Novel phosphatidylinositol phosphate kinases with a G-protein coupled receptor signature are shared by Dictyostelium and Phytophthora

G-protein coupled receptors (GPCR) and phosphatidylinositol phosphate kinases (PIPK) are important key switches in signal transduction pathways. A novel class of proteins was identified in the genomes of two unrelated organisms that harbor both a GPCR and a PIPK domain. Dictyostelium discoideum contains one GPCR–PIPK, which is crucial in cell-density sensing, and the genomes of Phytophthora sojae and Phytophthora ramorum each encode twelve GPCR–PIPKs. Intriguingly, these are currently the only species that have these two domains combined in one protein. Here, the structural and regulatory characteristics of GPCR–PIPKs are presented and discussed. It is hypothesized that, upon activation, GPCR–PIPKs are able to trigger heterotrimeric G-protein signaling and phosphoinositide second-messenger synthesis.