Selective labeling of IRAP by the tritiated AT4 receptor ligand [3H]Angiotensin IV and its stable analog [3H]AL-11

Heidi Demaegdt, Aneta Lukaszuk, E. De Buyser, Jean-Paul De Backer, E Szemenyei, Géza Tóth, S. Chakravarthy, M. Panicker, Yvette Michotte, Dirk Tourwe, Georges Vauquelin

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16 Citations (Scopus)


'AT4 receptors' through which Angiotensin IV (Ang IV) improves memory acquisition, were recently identified as insulin regulated aminopeptidase (IRAP). Radioligand binding studies have hitherto been performed with iodinated Ang IV in the presence of divalent cation chelators EDTA and 1,10-phenanthrolin. Hence, they referred to the apo-form of IRAP. Presently, binding of [3H]Ang IV and [3H]AL-11, a stable Ang IV analog, was compared on Chinese hamster ovary (CHO-K1) and mouse hippocampal (P40H1) cell membranes. With chelators, their high affinity sites showed the same pharmacological profile as for [125I]Ang IV binding. Without chelators, only high affinity binding was perceived for [3H]AL-11. The same pharmacological profile was recorded in both membrane preparations; it was different from the one in the presence of chelators and corresponded to catalytically active IRAP (despite the concurrent presence of aminopeptidase N (APN) in P40H1 cell membranes). This confirms that the active and apo-forms of IRAP have a distinct pharmacological profile.
Original languageEnglish
Pages (from-to)77-86
Number of pages10
JournalMolecular and Cellular Endocrinology
Issue number1-2
Publication statusPublished - Nov 2009


  • IRAP
  • Ang IV
  • AL-11


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