Oxidative Stress-Mediated YAP Dysregulation Contributes to the Pathogenesis of Pemphigus Vulgaris

Abstract

Pemphigus Vulgaris (PV) is a life-threatening autoimmune disease manifested with blisters in the skin and mucosa and caused by autoantibodies against adhesion protein desmoglein-3 (Dsg3) expressed in epithelial membrane linings of these tissues. Despite many studies, the pathogenesis of PV remains incompletely understood. Recently we have shown Dsg3 plays a role in regulating the yes-associated protein (YAP), a co-transcription factor and mechanical sensor, and constraining reactive oxygen species (ROS). This study investigated the effect of PV sera as well as the anti-Dsg3 antibody AK23 on these molecules. We detected elevated YAP steady-state protein levels in PV cells surrounding blisters and perilesional regions and in keratinocytes treated with PV sera and AK23 with concomitant transient ROS overproduction. Cells treated with hydrogen peroxide also exhibited augmented nuclear YAP accompanied by reduction of Dsg3 and α-catenin, a negative regulator of YAP. As expected, transfection of α-catenin-GFP plasmid rendered YAP export from the nucleus evoked by hydrogen peroxide. In addition, suppression of total YAP was observed in hydrogen peroxide treated cells exposed to antioxidants with enhanced cell-cell adhesion being confirmed by decreased fragmentation in the dispase assay compared to hydrogen peroxide treatment alone. On the other hand, the expression of exogenous YAP disrupted intercellular junction assembly. In contrast, YAP depletion resulted in an inverse effect with augmented expression of junction assembly proteins, including Dsg3 and α-catenin capable of abolishing the effect of AK23 on Dsg3 expression. Finally, inhibition of other kinase pathways, including p38MAPK, also demonstrated suppression of YAP induced by hydrogen peroxide. Furthermore, antioxidant treatment of keratinocytes suppressed PV sera-induced total YAP accumulation. In conclusion, this study suggests that oxidative stress coupled with YAP dysregulation attributes to PV blistering, implying antioxidants may be beneficial in the treatment of PV.

Evolving Mechanisms in the Pathophysiology of Pemphigus Vulgaris: A Review Emphasizing the Role of Desmoglein 3 in Regulating p53 and the Yes-Associated Protein

“…Elevated apoptotic factors such as Bax, FasL, and caspases as well as downregulation of the apoptotic inhibitory protein Bcl-2 in PV have been reported. Our recent studies shed new light on the unprecedented roles of DSG3 and suggest its mediated signaling towards p53, YAP and ROS in cellular stress response with the evidence of dysregulation of these axes being demonstrated in PV [ 15 , 81 , 85 , 86 , 112 ]. Elucidation of the underlying mechanisms could be a fertile area for future research [ 113 ].…”

“… Schematic representation of the recently identified pathways in PV [ 15 , 81 ]. PV IgG targeting DSG3 perturbs its action in anti-stress response and causes elevated ROS generation, leading to DNA DSBs, p53 activation via ATM and consequently apoptosis.…”

“…A recent study by our group has demonstrated that elevated ROS production can be evoked by treating keratinocytes with PV patient’s sera as well as a pathogenic mouse monoclonal antibody AK23, with concomitant accumulation of Yes-associated protein (YAP) especially in the cytoplasm of antibody-treated cells [ 81 ]. Importantly, a marked increase of YAP was also detected in the oral mucous membrane of PV patients with elevated cytoplasmic and/or nuclear YAP found in cells not only surrounding blisters but also in the perilesional regions where the split of keratinocytes was not shown.…”

“…Additionally, elevated YAP was demonstrated in cells exposed to hydrogen peroxide that mimics cellular oxidative stress, with numerous protein aggregates located at the cell borders. Furthermore, the effect of YAP on cell junction formation and maintenance was investigated and showed that expression of exogenous YAP led to disruption of cell junctions, whereas an adverse effect was observed in cells with YAP silencing that enhanced DSG3 expression which was capable of abrogating AK23-mediated pathogenicity to DSG3 [ 81 ]. These findings collectively suggest that antibody-induced oxidative stress and cytoplasmic YAP accumulation may attribute to the disruption of cell junctions and pemphigus acantholysis ( Figure 1 ).…”

“…Paradoxically, elevated YAP was shown in PV with variations of its cellular localization. Increased YAP nuclear expression was pronounced in PV perilesional regions [ 81 ] suggesting activation of YAP likely occurs at the early stages of the disease process when the autoantibodies target DSG3 and/or other surface proteins. However, the different effects of monoclonal versus polyclonal IgGs, as well as PV IgG targeting non-DSGs, on ROS and YAP expression remain largely unknown.…”