FWF-Regulation der PA Biosynthese - Regulatory aspects of phosphatidic acid biosynthesis in yeast

Regulatory aspects of phosphatidic acid biosynthesis in yeast Phosphatidic acid (PA) holds a pivotal role in cell metabolism, because on one hand it is the key intermediate for the formation of all glycerophospholipids (membrane lipids) and triacylglycerols (storage lipids), and on the other hand involved in cell signaling. Due to these fundamental functions it is important that the cellular PA pool is adjusted to cellular demands. In all eukaryotic organisms enzymes mediating the reactions of PA biosynthesis occur in redundancy. Several differences in the properties of these isoenzymes have been observed. However, our current knowledge about mechanisms regulating the activity of these enzymes, and hence de novo synthesis of PA, is still limited. The aim of the proposed project is to elucidate the regulation of PA biosynthesis by focusing on glycerol-3-phosphate acyltransferases (GPATs), because these enzymes catalyze the first and rate limiting reaction in PA biosynthesis, and represent the main target of regulation. For these studies we will use as experimental system the budding yeast Saccharomyces cerevisiae, which has been proven to be an invaluable model organism to determine the principles of lipid metabolic processes. In this microorganism two GPATs exist, namely Gat1p (Gpt2p) and Gat2p (Sct1p), which are both target of protein-kinases. By using molecular biological, cell biological and biochemical methods the following questions will be addressed: (i) Is the transcription and/or the phosphorylation of GPATs linked to the cell cycle? (ii) Does phosphorylation of GPATs change their activity, stability and/or subcellular localization? (iii) Is the contribution of GPATs to PA biosynthesis regulated by interaction with other proteins? (iv) Are GPATs regulated by feedback mechanism(s)? And finally, (v) is the dual localization of Gat1p to lipid droplets and the endoplasmic reticulum required to regulate its contribution to PA biosynthesis? Since PA biosynthesis via GPATs is like many cell metabolic processes highly conserved from yeast to human, our results obtained with Saccharomyces cerevisiae will provide the basis for similar studies in higher eukaryotes.