title: Endofin, a FYVE domain protein, interacts with Smad4 and facilitates transforming growth factor-beta signaling.
abstract: Transforming growth factor-beta (TGF-beta) signaling is facilitated by scaffold proteins such as SARA (Smad anchor for receptor activation). Endofin, a member of the FYVE domain protein family, has been suggested to regulate membrane trafficking. In this study, we report that endofin functions as a scaffold protein to facilitate TGF-beta signaling. Overexpression of endofin FYVE domain-deletion mutants inhibited TGF-beta-induced expression of CAGA-luciferase. Knockdown of endogenous endofin expression by RNA interference specifically led to reduction of the transcriptional responses of TGF-beta, but had no effect on BMP- or Wnt1-induced reporter expression. Furthermore, in endofin small interfering RNA-expressing stable cells, TGF-beta-mediated expression of plasminogen activator inhibitor-1 and p21(Cip1) was significantly reduced, and TGF-beta-promoted apoptosis was also impaired. We further showed that endofin could interact with Smad4 and TGF-beta type I receptors. Reduction of endogenous endofin expression resulted in a decrease of TGF-beta-induced Smad2 phosphorylation and Smad2-Smad4 complex formation. Together, our findings suggest that endofin facilitates TGF-beta signaling as a scaffold protein to promote the R-Smad-Smad4 complex formation by bringing Smad4 to the proximity of the receptor complex.
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China. Electronic address: ygchen@tsinghua.edu.cn.
authors.forename: Ye-Guang
authors.initials: YG
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Ma
authors.affiliation: State Key Laboratory of Biomembrane and Membrane Biotechnology, Department of Biological Sciences and Biotechnology, Tsinghua University, Beijing 100084, China.
authors.forename: Long
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Medicine and Biological Chemistry, College of Medicine, University of California, Irvine, California 92697.
authors.forename: Zhongxian
authors.initials: Z
authors.lastname: Lu
mesh_terms: D045744:Cell Line, Tumor; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism* / Q000502:physiology; D017434:Protein Structure, Tertiary; D012697:Serine Endopeptidases / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D051901:Smad4 Protein / Q000378:metabolism* / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta; C116420:ZFYVE16 protein, human; D012697:Serine Endopeptidases