[S4-1] Legionella exploits host cellular systems using unconventional post-translational modifications
Many bacterial pathogens secrete effector proteins directly into host cells to accomplish infection. Using these effectors, bacteria exploit host cellular systems to evade the immune system and promote infection. A particularly interesting subset of the effectors are enzymes that catalyze chemical reactions never being characterized in eukaryotic cells. In this presentation, we introduce the intracellular bacterial pathogen Legionella pneumophila which employs more than 300 effector proteins for biogenesis and remodeling of a replicative niche to survive in host cell. In this process, several effector proteins are utilized to exploit the host ubiquitin system. Some of them function as ubiquitin ligases, including unprecedented enzymes that catalyze ubiquitination through unconventional mechanisms. Furthermore, recent studies have identified many L. pneumophila effector proteins that can reverse the infection-mediated ubiquitination. Most recently, we identified a Legionella deubiquitinase which cleaves ubiquitin chains on a v-SNARE Sec22b and showed the biological implication of its function on the remodeling of the replicative vacuole. Through the topic regarding the complexity of ubiquitin-related bacterial effector array with reversible functions, we would like to discuss sophisticated strategies to adapt to the host environment and enable bacteria to survive in host cells.