title: Burkholderia cenocepacia J2315 escapes to the cytosol and actively subverts autophagy in human macrophages.
abstract: Selective autophagy functions to specifically degrade cellular cargo tagged by ubiquitination, including bacteria. Strains of the Burkholderia cepacia complex (Bcc) are opportunistic pathogens that cause life-threatening infections in patients with cystic fibrosis (CF) and chronic granulomatous disease (CGD). While there is evidence that defective macrophage autophagy in a mouse model of CF can influence B. cenocepacia susceptibility, there have been no comprehensive studies on how this bacterium is sensed and targeted by the host autophagy response in human macrophages. Here, we describe the intracellular life cycle of B. cenocepacia J2315 and its interaction with the autophagy pathway in human cells. Electron and confocal microscopy analyses demonstrate that the invading bacteria interact transiently with the endocytic pathway before escaping to the cytosol. This escape triggers theselective autophagy pathway, and the recruitment of ubiquitin, the ubiquitin-binding adaptors p62 and NDP52 and the autophagosome membrane-associated protein LC3B, to the bacterial vicinity. However, despite recruitment of these key autophagy pathway effectors, B. cenocepacia blocks autophagosome completion and replicates in the host cytosol. We find that a pre-infection increase in cellular autophagy flux can significantly inhibit B. cenocepacia replication and that lower autophagy flux in macrophages from immunocompromised CGD patients could contribute to increased B. cenocepacia susceptibility, identifying autophagy manipulation as a potential therapeutic approach to reduce bacterial burden in B. cenocepacia infections.
authors.affiliation: Signaling Systems Unit, Laboratory of Systems Biology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, 20892, USA.
authors.forename: Souhaila
authors.initials: S
authors.lastname: Al-Khodor
authors.forename: Kimberly
authors.initials: K
authors.lastname: Marshall-Batty
authors.forename: Vinod
authors.initials: V
authors.lastname: Nair
authors.forename: Li
authors.initials: L
authors.lastname: Ding
authors.forename: David E
authors.initials: DE
authors.lastname: Greenberg
authors.forename: Iain D C
authors.initials: ID
authors.lastname: Fraser
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D000818:Animals; D001343:Autophagy / Q000276:immunology*; D019121:Burkholderia Infections / Q000276:immunology*; D057508:Burkholderia cenocepacia / Q000276:immunology*; D002460:Cell Line; D003600:Cytosol / Q000382:microbiology; D004195:Disease Models, Animal; D004721:Endoplasmic Reticulum / Q000276:immunology; D006801:Humans; D057131:Immune Evasion; D008264:Macrophages / Q000276:immunology* / Q000382:microbiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008869:Microtubule-Associated Proteins / Q000276:immunology; D009687:Nuclear Proteins; D034622:RNA Interference; D034741:RNA, Small Interfering; D000071456:Sequestosome-1 Protein
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C094297:CALCOCO2 protein, human; C502070:MAP1LC3B protein, human; D008869:Microtubule-Associated Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; C099718:SQSTM1 protein, human; D000071456:Sequestosome-1 Protein