Human giant GTPase GVIN1 forms an antimicrobial coatomer around the intracellular bacterial pathogen Burkholderia thailandensis.

Several human pathogens exploit the kinetic forces generated by polymerizing actin to power their intracellular motility. Human cell-autonomous immune responses activated by the cytokine interferon-gamma (IFNγ) interfere with such microbial actin-based motility, yet the underlying molecular mechanisms are poorly defined. Here, we identify the IFNγ-inducible human giant GTPases GVIN1 as a novel host defense protein that blocks the bacterial pathogen Burkholderia thailandensis from high-jacking the host's actin polymerization machinery. We found that GVIN1 proteins form a coatomer around cytosolic bacteria and prevent Burkholderia from establishing force-generating actin comet tails. Coatomers formed by a second IFNγ-inducible GTPase, human guanylate binding protein 1 (GBP1), constitute a GVIN1-independent but mechanistically related anti-motility pathway. We show that coating with either GVIN1 or GBP1 displaces the Burkholderia outer membrane protein BimA, an actin nucleator that is essential for actin tail formation. Both GVIN1 and GBP1 coatomers require additional IFNγ-inducible co-factors to disrupt the membrane localization of BimA, demonstrating the existence of two parallel-acting IFNγ-inducible defense modules that evolved to target a virulence trait critical for the pathogenesis of numerous bacterial infectious agents.