Immune cell signaling

Quantitative cell biology in immune cells
Complementing our biochemical measurements on supported membranes, we expanded our effort to perform quantitative cell biology experiments in immune cells to test molecular mechanisms that we generate through our biochemical reconstitution. We use fluorescence microscopy to visualize molecular dynamics inside living cells that have been exposed to gradients of chemoattractants that active cell surface receptors and regulate cell behavior. In addition, we developed approaches to express fluorescently labeled lipid modifying enzymes and signaling molecule activity sensors in immune cells (e.g. neutrophils, mast cells, and macrophages). In order to understand the mechanisms that regulate the dynamics of lipid modifying enzymes in cells, we also established genetic tools that allow us to manipulate the cellular concentration of biomolecules using CRISPR interference. We can now determine the functional significance of membrane binding proteins that we hypothesize regulate lipid kinase and phosphatase activity in cells.

Mechanism controlling cell polarity and migration in human neutrophils
Directed cell migration is critical for innate immune cell function and morphogenesis of multicellular organisms. Through our studies of directed cell migration in human neutrophils, our lab recently discovered that lipid modifying enzymes regulate directed cell migration by functioning in a signaling network that exhibit an excitable behavior. Molecules that display excitability dynamically cycle ON and OFF the plasma membrane in the form of a traveling wave. These oscillatory waves are synchronized with the activation of essential cell polarity factors. Based on our preliminary findings, we hypothesize a feedback loop between PIP lipids and small GTPases controls plasma membrane localization of numerous cell polarity factors in immune cells. Using a combination of genetics, live cell imaging, and in vitro biochemistry, we are investigating how the spatiotemporal dynamics (or excitability) of this signaling system is regulated during neutrophil cell migration.