Expression of the inhibitor of apoptosis (IAP) family members in human neutrophils: up-regulation of cIAP2 by granulocyte colony-stimulating factor and overexpression of cIAP2 in chronic neutrophilic leukemia

Abstract

Human neutrophils were found to express members of the inhibitor of apoptosis (IAP) family, namely cellular IAP1 (cIAP1), cIAP2, and X-linked IAP. Among these members, cIAP2 expression was selectively up-regulated by stimulation with granulocyte colony-stimulating factor (G-CSF), but not with granulocytemacrophage CSF. The increased expression of cIAP2 mRNA was detected as early as 30 minutes after in vitro stimulation with G-CSF, and the elevated level of cIAP2 protein was detected at 1 hour. The elevated level of cIAP2 protein was also detected in peripheral blood neutrophils obtained from healthy donors receiving G-CSF administration. G-CSF-induced up-regulation of cIAP2 mRNA and protein, phosphorylation of signal transducer and activator of transcription 3 (STAT3), and the antiapoptotic effects were inhibited by pretreatment of cells with AG490, a specific inhibitor of Janus kinase 2 (JAK2). Mature neutrophils from a patient with chronic neutrophilic leukemia exhibited remarkable overexpression of cIAP2 mRNA and prolongation of survival, whereas cIAP2 mRNA expression and survival in mature neutrophils from patients with chronic myelogenous leukemia were essentially similar to those in normal neutrophils. These findings suggest that cIAP2 expression is upregulated by G-CSF through activation of the JAK2-STAT3 pathway, and increased expression of cIAP2 protein may contribute to G-CSF-mediated antiapoptosis. In addition, overexpression of cIAP2 may be partly responsible for sustained neutrophilia at least in some cases of chronic neutrophilic leukemia. (Blood.

Activation of JNK-dependent Pathway Is Required for HIV Viral Protein R-induced Apoptosis in Human Monocytic Cells

“…Equal aliquots (5 l) of cDNA were subsequently amplified for Bcl2, c-IAP1, and ␤-actin. The oligonucleotide primer sequences used for Bcl2 (Biomol), c-IAP1 (33), and ␤-actin (Stratagene, La Jolla, CA) were as follows: Bcl2: sense, 5Ј-TTC TTT GAG TTC GGT GGG GTC-3Ј; antisense, 5Ј-TGC ATA TTT GTT TGG GGC AGG-3Ј; c-IAP1: sense, 5Ј-AGC TGT TGT CAA CTT CAG ATA CCA CT-3Ј; antisense, 5Ј-TGT TTC ACC AGG TCT CTA TTA AAG CC-3Ј; and ␤-actin: sense, 5Ј-TGA CGG GGT CAC CCA CAC TGT GCC CAT CTA-3Ј; antisense, 5Ј-CTA GAA GCA TTT GCG GTG GAC GAT GGA GGG-3Ј. The amplification conditions for Bcl2, c-IAP1, and ␤-actin were as follows: denaturation at 94°C for 1 min, annealing at 58°C for 1 min, and extension at 72°C for 1 min.…”

Bacterial N-acylhomoserine lactone-induced apoptosis in breast carcinoma cells correlated with down-modulation of STAT3

“…For example, the high level of Bcl XL expressed in the Fas-resistant myeloma cell line U266 is reduced upon STAT3 inactivation, whereupon the cells undergo apoptosis (Catlett-Falcone et al, 1999). More recently, STAT3 has been implicated in the expression of Mcl-1, another Bcl-2 prosurvival family member, and members of the inhibitors of apoptosis (IAP) family in human macrophages and neutrophils, respectively (Hasegawa et al, 2003;Liu et al, 2003). While loss of Mcl-1 is associated with cytochrome c release from mitochondria and the activation of procaspase 9, IAPs are reported to interfere with the activation of procaspases 8 and 9 (Deveraux et al, 1998).…”

Functional characterization of mitochondria in neutrophils: a role restricted to apoptosis

“…Probably, this mechanism controls the intrinsic pathway of apoptosis in neutrophils, since the expression of several members of the IAP family has recently been reported in these cells. 24,47,48 Moreover, delay of neutrophil apoptosis due to impaired degradation of XIAP has been associated with the pathological neutrophil accumulation in chronic neutrophilic leukemia, 46,47 underlining the importance of IAP-dependent regulation of neutrophil cell death. At the same time, an intact activation of caspase-9 in cytoplasts, which are devoid of mitochondrial structures (porin), does not exclude that a cytoplasmic factor also might be involved.…”