Depletion of the Ubiquitin-binding Adaptor Molecule SQSTM1/p62 from Macrophages Harboring cftr ΔF508 Mutation Improves the Delivery of Burkholderia cenocepacia to the Autophagic Machinery

• Published in: The Journal of biological chemistry 2013-01, Vol.288 (3), p.2049-2058
• Main Authors: Abdulrahman, Basant A., Khweek, Arwa Abu, Akhter, Anwari, Caution, Kyle, Tazi, Mia, Hassan, Hoda, Zhang, Yucheng, Rowland, Patrick D., Malhotra, Sankalp, Aeffner, Famke, Davis, Ian C., Valvano, Miguel A., Amer, Amal O.
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - antagonists & inhibitors; Adaptor Proteins, Signal Transducing - genetics; Adaptor Proteins, Signal Transducing - metabolism; Animals; Autophagy; Autophagy - genetics; Bacterial Pathogenesis; Biomarkers - metabolism; Burkholderia cenocepacia; Burkholderia cenocepacia - physiology; Burkholderia Infections - complications; Burkholderia Infections - genetics; Burkholderia Infections - metabolism; Burkholderia Infections - microbiology; Cystic Fibrosis; Cystic Fibrosis - complications; Cystic Fibrosis - genetics; Cystic Fibrosis - metabolism; Cystic Fibrosis - microbiology; Cystic Fibrosis Transmembrane Conductance Regulator - genetics; Cystic Fibrosis Transmembrane Conductance Regulator - metabolism; Gene Expression; Heat-Shock Proteins - antagonists & inhibitors; Heat-Shock Proteins - genetics; Heat-Shock Proteins - metabolism; Humans; Innate Immunity; Macrophages - metabolism; Macrophages - microbiology; Macrophages - pathology; Mice; Mice, Transgenic; Microbial Viability; Microtubule-Associated Proteins - metabolism; Molecular Bases of Disease; Phagosomes - metabolism; Protein Transport; RNA, Small Interfering - genetics; Sequestosome-1 Protein; Trafficking; Transfection; Ubiquitin - genetics; Ubiquitin - metabolism
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M112.411728

Cystic fibrosis is the most common inherited lethal disease in Caucasians. It is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), of which the cftr ΔF508 mutation is the most common. ΔF508 macrophages are intrinsically defective in autophagy because of the sequestration of essential autophagy molecules within unprocessed CFTR aggregates. Defective autophagy allows Burkholderia cenocepacia (B. cepacia) to survive and replicate in ΔF508 macrophages. Infection by B. cepacia poses a great risk to cystic fibrosis patients because it causes accelerated lung inflammation and, in some cases, a lethal necrotizing pneumonia. Autophagy is a cell survival mechanism whereby an autophagosome engulfs non-functional organelles and delivers them to the lysosome for degradation. The ubiquitin binding adaptor protein SQSTM1/p62 is required for the delivery of several ubiquitinated cargos to the autophagosome. In WT macrophages, p62 depletion and overexpression lead to increased and decreased bacterial intracellular survival, respectively. In contrast, depletion of p62 in ΔF508 macrophages results in decreased bacterial survival, whereas overexpression of p62 leads to increased B. cepacia intracellular growth. Interestingly, the depletion of p62 from ΔF508 macrophages results in the release of the autophagy molecule beclin1 (BECN1) from the mutant CFTR aggregates and allows its redistribution and recruitment to the B. cepacia vacuole, mediating the acquisition of the autophagy marker LC3 and bacterial clearance via autophagy. These data demonstrate that p62 differentially dictates the fate of B. cepacia infection in WT and ΔF508 macrophages. Background: Cystic fibrosis is characterized by defective autophagy and increased Burkholderia cenocepacia infection. Results: The depletion of SQSTM1/p62 from ΔF508 macrophages improves bacterial clearance via autophagy. Conclusion: p62 expression level determines the fate of B. cepacia infection in ΔF508 macrophages. Significance: Our study reveals the role of p62 in diseases characterized by protein aggregates that compromise autophagy by consuming essential autophagy molecules.