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Inflammation-associated cell cycle-independent block of apoptosis by survivin in terminally differentiated neutrophils.

Altznauer F, Martinelli S, Yousefi S, Thürig C, Schmid I, Conway EM, Schöni MH, Vogt P, Mueller C, Fey MF, Zangemeister-Wittke U, Simon HU - J. Exp. Med. (2004)

Bottom Line: Strikingly, these cells reexpressed survivin upon granulocyte/macrophage colony-stimulating factor (CSF) or granulocyte CSF stimulation in vitro and under inflammatory conditions in vivo.Together, our findings demonstrate the following: (a) overexpression of survivin occurs in primary, even terminally differentiated cells and is not restricted to proliferating cells; and (b) survivin acts as an inhibitor of apoptosis protein in a cell cycle-independent manner.Therefore, survivin plays distinct and independent roles in the maintenance of the G2-M checkpoint and in apoptosis control, and its overexpression is not restricted to proliferating cells.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Pharmacology, University of Bern, Friedbühlstrasse 49, CH-3010 Bern, Switzerland.

ABSTRACT
Survivin has received great attention due to its expression in many human tumors and its potential as a therapeutic target in cancer. Survivin expression has been described to be cell cycle-dependent and restricted to the G2-M checkpoint, where it inhibits apoptosis in proliferating cells. In agreement with this current view, we found that survivin expression was high in immature neutrophils, which proliferate during differentiation. In contrast with immature cells, mature neutrophils contained only little or no survivin protein. Strikingly, these cells reexpressed survivin upon granulocyte/macrophage colony-stimulating factor (CSF) or granulocyte CSF stimulation in vitro and under inflammatory conditions in vivo. Moreover, survivin-deficient mature neutrophils were unable to increase their lifespan after survival factor exposure. Together, our findings demonstrate the following: (a) overexpression of survivin occurs in primary, even terminally differentiated cells and is not restricted to proliferating cells; and (b) survivin acts as an inhibitor of apoptosis protein in a cell cycle-independent manner. Therefore, survivin plays distinct and independent roles in the maintenance of the G2-M checkpoint and in apoptosis control, and its overexpression is not restricted to proliferating cells. These data provide new insights into the regulation and function of survivin and have important implications for the pathogenesis, diagnosis, and treatment of inflammatory diseases and cancer.

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Expression of IAP family members in freshly purified immature and mature neutrophils. (A) Immunoblotting. Mature neutrophils expressed detectable levels of XIAP, IAP-1, IAP-2, and survivin. NAIP was often not detectable. Immature neutrophils expressed large amounts of survivin. Filters were reprobed with anti-GAPDH or anti–β-actin mAbs to ensure equal loading of the gels. For both immature and mature neutrophil populations, results from three different donors are shown (1–3). (B) Confocal microscopy. Survivin was readily detected in immature, but not in mature, neutrophils. Survivin was localized in both nucleus and cytoplasm of immature cells. Caspase-3 was expressed in the cytoplasm of both immature and mature neutrophils. Interestingly, myeloblasts (white arrows) did not express detectable levels of caspase-3. Bars, 10 μm. The results are representative of five independent experiments.
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fig3: Expression of IAP family members in freshly purified immature and mature neutrophils. (A) Immunoblotting. Mature neutrophils expressed detectable levels of XIAP, IAP-1, IAP-2, and survivin. NAIP was often not detectable. Immature neutrophils expressed large amounts of survivin. Filters were reprobed with anti-GAPDH or anti–β-actin mAbs to ensure equal loading of the gels. For both immature and mature neutrophil populations, results from three different donors are shown (1–3). (B) Confocal microscopy. Survivin was readily detected in immature, but not in mature, neutrophils. Survivin was localized in both nucleus and cytoplasm of immature cells. Caspase-3 was expressed in the cytoplasm of both immature and mature neutrophils. Interestingly, myeloblasts (white arrows) did not express detectable levels of caspase-3. Bars, 10 μm. The results are representative of five independent experiments.

Mentions: The antiapoptotic effects of members of the IAP family have often been associated with decreased enzymatic caspase activities (1, 2). Because caspase-3 did not demonstrate evidence for high activity in immature neutrophils, we hypothesized that specific IAPs are involved in the inhibition of nascent active caspases in these cells. Expression of IAPs was investigated by immunoblotting (Fig. 3 A). XIAP levels were increased in two out of three investigated immature neutrophil populations compared with mature blood neutrophils. However, the most impressive difference was seen in the levels of survivin, which were dramatically increased in immature compared with mature cells. In contrast, levels of IAP-1, IAP-2, and NAIP did not show consistent differences between the two cell populations. Immunofluorescence and laser scan microscopic analysis confirmed that survivin was highly expressed in immature neutrophils, but not in mature neutrophils from normal individuals, and was detectable both in the nucleus and the cytoplasm (Fig. 3 B). Interestingly, caspase-3 was not expressed at early stages of neutrophil maturation (myeloblast; Fig. 3 B, arrows).


Inflammation-associated cell cycle-independent block of apoptosis by survivin in terminally differentiated neutrophils.

