title: TRAIL-activated stress kinases suppress apoptosis through transcriptional upregulation of MCL-1.
abstract: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a potentially useful anticancer agent with exquisite selectivity for cancer cells. Unfortunately, many cancers show or acquire resistance to TRAIL. In this study we report that TRAIL activates a TGF-beta-activated kinase 1 --> mitogen-activated protein kinase (MAPK) kinase 3 (MKK3)/MKK6 --> p38 pathway in prostate cancer cells that transcriptionally upregulates expression of the antiapoptotic BCL-2 family member MCL-1. TRAIL alone triggered robust formation of the 'death-inducing signaling complex' (DISC), activation of the initiator caspase-8, and truncation of the BH3-only protein BID (tBID). Nevertheless, simultaneous disruption of the p38 MAPK pathway was required to suppress MCL-1 expression, thereby allowing tBID to activate the proapoptotic BCL-2 family member BAK and stimulate mitochondrial outer membrane permeabilization (MOMP). Release of the inhibitor-of-apoptosis (IAP) antagonist, Smac/DIABLO, from the intermembrane space was sufficient to promote TRAIL-induced apoptosis, whereas release of cytochrome c and activation of the apoptosome was dispensable. Even after MOMP, however, mitochondrial-generated reactive oxygen species (ROS) activated a secondary signaling pathway, involving c-Jun N-terminal kinases (JNKs), that similarly upregulated MCL-1 expression and partially rescued some cells from death. Thus, stress kinases activated at distinct steps, before and after mitochondrial injury, mediate TRAIL resistance through maintenance of MCL-1 expression.
authors.affiliation: Center for Molecular and Cellular Toxicology, Division of Pharmacology and Toxicology, College of Pharmacy, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: J K
authors.initials: JK
authors.lastname: Son
authors.forename: S
authors.initials: S
authors.lastname: Varadarajan
authors.forename: S B
authors.initials: SB
authors.lastname: Bratton
mesh_terms: D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D045744:Cell Line, Tumor; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D048371:MAP Kinase Kinase 3 / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D014158:Transcription, Genetic; D015854:Up-Regulation; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D051023:BH3 Interacting Domain Death Agonist Protein; C412403:DIABLO protein, human; D051034:Inhibitor of Apoptosis Proteins; D047908:Intracellular Signaling Peptides and Proteins; D024101:Mitochondrial Proteins; D064549:Myeloid Cell Leukemia Sequence 1 Protein; D019253:Proto-Oncogene Proteins c-bcl-2; D017382:Reactive Oxygen Species; D053221:TNF-Related Apoptosis-Inducing Ligand; D048051:p38 Mitogen-Activated Protein Kinases; D048371:MAP Kinase Kinase 3; D053181:Caspase 8