TheMycobacterium tuberculosisPup-proteasome system regulates nitrate metabolism through an essential protein quality control pathway

The human pathogenMycobacterium tuberculosisencodes a proteasome that carries out regulated degradation of bacterial proteins. It has been proposed that the proteasome contributes to nitrogen metabolism inM. tuberculosis, although this hypothesis had not been tested. Upon assessingM. tuberculosisgrowth in several nitrogen sources, we found that a mutant strain lacking theMycobacteriumproteasomal activator Mpa was unable to use nitrate as a sole nitrogen source due to a specific failure in the pathway of nitrate reduction to ammonium. We found that the robust activity of the nitrite reductase complex NirBD depended on expression of thegroEL/groESchaperonin genes, which are regulated by the repressor HrcA. We identified HrcA as a likely proteasome substrate, and propose that the degradation of HrcA is required for the full expression of chaperonin genes. Furthermore, our data suggest that degradation of HrcA, along with numerous other proteasome substrates, is enhanced during growth in nitrate to facilitate the derepression of the chaperonin genes. Importantly, growth in nitrate is an example of a specific condition that reduces the steady-state levels of numerous proteasome substrates inM. tuberculosis.

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TheMycobacterium tuberculosisPup-proteasome system regulates nitrate metabolism through an essential protein quality control system

10.1101/470989 ◽

2018 ◽

Cited By ~ 1

Author(s):

Samuel H. Becker ◽

Jordan B. Jastrab ◽

Avantika Dhabaria ◽

Catherine T. Chaton ◽

Jeffrey S. Rush ◽

...

Keyword(s):

Nitrogen Source ◽

Protein Quality ◽

Specific Growth ◽

Nitrogen Sources ◽

Human Pathogen ◽

Bacterial Physiology ◽

Bacterial Proteins ◽

Nitrate Metabolism ◽

Steady State Levels ◽

Protein Quality Control System

ABSTRACTThe human pathogenMycobacterium tuberculosis(M. tuberculosis) encodes a proteasome that carries out regulated degradation of bacterial proteins. It has been proposed that the proteasome contributes to nitrogen metabolism inM. tuberculosis, although this hypothesis had not been tested. Upon assessingM. tuberculosisgrowth in several nitrogen sources, we found that a mutant strain lacking theMycobacteriumproteasomal activator Mpa was unable to use nitrate as a sole nitrogen source due to a specific failure in the pathway of nitrate reduction to ammonium. We found that the robust activity by the nitrite reductase complex NirBD depended on expression of thegroEL/groESchaperonin genes, which are regulated by the repressor HrcA. We identified HrcA as a likely proteasome substrate, and propose that the degradation of HrcA is required for the full expression of chaperonin genes. Furthermore, our data suggest that degradation of HrcA, along with numerous other proteasome substrates, is enhanced during growth in nitrate to facilitate the de-repression of the chaperonin genes. Importantly, growth in nitrate is the first example of a specific condition that reduces the steady-state levels of numerous proteasome substrates inM. tuberculosis.SIGNIFICANCE STATEMENTThe proteasome is required for the full virulence ofM. tuberculosis. However, the extent of its role as a regulator of bacterial physiology remains unclear. In this work, we demonstrate a novel function of the proteasome system in maintaining the expression of essential chaperonin genes. This activity by the proteasome is required forM. tuberculosisto use nitrate as a nitrogen source. Furthermore, we identified a specific growth condition that robustly decreases the abundance of pupylated proteins. This observation strongly suggests the presence of a yet-to-be-determined mechanism of control over the Pup-proteasome system inM. tuberculosisthat is induced in nitrate.

