Effects of TPA on dye transfer and dye leakage in fibroblasts transfected with a connexin 43 mutation at ser368.

In order to investigate the site of active phosphorylation under treatment with TPA, both wild type (WT) fibroblasts and fibroblasts from Cx43-knockout mice transfected with Cx43 mutated at ser368 were used to study the effects of TPA on dye leakage and gap junction assembly. Results showed that in control conditions with or without EGTA, no significant differences in dye leakage were observed between these two kinds of cells. However, under TPA treatment, non-leakage cases in the mutant cells were much less than those in WT cells. In the two types of reaggregated cells, there was a marked difference in the capacity for dye transfer. Dye transfer in WT cells was 4-fold stronger than in mutant cells. While under TPA treatment, the difference between WT and mutant cells was diminished suggesting that ser368 was probably the most important phosphorylation site under treatment with TPA.