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Updated: May 30, 2026
Removal and Replacement of Endogenous Ligands from Lipid-Bound Proteins and Allergens
Published on: February 24, 2021
Molecular analysis of the membrane insertion domain of proteinase 3, the Wegener's autoantigen, in RBL cells:
Chahrazade Kantari1, Arnaud Millet, Julie Gabillet
1INSERM U1016, Institut Cochin, Paris, France.
Abstract:
PR3, also called myeloblastin, is a neutrophil serine protease that promotes myeloid cell proliferation by cleaving the cyclin-dependent kinase inhibitor p21(cip1/waf1). In addition, it is the target of ANCA in GPA, a necrotizing vasculitis. Anti-PR3 ANCA binding to membrane-expressed PR3 triggers neutrophil activation, potentiating vascular inflammation. This study performed in RBL cells identifies the structural motifs of PR3 membrane anchorage and examines its impact on PR3 proinflammatory and proliferative functions. With the use of MD simulations and mutagenesis, we demonstrate that the mutations of four hydrophobic (F180, F181, L228, F229) or four basic (R193, R194, K195, R227) amino acids abrogated PR3 membrane anchorage. The hydrophobic patch-deficient PR3 mutant (PR34H4A) was still able to cleave the synthetic substrate Boc-Ala-Pro-Val in cell lysates. However, in contrast to WT PR3, PR34H4A was not expressed at the plasma membrane after degranulation and failed to cleave extracellular fibronectin, was not externalized after apoptosis and did not impair macrophage phagocytosis of apoptotic cells, did not promote myeloid cell proliferation and failed to cleave p21/waf1. PR3 membrane insertion appears to be pivotal for its proinflammatory activities, such as extracellular proteolysis and impairment of apoptotic cell clearance, but also for myeloid cell proliferation. Targeting membrane-associated PR3 might constitute a novel, anti-inflammatory therapeutic strategy in inflammatory disease especially in vasculitis, but this approach has to be validated in mature neutrophils.
Insights
Membrane anchorage is crucial for proteinase 3 (PR3) to drive myeloid cell proliferation and inflammation. Targeting membrane-associated PR3 may offer a new anti-inflammatory strategy for vasculitis.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- Proteinase 3 (PR3), or myeloblastin, is a neutrophil serine protease implicated in myeloid cell proliferation and autoimmune vasculitis.
- Anti-PR3 ANCA antibodies bind to membrane-expressed PR3, activating neutrophils and exacerbating vascular inflammation.
Purpose of the Study:
- To identify structural motifs of PR3 essential for membrane anchorage.
- To investigate the impact of PR3 membrane anchorage on its pro-inflammatory and proliferative functions.
Main Methods:
- Molecular dynamics (MD) simulations and mutagenesis were employed to identify key amino acids for PR3 membrane anchoring.
- Functional assays assessed the enzymatic activity, cellular localization, and biological effects of wild-type (WT) PR3 and PR3 mutants.
Main Results:
- Mutations in hydrophobic (F180, F181, L228, F229) or basic (R193, R194, K195, R227) amino acid clusters abrogated PR3 membrane anchorage.
- A hydrophobic patch-deficient mutant (PR34H4A) retained substrate cleavage in lysates but failed to anchor to the plasma membrane.
- Loss of membrane anchorage prevented PR3-mediated extracellular fibronectin cleavage, impaired apoptotic cell clearance, and abolished myeloid cell proliferation induction via p21/waf1 cleavage.
Conclusions:
- PR3 membrane insertion is pivotal for its pro-inflammatory activities, including extracellular proteolysis and interference with apoptotic cell clearance.
- PR3 membrane association is also critical for promoting myeloid cell proliferation.
- Targeting membrane-associated PR3 presents a potential anti-inflammatory therapeutic strategy for inflammatory diseases, particularly vasculitis, warranting further validation in neutrophils.
