title: Leucine-2-alanine enkephalin induced delta opioid receptors internalization expressed stably in CHO cells.
abstract: OBJECTIVE
  To characterize the internalization of delta opioid receptors (DOR) stably expressed in Chinese hamster ovary (CHO) cells and the role of the C-terminal in this process.
  
  
  METHODS
  Receptor membrane anchoring was shown by immunofluorescence microscopy. Receptor internalization was assessed by measuring the radioligand binding resistant to the acid-buffer wash.
  
  
  RESULTS
  Originally, all the wild-type (CHO-W) and C-truncated (CHO-T) DOR expressed were localized to the membrane. Agonist [3H] leucine-2-alanine enkephalin (LAE) but not the antagonist [3H]diprenorphine (Dip) induced rapid receptor internalization. The internalization of C-truncated DOR in CHO-T was similar to that of the wild-type in maximal level, but climbed up more slowly. DOR internalization was extracellular osmolarity- and temperature-sensitive. Pertussis toxin and universal protein kinase inhibitor staurosporine had no effect on it.
  
  
  CONCLUSIONS
  DOR internalization is an agonist and clathrin-coated pits dependent, but post-receptor cellular signal transduction independent process; moreover, the C-terminal of DOR, not engaged in membrane anchoring, affects the initialization of DOR internalization.
authors.affiliation: Shanghai Institute of Materia Medica, Chinese Academy of Sciences, China.
authors.forename: C H
authors.initials: CH
authors.lastname: Wang
authors.forename: D H
authors.initials: DH
authors.lastname: Zhou
authors.forename: J
authors.initials: J
authors.lastname: Chen
authors.forename: Z Q
authors.initials: ZQ
authors.lastname: Chi
mesh_terms: D000818:Animals; D016466:CHO Cells / Q000378:metabolism; D006224:Cricetinae; D004174:Diprenorphine / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology*; D010957:Plasmids; D017465:Receptors, Opioid, delta / Q000235:genetics / Q000378:metabolism*; D014162:Transfection
chemical_list: D017465:Receptors, Opioid, delta; D004174:Diprenorphine; D016308:Enkephalin, Leucine-2-Alanine