Making contact away from home: a bacterial secreted effector mediates inter-organelle communication

Inter-organelle communication via the formation of membrane contact sites (MCS) is essential for cell homeostasis. Bacterial pathogens residing in membrane bound vacuoles have exploited this biological process by secreting effector proteins that establish and function at MCS between their vacuole and host organelles. In this issue of EMBO reports, Angara et al ( 2024 ) identify a Coxiella burnetii effector protein, CbEPF1, that uses molecular mimicry of eukaryotic FFAT motifs to alter MCS between two host organelles: the endoplasmic reticulum and lipid droplets. The study provides the first example of a bacterial secreted effector that directly alters organelle-organelle contact away from the vacuole, identifying a novel mechanism by which bacterial vacuolar pathogens can rewire the host cell to promote infection. A Coxiella burnetii effector protein acts outside the boundaries of the bacteria containing vacuole. CbEPF1 promotes membrane contact site formation between host lipid droplets and endoplasmic reticulum.