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Molecular cloning and characterization of two novel pro-apoptotic isoforms of caspase-10
P W Ng1, A G Porter, R U Jänicke
1Institute of Molecular and Cell Biology, National University of Singapore, Singapore 117609, Republic of Singapore.
Abstract:
Caspase-10/a (Mch4) and caspase-10/b (FLICE2) are related death effector domain-containing cysteine aspartases presumed to be at or near the apex of apoptotic signaling pathways. We report the cloning and characterization of two novel proteins that are splice isoforms of the caspase-10 family. Caspase-10/c is a truncated protein that is essentially a prodomain-only form of the caspase that lacks proteolytic activity in vitro but efficiently induces the formation of perinuclear filamentous structures and cell death in vivo. Caspase-10/c mRNA is specifically up-regulated upon TNF stimulation, suggesting a potential role of this isoform in amplifying the apoptotic response to extracellular stimuli such as cytokines. Caspase-10/d is a hybrid of the known caspases Mch4 and FLICE2, as it is identical to FLICE2 except for the small (p12) catalytic subunit, which is identical to Mch4. Caspase-10/d is proteolytically active in vitro and also induces cell death in vivo, although it is less active than Mch4. The mRNAs for all known isoforms of caspase-10 are abundantly expressed in fetal lung, kidney, and skeletal muscle but are very poorly expressed or absent in these tissues in the adult, implying a possible role for the caspase-10 family in fetal development.
Insights
Two new caspase-10 splice isoforms, caspase-10/c and caspase-10/d, were identified. Caspase-10/c amplifies TNF-induced apoptosis, while both isoforms play roles in fetal development.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Caspase-10/a (Mch4) and caspase-10/b (FLICE2) are cysteine proteases involved in apoptosis.
- These caspases are thought to be critical regulators of programmed cell death pathways.
Purpose of the Study:
- To clone and characterize novel splice isoforms of the caspase-10 family.
- To investigate the functional roles of these new isoforms in apoptosis and development.
Main Methods:
- Cloning and characterization of novel caspase-10 splice isoforms.
- In vitro proteolytic activity assays.
- In vivo cell death and filament formation assays.
- Quantitative analysis of mRNA expression in fetal and adult tissues.
Main Results:
- Caspase-10/c, a prodomain-only isoform, induces cell death and filamentous structures in vivo, with its mRNA upregulated by TNF stimulation.
- Caspase-10/d, a hybrid isoform, exhibits proteolytic activity and induces cell death in vivo, though less potent than Mch4.
- Caspase-10 isoform mRNAs are highly expressed in fetal tissues but downregulated in adults, suggesting a role in development.
Conclusions:
- Caspase-10/c may amplify apoptotic responses to extracellular stimuli.
- Caspase-10/d is a functional, proteolytically active isoform with cell death-inducing capabilities.
- The caspase-10 family likely plays a significant role in fetal development, with expression decreasing postnatally.