HACE1 and infection: HACE1 mediates recycling of β2-AR through ubiquitinating RAB11A at K145 whereas the β2-AR/HACE1 interactions are required for activation of HACE1.197 During infection by pathogenic bacterial like Legionella pneumophila, one important mechanism used by the bacteria to compromise host immune defenses is to ubiquitinate multiple RABs by the bacterial effector proteins (equivalent to E3 ligase) in an uncommon E1/E2-independent manner.198,199