PA28, an activator of the 20 S proteasome, is composed of two nonidentical but homologous subunits.

Mott, Joni D.; Pramanik, Bikash C.; Moomaw, Carolyn R.; Afendis, Steven J.; DeMartino, George N.; Slaughter, Clive A.

doi:10.1016/s0021-9258(18)31717-4

Cited by 59 publications

(10 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…PA700 requires ATP to bind to the MCP in order to stimulate peptidase activity while PA28 does not. PA28 is composed of two nonidentical (molecular mass ∼27.3 and 28.6 kDa), but homologous subunits (Mott et al, 1994). Using immunoelectron microscopy, PA28 has been shown to form a regulatory cap on top of the stacked rings of the MCP (Gray et al, 1994).…”

mentioning

confidence: 99%

Activation of the Multicatalytic Endopeptidase by Oxidants. Effects on Enzyme Structure

1996

View full text Add to dashboard Cite

It is well established that the functional properties of proteins can be compromised by oxidative damage and, in vivo, proteins modified by oxidants are rapidly degraded. It was hypothesized that oxidants may also affect the ability of proteases to hydrolyze peptides and proteins. We therefore examined the effect of oxidants on the endopeptidase activities of the 650 kDa 20S proteasome or multicatalytic endopeptidase (MCP), which is thought to play a central role in nonlysosomal protein breakdown. Treatment of the MCP with the oxidant system, FeSO4-EDTA-ascorbate, stimulated the peptidase activities of the MCP while H2O2 treatment showed little or no stimulation. However, treatment of the MCP with FeSO4-EDTA-ascorbate or H2O2 stimulated proteinase activity by 480% and 730%, respectively. An endogenous activator of the MCP, PA28, stimulated the acidic, basic, and hydrophobic peptidase activities of the MCP, but had no effect on proteolytic activity. Treatment of PA28 with oxidants in the presence of MCP or alone did not greatly affect PA28's ability to activate the peptidase activities of the MCP. Using nondenaturing polyacrylamide gel electrophoresis, structural alterations in the enzyme which may be responsible for the activation of peptidase and protease activities following exposure to oxidants were investigated. Treatment of the MCP with reagents that activate proteolysis, including H2O2, as well as the serine protease inhibitor 3,4-dichloroisocoumarin and the cysteine protease inhibitor p-(chloromercuri) benzenesulfonic acid, all caused dissociation of the 650 kDa MCP. However, exposure to FeSO4-EDTA-ascorbate resulted in little or no dissociation of the complex. The MCP complex dissociated by p-(chloromercuri) benzenesulfonic acid could be reassociated upon treatment with the reducing agent dithiothreitol, but dithiothreitol failed to completely reassociate 3,4-dichloroisocoumarin- or H2O2 treated MCP. Therefore, chemical modification of the MCP can cause activation with varying degrees of complex dissociation. These results suggest that metabolites, such as reactive oxygen species, in addition to endogenous proteins, such as PA28, are capable of modulating MCP activity.

show abstract

mentioning

confidence: 99%

Activation of the Multicatalytic Endopeptidase by Oxidants. Effects on Enzyme Structure

1996

View full text Add to dashboard Cite

show abstract

“…PA28α-deficient ( Psme1 -/- ) mice are not commercially available, so we evaluated the role of PA28α using BMDMs derived from PA28αβ-deficient ( Psme1/2 -/- ) mice (Preckel et al, 1999). PA28α associates with PA28β to form the PA28αβ (11S) proteasome regulator (Mott et al, 1994). PA28β is homologous to PA28α but is dependent on PA28α for activity and is hypothesized to enhance the interaction of PA28α with 20S proteolytic proteasome core particles (CPs) (Wilk et al, 2000).…”

Section: Resultsmentioning

confidence: 99%

“…LegC4 impairs resolution of oxidative proteotoxic stress. In cells of the innate immune system, PA28a is produced in response to oxidative stress, TNF, or IFN-g and forms a heteroheptameric complex with PA28b to assemble the 11S (PA28ab) proteasome regulator (2,16,18,19).…”

Section: Legc4 Binds Host Proteasome Activator (Pa)28a To Gain Insight Into the Mechanism Ofmentioning

confidence: 99%

“…LegC4 impairs resolution of oxidative proteotoxic stress. In cells of the innate immune system, PA28ab is produced in response to oxidative stress, TNF, or IFN-g (Fabunmi et al, 2001;Hallermalm et al, 2001;Mott et al, 1994;Pickering et al, 2010), which provides an explanation as to why LegC4 confers a growth phenotype within cytokine-activated cells. Induced PA28ab associates with proteasome core particles (CPs) to generate antigenic peptides and resolve oxidative stress by facilitating ubiquitin-independent proteasomal degradation of oxidant-damaged (carbonylated) proteins (Graaf et al, 2011;Li et al, 2010).…”

