title: The ability of Listeria monocytogenes PI-PLC to facilitate escape from the macrophage phagosome is dependent on host PKCbeta.
abstract: Listeria monocytogenes are facultative intracellular pathogenic bacteria that can infect macrophages as well as non-professional phagocytes. After entry in the host cell, the bacteria escape from the phagosome into the cytoplasm. In murine macrophages and in cell lines derived from these cells, escape of L. monocytogenes from the phagosome is absolutely dependent on listeriolysin O (LLO) and facilitated by a secreted phosphatidylinositol-specific phospholipase C (PI-PLC). Work in this laboratory has previously demonstrated a LLO and PI-PLC-dependent translocation of host PKCbeta isoforms. Pharmacological inhibition of PKCbeta resulted in a significant reduction in permeabilization of the phagosome, and in the number of bacteria reaching the cytosol. These findings led to the prediction that the bacterial PI-PLC promotes escape through the production of diacylglycerol leading to the activation of host PKCbeta. To test this hypothesis, bone marrow-derived macrophages (BMMf) obtained from PKCbeta knockout (PKCbetaKO) or C57Bl/6 mice were infected with L. monocytogenes. We observed that wild-type L. monocytogenes escapes from the phagosome of PKCbetaKO BMMf as well as from C57Bl/6 BMMf. However, in PKCbetaKO BMMf, L. monocytogenes uses a PI-PLC-independent, but phosphatidylcholine-preferring PLC (PC-PLC)-dependent pathway to facilitate escape. These findings strongly support the hypothesis that PI-PLC promotes escape through mobilization of host PKCbeta.
authors.affiliation: Department of Microbiology, School of Medicine, University of Pennsylvania, Philadelphia, PA 19104-6076, USA.
authors.forename: Mathilde A
authors.initials: MA
authors.lastname: Poussin
authors.forename: Michael
authors.initials: M
authors.lastname: Leitges
authors.forename: Howard
authors.initials: H
authors.lastname: Goldfine
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000382:microbiology; D002460:Cell Line; D008089:Listeria monocytogenes / Q000472:pathogenicity*; D008088:Listeriosis / Q000276:immunology / Q000382:microbiology; D008264:Macrophages / Q000382:microbiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010588:Phagosomes / Q000382:microbiology*; D054801:Phosphoinositide Phospholipase C / Q000378:metabolism*; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D064546:Protein Kinase C beta; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D011493:Protein Kinase C; D064546:Protein Kinase C beta; D010738:Type C Phospholipases; D054801:Phosphoinositide Phospholipase C; C105598:phosphatidylcholine-specific phospholipase C