Low to high Ca2+-switch causes phosphorylation and association of desmocollin 3 with plakoglobin and desmoglein 3 in cultured keratinocytes

Although desmocollins (Dscs) and desmogleins (Dsgs) are known to be bound to each other to form desmosomes, neither their interactions nor regulations that occur in human keratinocytes grown in low and high Ca(2+)medium has been determined. In this study, we investigated whether Dsc3 interacts with Dsg3 in a cell line of human squamous cell carcinoma keratinocytes (DJM-1) grown in low (0.05 mm) or high (1.27 mm) Ca(2+)medium. Anti-Dsc3 monoclonal antibody did not co-immunoprecipitate Dsg3 nor plakoglobin with Dsc3 in low Ca(2+)culture, whereas it co-immunoprecipitated plakoglobin already at 10 min and Dsg3 at 60 min after Ca2+-switch in association with Dsc3 phosphorylation at serine residues. These results suggest that both the binding of Dsc3 to plakoglobin and Dsc3 phosphorylation are involved in Dsc3 binding to Dsg3 during Ca2+-induced desmosome assembly.