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Role of Streptococcus intermedius DnaK chaperone system in stress tolerance and pathogenicity.

ABSTRACT: Streptococcus intermedius is a facultatively anaerobic, opportunistic pathogen that causes purulent infections and abscess formation. The DnaK chaperone system has been characterized in several pathogenic bacteria and seems to have important functions in stress resistance and pathogenicity. However, the role of DnaK in S. intermedius remains unclear. Therefore, we constructed a dnaK knockout mutant that exhibited slow growth, thermosensitivity, accumulation of GroEL in the cell, and reduced cytotoxicity to HepG2 cells. The level of secretion of a major pathogenic factor, intermedilysin, was not affected by dnaK mutation. We further examined the function and property of the S. intermedius DnaK chaperone system by using Escherichia coli ?dnaK and ?rpoH mutant strains. S. intermedius DnaK could not complement the thermosensitivity of E. coli ?dnaK mutant. However, the intact S. intermedius DnaK chaperone system could complement the thermosensitivity and acid sensitivity of E. coli ?dnaK mutant. The S. intermedius DnaK chaperone system could regulate the activity and stability of the heat shock transcription factor ?(32) in E. coli, although S. intermedius does not utilize ?(32) for heat shock transcription. The S. intermedius DnaK chaperone system was also able to efficiently eliminate the aggregated proteins from ?rpoH mutant cells. Overall, our data showed that the S. intermedius DnaK chaperone system has important functions in quality control of cellular proteins but has less participation in the modulation of expression of pathogenic factors.

SUBMITTER: Tomoyasu T

PROVIDER: S-EPMC3227844 | biostudies-literature | 2012 Jan

REPOSITORIES: biostudies-literature

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Role of Streptococcus intermedius DnaK chaperone system in stress tolerance and pathogenicity.

Tomoyasu Toshifumi T Tabata Atsushi A Imaki Hidenori H Tsuruno Keigo K Miyazaki Aya A Sonomoto Kenji K Whiley Robert Alan RA Nagamune Hideaki H

Cell stress & chaperones 20110806 1

Streptococcus intermedius is a facultatively anaerobic, opportunistic pathogen that causes purulent infections and abscess formation. The DnaK chaperone system has been characterized in several pathogenic bacteria and seems to have important functions in stress resistance and pathogenicity. However, the role of DnaK in S. intermedius remains unclear. Therefore, we constructed a dnaK knockout mutant that exhibited slow growth, thermosensitivity, accumulation of GroEL in the cell, and reduced cyto ...[more]

PMID: 21822788

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Project description:Protein folding is a crucial process in maintaining protein homeostasis, also known as proteostasis, in the cell. The requirement for the assistance of molecular chaperones in the appropriate folding of several proteins has already called into question the previously held view of spontaneous protein folding. These chaperones are highly ubiquitous cellular proteins, which not only help in mediating the proper folding of other nascent polypeptides but are also involved in refolding of the misfolded or the aggregated proteins. Hsp90 family proteins such as high-temperature protein G (HtpG) are abundant and ubiquitously expressed in both eukaryotic and prokaryotic cells. Although HtpG is known as an ATP-dependent chaperone protein in most organisms, function of this protein remains obscured in mycobacterial pathogens. Here, we aim to investigate significance of HtpG as a chaperone in the physiology of Mycobacterium tuberculosis. We report that M. tuberculosis HtpG (mHtpG) is a metal-dependent ATPase which exhibits chaperonin activity towards denatured proteins in coordination with the DnaK/DnaJ/GrpE chaperone system via direct association with DnaJ2. Increased expression of DnaJ1, DnaJ2, ClpX, and ClpC1 in a ΔhtpG mutant strain further suggests cooperativity of mHtpG with various chaperones and proteostasis machinery in M. tuberculosis. IMPORTANCE M. tuberculosis is exposed to variety of extracellular stressful conditions and has evolved mechanisms to endure and adapt to the adverse conditions for survival. mHtpG, despite being dispensable for M. tuberculosis growth under in vitro conditions, exhibits a strong and direct association with DnaJ2 cochaperone and assists the mycobacterial DnaK/DnaJ/GrpE (KJE) chaperone system. These findings suggest the potential role of mHtpG in stress management of the pathogen. Mycobacterial chaperones are responsible for folding of nascent protein as well as reactivation of protein aggregates. M. tuberculosis shows differential adaptive response subject to the availability of mHtpG. While its presence facilitates improved protein refolding via stimulation of the KJE chaperone activity, in the absence of mHtpG, M. tuberculosis enhances expression of DnaJ1/J2 cochaperones as well as Clp protease machinery for maintenance of proteostasis. Overall, this study provides a framework for future investigation to better decipher the mycobacterial proteostasis network in the light of stress adaptability and/or survival.

Dataset Information

Role of Streptococcus intermedius DnaK chaperone system in stress tolerance and pathogenicity.

Publications

Role of Streptococcus intermedius DnaK chaperone system in stress tolerance and pathogenicity.

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