Dr. Jon Friesen

Research Interests & Areas

In my laboratory we use modern molecular biological tools as well as classical biochemical techniques to study the structure and function of enzymes critical for the biosynthesis of phosphatidylcholine, a major phospholipid component of the eukaryotic cell membrane. Research focuses on the enzyme CTP:phosphocholine cytidylyltransferase (CT), a member of the CDP-choline pathway, which results in the biosynthesis of phosphatidylcholine (PC). PC is the major component of eukaryotic cell membranes and a precursor to vital components of signal transduction pathways such as diacylglycerol and phosphatidic acid. CT is rate-limiting for the CDP-choline pathway and extensively regulated at the cellular level. CT is present as both a soluble and membrane-associated form. In many cells, activation of CT occurs simultaneously with the translocation of the enzyme from a soluble form to membrane-associated form, while in vitro the soluble form of CT is activated by the addition of certain lipids. In addition to regulation via association with membranes, CT from mammals is extensively phosphorylated. The regulation of CT activity is central to a variety of cellular processes, including the cell cycle, cell death, and vesicular traffic.