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DAP-kinase induces apoptosis by suppressing integrin activity and disrupting matrix survival signals
Won-Jing Wang1, Jean-Cheng Kuo, Chung-Chen Yao
1Institute of Molecular Medicine, College of Medicine, National Taiwan University Hospital, National Taiwan University, Taipei, Taiwan.
Abstract:
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.
Insights
Death-associated protein kinase (DAP-kinase) suppresses cell adhesion and survival signals by inhibiting integrin activity. This mechanism promotes apoptosis, partly through p53 activation, highlighting a novel role for DAP-kinase in cell death.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Death-associated protein kinase (DAP-kinase) is a serine/threonine kinase involved in apoptosis.
- The precise mechanism by which DAP-kinase promotes apoptosis remains unclear.
Purpose of the Study:
- To elucidate the mechanism of apoptosis promotion by DAP-kinase.
- To investigate the role of DAP-kinase in regulating cell adhesion and integrin signaling.
Main Methods:
- Investigated the effect of DAP-kinase on integrin-mediated cell adhesion and signal transduction.
- Utilized dominant-negative interference and enforced activation of integrin signaling pathways.
- Examined apoptosis induction in different cell lines (fibroblasts, MCF10A, BT474) under various substrate conditions (fibronectin, poly-l-lysine).
Main Results:
- DAP-kinase suppresses integrin-mediated cell adhesion and signaling via an inside-out mechanism.
- This adhesion-inhibitory effect contributes significantly to DAP-kinase-induced apoptosis.
- Enforced activation of integrin or FAK signaling abolished DAP-kinase-induced apoptosis and p53 upregulation.
Conclusions:
- DAP-kinase induces apoptosis by inhibiting integrin function and survival signals.
- This inhibition leads to the activation of a p53-dependent apoptotic pathway.
- DAP-kinase represents a key regulator linking cell adhesion dynamics to programmed cell death.