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"Biophysical characterization of Protein-Lipid interactions"

Research in the Kooijman laboratory is currently divided into two distinct directions.

Lipid droplets (LDs) are intracellular organelles involved in many more processes than just energy metabolism and are important for numerous diseases such as diabetes and cancer. My lab is specifically interested in how cytosolic LD binding proteins recognize and bind to the lipid monolayer that surrounds the neutral lipid core of these organelles. For this work we use the human LD binding protein perilipin 3. The perilipin protein family (perilipin 1 through 5) are the most abundant LD binding proteins in mammalian cells and perilipins 3, 4, and 5 (and possibly 2) are able to cycle on and off the LD surface. Perilipins 2, 3, and 5 contain an amphipathic alpha-helix bundle domain in their C-terminus that is able to reversibly unfold (it's ternary structure) and cover portions of the droplet surface. The exact interactions responsible for this binding and its reversible nature are currently unknown. We use perilipin 3 [1,2] as model LD binding protein and use liquid drop tensiometry to study LD binding in a physiologically relevant model system. Additionally, we use 3T3-L1 derived adipocytes to study the intracellular localization of perilipin proteins and their mutants. This work involves a combination of lipid biophysics, molecular biology, and cell biology to answer an important problem in biology, i.e. how do cytosolic proteins specifically recognize the LD interface over all other lipid interfaces (bilayers) inside a cell.

Protein interactions are also crucial for membrane binding proteins. This work has received lots of interest in the past and hence much is known about how specific membrane proteins bind to and interact with lipid bilayers. However, there is still much that needs to be investigated. Lingering questions are why are there so many different chemical species of lipids in biological membranes, and how is specificity of binding achieved for specific membrane binding proteins. In order to shed light on this my lab as focused on the physicochemical characterization of signaling lipids containing phosphomonoester moieties (in their headgroup). Examples of such lipids are phosphatidic acid, the plant and parasite derivative of PA diacylglycerolpyrophosphate (DGPP), and the polyphosphoinositides. As the pKa of these lipids falls in the physiological pH range and their charge is sensitively influenced by their environment, gaining knowledge of exactly what influences the exact charge is crucial. My lab has pioneered the determination of the ionization properties of these lipids in complex lipid mixtures [3,4]. Current projects in the lab revolve around the lipid DGPP which is mainly found in plants, but also yeast, and Trypanosomes. The main technique employed is solid state 31P NMR coupled with a host of wet lipid chemistry work.

REU students have, in the past, worked on each of these two projects. You will be expected to work together with other undergraduate and graduate students in the lab, and if possible should see your work published in future publications.

1. Mona Mirheydari, Priya Putta, Elizabeth K Mann, Edgar E Kooijman, Interaction of Two Amphipathic α-Helix Bundle Proteins, ApoLp-III and ApoE 3, with the Oil–Aqueous Interface, J Phys Chem B, 125(18): 4746-4756 (2021) DOI: 10.1021/acs.jpcb.1c00271
2. Amber R Titus, Ellyse N Ridgway, Rebecca Douglas, Elena Sánchez Brenes, Elizabeth K Mann, Edgar E Kooijman, The C-Terminus of Perilipin 3 Shows Distinct Lipid Binding at Phospholipid-Oil-Aqueous Interfaces, Membranes, 11(4): 265 (2021) DOI: 10.3390/membranes11040265
3. Desmond Owusu Kwarteng, Priya Putta, Edgar E. Kooijman, Ionization properties of monophosphoinositides in mixed model membranes, BBA-Biomem, 1863(11): 183692 (2021) DOI: 10.1016/j.bbamem.2021.183692
4. Priya Putta, Emily Creque, Helen Piontkivska, Edgar E. Kooijman, Lipid-Protein Interactions for ECA1 an N-ANTH Domain Protein Involved in Stress Signaling in Plants, Chemistry and Physics of Lipids (2020) DOI: 10.1016/j.chemphyslip.2020.104919