Reduced glutathione as a physiological co-activator in the activation of peptidylarginine deiminase

Damgaard, Dres; Bjørn, Mads Emil; Steffensen, Maria Abildgaard; Pruijn, Ger J. M.; Nielsen, Claus Henrik

doi:10.1186/s13075-016-1000-7

Cited by 53 publications

(55 citation statements)

References 35 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In fact, the belief that PAD4 is activated by ROS during NETosis prevails to this day (67), although evidence to support this concept is lacking. Since a reducing environment is necessary to maintain the active site free thiol Cys645 required for PAD4 function (68, 69), we can anticipate that oxidation of PAD4 by ROS will instead inactivate the enzyme.…”

Section: Introductionmentioning

confidence: 99%

A Critical Reappraisal of Neutrophil Extracellular Traps and NETosis Mimics Based on Differential Requirements for Protein Citrullination

2016

View full text Add to dashboard Cite

NETosis, an antimicrobial form of neutrophil cell death, is considered a primary source of citrullinated autoantigens in rheumatoid arthritis (RA) and immunogenic DNA in systemic lupus erythematosus (SLE). Activation of the citrullinating enzyme peptidylarginine deiminase type 4 (PAD4) is believed to be essential for neutrophil extracellular trap (NET) formation and NETosis. PAD4 is therefore viewed as a promising therapeutic target to inhibit the formation of NETs in both diseases. In this review, we examine the evidence for PAD4 activation during NETosis and provide experimental data to suggest that protein citrullination is not a universal feature of NETs. We delineate two distinct biological processes, leukotoxic hypercitrullination (LTH) and defective mitophagy, which have been erroneously classified as “NETosis.” While these NETosis mimics share morphological similarities with NETosis (i.e., extracellular DNA release), they are biologically distinct. As such, these processes can be readily classified by their stimuli, activation of distinct biochemical pathways, the presence of hypercitrullination, and antimicrobial effector function. NETosis is an antimicrobial form of cell death that is NADPH oxidase-dependent and not associated with hypercitrullination. In contrast, LTH is NADPH oxidase-independent and not bactericidal. Rather, LTH represents a bacterial strategy to achieve immune evasion. It is triggered by pore-forming pathways and equivalent signals that cumulate in calcium-dependent hyperactivation of PADs, protein hypercitrullination, and neutrophil death. The generation of citrullinated autoantigens in RA is likely driven by LTH, but not NETosis. Mitochondrial DNA (mtDNA) expulsion, the result of a constitutive defect in mitophagy, represents a second NETosis mimic. In the presence of interferon-α and immune complexes, this process can generate highly interferogenic oxidized mtDNA, which has previously been mistaken for NETosis in SLE. Distinguishing NETosis from LTH and defective mitophagy is paramount to understanding the role of neutrophil damage in immunity and the pathogenesis of human diseases. This provides a framework to design specific inhibitors of these distinct biological processes in human disease.

show abstract

Section: Introductionmentioning

confidence: 99%

A Critical Reappraisal of Neutrophil Extracellular Traps and NETosis Mimics Based on Differential Requirements for Protein Citrullination

2016

View full text Add to dashboard Cite

show abstract

“…Two potential sources of extracellular PADs have been suggested to be responsible for this process. These include PADs secreted from activated neutrophils, and PADs released during neutrophil death . Nevertheless, while there is convincing evidence that soluble PADs are found in RA synovial fluid, the mechanisms involved in extracellular PAD activation are not fully understood.…”

Section: The Glitch Of Extracellular Citrullination In Ramentioning

confidence: 99%

“…PAD activity requires a reducing environment to maintain the active site free thiol cysteine necessary for catalysis . The oxidizing extracellular environment, which contrasts with the reducing milieu inside cells, is therefore hostile for citrullination.…”

Section: The Glitch Of Extracellular Citrullination In Ramentioning

confidence: 99%

“…The oxidizing extracellular environment, which contrasts with the reducing milieu inside cells, is therefore hostile for citrullination. Indeed, neither endogenous nor recombinant PADs have catalytic activity in synovial fluid unless reducing agents, such as dithiothreitol or reduced glutathione, are exogenously added . Similarly, PADs secreted from activated neutrophils, during PMA‐induced NET formation, or from necrotic neutrophils are only active in the presence of high amounts of dithiothreitol .…”

