Negative regulation of NADPH oxidase 4 by hydrogen peroxide-inducible clone 5 (Hic-5) protein.
Hydrogen peroxide-inducible clone 5 (Hic-5) is a focal adhesion adaptor protein induced by the profibrotic cytokine TGF-β1. We have demonstrated previously that TGF-β1 induces myofibroblast differentiation and lung fibrosis by activation of the reactive oxygen species-generating enzyme NADPH oxidase 4 (Nox4). Here we investigated a potential role for Hic-5 in regulating Nox4, myofibroblast differentiation, and senescence. In normal human diploid fibroblasts, TGF-β1 induces Hic-5 expression in a delayed manner relative to the induction of Nox4 and myofibroblast differentiation. Hic-5 silencing induced constitutive Nox4 expression and enhanced TGF-β1-inducible Nox4 levels. The induction of constitutive Nox4 protein in Hic-5-silenced cells was independent of transcription and translation and controlled by the ubiquitin-proteasomal system. Hic-5 associates with the ubiquitin ligase Cbl-c and the ubiquitin-binding protein heat shock protein 27 (HSP27). The interaction of these proteins is required for the ubiquitination of Nox4 and for maintaining low basal levels of this reactive oxygen species-generating enzyme. Our model suggests that TGF-β1-induced Hic-5 functions as a negative feedback mechanism to limit myofibroblast differentiation and senescence by promoting the ubiquitin-proteasomal system-mediated degradation of Nox4. Together, these studies indicate that endogenous Hic-5 suppresses senescence and profibrotic activities of myofibroblasts by down-regulating Nox4 protein expression. Additionally, these are the first studies, to our knowledge, to demonstrate posttranslational regulation of Nox4.
From the Divisions of Pulmonary, Allergy, and Critical Care Medicine and.
Leena P
LP
Desai
From the Divisions of Pulmonary, Allergy, and Critical Care Medicine and.
Yong
Y
Zhou
From the Divisions of Pulmonary, Allergy, and Critical Care Medicine and.
Aida V
AV
Estrada
From the Divisions of Pulmonary, Allergy, and Critical Care Medicine and.
Qiang
Q
Ding
From the Divisions of Pulmonary, Allergy, and Critical Care Medicine and.
Guangjie
G
Cheng
Cell, Developmental and Integrative Biology, University of Alabama, Birmingham, Birmingham, Alabama 35294.
James F
JF
Collawn
From the Divisions of Pulmonary, Allergy, and Critical Care Medicine and vjthan@uab.edu.
Victor J
VJ
Thannickal
D002454:Cell Differentiation; D015536:Down-Regulation; D005347:Fibroblasts / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D055551:HSP27 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D060588:LIM Domain Proteins / Q000235:genetics / Q000378:metabolism*; D058628:Myofibroblasts / Q000166:cytology / Q000201:enzymology / Q000378:metabolism; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000235:genetics* / Q000378:metabolism; D059748:Proteolysis; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D054875:Ubiquitination
D055551:HSP27 Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D060588:LIM Domain Proteins; C490351:TGFB1I1 protein, human; D053773:Transforming Growth Factor beta1; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human
Adaptor Protein; Fibrosis; Hic-5, Cbl-c, HSP27, Nox4, p16, pRb, UPS; NADPH Oxidase; Senescence; Ubiquitination