title: PKC inhibition results in a Kv 1.5 + Kv β1.3 pharmacology closer to Kv 1.5 channels.
abstract: OBJECTIVE
  The Kv β1.3 subunit modifies the gating and pharmacology of Kv 1.5 channels in a PKC-dependent manner, decreasing channel sensitivity to bupivacaine- and quinidine-mediated blockade. Cardiac Kv 1.5 channels associate with receptor for activated C kinase 1 (RACK1), the Kv β1.3 subunit and different PKC isoforms, resulting in the formation of a functional channelosome. The aim of the present study was to investigate the effects of PKC inhibition on bupivacaine and quinidine block of Kv 1.5 + Kv β1.3 channels.
  
  
  METHODS
  HEK293 cells were transfected with Kv 1.5 + Kv β1.3 channels, and currents were recorded using the whole-cell configuration of the patch-clamp technique. PKC inhibition was achieved by incubating the cells with either calphostin C or bisindolylmaleimide II and the effects of bupivacaine and quinidine were analysed.
  
  
  RESULTS
  The voltage-dependent inactivation of Kv 1.5 + Kv β1.3 channels and their pharmacological behaviour after PKC inhibition with calphostin C were similar to those displayed by Kv 1.5 channels alone. Indeed, the IC50 values for bupivacaine were similar in cells whose PKC was inhibited with calphostin C or bisindolylmaleimide II. Similar results were also observed in the presence of quinidine.
  
  
  CONCLUSIONS
  The finding that the voltage-dependence of inactivation and the pharmacology of Kv 1.5 + Kv β1.3 channels after PKC inhibition resembled that observed in Kv 1.5 channels suggests that both processes are dependent on PKC-mediated phosphorylation. These results may have clinical relevance in diseases that are characterized by alterations in kinase activity.
authors.affiliation: Modelos Experimentales Enfermedades Humanas, Instituto de Investigaciones Biomédicas 'Alberto Sols' (CSIC-UAM), Madrid, Spain.
authors.forename: A
authors.initials: A
authors.lastname: Macías
authors.forename: A
authors.initials: A
authors.lastname: de la Cruz
authors.forename: A
authors.initials: A
authors.lastname: Prieto
authors.forename: D A
authors.initials: DA
authors.lastname: Peraza
authors.forename: M M
authors.initials: MM
authors.lastname: Tamkun
authors.forename: T
authors.initials: T
authors.lastname: González
authors.forename: C
authors.initials: C
authors.lastname: Valenzuela
mesh_terms: D057809:HEK293 Cells; D006801:Humans; D007211:Indoles / Q000494:pharmacology; D051664:Kv1.3 Potassium Channel / Q000502:physiology*; D051666:Kv1.5 Potassium Channel / Q000502:physiology*; D008301:Maleimides / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors* / Q000502:physiology
chemical_list: D007211:Indoles; C496981:KCNA5 protein, human; C097044:KCNAB1 protein, human; D051664:Kv1.3 Potassium Channel; D051666:Kv1.5 Potassium Channel; D008301:Maleimides; D009281:Naphthalenes; C116174:bisindolylmaleimide II; D011493:Protein Kinase C; C058819:calphostin C