The early secretory pathway contributes to the development of the Coxiella replicative niche

CAMPOY, E.; ZOPPINO, M.; COLOMBO, M. I.

Mar del Plata

Congreso; XLIII Reunión Anual de la SAIB; 2007

Coxiella burnetii is a Gram-negative obligated intracellular bacterium. After internalization, this bacterium replicates in a large parasitophorous vacuole that has features of both phagolysosomes and autophagosomal compartments. We have previously demonstrated that early after internalization Coxiella phagosomes interact with both the endocytic and autophagic pathways. In this report we present evidence that the Coxiella-replicative vacuoles (CRV) also interact with the secretory pathway.  Rab1b is a small GTPase responsible for the anterograde transport between the Endoplasmic Reticulum and Golgi Apparatus. We have evidence that Rab1b is recruited to the CRV and that overexpression of GFP-Rab1bwt or the active GTPase defective mutant (Q67L) affects the development of the Coxiella-replicative compartment. In the present work we have examined the fusion competence of CRVs in cells overexpressing Rab1b Q67L. For this purpose Coxiella infected cells were incubated with rodamine-labeled heat inactivated Staphylococcus aureus or rodamine-dextran, to label the phagocytic and endocytic pathways, respectively. Our results indicate that fusion between CRV and both compartments was hampered. These results suggest that the GTPase defective mutant of Rab1b alters the normal development of the Coxiella vacuole by changing the fusogenic capacity of this compartment.