Thomas Schmitt

and 9 more

Background: Pemphigus vulgaris (PV) is a severe autoimmune skin disease. Autoantibodies in PV (PV-IgG) targeting desmoglein (DSG)1 are required for loss of desmosome adhesion and skin blistering. Objectives: The aim was to connect the single steps of a Ca2+ flux dependent pathway and show it’s importance for the pathogenesis of pemphigus vulgaris. Methods: Applied methods include immunoprecipitation, Ca2+-flux analysis with FURA2-AM, analysis of protein phosphorylation with Western-blotting, Immunofluorescence, investigation of loss of adhesion in dissociation assays and human skin ex-vivo blistering model. Results: PV-IgG but not a DSG3-specific monoclonal antibody (AK23) caused Ca2+ influx in primary human keratinocytes. Phosphatidyl inositol 4 kinase-α (PI4K) interacts with DSG1 but not DSG3. Its downstream targets, phospholipase-C-γ1 (PLC) and protein-kinase-C α, similar to p38MAPK interacted with both. PLC was activated by PV-IgG but not by AK23. PLC regulates the release of Inositol-1,4,5-trisphosphate (IP3) causing IP3-receptor (IP3R) activation and Ca2+ flux from the endoplasmic reticulum into the cytosol. This stimulates Ca2+-release-activated-channels (CRAC) causing Ca2+ influx. Inhibitors against PI4K, PLC, IP3R or CRAC effectively blocked PV-IgG-induced Ca2+ influx and ameliorated alterations of DSG1 and 3 localization, keratin filament retraction, actin disruption and loss of cell adhesion in vitro. Moreover, inhibiting PLC was protective against blister formation, redistribution of DSG1 and 3 and actin disruption in human skin ex vivo. Conclusions: These results demonstrate that Ca2+-mediated signalling is important for pemphigus pathology and dependent on the autoantibody profile, with different roles for the Dsg1 and Dsg3 complexes. PLC could be an interesting pharmaceutical target.