CED-1 is a transmembrane receptor that mediates cell corpse engulfment in C-elegans

We cloned the C. elegans gene ced-1, which is required for the engulfment o f cells undergoing programmed cell death, ced-1 encodes a transmembrane pro tein similar to human SREC (Scavenger Receptor from Endothelial Cells). We showed that ced-1 is expressed in and functions in engulfing cells. The CED -1 protein localizes to cell membranes and clusters around neighboring cell corpses. CED-1 failed to cluster around cell corpses in mutants defective in the engulfment gene ced-7. Motifs in the intracellular domain of CED-1 k nown to interact with PTB and SH2 domains were necessary for engulfment but not for clustering. Our results indicate that CED-1 is a cell surface phag ocytic receptor that recognizes cell corpses. We suggest that the ABC trans porter CED-7 promotes cell corpse recognition by CED-1, possibly by exposin g a phospholipid ligand on the surfaces of cell corpses.