title: Differential regulation of RhoA-mediated signaling by the TPalpha and TPbeta isoforms of the human thromboxane A2 receptor: independent modulation of TPalpha signaling by prostacyclin and nitric oxide.
abstract: In humans, thromboxane (TX) A(2) signals through the TPalpha and TPbeta isoforms of the TXA(2) receptor that exhibit common and distinct roles. For example, Gq/phospholipase (PL)Cbeta signaling by TPalpha is directly inhibited by the vasodilators prostacyclin and nitric oxide (NO) whereas that signaling by TPbeta is unaffected. Herein, we investigated whether TPalpha and/or TPbeta regulate G(12)/Rho activation and whether that signaling might be differentially regulated by prostacyclin and/or NO. Both TPalpha and TPbeta independently regulated RhoA activation and signaling in clonal cells over-expressing TPalpha or TPbeta and in primary human aortic smooth muscle cells (1 degrees AoSMCs). While RhoA-signaling by TPalpha was directly impaired by prostacyclin and NO through protein kinase (PK)A- and PKG-dependent phosphorylation, respectively, signaling by TPbeta was not directly affected by either agent. Collectively, while TPalpha and TPbeta contribute to RhoA activation, our findings support the hypothesis that TPalpha is involved in the dynamic regulation of haemostasis and vascular tone, such as in response to prostacyclin and NO. Conversely, the role of TPbeta in such processes remains unsolved. Data herein provide essential new insights into the physiologic roles of TPalpha and TPbeta and, through studies in AoSMCs, reveal an additional mode of regulation of VSM contractile responses by TXA(2).
authors.affiliation: UCD School of Biomolecular and Biomedical Science, UCD Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Katarina
authors.initials: K
authors.lastname: Wikström
authors.forename: David J
authors.initials: DJ
authors.lastname: Kavanagh
authors.forename: Helen M
authors.initials: HM
authors.lastname: Reid
authors.forename: B Therese
authors.initials: BT
authors.lastname: Kinsella
mesh_terms: D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D011464:Epoprostenol / Q000031:analogs & derivatives* / Q000494:pharmacology; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000378:metabolism; D043802:GTP-Binding Protein alpha Subunits, Gq-G11 / Q000378:metabolism; D006801:Humans; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D054799:Phospholipase C beta / Q000378:metabolism; D020033:Protein Isoforms / Q000502:physiology; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000502:physiology*; D015398:Signal Transduction; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D009569:Nitric Oxide; D011464:Epoprostenol; D000242:Cyclic AMP; D054799:Phospholipase C beta; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D043802:GTP-Binding Protein alpha Subunits, Gq-G11; D020742:rhoA GTP-Binding Protein; D006152:Cyclic GMP; C043867:cicaprost