Altznauer F, Martinelli S, Yousefi S, Thürig C, Schmid I, Conway EM, Schöni MH, Vogt P, Mueller C, Fey MF, Zangemeister-Wittke U, Simon HU - J. Exp. Med. (2004)

Expression of IAP family members in freshly purified immature and mature neutrophils. (A) Immunoblotting. Mature neutrophils expressed detectable levels of XIAP, IAP-1, IAP-2, and survivin. NAIP was often not detectable. Immature neutrophils expressed large amounts of survivin. Filters were reprobed with anti-GAPDH or anti–β-actin mAbs to ensure equal loading of the gels. For both immature and mature neutrophil populations, results from three different donors are shown (1–3). (B) Confocal microscopy. Survivin was readily detected in immature, but not in mature, neutrophils. Survivin was localized in both nucleus and cytoplasm of immature cells. Caspase-3 was expressed in the cytoplasm of both immature and mature neutrophils. Interestingly, myeloblasts (white arrows) did not express detectable levels of caspase-3. Bars, 10 μm. The results are representative of five independent experiments.
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Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2211817&req=5

fig3: Expression of IAP family members in freshly purified immature and mature neutrophils. (A) Immunoblotting. Mature neutrophils expressed detectable levels of XIAP, IAP-1, IAP-2, and survivin. NAIP was often not detectable. Immature neutrophils expressed large amounts of survivin. Filters were reprobed with anti-GAPDH or anti–β-actin mAbs to ensure equal loading of the gels. For both immature and mature neutrophil populations, results from three different donors are shown (1–3). (B) Confocal microscopy. Survivin was readily detected in immature, but not in mature, neutrophils. Survivin was localized in both nucleus and cytoplasm of immature cells. Caspase-3 was expressed in the cytoplasm of both immature and mature neutrophils. Interestingly, myeloblasts (white arrows) did not express detectable levels of caspase-3. Bars, 10 μm. The results are representative of five independent experiments.
Mentions: The antiapoptotic effects of members of the IAP family have often been associated with decreased enzymatic caspase activities (1, 2). Because caspase-3 did not demonstrate evidence for high activity in immature neutrophils, we hypothesized that specific IAPs are involved in the inhibition of nascent active caspases in these cells. Expression of IAPs was investigated by immunoblotting (Fig. 3 A). XIAP levels were increased in two out of three investigated immature neutrophil populations compared with mature blood neutrophils. However, the most impressive difference was seen in the levels of survivin, which were dramatically increased in immature compared with mature cells. In contrast, levels of IAP-1, IAP-2, and NAIP did not show consistent differences between the two cell populations. Immunofluorescence and laser scan microscopic analysis confirmed that survivin was highly expressed in immature neutrophils, but not in mature neutrophils from normal individuals, and was detectable both in the nucleus and the cytoplasm (Fig. 3 B). Interestingly, caspase-3 was not expressed at early stages of neutrophil maturation (myeloblast; Fig. 3 B, arrows).

Bottom Line: Strikingly, these cells reexpressed survivin upon granulocyte/macrophage colony-stimulating factor (CSF) or granulocyte CSF stimulation in vitro and under inflammatory conditions in vivo.Together, our findings demonstrate the following: (a) overexpression of survivin occurs in primary, even terminally differentiated cells and is not restricted to proliferating cells; and (b) survivin acts as an inhibitor of apoptosis protein in a cell cycle-independent manner.Therefore, survivin plays distinct and independent roles in the maintenance of the G2-M checkpoint and in apoptosis control, and its overexpression is not restricted to proliferating cells.

View Article: PubMed Central - PubMed

Affiliation: Dept. of Pharmacology, University of Bern, Friedbühlstrasse 49, CH-3010 Bern, Switzerland.

ABSTRACT
Survivin has received great attention due to its expression in many human tumors and its potential as a therapeutic target in cancer. Survivin expression has been described to be cell cycle-dependent and restricted to the G2-M checkpoint, where it inhibits apoptosis in proliferating cells. In agreement with this current view, we found that survivin expression was high in immature neutrophils, which proliferate during differentiation. In contrast with immature cells, mature neutrophils contained only little or no survivin protein. Strikingly, these cells reexpressed survivin upon granulocyte/macrophage colony-stimulating factor (CSF) or granulocyte CSF stimulation in vitro and under inflammatory conditions in vivo. Moreover, survivin-deficient mature neutrophils were unable to increase their lifespan after survival factor exposure. Together, our findings demonstrate the following: (a) overexpression of survivin occurs in primary, even terminally differentiated cells and is not restricted to proliferating cells; and (b) survivin acts as an inhibitor of apoptosis protein in a cell cycle-independent manner. Therefore, survivin plays distinct and independent roles in the maintenance of the G2-M checkpoint and in apoptosis control, and its overexpression is not restricted to proliferating cells. These data provide new insights into the regulation and function of survivin and have important implications for the pathogenesis, diagnosis, and treatment of inflammatory diseases and cancer.

Show MeSH
Related in: MedlinePlus