Connexin 43 expression is downregulated in raft cultures of human keratinocytes expressing the human papillomavirus type 16 E5 protein

A decrease in gap junction-mediated cell-to-cell communication has previously been observed in monolayer cultures of human keratinocytes (HaCaT cells) expressing the human papillomavirus type 16 E5 (HPV 16 E5) gene and attributed to the reduced phosphorylation of connexin 43, the most abundant connexin in HaCaT cells. In line with this observation, we have now analyzed the effect of HPV 16 E5 on connexin 43 expression in raft cultures produced by transfected HaCaT cells. These keratinocytes transcribe HPV 16 E5 under the control of a dexamethasone-inducible promoter. Our results show that treatment with dexamethasone leads to an almost complete disappearance of connexin 43 in rafts expressing the E5 gene but not in control rafts. In our study we discuss the possible effects of this downregulation on cell-cell communication and cellular malignant transformation.