TY - JOUR T1 - LATE-BREAKING ABSTRACT: Inhibition of the ubiquitin-E3-ligase FBXW7 enhances steroid efficacy: New concept for treating steroid insensitivity JF - European Respiratory Journal JO - Eur Respir J DO - 10.1183/13993003.congress-2015.PA5081 VL - 46 IS - suppl 59 SP - PA5081 AU - Marc Kaestle AU - David Wyatt AU - Paul Nicklin Y1 - 2015/09/01 UR - http://erj.ersjournals.com/content/46/suppl_59/PA5081.abstract N2 - Background: Steroids are a mainstay of asthma therapy. Nevertheless, specific asthma sub-groups are poorly controlled by inhaled corticosteroids through mechanisms that remain undefined. FBXW7 is the functional component of the Skp-Cullin-F-box E3-ubiquitin-ligase, targeting substrates such as the Gluccocorticoid Receptor (GR) for proteasomal degradation. In addition, FBXW7 is associated with the degradation of several pro-apoptotic genes.Hypothesis: FBXW7 knockout/knock-down has the potential to enhance steroid efficacy.Material and Methods: Cellular assays were performed with HTC116-FBXW7-/- cells and the parental cell line. Additionally, A549 cells were transfected with FBXW7 siRNA using a standard Lipofectamine protocol. The effects of FBXW7 on inflammatory readouts from epithelial cells were also determined by IL-8 ELISA. FBXW7 and GR expression was assessed by Western Blots. The sensitivity of GR to activation by Dexamethasone was determined via qPCR of steroid-responsive genes.Results: FBXW7-/- caused a statistically significant doubling of GR protein level compared to the parental cell line. GR levels were also increased after FBXW7 siRNA k.d. Moreover, FBXW7 siRNA k.d. resulted in a significant enhancement of steroid responsive genes (e.g. Gilz, Fkbp51) and a 2-fold reduction of basal IL-8 secretion after steroid treatment compared to the controls. Importantly, apoptosis was less sensitive to siRNA-mediated FBXW7 k.d. than the enhancement of steroid sensitivity and inflammatory readouts in epithelial cells.Conclusion: Reduction of FBXW7 caused a significant augmentation of functional GR and may have the potential to improve the efficacy of steroids. ER -