Desmoglein 3 (Dsg3) is a member of desmoglein subfamily and contributes to cell-cell adhesion in desmosomes. It was first characterized as an autoantigen in pemphigus vulgaris, an autoimmune blistering disease preferentially manifested in oral mucosa. Our recent study suggests that Dsg3 has a role beyond desmosome adhesion, being associated with E-cadherin in regulating intercellular junction assembly. To gain insight of Dsg3, here we adopted different methodologies to address the expression and distribution of Dsg3 and its relation with E-cadherin.
Methods:
The intercellular junction proteins are distributed in two distinct subcellular pools in epithelial cells, Trition X-100 soluble and insoluble fractions, the latter of which is associated with cytoskeleton. First, we analysed the protein solubility of Dsg3 and E-cadherin in HaCaT keratinocytes in response to a calcium switch by western blotting. Then, we determined whether up- or down-regulation of Dsg3 affects distribution of E-cadherin in cells.
Results:
We showed that Dsg3 expression was calcium-dependent and increased dramatically upon a calcium switch. It was predominantly present in Triton insoluble fraction. In contrast, E-cadherin remained consistent and was enriched in Triton soluble fraction. Its expression however was dependent on the status of cell confluence and appeared to be increased when the cells grew from sub-confluence to confluence (two-fold increase). Over-expression of Dsg3 in A431 cells suppressed E-cadherin expression, particularly in Triton insoluble fraction. On the other hand, knockdown of Dsg3 had no effect on overall E-cadherin levels but instead resulted in disruption of intercellular junction and flattened cells.
Conclusions:
These findings suggest that Dsg3 plays a role in regulating protein distribution and stability of E-cadherin that has implication for understanding the pathogenesis of pemphigus.