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Osmotic stress activates the TAK1-JNK pathway while blocking TAK1-mediated NF-kappaB activation: TAO2 regulates TAK1

Wei-Chun Huangfu1, Emily Omori, Shizuo Akira

  • 1Department of Environmental and Molecular Toxicology, North Carolina State University, Raleigh, North Carolina 27695, USA.

The Journal of Biological Chemistry
|August 9, 2006
PubMed

Insights

Osmotic stress activates stress-activated protein kinases (SAPKs). Transforming growth factor-beta-activated kinase 1 (TAK1) regulates JNK activation, but TAO2 protein specifically inhibits TAK1

Area of Science:

  • Cellular Biology
  • Molecular Signaling
  • Stress Response Pathways

Background:

  • Osmotic stress triggers mitogen-activated protein kinases (MAPKs), including JNK and p38, crucial for cellular defense.
  • Transforming growth factor-beta-activated kinase 1 (TAK1), a MAPKKK, activates JNK and p38, and also IKK, leading to NF-kappaB activation.

Purpose of the Study:

  • To investigate the specific role of TAK1 in osmotic stress-induced signaling.
  • To elucidate the mechanism by which TAK1 activity is modulated during osmotic stress.
  • To identify proteins that regulate TAK1 function in response to osmotic stress.

Main Methods:

  • Investigated TAK1 activation and downstream signaling (JNK, p38, IKK, NF-kappaB) under osmotic stress.
  • Screened for TAK1-binding proteins using biochemical assays.
  • Assessed the effect of identified binding proteins on TAK1-mediated signaling pathways.

Main Results:

  • TAK1 is essential for osmotic stress-induced JNK activation but not exclusively for p38 activation.
  • Despite high activation by osmotic stress, TAK1 did not activate IKK or NF-kappaB.
  • TAO2 (thousand-and-one amino acid kinase 2) binds TAK1, inhibiting NF-kappaB activation but not JNK activation.
  • TAO2 interferes with TAK1-IKK interaction, suggesting a regulatory role.

Conclusions:

  • TAK1 activity is specifically modulated during osmotic stress to activate JNK while inhibiting IKK/NF-kappaB pathways.
  • TAO2 acts as a negative regulator of TAK1, specifically preventing IKK activation.
  • This TAO2-mediated regulation allows for distinct signaling outcomes specific to osmotic stress responses.

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