Doyle B T, O'Neill A J, Newsholme P, Fitzpatrick J M, Watson R W G
Department of Surgery, Mater Misericordiae Hospital, University College Dublin, Ireland.
J Leukoc Biol. 2002 Feb;71(2):247-54.
Human promyelocytic leukaemia cells (HL-60) differentiate into neutrophil-like cells that die spontaneously by apoptosis when treated with retinoic acid (RA). Inhibitors of apoptosis proteins (IAP) bind to and inhibit caspases 3, 7, and 9 activity and the induction of apoptosis. In this study, we demonstrate that undifferentiated HL-60 cells express IAP. During their differentiation, IAP expression is decreased at the mRNA and protein levels. In addition, we show that there is a corresponding increase in the expression and functional activity of active caspases 3 and 9. This activity was associated with the cleavage of XIAP, NAIP, and cIAP-2. Most importantly, we demonstrate that blocking caspase activity does not alter the decrease in IAP protein expression during differentiation but prevents caspase activation, IAP cleavage, and the induction of apoptosis. This result shows that the loss of IAP expression is independent of the induction of apoptosis and is solely related to the differentiation process. However, IAP cleavage is caspase-dependent. Terminal differentiation results in an altered apoptotic phenotype that is associated with the induction of HL-60 cell apoptosis.
人早幼粒细胞白血病细胞（HL-60）在用视黄酸（RA）处理后可分化为嗜中性粒细胞样细胞，并通过凋亡自发死亡。凋亡抑制蛋白（IAP）与半胱天冬酶3、7和9结合并抑制其活性以及凋亡的诱导。在本研究中，我们证明未分化的HL-60细胞表达IAP。在其分化过程中，IAP在mRNA和蛋白质水平上的表达均降低。此外，我们表明活性半胱天冬酶3和9的表达及功能活性相应增加。这种活性与XIAP、NAIP和cIAP-2的裂解有关。最重要的是，我们证明阻断半胱天冬酶活性不会改变分化过程中IAP蛋白表达的降低，但可阻止半胱天冬酶激活、IAP裂解和凋亡诱导。该结果表明IAP表达的丧失与凋亡诱导无关，仅与分化过程有关。然而，IAP裂解是半胱天冬酶依赖性的。终末分化导致凋亡表型改变，这与HL-60细胞凋亡的诱导有关。
