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How Pathogens Maintain Proteostasis During Infection.

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  • 1Department of Microbial Pathogenesis, Yale School of Medicine, New Haven, Connecticut, USA.

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Summary
This summary is machine-generated.

Bacterial Hsp70 chaperone DnaK binds to ribosomes and slows protein synthesis during magnesium starvation, a key stress during infection. This chaperone activity differs from its role in protein folding and varies across organisms.

Keywords:
DnaKHsp70J‐domain cochaperonePhoPRpoHmagnesiumprotein foldingprotein synthesistrigger factor

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Area of Science:

  • Microbiology
  • Molecular Biology
  • Cellular Biology

Background:

  • Molecular chaperones are essential for maintaining proteostasis by assisting protein folding.
  • Cells regulate protein synthesis and folding capacity to prevent toxic aggregate formation.
  • Cytoplasmic Mg2+ starvation is an infection-relevant stress impacting bacterial proteostasis.

Purpose of the Study:

  • To investigate the role of the Hsp70 chaperone DnaK in regulating protein synthesis during Mg2+ starvation in *Salmonella enterica* serovar Typhimurium.
  • To understand how DnaK's function under stress differs from its canonical roles and from other chaperones like trigger factor.
  • To explore the implications of differential chaperone expression in bacterial pathogenesis.

Main Methods:

  • Studied the interaction of DnaK with ribosomes in *S. typhimurium* under Mg2+-deficient conditions.
  • Assessed the effect of DnaK binding on protein synthesis rates.
  • Analyzed the expression patterns of DnaK, cochaperones (J-domain proteins, GrpE), and trigger factor under infection-relevant conditions regulated by PhoP.

Main Results:

  • DnaK binds to ribosomes and decreases protein synthesis during Mg2+ starvation in *S. typhimurium*.
  • This inhibitory effect on protein synthesis is independent of J-domain cochaperones and GrpE.
  • The virulence regulator PhoP upregulates DnaK but not other chaperones/cochaperones during infection-relevant stress.
  • Hsp70 chaperone activity at the ribosome differs between bacteria (inhibition) and eukaryotes (promotion) and varies with growth conditions.

Conclusions:

  • DnaK plays a distinct role in regulating protein synthesis, separate from its folding functions, during Mg2+ starvation.
  • Differential expression of chaperones and cochaperones, orchestrated by PhoP, contributes to *S. typhimurium* pathogenesis.
  • Hsp70 chaperone activity at the ribosome is context-dependent, varying with cellular conditions and organismal type, highlighting functional divergence.