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The ultimate step in the "programmed cell death" (apoptosis) is clearance of apoptotic cells by phagocytes. This type of phagocytosis requires formation of filopodia, which surround the apoptotic cell to be engulfed. Filopodia formation is driven by actin polymerization (formaiton of filamentous F-actin). The data, reported by Miller et al. in this issue (Mol. Biol. Cell [2003]. 14, 4196-4206) and in J. Biol. Chem. (2001) 276, 19431-19439, demonstrate that F-actin of filopodia colocalizes with the macrophage enzyme 12/15-lipoxygenase (12/15-L0) and that the 12/15-L0 activity promotes actin polymerization and phagocytosis. The image on the cover shows a fragment of a peritoneal macrophage that is in the process of phagocytosing apoptotic thymocytes (Hoechst-stained blue nuclei of condensed chromatin). One apoptotic cell is surrounded by vast filopodia, which appear bright yellow because of colocalized concentration of F-actin (green, stained with FITC-phalloidin) and 12/15-L0 (red, antibody staining). This image is a "volume view" compiled from the areas of maximal intensity of individual optical sections throughout the cells. An animated three-dimensional reconstruction of this cell group is available as an online supplement to the article by Miller et al. in this issue (Mol. Biol. Cell [2003]. 14, 4196-4206).

-Y.I. Miller, D.S. Worrall, C.D. Funk, J.R. Feramisco, and J.L. Witztum.