A role for caspases in the differentiation of erythroid cells and macrophages.

Several cysteine proteases of the caspase family play a central role in many forms of cell death by apoptosis. Other enzymes of the family are involved in cytokine maturation along inflammatory response. In recent years, several caspases involved in cell death were shown to play a role in other cellular processes such as proliferation and differentiation. In the present review, we summarize the current knowledge of the role of caspases in the differentiation of erythroid cells and macrophages. Based on these two examples, we show that the nature of involved enzymes, the pathways leading to their activation in response to specific growth factors, and the specificity of the target proteins that are cleaved by the activated enzymes strongly differ from one cell type to another. Deregulation of these pathways is thought to play a role in the pathophysiology of low-grade myelodysplastic syndromes, characterized by excessive activation of caspases and erythroid precursor apoptosis, and that of chronic myelomonocytic leukemia, characterized by a defective activation of caspases in monocytes exposed to M-CSF, which blocks their differentiation.