RUI: The Fate of Lipid Rafts in Apoptotic Cells

Amherst College, Amherst MA

Investigators

Abstract

In multicellular organisms, cells are born by the process of cell division, and die by the process of apoptosis. Apoptotic cells are recognized and engulfed by neighboring cells or professional phagocytes such as macrophages. The mechanism of recognition is complex and poorly understood, but depends on the rearrangement of the phospholipids that make up the two leaflets of the plasma membrane. Lipid rearrangement induces membrane proteins to join the recognition process, but the mechanism of this induction is not understood. Prior to rearrangement, some phospholipids and cholesterol in the outer leaflet of the plasma membrane aggregate into domains, or rafts, which segregate from the rest of the membrane some, but not all, of the proteins that cooperate in the recognition of apoptotic cells. The rearrangement of lipids in apoptotic cells may result in the disappearance of these rafts, creating new contacts between receptors and both lipids and other proteins; disruption of rafts is thus a potential mechanism for activating and combining recognition proteins. Determining whether lipid rearrangement disrupts rafts requires analyzing the status of rafts in small subpopulations of still living cells. Dr. Williamson and his students will combine a biophysical approach for detecting rafts (measuring the correlation between fluorescence anisotropy and fluorescence intensity) with flow cytometric analysis of cell subpopulations to determine whether lipid rafts are disrupted during apoptosis. The research in this project will be entirely integrated into an undergraduate teaching environment. Most of the experiments will be carried out by undergraduates, including seniors as part of a capstone research experience, and freshmen/sophomores as an introduction to laboratory research, all under the direct supervision of the Principal Investigator. In addition, the laboratory has repeatedly hosted middle and high school science teachers with no previous exposure to research, for whom this project would be an introduction to the practice of science. The project proposes to develop a (reversible) modification of the mostly widely distributed benchtop clinical cytometer as a platform for testing living cells for the presence of lipid rafts.