The periodontal pathogen Porphyromonas gingivalis is known to express 2 distinct types of fimbriae: FimA and Mfa1 fimbriae. However, we previously reported that fimbria-like structures were found in ...a P. gingivalis strain in which neither FimA nor Mfa1 fimbriae were detected. In this study, we identified a major protein in the bacterial lysates of the strain, which has been reported as the 53-kDa major outer membrane protein of P. gingivalis (53K protein) and subsequently reported as a major fimbrilin of a novel-type fimbria. Sequencing of the chromosomal DNA of the strain showed that the 53k gene (encoding the 53K protein) was located at a locus corresponding to the mfa1 gene (encoding the Mfa1 protein, which is a major fimbrilin of Mfa1 fimbriae) of the ATCC 33277 type strain. However, the 53K and Mfa1 proteins showed a low amino acid sequence homology and different antigenicity. The 53K protein was detected in 34 of 84 (41%) P. gingivalis strains, while the Mfa1 protein was detected in 44% of the strains. No strain expressed both 53K and Mfa1 proteins. Additionally, fimbriae were normally expressed in mutants in which the 53k and mfa1 genes were interchanged. These results indicate that the 53K protein is another major fimbrilin of Mfa1 fimbriae in P. gingivalis.
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CMK, NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Fimbriae are protein-based filamentous appendages that protrude from the bacterial cell surface and facilitate host adhesion. Two types of fimbriae, FimA and Mfa1, of the periodontal pathogen ...Porphyromonas gingivalis are responsible for adherence to other bacteria and to host cells in the oral cavity. Both fimbrial forms are composed of 5 proteins, but there is limited information about their polymerization mechanisms. Here, the authors evaluated the function of Mfa5, one of the Mfa1 fimbrial accessory proteins. Using mfa5 gene disruption and complementation studies, the authors revealed that Mfa5 affects the incorporation of other accessory proteins, Mfa3 and Mfa4, into fibers and the expression of fimbriae on the cell surface. Mfa5 is predicted to have a C-terminal domain (CTD) that uses the type IX secretion system (T9SS), which is limited to this organism and related Bacteroidetes species, for translocation across the outer membrane. To determine the relationship between the putative Mfa5 CTD and the T9SS, mutants were constructed with in-frame deletion of the CTD and deletion of porU, a C-terminal signal peptidase linked to T9SS-mediated secretion. The ∆CTD-expressing strain presented a similar phenotype to the mfa5 disruption mutant with reduced expression of fimbriae lacking all accessory proteins. The ∆porU mutants and the ∆CTD-expressing strain showed intracellular accumulation of Mfa5. These results indicate that Mfa5 function requires T9SS-mediated translocation across the outer membrane, which is dependent on the CTD, and subsequent incorporation into fibers. These findings suggest the presence of a novel polymerization mechanism of the P. gingivalis fimbriae.
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CMK, NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Autism spectrum disorder (ASD) is associated with two core symptoms (social communication deficits and stereotyped repetitive behaviors) in addition to a number of comorbidities. There are no ...FDA-approved drugs for the core symptoms and the changes that underlie these behaviors are not fully understood. One hypothesis is an imbalance of the excitation (E)/inhibition (I) ratio with excessive E and diminished I occurring in specific neuronal circuits. Data suggests that both gamma-aminobutyric acid
(GABA
) and α7 nicotinic acetylcholine receptors (nAChRs) significantly impact E/I. BTBR T
tf/J (BTBR) mice are a model that display an autism-like phenotype with impaired social interaction and stereotyped behavior. A β2/3-subunit containing GABA
receptor (GABA
R) subtype selective positive allosteric modulator (PAM), 2-261, and an α7 nAChR subtype selective PAM, AVL-3288, were tested in social approach and repetitive self-grooming paradigms. 2-261 was active in the social approach but not the self-grooming paradigm, whereas AVL-3288 was active in both. Neither compound impaired locomotor activity. Modulating α7 nAChRs alone may be sufficient to correct these behavioral and cognitive deficits. GABAergic and nicotinic compounds are already in various stages of clinical testing for treatment of the core symptoms and comorbidities associated with ASD. Our findings and those of others suggest that compounds that have selective activities at GABA
R subtypes and the α7 nAChR may address not only the core symptoms, but many of the associated comorbidities as well and warrant further investigation in other models of ASD.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, PNG, SAZU, SBCE, SBJE, UL, UM, UPUK, ZRSKP
Indigenous peoples of the Americas are proficient in botanical medicine. KCNQ family voltage-gated potassium (Kv) channels are sensitive to a variety of ligands, including plant metabolites. Here, we ...screened methanolic extracts prepared from 40 Californian coastal redwood forest plants for effects on Kv current and membrane potential in
oocytes heterologously expressing KCNQ2/3, which regulates excitability of neurons, including those that sense pain. Extracts from 9 of the 40 plant species increased KCNQ2/3 current at -60 mV by ≥threefold (maximally, 15-fold by
) and/or hyperpolarized membrane potential by ≥-3 mV (maximally, -11 mV by
). All nine plants have traditionally been used as both analgesics and gastrointestinal therapeutics. Of two extracts tested, both acted as KCNQ-dependent analgesics in mice. KCNQ2/3 activation at physiologically relevant, subthreshold membrane potentials by tannic acid, gallic acid and quercetin provided molecular correlates for analgesic action of several of the plants. While tannic acid also activated KCNQ1 and KCNQ1-KCNE1 at hyperpolarized, negative membrane potentials, it inhibited KCNQ1-KCNE3 at both negative and positive membrane potentials, mechanistically rationalizing historical use of tannic acid-containing plants as gastrointestinal therapeutics. KCNE dependence of KCNQ channel modulation by plant metabolites therefore provides a molecular mechanistic basis for Native American use of specific plants as both analgesics and gastrointestinal aids.
