The Legionella pneumophila F-box protein Lpp2082 (AnkB) modulates ubiquitination of the host protein parvin B and promotes intracellular replication

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M. Lomma, D. Dervins-Ravault, M. Rolando, T. Nora, H. J. Newton, F. M. Samson, T. Sahr, L. Gomez-Valero, M. Jules, E. L. Hartland, C. Buchrieser

The environmental pathogen Legionella pneumophila encodes three proteins containing F-box domains and additional protein[ndash]protein interaction domains, reminiscent of eukaryotic SCF ubiquitin[ndash]protein ligases. Here we show that the F-box proteins of L. pneumophila strain Paris are Dot/Icm effectors involved in the accumulation of ubiquitinated proteins associated with the Legionella-containing vacuole. Single, double and triple mutants of the F-box protein encoding genes were impaired in infection of Acanthamoeba castellanii, THP-1 macrophages and human lung epithelial cells. Lpp2082/AnkB was essential for infection of the lungs of A/J mice in vivo, and bound Skp1, the interaction partner of the SCF complex in mammalian cells, similar to AnkB from strain AA100/130b. Using a yeast two-hybrid screen and co-immunoprecipitation analysis we identified ParvB a protein present in focal adhesions and in lamellipodia, as a target. Immunofluorescence analysis confirmed that ectopically expressed Lpp2082/AnkB colocalized with ParvB at the periphery of lamellipodia. Unexpectedly, ubiquitination tests revealed that Lpp2082/AnkB diminishes endogenous ubiquitination of ParvB. Based on these results we propose that L. pneumophila modulates ubiquitination of ParvB by competing with eukaryotic E3 ligases for the specific protein[ndash]protein interaction site of ParvB, thereby revealing a new mechanism by which L. pneumophila may employ translocated effector proteins to promote bacterial survival.