How do cytosolic proteins interact with lipid droplets? A bio-physical chemical approach to an unresolved biological problem.

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The Chemistry of Life Processes Program in the Chemistry Division has funded Dr. Edgar E. Kooijman and Dr. Elizabeth K. Mann, at Kent State University, to unravel how proteins interact with the surface of lipid droplets. Lipid droplets are fat particles that are crucial for supplying and regulating energy within the cell, and are involved in a whole host of other cellular processes. This research focuses on how proteins in cells are targeted to and bind to the surface of these lipid droplets, where they regulate droplet structure and function. While much is known about how proteins bind to the lipid membrane that encloses complex cells, essentially nothing is known for lipid droplets. Using model proteins, this research is determining the interactions responsible for the binding of lipid droplet proteins. As such, this work is transforming understanding of the structure and function of lipid droplets. Graduate, undergraduate, and high school students are working together in a highly interdisciplinary environment. Additionally, this work is resulting in meaningful educational experiences for low socioeconomic and minority background students, with the goal of increased STEM degrees among diverse students.This research project is an investigation of how cytosolic lipid droplet binding proteins interact with the surface of these crucial, but poorly understood, organelles. Elucidation of the exact protein-lipid interactions is transforming the understanding of lipid droplet biology as results are providing insight not only on lipid metabolism but also on the diverse functions of lipid droplets. Perilipins, and specifically, perilipin 3, are serving as the model protein(s) to characterize exactly how different protein domains are involved in protein-lipid interaction at the lipid droplet interface. Special attention is being given to the amphipathic alpha-helix bundle domain found in many proteins that interact with neutral lipid particles. A diverse array of experimental tools is being used, including a PI-built monolayer trough, a PI-built oil drop tensiometer, site directed mutagenesis, and protein expression and purification, supplemented by in vivo localization studies. This work thus provides key insights into the structure and physiological function of lipid droplets.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.