Thus, neurotrophin-stimulated phosphorylation of Smad ubiquitylation regulator factor 1 (Smurf1), a key component of TGF-β/BMP pathway, reduces degradation of polarity protein Par6 and enhances proteolysis of growth-inhibiting RhoA factor, eventually leading to axon outgrowth (Cheng et al., 2011).Similarly, in cisplatin-treated cancer cells, PKA phosphorylation of Smurf1 prevents degradation of the pro-apoptotic protein Nur77, triggering the mitochondrial apoptotic machinery (Lin et al., 2014). Here, SMURF1 is linked to cancer.