title: A novel cyclic AMP/Epac1/CaMKI signaling cascade promotes GCM1 desumoylation and placental cell fusion.
abstract: Cyclic AMP (cAMP) signaling and the placental transcription factor glial cell missing 1 (GCM1) regulate expression of syncytin-1 and -2 fusogenic proteins, which are critical for syncytiotrophoblast formation by trophoblast fusion. We recently revealed a cAMP/protein kinase A (PKA)/CBP signaling pathway that activates GCM1 by coordinating GCM1 phosphorylation and acetylation. In contrast, GCM1 activity is downregulated by sumoylation of Lys156. How GCM1 sumoylation is regulated was unknown. Here, we identify a novel PKA-independent cAMP signaling pathway as the critical regulator of GCM1 sumoylation. We show that Epac1 and Rap1, in response to cAMP, activate CaMKI to phosphorylate Ser47 in GCM1. This phosphorylation facilitates the interaction between GCM1 and the desumoylating enzyme SENP1 and thereby leads to GCM1 desumoylation and activation. Using RNA interference (RNAi), we further demonstrate that 8-(4-chlorophenylthio)-2'-O-Me-cAMP-AM (8-CPT-AM), an Epac activator, stimulates syncytin-1 and -2 gene expression and cell fusion of placental BeWo cells in a GCM1-dependent manner. Importantly, the cell fusion defect in GCM1-knockdown BeWo cells can be reversed and enhanced by the RNAi-resistant phosphomimetic GCM1(S47D) mutant. Our study has identified a novel cAMP/Epac1/CaMKI/GCM1 signaling cascade that stimulates trophoblast fusion through promoting GCM1 phosphorylation and desumoylation.
authors.affiliation: Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan.
authors.forename: Ching-Wen
authors.initials: CW
authors.lastname: Chang
authors.forename: Geen-Dong
authors.initials: GD
authors.lastname: Chang
authors.forename: Hungwen
authors.initials: H
authors.lastname: Chen
mesh_terms: D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1 / Q000378:metabolism*; D002459:Cell Fusion; D002460:Cell Line; D000242:Cyclic AMP / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D004268:DNA-Binding Proteins; D005260:Female; D015686:Gene Products, env / Q000096:biosynthesis / Q000235:genetics; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism*; D010766:Phosphorylation; D010920:Placenta; D011247:Pregnancy; D011257:Pregnancy Proteins / Q000096:biosynthesis / Q000235:genetics; D034622:RNA Interference; D034741:RNA, Small Interfering; D015398:Signal Transduction; D058207:Sumoylation; D013873:Thionucleotides / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism*; D014327:Trophoblasts / Q000378:metabolism
chemical_list: C488718:2'-O-methyl-8-(4-chlorophenylthio)cAMP; D004268:DNA-Binding Proteins; C518353:ERVFRD-1 protein, human; C491089:GCM1 protein, human; D015686:Gene Products, env; D020662:Guanine Nucleotide Exchange Factors; D009687:Nuclear Proteins; D011257:Pregnancy Proteins; C116122:RAPGEF3 protein, human; D034741:RNA, Small Interfering; D013873:Thionucleotides; D014157:Transcription Factors; C405335:syncytin; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; C517596:CAMK1 protein, human; D054729:Calcium-Calmodulin-Dependent Protein Kinase Type 1