Essential for synthesis of DNA and RNA and for cell growth, purine biosynthesis is facilitated by the reversible assembly of the purinosome, a large enzyme complex regulated by casein kinase 2. Despite their integral role in cell behavior, it is not known how G protein-coupled receptors (GPCRs) contribute to purine biosynthesis. Now, using a cell-based dynamic mass redistribution (DMR) assay that measures redistribution of cellular material, Benkovic, Fang and colleagues have shown that Gi-coupled receptors have a role in regulating purinosome assembly. Assaying in HeLa cells, the authors screened 113 GPCR agonists for their ability to modulate small molecule–induced effects on purinosome assembly. Five adrenergic receptor agonists had an effect, and further characterization of their activity revealed that α2A-AR, but not β2-AR, is the receptor involved. Furthermore, purinosome assembly stimulated by α2A-AR is mediated by Gαi activation, as inhibiting Gαi with pertussis toxin (PTX) blocked the effects of the α-AR agonist oxymetazoline. The ability of Gαi to mediate purinosome assembly extends beyond adrenergic receptors, as P2Y, LPA and prostaglandin receptor agonists all promoted purinosome formation in a PTX-sensitive fashion. Although many of the other proteins involved remain to be determined, the authors conclude that Gαi mediates a GPCR-driven pathway regulating purine biosynthesis, and GPCRs may represent a new class of targets for inhibiting this process. (Nat. Chem. Biol. 7, 909–915, 2011)