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Humans↗
Biomedical subjects
Lisa Pedersen
Publications and source records attributed to Lisa Pedersen.
Temperature regulation of the hemin storage (Hms+) phenotype of Yersinia pestis is posttranscriptional.
In Yersinia pestis, the Congo red (and hemin) binding that is characteristic of the Hms+ phenotype occurs at temperatures up to 34 degrees C but not at higher temperatures. Manifestation of the Hms+ phenotype requires at least five proteins (HmsH, -F, -R, -S, and -T) that are organized into two separate operons: hmsHFRS and hmsT. HmsH and HmsF are outer membrane proteins, while HmsR, HmsS, and HmsT are predicted to be inner membrane proteins. We have used transcriptional reporter constructs, RNA dot blots, and Western blots to examine the expression of hms operons and proteins. Our studies indicate that transcription from the hmsHFRS and hmsT promoters is not regulated by the iron status of the cells, growth temperature, or any of the Hms proteins. In addition, the level of mRNA for both operons is not significantly affected by growth temperature. However, protein levels of HmsH, HmsR, and HmsT in cells grown at 37 degrees C are very low compared to those in cells grown at 26 degrees C, while the amounts of HmsF and HmsS show only a moderate reduction at the higher growth temperature. Neither the Pla protease nor a putative endopeptidase (Y2360) encoded upstream of hmsH is essential for temperature regulation of the Hms+ phenotype. However, HmsT at 37 degrees C is sensitive to degradation by Lon and/or ClpPX. Thus, the stability of HmsH, HmsR, and HmsT proteins likely plays a role in temperature regulation of the Hms+ phenotype of Y. pestis.
Bacterial Proteins↗
The Dot/Icm type IV secretion system of Legionella pneumophila is essential for the induction of apoptosis in human macrophages.
We have previously shown that Legionella pneumophila induces caspase 3-dependent apoptosis in mammalian cells during early stages of infection. In this report, we show that nine L. pneumophila strains with mutations in the dotA, dotDCB, icmT, icmGCD, and icmJB loci are completely defective in the induction of apoptosis, in addition to their severe defects in intracellular replication and pore formation-mediated cytotoxicity. Importantly, all nine dot/icm mutants were complemented for all their defective phenotypes with the respective wild-type loci. We show that the role of the Dot/Icm type IV secretion system in the induction of apoptosis is independent of the RtxA toxin, the dot/icm-regulated pore-forming toxin, and the type II secretion system. However, the pore-forming toxin, which is triggered upon entry into the postexponential growth phase, enhances the ability of L. pneumophila to induce apoptosis. Our data provide the first example of the role of a type IV secretion system of a bacterial pathogen in the induction of apoptosis in the host cell.
Apoptosis↗