Glycogen Synthase Kinase-3β Mediates Endoplasmic Reticulum Stress-Induced Lysosomal Apoptosis in Leukemia
- Institute of Basic Medical Sciences (W.-C.H., Y.-S.L., C.-Y.W., C.-F.L.), Graduate Institute of Clinical Medicine (W.-C.H., C.-Y.W., W.-H.C., C.-F.L.), Center for Gene Regulation and Signal Transduction Research (Y.-S.L.), and Departments of Microbiology and Immunology (W.-C.H., Y.-S.L., C.-L.C., C.-Y.W., C.-F.L.), and Internal Medicine (W.-H.C.), National Cheng Kung University Medical College, Tainan, Taiwan
- Address correspondence to:
Dr. Chiou-Feng Lin, Institute of Clinical Medicine, National Cheng Kung University Medical College, Tainan 701, Taiwan. E-mail: cflin{at}mail.ncku.edu.tw
Abstract
Glycogen synthase kinase (GSK)-3β may modulate endoplasmic reticulum (ER) stress-induced apoptosis; however, the mechanism remains unclear. Our data showed that human monocytic leukemia/lymphoma U937 and acute myeloid leukemia HL-60, but not chronic myeloid leukemia K562, cells were susceptible to apoptosis induced by ER stressor tunicamycin, a protein glycosylation inhibitor. Tunicamycin caused early activation of caspase-2, -3, -4, and -8, followed by apoptosis, whereas caspase-9 was slowly activated. Inhibiting caspase-2 reduced activation of caspase-8 and -3 but had no effect on caspase-4. Tunicamycin induced apoptosis independently of the mitochondrial pathway but caused lysosomal destabilization followed by lysosomal membrane permeabilization (LMP), cathepsin B relocation from lysosomes to the cytosol, and caspase-8 and -3 activation. It is notable that caspase-2 mediated lysosomal destabilization. Inhibiting GSK-3β comprehensively reduced lysosomal apoptosis after caspase-2 inhibition. Unlike U937 and HL-60 cells, K562 cells showed nonresponsive ER stress and failure of activation of GSK-3β and caspase-2 in response to tunicamycin. Activating GSK-3β caused K562 cells to be susceptible to tunicamycin-induced apoptosis. Taken together, we show that GSK-3β exhibits a mechanism of ER stress-induced lysosomal apoptosis in leukemia involving caspase-2-induced LMP and cathepsin B relocation, which result in caspase-8 and -3 activation.
Footnotes
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This work was supported by the National Science Council, Taiwan [Grant NSC 96-2320-B-006-018-MY3]; and the National Cheng Kung University, Taiwan [Landmark Project C020].
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doi:10.1124/jpet.108.148122.
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ABBREVIATIONS: ER, endoplasmic reticulum; UPR, unfolded protein response; CHOP, CCAAT/enhancer-binding protein homologous protein; LMP, lysosomal membrane permeabilization; GSK, glycogen synthase kinase; Z-FA-fmk, benzyloxycarbonyl-Phe-Ala-fluoromethyl ketone; pepstatin A, Isovalery-Val-Val-Sta-Ala-Sta; SB415286, 3-[(3-chloro-4-hydroxyphenyl)amino]-4-(2-nitrophenyl)-1H-pyrrol-2,5-dione; LY294002, 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one hydrochloride; DMSO, dimethyl sulfoxide; DAPI, 4,6-diamidino-2-phenylindole; PI, propidium iodide; AO, acridine orange; Z-VDVAD-fmk, benzyloxycarbonyl-Val-Asp(Ome)-Val-Ala-Asp(Ome)-fluoromethyl ketone; Z-IETD-fmk, benzyloxycarbonyl-Ile-Glu(Ome)-Thr-Asp(Ome)-fluoromethyl ketone; Z-VAD-fmk, benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone; GRP, glucose-regulated protein; PBS, phosphate-buffered saline; HIAP2, human inhibitor of apoptosis 2; PP2A, protein phosphatase 2A; 17-AAG, 17-(allylamino)-17-demethoxygeldanamycin.
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The online version of this article (available at http://Jpet.Aspetjournals.Org) contains supplemental material.
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- Received October 30, 2008.
- Accepted January 30, 2009.
- The American Society for Pharmacology and Experimental Therapeutics
