Relationship between C. burnetii-containing vacuole and host actin cytoskeleton

BERON, W

Sao Paulo

Congreso; XV Meeting of the Brazilian Society for Cell Biology; 2010

Coxiella burnetii, the causative agent of human Q fever, is an obligate intracellular bacterium which generates in the host cell a large parasitophorous vacuole (PV) with lysosomal characteristics. We have demonstrated that F-actin not only is recruited to, but is also involved in the formation of the typical PV. Treatment of infected cells with latrunculin B, an F-actin-depolymerizing agent, alters PV development. The small PVs formed in latrunculin-treated cells were loaded with transferrin and Lysotracker and labeled with an antibody against cathepsin D, suggesting that latrunculin B did not affect vacuole cargo and its lysosomal characteristics. Nevertheless, the vacuoles were unable to fuse with latex bead phagosomes. It is known that actin dynamics are regulated by the Rho family GTPases. To assess the role of these GTPases in PV formation, infected cells were transfected with pEGFP: Rac1, Cdc42 or RhoA wild types and mutants. Rac1 did not show significant PV association. In contrast, PVs were decorated by both wild type and constitutively-active mutants of Cdc42 and RhoA. This association was inhibited by treatment of infected cells with chloramphenicol, suggesting a role for bacterial protein synthesis in the recruitment of these proteins. Interestingly, a decrease in vacuole size was observed in cells expressing dominant-negative RhoA; however, these small vacuoles accumulated transferrin, Lysotracker and DQ-BSA. In summary, these results suggest that actin, likely modulated by the GTPases RhoA and Cdc42 and by bacterial proteins, is involved in the formation of the typical PV.