Role of HtrA in Surface Protein Expression and Biofilm Formation by Streptococcus mutans

Abstract

The HtrA surface protease in gram-positive bacteria is involved in the processing and maturation of extracellular proteins and degradation of abnormal or misfolded proteins. Inactivation of htrA has been shown to affect the tolerance to thermal and environmental stress and to reduce virulence. We found that inactivation of Streptococcus mutans htrA by gene-replacement also resulted in a reduced ability to withstand exposure to low and high temperatures, low pH, and oxidative and DNA damaging agents. The htrA mutation affected surface expression of several extracellular proteins including glucan-binding protein B (GbpB), glucosyltransferases, and fructosyltransferase. In addition, htrA mutation also altered the surface expression of enolase and glyceraldehyde-3-phosphate dehydrogenease, two glycolytic enzymes that are known to be present on the streptococcal cell surface. As expected, microscopic analysis of in vitro grown biofilm structure revealed that the htrA deficient biofilms adopted a much more granular patchy appearance, rather than the relatively smooth confluent layer normally seen in the wild type. These results suggest that HtrA plays an important role in the biogenesis of extracellular proteins including surface associated glycolytic enzymes and in biofilm formation of S. mutans.

An Extracelluar Protease, SepM, Generates Functional Competence-Stimulating Peptide in Streptococcus mutans UA159

“…A Kan-resistant cassette with flanking modified loxP sites was amplified from pUC4 ⍀Kan (39) using the primers lox71-Km-F and lox66-Km-R (for all primers, see Table 2) and cloned into EcoRV-digested pIB-D48 to generate pIB-D50. Plasmid pIB-D50 was lin- pIB104::Em earized with EcoRI and transformed into S. mutans UA159 as previously described (9). The transformants were selected on THY plates containing Kan; one such transformant was selected and named IBS-D20.…”

YidC1 and YidC2 are functionally distinct proteins involved in protein secretion, biofilm formation and cariogenicity of Streptococcus mutans

“…An investigation by Biswas & Biswas (2005) found that deletion of the HtrA extracellular protease/chaperone resulted in increased levels of extracellular GAPDH in culture media. It is not known how GAPDH or other cytoplasmic proteins are transported, as they do not contain signal peptides.…”

“…A study by Biswas & Biswas (2005) investigated the effects of deletion of the HtrA extracellular protease/chaperone and found that levels of extracellular GAPDH in culture media increased when HtrA was absent. Extracellular GAPDH activity was increased in both DyidC1 and DyidC2 mutants compared with the parental strain, with a greater effect seen with DyidC2.…”

Thermosensing to Adjust Bacterial Virulence in a Fluctuating Environment

“…In consistency, htrA mutants of many pathogens show attenuated virulence [128][129][130][131]. Intriguingly, a novel role has recently been identified for HtrA of Helicobacter pylori and Campylobacter jejuni: HtrA was found to be secreted during infection and acts as a virulence factor that specifically cleaves the extracellular domain of E-cadherin on infected gastric epithelial cells [132][133][134][135].…”