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Individual caspase-10 isoforms play distinct and opposing roles in the initiation of death receptor-mediated tumour cell apoptosis.

Mühlethaler-Mottet A, Flahaut M, Bourloud KB, Nardou K, Coulon A, Liberman J, Thome M, Gross N - Cell Death Dis (2011)

Bottom Line: The cysteine protease caspase-8 is an essential executioner of the death receptor (DR) apoptotic pathway.The physiological function of its homologue caspase-10 remains poorly understood, and the ability of caspase-10 to substitute for caspase-8 in the DR apoptotic pathway is still controversial.Further investigations revealed that the unique C-terminal end of caspase-10B was responsible for its degradation by the ubiquitin-proteasome pathway and for its lack of pro-apoptotic activity compared with caspase-10A and -10D.

View Article: PubMed Central - PubMed

Affiliation: Department of Paediatrics, Paediatric Oncology Research, University Hospital CHUV, CH-1011 Lausanne, Switzerland. Annick.Muhlethaler@chuv.ch

ABSTRACT
The cysteine protease caspase-8 is an essential executioner of the death receptor (DR) apoptotic pathway. The physiological function of its homologue caspase-10 remains poorly understood, and the ability of caspase-10 to substitute for caspase-8 in the DR apoptotic pathway is still controversial. Here, we analysed the particular contribution of caspase-10 isoforms to DR-mediated apoptosis in neuroblastoma (NB) cells characterised by their resistance to DR signalling. Silencing of caspase-8 in tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-sensitive NB cells resulted in complete resistance to TRAIL, which could be reverted by overexpression of caspase-10A or -10D. Overexpression experiments in various caspase-8-expressing tumour cells also demonstrated that caspase-10A and -10D isoforms strongly increased TRAIL and FasL sensitivity, whereas caspase-10B or -10G had no effect or were weakly anti-apoptotic. Further investigations revealed that the unique C-terminal end of caspase-10B was responsible for its degradation by the ubiquitin-proteasome pathway and for its lack of pro-apoptotic activity compared with caspase-10A and -10D. These data highlight in several tumour cell types, a differential pro- or anti-apoptotic role for the distinct caspase-10 isoforms in DR signalling, which may be relevant for fine tuning of apoptosis initiation.

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Analysis of the expression levels of caspase-8 and -10 isoforms. (a) Schematic representation of caspase-10 and -8 protein isoforms. Regions encoded by alternative exons are indicated. DED, death effector domain. (b) Whole cell extracts from various cell lines were loaded on a 15% SDS-polyacrylamide gel as described,40 and analysed by immunoblotting for the expression of caspase-8 and -10 isoforms. The three types of NB cells (S, substrate adherent; I, intermediate; N, neuroblastic) are represented. n.d., not determined. The immunoblot for endogenous caspase-10 detection were revealed using the ECL Advanced western blotting substrate for stronger signal detection. (c) Caspase-8 and -10 mRNA expression levels in tumour cells were compared by semi-quantitative real-time PCR. Plots represent means of three separate experiments
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fig1: Analysis of the expression levels of caspase-8 and -10 isoforms. (a) Schematic representation of caspase-10 and -8 protein isoforms. Regions encoded by alternative exons are indicated. DED, death effector domain. (b) Whole cell extracts from various cell lines were loaded on a 15% SDS-polyacrylamide gel as described,40 and analysed by immunoblotting for the expression of caspase-8 and -10 isoforms. The three types of NB cells (S, substrate adherent; I, intermediate; N, neuroblastic) are represented. n.d., not determined. The immunoblot for endogenous caspase-10 detection were revealed using the ECL Advanced western blotting substrate for stronger signal detection. (c) Caspase-8 and -10 mRNA expression levels in tumour cells were compared by semi-quantitative real-time PCR. Plots represent means of three separate experiments

Mentions: Caspase-10 is highly homologous to caspase-8 and the CASP10 gene is linked to the CASP8 gene at the human chromosome locus 2q33-34, suggesting tandem duplication.10, 11 However, in contrast to caspase-8, no ortholog of human caspase-10 exists in mice. Different splice variants of caspase-8 and -10 mRNA have been identified, which lead to the production of several closely related isoforms.3, 11, 12, 13, 14 Although the two full-length caspase-8A and B isoforms are pro-apoptotic, the truncated caspase-8L isoform, acting as dominant-negative isoform, is anti-apoptotic (Figure 1a).3 Caspase-10 is expressed as three full-length isoforms, caspase-10A, B and D, and a truncated isoform, caspase-10G, consisting of only the two death effector domains (DEDs)12, 13, 14 (Figure 1a). This smaller isoform was initially described as caspase-10C, but its transcript is supposed to be untranslated because of nonsense-mediated mRNA decay.13


Individual caspase-10 isoforms play distinct and opposing roles in the initiation of death receptor-mediated tumour cell apoptosis.

