Endoplasmic Reticulum Stress Induces Epithelial-Mesenchymal Transition through Autophagy via Activation of c-Src Kinase

Abstract

Background: Endoplasmic reticulum (ER) stress has been implicated in inducing epithelial-mesenchymal transition (EMT). ER stress is also known to induce autophagy. However, it is unclear whether ER stress-induced autophagy contributes to EMT. We hypothesized that ER stress might induce EMT through autophagy via activation of c-Src kinase in tubular epithelial cells. Method: All experiments were performed using HK-2 cells. Protein expression was measured by Western blot analysis. Immunofluorescence and small interfering RNA (siRNA) experiments were performed. Results: Chemical ER stress inducers such as tunicamycin (TM, 0.2 μ<smlcap>M</smlcap>) and thapsigargin (TG, 0.2 μ<smlcap>M</smlcap>) induced EMT, as shown by upregulation of α-smooth muscle actin and downregulation of E-cadherin. ER stress inhibitors such as 4-PBA and salubrinal suppressed both TM- and TG-induced EMT. TM and TG also induced autophagy, as evidenced by upregulation of LC3-II and beclin-1, which were abolished by pretreatment with ER stress inhibitors. Transfection with siRNA targeting ER stress protein (IRE-1) blocked the TM- or TG-induced EMT and autophagy. Autophagy inhibitors such as 3-methyladenine and bafilomycin inhibited the TM- or TG-induced EMT. Transfection with siRNA targeting autophagy protein (beclin-1) also blocked the TM- or TG-induced EMT. Both TM and TG induced activation of c-Src kinase. Inhibitor of c-Src kinase (PP2) suppressed the TM- or TG-induced autophagy and EMT. Conclusion: ER stress by TM or TG induced EMT through autophagyvia activation of c-Src kinase in tubular epithelial cells.

Anti-Fibrotic Effect of Losartan, an Angiotensin II Receptor Blocker, Is Mediated through Inhibition of ER Stress via Up-Regulation of SIRT1, Followed by Induction of HO-1 and Thioredoxin

“…ER stress is also a known cause of EMT and we previously reported that ER stress was able to induce EMT in renal tubular cells [34]. In this study, we found that losartan could suppress the tunicamycin-induced EMT as well.…”

Inositol-requiring protein 1 – X-box-binding protein 1 pathway promotes epithelial–mesenchymal transition via mediating snail expression in pulmonary fibrosis

“…EMT is a process that alveolar epithelial cells (AECs) are transformed into the phenotype of mesenchymal cells such as myofibroblasts. During EMT, AECs lose the specific epithelial markers, such as zonula occludens-1 (ZO-1), E-cadherin and cytokeratin, and gain mesenchymal markers, such as vimentin, ␣-smooth muscle actin (␣-SMA), and fibroblast specific protein 1 (FSP-1) (Moon et al, 2014). Previous researches suggest that endoplasmic reticulum (ER) stress plays an incredible role in EMT in the progression of lung fibrosis (Tanjore et al, 2015;Zhao et al, 2014b).…”

Germline compound heterozygous poly-glutamine deletion inUSF3may be involved in predisposition to heritable and sporadic epithelial thyroid carcinoma

“…The majority of previous studies focused on its reverse signalling, ie, that ER stress induces EMT and autophagy (33); in contrast, a recent report revealed that EMT can sensitize cells to ER stress by activating the PERK-elF2α axis of the UPR (12). In our present study, this sensitization seems to be due to the loss of the endogenous ER stress response/UPR signalling although it remains unclear how the loss of/altered USF3 could lead to the loss of ER stress response/UPR.…”