G protein gated inward rectifier K+ (GIRK) channels open and thereby silence cellular electrical activity when inhibitory G protein coupled receptors (GPCRs) are stimulated. Here we describe an assay to measure neuronal GIRK2 activity as a function of membrane-anchored G protein concentration. Using this assay we show that four Gβɣ subunits bind cooperatively to open GIRK2, and that intracellular Na+ – which enters neurons during action potentials – further amplifies opening mostly by increasing Gβɣ affinity. A Na+ amplification function is characterized and used to estimate the concentration of Gβɣ subunits that appear in the membrane of mouse dopamine neurons when GABAB receptors are stimulated. We conclude that GIRK2, through its dual responsiveness to Gβɣ and Na+, mediates a form of neuronal inhibition that is amplifiable in the setting of excess electrical activity.
ASJC Scopus subject areas
- Immunology and Microbiology(all)
- Biochemistry, Genetics and Molecular Biology(all)