Regulation of the Phosphorylation of Human Pharyngeal Cell Proteins by Group A Streptococcal Surface Dehydrogenase: Signal Transduction between Streptococci and Pharyngeal Cells

Abstract

Whether cell-to-cell communication results when group A streptococci interact with their target cells is unknown. Here, we report that upon contact with cultured human pharyngeal cells, both whole streptococci and purified streptococcal surface dehydrogenase (SDH) activate pharyngeal cell protein tyrosine kinase as well as protein kinase C, thus regulating the phosphorylation of cellular proteins. SDH, a major surface protein of group A streptococci, has both glyceraldehyde-3-phosphate dehydrogenase and ADP-ribosylating enzyme activities that may relate to early stages of streptococcal infection. Intact streptococci and purified SDH induce a similar protein phosphorylation pattern with the de novo tyrosine phosphorylation of a 17-kD protein found in the membrane/particulate fraction of the pharyngeal cells. However, this phosphorylation required the presence of cytosolic components. NH2-terminal amino acid sequence analysis identified the 17-kD protein as nuclear core histone H3. Both phosphotyrosine and phosphoserine-specific monoclonal antibodies reacted with the 17-kD protein by Western blot, suggesting that the binding of SDH to these pharyngeal cells elicits a novel signaling pathway that ultimately leads to activation of histone H3–specific kinases. Genistein-inhibitable phosphorylation of histone H3 indicates that tyrosine kinase plays a key role in this event. Treatment of pharyngeal cells with protein kinase inhibitors such as genistein and staurosporine significantly inhibited streptococcal invasion of pharyngeal cells. Therefore, these data indicated that streptococci/SDH-mediated phosphorylation plays a critical role in bacterial entry into the host cell. To identify the membrane receptor that elicits these signaling events, we found that SDH bound specifically to 30- and 32-kD membrane proteins in a direct ligand-binding assay. These findings clearly suggest that SDH plays an important role in cellular communication between streptococci and pharyngeal cells that may be important in host cell gene transcription, and hence in the pathogenesis of streptococcal infection.

Fluoride Exposure Attenuates Expression of Streptococcus pyogenes Virulence Factors

“…GAPDH expression was also decreased by fluoride. GAPDH expressed on the S. pyogenes cell surface acts as a virulence factor by binding fibronectin and stimulating signal transduction in host cells (23)(24)(25). Purified GAPDH stimulated serine and tyrosine kinase activity in host cells that was required for uptake of bacteria.…”

Role of Serine/Threonine Phosphatase (SP-STP) in Streptococcus pyogenes Physiology and Virulence

“…The signal was visualized using chemiluminescence substrate (SuperSignal West Pico, Pierce). The expression of SDH/ GAPDH in the total cell lysates was taken as loading control (7,21).…”

EsxA and EsxB are secreted by an ESAT-6-like system that is required for the pathogenesis ofStaphylococcus aureusinfections

“…Sec-independent translocation of virulence factors has been observed in group A streptococci and other Gram-positive species (3). The mechanism of substrate recognition and transport for these ''signal peptide less'' polypeptides has thus far not been revealed (4). In group A streptococci, secretion across the plasma membrane and injection of polypeptides into the cytosol of host cells uses a cytolysin-mediated transport mechanism (5), that functionally resembles type III secretion of Gram-negative bacteria (6).…”