Binding of "AT4 receptor" ligands to insulin regulated aminopeptidase (IRAP) in intact Chinese hamster ovary cells

Heidi Demaegdt, Paul Gard, Jean-Paul De Backer, Aneta Lukaszuk, E Szemenyei, Géza Tóth, Dirk Tourwe, Georges Vauquelin

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Insulin regulated aminopeptidase (IRAP) recognises "AT4-receptor" ligands like angiotensin IV (Ang IV) and peptidomimetics like AL-11. The metabolic stability and high affinity of [3H]AL-11 for catalytically active IRAP allowed its detection in Chinese hamster ovary (CHO-K1) cell membranes in the absence of chelators (Demaegdt et al., 2009). Here, we show that, contrary to [3H]Ang IV, [3H]AL-11 displays high affinity and specificity for IRAP in intact CHO-K1 cells as well. After binding to IRAP at the surface, [3H]AL-11 is effectively internalized by an endocytotic process. Unexpectedly, surface binding and internalization of [3H]AL-11 was not affected by pretreating the cells with Ang IV but declined with AL-11. In the latter case surface expression of IRAP even increased. After elimination of simpler explanations, it is proposed that metabolically stable "AT4-receptor" ligands undergo semi-continuous cycling between the cell surface and endosomal compartments. The in vivo efficacy of stable and unstable "AT4-receptor" ligands could therefore differ.
Original languageEnglish
Pages (from-to)34-44
Number of pages11
JournalMolecular and Cellular Endocrinology
Volume339
Issue number1-2
Publication statusPublished - 2011

Keywords

  • IRAP
  • CHO cells
  • internalization
  • radioligand binding
  • Ang IV
  • AL-11

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