Local membrane charge regulates β 2 adrenergic receptor coupling to G i3 .

The β ₂ adrenergic receptor (β ₂ AR) signals through both G _s and G _i in cardiac myocytes, and the G _i pathway counteracts the G _s pathway. However, G _i coupling is much less efficient than G _s coupling in most cell-based and biochemical assays, making it difficult to study β ₂ AR-G _i interactions. Here we investigate the role of phospholipid composition on G _s and G _i coupling. While negatively charged phospholipids are known to enhance agonist affinity and stabilize an active state of the β ₂ AR, we find that they impair coupling to G _i3 and facilitate coupling to G _s . Positively charged Ca ²⁺ and Mg ²⁺ , known to interact with the negative charge on phospholipids, facilitates G _i3 coupling. Mutational analysis suggests that Ca ²⁺ coordinates an interaction between phospholipid and the negatively charged EDGE motif on the amino terminal helix of G _i3 . Taken together, our observations suggest that local membrane charge modulates the interaction between β ₂ AR and competing G protein subtypes.