Vibrio deploys type 2 secreted lipase to esterify cholesterol with host fatty acids and mediate cell egress

Pathogens find diverse niches for survival including inside a host cell where replication occurs in a relatively protective environment. Vibrio parahaemolyticus is a facultative intracellular pathogen that uses its type 3 secretion system 2 (T3SS2) to invade and replicate inside host cells. Analysis of the T3SS2 pathogenicity island encoding the T3SS2 appeared to lack a mechanism for egress of this bacterium from the invaded host cell. Using a combination of molecular tools, we found that VPA0226, a constitutively secreted lipase, is required for escape of V. parahaemolyticus from the host cells. This lipase must be delivered into the host cytoplasm where it preferentially uses fatty acids associated with innate immune response to esterify cholesterol, weakening the plasma membrane and allowing egress of the bacteria. This study reveals the resourcefulness of microbes and the interplay between virulence systems and host cell resources to evolve an ingenious scheme for survival and escape.

Vibrio deploys Type 2 secreted lipase to esterify cholesterol with host fatty acids and mediate cell egress

Pathogens find diverse niches for survival inside host cells where replication occurs in a relatively protected environment. Vibrio parahaemolyticus, a facultative intracellular pathogen, uses its type 3 secretion system 2 (T3SS2) to invade and replicate inside host cells. However, after extensive analysis, the T3SS2 pathogenicity island appeared to lack a mechanism for egress of this bacterium from the invaded host cell. Using a combination of cell biology, microbial genetics and lipid biochemistry, we found that VPA0226, a constitutively secreted lipase, is required for escape of Vibrio parahaemolyticus from host cells. Remarkably, this lipase must be delivered into the host cytoplasm where it preferentially uses fatty acids associated with innate immune response (i.e. arachidonic acid, 20:4) to esterify cholesterol, weakening the plasma membrane and allowing egress of the bacteria. This study reveals the resourcefulness of microbes and the interplay between virulence systems to evolve an ingenious scheme for survival and escape.Impact StatementConsidering the course of a pathogen’s evolution, there appears to be interplay between secretion systems, providing unique, synergistic mechanisms to support a successful lifestyle for possibly pathogenesis, symbiosis and/or parasitosis.

HEPATIC VITAMIN A IN THE RAT AS AFFECTED BY THE ADMINISTRATION OF DIBENZANTHRACENE

1. The decreased concentrations of vitamin A in the livers of rats given dibenzanthracene probably are due to a particular effect of the carcinogen on the ability of the liver to store the vitamin and not to the production of general hepatic dysfunction. 2. The administration of dibenzanthracene to normal rats does not (a) increase significantly their hepatic content of total fat nor decrease that of phospholipid; (b) impair the ability of their livers to fabricate serum albumin; (c) impair the capacity of their livers to esterify cholesterol or phenol; (d) interfere with the hepatic synthesis and conjugation of glucuronic acid; or (e) interfere with the hepatic storage of riboflavin. 3. The simultaneous ingestion of yeast by the dibenzanthracene-treated rats further depletes their hepatic stores of vitamin A. This depletion conceivably is due to the fact that yeast alone also might deplete the liver of its vitamin A and thus a summation of two similar effects is attained. 4. The results suggest a competition between vitamin A and dibenzanthracene for some substance, possibly a protein, to which vitamin A may be bound in the liver.