The first step in attachment of Chlamydia to host cells is thought to involve reversible binding to host heparan sulfate proteoglycans (HSPGs), polymers of variably sulfated repeating disaccharide units coupled to diverse protein backbones. However, the key determinants of HSPG structure that are involved in Chlamydia binding are incompletely defined. A previous genome-wide Drosophila RNAi screen suggested that the level of HSPG 6-O sulfation rather than the identity of the proteoglycan backbone maybe a critical determinant for binding (Elwell et al., 2008). Here, we tested in mammalian cells whether SULF1 or SULF2, human endosulfatases which remove 6-O sulfates from HSPGs, modulate Chlamydia infection. Ectopic expression of SULF1 or SULF2 in HeLa cells, which decreases cell surface HSPG sulfation, diminished C. muridarum binding and decreased vacuole formation. ShRNA depletion of endogenous SULF2 in a cell line that primarily expresses SULF2 augmented binding and increased vacuole formation. C. muridarum infection of diverse cell lines resulted in downregulation of SULF2 mRNA. In a murine model of acute pneumonia, mice genetically deficient in both endosulfatases or in SULF2 alone demonstrated increased susceptibility to C. muridarum lung infection. Collectively, these studies demonstrate that the level of HSPG 6-O sulfation is a critical determinant of C. muridarum infection in vivo and that 6-O endosulfatases are previously unappreciated modulators of microbial pathogenesis.
[Show abstract][Hide abstract] ABSTRACT: In a previous study we reported that the OmcB protein from Chlamydia pneumoniae mediates adhesion of the infectious elementary body to human HEp-2 cells by interacting with heparin/heparan sulfate-like glycosaminoglycans (GAGs) via basic amino acids located in the first of a pair of XBBXBX heparin-binding motifs. In the present study we show that the basic amino acid at positions 57 (arginine) in the first XBBXBX motif, the basic amino acids at position 61 (arginine) in the second motif, and another (lysine 69) C-terminal to it, play key roles in the interaction. In addition, we show that discrimination between heparin-dependent and -independent adhesion by C. trachomatis OmcBs is entirely dependent on three variable amino acids in the so-called variable domain C-terminal to the conserved XBBXBX motif. Here, the predicted conformational change in the secondary structure induced by the proline at position 66 seems to be crucial for heparin recognition. Finally, we performed neutralization experiments using different anti-heparan sulfate antibodies to gain insight into the nature of the GAGs recognized by OmcB. The results suggest that C. trachomatis serovar L2 OmcB may interact with 6-O-sulfated domains of heparan sulfate, while C. pneumoniae OmcB apparently interacts with domains of heparan sulfate harboring a diverse subset of O-sulfations.
Journal of bacteriology 09/2013; 195(23). DOI:10.1128/JB.00780-13 · 2.81 Impact Factor
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