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.
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.
From the Department of Biochemistry, Hallym University College of Medicine, Chuncheon, Kangwon-Do 200-702, Korea.
Hee-Jun
HJ
Kim
Jae-Gyu
JG
Kim
Mi-Young
MY
Moon
Seol-Hye
SH
Park
Jae-Bong
JB
Park
D000818:Animals; D002460:Cell Line; D002465:Cell Movement / Q000502:physiology; D018925:Chemokines / Q000096:biosynthesis / Q000235:genetics; D004789:Enzyme Activation / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology; D006801:Humans; D051550:I-kappa B Kinase / Q000235:genetics / Q000378:metabolism*; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D016328:NF-kappa B / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation / Q000502:physiology; D017434:Protein Structure, Tertiary; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha / Q000502:physiology; D054460:rho-Associated Kinases / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
C569638:ARHGDIA protein, human; D018925:Chemokines; C491731:IKBKG protein, human; D047908:Intracellular Signaling Peptides and Proteins; C514981:NEMO protein, mouse; D016328:NF-kappa B; D053773:Transforming Growth Factor beta1; D062948:rho Guanine Nucleotide Dissociation Inhibitor alpha; C066737:RHOA protein, human; D054460:rho-Associated Kinases; D051550:I-kappa B Kinase; C526380:RhoA protein, mouse; D020741:rho GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein
Cell Migration; Inflammation; NF-kB Transcription Factor; Rhoa; Transforming Growth Factor Beta (TGFbeta)