The role of PKC subtype-specific signaling in the regulation of adhesion in human keratinocytes and skin in pemphigus

Aim Autoantibodies, in the blistering skin disease pemphigus primarily target desmosomal cadherins and cause loss of keratinocyte adhesion and epidermal blistering via signaling events. Pemphigus vulgaris is associated with autoantibodies (PV-IgG) against desmoglein (Dsg)1 and Dsg3 and pemphigus foliaceus (PF) with antibodies against Dsg1 only. In previous studies, protein kinase C (PKC) inhibition was protective in murine but not in human epidermis. Here, we investigated the roles of PKC subtypes for pemphigus pathogenesis. Methods We applied the ex vivo human skin organ culture model, dispase-based dissociation assays, Western blot analysis, confocal and simulated emission depletion (STED) microscopy to study underlying mechanisms in vitro. Results First, we investigated the role of PKC subtypes for PV-IgG-induced epidermal blistering in human skin. Surprisingly, the inhibitor of atypical PKC isoforms (aPKC) CRT0066854 (CRT) completely abolished acantholysis whereas the conventional PKC (cPKC) inhibitor Gö6976 (Gö) did not. In cultured keratinocytes, both CRT and Gö were effective to inhibit loss of cell adhesion, keratin filament retraction and Dsg3 depletion in response to PV-IgG as well the pathogenic Dsg3-specific IgGs AK23 and 2G4. In contrast, reduced cell adhesion and keratin filament retraction in response to PKC activation by phorbol-12-myristate-13-acetate (PMA) and PF-IgG was blocked by inhibition of cPKC but not of aPKC. Mechanistically, both cPKC and aPKC were required for PV-IgG-induced translocation of PKC towards peripheral keratin filaments and conformational changes in Dp. Conclusion These findings demonstrate that aPKC is critical for blistering in human epidermis in PV dependent on the autoantibody profile.