Determining the Effects of Legionella pneumophila SidE Effector Proteins on Host Vesicular Trafficking

Abstract

Legionella pneumophila is an opportunistic intracellular pathogen responsible for Legionnaires’ disease in humans. Upon infection, L. pneumophila forms the Legionella‐containing vacuole (LCV), shielding itself from the host immune response. From the LCV, L. pneumophila uses a specialized secretion system to translocate over 350 effector proteins into the host cell. Effectors target and manipulate host pathways in order to optimize the host’s cellular environment to support L. pneumophila replication (1). One important cellular process targeted during infection is endocytic recycling. Recycling pathways are generally categorized as slow or fast, depending on the time it takes for endocytosed cargo to return to the plasma membrane. Rab11 is a key regulator of the slow endocytic recycling pathway (2) and it moves along microtubules partly through its interaction with Rab11‐FIP1A. It was previously shown that mutation of Rab11‐FIP1A disrupts transferrin recycling (3). In the context of infection by L. pneumophila, our group has shown that transferrin recycling in human macrophages is inhibited early during infection. We hypothesize that the L. pneumophila effectors protein family SidE is at least partly responsible for this defect. Pull‐down assays revealed that interaction between Rab11 and Rab11‐FIP1A is disrupted in the presence of SdeC. In transiently transfected CHO cells, GFP‐Rab11‐FIP1A is found on vesicles in the perinuclear region. However, when GFP‐Rab11‐FIP1A and mCherry‐SdeC are co‐expressed in CHO cells, we observed that GFP‐Rab11‐FIP1A changed its localization to several enlarged structures. We are investigating whether SdeC’s ubiquitination activity is responsible for disrupting interaction of Rab11 with Rab11‐FIP1A. These results will help establish the effects of ubiquitination by SidE effector proteins on the slow recycling pathway.Support or Funding Information