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

CAMPOY EM, ZOPPINO FCM, COLOMBO MI

Mar del Plata, Argentina

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2007

SAIB

Coxiella 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 phagosomes interact with both the endocytic and autophagic pathways. In this report we present evidence that the -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 GFPRab1b wt or the active GTPase defective mutant (Q67L) affects the development of the -replicative compartment. In the present work we have examined the fusion competence of CRVs in cells overexpressing Rab1b Q67L. For this purpose infected cells were incubated with rodamine-labeled heat inactivated or rhodamine-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 vacuole by changing the fusogenic capacity of this compartment.