Biomedical subjects

Uwe H Stroeher

Publications and source records attributed to Uwe H Stroeher.

4 recordsLinked to original sources

PubMed2005

The two-component signal transduction system RR06/HK06 regulates expression of cbpA in Streptococcus pneumoniae.

Streptococcus pneumoniae encounters a number of environmental niches in the body, including the nasopharynx, lungs, blood, middle ear, and brain. Recent studies have identified 13 putative two-component signal-transduction systems in S. pneumoniae, which are likely to be important for gene regulation in response to external stimuli. Here, we present conclusive evidence for the regulation of choline binding protein A (CbpA), a major pneumococcal virulence factor and protective antigen, by one of these two-component signal-transduction systems. We have demonstrated divergent expression of cbpA in unmarked hk06 and rr06 deletion mutants relative to wild-type S. pneumoniae D39 by using Western immunoblotting and real-time RT-PCR. Electrophoretic mobility-shift and solid-phase binding assays have demonstrated the binding of RR06 to the promoter region of cbpA, suggesting that RR06/HK06 directly regulates cbpA transcription. We have also shown that this system is important for the ability of the pneumococcus to adhere to epithelial cells in vitro and to survive and proliferate in an in vivo mouse model. Thus, the RR06/HK06 system has a significant role in pathogenesis, both in colonization and invasive disease.

Animals↗

PubMed2003

Mutation of luxS of Streptococcus pneumoniae affects virulence in a mouse model.

The LuxS protein is required for the biosynthesis of the type 2 autoinducer (AI-2), which is involved in quorum sensing in a wide range of bacterial species. We have determined the effects of a defined luxS mutation on the virulence of Streptococcus pneumoniae. Although the luxS mutant displayed reduced virulence relative to its wild-type parent, the type 2 strain D39, it was by no means avirulent in a mouse model. After intranasal administration, the luxS mutant was able to colonize the nasopharynx of the mouse as efficiently as the wild type. However, it was less able to spread from the nasopharynx to the lungs or the blood. Intraperitoneal coadministration studies indicated that the luxS mutant was less fit and was readily outcompeted by wild-type D39. However, when administered on its own by this route, the mutant was able to proliferate and cause fatal systemic disease, albeit at a lower rate than the wild type. Western blot analysis of whole-cell lysates of the mutant and its parent did not reveal any differences in the levels of several well-characterized virulence proteins. However, analysis of Coomassie blue-stained protein profiles after separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that mutation of luxS had pleiotropic effects on protein expression in all cellular compartments. This is consistent with the product of luxS having a regulatory role in S. pneumoniae. This is the first report of a direct role for luxS (and by inference, AI-2) in the virulence of a gram-positive pathogen. However, the fact that mutagenesis of luxS does not completely attenuate S. pneumoniae has implications for the possible use of AI-2 antagonists for treatment of pneumococcal infections.

Animals↗

PubMed2002

The human complement regulator factor H binds pneumococcal surface protein PspC via short consensus repeats 13 to 15.

The innate ability of Streptococcus pneumoniae to resist complement activation and complement-mediated phagocytosis may be a direct consequence of the ability of the bacteria to bind components of the complement regulatory system. One such component, factor H (fH), is a crucial fluid-phase negative regulator of the alternative pathway of complement and is utilized by a number of pathogenic organisms to resist complement attack. The pneumococcal surface protein C (PspC [also known as CbpA] and SpsA) has been shown to bind fH, although the exact binding site within one or more of the 20 short consensus repeats (SCRs) of the molecule is not known. The purpose of the current study was to map specific SCRs on fH responsible for this binding. Initial experiments utilizing type 2 pneumococcal strain D39 and its isogenic PspC-negative derivative (D39/pspC mutant) showed that fH binding was PspC dependent. A purified recombinant protein derivative of PspC that lacked the proline-rich region (PspCDeltaPro) had a reduced binding efficiency for fH, thereby directly showing the importance of this region for the fH interaction. We have specifically shown by inhibition experiments that SCRs responsible for heparin and C3b binding of fH are not involved in binding PspC and the interaction between fH and PspC is largely hydrophobic, since no inhibition was observed in the presence of high concentrations of NaCl. Construction of SCR proteins encompassing the whole fH molecule showed that SCRs 8 to 15 (SCR 8-15) mediated binding to PspC. Further localization experiments revealed that SCR 13 and SCR 15 were required for full binding, although partial binding was retained when either SCR was removed.

Bacterial Proteins↗

PubMed2000

Distribution of IS1358 and linkage to rfb-related genes in Vibrio anguillarum.

The insertion sequence IS1358 is linked to the rfb regions of both Vibrio cholerae O1 and O139, and its location was suggestive of a role in generating new combinations of rfb genes. This provoked an examination of the distribution and localization of IS1358 in Vibrio anguillarum. S11358 was widely distributed in a number of V. anguillarum serogroups. In particular, when cosmid clones of V. anguillarum O1 were screened with IS1358 and subsequently subcloned and sequenced, it was found that rfb-like genes were linked to this region. Furthermore, when the previously identified genes virA and virB from V. anguillarum O1, now known to be involved in LPS biosynthesis, were used as probes, it was discovered that they too are present on the same large EcoRI fragment as IS1358. This clearly indicated that IS1358 was linked to the rfb region of V. anguillarum O1. Further analysis of the location of IS1358 in other serotypes indicated that V. anguillarum O2 also has IS1358 associated with rfb-like genes. In V. anguillarum O2 there is more than one copy of IS1358, suggesting that this element is a site for recombination, gene duplication or that it may be capable of transposition. Following this latter premise, IS1358 elements from a variety of V. anguillarum strains have been cloned and sequenced. Only those strains with multiple copies of IS1358 produce a full-length putative transposase, as shown by protein overexpression, further strengthening the argument that the element is transposing within these strains.

Bacterial Proteins↗