title: Functions of cell surface-anchored antigen I/II family and Hsa polypeptides in interactions of Streptococcus gordonii with host receptors.
abstract: Streptococcus gordonii colonizes multiple sites within the human oral cavity. This colonization depends upon the initial interactions of streptococcal adhesins with host receptors. The adhesins that bind salivary agglutinin glycoprotein (gp340) and human cell surface receptors include the antigen I/II (AgI/II) family polypeptides SspA and SspB and a sialic acid-binding surface protein designated Hsa or GspB. In this study we determined the relative functions of the AgI/II polypeptides and Hsa in interactions of S. gordonii DL1 (Challis) with host receptors. For an isogenic mutant with the sspA and sspB genes deleted the levels of adhesion to surface-immobilized gp340 were reduced 40%, while deletion of the hsa gene alone resulted in >80% inhibition of bacterial cell adhesion to gp340. Adhesion of S. gordonii DL1 cells to gp340 was sialidase sensitive, verifying that Hsa has a major role in mediating sialic acid-specific adhesion to gp340. Conversely, aggregation of S. gordonii cells by fluid-phase gp340 was not affected by deletion of hsa but was eliminated by deletion of the sspA and sspB genes. Deletion of the AgI/II polypeptide genes had no measurable effect on hsa mRNA levels or Hsa surface protein expression, and deletion of hsa did not affect AgI/II polypeptide expression. Further analysis of mutant phenotypes showed that the Hsa and AgI/II proteins mediated adhesion of S. gordonii DL1 to human HEp-2 epithelial cells. Hsa was also a principal streptococcal cell surface component promoting adhesion of human platelets to immobilized streptococci, but Hsa and AgI/II polypeptides acted in concert in mediating streptococcal cell-platelet aggregation. The results suggest that Hsa directs primary adhesion events for S. gordonii DL1 (Challis) with immobilized gp340, epithelial cells, and platelets. AgI/II polypeptides direct gp340-mediated aggregation, facilitate multimodal interactions necessary for platelet aggregation, and modulate S. gordonii-host engagements into biologically productive phenomena.
authors.affiliation: Department of Oral and Dental Science, University of Bristol, UK.
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Jakubovics
authors.forename: Steven W
authors.initials: SW
authors.lastname: Kerrigan
authors.forename: Angela H
authors.initials: AH
authors.lastname: Nobbs
authors.forename: Nicklas
authors.initials: N
authors.lastname: Strömberg
authors.forename: Craig J
authors.initials: CJ
authors.lastname: van Dolleweerd
authors.forename: Dermot M
authors.initials: DM
authors.lastname: Cox
authors.forename: Charles G
authors.initials: CG
authors.lastname: Kelly
authors.forename: Howard F
authors.initials: HF
authors.lastname: Jenkinson
mesh_terms: D018829:Adhesins, Bacterial / Q000235:genetics / Q000378:metabolism*; D000942:Antigens, Bacterial / Q000235:genetics / Q000378:metabolism; D001422:Bacterial Adhesion / Q000235:genetics / Q000502:physiology; D001792:Blood Platelets / Q000378:metabolism / Q000382:microbiology; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D004847:Epithelial Cells / Q000378:metabolism / Q000382:microbiology; D017353:Gene Deletion; D006389:Hemagglutinins, Viral; D006801:Humans; D009154:Mutation; D010455:Peptides / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013290:Streptococcal Infections / Q000276:immunology / Q000378:metabolism; D013291:Streptococcus / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D025521:Tumor Suppressor Proteins
chemical_list: D018829:Adhesins, Bacterial; D000942:Antigens, Bacterial; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; C108174:DMBT1 protein, human; D004268:DNA-Binding Proteins; D006389:Hemagglutinins, Viral; D010455:Peptides; D011956:Receptors, Cell Surface; C082314:SspA protein, bacteria; D025521:Tumor Suppressor Proteins; C450840:hsa protein, Streptococcus gordonii; C068465:salivary agglutinin receptor, Streptocococcus