Bacterial effectors targeting the host ubiquitin system

Intracellular bacteria are largely shielded from humoral immunity but remain vulnerable to cell-autonomous defense mechanisms, many of which depend on the ubiquitin system. To evade autophagy and lysosomal targeting, numerous bacteria have evolved secreted effectors that disrupt or manipulate the host ubiquitin machinery to their advantage. Bacterial deubiquitinases can protect bacterial surfaces or their enclosing vacuoles from ubiquitin coating and interfere with host inflammatory and cell death pathways. Conversely, bacterial ubiquitin ligases may induce the degradation of host proteins, engaging in an evolutionary arms race with host ligases. In addition, ubiquitin-modifying and ubiquitin-crosslinking effectors can disable major host defense signaling pathways. In the present overview, we summarize currently known ubiquitin-directed effectors, their targets, and their roles in bacteria-host interaction.