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A host-derived pentapeptide enhancing host-bacteria commensalisms and communication
Umeå University, Faculty of Medicine, Department of Odontology, Cariology.
Umeå University, Faculty of Medicine, Department of Odontology, Cariology.
Umeå University, Faculty of Medicine, Department of Odontology, Cariology.
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2006 (English)In: Infection and Immunity, ISSN 0019-9567, E-ISSN 1098-5522, Vol. 74, no 11, 6293-6299 p.Article in journal (Refereed) Published
Abstract [en]

Salivary proline-rich proteins (PRPs) attach commensal Actinomyces and Streptococcus species to teeth. Here, gel filtration, mass spectrometry and Edman degradation were applied to show the release of a pentapeptide, RGRPQ, from PRP-1 upon proteolysis by Streptococcus gordond. Moreover, synthetic RGRPQ and derivatives were used to investigate associated innate properties and responsible motifs. The RGRPQ peptide increased 2.5-fold the growth rate of S. gordonii via a Q-dependent sequence motif and selectively stimulated oral colonization of this organism in a rat model in vivo. In contrast, the growth of Streptococcus mutans, implicated in caries, was not affected. While the entire RGRPQ sequence was required to block sucrose-induced pH-decrease by S. gordonii and S. mutans, the N-terminal Arg residue mediated the pH increase (i.e., ammonia production) by S. gordonii alone (which exhibits Arg catabolism to ammonia). Strains of commensal viridans streptococci exhibited PR-P degradation and Arg catabolism, whereas cariogenic species did not. The RGRPQ peptide mediated via a differential Q-dependent sequence motif, adhesion inhibition, and desorption of PRP-1-binding strains of A. naeslundii genospecies 2 (5 of 10 strains) but not of S. gordonii (n = 5). The inhibitable A. naeslundii strains alone displayed the same binding profile as S. gordond to hybrid peptides terminating in RGRPQ or GQSPQ, derived from the middle or C-terminal segments of PRP-1. The present findings indicate the presence of a host-bacterium interaction in which a host peptide released by bacterial proteolysis affects key properties in biofilm formation.

Place, publisher, year, edition, pages
Washington: American society for microbiology , 2006. Vol. 74, no 11, 6293-6299 p.
Keyword [en]
proline-rich proteins, candida albicans, oral bacteria, salivary agglutinin, apatitic surfaces, innate immunity, Dental caries, Gordonii, commensal, statherin
National Category
Immunology in the medical area Infectious Medicine Dentistry
URN: urn:nbn:se:umu:diva-5291DOI: 10.1128/IAI.00068-06ISI: 000241600500031OAI: diva2:144765
Available from: 2006-09-08 Created: 2006-09-08 Last updated: 2016-08-26Bibliographically approved
In thesis
1. Adhesion-related interactions of Actinomyces and Streptococcus biofilm bacteria
Open this publication in new window or tab >>Adhesion-related interactions of Actinomyces and Streptococcus biofilm bacteria
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Adhesion of bacteria is a key event in biofilm formation and is mediated by bacterial adhesins recognising host or bacterial partner receptors. In oral biofilm formation, primary Actinomyces and Streptococcus colonizers adhere to salivary pellicle proteins such as proline-rich proteins (PRPs) as well as to mucosal surfaces. Subsequently, Actinomyces and Streptococcus strains and other bacteria, such as Veillonella, Fusobacterium and Porphyromonas, adhere to each other. The nature of this community is highly important for the health or disease status, although specific pathogenic species may also have been implicated.

The aim of this thesis was to study key players in early oral colonisation, Actinomyces and Streptococcus species, and more specifically the nature of their adhesins and ligands. A further aim was to study the function of the salivary PRP proteins and an innate peptide derived thereof on bacterial adhesion, proliferation and regulation of pH, i.e. key factors in biofilm formation.

In paper I and II, adhesion, proliferation and pH affecting features of the RGRPQ (arginine-glycine-arginine-proline-glutamine) peptide, derived from PRP-1, were demonstrated. By use of an alanine-scan (I), motifs for adhesion inhibition and desorption of Actinomyces naeslundii, and proliferation stimulation, ammonia production and inhibition of sucrose induced pH drop by Streptococcus gordonii were indicated. The RGRPQ peptide also stimulated S. gordonii colonisation in vivo. In paper II, a more sophisticated quantitative structure-activity relationship (QSAR) study, using statistical molecular design (SMD) and multivariate modelling (partial least squares projections to latent structures, PLS), further narrowed down the RGRPQ peptide motifs. The R and Q amino acids were crucial for activity. For proliferation a hydrophobic and large size third position amino acid was crucial, while adhesion inhibition and desorption needed a small hydrophilic second position amino acid. All functions depended on a low polarity hydrophobic fourth position. Accordingly, activities could be optimized separately, with decreased function in the others.

In paper III and IV, focus was on the bacterial adhesins and their binding epitopes. The genes for FimA major subunit proteins of type-2 fimbriae were sequenced from A. naeslundii genospecies 1 and 2 and Actinomyces odontolyticus, each with unique carbohydrate binding specificities (III). Three major subtypes of FimA proteins were found that correlated with binding specificity, including a novel fimA gene in A. odontolyticus. All subtypes contained a pilin, LPXTG and E box motif. In paper IV, multiple PRP binding patterns for Actinomyces and Streptococcus strains were mapped using a hybrid peptide construct. The two most deviating binding groups deviated in type-1 fimbriae mediated binding to milk and saliva protein ligands.

In conclusion, differences in bacterial adhesins and their ability to utilise salivary proteins may render bacteria tropism for different niches. Peptides derived from protein receptors, such as RGRPQ, may be important modulators of biofilm formation, giving commensal bacteria a competitive edge in the bacterial community.

Place, publisher, year, edition, pages
Umeå: Odontologi, 2006. 45 p.
Umeå University odontological dissertations, ISSN 0345-7532 ; 92
biofilm, Actinomyces, Streptococcus, adhesion
National Category
urn:nbn:se:umu:diva-860 (URN)91-7264-111-8 (ISBN)
Public defence
2006-09-29, Sal B, Tandläkarhögskolan 9 tr, 90187 Umeå, Umeå, 13:00 (English)
Available from: 2006-09-08 Created: 2006-09-08 Last updated: 2009-10-01Bibliographically approved

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