Porphyromonas gingivalis, one of the major causative agents of periodontal diseases, produces large amounts of arginine- and lysine-specific cysteine proteinases in cell-associated and secretory forms, which are now referred to as Arg-gingipain (Rgp) and Lys-gingipain (Kgp), respectively. A number of studies have revealed that these proteinases are closely associated with the periodontopathogenesis of this bacterium: destruction of periodontal connective tissues, disruption of host defense mechanisms, and development and maintenance of inflammation in periodontal pockets. With respect to the physiology of the bacterium, Rgp and Kgp are indispensable for it to obtain nutrients from the environment, since it cannot utilize saccharides as carbon/energy sources for growth and totally depends on peptides and amino acids that are provided from environmental proteins by Rgp and Kgp. Furthermore, proteolytic activities of Rgp and Kgp contribute to processing/maturation of various cell-surface proteins of P. gingivalis, such as fimA fimbrilin (a subunit of major fimbriae), 75-kDa protein (a subunit of minor fimbriae), hemagglutinins, and the hemoglobin receptor protein, which are important for the bacterium to colonize and proliferate in the gingival crevice and to invade the periodontium. These findings strongly indicate critical roles of Rgp and Kgp in the virulence of P. gingivalis.

Arg-gingipain (Rgp) and Lys-gingipain (Kgp) are cysteine proteinases produced by Porphyromonas gingivalis, a major etiological bacterium of periodontal diseases. Here we show a series of small peptide analogs able to inhibit either Rgp or Kgp, which are synthesized on the basis of the cleavage site specificity of human salivary histatins by each enzyme. Among this series of compounds, carbobenzoxy-Lys-Arg-CO-Lys-N-(CH 3 ) 2 (KYT-1) and carbobenzoxy-Glu(NHN(CH 3 )Ph)-Lys-CO-NHCH 2 Ph (KYT-36) were found to be the most potent inhibitors of Rgp and Kgp, respectively, with K i values of 10 Ϫ11 to 10 Ϫ10 M order. Both inhibitors exhibited slight or no inhibition on mammalian proteinases such as trypsin and cathepsins B, L, and H. All of the virulence induced by the culture supernatant of P. gingivalis tested, including the degradation of various host proteins such as human type I collagen, immunoglobulins, fibronectin, and fibrinogen, disruption of the bactericidal activity of polymorphonuclear leukocytes, and enhancement of the vascular permeability, were strongly inhibited by a combined action of both inhibitors. The functions essential for the bacterium to grow and survive in the periodontal pocket, such as coaggregation and acquisition of amino acids, were also strongly inhibited by the combined action of both inhibitors. The disruption of the adhesion and viability of human fibroblasts and hemagglutination by the organism were strongly suppressed by a single use of KYT-1. These results thus indicate that the newly developed KYT-1 and KYT-36 both should provide a broader application in studies of this important class of enzymes and facilitate the development of new approaches to periodontal diseases.

Arg-gingipain (Rgp) and Lys-gingipain (Kgp) are Porphyromonas gingivalis cysteine proteinases implicated as major virulence factors in pathologies of periodontitis. We purified a 660-kDa cell-associated gingipain complex existing as a homodimer of two catalytically active monomers which comprises their catalytic and adhesin domains. Electron microscopy revealed that the complex was composed of a globular particle with a 10-nm external diameter possessing one or two electron-dense hole-like structures. Two-dimensional gel electrophoresis and immunoblot analyses revealed the association of lipopolysaccharide (LPS) with the catalytic domains and a hemagglutinin domain, Hgp44, of Rgp and Kgp in the complex. The complex significantly degraded human type I collagen and elastin and strongly disrupted viability of human gingival fibroblasts and umbilical vein endotherial cells with an efficiency which was higher than that of the monomeric gingipains. The native complex produced only a small amount of nitrogen dioxide, tumor necrosis factor alpha, and interleukin-6 by macrophages, whereas the heat-denatured complex resulted in increased production. Inhibition of the proteolytic activities of the gingipain complex did not up-regulate the cytokine production, indicating that the functional domains in LPS are structurally masked by the complex proteins. These results indicate the importance of the complex in evasion of host defense mechanisms as well as in host tissue breakdown.Gingipains are cysteine proteinases produced by Porphyromonas gingivalis, a gram-negative anaerobic bacterium associated with some types of periodontitis including chronic adult and progressive periodontitis (1, 14, 16, 18-20, 36, 38, 42). Gingipains are composed of Arg-specific (Arg-gingipains [Rgps]) and Lys-specific (Lys-gingipain [Kgp]) endopeptidases. Rgps are encoded by two rgp genes (rgpA and rgpB) (13,24,26,27,32,35), whereas Kgp is encoded by a single kgp gene (33,34). rgpA and rgpB are essentially identical, except that rgpB lacks most of the C-terminal adhesin domains of rgpA. Interestingly, the C-terminal adhesin domains of rgpA and kgp are highly homologous, although the propeptide and proteinase domains have no sequence similarity (21,33,36). Using various Rgp-and/or Kgp-deficient mutants as well as soluble gingipains purified from the culture supernatant of P. gingivalis strains, the virulence of the bacterium has been shown to be exclusively attributable to gingipains (1,20,(26)(27)(28). These include extensive degradation of various host proteins including collagen, fibronectin, and fibrinogen (1, 20, 34), cytokines such as interleukin-6 (IL-6), IL-8, and tumor necrosis factor alpha (TNF-␣) (7, 10, 31), complement factors C3 and C5 (47), and immunoglobulins (1, 20); disruption of the bactericidal activity of polymorphonuclear leukocytes (1,20,26); and strong induction of human fibroblast (3, 4) and human umbilical vein endothelial cell (HUVEC) (5) death. In addition, gingipains are also shown to be important for the bacterium to prol...

