Functional Characterization of two substrates of the Brucella abortus Type-IV Secretion System

HERRMANN, C. K.; MELLI LJ; COMERCI D. J

Mendoza

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular (SAIB); 2012

Sociedad Argentina de Investigaciones Bioquímica y Biología Molecular

The delivery of effector proteins into the host cell is the central function of the VirB protein complex, the Type IV Secretion System of B. abortus. Effectors proteins target, modulate and subvert diverse cellular processes allowing the pathogen to evade lysosome fusion and to create an organelle permissive for intracellular replication called the Brucella-containing vacuole (BCV). To identify VirB substrates, we performed a combined in silico-in vivo screening and found 3 proteins that are translocated in a VirB-dependent manner: BPE043, a hypothetical protein with prediction of 4 apolipoprotein domains; BPE005, a putative cyclic nucleotide-binding protein and BPE275, a member of the rhomboid family. To unveil the function of these proteins, we generated B. abortus clean deletion mutants of those genes and analyzed their phenotype. Our results revealed that two mutants displayed different but remarkable defects in virulence. B. abortus Äbpe005 showed a significant increase in LAMP-1 acquisition and was affected in the biogenesis of the replicative BCV, thus, its survival and intracellular replication was impaired. On the other hand, B. abortus Äbpe275 displayed reduced adhesion to host cell but the intracellular replication stages were not affected in this mutant. These results remark the importance of VirB and effector proteins for the Brucella-host cell interaction