Host CD59 Potentiates the Type III Secretion System in <i>Yersinia pseudotuberculosis</i>

Type III secretion systems (T3SS) play critical roles in disease for many Gram-negative pathogens. For <i>Yersinia pseudotuberculosis</i> ( <i>Yptb</i> ), the machinery delivers the Yop bacterial effectors into host cells, misregulating cytoskeletal components and sabotaging immune defenses. Although the structural details of T3SS assembly have been extensively studied, the intimate interactions between T3SS components and the target host plasma membrane are poorly characterized. A previous RNA interference (RNAi) study identified the GPI-linked surface protein CD59 as a critical host component that supports T3SS translocation pore formation and effector movement into the host cytosol. We show here that both depletion and increased levels of CD59 reduced <i>Yptb</i> T3SS pore formation and Yop translocation into host target cells. Enzymatic removal of all GPI-linked surface proteins from wild-type cells prior to <i>Yptb</i> infection had no effect on T3SS function, indicating that neither CD59 nor other GPI-linked proteins were receptors for the T3SS machinery. Consistent with its importance in supporting the T3SS function, efficient bacterial effector-mediated focal adhesion disassembly was dependent on CD59. Depletion of CD59 interfered with the rearrangement of the lipid raft marker GM1 that occurs after <i>Yptb</i> adhesion to host cells, indicating that CD59 supports lipid microdomain dynamics. Consistent with a role in modulating lipid composition, the loss of CD59 resulted in the accumulation of phosphatidylcholine lipids and alterations in both fatty acid chain lengths and fatty acid saturation levels. This work points to a role for CD59 in supporting efficient T3SS function by maintaining plasma membrane dynamics necessary to support efficient T3SS function.