The evolutionarily conserved deubiquitinase UBH1/UCH-L1 augments DAF7/TGF-β signaling, inhibits dauer larva formation, and enhances lung tumorigenesis

• Published in: The Journal of biological chemistry 2020-07, Vol.295 (27), p.9105-9120
• Main Authors: Nagata, Asami, Itoh, Fumiko, Sasho, Ayaka, Sugita, Kaho, Suzuki, Riko, Hinata, Hiroki, Shimoda, Yuta, Suzuki, Eri, Maemoto, Yuki, Inagawa, Toshihiko, Fujikawa, Yuuta, Ikeda, Eri, Fujii, Chiaki, Inoue, Hideshi
• Format: Article
• Language: English
• Subjects: Animals; Caenorhabditis elegans; Caenorhabditis elegans Proteins - metabolism; Carcinogenesis - metabolism; cell signaling; Cell Transformation, Neoplastic; DAF-7; Deubiquitinating Enzymes; deubiquitylation (deubiquitination); hypoxia; Larva - metabolism; Lung - metabolism; lung cancer; lung carcinoma; post-translational modification (PTM); Signal Transduction; Signal Transduction - genetics; SMAD transcription factor; Smad2 Protein - metabolism; Smad3 Protein - metabolism; Transforming Growth Factor beta - metabolism; transforming growth factor β (TGF-β); ubh-1/UCH-L1; Ubh1; ubiquitin C-terminal hydrolase-L1 (UCH-L1); Ubiquitin Thiolesterase - metabolism; Ubiquitin Thiolesterase - physiology; Ubiquitination
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.RA119.011222

Modification of the transforming growth factor β (TGF-β) signaling components by (de)ubiquitination is emerging as a key regulatory mechanism that controls cell signaling responses in health and disease. Here, we show that the deubiquitinating enzyme UBH-1 in Caenorhabditis elegans and its human homolog, ubiquitin C-terminal hydrolase-L1 (UCH-L1), stimulate DAF-7/TGF-β signaling, suggesting that this mode of regulation of TGF-β signaling is conserved across animal species. The dauer larva–constitutive C. elegans phenotype caused by defective DAF-7/TGF-β signaling was enhanced and suppressed, respectively, by ubh-1 deletion and overexpression in the loss-of-function genetic backgrounds of daf7, daf-1/TGF-βRI, and daf4/R-SMAD, but not of daf-8/R-SMAD. This suggested that UBH-1 may stimulate DAF-7/TGF-β signaling via DAF-8/R-SMAD. Therefore, we investigated the effect of UCH-L1 on TGF-β signaling via its intracellular effectors, i.e. SMAD2 and SMAD3, in mammalian cells. Overexpression of UCH-L1, but not of UCH-L3 (the other human homolog of UBH1) or of the catalytic mutant UCH-L1C90A, enhanced TGF-β/SMAD-induced transcriptional activity, indicating that the deubiquitination activity of UCH-L1 is indispensable for enhancing TGF-β/SMAD signaling. We also found that UCH-L1 interacts, deubiquitinates, and stabilizes SMAD2 and SMAD3. Under hypoxia, UCH-L1 expression increased and TGF-β/SMAD signaling was potentiated in the A549 human lung adenocarcinoma cell line. Notably, UCH-L1–deficient A549 cells were impaired in tumorigenesis, and, unlike WT UCH-L1, a UCH-L1 variant lacking deubiquitinating activity was unable to restore tumorigenesis in these cells. These results indicate that UCH-L1 activity supports DAF-7/TGF-β signaling and suggest that UCH-L1's deubiquitination activity is a potential therapeutic target for managing lung cancer.