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

• Published in: The Journal of biological chemistry Vol. 289; no. 3; pp. 1429 - 1440
• Main Authors: Kim, Hee-Jun, Kim, Jae-Gyu, Moon, Mi-Young, Park, Seol-Hye, Park, Jae-Bong
• Format: Journal Article
• Language: English
• Published: United States American Society for Biochemistry and Molecular Biology 17.01.2014
• Subjects: 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; 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; Signal Transduction; Transforming Growth Factor beta1 - genetics; Transforming Growth Factor beta1 - metabolism; Cell Migration; Transforming Growth Factor Beta (TGFbeta); Inflammation; NF-kB Transcription Factor; Rhoa
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.520130

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.