Activity of protein kinase CK2 uncouples Bid cleavage from caspase-8 activation

Abstract

SummaryIn the present study, we quantitatively analysed the interface between apoptosis initiation and execution by determining caspase-8 activation, Bid cleavage and mitochondrial engagement (onset of mitochondrial depolarisation) in individual HeLa cervical cancer cells following exposure to tumour-necrosis-factor-related apoptosis-inducing ligand (TRAIL). Employing resonance-energy-transfer probes containing either the caspase-8 recognition site IETD or full-length Bid, we observed a significant delay between the times of caspase-8 activation and Bid cleavage, suggesting the existence of control steps separating these two processes. Subsequent analyses suggested that the divergence of caspase-8 activation and Bid cleavage are critically controlled by kinase signalling: inhibiting protein kinase CK2 by using 5,6-dichloro-l-(-D-ribofuranosyl-1)-benzimidazole (DRB) or by overexpression of a dominant-negative CK2 catalytic subunit largely eliminated the lag time between caspase-8 activation and Bid cleavage. We conclude that caspase-8 activation and Bid cleavage are temporally uncoupled events, providing transient tolerance to caspase-8 activities.

A fate worse than death: apoptosis as an oncogenic process

“…A prime candidate might be BID, of which minimal cleavage is required to kill a cell 131 . A potentially targetable possibility is using inhibitors for the kinase(s) that phosphorylate BID and inhibit its caspase-mediated activation 132,133 . Finally, cancer cells undergoing sub-lethal caspase activity may be more sensitive than healthy tissue to additional caspase activity providing a therapeutic window for direct smallmolecule caspase activators 134 .…”

TRAIL Signaling and Synergy Mechanisms Used in TRAIL-Based Combination Therapies

“…For example, inhibiting protein kinase CK2 impairs Bid phosphorylation and enhances Bid cleavage by caspase-8 (65,66) and may be an attractive cotreatment strategy if outstanding safety tests yield satisfying results. Procaspase-8 itself can be phosphorylated by Src kinase, which impairs its binding to and activation at the DISC (67).…”

An Analysis of the Truncated Bid- and ROS-dependent Spatial Propagation of Mitochondrial Permeabilization Waves during Apoptosis

“…tBid was added into the system at mesh position 1 using a sigmoid input function that reflects experimentally determined Bid cleavage kinetics (20,21). The input function was initiated at time 0, and the local concentrations of tBid were normalized to a percentage scale, with 100% reflecting the maximum concentration expected for evenly distributed tBid.…”

“…In the modeled scenario, tBid is entered into the system at the near end of the modeled cell ( Fig. 2A), and the tBid influx was based on experimentally determined Bid cleavage kinetics (20,21). In the original reaction-diffusion model, the simulations covered a distance of 30 m to resemble typical HeLa cell sizes, and boundary conditions were implemented that prevented tBid from leaving the cell system (17).…”