Generation And Phenotype Analysis Of The Smurf1 C426A Knock In Mouse

Ubiquitin is involved mainly in the regulation of cellular homeostasisby its roles playing in the ubiquitin–proteasome system in eukaryote. Conjugation of ubiquitin to the targets requires three enzymes, the E1, E2, and E3. Ubiquitin E3 ligasesare pivotal effectors of the ubiquitin-proteasome system, they interacts with both substrates and E2, determining the substrate specificity. According to the structure, the E3 ubiquitin ligases are classified as two types: RING(Really Interesting New Gene)-type ligases and HECT(Homologous to E6-AP C Terminus)-type ligases. Ligases with a structure of C2-WW-HECT-domain including Smurfs(Smad ubiquitylation regulatory factors) belong to the Nedd4 family of HECT-type ligases.Smurf1(Smad ubiquitylation regulatory factor 1)is essential in regulation of TGF-βsignaling. Smurf1 downregulates bone morphogenetic protein(BMP) signaling by interacting and degradates Smad1, Smad5 and BMP receptor kinases for degradation.Smurf1 also plays critical roles in the regulation of the Wnt and Rho A pathways.Genomic ablation of Smurf1 results in an age-dependent increase of bone mass in mice.It has been demonstrated previously that HECT-type E3 Smurf1 covalently modified by ubiquitin-like protein Nedd8. Here, we show thatatransgenic mice Smurf1 C426 A in which the mutant Smurf1 loses Neddylation E3 activity, shows the similarphenotype with Smurf1-deficient mice.Our current findings provide new clues of Smurf1 activation regulation.