FIG. 10. Model for ribotoxin-induced rRNA cleavage model in RAW 264.7 cells.
Picture depicts putative signaling pathways for induction of rRNA cleavage by DON, anisomycin, SG and ricin. DON and anisomycin sequentially activate PKR/Hck, p38, p53 and caspases leading to apoptosis-associate rRNA cleavage, while SG and ricin activate p53 and caspases by an alternative mechanism. Cathepsin L released from lysosome promotes DON-, anisomycin-, SG- and ricin-induced apoptosis and rRNA cleavage. Both constitutive (c) and inducible (i) RNases might contribute to the ribotoxin-induced cleavage of rRNA exposed by caspase action. Black and gray circles represent cathepsins and cytochrome c, respectively.