A lipid A-associated protein of Porphyromonas gingivalis, derived from the haemagglutinating domain of the RI protease gene family, is a potent stimulator of interleukin 6 synthesis

Abstract

There is evidence that the lipid A-associated proteins (LAPs) of enteric bacteria can induce the synthesis of interleukin 1 (IL-1) and therefore may be important virulence factors. Porphyromonas gingivdis is now recognized as a major pathogen in the chronic inflammatory periodontal diseases and it has previously been reported that a crude LAP fraction from this organism could induce IL-1 and interleukin 6 (IL-6) synthesis. In the present study the chemical and biological properties of the LAPs of this bacterium have been further characterized. Analysis by SDS-PAGE has shown that the LAPs comprise nine proteins of molecular masses 81,68,48,47,28,25,20,17 and 16 kDa. These LAPS, at concentrations as low as 100 ng mV, were shown to stimulate human gingival fibroblasts, human peripheral blood mononuclear cells and whole human blood t o produce the pro-inflammatory cytokine IL-6. The cytokineinducing activity of the LAPs was reduced after heat-inactivation and trypsinization, suggesting that the activity was not due to contaminating LPS. To establish which proteins in this mixture were the active cytokine inducers, the LAPs were separated by electrophoresis on polyacrylamide gels. The majority of the activity was associated with the 17 kDa LAP. N-terminal sequence analysis demonstrated that this protein was homologous t o an internal region of a conserved adhesin domain contained within a family of P. gingivdis extracellular proteins including the RI protease, Lys-gingipain, porphypain and haemagglutinin A. In addition to a role in adherence, the adhesin domain(s) of these proteins may also have cytokine-inducing properties. Furthermore, it has also been shown that the previously observed degradation of cytokines by P. gingivelis may be attributable to the catalytic domain of the RI protease. Thus, different domains within the same molecule appear t o have opposing actions on pro-inflammatory cytokine levels and the balance between these two activities may influence the cytokine status of the periodontiurn in patients with the common chronic inflammatory conditions known as the periodontal diseases.Keywords : Porphyromonas gingivalis RI protease, lipopolysaccharide, lipid A-associated protein, interleukin 1/3, interleukin 6Abbreviations: HGFs, human gingival fibroblasts; IL-1/3, interleukin 18; IL-6, interleukin 6; IAL, Limulus amoebocyte lysate; LAP, lipid A-associated protein; PBMCs, peripheral blood mononuclear cells; P-LPS, P. gingivalis LPS.The SWISS-PROT accession number for the sequence reported in this paper is P81411.

The Hemoglobin Receptor Protein ofPorphyromonas gingivalisInhibits Receptor Activator NF-κB Ligand-Induced Osteoclastogenesis from Bone Marrow Macrophages

“…The activation of NF-B and mitogen-activated protein kinases such as ERK and p38 is known to be associated with upregulation of proinflammatory cytokine gene expression. In this context, Sharp et al (45) reported that lipid A-associated proteins of P. gingivalis have the ability to induce interleukin-6 (IL-6) in human monocytes and that the active component in the lipid A-associated proteins is HbR. These findings indicate that HbR may induce various cytokines from bone marrow macrophages.…”

Human Lactoferrin Binds and Removes the Hemoglobin Receptor Protein of the Periodontopathogen Porphyromonas gingivalis

“…HbR, a 19-kilodalton protein, was intragenically encoded by an arginine-specific cysteine proteinase (Arg-gingipain, RGP)-encoding gene (rgpA), a lysine-specific cysteine proteinase (Lys-gingipain, KGP)-encoding gene (kgp), and a hemagglutinin (HA)-encoding gene (hagA) (11). Several pieces of evidence show that HbR forms a large proteinase-adhesin complex with RGP, KGP, and HA proteins that are encoded intragenically by these genes (12,13), and appears to be associated with a lipid A portion of lipopolysaccharide (LPS) (14). P. gingivalis has another RGP-encoding gene (rgpB); however, it does not encode HbR or HA (15).…”

Structural requirements for recognition of essential porphyrin byPorphyromonas gingivalis

“…Kgp-associated HA2 may also function to stabilize or anchor this cell surface coating. In this context, HA2 has also been reported to function as a lipid A binding peptide with the potential to anchor gingipains and HagA into the outer membrane [29]. Alternatively, heme might be exchanged between heme-loaded Kgp and other Hb-receptor proteins or hemophores such as HagA for uptake or cell surface storage.…”