title: Cell type influences the molecular mechanisms involved in hormonal regulation of ERG K+ channels.
abstract: While the thyrotropin-releasing hormone (TRH) effect of raising intracellular Ca(2+) levels has been shown to rely on G(q/11) and PLC activation, the molecular mechanisms involved in the regulation of ERG K(+) channels by TRH are still partially unknown. We have analysed the effects of βγ scavengers, Akt/PKB inactivation, and TRH receptor (TRH-R) overexpression on such regulation in native and heterologous expression cell systems. In native rat pituitary GH(3) cells β-ARK/CT, Gα(t), and phosducin significantly reduced TRH inhibition of rERG currents, whereas in HEK-H36/T1 cells permanently expressing TRH-R and hERG, neither of the βγ scavengers affected the TRH-induced shift in V                         (1/2). Use of specific siRNAs to knock Akt/PKB expression down abolished the TRH effect on HEK-H36/T1 cell hERG, but not on rERG from GH(3) cells. Indeed, wortmannin or long insulin pretreatment also blocked TRH regulation of ERG currents in HEK-H36/T1 but not in GH(3) cells. To determine whether these differences could be related to the amount of TRH-Rs in the cell, we studied the TRH concentration dependence of the Ca(2+) and ERG responses in GH(3) cells overexpressing the receptors. The data indicated that independent of the receptor number additional cellular factor(s) contribute differently to couple the TRH-R to hERG channel modulation in HEK-H36/T1 cells. We conclude that regulation of ERG currents by TRH and its receptor is transduced in GH(3) and HEK-H36/T1 cell systems through common and different elements, and hence that the cell type influences the signalling pathways involved in the TRH-evoked responses.
authors.affiliation: Departamento de Bioquímica y Biología Molecular, Edificio Santiago Gascón, Campus del Cristo, Universidad de Oviedo, 33006, Oviedo, Spain.
authors.forename: Luis
authors.initials: L
authors.lastname: Carretero
authors.forename: Francisco
authors.initials: F
authors.lastname: Barros
authors.forename: Pablo
authors.initials: P
authors.lastname: Miranda
authors.forename: Jorge
authors.initials: J
authors.lastname: Fernández-Trillo
authors.forename: Angeles
authors.initials: A
authors.lastname: Machín
authors.forename: Pilar
authors.initials: P
authors.lastname: de la Peña
authors.forename: Pedro
authors.initials: P
authors.lastname: Domínguez
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D051638:Ether-A-Go-Go Potassium Channels / Q000037:antagonists & inhibitors / Q000378:metabolism*; D044387:GTP-Binding Protein beta Subunits / Q000378:metabolism; D044388:GTP-Binding Protein gamma Subunits / Q000378:metabolism; D006801:Humans; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D018025:Receptors, Thyrotropin-Releasing Hormone / Q000378:metabolism; D015398:Signal Transduction; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism*
chemical_list: D051638:Ether-A-Go-Go Potassium Channels; C118981:G-protein Beta gamma; D044387:GTP-Binding Protein beta Subunits; D044388:GTP-Binding Protein gamma Subunits; D018025:Receptors, Thyrotropin-Releasing Hormone; D013973:Thyrotropin-Releasing Hormone; D064413:3-Phosphoinositide-Dependent Protein Kinases; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D002118:Calcium