Proteomic analysis of neutrophils in ANCA-associated vasculitis reveals a dysregulation in proteinase 3-associated proteins such as annexin-A1 involved in apoptotic cell clearance

Granulomatosiswith polyangiitis(GPA) is an autoimmune vasculitisassociated with anti-neutrophil-cytoplasmic antibodies(ANCA) against proteinase 3leading to kidney damage. Neutrophilsfrom those patients have increased expression of membrane proteinase 3during apoptosis. Here we examined whether neutrophilsfrom patients with GPA have dysregulated protein expressions associated with apoptosis. A global proteomic analysis was performed comparing neutrophilsfrom patients with GPA, with healthy individuals under basal conditions and during apoptosis. At disease onset, the cytosolic proteome of neutrophilsof patients with GPA before treatment was significantly different from healthy controls, and this dysregulation was more pronounced following ex vivo apoptosis. Proteins involved in cell death/survival were altered in neutrophilsof patients with GPA. Several proteins identified were PR3-binding partners involved in the clearance of apoptotic cells, namely calreticulin, annexin-A1and phospholipid scramblase1. These proteins form a platform at the membrane of apoptotic neutrophilsin patients with GPA but not healthy individuals and this was associated with the clinical presentation of GPA. Thus, our study shows that neutrophilsfrom patients with GPA have an intrinsic dysregulation in proteins involved in apoptotic cell clearance, which could contribute to the unabated inflammation and autoimmunity in GPA. Hence, harnessing these dysregulated pathways could lead to novel biomarkers and targetedtherapeutic opportunitiesto treat kidney disease.