Abstract/Details

Extracellular DnaK (Heat Shock Protein 70) of <i>Streptococcus mutans</i> is an endothelial modulin


2006 2006

Other formats: Order a copy

Abstract (summary)

DnaK (Heat Shock Protein [Hsp]70 and GroEL (Hsp60) are ubiquitous, highly conserved molecular chaperones. Bacterial HSPs have been shown to stimulate innate immunity, as well as to act as adhesins to mammalian cells. Mycobacterial Hsp70 binds to the human CD40 receptor. Streptococcus mutans is a causative agent of dental caries as well as infective endocarditis (IE). The S. mutans proteins that act as endothelial modulins and adhesins during IE remain to be completely defined. The objectives of this study were to localize extracellular S. mutans HSPs and to define functions of these proteins in interactions with endothelial cells. We identified DnaK and GroEL on the S. mutans and in culture medium through immunogold transmission electron microscopy, immunoblotting and immunofluorescence. Through sandwich enzyme-linked immunosorbent assays (ELISA) and cytokine antibody arrays, we demonstrated that recombinant S. mutans DnaK (SmDnaK), but not GroEL, can stimulate the release of proinflammatory cytokines/chemokines interleukin (IL)-6, IL-8 and growth-regulated oncogene (GRO) from human umbilical vein endothelial cells (HUVEC). This activity was enhanced upon endothelial pretreatment with interferon-gamma. Binding of SmDnaK to HUVEC was demonstrated through immunofluorescence microscopy, and increased binding was seen upon interferon-gamma pretreatment. Antibody blocking of DnaK on the surface of S. mutans decreased bacterial adherence to HUVEC, as evidenced by microscopy and flow cytometry. Expression of CD40 in HEK293 cells did not support increased adherence of SmDnaK. Additionally, SmDnaK failed to stimulate cytokine expression from CD40-expressing HEK293 cells. We conclude that S. mutans expresses DnaK and GroEL on its surface, as well as releases these HSPs into the culture medium. S. mutans DnaK, but not GroEL, can act as an endothelial modulin through recognition of an interferon-gamma-inducible receptor. The cellular binding of S. mutans DnaK is most likely CD40-independent. DnaK contributes to the adherence of S. mutans to endothelial cells. Our work suggests that DnaK is a modulin of the host immune response to S. mutans, and it might be utilized as a virulence factor during S. mutans attachment in the initial stages of IE.

Indexing (details)


Subject
Pathology;
Immunology
Classification
0571: Pathology
0982: Immunology
Identifier / keyword
Health and environmental sciences; DnaK; Endocarditis; Endothelial; Hsp70; Streptococcus mutans
Title
Extracellular DnaK (Heat Shock Protein 70) of <i>Streptococcus mutans</i> is an endothelial modulin
Author
Renschler, Janelle S.
Number of pages
148
Publication year
2006
Degree date
2006
School code
0093
Source
DAI-B 67/09, Dissertation Abstracts International
Place of publication
Ann Arbor
Country of publication
United States
ISBN
9780542879418
Advisor
Gregory, Richard L.
University/institution
Indiana University
University location
United States -- Indiana
Degree
Ph.D.
Source type
Dissertations & Theses
Language
English
Document type
Dissertation/Thesis
Dissertation/thesis number
3234477
ProQuest document ID
305337449
Copyright
Database copyright ProQuest LLC; ProQuest does not claim copyright in the individual underlying works.
Document URL
http://search.proquest.com/docview/305337449
Access the complete full text

You can get the full text of this document if it is part of your institution's ProQuest subscription.

Try one of the following:

  • Connect to ProQuest through your library network and search for the document from there.
  • Request the document from your library.
  • Go to the ProQuest login page and enter a ProQuest or My Research username / password.