The Identification of Girk Channel Domains that Facilitate Rapid and Efficient Coupling to G Protein- Coupled Receptors

Abstract

G protein-gated inwardly rectifying potassium (GIRK or Kir3) channels constitute one subfamily of potassium-selective ion channels that regulate neuronal activity and heart rate. GIRK channels have been implicated in many biological processes, including pain perception, learning and memory, food intake, and reward. Structurally, GIRK channels consist of 4 subunits, able to form homotetramers or heterotetramers within the cell membrane. Activation of these channels occurs through a signal transduction cascade originating from ligandstimulated G-protein coupled receptors (GPCRs). This results in hyperpolarization of the cell membrane. With the variety of biological processes GIRK channels are involved in, understanding the interaction of the GPCR signaling cascade with GIRK channels could provide a beneficial therapeutic target. Using a variety of molecular biology techniques, I synthesized various chimeric proteins to investigate the GIRK channel and GPCR relationship, specifically focusing on amino acid residues promoting the coupling of GIRK1 with the GABAB receptor. Functional and biochemical assays in native systems suggest the Cterminal region and pore residue of the GIRK1 subunit are necessary to mediate a large receptor-induced response from the GIRK channel. Investigating this phenomenon further can determine how the identified GIRK1 channel domains are mediating efficient GABAB receptor coupling.