R7BP: a surprising new link between G proteins, RGS proteins, and nuclear signaling in the brain.

The regulators of G protein signaling (RGS proteins) bind directly to G protein alpha (Galpha) subunits in brain and other tissues to determine the strength, duration, and fidelity of neurotransmitter receptor signaling. A recent study shows, quite unexpectedly, that one class of RGS proteins [the R7 subfamily bound to Gbeta(5) (R7-Gbeta(5))] shuttles between the plasma membrane and the nucleus with assistance from a novel shuttle protein, R7BP. R7BP binds directly to R7-Gbeta(5) and the protein complex is tethered to the plasma membrane by addition of a lipid, palmitate, on R7BP. Removal of palmitate results in the translocation of the R7BP-R7-Gbeta(5) complex to the nucleus, presumably for nontraditional signaling functions. These findings suggest an entirely novel mechanism for regulating neurotransmitter signaling. That is, R7BP transduces signals directly from receptors and G proteins at the plasma membrane to the nucleus, and this plasma membrane-nuclear shuttling is controlled by reversible palmitoylation of R7BP.