Newly detected enzymes influence signaling lipids in eukaryotic cells

Polyphosphoinositides (PPIs) are signaling lipids in the membrane of eukaryotes, which play an important role in a variety of processes in the cell, from membrane trafficking, cytoskeleton organization, nuclear signaling to stress responses. In their work published on February 3 in PNAS (Doi: 10.1073/pnas.1324264111), IST Austria Professor Jiři Friml and PhD student Petra Nováková, together with colleagues at Ghent University, University of Amsterdam, and the Martin Luther University Halle-Wittenberg, identified a previously functionally uncharacterized group of enzymes, SAC2-SAC5, and show that they modify the levels of PPIs in their plant model, Arabidopsis thaliana. Their results suggest that SAC2-SAC5 are involved in the metabolization of PPIs in the tonoplast, the membrane surrounding a plant cell’s central vacuole. Both loss and overexpression of these enzymes leads to plant growth defects indicating disruptions in vacuole function. Analyzing the effects of gain- and loss-of-function of SAC2-SAC5 and PPIs on the cell, the researchers demonstrate that SAC2-SAC5 and PPIs play important roles in the morphology and function of plant vacuoles.