The investigators discovered this second role for caspase-8
while studying a genetic condition known to exist in only two people--a brother and sister found to have a mutation in both copies of their caspase8 genes.
The repeats, consisting of multiple copies of the amino acid glutamine, convert caspase-8
into an active form, according to test tube studies performed by the researchers.
Expression of the A88V and G11R mutants resulted in elevated levels of the cleaved forms of caspase-3, caspase-8
, caspase-9, and PARP, which are all markers of apoptotic activation while the same markers were unchanged in cells transfected with the negative control virus or the wild-type GJB6 gene.
Activity of caspase-3 (CASP3), caspase-8
(CASP8), and caspase-9 (CASP9) was measured using the Green Caspase Staining Kit (Promokine, Heidelberg, Germany) according to the manufacturer's protocol.
Upon binding with its specific ligand, TRAIL, TRAIL-R2 initiates the recruitment of Fas-associated protein with death domain (FADD) and signaling molecules (such as caspase-8
) to form the death-inducing signaling complex (DISC).
Cell counting kit 8 (CCK-8) and caspase-3, caspase-8
, and caspase-9 fluorescence metric assay kits were purchased from KeyGen BioTECH (Jiangsu, China).
To confirm that the subG1 portion observed in Hep3B cells shown in Figure 1 was due to apoptosis, caspase-3, caspase-8
, and caspase-9 activities were analyzed by flow cytometry.
Zhuo, "HMGB1 promotes the activation of NLRP3 and caspase-8
inflammasomes via NF-[kappa]B pathway in acute glaucoma," Journal of Neuroinflammation, vol.
Recently, NleF has been reported to inhibit the catalytic activity of caspase-4, caspase-8
, and caspase-9 .
In parallel, honokiol induced activations of caspase-8
, -9, and -3, apoptosis, and G1 cell cycle arrest.
Basically, there are two main signaling pathways for cellular apoptosis: a) the mitochondrial or intrinsic pathway that responds to intracellular stimuli and results in cytochrome c release from the mitochondria leading to the activation of Caspase-9; and b) the extrinsic death receptor pathway initiated by ligand binding to extracellular cell death receptors resulting in caspase-8
Studies have indicated that Caspase-8
in external pathway and Caspase-9 in internal pathway act as crucial caspases.