VAMP7 is involved in homotypic and heterotypic fusion of C. burnetii phagosomes.

CAMPOY EM; MANSILLA ME; COLOMBO MI

Potrero de los Funes-San Luis.

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB).; 2011

Coxiella burnetii, is a Gram-negative obligate intracellular bacterium. It has been previously described that both the endocytic and the autophagic pathways contribute to Coxiella replicative vacuole (CRV) maturation. The large CRV shares characteristic of a phagolysosome-autophagolysosomal compartment. VAMP7, Vti1a and Vti1b are SNAREs involved in both the endocytic and secretory pathways, which particularly participates in the heterotypic fusion between late endosomes and lysosomes. We have previously observed that VAMP7 interacts with C. burnetii at different infection times (1h-72h p.i.). A truncated mutant of VAMP7 (VAMP7 NT) and siRNA against this SNARE protein affected the development of CRV, suggesting that VAMP7 mediates fusion events that are required for the biogenesis of the CRVs. In the present work, we observed that overexpression of VAMP7 NT affected the heterotypic fusion with late endosomes and also the homotypic fusion between Coxiella phagosomes and CRVs. On the other hand, we also detected the VAMP7 partners (Vti1a and Vti1b) in the vacuole membrane at different infection times. Moreover, treatment with chloramphenicol reduced the colocalization between C. burnetii and VAMP7, Vti1a or Vti1b, indicating that the recruitment of these SNAREs proteins is a bacteria driven process that favors the CRV biogenesis, likely by facilitating the interaction with the lysosomes.