TNF is an essential effector molecule for the eradication of intracellular pathogens. Lack of TNF or TNF-receptor 1 (TNFR1) is associated with a high susceptibility to infections with intracellular bacteria such as Listeria monocytogenes (LM). We have shown that internalized TNFR1 complexes are instrumental for mediating apoptosis and activation of a lysosomal compartment. In addition, we found that an adenovirus protein, E3-14.7K can inhibit selectively TNFR1 endocytosis and apoptosis. Therefore, we hypothesised that these TNFR1 receptosomes deliver activated lysosomal components to the LM-containing phagosomes to mediate their listericidal effects. By confocal microscopy we were able to demonstrate the colocalisation of TNFR1 receptosomes with LM-containing phagosomes. We have adopted a protocol to magnetize LM and to purify phagosomes from infected cells and analyse the recruitment of signature proteins. To elucidate the specific contribution of TNFR1 receptosomes we plan to infect macrophages from TNFR1- and IFN-γ-deficient mice and to analyse their phagosomal components. In addition, to analyse the inhibition of TNFR1 endocytosis in vivo we have established an E3-14.7K transgenic mouse and work is in progress to generate a mouse expressing an internalisation-deficient TNFR1.