The periodontitis-associated pathogen Porphyromonas gingivalis colonizes and forms a biofilm in gingival crevices through fimbriae. It is known that the often-used strains ATCC 33277 and 381 produce ...long FimA fimbriae. We found a possible nonsense mutation within fimB, immediately downstream from fimA, coding a major subunit of FimA fimbriae of the strains. Indeed, P. gingivalis strains, except for ATCC 33277 and 381, universally expressed FimB, the gene product of fimB. Electron micrographs revealed that a FimB-restored strain had short and dense, “toothbrush”-like, FimA fimbriae. FimA overexpression elongated the fimbriae, whereas FimB overexpression shortened them. FimB restoration increased production of FimA and its accessory proteins. Thus, FimB regulates the length and expression of FimA fimbriae. Additionally, FimB restoration significantly reduced the release of FimA fimbriae from the cell surface, suggesting that FimB functions as an anchor of the fimbriae. The restoration enhanced adherent activity as well.
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CMK, NUK, OILJ, SAZU, UKNU, UL, UM, UPUK
Background and Objective: Research on Porphyromonas gingivalis, a periodontopathogen, has provided a tremendous amount of information over the last 20 years, which may exceed in part than that on ...other closely related members in terms of phylogenetic as well as proteomic criteria, including Bacteroides fragilis and B. thetaiotaomicron as major anaerobic, opportunistic pathogens in the medical field. In this minireview, we focused on recent research findings concerning surface components such as outer membrane proteins and fimbriae, of P. gingivalis.
Material and Methods: Elucidation of the surface components in P. gingivalis was especially difficult because outer membrane proteins are tightly bound to lipopolysaccharide and they are resistant to dissociation and separation from each other, even during sodium dodecyl sulfate–polyacrylamide gel electrophoresis, unless samples are appropriately heated. In addition, P. gingivalis is asaccharolytic and therefore a potent proteolytic bacterium, another factor causing difficulty in research. The study of the surface components was carefully carried out considering these unique features in P. gingivalis when compared with other gram‐negative bacteria, including Escherichia coli and Pseudomonas aeruginosa.
Results: Separation of outer membrane proteins, and characterization of OmpA‐like proteins and RagAB as major proteins, is described herein. Our recent findings on FimA and Mfa1 fimbriae, two unique appendages in this organism, and on their regulation of expression are also described briefly.
Conclusion: Surface components of P. gingivalis somehow have contact with host tissues and cells because of the outermost cell elements. Therefore, such bacterial components are potentially important in the occurrence of periodontal diseases.
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BFBNIB, CMK, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
The gram-negative anaerobic bacterium Porphyromonas gingivalis is a major causative agent of chronic periodontitis. Porphyromonas gingivalis strains have been classified into virulent and ...less-virulent strains by mouse subcutaneous soft tissue abscess model analysis. Here, we present the whole genome sequence of P. gingivalis ATCC 33277, which is classified as a less-virulent strain. We identified 2090 protein-coding sequences (CDSs), 4 RNA operons, and 53 tRNA genes in the ATCC 33277 genome. By genomic comparison with the virulent strain W83, we identified 461 ATCC 33277-specific and 415 W83-specific CDSs. Extensive genomic rearrangements were observed between the two strains: 175 regions in which genomic rearrangements have occurred were identified. Thirty-five of those genomic rearrangements were inversion or translocation and 140 were simple insertion, deletion, or replacement. Both strains contained large numbers of mobile elements, such as insertion sequences, miniature inverted-repeat transposable elements (MITEs), and conjugative transposons, which are frequently associated with genomic rearrangements. These findings indicate that the mobile genetic elements have been deeply involved in the extensive genome rearrangement of P. gingivalis and the occurrence of many of the strain-specific CDSs. We also describe here a very unique feature of MITE400, which we renamed MITEPgRS (MITE of