Section: Legc4-mediated Restriction Of L Pneumophila Is Abolished In ...mentioning

confidence: 99%

See 1 more Smart Citation

Effector-mediated subversion of proteasome activator (PA)28αβ enhances host defense againstLegionella pneumophilaunder inflammatory and oxidative stress conditions

Ngwaga

Chauhan

Salberg

et al. 2021

Preprint

View full text Add to dashboard Cite

Legionella pneumophila causes Legionnaires' Disease via replication within host macrophages using an arsenal of hundreds of translocated virulence factors termed effector proteins. Effectors are critical for intracellular replication but can also enhance pathogen clearance in mammalian hosts via effector-triggered immunity. The effector LegC4 confers a fitness disadvantage on L. pneumophila within mouse models of Legionnaires' Disease and uniquely potentiates the antimicrobial activity of macrophages activated with either tumor necrosis factor (TNF) or interferon (IFN)-γ. Here, we investigated the mechanism of LegC4 function. We found that LegC4 binds proteasome activator (PA)28α, a subunit of the PA28αβ (11S) proteasome regulator, and that the LegC4 restriction phenotype is abolished within PA28αβ-deficient macrophages. PA28αβ facilitates ubiquitin-independent proteasomal degradation of oxidant-damaged proteins. Impaired proteasome activity results in compensatory upregulation of lysosomal degradation pathways to relieve oxidative proteotoxic stress. We found that LegC4 impairs the resolution of oxidative proteotoxic stress and enhances phagolysosomal fusion with the Legionella-containing vacuole. PA28αβ has been traditionally associated with antigen presentation and adaptive immunity; however, our data support a model whereby suppression of PA28αβ by LegC4 impairs resolution of oxidative proteotoxic stress, which culminates in the lysosomal killing of L. pneumophila within activated macrophages. This work provides a solid foundation on which to evaluate induced proteasome regulators as mediators of cell-autonomous immunity.

show abstract

“…Proteasome activity was measured by determining rates of hydrolysis of AMC-linked peptides such as Suc-LLVY-AMC, as described previously. 39 In brief, 20S proteasomes and any other components of specific reactions, such as PI31, carboxylbenzyltyrosine-alanine (z-YA), 19 SDS, 16 and activator proteins such as PA28, 41,42 from reactions containing no enzyme was subtracted from enzyme-containing samples. In given experiments, reactions were conducted in triplicate and rates of hydrolysis were expressed as mean values of arbitrary fluorescent units (AFU)/ min/μg protein, ± standard deviation.…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Differential Interactions of the Proteasome Inhibitor PI31 with Constitutive and Immuno-20S Proteasomes

Wang,

Kjellgren,

DeMartino

2024

Biochemistry

View full text Add to dashboard Cite

PI31 (Proteasome Inhibitor of 31,000 Da) is a 20S proteasome binding protein originally identified as an in vitro inhibitor of 20S proteasome proteolytic activity. Recently reported cryo-electron microscopy structures of 20S−PI31 complexes have revealed that the natively disordered proline-rich C-terminus of PI31 enters the central chamber in the interior of the 20S proteasome and interacts directly with the proteasome's multiple catalytic threonine residues in a manner predicted to inhibit their enzymatic function while evading its own proteolysis. Higher eukaryotes express an alternative form of the 20S proteasome (termed "immuno-proteasome") that features genetically and functionally distinct catalytic subunits. The effect of PI31 on immuno-proteasome function is unknown. We examine the relative inhibitory effects of PI31 on purified constitutive (20Sc) and immuno-(20Si) 20S proteasomes in vitro and show that PI31 inhibits 20Si hydrolytic activity to a significantly lesser degree than that of 20Sc. Unlike 20Sc, 20Si hydrolyzes the carboxyl-terminus of PI31 and this effect contributes to the reduced inhibitory activity of PI31 toward 20Si. Conversely, loss of 20Sc inhibition by PI31 point mutants leads to PI31 degradation by 20Sc. These results demonstrate unexpected differential interactions of PI31 with 20Sc and 20Si and document their functional consequences.

show abstract

PA28, an activator of the 20 S proteasome, is composed of two nonidentical but homologous subunits.

Cited by 59 publications

References 27 publications

Activation of the Multicatalytic Endopeptidase by Oxidants. Effects on Enzyme Structure

Activation of the Multicatalytic Endopeptidase by Oxidants. Effects on Enzyme Structure

Effector-mediated subversion of proteasome activator (PA)28αβ enhances host defense againstLegionella pneumophilaunder inflammatory and oxidative stress conditions

Differential Interactions of the Proteasome Inhibitor PI31 with Constitutive and Immuno-20S Proteasomes

Contact Info

Product

Resources

About