Mühlethaler-Mottet A, Flahaut M, Bourloud KB, Nardou K, Coulon A, Liberman J, Thome M, Gross N - Cell Death Dis (2011)

Analysis of the expression levels of caspase-8 and -10 isoforms. (a) Schematic representation of caspase-10 and -8 protein isoforms. Regions encoded by alternative exons are indicated. DED, death effector domain. (b) Whole cell extracts from various cell lines were loaded on a 15% SDS-polyacrylamide gel as described,40 and analysed by immunoblotting for the expression of caspase-8 and -10 isoforms. The three types of NB cells (S, substrate adherent; I, intermediate; N, neuroblastic) are represented. n.d., not determined. The immunoblot for endogenous caspase-10 detection were revealed using the ECL Advanced western blotting substrate for stronger signal detection. (c) Caspase-8 and -10 mRNA expression levels in tumour cells were compared by semi-quantitative real-time PCR. Plots represent means of three separate experiments
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3101821&req=5

fig1: Analysis of the expression levels of caspase-8 and -10 isoforms. (a) Schematic representation of caspase-10 and -8 protein isoforms. Regions encoded by alternative exons are indicated. DED, death effector domain. (b) Whole cell extracts from various cell lines were loaded on a 15% SDS-polyacrylamide gel as described,40 and analysed by immunoblotting for the expression of caspase-8 and -10 isoforms. The three types of NB cells (S, substrate adherent; I, intermediate; N, neuroblastic) are represented. n.d., not determined. The immunoblot for endogenous caspase-10 detection were revealed using the ECL Advanced western blotting substrate for stronger signal detection. (c) Caspase-8 and -10 mRNA expression levels in tumour cells were compared by semi-quantitative real-time PCR. Plots represent means of three separate experiments
Mentions: Caspase-10 is highly homologous to caspase-8 and the CASP10 gene is linked to the CASP8 gene at the human chromosome locus 2q33-34, suggesting tandem duplication.10, 11 However, in contrast to caspase-8, no ortholog of human caspase-10 exists in mice. Different splice variants of caspase-8 and -10 mRNA have been identified, which lead to the production of several closely related isoforms.3, 11, 12, 13, 14 Although the two full-length caspase-8A and B isoforms are pro-apoptotic, the truncated caspase-8L isoform, acting as dominant-negative isoform, is anti-apoptotic (Figure 1a).3 Caspase-10 is expressed as three full-length isoforms, caspase-10A, B and D, and a truncated isoform, caspase-10G, consisting of only the two death effector domains (DEDs)12, 13, 14 (Figure 1a). This smaller isoform was initially described as caspase-10C, but its transcript is supposed to be untranslated because of nonsense-mediated mRNA decay.13

Bottom Line: The cysteine protease caspase-8 is an essential executioner of the death receptor (DR) apoptotic pathway.The physiological function of its homologue caspase-10 remains poorly understood, and the ability of caspase-10 to substitute for caspase-8 in the DR apoptotic pathway is still controversial.Further investigations revealed that the unique C-terminal end of caspase-10B was responsible for its degradation by the ubiquitin-proteasome pathway and for its lack of pro-apoptotic activity compared with caspase-10A and -10D.

View Article: PubMed Central - PubMed

Affiliation: Department of Paediatrics, Paediatric Oncology Research, University Hospital CHUV, CH-1011 Lausanne, Switzerland. Annick.Muhlethaler@chuv.ch

ABSTRACT
The cysteine protease caspase-8 is an essential executioner of the death receptor (DR) apoptotic pathway. The physiological function of its homologue caspase-10 remains poorly understood, and the ability of caspase-10 to substitute for caspase-8 in the DR apoptotic pathway is still controversial. Here, we analysed the particular contribution of caspase-10 isoforms to DR-mediated apoptosis in neuroblastoma (NB) cells characterised by their resistance to DR signalling. Silencing of caspase-8 in tumour necrosis factor-related apoptosis-inducing ligand (TRAIL)-sensitive NB cells resulted in complete resistance to TRAIL, which could be reverted by overexpression of caspase-10A or -10D. Overexpression experiments in various caspase-8-expressing tumour cells also demonstrated that caspase-10A and -10D isoforms strongly increased TRAIL and FasL sensitivity, whereas caspase-10B or -10G had no effect or were weakly anti-apoptotic. Further investigations revealed that the unique C-terminal end of caspase-10B was responsible for its degradation by the ubiquitin-proteasome pathway and for its lack of pro-apoptotic activity compared with caspase-10A and -10D. These data highlight in several tumour cell types, a differential pro- or anti-apoptotic role for the distinct caspase-10 isoforms in DR signalling, which may be relevant for fine tuning of apoptosis initiation.

Show MeSH
Related in: MedlinePlus