17 research outputs found
Dual Mechanisms of sHA 14-1 in Inducing Cell Death through Endoplasmic Reticulum and Mitochondria
HA 14-1 is a small-molecule Bcl-2 antagonist that promotes apoptosis in
malignant cells, but its mechanism of action is not well defined. We recently
reported that HA 14-1 has a half-life of only 15 min in vitro, which led us to
develop a stable analog of HA 14-1 (sHA 14-1). The current study characterizes
its mode of action. Because of the antiapoptotic function of Bcl-2 family
proteins on the endoplasmic reticulum (ER) and mitochondria, the effect of sHA
14-1 on both organelles was evaluated. sHA 14-1 induced ER calcium release in
human leukemic cells within 1 min, followed by induction of the ER
stress-inducible transcription factor ATF4. Similar kinetics and stronger
intensity of ER calcium release were induced by the sarcoendoplasmic reticulum
Ca2+-ATPase (SERCA) inhibitor thapsigargin, accompanied by similar
kinetics and intensity of ATF4 induction. sHA 14-1 directly inhibited SERCA
enzymatic activity but had no effect on the inositol triphosphate receptor.
Evaluation of the mitochondrial pathway showed that sHA 14-1 triggered a loss
of mitochondrial transmembrane potential (Δψm) and weak caspase-9
activation, whereas thapsigargin had no effect.
(R)-4-(3-Dimethylamino-1-phenylsulfanylmethyl-propylamino)-N-{4-[4-(4′-chloro-biphenyl-2-ylmethyl)-piperazin-1-yl]-benzoyl}-3-nitrobenzenesulfonamide
(ABT-737), a well established small-molecule Bcl-2 antagonist, rapidly induced
loss of Δψm and caspase-9 activation but had no effect on the ER.
The pan-caspase inhibitor
N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone had some
protective effect on sHA 14-1-induced cell death. These collective results
suggest a unique dual targeting mechanism of sHA 14-1 on the apoptotic
resistance machinery of tumor cells that includes antiapoptotic Bcl-2 family
proteins and SERCA proteins