The Role of the Phagosomal Transporter (Pht) Family of Proteins in Legionella pneumophila Pathogenesis
J. Sauer, M. Swanson
2006
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Key Takeaway Key Takeaway: Phagosomal transporter proteins play a crucial role in Legionella pneumophila pathogenesis, with some essential for growth within macrophages and others for replication.
Abstract
A central aspect of the pathogenesis of Legionella pneumophila is its ability to differentiate in response to nutrient availability. The phagosomal transporter (Pht) proteins are members of the major facilitator superfamily of proteins which are ATP-independent transporters that perform diverse functions in both prokaryotic and eukaryotic cells. One of these transporters, PhtA, is required by intracellular L. pneumophila for threonine acquisition, differentiation, and growth. Accordingly, the authors have developed a model in which Pht proteins are responsible for acquisition of nutrients in the nascent phagosome; have postulated that this process is absolutely required both for L. pneumophila differentiation and growth within host macrophages. Knowing that nutrient starvation in broth triggers differentiation of replicative cells to the transmissive form, the authors tested if threonine limitation, caused by mutation of the phtA locus, impaired differentiation of intracellular bacteria. Analysis of mutants that lack one of each of the other members of the Pht family indicated that some of the putative transporters are required for growth within mouse macrophages, but others are not. In particular, the phtB, phtG, phtH, phtIK genes are not essential for growth within macrophages, while phtC, phtD, phtE, phtF, and phtJ are required for replication.