Glycerol-3-phosphate acyltransferase (GPAT) initiates the synthesis of triacylglycerol and phospholipids and, in the process, regulates the formation of several lipid metabolites known to be intracellular signaling molecules. The recent identification of a new GPAT isoform (Cao et al., 2006) suggests a role for GPAT isoforms in nutrient-mediated signaling.