Autophagy genes promote apoptotic cell corpse clearance.

Autophagy is a catabolic process through which damaged organelles and protein aggregates are delivered to lysosomes for degradation. Autophagy genes are reported to promote exposure of "eat me" signals on the surface of apoptotic cells, but whether they function in engulfing cells is not clear. Recently, we found that the autophagy mutants atg-18 and epg-5 are defective in removing apoptotic cells derived from the C. elegans Q neuroblast, a phenotype that can be fully rescued by expression of ATG-18 and EPG-5 in the engulfing cell. Loss of ATG-18 or EPG-5 does not affect cell corpse engulfment but causes defects in phagosomal recruitment of RAB-5 and RAB-7 and formation of phagolysosomes. EPG-5, ATG-18 and LGG-1 are sequentially recruited to phagosomes, suggesting that they function at different steps of phagosomal maturation. Our studies indicate that autophagy genes function sequentially to promote apoptotic cell corpse degradation in the engulfing cell.