A role for Jun-N-terminal kinase in anoikis; suppression by bcl-2 and crmA.
The disruption of interactions between extracellular matrix and specific cognate integrins triggers apoptosis in epithelial cells, in a process termed "anoikis." To understand anoikis, the connections between epithelial cell integrin signaling and the apoptosis-regulatory proteins are being explored. We report herein that early after detachment from matrix, epithelial cells activate Jun-N-Terminal Kinases (JNKs; alternatively known as Stress-activated Protein Kinases), which are also activated by other apoptotic stimuli. The activity of this pathway was required for anoikis. Another early response to cell suspension was the activation of the ICE-related cysteine protease, ICE/LAP3; this activation and anoikis were suppressed by the ICE-protease inhibitor, crmA. The overexpression of bcl-2 suppressed ICE/LAP3 activation as well. Surprisingly, bcl-2 and crmA attenuated the activation of JNKs following cell suspension, suggesting that the JNK pathway is regulated directly or indirectly by proteolysis. In addition, the blockage of the JNK pathway attenuated the activation of ICE/LAP3, suggesting a positive feedback loop between the ICE and JNK systems. These results indicate the following sequence of information flow in anoikis: integrins-->bcl-2/bax-->(ICE-proteases<-->JNK)-->apopt osis. Cell-cell interactions, which were previously shown to sensitize cells to anoikis, caused bcl-2 mRNA to be downregulated, a permissive event for downstream apoptotic signaling.
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Burnham Institute, La Jolla Cancer Research Center, California 92037, USA. sfrisch@ljcrf.edu
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D000818:Animals; D017209:Apoptosis; D029742:Caenorhabditis elegans Proteins; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D020170:Caspase 1; D020169:Caspases; D002450:Cell Communication; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004285:Dogs; D004789:Enzyme Activation; D004790:Enzyme Induction; D019254:Genes, bcl-2; D011905:Genes, ras; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D011506:Proteins / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D012333:RNA, Messenger / Q000235:genetics; D015843:Serpins / Q000502:physiology*; D015398:Signal Transduction; D014162:Transfection; D014764:Viral Proteins
D029742:Caenorhabditis elegans Proteins; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D015843:Serpins; D014764:Viral Proteins; C074641:interleukin-1beta-converting enzyme inhibitor; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D020169:Caspases; D003546:Cysteine Endopeptidases; C089223:ced-3 protein, C elegans; D020170:Caspase 1