Activation of TORC1 transcriptional coactivator through MEKK1-induced phosphorylation

Mol Biol Cell. 2008 Nov;19(11):4750-61. doi: 10.1091/mbc.e08-04-0369. Epub 2008 Sep 10.

Abstract

CREB is a prototypic bZIP transcription factor and a master regulator of glucose metabolism, synaptic plasticity, cell growth, apoptosis, and tumorigenesis. Transducers of regulated CREB activity (TORCs) are essential transcriptional coactivators of CREB and an important point of regulation on which various signals converge. In this study, we report on the activation of TORC1 through MEKK1-mediated phosphorylation. MEKK1 potently activated TORC1, and this activation was independent of downstream effectors MEK1/MEK2, ERK2, JNK, p38, protein kinase A, and calcineurin. MEKK1 induced phosphorylation of TORC1 both in vivo and in vitro. Expression of the catalytic domain of MEKK1 alone in cultured mammalian cells sufficiently caused phosphorylation and subsequent activation of TORC1. MEKK1 physically interacted with TORC1 and stimulated its nuclear translocation. An activation domain responsive to MEKK1 stimulation was mapped to amino acids 431-650 of TORC1. As a physiological activator of CREB, interleukin 1alpha triggered MEKK1-dependent phosphorylation of TORC1 and its consequent recruitment to the cAMP response elements in the interleukin 8 promoter. Taken together, our findings suggest a new mechanism for regulated activation of TORC1 transcriptional coactivator and CREB signaling.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calcineurin / metabolism
  • Cell Nucleus / metabolism
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Extracellular Signal-Regulated MAP Kinases / metabolism
  • HeLa Cells
  • Humans
  • Interleukin-8 / genetics
  • JNK Mitogen-Activated Protein Kinases / metabolism
  • MAP Kinase Kinase Kinase 1 / metabolism*
  • Phosphorylation
  • Phosphothreonine / metabolism
  • Promoter Regions, Genetic
  • Protein Binding
  • Protein Structure, Tertiary
  • Protein Transport
  • Trans-Activators / metabolism*
  • Transcription Factors / chemistry
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transcription, Genetic*
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • CRTC1 protein, human
  • Interleukin-8
  • Trans-Activators
  • Transcription Factors
  • Phosphothreonine
  • Cyclic AMP-Dependent Protein Kinases
  • Extracellular Signal-Regulated MAP Kinases
  • JNK Mitogen-Activated Protein Kinases
  • p38 Mitogen-Activated Protein Kinases
  • MAP Kinase Kinase Kinase 1
  • MAP3K1 protein, human
  • Calcineurin