Invaded microorganisms or extracellular particular debris are recognized by specific immune cells, in particular macrophages. These remove the particles by uptake into a membrane-bound phagosome which will mature into a phagolysosome. Some lysosomal hydrolases, proton-pumping ATPase and lysosomal membrane proteins play critical roles in killing and digestion of ingested microorganisms in a phagolysosome, as has been shown for some of them using transgenic mouse models and cells derived from them. This application proposes to probe processing of phagosomes containing model particles or bacterial intracellular pathogens in macrophages, granulocytes and embryonic fibroblasts with deletion in the genes for the abundant lysosome membrane proteins LAMP-1, LAMP-2, LIMP-2 and LIMP-1/CD63, in LAMP-1 as well as LAMP-2, or in transmembrane subunits of the protonpumping vacuolar ATPase which is crucial for function of the endocytic pathway. Regular and diverted phagosome maturation will be followed microscopically and biochemically in cells infected with harmless microorganisms (Escherichia coli safety strains, baker’s yeast) or a pathogenic bacterium (Listeria monocytogenes) or fed with inert latex bead particles. In addition, the effects of host cell mutation on intra-host cell multiplication or killing will be tested. The results forseen will help to molecularly understand if and how major membrane proteins of late endosomes and lysosomes orchestrate fusion between these late endocytic compartments and different types of phagosomes and how they contribute to pathogen killing.
DFG Programme
Priority Programmes
