Campylobacter jejuni Serine Protease HtrA Cleaves the Tight Junction Component Claudin-8
express the high temperature requirement protein A (HtrA), a secreted serine protease, which is implicated in virulence properties of the pathogen. Previous studies have shown that HtrA can cleave the epithelial transmembrane proteins occludin and E-cadherin in the tight and adherens junctions, resp...
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Veröffentlicht in: | Frontiers in cellular and infection microbiology 2020-12, Vol.10, p.590186-590186 |
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Zusammenfassung: | express the high temperature requirement protein A (HtrA), a secreted serine protease, which is implicated in virulence properties of the pathogen. Previous studies have shown that
HtrA can cleave the epithelial transmembrane proteins occludin and E-cadherin in the tight and adherens junctions, respectively. In the present report, we studied the interaction of HtrA with another human tight junction protein, claudin-8. Confocal immunofluorescence experiments have shown that
infection of the intestinal polarized epithelial cells
leads to a relocation of claudin-8. Wild-type
induced the downregulation of claudin-8 signals in the tight junctions and an accumulation of claudin-8 agglomerates in the cytoplasm, which were not seen during infection with isogenic Δ
knockout deletion or protease-inactive S197A point mutants. Western blotting of protein samples from infected
. uninfected cells revealed that an 18-kDa carboxy-terminal fragment is cleaved-off from the 26-kDa full-length claudin-8 protein, but not during infection with the isogenic Δ
mutant. These results were confirmed by
cleavage assays using the purified recombinant
HtrA and human claudin-8 proteins. Recombinant HtrA cleaved purified claudin-8
giving rise to the same 18-kDa sized carboxy-terminal cleavage product. Mapping studies revealed that HtrA cleavage occurs in the first extracellular loop of claudin-8. Three-dimensional modeling of the claudin-8 structure identified an exposed HtrA cleavage site between the amino acids alanine 58 and asparagine 59, which is in well agreement with the mapping studies. Taken together, HtrA operates as a secreted virulence factor targeting multiple proteins both in the tight and adherens junctions. This strategy may help the bacteria to open the cell-to-cell junctions, and to transmigrate across the intestinal epithelium by a paracellular mechanism and establish an acute infection. |
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ISSN: | 2235-2988 2235-2988 |
DOI: | 10.3389/fcimb.2020.590186 |