Background Pemphigus is a severe bullous autoimmune skin disease. Pemphigus foliaceus
(PF) is characterized by antidesmoglein (Dsg) 1 IgG causing epidermal blistering;
mucosal pemphigus vulgaris (mPV) by anti-Dsg3 IgG inducing erosions in the mucosa;
and mucocutaneous pemphigus vulgaris (PV) by affecting both, with autoantibodies targeting
Dsg1 and Dsg3. Objectives To characterize the Ca2+ flux pathway and delineate its
importance in pemphigus pathogenesis and clinical phenotypes caused by different antibody
profiles. Methods Immunoprecipitation, Ca2+ flux analysis, Western blotting, immunofluorescence
staining, dissociation assays and a human skin ex vivo model were used. Results PV
IgG and PF IgG, but neither Dsg3-specific monoclonal antibody (AK23) nor mPV IgG,
caused Ca2+ influx in primary human keratinocytes. Phosphatidylinositol 4-kinase alpha
interacts with Dsg1 but not with Dsg3. Its downstream target - phospholipase-C-gamma
1 (PLC) - was activated by PV IgG and PF IgG but not AK23 or mPV IgG. PLC releases
inositol 1,4,5-trisphosphate (IP3) causing IP3 receptor (IP3R) activation and Ca2+
flux from the endoplasmic reticulum into the cytosol, which stimulates Ca2+ release-activated
channels (CRAC)-mediated Ca2+ influx. Inhibitors against PLC, IP3R and CRAC effectively
blocked PV IgG and PF IgG-induced Ca2+ influx; ameliorated alterations of Dsg1 and
Dsg3 localization, and reorganization of keratin and actin filaments; and inhibited
loss of cell adhesion in vitro. Finally, inhibiting PLC or IP3R was protective against
PV IgG-induced blister formation and redistribution of Dsg1 and Dsg3 in human skin
ex vivo. Conclusions Ca2+-mediated signalling is important for epidermal blistering
and dependent on the autoantibody profile, which indicates different roles for signalling
complexes organized by Dsg1 and Dsg3. Interfering with PLC and Ca2+ signalling may
be a promising approach to treat epidermal manifestations of pemphigus.
