Ubiquitin carboxyl-terminal hydrolase-L5 promotes TGFβ-1 signaling by de-ubiquitinating and stabilizing Smad2/Smad3 in pulmonary fibrosis.
Transforming growth factor β-1 (TGFβ-1)-induced phosphorylation of transcription factors Smad2 and Smad3 plays a crucial role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, the molecular regulation of Smad2/Smad3 proteins stability remains a mystery. Here, we show that ubiquitin carboxyl-terminal hydrolase-L5 (UCHL5 or UCH37) de-ubiquitinates both Smad2 and Smad3, up-regulates their stability, and promotes TGFβ-1-induced expression of profibrotic proteins, such as fibronectin (FN) and α-smooth muscle actin (α-SMA). Inhibition or down-regulation of UCHL5 reduced Smad2/Smad3 levels and TGFβ-1-induced the expression of FN and α-SMA in human lung fibroblast. We demonstrate that Smad2 and Smad3 ubiquitination was diminished by over-expression of UCHL5, while it was enhanced by inhibition or down-regulation of UCHL5. UCHL5 is highly expressed in IPF lungs. UCHL5, Smad2, and Smad3 levels were increased in bleomycin-injured lungs. Administration of UCHL5 inhibitor, b-AP15, reduced the expression of FN, type I collagen, Smad2/Smad3, and the deposition of collagen in lung tissues in a bleomycin-induced model of pulmonary fibrosis. Our studies provide a molecular mechanism by which UCHL5 mitigates TGFβ-1 signaling by stabilizing Smad2/Smad3. These data indicate that UCHL5 may contribute to the pathogenesis of IPF and may be a potential therapeutic target.
Department of Anesthesia, First Hospital of Jilin University, Changchun, China.
Ling
L
Nan
Department of Medicine, Acute Lung Injury Center of Excellence, Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, United States.
Anastasia M
AM
Jacko
Department of Medicine, Acute Lung Injury Center of Excellence, Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, United States.
Jiangning
J
Tan
Department of Anesthesia, First Hospital of Jilin University, Changchun, China.
Dan
D
Wang
Department of Medicine, Acute Lung Injury Center of Excellence, Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, United States.
Jing
J
Zhao
Department of Medicine, Acute Lung Injury Center of Excellence, Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, United States.
Daniel J
DJ
Kass
Department of Anesthesia, First Hospital of Jilin University, Changchun, China.
Haichun
H
Ma
Department of Medicine, Acute Lung Injury Center of Excellence, Department of Cell Biology, University of Pittsburgh, Pittsburgh, PA, United States.
Yutong
Y
Zhao
D000818:Animals; D001761:Bleomycin / Q000633:toxicity; D002460:Cell Line; D002478:Cells, Cultured; D004195:Disease Models, Animal; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000209:etiology / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D010881:Piperidones / Q000494:pharmacology; D055550:Protein Stability / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D051899:Smad2 Protein / Q000737:chemistry / Q000378:metabolism*; D051900:Smad3 Protein / Q000737:chemistry / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000378:metabolism*; D043222:Ubiquitin Thiolesterase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D054875:Ubiquitination / Q000187:drug effects
C569633:3,5-bis((4-nitrophenyl)methylidene)-1-prop-2-enoylpiperidin-4-one; D010881:Piperidones; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D053773:Transforming Growth Factor beta1; D001761:Bleomycin; C421245:UCHL5 protein, human; D043222:Ubiquitin Thiolesterase; C581032:Uchl5 protein, mouse