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Acetylation suppresses the proapoptotic activity of GD3 ganglioside.

Malisan F, Franchi L, Tomassini B, Ventura N, Condò I, Rippo MR, Rufini A, Liberati L, Nachtigall C, Kniep B, Testi R - J. Exp. Med. (2002)

Bottom Line: We found that sialic acid acetylation suppresses the proapoptotic activity of GD3.In fact, unlike GD3, 9-O-acetyl-GD3 is completely ineffective in inducing cytochrome c release and caspase-9 activation on isolated mitochondria and fails to induce the collapse of mitochondrial transmembrane potential and cellular apoptosis.The coexpression of GD3 synthase with a viral 9-O-acetyl esterase, which prevents 9-O-acetyl-GD3 accumulation, reconstitutes GD3 responsiveness and apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Immunology and Signal Transduction, Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, 00133 Rome, Italy.

ABSTRACT
GD3 synthase is rapidly activated in different cell types after specific apoptotic stimuli. De novo synthesized GD3 accumulates and contributes to the apoptotic program by relocating to mitochondrial membranes and inducing the release of apoptogenic factors. We found that sialic acid acetylation suppresses the proapoptotic activity of GD3. In fact, unlike GD3, 9-O-acetyl-GD3 is completely ineffective in inducing cytochrome c release and caspase-9 activation on isolated mitochondria and fails to induce the collapse of mitochondrial transmembrane potential and cellular apoptosis. Moreover, cells which are resistant to the overexpression of the GD3 synthase, actively convert de novo synthesized GD3 to 9-O-acetyl-GD3. The coexpression of GD3 synthase with a viral 9-O-acetyl esterase, which prevents 9-O-acetyl-GD3 accumulation, reconstitutes GD3 responsiveness and apoptosis. Finally, the expression of the 9-O-acetyl esterase is sufficient to induce apoptosis of glioblastomas which express high levels of 9-O-acetyl-GD3. Thus, sialic acid acetylation critically controls the proapoptotic activity of GD3.

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9-O-acetyl GD3 is unable to induce mitochondrial damage and apoptosis of HEK-293 cells. The percentage of HEK-293 cells with ΔΨm loss (A) or condensed nuclei (B) was analyzed at 30 h after stimulation with 200 μM of exogenous GD3, 9-O-acetyl GD3 (acGD3), and deacetylated 9-O-acetyl GD3 (de-ac-GD3). Data represent the mean ± 1 SD from three independent experiments.
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fig2: 9-O-acetyl GD3 is unable to induce mitochondrial damage and apoptosis of HEK-293 cells. The percentage of HEK-293 cells with ΔΨm loss (A) or condensed nuclei (B) was analyzed at 30 h after stimulation with 200 μM of exogenous GD3, 9-O-acetyl GD3 (acGD3), and deacetylated 9-O-acetyl GD3 (de-ac-GD3). Data represent the mean ± 1 SD from three independent experiments.

Mentions: Exposure of intact cells to exogenous GD3 induces the collapse of mitochondrial transmembrane potential (ΔΨm) and triggers apoptosis. To investigate whether sialic acid acetylation affected the proapoptotic activity of GD3, HEK-293 cells were exposed to 9-O-acetyl GD3. As shown in Fig. 2, 9-O -acetyl GD3 could not affect the mitochondrial transmembrane potential of HEK-293 cells (Fig. 2 A), nor induce apoptosis (Fig. 2 B). In vitro deacetylation of sialic acid restored the ability of 9-O-acetyl GD3 to induce mitochondrial changes and apoptosis. Moreover, competition experiments indicated that 9-O-acetyl GD3 could not prevent GD3-induced apoptosis (unpublished data). Together these results strongly suggested that sialic acid 9-O-acetylation might represent a mechanism to inactivate GD3 in vivo. We therefore further investigated the functional implications of this finding.


Acetylation suppresses the proapoptotic activity of GD3 ganglioside.