P. gingivalis with Repeating Sequences).
Summary
The periodontal pathogen Porphyromonas gingivalis generally expresses two distinct fimbriae, FimA and Mfa1, which play a role in biofilm formation. The fimA gene that encodes FimA fimbrilin ...is polymorphic, and polymerase chain reaction analysis has identified six genotypes called types I–V and Ib. We found recently that fimbriae exhibit antigenic heterogeneity among the genotypes. In the present study, we analysed the fimA DNA sequences of 84 strains of P. gingivalis and characterized the antigenicity of FimA fimbriae. Strains analysed here comprised 10, 16, 29, 13, 10 and 6 strains of types I, Ib, II, III, IV and V, respectively. DNA sequencing revealed that type Ib does not represent a single cluster and that type II sequences are remarkably diverse. In contrast, the fimA sequences of the other types were relatively homogeneous. Antigenicity was investigated using antisera elicited by pure FimA fimbriae of types I–V. Antigenicity correlated generally with the respective genotype. Type Ib strains were recognized by type I antisera. However, some strains showed cross‐reactivity, especially, many type II strains reacted with type III antisera. The levels of fimbrial expression were highly variable, and expression was positively correlated with ability of biofilm formation on a saliva‐coated plate. Further, two strains without FimA and Mfa1 fimbriae expressed fimbrial structures, suggesting that the strains produce other types of fimbriae.
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CMK, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Summary
In monocytes and macrophages, the interaction of Porphyromonas gingivalis with Toll‐like receptor 2 (TLR2) leads to the activation of a MyD88‐dependent antimicrobial pathway and a ...phosphatidylinositol‐3 kinase (PI3K) ‐dependent pro‐adhesive pathway, which activates the β2‐integrin complement receptor 3 (CR3). By means of its fimbriae, P. gingivalis binds CXC‐chemokine receptor 4 (CXCR4) and induces crosstalk with TLR2 that inhibits the MyD88‐dependent antimicrobial pathway. In this paper, we investigated the impact of the P. gingivalis‐CXCR4 interaction on the pro‐adhesive pathway. Using human monocytes, mouse macrophages, or receptor‐transfected cell lines, we showed that the binding of P. gingivalis fimbriae to CXCR4 induces CR3 activation via PI3K, albeit in a TLR2‐independent manner. An isogenic strain of P. gingivalis expressing mutant fimbriae that do not interact with CXCR4 failed to efficiently activate CR3, leading to enhanced susceptibility to killing in vivo compared with the wild‐type organism. This in vivo observation is consistent with previous findings that activated CR3 mediates safe entry of P. gingivalis into macrophages. Taken together with our previous work, these results indicate that the interaction of P. gingivalis with CXCR4 leads to inhibition of antimicrobial responses and enhancement of pro‐adhesive responses, thereby maximizing its adaptive fitness in the mammalian host.
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BFBNIB, CMK, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Summary
Periodontal diseases are semi‐ubiquitous and caused by chronic, plaque‐induced inflammation. The 55‐kDa immunodominant RagB outer membrane protein of Porphyromonas gingivalis, a keystone ...periodontal pathogen, has been proposed to facilitate nutrient transport. However, potential interactions between RagB and the innate response have not been examined. We determined that RagB exposure led to the differential and dose‐related expression of multiple genes encoding proinflammatory mediators interleukin‐1α (IL‐1α), IL‐1β, IL‐6, IL‐8 and CCL2; all P < 0.05 in primary human monocytes and to the secretion of tumor necrosis factor and IL‐8, but not interferon‐γ or IL‐12. RagB was shown to be a Toll‐like receptor 2 (TLR2) and TLR4 agonist that activated signal transducer and activator of transcription 4 and nuclear factor‐κB signaling, as determined by a combination of blocking antibodies, pharmaceutical inhibitors and gene silencing. In keeping, a ΔragB mutant similarly exhibited reduced inflammatory capacity, which was rescued by ragB complementation. These results suggest that RagB elicits a major pro‐inflammatory response in primary human monocytes and, therefore, could play an important role in the etiology of periodontitis and systemic sequelae.
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CMK, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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