The cyclic AMP (cAMP) signalling pathways play a crucial role in the development and chemotaxis of the amoeba Dictyostelium discoideum. The cAMP-activated RasC–TORC2–PKB module controls cell polarisation and chemotaxis. TORC2-dependent adenylyl cyclase A (ACA) activity also stimulates cAMP accumulation and developmental gene expression. However, the picture of cAMP signalling in Dictyostelium is still far from complete. In this issue on page 551, Salvatore Bozzaro and colleagues set out to identify new components involved in the cAMP signalling networks through an insertional mutagenesis screen. Mutations in the TORC2 subunit Pia cause impaired chemotaxis and development, and the authors identify suppressor mutants that restore these activities in the amoeba. The authors show that whereas cell polarity and chemotaxis are rescued in these mutants, Pia-dependent ACA stimulation is bypassed in a manner dependent on adenylyl cyclase B (ACB). They demonstrate that one identified gene encodes the putative HECT ubiquitin ligase HectPH1, which is homologous to mammalian HERC1. A gene knockout for hectPH1 in the Pia mutant also displays the rescue phenotype from the screen – including the bypass of TORC2 and ACA signalling – and is reversed by expression of the isolated HECT domain. Taken together, these data identify a potential new ubiquitin ligase in Dictyostelium that regulates cAMP signalling sensitivity in the cell.
- © 2017. Published by The Company of Biologists Ltd