title: Recruitment of α7 nicotinic acetylcholine receptor to caveolin-1-enriched lipid rafts is required for nicotine-enhanced Escherichia coli K1 entry into brain endothelial cells.
abstract: OBJECTIVE
  We investigate how the α7 nicotinic acetylcholine receptor (α7 nAChR), an essential regulator of inflammation, contributes to the α7 agonist nicotine-enhanced Escherichia coli K1 invasion of human brain microvascular endothelial cells (HBMECs) through lipid rafts/caveolae-mediated signaling.
  
  
  METHODS
  α7 nAChR-mediated signaling and bacterial invasion were defined by lipid raft fractionation, immunofluorescence microscopy and siRNA knockdown.
  
  
  RESULTS
  Nicotine-enhanced bacterial invasion was dose-dependently inhibited by two raft-disrupting agents, nystatin and filipin. Significant accumulation of the lipid raft marker GM3 was observed in HBMEC induced by E. coli K1 and nicotine. The recruitment of α7 nAChR and related signaling molecules, including vimentin, and Erk1/2, to caveolin-1 enriched lipid rafts was increased upon treatment with E44 or E44 plus nicotine. Erk1/2 activation (phosphorylation), which is required for α7 nAChR-mediated signaling and E44 invasion, was associated with lipid rafts and nicotine-enhanced bacterial infection. Furthermore, E44 invasion, E44/nicotine-induced activation of Erk1/2 and clustering of α7 nAChR and caveolin-1 was specifically blocked by both siRNAs.
  
  
  CONCLUSIONS
  α7 nAChR-mediated signaling through lipid rafts/caveolae is required for nicotine-enhanced E. coli K1 invasion of HBMEC.
authors.affiliation: Saban Research Institute of Childrens Hospital Los Angeles, Department of Pediatrics, University of Southern California, USA.
authors.forename: Feng
authors.initials: F
authors.lastname: Chi
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.forename: Xueye
authors.initials: X
authors.lastname: Zheng
authors.forename: Ambrose
authors.initials: A
authors.lastname: Jong
authors.forename: Sheng-He
authors.initials: SH
authors.lastname: Huang
mesh_terms: D000818:Animals; D000942:Antigens, Bacterial; D016667:Bacterial Capsules / Q000378:metabolism; D001921:Brain / Q000166:cytology / Q000382:microbiology*; D051242:Caveolin 1 / Q000378:metabolism*; D002478:Cells, Cultured; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000378:metabolism / Q000382:microbiology*; D004926:Escherichia coli / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology / Q000473:pathology; D006801:Humans; D021962:Membrane Microdomains / Q000737:chemistry / Q000378:metabolism*; D016920:Meningitis, Bacterial / Q000382:microbiology / Q000473:pathology; D051379:Mice; D009538:Nicotine / Q000378:metabolism*; D011135:Polysaccharides, Bacterial; D011978:Receptors, Nicotinic / Q000378:metabolism*; D012376:Rodent Diseases / Q000382:microbiology / Q000473:pathology; D015398:Signal Transduction
chemical_list: D000942:Antigens, Bacterial; C495540:CAV1 protein, human; D051242:Caveolin 1; D011135:Polysaccharides, Bacterial; D011978:Receptors, Nicotinic; C036962:capsular polysaccharide K1; D009538:Nicotine