Arg-gingipain (Rgp) and Lys-gingipain (Kgp) are two major cysteine proteinases produced by the oral anaerobic bacterium Porphyromonas gingivalis, which has been shown to act as major pathogen in the development and progression of periodontal diseases. These enzymes are also important for this organism to proliferate and survive in periodontal pockets. Here we show that Rgp is responsible for the disruption of fibronectin-integrin interactions in human gingival fibroblasts by P. gingivalis. Fibroblasts incubated with the culture supernatant of P. gingivalis showed a time-dependent loss of the adhesion activity. Sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting revealed that fibronectin and integrin subunits alpha2, beta1 and beta3 in the fibroblast culture largely disappeared with the treatment. The detached cells became committed to death by disruption of contacts between adhesion molecules. In contrast, the culture supernatants from the Rgp-deficient mutants produced no significant changes in either cell adhesion or viability. Prior treatment of the culture supernatant of P. gingivalis with an Rgp inhibitor, but not a Kgp inhibitor, strongly inhibited the detachment of fibroblasts followed by cell death. These results suggest that Rgp disrupts the integrin-fibronectin interactions in fibroblasts, thereby contributing to the damage of periodontal tissues in periodontal diseases caused by P. gingivalis.

Accumulating evidence indicates that periodontal disease is associated with human cardiovascular diseases. The periodontal pathogen Porphyromonas gingivalis was shown to be present in atherosclerotic plaques in addition to periodontal pockets. This bacterium is known to produce two individual cysteine proteinases, Arg-gingipain (Rgp) and Lys-gingipain (Kgp). Here we show that these two enzymes are responsible for either the disruption of cytokine responses in human umbilical vein endothelial cells (HUVEC) to the bacterium infection or the loss of cell viability. The expression of interleukin-8 and monocyte chemoattractant protein-1 mRNA in HUVEC was greatly induced when infected with the wild-type strain, nevertheless, their protein levels in the culture medium were markedly decreased. This decrease was completely abolished in the cells infected with the Rgp/Kgp-null mutant, but not in either the Rgp- or Kgp-null mutants. Loss of the adhesion activity and viability of HUVEC were greatly induced by the culture supernatant of the wild-type strain and strongly inhibited by either a combination of the Rgp- and the Kgp-specific inhibitors or the deficiency of the Rgp- and Kgp-encoding genes. These findings indicate that P. gingivalis modulates the cytokine response in the cells and disrupts the adhesion activity and the viability through the cooperative action of Rgp and Kgp and thereby may contribute to pathogenesis of cardiovascular diseases as well as periodontal disease.

Arg- (Rgp) and Lys-gingipains (Kgp) are two individual cysteine proteinases produced by Porphyromonas gingivalis , an oral anaerobic bacterium, and are implicated as major virulence factors in a wide range of pathologies of adult periodontitis. Coaggregation of this bacterium with other oral bacteria is an initial and critical step in infectious processes, yet the factors and mechanisms responsible for this process remain elusive. Here we show that the initial translation products of the rgpA , kgp and hemagglutinin hagA genes are responsible for coaggregation of P. gingivalis and that the proteolytic activity of Rgp and Kgp is indispensable in this process. The rgpA rgpB kgp- and rgpA kgp hagA -deficient triple mutants exhibited no coaggregation activity with Actinomyces viscosus , whereas the kgp -null and rgpA rgpB -deficient double mutants significantly retained this activity. Consistently, the combined action of Rgp- and Kgp-specific inhibitors strongly inhibited the coaggregation activity of the bacterium, although single use of Rgp- or Kgp-specific inhibitor significantly retained this activity. We also demonstrate that the 47- and 43-kDa proteins produced from the translation products of the rgpA , kgp , and hagA genes by proteolytic activity of both Rgp and Kgp are responsible for the coaggregation of P. gingivalis.

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The periodontal pathogen Porphyromonas gingivalis produces a unique class of cysteine proteinases termed gingipains that comprises Arg-gingipain (Rgp) and Lys-gingipain (Kgp). Growing evidence indicates that these 2 types of gingipains synergistically contribute to the entire virulence of the organism and increase the risk of periodontal disease (PD) by disrupting the host immune system and degrading the host tissue and plasma proteins. Therefore, a dual inhibitor of both gingipains would have attractive clinical potential for PD therapy. In this study, a novel, potent, dual inhibitor of Rgp and Kgp was developed through structure-based drug design, and its biological potency was evaluated in vitro and in vivo. This inhibitor had low nanomolar inhibitory potency (Ki=40 nM for Rgp, Ki=0.27 nM for Kgp) and good selectivity for host proteases and exhibited potent antibacterial activity against P. gingivalis by abrogating its manifold pathophysiological functions. The therapeutic potential of this inhibitor in vivo was also verified by suppressing the vascular permeability that was enhanced in guinea pigs by the organism and the gingival inflammation in beagle dog PD models. These findings suggest that a dual inhibitor of Rgp and Kgp would exhibit noteworthy anti-inflammatory activity in the treatment of PD.