Role of protein kinase C subtype-specific signalling in regulating adhesion in human keratinocytes and skin in pemphigus

Background: Autoantibodies in the blistering skin disease pemphigus primarily target desmosomal cadherins and cause loss of keratinocyte adhesion and epidermal blistering via signalling events. Pemphigus vulgaris (PV) 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.

Objectives: To investigate the roles of PKC subtypes in in PV IgG-induced epidermal blistering in human skin.

Methods: We applied an ex vivo human skin organ culture model, dispase-based dissociation assays, Western blot analysis and confocal and simulated emission depletion (STED) microscopy, to study the underlying mechanisms of pemphigus pathogenesis in vitro.

Results: The inhibitor of atypical PKC (aPKC) isoforms CRT0066854 (CRT) completely abolished acantholysis, whereas the conventional PKC (cPKC) inhibitor Gö6976 (Gö) did not. In cultured keratinocytes, both CRT and Gö effectively inhibited the 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 and PF IgG was blocked by the inhibition of cPKC but not of aPKC. Mechanistically, cPKC and aPKC were both required for PV IgG-induced translocation of PKC towards peripheral keratin filaments and conformational changes in desmoplakin.

Conclusions: These findings show that aPKC is critical for the blistering seen in human epidermis in PV and is dependent on the autoantibody profile.