title: Enteroaggregative Escherichia coli induced increase in intracellular calcium concentration modulates cytoskeletal F-actin rearrangement and bacterial entry in INT-407 cells.
abstract: BACKGROUND
  Enteroaggregative Escherichia coli (EAEC) is an emerging enteric pathogen, associated with cases of acute and persistent diarrhoea worldwide. The pathogenesis of EAEC is yet to be understood. In intestinal epithelium, an increase in [Ca²⁺](i) has been attributed due to the action of different enteric pathogens. EAEC was shown to increase [Ca²⁺](i) in HEp-2 cells.The present study was undertaken to investigate the effect of EAEC induced increase in [Ca²⁺](i) oncultured human intestinal epithelial cells.
  
  
  METHODS
  INT-407 cells were infected with EAEC (T8 strain) in the absence and presence of dantrolene (inhibitor of release of Ca²⁺ from intracellular stores)/verapamil (L-type Ca²⁺ channel blocker)/BAPTAAM (Ca²⁺ chelator)/U73122 (PLC inhibitor)/Cytochalasin-D (inhibitor of actin polymerization). [Ca²⁺](i) was estimated using Fura-2/AM. Cytoskeletal rearrangement was assessed by F-actin staining using TRITC-phalloidin. The invasiveness of EAEC-T8 to INT-407 cells was checked by electron microscopy and invasion assay.
  
  
  RESULTS
  A significant increase in [Ca²⁺](i) was observed in EAEC-T8 infected INT-407 cells, which was reduced in presence of dantrolene/verapamil/U73122. EAEC-T8 could induce cytoskeletal F-actin polymerization in INT-407 cells and was found to be invasive in nature. The cytoskeletal rearrangement as well as invasion of EAEC-T8 was attenuated in presence of U73122/dantrolene/BAPTA-AM/verapamil/cytochalasin D.
  
  
  CONCLUSIONS
  EAEC induced increase in [Ca²⁺](i) seems to play a major role in host cytoskeletal F-actin rearrangements leading to invasion of the organism.
  
  
  CONCLUSIONS
  Our study undoubtedly will lead to an improved understanding of EAEC-pathogenesis.
authors.affiliation: Department of Experimental Medicine & Biotechnology, Post Graduate Institute of Medical Education & Research, Chandigarh 160012, India.
authors.forename: Monica
authors.initials: M
authors.lastname: Konar
authors.forename: Sujata
authors.initials: S
authors.lastname: Ghosh
mesh_terms: D000199:Actins / Q000378:metabolism*; D001422:Bacterial Adhesion; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D003599:Cytoskeleton / Q000378:metabolism*; D004926:Escherichia coli / Q000502:physiology*; D004927:Escherichia coli Infections / Q000378:metabolism* / Q000382:microbiology; D006801:Humans; D015854:Up-Regulation
chemical_list: D000199:Actins; D002118:Calcium