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Mechanism to control the cell lysis and the cell survival strategy in stationary phase under heat stress.

Noor R - Springerplus (2015)

Bottom Line: At the elevated temperatures, σ(E) also serves as the transcription factor for σ(H) (the main heat shock sigma factor, encoded by rpoH), which is involved in the expression of several genes whose products deal with the cytoplasmic unfolded proteins.Besides, oxidative stress in form of the reactive oxygen species (ROS) that accumulate due to heat stress, has been found to give rise to viable but non-culturable (VBNC) cells at the early stationary phase, which is in turn lysed by the σ(E)-dependent process.Such lysis of the defective cells may generate nutrients for the remaining population to survive with the capacity of formation of colony forming units (CFUs). σ(H) is also known to regulate the transcription of the major heat shock proteins (HSPs) required for heat shock response (HSR) resulting in cellular survival.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka, 1217 Bangladesh.

ABSTRACT
An array of stress signals triggering the bacterial cellular stress response is well known in Escherichia coli and other bacteria. Heat stress is usually sensed through the misfolded outer membrane porin (OMP) precursors in the periplasm, resulting in the activation of σ(E) (encoded by rpoE), which binds to RNA polymerase to start the transcription of genes required for responding against the heat stress signal. At the elevated temperatures, σ(E) also serves as the transcription factor for σ(H) (the main heat shock sigma factor, encoded by rpoH), which is involved in the expression of several genes whose products deal with the cytoplasmic unfolded proteins. Besides, oxidative stress in form of the reactive oxygen species (ROS) that accumulate due to heat stress, has been found to give rise to viable but non-culturable (VBNC) cells at the early stationary phase, which is in turn lysed by the σ(E)-dependent process. Such lysis of the defective cells may generate nutrients for the remaining population to survive with the capacity of formation of colony forming units (CFUs). σ(H) is also known to regulate the transcription of the major heat shock proteins (HSPs) required for heat shock response (HSR) resulting in cellular survival. Present review concentrated on the cellular survival against heat stress employing the harmonized impact of σ(E) and σ(H) regulons and the HSPs as well as their inter connectivity towards the maintenance of cellular survival.

No MeSH data available.


Related in: MedlinePlus

Function of DnaK in association with σH in response to heat stress. Unfolded proteins caused by heat stress are sensed by the heat shock chaperon DnaK which keeps attached to σH. Upon protein unfolding, DnaK releases σH which in turn binds to RNA polymerase. The σH—RNA polymerase complex transcribes genes whose products are essential to respond against the cytoplasmic stress. This is to be mentioned that the transcription of the σH (encoded by the rpoH gene) is induced at elevated temperature via the action of σE (encoded by the rpoE gene)
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Fig4: Function of DnaK in association with σH in response to heat stress. Unfolded proteins caused by heat stress are sensed by the heat shock chaperon DnaK which keeps attached to σH. Upon protein unfolding, DnaK releases σH which in turn binds to RNA polymerase. The σH—RNA polymerase complex transcribes genes whose products are essential to respond against the cytoplasmic stress. This is to be mentioned that the transcription of the σH (encoded by the rpoH gene) is induced at elevated temperature via the action of σE (encoded by the rpoE gene)

Mentions: One of envelope-stress responses in E. coli is performed by a regulated intra-membrane proteolysis system (Barchinger and Ades 2013; Cezairliyan and Sauer 2006) that includes the σE transcription factor, the RseA and RseB regulators, and the DegS and RseP (YaeL) proteases (Noor et al. 2009a; Cezairliyan and Sauer 2006; Kabir and Yamada 2005; Ruiz and Silhavy 2005; Ades 2004; Alba and Gross 2004; Ehrmann and Clausen 2004; Duguay and Silhavy 2004; Campbell et al. 2003). The association of σE with RNA polymerase is normally inhibited by formation of a tight complex between σE and RseA (Fig. 3). At high temperature or under other conditions that result in protein misfolding, a series of proteolytic cleavages destroy RseA and liberate σE in free form (Alba et al. 2002). DegS, which is anchored into the inner membrane by an N-terminal transmembrane segment, is activated when the PDZ domain of DegS binds to a misfolded OMP precursor (Kim et al. 2007; Ades et al. 1999). The periplasmic C-terminus of RseA is then cleaved by the activated DegS (Wilken et al. 2004), followed by the sequential digestion of the N terminus of RseA by RseP (YaeL), a membrane metalloprotease, to release the N terminus of RseA/σE complex into the cytosol (Kanehara et al. 2002). The σE can be released completely from RseA, and its activity as a sigma factor is restored when the RseA fragment is removed by ClpXP protease (Kim et al. 2007; Flynn et al. 2004). The models shown in Figs. 3, 4 specifically demonstrated that the σE regulon genes deal with extracytoplasmic stress, whereas the σH regulon genes deal with the cytoplasmic stress (Kabir and Yamada 2005).Fig. 3


Mechanism to control the cell lysis and the cell survival strategy in stationary phase under heat stress.

