Phosphorylation of the lipid droplet localized glycerol‑3‑phosphate acyltransferase Gpt2 prevents a futile triacylglycerol cycle in yeast

Publication date: Available online 14 August 2019Source: Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of LipidsAuthor(s): Bernadette Kiegerl, Marjan Tavassoli, Heather Smart, Brittney N. Shabits, Vanina Zaremberg, Karin AthenstaedtAbstractThe proteome of lipid droplets, storage compartments of triacylglycerols (TAGs), comprises TAG synthesizing and TAG degrading enzymes. Thus, to prevent a futile cycle the activity of enzymes catalyzing key steps in TAG turnover has to be strictly coordinated. The first and committed reaction of TAG synthesis is catalyzed by a glycerol‑3‑phosphate acyltransferase (GPAT). Here we demonstrate that in the model organism yeast the lipid droplet associated GPAT Gpt2 requires phosphorylation at a conserved motif to prevent a futile TAG cycle. Phosphorylation deficiency at the conserved motif increases the enzyme activity of Gpt2 and consequently enhances TAG synthesis. In proliferating cells the phosphorylation deficient GPAT-form contributes to TAG metabolism similar to control. However, during lipolysis the increased activity of phosphorylation deficient Gpt2 causes a constant TAG level by using TAG-released fatty acids as substrate for TAG synthesis. These data strongly indicate that phosphorylation of Gpt2 at a conserved motif plays a critical role in coordinating the synthesis and degradation of TAGs.Graphical abstract
Source: Biochimica et Biophysica Acta (BBA) Molecular and Cell Biology of Lipids - Category: Lipidology Source Type: research