Sumoylation enhances the activity of the TGF-β/SMAD and HIF-1 signaling pathways in keloids

Excessive fibrosis and extracellular matrix deposition resulting from upregulation of target genes expression mediated by transforming growth factor-beta (TGF-β)/SMAD and hypoxia inducible factor-1 (HIF-1) signaling pathways are the main mechanisms that drive keloid formation. Sumoylation is a protein posttranslational modification that regulates the function of proteins in many biological processes. In the present study, we aimed to investigate the mechanism underlying the effects of sumoylation on the TGF-β/SMAD and HIF-1 signaling pathways in keloids. We used 2-D08 to block sumoylation and silenced the expression of sentrin sumo-specific protease 1 (SENP1) to enhance sumoylation in human foreskin fibroblasts (HFFs) and human keloid fibroblasts (HKFs). We also reduced and increased intracellular SUMO1 levels by silencing SUMO1 and transfecting cells with a SUMO1 overexpression lentivirus, respectively. Sumoylation has the ability to amplify TGF-β/SMAD and HIF-1 signals in keloids, while SUMO1, especially the SUMO1-RanGAP1 complex, is the key molecule affecting the TGF-β/SMAD and HIF-1 signaling pathways. In addition, we also found that hypoxia promotes sumoylation in keloids and that HIF-1α is covalently modified by SUMO1 at Lys 391 and Lys 477 in HKFs. In summary, we elucidated the role and molecular mechanism of sumoylation in the formation of keloids, providing a new perspective for a potential therapeutic target of keloids.

Keywords: HIF-1α; Hypoxia; Keloid; SUMO1; SUMO1-RanGAP1 complex; Sumoylation; TGF-β/SMAD signaling pathway.