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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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Related in: MedlinePlus

Purification of immature bone marrow neutrophils. (A) After a Percoll gradient isolation, neutrophils were negatively selected. The resulting neutrophil populations were CD7 and CD36 negative. The figure also demonstrates the positively selected cells (right) that were analyzed to further control the purification process. (B) The isolated CD7−CD34−CD36− cells were MPO positive (>97%) and contained a mix of mostly immature neutrophils at different maturation stages as assessed by immunophenotyping and morphology (see Table I).
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fig1: Purification of immature bone marrow neutrophils. (A) After a Percoll gradient isolation, neutrophils were negatively selected. The resulting neutrophil populations were CD7 and CD36 negative. The figure also demonstrates the positively selected cells (right) that were analyzed to further control the purification process. (B) The isolated CD7−CD34−CD36− cells were MPO positive (>97%) and contained a mix of mostly immature neutrophils at different maturation stages as assessed by immunophenotyping and morphology (see Table I).

Mentions: Purification of immature neutrophils from morphologically normal human bone marrow aspirates yielded a pure population of CD34− CD36−CD7−, but also MPO positive cells (Fig. 1, >97%). However, the cell population contained a mix of neutrophils representing different maturation stages (Table I) . When culturing these mostly immature cells, we observed that they did not rapidly undergo cell death (Fig. 2 A) and apoptosis (Fig. 2 B) as seen in mature neutrophils. Because caspase-3 has been described as a key effector caspase in neutrophil apoptosis (27–29), we measured caspase-3 cleavage by immunoblotting. Both freshly purified immature and mature neutrophils contained significant amounts of procaspase-3 (Fig. 2 C). However, the active 17-kD fragment was not detectable in the immature population. Culturing the mature cells was associated with a partial cleavage of procaspase-3 and in the appearance of the p17 fragment usually after 4–8 h of culture. At later time points, cleavage of procaspase-3 continued until the molecule was no longer detectable. In contrast, culturing of immature cells up to 72 h did not result in cleavage of procaspase-3 (Fig. 2 C). Together, these data suggest that immature neutrophils have much lower caspase-3 activity compared with mature neutrophils, resulting in prolonged in vitro survival.


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)

Purification of immature bone marrow neutrophils. (A) After a Percoll gradient isolation, neutrophils were negatively selected. The resulting neutrophil populations were CD7 and CD36 negative. The figure also demonstrates the positively selected cells (right) that were analyzed to further control the purification process. (B) The isolated CD7−CD34−CD36− cells were MPO positive (>97%) and contained a mix of mostly immature neutrophils at different maturation stages as assessed by immunophenotyping and morphology (see Table I).
© Copyright Policy
Related In: Results  -  Collection

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

fig1: Purification of immature bone marrow neutrophils. (A) After a Percoll gradient isolation, neutrophils were negatively selected. The resulting neutrophil populations were CD7 and CD36 negative. The figure also demonstrates the positively selected cells (right) that were analyzed to further control the purification process. (B) The isolated CD7−CD34−CD36− cells were MPO positive (>97%) and contained a mix of mostly immature neutrophils at different maturation stages as assessed by immunophenotyping and morphology (see Table I).
Mentions: Purification of immature neutrophils from morphologically normal human bone marrow aspirates yielded a pure population of CD34− CD36−CD7−, but also MPO positive cells (Fig. 1, >97%). However, the cell population contained a mix of neutrophils representing different maturation stages (Table I) . When culturing these mostly immature cells, we observed that they did not rapidly undergo cell death (Fig. 2 A) and apoptosis (Fig. 2 B) as seen in mature neutrophils. Because caspase-3 has been described as a key effector caspase in neutrophil apoptosis (27–29), we measured caspase-3 cleavage by immunoblotting. Both freshly purified immature and mature neutrophils contained significant amounts of procaspase-3 (Fig. 2 C). However, the active 17-kD fragment was not detectable in the immature population. Culturing the mature cells was associated with a partial cleavage of procaspase-3 and in the appearance of the p17 fragment usually after 4–8 h of culture. At later time points, cleavage of procaspase-3 continued until the molecule was no longer detectable. In contrast, culturing of immature cells up to 72 h did not result in cleavage of procaspase-3 (Fig. 2 C). Together, these data suggest that immature neutrophils have much lower caspase-3 activity compared with mature neutrophils, resulting in prolonged in vitro survival.

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