Bacteria use energy dependent proteases to respond to stressful conditions. These proteases serve a dual role: destroying aberrant, potentially toxic, damaged proteins and generating stress responsive signals through degradation of regulatory factors. Cells often arrest replication in response to stress, but how regulated proteolysis contributes to cell cycle arrest in bacteria is currently poorly understood. This proposal addresses how stress related proteases target replication factors using a combination of biochemical, genetic and proteomic approaches, specifically focusing on proteases and replication factors from the model bacteria Caulobacter crescentus.
Aims 1 and 2 determine how misfolded proteins generated during proteotoxic stress directly stimulate the Lon protease to destroy the replication initiator DnaA and cause growth arrest during stress.
Aims 3 and 4 focus on how partial processing of the clamp loader subunit DnaX by the ClpXP protease is critical for replication stress tolerance during DNA damage. Because these proteases and replication factors are highly conserved throughout all bacteria, these results will impact our general understanding of replication, proteolysis, and stress tolerance. The critical role of these proteases in bacterial virulence and pathogenicity, together with the universal requirement for these proteases in bacterial stress responses, suggests that they are excellent targets for development of new antibiotic strategies that are of immediate human health need.

Public Health Relevance

Energy dependent proteases are found in all bacteria and necessary for virulence in many human pathogens. When bacteria are stressed, such as when they invade a host or encounter antibiotics, a crucial response is to stop growing in order to repair damages before they invest limited resources in growth. By determining how these changes rely on proteolytic degradation of essential replication factors, this work will reveal new path- ways that could be targeted to block bacterial virulence or to prevent bacteria from resisting the stresses produced by currently used antibiotics.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Prokaryotic Cell and Molecular Biology Study Section (PCMB)
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Reddy, Michael K
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University of Massachusetts Amherst
Schools of Arts and Sciences
United States
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Mahmoud, Samar A; Chien, Peter (2018) Regulated Proteolysis in Bacteria. Annu Rev Biochem 87:677-696
Liu, Jing; Zeinert, Rilee; Francis, Laura et al. (2018) Lon recognition of the replication initiator DnaA requires a bipartite degron. Mol Microbiol :
Joshi, Kamal Kishore; Battle, Christine M; Chien, Peter (2018) Polar Localization Hub Protein PopZ Restrains Adaptor-Dependent ClpXP Proteolysis in Caulobacter crescentus. J Bacteriol 200:
Joshi, Kamal Kishore; Sutherland, Madeleine; Chien, Peter (2017) Cargo engagement protects protease adaptors from degradation in a substrate-specific manner. J Biol Chem 292:10973-10982
Vass, Robert H; Nascembeni, Jacob; Chien, Peter (2017) The Essential Role of ClpXP in Caulobacter crescentus Requires Species Constrained Substrate Specificity. Front Mol Biosci 4:28
Kuhlmann, Nathan J; Chien, Peter (2017) Selective adaptor dependent protein degradation in bacteria. Curr Opin Microbiol 36:118-127
Joshi, Kamal Kishore; Chien, Peter (2016) Regulated Proteolysis in Bacteria: Caulobacter. Annu Rev Genet 50:423-445
Glynn, Steven E; Chien, Peter (2016) Sending protein aggregates into a downward spiral. Nat Struct Mol Biol 23:769-70
Vass, Robert H; Zeinert, Rilee D; Chien, Peter (2016) Protease regulation and capacity during Caulobacter growth. Curr Opin Microbiol 34:75-81
Vass, Robert H; Chien, Peter (2016) Two ways to skin a cat: acyldepsipeptides antibiotics can kill bacteria through activation or inhibition of ClpP activity. Mol Microbiol 101:183-5

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