Noor R - Springerplus (2015)

Function of DnaK in association with σH in response to heat stress. Unfolded proteins caused by heat stress are sensed by the heat shock chaperon DnaK which keeps attached to σH. Upon protein unfolding, DnaK releases σH which in turn binds to RNA polymerase. The σH—RNA polymerase complex transcribes genes whose products are essential to respond against the cytoplasmic stress. This is to be mentioned that the transcription of the σH (encoded by the rpoH gene) is induced at elevated temperature via the action of σE (encoded by the rpoE gene)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4627973&req=5

Fig4: Function of DnaK in association with σH in response to heat stress. Unfolded proteins caused by heat stress are sensed by the heat shock chaperon DnaK which keeps attached to σH. Upon protein unfolding, DnaK releases σH which in turn binds to RNA polymerase. The σH—RNA polymerase complex transcribes genes whose products are essential to respond against the cytoplasmic stress. This is to be mentioned that the transcription of the σH (encoded by the rpoH gene) is induced at elevated temperature via the action of σE (encoded by the rpoE gene)
Mentions: One of envelope-stress responses in E. coli is performed by a regulated intra-membrane proteolysis system (Barchinger and Ades 2013; Cezairliyan and Sauer 2006) that includes the σE transcription factor, the RseA and RseB regulators, and the DegS and RseP (YaeL) proteases (Noor et al. 2009a; Cezairliyan and Sauer 2006; Kabir and Yamada 2005; Ruiz and Silhavy 2005; Ades 2004; Alba and Gross 2004; Ehrmann and Clausen 2004; Duguay and Silhavy 2004; Campbell et al. 2003). The association of σE with RNA polymerase is normally inhibited by formation of a tight complex between σE and RseA (Fig. 3). At high temperature or under other conditions that result in protein misfolding, a series of proteolytic cleavages destroy RseA and liberate σE in free form (Alba et al. 2002). DegS, which is anchored into the inner membrane by an N-terminal transmembrane segment, is activated when the PDZ domain of DegS binds to a misfolded OMP precursor (Kim et al. 2007; Ades et al. 1999). The periplasmic C-terminus of RseA is then cleaved by the activated DegS (Wilken et al. 2004), followed by the sequential digestion of the N terminus of RseA by RseP (YaeL), a membrane metalloprotease, to release the N terminus of RseA/σE complex into the cytosol (Kanehara et al. 2002). The σE can be released completely from RseA, and its activity as a sigma factor is restored when the RseA fragment is removed by ClpXP protease (Kim et al. 2007; Flynn et al. 2004). The models shown in Figs. 3, 4 specifically demonstrated that the σE regulon genes deal with extracytoplasmic stress, whereas the σH regulon genes deal with the cytoplasmic stress (Kabir and Yamada 2005).Fig. 3

Bottom Line: At the elevated temperatures, σ(E) also serves as the transcription factor for σ(H) (the main heat shock sigma factor, encoded by rpoH), which is involved in the expression of several genes whose products deal with the cytoplasmic unfolded proteins.Besides, oxidative stress in form of the reactive oxygen species (ROS) that accumulate due to heat stress, has been found to give rise to viable but non-culturable (VBNC) cells at the early stationary phase, which is in turn lysed by the σ(E)-dependent process.Such lysis of the defective cells may generate nutrients for the remaining population to survive with the capacity of formation of colony forming units (CFUs). σ(H) is also known to regulate the transcription of the major heat shock proteins (HSPs) required for heat shock response (HSR) resulting in cellular survival.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, Stamford University Bangladesh, 51 Siddeswari Road, Dhaka, 1217 Bangladesh.

ABSTRACT
An array of stress signals triggering the bacterial cellular stress response is well known in Escherichia coli and other bacteria. Heat stress is usually sensed through the misfolded outer membrane porin (OMP) precursors in the periplasm, resulting in the activation of σ(E) (encoded by rpoE), which binds to RNA polymerase to start the transcription of genes required for responding against the heat stress signal. At the elevated temperatures, σ(E) also serves as the transcription factor for σ(H) (the main heat shock sigma factor, encoded by rpoH), which is involved in the expression of several genes whose products deal with the cytoplasmic unfolded proteins. Besides, oxidative stress in form of the reactive oxygen species (ROS) that accumulate due to heat stress, has been found to give rise to viable but non-culturable (VBNC) cells at the early stationary phase, which is in turn lysed by the σ(E)-dependent process. Such lysis of the defective cells may generate nutrients for the remaining population to survive with the capacity of formation of colony forming units (CFUs). σ(H) is also known to regulate the transcription of the major heat shock proteins (HSPs) required for heat shock response (HSR) resulting in cellular survival. Present review concentrated on the cellular survival against heat stress employing the harmonized impact of σ(E) and σ(H) regulons and the HSPs as well as their inter connectivity towards the maintenance of cellular survival.

No MeSH data available.


Related in: MedlinePlus