title: Basal activity of GIRK5 isoforms.
abstract: G protein-coupled inwardly rectifying K(+) channels (GIRK or Kir3) form functional heterotetramers gated by Gbetagamma subunits. GIRK channels are critical for functions as diverse as heart rate modulation and neuronal post-synaptic inhibition. GIRK5 (Kir3.5) is the oocyte homologue of the mammalian GIRK subunits that conform the K(ACh) channel. It has been claimed that even when the oocytes express GIRK5 proteins they do not form functional channels. However, the GIRK5 gene shows three initiation sites that suggest the existence of three isoforms. In a previous work we demonstrated the functionality of homomultimers of the shortest isoform overexpressed in the own oocytes. Remarkably, the basal GIRK5-Delta25 inward currents were not coupled to the activation of a G-protein receptor in the oocytes. These results encouraged us to study this channel in another expression system. In this work we show that Sf21 insect cells can be successfully transfected with this channel. GIRK5-Delta25 homomultimers produce time-dependent inward currents only with GTPgammaS in the recording pipette. Therefore, alternative modes of stimulus input to heterotrimeric G-proteins should be present in the oocytes to account for these results.
authors.affiliation: Departamento de Fisiologi;a, Facultad de Medicina, UNAM, Apartado Postal 70-250, D.F., 04510, Mexico.
authors.forename: Carolina
authors.initials: C
authors.lastname: Salvador
authors.forename: Silvia I
authors.initials: SI
authors.lastname: Mora
authors.forename: Benito
authors.initials: B
authors.lastname: Ordaz
authors.forename: Anaid
authors.initials: A
authors.lastname: Antaramian
authors.forename: Luis
authors.initials: L
authors.lastname: Vaca
authors.forename: Laura I
authors.initials: LI
authors.lastname: Escobar
mesh_terms: D000818:Animals; D016367:Baculoviridae / Q000378:metabolism; D002460:Cell Line; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007313:Insecta / Q000378:metabolism*; D007536:Isomerism; D009865:Oocytes / Q000378:metabolism; D018408:Patch-Clamp Techniques; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D024661:Potassium Channels, Inwardly Rectifying; D012313:RNA; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018411:Spodoptera / Q000378:metabolism
chemical_list: D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D015221:Potassium Channels; D024661:Potassium Channels, Inwardly Rectifying; C034477:RNA primers; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D012313:RNA