Autoinhibition of the HECT-type ubiquitin ligase Smurf2 through its C2 domain.
Ubiquitination of proteins is an abundant modification that controls numerous cellular processes. Many Ubiquitin (Ub) protein ligases (E3s) target both their substrates and themselves for degradation. However, the mechanisms regulating their catalytic activity are largely unknown. The C2-WW-HECT-domain E3 Smurf2 downregulates transforming growth factor-beta (TGF-beta) signaling by targeting itself, the adaptor protein Smad7, and TGF-beta receptor kinases for degradation. Here, we demonstrate that an intramolecular interaction between the C2 and HECT domains inhibits Smurf2 activity, stabilizes Smurf2 levels in cells, and similarly inhibits certain other C2-WW-HECT-domain E3s. Using NMR analysis the C2 domain was shown to bind in the vicinity of the catalytic cysteine, where it interferes with Ub thioester formation. The HECT-binding domain of Smad7, which activates Smurf2, antagonizes this inhibitory interaction. Thus, interactions between C2 and HECT domains autoinhibit a subset of HECT-type E3s to protect them and their substrates from futile degradation in cells.
Wiesner
Silke
S
Hospital for Sick Children, 555 University Avenue, Toronto, Ontario M5G 1X8, Canada. silke@pound.med.utoronto.ca
Ogunjimi
Abiodun A
AA
Wang
Hong-Rui
HR
Rotin
Daniela
D
Sicheri
Frank
F
Wrana
Jeffrey L
JL
Forman-Kay
Julie D
JD
D001665:Binding Sites; D020134:Catalytic Domain; D003545:Cysteine / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D008954:Models, Biological; D008956:Models, Chemical; D008958:Models, Molecular; D009154:Mutation; D019906:Nuclear Magnetic Resonance, Biomolecular; D010716:Phosphatidylinositols / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000378:metabolism; D051906:Smad7 Protein / Q000737:chemistry; D044767:Ubiquitin-Protein Ligases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D010716:Phosphatidylinositols; D011994:Recombinant Proteins; C497806:SMAD7 protein, human; D051906:Smad7 Protein; C471641:SMURF2 protein, human; D044767:Ubiquitin-Protein Ligases; D005982:Glutathione Transferase; D003545:Cysteine