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Chapter 15 Phosphatidylserine exposure and phagocytosis of apoptotic cells

2001; Elsevier BV; Linguagem: Inglês

10.1016/s0091-679x(01)66016-3

0091-679X

Patrick Williamson, Stefan van den Eijnde, Robert Schlegel,

Cell death mechanisms and regulation

This chapter describes methods for detecting apoptotic cells by loss of asymmetry and exposure of phosphatidylserine (PS) and methods for assessing phagocytosis of apoptotic cells. Several tools are available for assessing the distribution of phospholipids across the plasma membrane as well as the transbilayer lipid movements that underlie that distribution. The normal phospholipid distribution is one in which phosphatidylcholine (PC) and sphingomyelin are present mainly in the external leaflet, while most of the phosphatidylethanolamine (PE) and all of the PS are located in the internal leaflet. Loss of lipid asymmetry, through randomization of lipids across the bilayer, results in exposure of PS on the cell surface, where it can be detected by binding of the Ca2+-dependent, Annexin V, and PS-specific protein . Loss of asymmetry alters the biophysical properties of the plasma membrane bilayer and detection is possible in some circumstances by measuring the binding of the naturally fluorescent dye merocyanine 540 (MC540). Quantification of the frequency of cells exposing PS by measuring the number of cells that bind Annexin V is the one of the simplest of the assays available for assessing an early stage of apoptosis.