aPKC/Par3/Par6 polarity complexes regulate podocyte motility and crescent formation in the progression of ANCA-associated vasculitis

Abstract Objectives Podocyte bridging may be a key initial event occurring early in crescent formation. This study aims to probe the underlying mechanism of atypical protein kinase C (aPKC)/protease-activated receptor 3(Par3)/Par6 polarity complexes on podocyte motility and crescent formation during the progression of antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV). Methods The effects of anti-TNF-α monoclonal antibody (mAb) on the crescent formation, localization and expression of aPKC/Par3/Par6 polarity complexes, and activities of small GTPases (Rho/Rac1/Cdc42) were explored in an AAV mouse model. Podocytes were stimulated in vitro by TNF-α and myeloperoxidase (MPO)-ANCA positive serum collected from patients with microscopic polyangiitis (MPA). Then, podocyte motility, aPKC/Par3/Par6 polarity protein expression and small GTPases activity were measured. The impacts of heat shock protein 70 (HSP70), a type of molecular chaperone, on the phosphorylation of aPKC was evaluated. Results Anti-TNF-α mAb inhibited crescent formation and restored the localization of aPKC/Par3/Par6 polarity complexes in the glomerulus of the AAV mouse model. Both MPO-ANCA-positive serum and TNF-α stimulation significantly induced podocyte motility by inhibiting of aPKC phosphorylation and detachment of aPKC/Par3/Par6 polarity complexes. Overexpression of HSP70 increased p-aPKC level and inhibited podocyte motility stimulated by either MPO-ANCA-positive serum or TNF-α. Conclusion The podocyte polarity preserved by aPKC/Par3/Par6 polarity complexes, especially the phosphorylation status of aPKC, may play an important role in the crescent formation of AAV. The inhibition of TNF-α prevents the crescent formation in AAV via, at least partly, inhibiting podocyte polarity loss and motility.