title: Ezrin/Exocyst complex regulates mucin 5AC secretion induced by neutrophil elastase in human airway epithelial cells.
abstract: OBJECTIVE
  Increased mucin secretion is a characteristic feature of many chronic airway diseases, particularly during periods of exacerbation; however, the exact mechanism of mucin secretion remains unclear. Ezrin, which is a specific marker of apical membranes, is predominantly concentrated in exocyst-rich cell surface structures, crosslinking the actin cytoskeleton with the plasma membrane. In the present study, we examined whether Ezrin is involved in mucin 5AC (MUC5AC) secretion after neutrophil elastase (NE) attack, and we investigated the role of the exocyst complex docking protein Sec3 in this process.
  
  
  METHODS
  NE was used as a stimulator in a 16HBE14o- cell culture model. The expression and location of Ezrin and Sec3 were investigated, and the interaction between Ezrin and Sec3 in 16HBE14o-cells was assayed after treatment with NE, Ezrin siRNA, Sec3 siRNA, neomycin or PIP2-Ab.
  
  
  RESULTS
  We found that Ezrin was highly expressed in the bronchi of humans with chronic airway diseases. NE induced robust MUC5AC protein secretion. The Ezrin siRNA, Sec3 siRNA, and neomycin treatments led to impaired MUC5AC secretion in cells. Both Ezrin and Sec3 were recruited primarily to the cytoplasmic membrane after NE stimulation, and the neomycin and PIP2-Ab treatments abrogated this effect. Immunoprecipitation analysis revealed that Ezrin and Sec3 combined to form complexes; however, these complexes could not be detected in Ezrin∆1-333 mutant-transfected cells, even when PIP2 was added.
  
  
  CONCLUSIONS
  These results demonstrate that Ezrin/Sec3 complexes are essential for MUC5AC secretion in NE-stimulated airway epithelial cells and that PIP2 is of critical importance in the formation of these complexes.
authors.affiliation: Department of Respiratory Medicine, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Li
authors.forename: Na
authors.initials: N
authors.lastname: Li
authors.forename: Chun-Yi
authors.initials: CY
authors.lastname: Liu
authors.forename: Rui
authors.initials: R
authors.lastname: Xu
authors.forename: Victor P
authors.initials: VP
authors.lastname: Kolosov
authors.forename: Juliy M
authors.initials: JM
authors.lastname: Perelman
authors.forename: Xiang-Dong
authors.initials: XD
authors.lastname: Zhou
mesh_terms: D000368:Aged; D000906:Antibodies / Q000276:immunology; D001980:Bronchi / Q000166:cytology; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D004847:Epithelial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D019272:Leukocyte Elastase / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D055271:Mucin 5AC / Q000378:metabolism*; D009355:Neomycin / Q000494:pharmacology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000276:immunology; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism / Q000473:pathology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000099149:Ezrin
chemical_list: D000906:Antibodies; D003598:Cytoskeletal Proteins; D019272:Leukocyte Elastase; D055271:Mucin 5AC; D009355:Neomycin; D019269:Phosphatidylinositol 4,5-Diphosphate; D034741:RNA, Small Interfering; D033921:Vesicular Transport Proteins; D000099149:Ezrin; C529992:EXOC1 protein, human