Journal of the renin-angiotensin-aldosterone system : JRAAS 2014 Feb 14. [Epub ahead of print]
Nikolaou, A; Stijlemans, B; Laoui, D; Schouppe, E; Tran, HT; Tourwé, D; Chai, SY; Vanderheyden, PM; Ginderachter, JA Van
Molecular and Biochemical Pharmacology, Vrije Universiteit Brussel, Belgium
The insulin-regulated aminopeptidase (IRAP) is expressed in several cell types, where it is mainly located in specialized secretory endosomes that are quickly recruited to the cell surface upon cell type-specific activation. Here we describe for the first time the expression and subcellular distribution of IRAP in macrophages. METHODS: IRAP mRNA expression, protein expression and presence at the cell surface was investigated by real-time polymerase chain reaction (PCR), Western blot and [3H]IVDE77 binding, respectively. RESULTS: IRAP mRNA expression was increased by interferon-γ (IFN-γ) and lipopolysaccharide (LPS), but not by anti-inflammatory cytokines (interleukin (IL)-4, IL-10, transforming growth factor β (TGF-β)). IFN-γ increased [3H]IVDE77 binding steadily over time, while LPS quickly and transiently recruited IRAP to the cell surface. Combined stimulations with IFN-γ and LPS showed the same pattern as LPS alone. Latex particles also induced a transient recruitment of IRAP to the cell surface, but no difference was observed in phagocytic uptake between wild-type and IRAP-/- macrophages, suggesting that the enzymatic activity of IRAP is not required for the ingestion of particles. CONCLUSION: IRAP is more highly expressed in pro-inflammatory M1-activated macrophages and its presence at the cell surface is modulated upon exposure to IFN-γ, LPS or exogenous particles.