title: NHE-1 relocation outside cholesterol-rich membrane microdomains is associated with its benzo[a]pyrene-related apoptotic function.
abstract: BACKGROUND
  Polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene (B[a]P), are ubiquitous toxic environmental pollutants capable of inducing cell death. Intracellular pH plays a key role in the regulation of cell survival and death. Our previous works have demonstrated that intracellular alkalinization mediated by Na(+)/H(+) exchanger 1 (NHE-1) is a critical event involved in B[a]P-induced apoptosis. The aim of this study was to further elucidate the mechanisms of NHE-1 activation upon B[a]P exposure.
  
  
  METHODS
  We tested the effects of plasma membrane cholesterol enrichment or depletion on B[a]P-induced NHE-1 activation related to apoptosis. We isolated cholesterol-rich plasma membrane microdomains to assess NHE-1 submembrane location and immunoprecipitated NHE-1 from the different sub-membrane fractions obtained to examine NHE-1 protein interactions during B[a]P-induced apoptosis.
  
  
  RESULTS
  We found that NHE-1 is preferentially located in cholesterol-rich microdomains and that B[a]P activates NHE-1 via its relocation and binding of calmodulin outside these specialized plasma membrane microstructures; these events are necessary for the execution of the apoptosis-related intracellular alkalinization.
  
  
  CONCLUSIONS
  Plasma membrane location of NHE-1 affects its protein interactions and apoptotic function.
authors.affiliation: EA 4427 SeRAIC / IRSET, Equipe labellisée Ligue contre le Cancer, Université de Rennes 1, Rennes, France.
authors.forename: Xavier
authors.initials: X
authors.lastname: Tekpli
authors.forename: Laurence
authors.initials: L
authors.lastname: Huc
authors.forename: Odile
authors.initials: O
authors.lastname: Sergent
authors.forename: Béatrice
authors.initials: B
authors.lastname: Dendelé
authors.forename: Marie-Thérèse
authors.initials: MT
authors.lastname: Dimanche-Boitrel
authors.forename: Jørn A
authors.initials: JA
authors.lastname: Holme
authors.forename: Dominique
authors.initials: D
authors.lastname: Lagadic-Gossmann
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001564:Benzo(a)pyrene / Q000494:pharmacology*; D015153:Blotting, Western; D002147:Calmodulin / Q000378:metabolism; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D002147:Calmodulin; D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D001564:Benzo(a)pyrene; D002784:Cholesterol