The deubiquitinating enzyme UCH37 interacts with Smads and regulates TGF-beta signalling.
Disruption of components in the transforming growth factor-beta (TGF-beta) signalling cascade is a common occurrence in human cancers. TGF-beta pathway activation is accomplished via serine/threonine kinase receptors and intracellular Smad transcription factors. A key regulatory step involves specific ubiquitination by Smurfs that mediate the proteasomal degradation of Smads and/or receptors. Here, we report a novel interaction between Smads and ubiquitin C-terminal hydrolase UCH37, a deubiquitinating enzyme that could potentially reverse Smurf-mediated ubiquitination. In GST pull down experiments, UCH37 bound weakly to Smad2 and Smad3, and bound very strongly to Smad7 in a region that is distinct from the -PY- motif in Smad7 that interacts with Smurf ubiquitin ligases. Endogenous Smad7 and UCH37 formed a stable complex in U4A/JAK1 cells, and FLAG-Smad7 co-immunoprecipitated with HA-UCH37 in transfected HEK-293 cells. In addition, we show that UCH37 can deubiquitinate and stabilize the type I TGF-beta receptor. Furthermore, overexpression of UCH37 upregulates TGF-beta-dependent transcription, and this effect is reversed in cells subject to RNAi-mediated knockdown of endogenous UCH37. These findings support a new role for deubiquitinating enzymes in the control of the TGF-beta signalling pathway, and provide a novel molecular target for the design of inhibitors with therapeutic potential in cancer.
Wicks
Stephen J
SJ
School of Biological Sciences, University of East Anglia, Earlham Road, Norwich Norfolk NR4 7TJ, UK.
Haros
Katherine
K
Maillard
Marjorie
M
Song
Ling
L
Cohen
Robert E
RE
Dijke
Peter Ten
PT
Chantry
Andrew
A
D030201:Activin Receptors, Type I / Q000378:metabolism; D002268:Carboxypeptidases; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D005786:Gene Expression Regulation; D006801:Humans; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases; D034622:RNA Interference; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D015398:Signal Transduction; D051901:Smad4 Protein / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism; D043222:Ubiquitin Thiolesterase
D002352:Carrier Proteins; D018125:Receptors, Transforming Growth Factor beta; C497796:SMAD4 protein, human; D051901:Smad4 Protein; D016212:Transforming Growth Factor beta; D025801:Ubiquitin; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D002268:Carboxypeptidases; C421245:UCHL5 protein, human; D043222:Ubiquitin Thiolesterase