The cAMP-responsive element binding protein (CREB) transcription factor regulates furin expression during human trophoblast syncytialization

Introduction: The multinucleated syncytiotrophoblast is formed and maintained by cytotrophoblast cell fusion and serves multiple functions to ensure a successful pregnancy. We have previously reported that the proprotein convertase furin is required for trophoblast syncytialization by processing type 1 insulin-like growth factor receptor (IGF1R). Methods: Utilizing trophoblast cell fusion models including induced fusion of choriocarcinoma BeWo cells and spontaneous fusion of primary cultured term cytotrophoblast cells, the expression of furin was evaluated by quantitative real-time PCR, Western blotting and immunofluorescence. The key transcription factor regulating the FUR gene promoter and critical responsive elements were identified by luciferase reporter assays, truncated mutants analysis, site-directed mutagenesis and ChIP. Results: We demonstrated that the levels of FUR mRNA were significantly stimulated by cAMP/PKA signaling pathway during spontaneous fusion of cytotrophoblast cells and forskolin-induced fusion of BeWo cells, cAMP-responsive element binding protein (CREB) was proven to be the key transcription factor which regulated the FUR P1 promoter during forskolin-induced BeWo cell fusion, and two critical cAMP-responsive elements (CREs) in the P1 promoter were further identified. Finally, we showed that CREB mediated endogenous furin activation and that CREB siRNA attenuated forskolin-induced furin expression and cell fusion in BeWo cells. Discussion: This provides the first evidence of the upstream regulator of furin during trophoblast cell fusion. Conclusions: The above results suggest that the FUR transcription is activated by CREB-dependent stimulation of the FUR P1 promoter during human trophoblast syncytialization. (C) 2014 Elsevier Ltd. All rights reserved.