Figure 1.

Amino acid utilzation by intracellular Francisella. (A) Upon entry into macrophages, Francisella transiently resides in a phagosomal compartment. In this compartment, the glutamate permease GadC helps the bacterium to resist the oxidative stress generated by the NADPH oxidase. This transporter is critically required for proper bacterial phagosomal escape. Concomitantly, the synthesis of the host neutral amino acid transporter SLC1A5 is rapidly up-regulated, favoring the entry of amino acids in the infected host cell. (B) Once in the host cytosol, bacteria start their active replication and therefore require the supply of numerous additional host-derived nutrients. The AnsP permease contributes to bacterial multiplication by providing asparagine for protein synthesis. The ATG-5-independent autophagy contributes to the delivery of amino acids, enriching the cytosolic bacterial diet. At both stages, other amino acid transporters contribute to the proper feeding of the bacterium.