Blood. 2002 Jun 1;99(11):4070-8.

Characterization of caspase-8L: a novel isoform of caspase-8 that behaves as an inhibitor of the caspase cascade.External

Himeji, D., Horiuchi, T., Tsukamoto, H., Hayashi, K., Watanabe, T., Harada, M.,
--- - Medicine and Biosystemic Science, Kyushu University Graduate School of Medical Sciences, Japan.
Caspase-8 (Fas-associating protein with death domain-like interleukin-1beta- converting enzyme [FLICE]/MACH/Mch5) belongs to a family of cysteine proteases presumed to be the apex of the apoptotic signaling pathways. We recently reported the presence of a novel isoform of caspase-8, named caspase-8L, generated by the alternative splicing of human caspase-8 gene, from human peripheral blood lymphocytes by reverse transcriptase-polymerase chain reaction. We herein report a functional analysis of caspase-8L in the Fas-mediated apoptotic pathway. Caspase-8L is missing the catalytic site of caspase-8 but retains 2 N-terminal repeats of the death-effector domain. The caspase-8L messenger RNA was detected in various tissues but not in any cell lines examined. In human peripheral blood lymphocytes, caspase-8L was strongly suggested to be expressed at the protein level. In MCF-7 cells, caspase-8L transfection itself did not affect cell viability but instead inhibited the apoptosis induced by the cotransfection of caspase-8 in a dominant negative manner. Moreover, Fas-mediated apoptosis was inhibited in caspase-8L-transfected Jurkat cells, which were associated with a reduction in the caspase-8 catalytic activity. In vitro binding assays demonstrated that caspase-8L bound to FADD (Fas-associating protein with death domain) and caspase-8a and blocked the binding of caspase-8 to FADD. In in vivo binding assays, transfected caspase-8L bound to endogenous FADD. Thus, caspase-8L acts as an inhibitor of caspase-8 by interfering with the binding of caspase-8 to FADD and is involved in the regulation of Fas-mediated apoptosis.
PMID: 12010809External
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
In vitro interaction
  DD1 DD2 Reference
Family DD1 DD2 Method Species Region Expression Species Region Expression
DED Caspase8 Link FADD His fusion protein pull-down Human 1-479 In vitro translation Not specified Not specified In vitro translation 12010809
(Link: click this icon to show interactions only between the two corresponding DDs)
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
In vivo interaction
  Endogenous
expression
Overexpression DD1 DD2 Reference
Family DD1 DD2 Method Species Region Species Region
DED Caspase8 Link FADD Co-immunoprecipitation MCF-7 Human 1-276 Not used 12010809
(Link: click this icon to show interactions only between the two corresponding DDs)
Arrow2 In vitro interaction Arrow2 In vivo interaction Arrow2 Characterization Arrow2 Functional role Arrow2 top
Functional Role
Family DD1 DD2 Method Death-related Death-unrelated Reference
DED Caspase8 Link FADD Propidium iodide staining Apoptosis (DISC) 12010809
(Link: click this icon to show interactions only between the two corresponding DDs)