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Molecular mechanism by which surface antigen HP0197 mediates host cell attachment in the pathogenic bacteria Streptococcus suis.

ABSTRACT: Streptococcus suis, one of the most important and prevalent pathogens in swine, presents a major challenge to global public health. HP0197 is an S. suis surface antigen that was previously identified by immunoproteomics and can bind to the host cell surface. Here, we investigated the interaction between HP0197 and the host cell surface glycosaminoglycans (GAGs) using indirect immunofluorescence and cell adhesion inhibition assays. In addition, we determined that a novel 18-kDa domain in the N-terminal region of HP0197 functions as the GAG-binding domain. We then solved the three-dimensional structures of the N-terminal 18-kDa and C-terminal G5 domains using x-ray crystallography. Based on this structural information, the GAG-binding sites in HP0197 were predicted and subsequently verified using site-directed mutagenesis and indirect immunofluorescence. The results indicate that the positively charged residues on the exposed surface of the 18-kDa domain, which are primarily lysines, likely play a critical role in the HP0197-heparin interaction that mediates bacterium-host cell adhesion. Understanding this molecular mechanism may provide a basis for the development of effective drugs and therapeutic strategies for treating streptococcal infections.

SUBMITTER: Yuan ZZ

PROVIDER: S-EPMC3543045 | biostudies-literature | 2013 Jan

REPOSITORIES: biostudies-literature

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Molecular mechanism by which surface antigen HP0197 mediates host cell attachment in the pathogenic bacteria Streptococcus suis.

Yuan Zeng-zhi ZZ Yan Xiao-jie XJ Zhang An-ding AD Chen Bo B Shen Yue-quan YQ Jin Mei-lin ML

The Journal of biological chemistry 20121126 2

Streptococcus suis, one of the most important and prevalent pathogens in swine, presents a major challenge to global public health. HP0197 is an S. suis surface antigen that was previously identified by immunoproteomics and can bind to the host cell surface. Here, we investigated the interaction between HP0197 and the host cell surface glycosaminoglycans (GAGs) using indirect immunofluorescence and cell adhesion inhibition assays. In addition, we determined that a novel 18-kDa domain in the N-te ...[more]

PMID: 23184929

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Project description:The capsular polysaccharide (CPS) represents a key virulence factor for most encapsulated streptococci. Streptococcus suis and Group B Streptococcus (GBS) are both well-encapsulated pathogens of clinical importance in veterinary and/or human medicine and responsible for invasive systemic diseases. S. suis and GBS are the only Gram-positive bacteria which express a sialylated CPS at their surface. An important difference between these two sialylated CPSs is the linkage between the side-chain terminal galactose and sialic acid, being ?-2,6 for S. suis but ?-2,3 for GBS. It is still unclear how sialic acid may affect CPS production and, consequently, the pathogenesis of the disease caused by these two bacterial pathogens. Here, we investigated the role of sialic acid and the putative effect of sialic acid linkage modification in CPS synthesis using inter-species allelic exchange mutagenesis. To this aim, a new molecular biogenetic approach to express CPS with modified sialic acid linkage was developed. We showed that sialic acid (and its ?-2,6 linkage) is crucial for S. suis CPS synthesis, whereas for GBS, CPS synthesis may occur in presence of an ?-2,6 sialyltransferase or in absence of sialic acid moiety. To evaluate the effect of the CPS composition/structure on sialyltransferase activity, two distinct capsular serotypes within each bacterial species were compared (S. suis serotypes 2 and 14 and GBS serotypes III and V). It was demonstrated that the observed differences in sialyltransferase activity and specificity between S. suis and GBS were serotype unrestricted. This is the first time that a study investigates the interspecies exchange of capsular sialyltransferase genes in Gram-positive bacteria. The obtained mutants represent novel tools that could be used to further investigate the immunomodulatory properties of sialylated CPSs. Finally, in spite of common CPS structural characteristics and similarities in the cps loci, sialic acid exerts differential control of CPS expression by S. suis and GBS.

Dataset Information

Molecular mechanism by which surface antigen HP0197 mediates host cell attachment in the pathogenic bacteria Streptococcus suis.

Publications

Molecular mechanism by which surface antigen HP0197 mediates host cell attachment in the pathogenic bacteria Streptococcus suis.

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