Smurf1 regulates ameloblast polarization by ubiquitination‐mediated degradation of RhoA

Abstract

Cell polarity is essential for ameloblast differentiation and enamel formation. Smurf1 can mediate cell polarization through ubiquitination degradation of specific substrates. But it remains unclear whether Smurf1 could regulate ameloblast polarity and the underlying mechanism. Here, immuno-fluorescence staining and RT-qPCR were applied to detect the expression of Smurf1 and F-actin. A mouse lower incisor defect model was constructed. Scanning electron microscope, rat lower incisor culture, western blot, wound healing assay and trans-well migration assay were performed to detect the influence of Smurf1 knockdown on ameloblast. IF double staining, western blot and co-immunoprecipitation were conducted to detect the interaction between Smurf1 and RhoA. The in vivo experiment was also performed.We found that Smurf1 was mainly expressed in the membrane and cell cortex of ameloblast, similar to F-actin. Smurf1 expression increased along ameloblast polarization and differentiation. After knocking down Smurf1, the cytoskeleton and cell morphology changed and the cell polarity was damaged. Smurf1 regulated ameloblast polarity through ubiquitination degradation of activated RhoA in vitro. Local knockdown of Smurf1 in rat lower incisor ameloblast resulted in ameloblast polarity loss, enamel matrix secretion disorder and chalky enamel, but RhoA inhibitor Y-27632 could reverse this effect. Collectively, Smurf1 could regulate the polarization of ameloblast through ubiquitination degradation of activated RhoA, which contributed to the knowledge of tooth development and provided new research ideas for cell polarity.

The role ofSMURFsin non‐cancerous diseases

“…66 SMURF1 is a significant regulator of RhoA degradation. 67 Rajagopalan et al have reported that enhancing proteasomal function, such as promoting SMURF1-mediated ubiquitination of RhoA, has a partially protective effect on right ventricular hypertrophy and failure. 68 Meanwhile, the hearts of mice with cardiomyocyte-specific RhoA deficiency exhibited a reduced degree of fibrosis in reaction to aortic pressure overload, 69 thereby offering novel perspectives on the treatment of hypertension and cardiac hypertrophy.…”

“…Treatment with RhoA inhibitors has been shown to have positive effects on blood pressure reduction and cardiac hypertrophy recovery 66 . SMURF1 is a significant regulator of RhoA degradation 67 . Rajagopalan et al have reported that enhancing proteasomal function, such as promoting SMURF1‐mediated ubiquitination of RhoA, has a partially protective effect on right ventricular hypertrophy and failure 68 .…”