A docking site for G protein βγ subunits on the parathyroid hormone 1 receptor supports signaling through multiple pathways

The G protein-coupled receptor for PTH and PTH-related protein ( PTH1R) signals via many intracellular pathways. The purpose of this work is to investigate a G protein binding site on an intracellular domain of the PTH1R. The carboxy-terminal, cytoplasmic tail of the PTH1R fused to glutathione-S-transferase interacts with G(i/o) proteins in vitro. All three subunits of the heterotrimer interact with the receptor C-tail. Activation of the heterotrimeric complex with GTP gamma S has no effect on G beta gamma interactions, but markedly disrupts binding of the G alpha(i/o) subunits to the receptor tail, suggesting that direct G beta gamma binding indirectly links G alpha subunits to this region of the receptor. G beta gamma subunits alone bind the C-tail with an affinity that is comparable to the heterotrimeric G protein complex. G protein complexes consisting of G alpha(s)his(6)-beta(1)gamma(2) and G alpha(q)his(6)beta(1)gamma(2) also interact with the PTH1R tail in vitro. The G beta gamma interaction domain is located on the juxta-membrane region of the tail between amino acids 468 and 491. Mutations that disrupt G beta gamma interactions block PTH signaling via phospholipase C beta/ [ Ca2+](i) and MAPK and markedly reduce signaling via adenylyl cyclase/cAMP. Herein, we define a domain on the PTH1R that is capable of binding G protein heterotrimeric complexes via direct G beta gamma interactions.