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Regulation of MTK1/MEKK4 kinase activity by its N-terminal autoinhibitory domain and GADD45 binding

Hiroaki Mita1, Junichiro Tsutsui, Mutsuhiro Takekawa

  • 1Dana-Farber Cancer Institute and Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115, USA.

Molecular and Cellular Biology
|June 8, 2002
PubMed

Insights

Cellular stress activates p38 and JNK pathways via MTK1. GADD45 proteins bind MTK1, relieving autoinhibition and activating downstream kinases for stress response.

Area of Science:

  • Cellular biology
  • Molecular signaling
  • Stress response pathways

Background:

  • Cellular stresses activate stress-responsive mitogen-activated protein (MAP) kinases, including p38 and JNK.
  • MTK1 (MEKK4) is a MAP kinase kinase kinase that mediates the activation of both p38 and JNK pathways.

Purpose of the Study:

  • To elucidate the activation mechanism of the human MAP kinase kinase kinase, MTK1.
  • To identify factors that regulate MTK1 activity in cellular stress responses.

Main Methods:

  • Functional complementation screening in yeast cells to identify MTK1 activators.
  • Site-directed mutagenesis to generate constitutively active MTK1 mutants.
  • Analysis of MTK1 kinase activity and substrate interaction (MKK6) in yeast and mammalian cells.

Main Results:

  • MTK1 possesses an autoinhibitory domain (residues 253-553) in its N-terminal noncatalytic region, rendering it inactive in full-length form.
  • GADD45 proteins (alpha, beta, gamma) were identified as novel MTK1 activators that bind near the inhibitory domain and relieve autoinhibition.
  • Constitutively active MTK1 mutants were generated, capable of interacting with MKK6 independently of GADD45 binding.

Conclusions:

  • MTK1 activity is regulated by autoinhibition mediated by its N-terminal domain.
  • GADD45 proteins play a crucial role in MTK1 activation, linking cellular stress signals to p38 and JNK pathways.
  • Understanding MTK1 regulation provides insights into stress signaling and potential therapeutic targets.

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