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Tumor necrosis factor-receptor-associated factor-4 is a positive regulator of transforming growth factor-beta

Tuzer Kalkan1, Yasuno Iwasaki, Chong Yon Park

  • 1Graduate Program in Molecular and Cellular Biology and Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, NY 11794, USA.

Molecular Biology of the Cell
|May 22, 2009
PubMed

Insights

Tumor necrosis factor receptor-associated factor-4 (TRAF4) is identified as a new target of Smurf1, a ubiquitin ligase. Smurf1 targets TRAF4 for degradation, regulating bone morphogenetic protein (BMP) and Nodal signaling crucial for neural crest development.

Area of Science:

  • Cell Biology
  • Developmental Biology
  • Molecular Signaling

Background:

  • Transforming growth factor-beta (TGF-beta) superfamily signaling is vital for cellular processes and development.
  • Smurf ubiquitin ligases regulate TGF-beta superfamily pathways by degrading key signaling proteins like Smads.
  • Tumor necrosis factor (TNF)-receptor-associated factors (TRAFs) typically mediate innate immunity signaling.

Purpose of the Study:

  • To identify novel targets and functions of Smurf1.
  • To investigate the role of TRAF4 in TGF-beta superfamily signaling.
  • To elucidate the developmental functions of TRAF4 in neural crest formation.

Main Methods:

  • Ubiquitin ligase assays to identify Smurf1 targets.
  • Western blotting and small interfering RNA (siRNA) knockdown in human embryonic kidney 293 cells to assess protein regulation.
  • Xenopus laevis embryo manipulation (mRNA knockdown and overexpression) to study developmental roles.
  • Analysis of gene expression patterns during embryonic development.

Main Results:

  • TRAF4 is identified as a novel substrate of Smurf1, undergoing polyubiquitylation and proteasomal degradation.
  • TRAF4 enhances bone morphogenetic protein (BMP) and Nodal signaling, distinct from other TRAF family members.
  • TRAF4 is maternally expressed in Xenopus eggs and localized to key developmental regions, including the neural plate and neural crest.
  • TRAF4 knockdown in Xenopus embryos impairs neural crest development and neural folding.
  • Smurf1 knockdown in human cells increases endogenous TRAF4 levels, confirming Smurf1-mediated regulation.

Conclusions:

  • TRAF4 acts as a Smurf1-regulated positive mediator of BMP and Nodal signaling.
  • TRAF4 plays an essential role in neural crest development and neural plate morphogenesis.
  • This study uncovers a new function for TRAF4 in developmental signaling pathways, distinct from its canonical roles in immunity.

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