Malisan F, Franchi L, Tomassini B, Ventura N, Condò I, Rippo MR, Rufini A, Liberati L, Nachtigall C, Kniep B, Testi R - J. Exp. Med. (2002)

9-O-acetyl GD3 is unable to induce mitochondrial damage and apoptosis of HEK-293 cells. The percentage of HEK-293 cells with ΔΨm loss (A) or condensed nuclei (B) was analyzed at 30 h after stimulation with 200 μM of exogenous GD3, 9-O-acetyl GD3 (acGD3), and deacetylated 9-O-acetyl GD3 (de-ac-GD3). Data represent the mean ± 1 SD from three independent experiments.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196066&req=5

fig2: 9-O-acetyl GD3 is unable to induce mitochondrial damage and apoptosis of HEK-293 cells. The percentage of HEK-293 cells with ΔΨm loss (A) or condensed nuclei (B) was analyzed at 30 h after stimulation with 200 μM of exogenous GD3, 9-O-acetyl GD3 (acGD3), and deacetylated 9-O-acetyl GD3 (de-ac-GD3). Data represent the mean ± 1 SD from three independent experiments.
Mentions: Exposure of intact cells to exogenous GD3 induces the collapse of mitochondrial transmembrane potential (ΔΨm) and triggers apoptosis. To investigate whether sialic acid acetylation affected the proapoptotic activity of GD3, HEK-293 cells were exposed to 9-O-acetyl GD3. As shown in Fig. 2, 9-O -acetyl GD3 could not affect the mitochondrial transmembrane potential of HEK-293 cells (Fig. 2 A), nor induce apoptosis (Fig. 2 B). In vitro deacetylation of sialic acid restored the ability of 9-O-acetyl GD3 to induce mitochondrial changes and apoptosis. Moreover, competition experiments indicated that 9-O-acetyl GD3 could not prevent GD3-induced apoptosis (unpublished data). Together these results strongly suggested that sialic acid 9-O-acetylation might represent a mechanism to inactivate GD3 in vivo. We therefore further investigated the functional implications of this finding.

Bottom Line: We found that sialic acid acetylation suppresses the proapoptotic activity of GD3.In fact, unlike GD3, 9-O-acetyl-GD3 is completely ineffective in inducing cytochrome c release and caspase-9 activation on isolated mitochondria and fails to induce the collapse of mitochondrial transmembrane potential and cellular apoptosis.The coexpression of GD3 synthase with a viral 9-O-acetyl esterase, which prevents 9-O-acetyl-GD3 accumulation, reconstitutes GD3 responsiveness and apoptosis.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Immunology and Signal Transduction, Department of Experimental Medicine and Biochemical Sciences, University of Rome Tor Vergata, 00133 Rome, Italy.

ABSTRACT
GD3 synthase is rapidly activated in different cell types after specific apoptotic stimuli. De novo synthesized GD3 accumulates and contributes to the apoptotic program by relocating to mitochondrial membranes and inducing the release of apoptogenic factors. We found that sialic acid acetylation suppresses the proapoptotic activity of GD3. In fact, unlike GD3, 9-O-acetyl-GD3 is completely ineffective in inducing cytochrome c release and caspase-9 activation on isolated mitochondria and fails to induce the collapse of mitochondrial transmembrane potential and cellular apoptosis. Moreover, cells which are resistant to the overexpression of the GD3 synthase, actively convert de novo synthesized GD3 to 9-O-acetyl-GD3. The coexpression of GD3 synthase with a viral 9-O-acetyl esterase, which prevents 9-O-acetyl-GD3 accumulation, reconstitutes GD3 responsiveness and apoptosis. Finally, the expression of the 9-O-acetyl esterase is sufficient to induce apoptosis of glioblastomas which express high levels of 9-O-acetyl-GD3. Thus, sialic acid acetylation critically controls the proapoptotic activity of GD3.

Show MeSH
Related in: MedlinePlus