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

Abstract

<jats:p>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 <jats:italic>Caenorhabditis elegans</jats:italic> 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 <jats:italic>C. elegans</jats:italic> phenotype caused by defective DAF-7/TGF-β signaling was enhanced and suppressed, respectively, by <jats:italic>ubh-1</jats:italic> deletion and overexpression in the loss-of-function genetic backgrounds of <jats:italic>daf7</jats:italic>, <jats:italic>daf-1</jats:italic>/TGF-βRI, and <jats:italic>daf4</jats:italic>/R-SMAD, but not of <jats:italic>daf-8</jats:italic>/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, <jats:italic>i.e.</jats:italic> 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-L1<jats:sup>C90A</jats:sup>, 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.</jats:p>

Endothelial-specific depletion of TGF-β signaling affects lymphatic function

“…Male TβRII fl/fl and TβRII iΔLEC mice (7-12 weeks old) were subcutaneously implanted with LLCs (2.5 × 10 5 cells) in 100 μl of PBS. Tumor volumes (V) were calculated using the following formula: length × width × width × 0.5 [13]. The tumors were surgically removed and embedded into a frozen section compound (Leica).…”

Similar sequences but dissimilar biological functions of GDF11 and myostatin

“…Indeed, analysis of multiple invertebrate species revealed that they harbor a single homologous gene corresponding to GDF11 and MSTN 10 . For instance, in Caenorhabditis elegans, daf-7 was shown to encode a homolog of GDF11 and MSTN, while in fruit flies (Drosophila melanogaster), myoglianin (Myo) was found to exhibit the highest sequence homology to GDF11 and MSTN [10][11][12][13] . An important question that arose from these identifications was whether the divergence of GDF11 and MSTN occurred at the time of the emergence of vertebrates.…”

“…The reason for and functional significance of the divergence of the two mstn genes in fish remains to be clarified. Interestingly, many of the reported functions of the invertebrate MSTN/GDF11 protein are very different from the well-established suppressive role of vertebrate MSTN in the development of multiple tissues, and the broad expression pattern of the ancestral protein more closely resembles the expression pattern of vertebrate GDF11 11,13,[15][16][17][18][19] . These observations imply that MSTN most likely emerged from the ancestral gene to allow more specific control of skeletal muscle growth in vertebrates, although the relatively small amount of information available on the function of invertebrate MSTN/ GDF11 limits further interpretation.…”

“…Ancestral Mstn/Gdf11 was also shown to exhibit a broad expression pattern, which is similar to that of vertebrate GDF11 but different from the muscle-specific expression pattern of vertebrate MSTN . For instance, C. elegans daf-7 , a homolog of GDF11 and MSTN expressed in ASI neurons, has been shown to promote the reproductive growth and development of worms 11 , 19 , 36 . Accordingly, daf-7 -mutant worms exhibited a slower growth rate and increased dauer entry 11 .…”

“…For instance, C. elegans daf-7 , a homolog of GDF11 and MSTN expressed in ASI neurons, has been shown to promote the reproductive growth and development of worms 11 , 19 , 36 . Accordingly, daf-7 -mutant worms exhibited a slower growth rate and increased dauer entry 11 . Genetic mutations or RNAi-mediated knockdown of daf-7 also resulted in an increase in fat accumulation 18 , despite a reduction in the feeding rate, and declines in germ cell production and sperm motility 37 , 38 .…”