LAUSR

Significance G protein–coupled receptor (GPCR) signaling is the most prevalent signaling motif in cells. The basic pathway consists of a GPCR molecule that, once stimulated, goes on to activate a G protein, which in turn typically activates an effector enzyme to produce a cellular function. One long-standing concept about GPCR signaling, originating from a study in rod phototransduction turned into textbook dogma, is high amplification; namely, a large number of downstream G protein molecules are activated by one GPCR molecule. Our findings here from mammalian olfactory transduction now indicate that this amplification is less than unity even for a well-matched odorant/receptor complex. Thus, rod phototransduction is possibly unusual and not necessarily representative of ligand-triggered GPCR signaling generally.