Section: The Glitch Of Extracellular Citrullination In Ramentioning

confidence: 99%

“…Indeed, neither endogenous nor recombinant PADs have catalytic activity in synovial fluid unless reducing agents, such as dithiothreitol or reduced glutathione, are exogenously added . Similarly, PADs secreted from activated neutrophils, during PMA‐induced NET formation, or from necrotic neutrophils are only active in the presence of high amounts of dithiothreitol . In some cases, supraphysiologic amounts of calcium (>1.5 mM, with 1‐1.5 mM normally present in extracellular compartments) are also added exogenously to increase extracellular PAD activity .…”

Section: The Glitch Of Extracellular Citrullination In Ramentioning

confidence: 99%

See 2 more Smart Citations

Insights into the study and origin of the citrullinome in rheumatoid arthritis

Fert-Bober

Darrah

Andrade

2019

Immunological Reviews

View full text Add to dashboard Cite

The presence of autoantibodies and autoreactive T cells to citrullinated proteins and citrullinating enzymes in patients with rheumatoid arthritis (RA), together with the accumulation of citrullinated proteins in rheumatoid joints, provides substantial evidence that dysregulated citrullination is a hallmark feature of RA. However, understanding mechanisms that dysregulate citrullination in RA has important challenges. Citrullination is a normal process in immune and non‐immune cells, which is likely activated by different conditions (eg, inflammation) with no pathogenic consequences. In a complex inflammatory environment such as the RA joint, unique strategies are therefore required to dissect specific mechanisms involved in the abnormal production of citrullinated proteins. Here, we will review current models of citrullination in RA and discuss critical components that, in our view, are relevant to understanding the accumulation of citrullinated proteins in the RA joint, collectively referred to as the RA citrullinome. In particular, we will focus on potential caveats in the study of citrullination in RA and will highlight methods to precisely detect citrullinated proteins in complex biological samples, which is a confirmatory approach to mechanistically link the RA citrullinome with unique pathogenic pathways in RA.

show abstract

Generation of Distinct Patterns of Rheumatoid Arthritis Autoantigens by Peptidylarginine Deiminase Types 2 and 4 During Perforin‐Induced Cell Damage

Romero

Darrah

Andrade

2020

Arthritis & Rheumatology

View full text Add to dashboard Cite

Objective To address the independent roles of peptidylarginine deiminase type 2 (PAD2) and PAD4 in generating rheumatoid arthritis (RA) autoantigens by using a system that mimics intracellular citrullination in the RA joint. Methods PAD2‐ or PAD4‐expressing 293T cells and mock‐transfected cells were used as targets in cytotoxic assays using lymphokine‐activated killer cells, cytotoxic YT cell granule contents, or purified human perforin. Protein citrullination and autoantigen production were determined by immunoblotting using the anti–modified citrulline–Senshu method and RA sera (n = 30), respectively. Results RA sera recognized at least 3 categories of autoantigens in PAD‐expressing target cells killed by the cytotoxic lymphocyte granule–induced death pathway. These included: 1) autoantigens targeted in their native form, 2) citrullinated antigens, and 3) antigens cleaved by cytotoxic proteases (e.g., granzymes). Interestingly, although target cells expressing PAD2 or PAD4 showed prominent hypercitrullination of a broad range of proteins during cytotoxic granule–induced cell damage, autoantibodies in RA sera targeted only a very limited number of antigens in hypercitrullinated cells. Furthermore, RA sera showed distinct reactivities to autoantigens generated by PAD2 or PAD4. Conclusion The cytotoxic granule–induced death pathway has the capacity to modify antigens by inducing hypercitrullination and antigen cleavage in target cells. Interestingly, among a large number of citrullinated proteins generated by PAD2 and PAD4 in cells, only a few are likely involved in the production of autoantibodies in RA.

show abstract

Reduced glutathione as a physiological co-activator in the activation of peptidylarginine deiminase

Cited by 53 publications

References 35 publications

A Critical Reappraisal of Neutrophil Extracellular Traps and NETosis Mimics Based on Differential Requirements for Protein Citrullination

A Critical Reappraisal of Neutrophil Extracellular Traps and NETosis Mimics Based on Differential Requirements for Protein Citrullination

Insights into the study and origin of the citrullinome in rheumatoid arthritis

Generation of Distinct Patterns of Rheumatoid Arthritis Autoantigens by Peptidylarginine Deiminase Types 2 and 4 During Perforin‐Induced Cell Damage

Contact Info

Product

Resources

About