title: Cooperation of Epac1/Rap1/Akt and PKA in prostaglandin E(2) -induced proliferation of human umbilical cord blood derived mesenchymal stem cells: involvement of c-Myc and VEGF expression.
abstract: Prostaglandin E(2) (PGE(2)) is well known to regulate cell functions through cAMP; however, the role of exchange protein directly activated by cAMP (Epac1) and protein kinase A (PKA) in modulating such functions is unknown in human umbilical cord blood-derived mesenchymal stem cells (hUCB-MSCs). Therefore, we investigated the relationship between Epac1 and PKA during PGE(2)-induced hUCB-MSC proliferation and its related signaling pathways. PGE(2) increased cell proliferation, and E-type prostaglandin (EP) 2 receptor mRNA expression level and activated cAMP generation, which were blocked by EP2 receptor selective antagonist AH 6809. PGE(2) increased Epac1 expression, Ras-related protein 1 (Rap1) activation level, and Akt phosphorylation, which were inhibited by AH 6809, adenylyl cyclase inhibitor SQ 22536, and Epac1/Rap1-specific siRNA. Also, PGE(2) increased PKA activity, which was inhibited by AH 6809, SQ 22536, and PKA inhibitor PKI. HUCB-MSCs were incubated with the Epac agonist 8-pCPT-cAMP or the PKA agonist 6-phe-cAMP to examine whether Epac1/Rap1/Akt activation was independent of PKA activation. 8-pCPT-cAMP increased Akt phosphorylation but not PKA activity. 6-Phe-cAMP increased PKA activity, but not Akt phosphorylation. Additionally, an Akt inhibitor or PKA inhibitor (PKI) did not block the PGE(2) -induced increase in PKA activity or Akt phosphorylation, respectively. Moreover, PGE(2) increased glycogen synthase kinase (GSK)-3β phosphorylation and nuclear translocation of active-β-catenin, which were inhibited by Akt inhibitor or/and PKI. PGE(2) increased c-Myc and vascular endothelial growth factor (VEGF) expression levels, which were blocked by β-catenin siRNA. In conclusion, PGE(2) stimulated hUCB-MSC proliferation through β-catenin-mediated c-Myc and VEGF expression via Epac/Rap1/Akt and PKA cooperation.
authors.affiliation: Department of Veterinary Physiology, College of Veterinary Medicine, Chonnam National University, Gwangju, Korea.
authors.forename: Min Woo
authors.initials: MW
authors.lastname: Jang
authors.forename: Seung Pil
authors.initials: SP
authors.lastname: Yun
authors.forename: Jae Hong
authors.initials: JH
authors.lastname: Park
authors.forename: Jung Min
authors.initials: JM
authors.lastname: Ryu
authors.forename: Jang Hern
authors.initials: JH
authors.lastname: Lee
authors.forename: Ho Jae
authors.initials: HJ
authors.lastname: Han
mesh_terms: D049109:Cell Proliferation / Q000187:drug effects; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology*; D005312:Fetal Blood / Q000166:cytology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism; D006801:Humans; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics / Q000378:metabolism*; D000089804:Shelterin Complex; D015398:Signal Transduction; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*
chemical_list: D020662:Guanine Nucleotide Exchange Factors; D016271:Proto-Oncogene Proteins c-myc; C116122:RAPGEF3 protein, human; D000089804:Shelterin Complex; C440809:TERF2IP protein, human; D034501:Telomere-Binding Proteins; D042461:Vascular Endothelial Growth Factor A; D051057:Proto-Oncogene Proteins c-akt; D017868:Cyclic AMP-Dependent Protein Kinases; D015232:Dinoprostone