title: Serotonin induces Rho/ROCK-dependent activation of Smads 1/5/8 in pulmonary artery smooth muscle cells.
abstract: Serotonin (5-HT) stimulates pulmonary artery smooth muscle cell proliferation and has been associated with pulmonary arterial hypertension (PAH). Bone morphogenetic protein receptor 2 (BMPR2) mutations similarly have been linked to PAH. However, possible crosstalk between 5-HT and BMPR signaling remains poorly characterized. We report here that 5-HT activates Smads 1/5/8 in bovine and human pulmonary artery smooth muscle cells (SMCs) and causes translocation of these Smads from cytoplasm to the nucleus. DN BMPR1A blocked 5-HT activation of Smads 1/5/8 by 5-HT and BMPR1A overexpression enhanced it. Activation of Smads by 5-HT occurred through the 5-HT 1B/1D receptor as it was blocked with the inhibitor GR 55562 but unaffected by inhibitors of the 5-HT transporter and a variety of 5-HT receptors. Activation of the Smads by 5-HT depended on Rho/Rho kinase signaling as it was blocked by Y27632, but unaffected by inhibitors of PI3K or MAPK. Transfection of cells with BMPR1A and ligation of the BMP receptor with BMP-2 also activated GTP-Rho A of these SMCs, while DN BMPR1A blocked the activation. 5-HT stimulated an increase in serine/threonine phosphorylation of BMPR1A, supporting the activation of BMPR1A by 5-HT in SMCs. Infusion of 5-HT into mice with miniosmotic infusion pumps caused activation of Smads 1/5/8 in lung tissue, demonstrating the effect in vivo. The studies support a unique concept that 5-HT transactivates the serine kinase receptor, BMPR 1A, to activate Smads 1/5/8 via Rho and Rho kinase in pulmonary artery SMCs. Rho and Rho kinase also participate in the activation of Smads by BMP.
authors.affiliation: Tufts Medical Center, Pulmonary, Critical Care, and Sleep Division, Tupper Research Institute, 750 Washington Street, Boston, MA 02111, USA.
authors.forename: Yinglin
authors.initials: Y
authors.lastname: Liu
authors.forename: Wenying
authors.initials: W
authors.lastname: Ren
authors.forename: Rod
authors.initials: R
authors.lastname: Warburton
authors.forename: Deniz
authors.initials: D
authors.lastname: Toksoz
authors.forename: Barry L
authors.initials: BL
authors.lastname: Fanburg
mesh_terms: D000818:Animals; D052005:Bone Morphogenetic Protein Receptors, Type I / Q000235:genetics* / Q000378:metabolism; D002417:Cattle; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D009131:Muscle, Smooth, Vascular / Q000166:cytology; D032389:Myocytes, Smooth Muscle / Q000166:cytology*; D011651:Pulmonary Artery / Q000166:cytology*; D012701:Serotonin / Q000494:pharmacology*; D051896:Smad Proteins, Receptor-Regulated / Q000378:metabolism*; D051898:Smad1 Protein / Q000378:metabolism; D051902:Smad5 Protein / Q000378:metabolism; D051904:Smad8 Protein / Q000378:metabolism; D015533:Transcriptional Activation; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases / Q000378:metabolism*
chemical_list: D051896:Smad Proteins, Receptor-Regulated; D051898:Smad1 Protein; D051902:Smad5 Protein; D051904:Smad8 Protein; D012701:Serotonin; D054460:rho-Associated Kinases; D052005:Bone Morphogenetic Protein Receptors, Type I; D020741:rho GTP-Binding Proteins