Fig. 2.

Extracellular trafficking of eat-me signals through four different mechanisms. Soluble eat-me signals with or without signal peptide are secreted through conventional or unconventional pathways from phagocytes or non-phagocytes, and selectively bind to apoptotic cells. Non-secreted intracellular proteins or molecules, including membrane-anchored eat-me signals, are released during apoptosis through damaged plasma membrane. Finally, enzymes released or activated during apoptosis may modify the surface of apoptotic cells to create new motifs or moieties as eat-me signals.