Granzyme B Disrupts Epithelial Barrier Function

The epithelium functions as a barrier to the external environment, which is maintained in large part by cell junctions. Age‐related and chronic inflammatory conditions of the skin result in a loss of epithelial barrier integrity through the degradation of cell adhesion proteins. Granzyme B (GzmB) is a serine protease that accumulates in the extracellular milieu in a number of autoimmune skin conditions. As such, GzmB may contribute to the progressive loss of epithelial barrier function. We hypothesized that GzmB disrupts epithelial barrier function through the proteolytic cleavage of cell junction proteins. Human keratinocytes were treated with exogenous GzmB, in the presence or absence of a GzmB inhibitor. Subsequently, epithelial barrier function was assessed by Electric Cell‐substrate Impedance Sensing (ECIS) and immunofluorescence (confocal) microscopy was used to visualize E‐cadherin. GzmB treatment resulted in a loss of E‐cadherin staining on the cell membrane which was further supported by western blot analysis of cell supernatants and biochemical cleavage assays, where we observed a dose‐dependent increase in E‐cadherin fragmentation. E‐cadherin cleavage was markedly decreased when treated with a GzmB inhibitor. Moreover, ECIS analysis showed a noticeable decline in barrier function after GzmB treatment. In summary, GzmB contributes to a decline in epithelial barrier function in part through the proteolytic cleavage of E‐cadherin. Support or Funding Information BC Lung Association