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

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