title: Ligand-induced tyrosine phosphorylation of cysteinyl leukotriene receptor 1 triggers internalization and signaling in intestinal epithelial cells.
abstract: BACKGROUND
  Leukotriene D(4) (LTD(4)) belongs to the bioactive lipid group known as eicosanoids and has implications in pathological processes such as inflammation and cancer. Leukotriene D(4) exerts its effects mainly through two different G-protein-coupled receptors, CysLT(1) and CysLT(2). The high affinity LTD(4) receptor CysLT(1)R exhibits tumor-promoting properties by triggering cell proliferation, survival, and migration in intestinal epithelial cells. In addition, increased expression and nuclear localization of CysLT(1)R correlates with a poorer prognosis for patients with colon cancer.
  
  
  RESULTS
  Using a proximity ligation assay and immunoprecipitation, this study showed that endogenous CysLT(1)R formed heterodimers with its counter-receptor CysLT(2)R under basal conditions and that LTD(4) triggers reduced dimerization of CysLTRs in intestinal epithelial cells. This effect was dependent upon a parallel LTD(4)-induced increase in CysLT(1)R tyrosine phosphorylation. Leukotriene D(4) also led to elevated internalization of CysLT(1)Rs from the plasma membrane and a simultaneous increase at the nucleus. Using sucrose, a clathrin endocytic inhibitor, dominant-negative constructs, and siRNA against arrestin-3, we suggest that a clathrin-, arrestin-3, and Rab-5-dependent process mediated the internalization of CysLT(1)R. Altering the CysLT(1)R internalization process at either the clathrin or the arrestin-3 stage led to disruption of LTD(4)-induced Erk1/2 activation and up-regulation of COX-2 mRNA levels.
  
  
  CONCLUSIONS
  Our data suggests that upon ligand activation, CysLT(1)R is tyrosine-phosphorylated and released from heterodimers with CysLT(2)R and, subsequently, internalizes from the plasma membrane to the nuclear membrane in a clathrin-, arrestin-3-, and Rab-5-dependent manner, thus, enabling Erk1/2 signaling and downstream transcription of the COX-2 gene.
authors.affiliation: Department of Laboratory Medicine, Clinical Research Center, Lund University, Skåne University Hospital, Malmö, Sweden.
authors.forename: Ladan
authors.initials: L
authors.lastname: Parhamifar
authors.forename: Wondossen
authors.initials: W
authors.lastname: Sime
authors.forename: Yuliana
authors.initials: Y
authors.lastname: Yudina
authors.forename: Frederik
authors.initials: F
authors.lastname: Vilhardt
authors.forename: Matthias
authors.initials: M
authors.lastname: Mörgelin
authors.forename: Anita
authors.initials: A
authors.lastname: Sjölander
mesh_terms: D019390:Arrestins / Q000737:chemistry; D018938:Caco-2 Cells; D002966:Clathrin / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry; D019281:Dimerization; D004847:Epithelial Cells / Q000166:cytology*; D006801:Humans; D007422:Intestines / Q000166:cytology*; D008024:Ligands; D010766:Phosphorylation; D034741:RNA, Small Interfering / Q000378:metabolism; D018077:Receptors, Leukotriene / Q000378:metabolism*; D014443:Tyrosine / Q000737:chemistry*; D020696:rab5 GTP-Binding Proteins / Q000737:chemistry
chemical_list: D019390:Arrestins; D002966:Clathrin; D008024:Ligands; D034741:RNA, Small Interfering; D018077:Receptors, Leukotriene; C082333:arrestin3; D014443:Tyrosine; C412375:cysteinyl leukotriene receptor 2; D020696:rab5 GTP-Binding Proteins; D003545:Cysteine; C083169:leukotriene D4 receptor