Involvement of Beclin 1 in engulfment of apoptotic cells.

Efficient apoptotic cell engulfment is important for both tissue homeostasis and immune response in mammals. In the present study, we report that Beclin 1 (a regulator of autophagy) is required for apoptotic cell engulfment. The engulfment process was largely abolished in Beclin 1 knock-out cells, and Beclin 1 knockdown significantly decreased apoptotic cell internalization in macrophage and fibroblast cell lines. Beclin 1 was recruited to the early phagocytic cup along with the generation of phosphatidylinositol 3-phosphate and Rac1, which regulates actin dynamics in lamellipodia. No lamellipodia were formed in Beclin 1 knock-out cells, and Beclin 1 knockdown completely inhibited the promotion of engulfment by ectopic expression of Rac1. Beclin 1 was co-immunoprecipitated with Rac1. These data indicate that Beclin 1 coordinates actin dynamics and membrane phospholipid synthesis to promote efficient apoptotic cell engulfment.