IκB kinase γ/nuclear factor-κB-essential modulator (IKKγ/NEMO) facilitates RhoA GTPase activation, which, in turn, activates Rho-associated KINASE (ROCK) to phosphorylate IKKβ in response to transforming growth factor (TGF)-β1

J Biol Chem. 2014 Jan 17;289(3):1429-40. doi: 10.1074/jbc.M113.520130. Epub 2013 Nov 16.

Abstract

Transforming growth factor (TGF)-β1 plays several roles in a variety of cellular functions. TGF-β1 transmits its signal through Smad transcription factor-dependent and -independent pathways. It was reported that TGF-β1 activates NF-κB and RhoA, and RhoA activates NF-κB in several kinds of cells in a Smad-independent pathway. However, the activation molecular mechanism of NF-κB by RhoA upon TGF-β1 has not been clearly elucidated. We observed that RhoA-GTP level was increased by TGF-β1 in RAW264.7 cells. RhoA-GDP and RhoGDI were bound to N- and C-terminal domains of IKKγ, respectively. Purified IKKγ facilitated GTP binding to RhoA complexed with RhoGDI. Furthermore, Dbs, a guanine nucletotide exchange factor of RhoA much more enhanced GTP binding to RhoA complexed with RhoGDI in the presence of IKKγ. Indeed, si-IKKγ abolished RhoA activation in response to TGF-β1 in cells. However, TGF-β1 stimulated the release of RhoA-GTP from IKKγ and Rho-associated kinase (ROCK), an active RhoA effector protein, directly phosphorylated IKKβ in vitro, whereas TGF-β1-activated kinase 1 activated RhoA upon TGF-β1 stimulation. Taken together, our data indicate that IKKγ facilitates RhoA activation via a guanine nucletotide exchange factor, which in turn activates ROCK to phosphorylate IKKβ, leading to NF-κB activation that induced the chemokine expression and cell migration upon TGF-β1.

Keywords: Cell Migration; Inflammation; NF-kB Transcription Factor; Rhoa; Transforming Growth Factor Beta (TGFbeta).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Cell Movement / physiology
  • Chemokines / biosynthesis
  • Chemokines / genetics
  • Enzyme Activation / physiology
  • Gene Expression Regulation / physiology
  • Humans
  • I-kappa B Kinase / genetics
  • I-kappa B Kinase / metabolism*
  • Intracellular Signaling Peptides and Proteins / genetics
  • Intracellular Signaling Peptides and Proteins / metabolism*
  • Mice
  • NF-kappa B / genetics
  • NF-kappa B / metabolism
  • Phosphorylation / physiology
  • Protein Structure, Tertiary
  • Transforming Growth Factor beta1 / genetics
  • Transforming Growth Factor beta1 / metabolism*
  • rho GTP-Binding Proteins / genetics
  • rho GTP-Binding Proteins / metabolism*
  • rho Guanine Nucleotide Dissociation Inhibitor alpha / physiology
  • rho-Associated Kinases / genetics
  • rho-Associated Kinases / metabolism*
  • rhoA GTP-Binding Protein / genetics
  • rhoA GTP-Binding Protein / metabolism*

Substances

  • ARHGDIA protein, human
  • Chemokines
  • IKBKG protein, human
  • Intracellular Signaling Peptides and Proteins
  • NEMO protein, mouse
  • NF-kappa B
  • Transforming Growth Factor beta1
  • rho Guanine Nucleotide Dissociation Inhibitor alpha
  • RHOA protein, human
  • rho-Associated Kinases
  • I-kappa B Kinase
  • RhoA protein, mouse
  • rho GTP-Binding Proteins
  • rhoA GTP-Binding Protein