Abstract
Dlk/ZIP kinase is a member of the Death Associated Protein (DAP) kinase family of pro-apoptotic serine/threonine kinases that have been implicated in regulation of apoptosis and tumour suppression. Expression of both Dlk/ZIP kinase and its interaction partner Par-4 is maintained in four medulloblastoma cell lines investigated, whereas three of seven neuroblastoma cell lines have lost expression of Par-4. Overexpression of a constitutively pro-apoptotic deletion mutant of Dlk/ZIP kinase induced significant apoptosis in D283 medulloblastoma cells. Cell death was characterized by apoptotic membrane blebbing, and a late stage during which the cells had ceased blebbing and were drastically shrunken or disrupted into apoptotic bodies. Over-expression of the anti-apoptotic Bcl-xL protein had no effect on Dlk/ZIP kinase-induced membrane blebbing, but potently inhibited Dlk/ZIP kinase-induced cytochrome c release and transition of cells to late stage apoptosis. Treatment with caspase inhibitors delayed, but did not prevent entry into late stage apoptosis. These results demonstrate that Dlk/ZIP kinase-triggered apoptosis involves the mitochondrial apoptosis pathway. However, cell death proceeded in the presence of caspase inhibitors, suggesting that Dlk/ZIP kinase is able to activate alternative cell death pathways. Alterations of signal transduction pathways leading to Dlk/ZIP kinase induced apoptosis or loss of expression of upstream activators could play important roles in tumour progression and metastasis of neural tumours.
(c) 2001 Cancer Research Campaign
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Amino Acid Chloromethyl Ketones / pharmacology
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Apoptosis / drug effects
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Apoptosis / genetics
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Apoptosis / physiology*
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Apoptosis Regulatory Proteins
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Calcium-Calmodulin-Dependent Protein Kinases
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Carrier Proteins / genetics
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Carrier Proteins / metabolism
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Caspase Inhibitors
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Cysteine Proteinase Inhibitors / pharmacology
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Cytochrome c Group / metabolism
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Death-Associated Protein Kinases
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Gene Expression Regulation, Neoplastic
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Green Fluorescent Proteins
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Humans
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Intracellular Membranes / metabolism
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Intracellular Signaling Peptides and Proteins*
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Luminescent Proteins / genetics
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Luminescent Proteins / metabolism
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Medulloblastoma / enzymology
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Medulloblastoma / genetics
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Medulloblastoma / pathology*
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Microscopy, Fluorescence
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Mitochondria / enzymology
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Mitochondria / genetics
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Mitochondria / pathology
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Mutation
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Neuroblastoma / enzymology
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Neuroblastoma / genetics
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Neuroblastoma / pathology
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Oligopeptides / pharmacology
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Proto-Oncogene Proteins c-bcl-2 / genetics
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Recombinant Fusion Proteins / genetics
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Recombinant Fusion Proteins / metabolism
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Signal Transduction
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Transfection
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Tumor Cells, Cultured
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bcl-X Protein
Substances
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Amino Acid Chloromethyl Ketones
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Apoptosis Regulatory Proteins
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BCL2L1 protein, human
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Carrier Proteins
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Caspase Inhibitors
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Cysteine Proteinase Inhibitors
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Cytochrome c Group
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Intracellular Signaling Peptides and Proteins
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Luminescent Proteins
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Oligopeptides
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Proto-Oncogene Proteins c-bcl-2
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Recombinant Fusion Proteins
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acetyl-aspartyl-glutamyl-valyl-aspartal
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bcl-X Protein
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benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone
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prostate apoptosis response-4 protein
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L 709049
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Green Fluorescent Proteins
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Death-Associated Protein Kinases
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Protein Serine-Threonine Kinases
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Calcium-Calmodulin-Dependent Protein Kinases