Engineering of an artificial light-modulated potassium channel

PLoS One. 2012;7(8):e43766. doi: 10.1371/journal.pone.0043766. Epub 2012 Aug 22.

Abstract

Ion Channel-Coupled Receptors (ICCRs) are artificial receptor-channel fusion proteins designed to couple ligand binding to channel gating. We previously validated the ICCR concept with various G protein-coupled receptors (GPCRs) fused with the inward rectifying potassium channel Kir6.2. Here we characterize a novel ICCR, consisting of the light activated GPCR, opsin/rhodopsin, fused with Kir6.2. To validate our two-electrode voltage clamp (TEVC) assay for activation of the GPCR, we first co-expressed the apoprotein opsin and the G protein-activated potassium channel Kir3.1(F137S) (Kir3.1*) in Xenopus oocytes. Opsin can be converted to rhodopsin by incubation with 11-cis retinal and activated by light-induced retinal cis→trans isomerization. Alternatively opsin can be activated by incubation of oocytes with all-trans-retinal. We found that illumination of 11-cis-retinal-incubated oocytes co-expressing opsin and Kir3.1* caused an immediate and long-lasting channel opening. In the absence of 11-cis retinal, all-trans-retinal also opened the channel persistently, although with slower kinetics. We then used the oocyte/TEVC system to test fusion proteins between opsin/rhodopsin and Kir6.2. We demonstrate that a construct with a C-terminally truncated rhodopsin responds to light stimulus independent of G protein. By extending the concept of ICCRs to the light-activatable GPCR rhodopsin we broaden the potential applications of this set of tools.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels / genetics*
  • G Protein-Coupled Inwardly-Rectifying Potassium Channels / metabolism*
  • GTP-Binding Protein alpha Subunits, Gi-Go / genetics
  • Light*
  • Oocytes / metabolism
  • Potassium Channels, Inwardly Rectifying / genetics*
  • Potassium Channels, Inwardly Rectifying / metabolism
  • Protein Engineering / methods*
  • Recombinant Fusion Proteins / genetics*
  • Recombinant Fusion Proteins / metabolism
  • Rhodopsin / genetics
  • Xenopus laevis / genetics

Substances

  • G Protein-Coupled Inwardly-Rectifying Potassium Channels
  • Kir6.2 channel
  • Potassium Channels, Inwardly Rectifying
  • Recombinant Fusion Proteins
  • Rhodopsin
  • GTP-Binding Protein alpha Subunits, Gi-Go

Grants and funding

This work was supported by the Agence Nationale de la Recherche (ICCR project, grant ANR-09-PIRI-0010 to M.V.) and the Canada Excellence Research Chair program (to O.P.E.). The Vivaudou laboratory is a member of the French National Laboratory of Excellence « Ion Channel Science and Therapeutics » supported by a network grant from ANR. O.P.E. holds the Anne and Max Tanenbaum Chair in Neuroscience at the University of Toronto. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.