cadherin and a decrease in the expression of Twist-1 and Snail, two master regulators of epithelial-to-mesenchymal transition, suggesting a crucial role for TRB3 in maintaining the mesenchymal status of tumor cells. These results demonstrate that TRB3 acts as a novel SMAD3-interacting protein to participate in the positive regulation of TGF-β-SMAD-mediated cellular biological functions.
authors: Molecular Immunology and Pharmacology Laboratory, State Key Laboratory of Bioactive Substances and Functions of Natural Medicines, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, 1 Xian Nong Tan Street, Beijing, 100050, P R China.
authors: Fang
authors: F
authors: Hua
authors: Rong
authors: R
authors: Mu
authors: Jinwen
authors: J
authors: Liu
authors: Jianfei
authors: J
authors: Xue
authors: Ziyan
authors: Z
authors: Wang
authors: Heng
authors: H
authors: Lin
authors: Hongzhen
authors: H
authors: Yang
authors: Xiaoguang
authors: X
authors: Chen
authors: Zhuowei
authors: Z
authors: Hu
mesh_terms: D000199:Actins / Q000378:metabolism; D015820:Cadherins / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002465:Cell Movement; D002467:Cell Nucleus / Q000378:metabolism; D058750:Epithelial-Mesenchymal Transition; D055785:Gene Knockdown Techniques; D017930:Genes, Reporter; D056945:Hep G2 Cells; D006801:Humans; D049410:Luciferases, Renilla / Q000096:biosynthesis / Q000235:genetics; D009361:Neoplasm Invasiveness; D011401:Promoter Regions, Genetic; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism* / Q000037:antagonists & inhibitors; D021381:Protein Transport; D059748:Proteolysis; D034622:RNA Interference; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000378:metabolism*; D015533:Transcriptional Activation; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism
chemical_list: D000199:Actins; D015820:Cadherins; D018797:Cell Cycle Proteins; D012097:Repressor Proteins; C497790:SMAD3 protein, human; D051900:Smad3 Protein; C474831:TRIB3 protein, human; D049410:Luciferases, Renilla; C471641:SMURF2 protein, human; D044767:Ubiquitin-Protein Ligases; D017346:Protein Serine-Threonine Kinases