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USP5 enhances SGTA mediated protein quality control

10.1101/2021.09.13.460017 ◽

2021 ◽

Author(s):

Yvonne Nyathi ◽

Jake Alfie Hill

Keyword(s):

Quality Control ◽

Steady State ◽

Type Ii Diabetes ◽

Protein Quality ◽

Proteasomal Degradation ◽

Aggregate Formation ◽

Deubiquitinating Enzymes ◽

Physiological Processes ◽

Hydrophobic Amino Acids ◽

Steady State Levels

Mislocalised membrane proteins (MLPs) present a risk to the cell due to exposed hydrophobic amino acids which cause MLPs to aggregate. Previous studies identified SGTA as a key component of the machinery that regulates the quality control of MLPs. Overexpression of SGTA promotes deubiqutination of MLPs resulting in their accumulation in cytosolic inclusions, suggesting SGTA acts in collaboration with deubiquitinating enzymes (DUBs) to exert these effects. However, the DUBs that play a role in this process have not been identified. In this study we have identified the ubiquitin specific peptidase 5 (USP5) as a DUB important in regulating the quality control of MLPs. We show that USP5 is in complex with SGTA, and this association is increased in the presence of an MLP. Overexpression of SGTA results in an increase in steady-state levels of MLPs suggesting a delay in proteasomal degradation of substrates. However, our results show that this effect is strongly dependent on the presence of USP5. We find that in the absence of USP5, the ability of SGTA to increase the steady state levels of MLPs is compromised. Moreover, knockdown of USP5 results in a reduction in the steady state levels of MLPs, while overexpression of USP5 increases the steady state levels. Our findings suggest that the interaction of SGTA with USP5 enables specific MLPs to escape proteasomal degradation allowing selective modulation of MLP quality control. These findings progress our understanding of aggregate formation, a hallmark in a range of neurodegenerative diseases and type II diabetes, as well as physiological processes of aggregate clearance.

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The nucleus is a quality control center for non-imported mitochondrial proteins

10.1101/2020.06.26.173781 ◽

2020 ◽

Cited By ~ 1

Author(s):

Viplendra P.S. Shakya ◽

William A. Barbeau ◽

Tianyao Xiao ◽

Christina S. Knutson ◽

Adam L. Hughes

Keyword(s):

Quality Control ◽

Steady State ◽

Nuclear Protein ◽

Protein Quality ◽

Mitochondrial Proteins ◽

Mitochondrial Targeting ◽

Mitochondrial Import ◽

Control Center ◽

Mitochondrial Impairment ◽

Precursor Proteins

AbstractMitochondrial import deficiency causes cellular stress due to the accumulation of non-imported mitochondrial precursor proteins. Despite the burden mis-localized mitochondrial precursors place on cells, our understanding of the systems that dispose of these proteins is incomplete. Here, we catalog the location and steady-state abundance of mitochondrial precursor proteins during mitochondrial impairment in S. cerevisiae. We find that a number of non-imported mitochondrial proteins localize to the nucleus, where they are eliminated by proteasome-based nuclear protein quality control. Recognition of mitochondrial precursors by the nuclear quality control machinery requires the presence of an N-terminal mitochondrial targeting sequence (MTS), and impaired breakdown of precursors leads to their buildup in nuclear-associated foci. These results identify the nucleus as a key destination for the disposal of non-imported mitochondrial precursors.

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Armand-Frappier Outstanding Student Award — Role of ATP-dependent proteases in antibiotic resistance and virulence

Canadian Journal of Microbiology ◽

10.1139/cjm-2012-0681 ◽

2013 ◽

Vol 59 (1) ◽

pp. 1-8 ◽

Cited By ~ 10

Author(s):

Elena B.M. Breidenstein ◽

Robert E.W. Hancock

Keyword(s):

Escherichia Coli ◽

Quality Control ◽

Antibiotic Resistance ◽

Protein Quality ◽

Human Pathogen ◽

Broad Array ◽

Living Organisms ◽

Opportunistic Human Pathogen ◽

Novel Therapeutic

ATP-dependent proteases are found in nearly all living organisms and are known to play important roles in protein quality control, including protein degradation and protein refolding. ATP-dependent proteases have been well characterized in Escherichia coli. However, in the opportunistic human pathogen Pseudomonas aeruginosa, the role of these proteases is only starting to be understood. This review will discuss the most recent research regarding the role of ATP-dependent proteases, particularly Lon and ClpP, in P. aeruginosa. These studies have revealed that despite the fact that they are not traditional regulators, these proteases are involved in regulating a multitude of processes, including antibiotic resistance and virulence, implicating a broad array of functions that these intracellular proteases have in Pseudomonas. These results are also relevant in the context of drug therapy, since ClpP and Lon are good candidates to become novel therapeutic targets to combat Pseudomonas infections.

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