The movement of key transition metal ions is recognized to be of critical importance in the interaction between macrophages and intracellular pathogens. The present study investigated the role of copper in mouse macrophage responses to Salmonella enterica sv. Typhimurium. The copper chelator BCS (bathocuproinedisulfonic acid, disodium salt) increased intracellular survival of S. Typhimurium within primary mouse BMM (bone-marrow-derived macrophages) at 24 h post-infection, implying that copper contributed to effective host defence against this pathogen. Infection of BMM with S. Typhimurium or treatment with the TLR (Toll-like receptor) 4 ligand LPS (lipopolysaccharide) induced the expression of several genes encoding proteins involved in copper transport [Ctr (copper transporter) 1, Ctr2 and Atp7a (copper-transporting ATPase 1)], as well as the multi-copper oxidase Cp (caeruloplasmin). Both LPS and infection with S. Typhimurium triggered copper accumulation within punctate intracellular vesicles (copper ‘hot spots’) in BMM as indicated by the fluorescent reporter CS1 (copper sensor 1). These copper hot spots peaked in their accumulation at approximately 18 h post-stimulation and were dependent on copper uptake into cells. Localization studies indicated that the copper hot spots were in discrete vesicles distinct from Salmonella containing vacuoles and lysosomes. We propose that copper hot spot formation contributes to antimicrobial responses against professional intracellular bacterial pathogens.
- copper redistribution
- copper sensor 1 (CS1)
- innate immunity
Abbreviations: ATP7A/Atp7a, copper-transporting ATPase 1; Atp7b, copper-transporting ATPase 2; BCS, bathocuproinedisulfonic acid, disodium salt; BMM, bone-marrow-derived macrophages; copA, copper-exporting ATPase; Cp, caeruloplasmin; CS1, copper sensor 1; Ctr, copper transporter; DAPI, 4′,6-diamidino-2-phenylindole; EEA1, early endosome antigen 1; FBS, fetal bovine serum; Fpn1, ferroportin 1; GPI, glycosylphosphatidylinositol; IFNγ, interferon γ; Lamp-1, lysosome-associated membrane protein-1; LB, Luria–Bertani; LPS, lipopolysaccharide; qRT-PCR, quantitative real-time PCR; RT, reverse transcription; SCV, Salmonella-containing vacuole; TEMEA, tris[(ethylthio)ethyl]amine
- © The Authors Journal compilation © 2012 Biochemical Society