Figure 2
From: Engulfment signals and the phagocytic machinery for apoptotic cell clearance
‘Eat-me’ signals, phagocytic machinery and signaling pathways. Apoptotic cells express ‘eat-me’ signals, such as phosphatidylserine and calreticulin, on the cell surface in response to apoptotic stimuli. Exposed phosphatidylserine on the apoptotic cell surface is recognized directly by phosphatidylserine receptors (Tim family proteins, BAI1, Stabilin-2, CD300f and RAGE) or indirectly by bridging molecules (MFG-E8, Gas6, protein S and C1q). MFG-E8 bound to phosphatidylserine is recognized by integrin αvβ3/5 on the phagocytes, and Gas6 or protein S bound to phosphatidylserine is sensed by Mer-TK. Bridging molecule C1q is recognized by MEGF10 or scarf1. Another ‘eat-me’ signal, calreticulin, is associated with phosphatidylserine or C1q on the apoptotic cell surface and recognized by CD91 (LRP1). Integrin αvβ3/5 and BAI transduce signals for cytoskeletal rearrangement through DOCK180/ELMO1, whereas Stabilin-2, MEGF10 and CD91 use adaptor protein Gulp1 as an engulfment signaling pathway.
