Uptake and intracellular transportation of a bacterial surface protein in lymphoid cells

M1 protein of Streptococcus pyogenes increases production of the antibacterial CXC chemokine MIG/CXCL9 in pharyngeal epithelial cells

Streptococcus pyogenes adheres to epithelial cells of the human pharynx where it can cause pharyngitis. To counteract infection, inflamed epithelium produces peptide antibiotics, among them the CXC chemokine MIG/CXCL9. M protein is both a surface-associated and released virulence factor of S. pyogenes. Here, we show that soluble M1 protein enhances MIG gene expression and synthesis in IFN-gamma stimulated epithelial cells. M1 protein was recognized both by resting and IFN-gamma activated pharyngeal epithelial cells as detected by activation of the transcription factor NF-kappaB. Furthermore, pharmacological inhibition of NF-kappaB, decreased MIG synthesis in IFN-gamma activated cells, demonstrating a key role for NF-kappaB in mediating the enhanced response. Microarrays were used to investigate expression of recognized antimicrobial peptides in pharyngeal epithelial cells after stimulation with a combination of IFN-gamma and M1 protein. Amongst the most up-regulated and expressed genes, were several antibacterial CC and CXC chemokines. To investigate an in vivo context, pharyngeal mucosa was stimulated in vitro and MIG could be detected by immunohistochemistry in epithelial cells. The results show that epithelial cells can recognize solubilized M1 protein and intact S. pyogenes, thereby modulating an antibacterial innate host response that may have bearing on the outcome of streptococcal pharyngitis.

The kappa promoter penta-decamer binding protein CBF-A interacts specifically with nucleophosmin in the nucleus only

CArG box-binding factor-A (CBF-A) interacts with the penta-decamer (pd) element that is a conserved sequence element within mouse Vkappa promoters. The pd element acts in synergy with the octamer element to stimulate kappa transcription, especially in later stages of B cell development. To get further insight in the mechanism for CBF-A action we have characterised its protein-protein interactions. We show here that CBF-A interacts specifically with nucleophosmin (NPM). This interaction occurs via the homo-oligomerisation domain of NPM and the N-terminus of CBF-A and was exclusive for the nuclear compartment while the two proteins failed to interact in the cytosol. In contrast, CBF-A formed homocomplexes in this compartment. CBF-A was also shown to localise to the nucleoli, most likely dependent on a functional interaction with NPM. Lastly, the sequence fine specificity of CBF-A complexes in the nucleus and cytoplasm were found to differ and nuclear protein-DNA complexes were shown to contain NPM. Thus, CBF-A participates in several protein-protein interactions that may modulate its subcellular localisation and target gene specificity.

Streptococcus pyogenes infection in mouse skin leads to a time-dependent up-regulation of protein H expression

Streptococcus pyogenes protein H (sph) is an immunoglobulin-binding protein present in the Mga regulon of certain M1 serotype isolates. Although sph is present in many strains, it is frequently not expressed. In this paper we show that protein H was highly expressed after bacteria were injected into the skin of mice and were recovered from the blood, kidney, or spleen at various times postinfection. The percentage of protein H-positive colonies increased with time, reaching 100% in the spleen and kidney within 24 to 72 h postinfection. The up-regulation of sph expression was also observed in a mga mutant.

Regulation of protein H expression in M1 serotype isolates of Streptococcus pyogenes

Protein H is an immunoglobulin-binding protein expressed by certain M1 serotypes of Streptococcus pyogenes. In a recent study of invasive group A isolates, it was found that none of the 16 M1 serotype isolates analyzed expressed protein H on their surface despite the presence of the protein H gene (sph) in approximately one-third of the isolates. Selection of stable protein H-expressing variants could be achieved by infection of prtH(+) non-expressing strains into a mouse skin and recovering bacteria from the spleen. This effect was independent of the transcription regulator Mga, since a similar effect was noted in an mga(-) mutant. Thus, host passage of S. pyogenes can lead to stable high level expression of Protein H.