Abstract
G protein-coupled receptors (GPCRs) transduce their signals through trimeric G proteins, inducing guanine nucleotide exchange on their Galpha-subunits; the resulting Galpha-GTP transmits the signal further inside the cell. GoLoco domains present in many proteins play important roles in multiple trimeric G protein-dependent activities, physically binding Galpha-subunits of the Galpha(i/o) class. In most cases GoLoco binds exclusively to the GDP-loaded form of the Galpha-subunits. Here we demonstrate that the poly-GoLoco-containing protein Pins of Drosophila can bind to both GDP- and GTP-forms of Drosophila Galpha(o). We identify Pins GoLoco domain 1 as necessary and sufficient for this unusual interaction with Galpha(o)-GTP. We further pinpoint a lysine residue located centrally in this domain as necessary for the interaction. Our studies thus identify Drosophila Pins as a target of Galpha(o)-mediated GPCR receptor signaling, e.g., in the context of the nervous system development, where Galpha(o) acts downstream from Frizzled and redundantly with Galpha(i) to control the asymmetry of cell divisions.