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Dominant expression of a novel splice variant of caspase-8 in human peripheral blood lymphocytes
T Horiuchi1, D Himeji, H Tsukamoto
1Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences, Fukuoka, Japan. horiuchi@intmed1.med.kyushu-u.ac.jp
Abstract:
Caspase-8 is an apical and critical proteolytic enzyme in the cascade of apoptosis. As a result of alternative splicing, the generation of at least 7 isoforms of caspase-8 has been reported. The existence of multiple isoforms that lack the essential domains for apoptosis suggests the possible role of these isoforms on the regulation of apoptosis. Here we report a novel longer isoform of caspase-8 (caspase-8L) that was generated by alternative splicing of intron 8, thereby carrying a 136-bp insertion and frame shift of the transcript. The transcript encoded N-terminal two repeats of death effector domain (DED) of caspase-8, but lacking the C-terminal half of the proteolytic domain. Reverse transcriptase (RT)-polymerase chain reaction (PCR) analysis revealed the dominant expression of caspase-8L transcript compared to the intact form of caspase-8 in human peripheral blood lymphocyte (PBL) and T cells. In patients with systemic lupus erythematosus (SLE), imbalanced expression of caspase-8L transcript was identified. These results suggest the important role of caspase-8L in the modulation of apoptosis.
Insights
A novel caspase-8 isoform, caspase-8L, generated by alternative splicing, is predominantly expressed in human immune cells. Imbalanced caspase-8L expression was observed in systemic lupus erythematosus patients, suggesting its role in apoptosis regulation.
Area of Science:
- Molecular Biology
- Immunology
- Cell Biology
Background:
- Caspase-8 is a key enzyme in apoptosis.
- Alternative splicing generates multiple caspase-8 isoforms.
- Some isoforms may regulate apoptosis due to domain variations.
Purpose of the Study:
- To report a novel longer isoform of caspase-8, termed caspase-8L.
- To investigate the expression of caspase-8L in human immune cells.
- To explore the role of caspase-8L in systemic lupus erythematosus (SLE).
Main Methods:
- Alternative splicing analysis to identify caspase-8L.
- Reverse transcriptase-polymerase chain reaction (RT-PCR) for transcript expression analysis.
- Comparison of caspase-8L expression in healthy individuals and SLE patients.
Main Results:
- A novel caspase-8L isoform was identified, resulting from intron 8 splicing with a 136-bp insertion and frame shift.
- Caspase-8L transcript showed dominant expression over intact caspase-8 in human peripheral blood lymphocytes (PBL) and T cells.
- Imbalanced caspase-8L transcript expression was detected in patients with systemic lupus erythematosus (SLE).
Conclusions:
- Caspase-8L is a novel, alternatively spliced isoform of caspase-8.
- Caspase-8L is predominantly expressed in human PBL and T cells.
- The imbalanced expression of caspase-8L in SLE suggests its involvement in apoptosis modulation and potential disease relevance.