ACTR2 and infection: For example, Legionella pneumophila effector Lpg1137 binds to and cleaves syntaxin17, a SNARE protein that regulates Drp1 activity during infection and induces mitochondrial fragmentation.45 In addition, L. pneumophila effector MitF triggers the activation of the Wiskott – Aldrich syndrome protein (WASP) and actin-related protein 2/3 complex (Arp2/3).13 Actin nucleation by WASP/Arp2/3 progressively facilitates Drp1-mediated mitochondrial fragmentation.13 In this study, S. Tm exploits the T3SS1 effector SipA to inhibit mitochondrial fragmentation in a Drp1-dependent manner (Figure 6).