title: 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.
  
  
  METHODS
  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 μM) and thapsigargin (TG, 0.2 μM) 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.
  
  
  CONCLUSIONS
  ER stress by TM or TG induced EMT through autophagy via activation of c-Src kinase in tubular epithelial cells.
authors.affiliation: Department of Internal Medicine, Asan Medical Center, University of Ulsan, Seoul, Korea.
authors.forename: Soo Young
authors.initials: SY
authors.lastname: Moon
authors.forename: Hyo Sang
authors.initials: HS
authors.lastname: Kim
authors.forename: Kyeong Woo
authors.initials: KW
authors.lastname: Nho
authors.forename: Young Joo
authors.initials: YJ
authors.lastname: Jang
authors.forename: Sang Koo
authors.initials: SK
authors.lastname: Lee
mesh_terms: D001343:Autophagy / Q000187:drug effects / Q000502:physiology*; D000081247:CSK Tyrosine-Protein Kinase; D002460:Cell Line; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects / Q000502:physiology*; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D058750:Epithelial-Mesenchymal Transition / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000201:enzymology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D047428:Protein Kinase Inhibitors; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human