Allosteric modulation of proteinase 3 activity by anti-neutrophil cytoplasmic antibodies in granulomatosis with polyangiitis.
Anti-neutrophil cytoplasmic antibodies (ANCA) with proteinase 3 (PR3) specificity are a useful laboratory biomarker for the diagnosis of Granulomatosis with Polyangiitis (GPA) and are believed to be implicated in the pathogenesis. It has been repeatedly suggested that disease activity of GPA is more closely related to the appearance and rise of PR3-inhibiting ANCA than to an increase of total ANCA. Previous studies on a limited number of patient samples, however, have yielded inconclusive results. To overcome the previous methodological limitations, we established a new ultrasensitive method to quantify the inhibitory capacity of PR3-ANCA using small volumes of plasma from patients with GPA. A large collection of longitudinally-collected samples from the Wegener Granulomatosis Etanercept Trial (WGET) became available to us to determine the functional effects of ANCA on PR3 in comparison to clinical disease manifestations. In these patient samples we not only detected PR3-ANCA with inhibitory capacity, but also PR3-ANCA with enhancing effects on PR3 activity. However no correlation of these activity-modulating PR3-ANCA with disease activity at either the time of enrollment or over the course of disease was found. Only patients with pulmonary involvement, especially patients with nodule formation in the respiratory tract, showed a slight, but not significant, decrease of inhibitory capacity. Epitope mapping of the activity-modulating PR3-ANCA revealed a binding on the active site surface of PR3. Yet these ANCA were able to bind to PR3 with an occupied active site cleft, indicating an allosteric mechanism of inhibition. The recently described signal ratio between the MCPR3-3 and MCPR3-2 capture ELISA was consistent with the binding of activity-modulating ANCA to the active site surface. Evidence for a shared epitope between activity-modulating PR3-ANCA and MCPR3-7, however, was very limited, suggesting that a majority of PR3-ANCA species do not inhibit PR3 by the same mechanism as previously reported for MCPR3-7.
Comprehensive Pneumology Center, Institute of Lung Biology and Disease (iLBD), University Hospital, Ludwig Maximilians University and Helmholtz Zentrum München, Member of the German Center of Lung Research, Max-Lebsche-Platz 31, 81377 Munich, Germany.
Lisa C
LC
Hinkofer
Thoracic Diseases Research Unit, Stabile Bldg. 8-56, Division of Pulmonary and Critical Care Medicine, Mayo Clinic and Foundation, 200 First Street SW, Rochester, MN 55905, USA.
Amber M
AM
Hummel
Massachusetts General Hospital, 55 Fruit St, Boston, MA 02114, USA.
John H
JH
Stone
Center for Vasculitis Care and Research, Cleveland Clinic, 9500 Euclid Avenue, Cleveland, OH 44195, USA.
Gary S
GS
Hoffman
Vasculitis Center, Division of Rheumatology and the Department of Biostatistics and Epidemiology, University of Pennsylvania, Philadelphia, 19104 PA, USA.
Peter A
PA
Merkel
Hospital for Special Surgery, 535 E 70th St, New York, NY 10021, USA.
E Robert F
ER
Spiera
Duke University Medical Center, Division of Rheumatology and Immunology, DUMC 3874, Durham, NC 27708, USA.
William
W
St Clair
University of Michigan, 500 S State St, Ann Arbor, MI 48109, USA.
Joseph W
JW
McCune
Genentech, One DNA Way, South San Francisco, CA 94080, USA; University of California San Francisco, San Francisco, CA 94143, USA.
John C
JC
Davis
Thoracic Diseases Research Unit, Stabile Bldg. 8-56, Division of Pulmonary and Critical Care Medicine, Mayo Clinic and Foundation, 200 First Street SW, Rochester, MN 55905, USA.
Ulrich
U
Specks
Comprehensive Pneumology Center, Institute of Lung Biology and Disease (iLBD), University Hospital, Ludwig Maximilians University and Helmholtz Zentrum München, Member of the German Center of Lung Research, Max-Lebsche-Platz 31, 81377 Munich, Germany; Max Planck Institute of Neurobiology, Planegg-Martinsried, Germany. Electronic address: dieter.jenne@helmholtz-muenchen.de.
Dieter E
DE
Jenne
D000494:Allosteric Regulation / Q000276:immunology; D019268:Antibodies, Antineutrophil Cytoplasmic / Q000378:metabolism*; D001666:Binding Sites, Antibody / Q000276:immunology; D015415:Biomarkers / Q000378:metabolism*; D018450:Disease Progression; D018604:Epitope Mapping / Q000379:methods*; D005500:Follow-Up Studies; D014890:Granulomatosis with Polyangiitis / Q000201:enzymology / Q000276:immunology*; D006801:Humans; D053146:Myeloblastin / Q000276:immunology / Q000378:metabolism*
D019268:Antibodies, Antineutrophil Cytoplasmic; D015415:Biomarkers; D053146:Myeloblastin
ANCA; Disease activity; Granulomatosis with polyangiitis; Inhibition; Proteinase 3