Pemphigus Vulgaris Autoantibodies Induce an Endoplasmic Reticulum Stress Response

Desmosomes are intercellular junctions that mediate cell–cell adhesion and are essential for maintaining tissue integrity. Pemphigus vulgaris (PV) is an autoimmune epidermal blistering disease caused by autoantibodies (IgG) targeting desmoglein 3, a desmosomal cadherin. PV autoantibodies cause desmosome disassembly and loss of cell–cell adhesion; however, the molecular signaling pathways that regulate these processes are not fully understood. Using high-resolution time-lapse imaging of live keratinocytes, we found that endoplasmic reticulum (ER) tubules make frequent and persistent contacts with internalizing desmoglein 3 puncta in keratinocytes treated with IgG of patients with PV. Biochemical experiments demonstrated that PV IgG activated ER stress signaling pathways, including both IRE1⍺ and PERK pathways, in cultured keratinocytes. Furthermore, ER stress transcripts were upregulated in the skin of patients with PV. Pharmacological inhibition of ER stress protects against PV IgG–induced desmosome disruption and loss of keratinocyte cell–cell adhesion, suggesting that ER stress may be an important pathomechanism and a therapeutically targetable pathway for PV treatment. These data support a model in which desmosome adhesion is integrated with ER function to serve as a cell adhesion stress sensor that is activated in blistering skin diseases.