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Streptococcal M6 protein binds to fucose-containing glycoproteins on cultured human epithelial cells
1Department of Microbiology, School of Medicine, State University of New York at Buffalo 14214.
Abstract:
M6 protein of Streptococcus pyogenes binds directly to HEp-2 cell surfaces and helps to mediate bacterial adhesion. Two epithelial cell receptors for M protein were identified as 97- and 205-kDa glycoproteins. Purified recombinant M6 protein (rM6) showed a dose-dependent and saturable binding to isolated HEp-2 membranes in an enzyme immunoassay. The HEp-2 cell receptors were selectively denatured by pretreatment of isolated membranes at 80 degrees C or with chymotrypsin; binding activity for rM6 was reduced 83 and 80%, respectively. Pretreatment of the HEp-2 membranes with neuraminidase-N-glycosidase, neuraminidase-O-glycosidase, alpha-L-fucosidase, or Ulex lectin caused 33, 42, 73, and 80% reduction of rM6 binding, respectively. Quantitative analysis of HEp-2 cells pretreated with alpha-L-fucosidase showed that the 97- and 205-kDa glycoproteins lost 70 and 62% of their abilities to bind M6 protein and that 33% of the HEp-2 cell's ability to bind whole streptococci was also lost. These results indicated that binding of M6 protein to HEp-2 cell surfaces is highly selective for certain fucose-containing oligosaccharides on these glycoproteins.
Insights
Streptococcus pyogenes M6 protein adheres to HEp-2 cells via fucose-containing glycoproteins. This bacterial adhesion mechanism involves specific oligosaccharide interactions on cell surface receptors.
Area of Science:
- Microbiology
- Cell Biology
- Biochemistry
Background:
- Streptococcus pyogenes M6 protein mediates bacterial adhesion to host cells.
- HEp-2 cells possess specific surface receptors for M6 protein.
Purpose of the Study:
- To identify and characterize the epithelial cell receptors for Streptococcus pyogenes M6 protein.
- To elucidate the molecular basis of M6 protein binding to HEp-2 cells.
Main Methods:
- Enzyme immunoassay using purified recombinant M6 protein (rM6) and isolated HEp-2 membranes.
- Selective denaturation of HEp-2 cell receptors using heat, chymotrypsin, and glycosidases.
- Quantitative analysis of M6 protein and streptococcal binding after enzymatic pretreatment.
Main Results:
- M6 protein binding to HEp-2 membranes was dose-dependent and saturable.
- Receptor denaturation with heat or chymotrypsin significantly reduced rM6 binding.
- Enzymatic pretreatment with alpha-L-fucosidase markedly reduced M6 protein binding to specific glycoproteins and overall bacterial adhesion.
Conclusions:
- HEp-2 cell surface receptors for M6 protein are 97- and 205-kDa glycoproteins.
- Binding is highly selective for fucose-containing oligosaccharides on these glycoproteins.
- This interaction is crucial for Streptococcus pyogenes adhesion to epithelial cells.