DAP-kinase induces apoptosis by suppressing integrin activity and disrupting matrix survival signals.
Death-associated protein kinase (DAP-kinase) is a calcium/calmodulin-dependent serine/threonine kinase, and participates in various apoptosis systems. However, its apoptosis-promoting mechanism is poorly understood. Here, we demonstrate that DAP-kinase suppresses integrin-mediated cell adhesion and signal transduction, whereas dominant-negative interference of this kinase promotes adhesion. This effect of DAP-kinase is neither a consequence of apoptosis nor a result of decreased expression of integrins. Rather, DAP-kinase downregulates integrin activity through an inside-out mechanism. We present evidence indicating that this adhesion-inhibitory effect accounts for a major mechanism of the apoptosis induced by DAP-kinase. First, in growth-arrested fibroblasts, DAP-kinase triggers apoptosis in cells plated on fibronectin, but does not affect the death of cells on poly-l-lysine. Second, in epithelial cells, DAP-kinase induces apoptosis in the anoikis-sensitive MCF10A cells, but not in the anoikis-resistant BT474 cells. Most importantly, the apoptosis-promoting effect of DAP-kinase is completely abolished by enforced activation of integrin-mediated signaling pathways from either integrin itself or its downstream effector, FAK. Finally, we show that integrin or FAK activation blocks the ability of DAP-kinase to upregulate p53. Our results indicate that DAP-kinase exerts apoptotic effects by suppressing integrin functions and integrin-mediated survival signals, thereby activating a p53-dependent apoptotic pathway.
Wang
Won-Jing
WJ
Institute of Molecular Medicine, College of Medicine, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan.
Kuo
Jean-Cheng
JC
Yao
Chung-Chen
CC
Chen
Ruey-Hwa
RH
D000590:Amino Acid Chloromethyl Ketones / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins; D001943:Breast Neoplasms / Q000378:metabolism; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002277:Carcinoma / Q000378:metabolism; D053148:Caspase 3; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology*; D002460:Cell Line; D048429:Cell Size; D002470:Cell Survival; D015853:Cysteine Proteinase Inhibitors / Q000378:metabolism; D064550:Death-Associated Protein Kinases; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism*; D017930:Genes, Reporter; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D051379:Mice; D015398:Signal Transduction / Q000502:physiology*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
D000590:Amino Acid Chloromethyl Ketones; D051017:Apoptosis Regulatory Proteins; D061945:Caspase Inhibitors; D015853:Cysteine Proteinase Inhibitors; D016023:Integrins; D016159:Tumor Suppressor Protein p53; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D064550:Death-Associated Protein Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases