Reactive oxygen species/neddylation is a novel pathway of transforming growth factor‐β‐induced smooth muscle cell differentiation (952.2)

Abstract

Smooth muscle cell (SMC) differentiation is an essential process in cardiovascular development. SMCs can be differentiated from pluripotent mesenchymal progenitors by transforming Growth Factor‐β (TGF‐β) while ubiquitin‐mediated protein degradation blocks SMC differentiation. Neural precursor cell‐Expressed Developmentally Down‐regulated 8 (NEDD8), a member in ubiquitin family, promotes protein stability and prevents protein degradation by conjugating to target proteins. We found that NEDD8/neddylation is essential for TGF‐β‐induced SMC differentiation. NEDD8 protein is increased during TGF‐β‐induced SMC differentiation and conjugates to smooth muscle α‐actin (α‐SMA). Blockade of neddylation by neddylation inhibitor (MLN‐4924) or NEDD8 short hairpin interfering RNA significantly inhibited the expression of α‐SMA and calponin (CNN) in TGF‐β‐treated cells. We found that reactive oxygen species (ROS) attenuation by SOD2 overexpression blocked TGF‐β‐induced NEDD8 conjugation to α‐SMA. SOD2 appeared to block neddylation through inhibiting expression of Casitas B‐lineage lymphoma (c‐Cbl), suggesting that ROS/c‐Cbl mediates TGF‐β‐mediated neddylation of α‐SMA and CNN. NEDD8/neddylation appears to enhance α‐SMA and CNN stability and prevent proteasome‐mediated degradation because administration of proteasome inhibitor (MG‐132) significantly inhibited α‐SMA and CNN protein degradation in neddylation‐depleted cells. Taken together, our study demonstrates that NEDD8‐mediated neddylation through ROS/c‐Cbl is a novel molecular event critical for TGF‐β‐induced SMC differentiation.Grant Funding Source: NIH‐R01