Identification of Drosophila Yin and PEPT2 as evolutionarily conserved phagosome-associated muramyl dipeptide transporters
Department of Medicine, Division of Infectious Diseases and Immunology
Acetylmuramyl-Alanyl-Isoglutamine; Animals; Cell Line; Drosophila Proteins; Evolution, Molecular; Green Fluorescent Proteins; Host-Pathogen Interactions; Humans; Interleukin-6; Macrophages; Membrane Transport Proteins; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy, Confocal; NF-kappa B; Nod2 Signaling Adaptor Protein; Phagosomes; Reverse Transcriptase Polymerase Chain Reaction; Staphylococcus aureus; Symporters; Toll-Like Receptor 2; Toll-Like Receptor 6; Transfection; Tumor Necrosis Factor-alpha
NOD2 (nucleotide-binding oligomerization domain containing 2) is an important cytosolic pattern recognition receptor that activates NF-kappaB and other immune effector pathways such as autophagy and antigen presentation. Despite its intracellular localization, NOD2 participates in sensing of extracellular microbes such as Staphylococcus aureus. NOD2 ligands similar to the minimal synthetic ligand muramyl dipeptide (MDP) are generated by internalization and processing of bacteria in hydrolytic phagolysosomes. However, how these derived ligands exit this organelle and access the cytosol to activate NOD2 is poorly understood. Here, we address how phagosome-derived NOD2 ligands access the cytosol in human phagocytes. Drawing on data from Drosophila phagosomes, we identify an evolutionarily conserved role of SLC15A transporters, Drosophila Yin and PEPT2, as MDP transporters in fly and human phagocytes, respectively. We show that PEPT2 is highly expressed by human myeloid cells. Ectopic expression of both Yin and PEPT2 increases the sensitivity of NOD2-dependent NF-kappaB activation. Additionally, we show that PEPT2 associates with phagosome membranes. Together, these data identify Drosophila Yin and PEPT2 as evolutionarily conserved phagosome-associated transporters that are likely to be of particular importance in delivery of bacteria-derived ligands generated in phagosomes to cytosolic sensors recruited to the vicinity of these organelles.
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Citation: J Biol Chem. 2010 Jun 25;285(26):20147-54. Epub 2010 Apr 20. Link to article on publisher's site