Keratinocyte adhesion and signaling in the skin blistering disease pemphigus vulgaris

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Project Summary/Abstract Desmosomes are adhesive intercellular junctions that play critical roles in epidermal homeostasis by mediating robust cell-cell adhesion and by modulating signaling pathways that regulate epidermal differentiation. The importance of desmosomes is highlighted by numerous autoimmune and inherited skin diseases that compromise desmosome function and cause epidermal fragility. These diseases include pemphigus vulgaris (PV), a severe autoimmune epidermal blistering disease caused by autoantibodies (IgG) directed against the desmosomal cadherin desmoglein-3 (Dsg3). The precise mechanism by which PV IgG disrupt desmosome adhesion and trigger signaling pathways associated with the loss of adhesion are not well understood. This limitation has hindered the development of new therapies that can spare or eliminate the need for immunosuppressive treatments which can pose risks for patient safety. In the current proposal, we outline a series of cutting edge imaging approaches that will resolve with previously unachievable detail precisely how PV IgG disrupt adhesion. Aim 1 studies will determine how pemphigus IgG disrupt desmosome dynamics, architecture, and function using cryo-EM, live cell imaging, and molecular dynamics simulations. In Aim 2, we focus on how keratinocytes respond to pemphigus IgG and the role of Ca2+ signaling and endoplasmic reticulum stress pathways in the endocytosis of desmosomal proteins and in the inflammatory responses associated with desmosome disruption in both cultured cells and patient tissues. The outcome of these studies will produce fundamentally new conceptual models for desmosome regulation and will form a foundation for the treatment of skin diseases associated with loss of desmosome adhesion.