Effect of heat shock and mutations in ClpL and ClpP on virulence gene expression in Streptococcus pneumoniae.
Spread of Streptococcus pneumoniae from the nasopharynx to other host tissues would require the organism to adapt to a variety of environmental conditions. Since heat shock proteins are induced by environmental stresses, we investigated the effect of heat shock on ClpL and ClpP synthesis and the effect of clpL and clpP mutations on the expression of key pneumococcal virulence genes. Pulse labeling with [(35)S]methionine and chase experiments as well as immunoblot analysis demonstrated that ClpL, DnaK, and GroEL were stable. Purified recombinant ClpL refolded urea-denatured rhodanese in a dose-dependent manner, demonstrating ClpL's chaperone activity. Although growth of the clpL mutant was not affected at 30 or 37 degrees C, growth of the clpP mutant was severely affected at these temperatures. However, both clpL and clpP mutants were sensitive to 43 degrees C. Although it was further induced by heat shock, the level of expression of ClpL in the clpP mutant was high at 30 degrees C, suggesting that ClpP represses expression of ClpL. Furthermore, the clpP mutation significantly attenuated the virulence of S. pneumoniae in a murine intraperitoneal infection model, whereas the clpL mutation did not. Interestingly, immunoblot and real-time reverse transcription-PCR analysis demonstrated that pneumolysin and pneumococcal surface antigen A were induced by heat shock in wild-type S. pneumoniae. Other virulence genes were also affected by heat shock and clpL and clpP mutations. Virulence gene expression seems to be modulated not only by heat shock but also by the ClpL and ClpP proteases.
Kwon
Hyog-Young
HY
College of Pharmacy, Sungkyunkwan University, Suwon 440-746, Korea.
Kim
Seung-Whan
SW
Choi
Moo-Hyun
MH
Ogunniyi
A David
AD
Paton
James C
JC
Park
Sin-Hee
SH
Pyo
Suhk-Neung
SN
Rhee
Dong-Kwon
DK
D000251:Adenosine Triphosphatases / Q000502:physiology*; D000818:Animals; D049071:Endopeptidase Clp; D006360:Heat-Shock Proteins / Q000502:physiology*; D006358:Hot Temperature; D051379:Mice; D008807:Mice, Inbred BALB C; D018832:Molecular Chaperones / Q000502:physiology; D009154:Mutation; D010641:Phenotype; D012697:Serine Endopeptidases / Q000502:physiology*; D013296:Streptococcus pneumoniae / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*; D014774:Virulence / Q000235:genetics
D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D012697:Serine Endopeptidases; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases