CDC25‐dependent induction of inositol 1,4,5‐trisphosphate and diacylglycerol in Saccharomyces cerevisiae by nitrogen

Abstract
The addition of ammonium sulfate to starved yeast cells leads to a 3‐ to 4‐fold rapid increase of the second messengers inositol 1,4,5‐trisphosphate (IP3) and diacylglycerol (DAG), the products of phosphoinositide‐specific phospholipase C (PI‐PLC). This response is reduced by dissecting the RAS‐activating Cdc25 protein, and is completely abolished by the cdc25‐1 mutation even at permissive temperature. Starved cdc25‐1 mutant cells have a strongly reduced IP3 content, but an at least 10‐fold increased DAG level compared to the isogenic wild‐type strain. NH4 does not stimulate cAMP synthesis, and glucose does not induce IP3 and DAG. Our data suggest that the Cdc25 protein controls a nitrogen‐specific signalling pathway involving the effector PI‐PLC, in addition to the glucose‐induced activation of adenylyl cyclase (AC).