DAP kinase and DRP-1 mediate membrane blebbing and the formation of autophagic vesicles during programmed cell death

Here we review recent observations indicating the existence of redundant cell death mechanisms. We speculate that this redundancy reflects a particular evolutionary history for cellular demise. Autophagic or apoptotic elements might have been added to a primordial death mechanism, initially improving cell dismantling and later acquiring the ability to act themselves as death effectors. The resulting redundancy of cell death mechanisms has pathophysiological implications.

Section: Inhibition/replacement Of Cell Death Typesmentioning

confidence: 99%

Redundant cell death mechanisms as relics and backups

Golstein

Kroemer

2005

“…Accordingly, evidence for a proapoptotic role is largely based on its ability to induce apoptosis-like cell morphology upon overexpression. [12][13][14] We thus hypothesised that endogenous DAPK2 may under some circumstances have antiapoptotic properties and provide cancer cells with prosurvival cues.…”

mentioning

confidence: 99%

DAPK2 is a novel modulator of TRAIL-induced apoptosis

Stöcker

et al. 2014

Targeting molecules involved in TRAIL-mediated signalling has been hailed by many as a potential magic bullet to kill cancer cells efficiently, with little side effects on normal cells. Indeed, initial clinical trials showed that antibodies against TRAIL receptors, death receptor (DR)4 and DR5, are well tolerated by cancer patients. Despite efficacy issues in the clinical setting, novel approaches to trigger TRAIL-mediated apoptosis are being developed and its clinical potential is being reappraised. Unfortunately, as observed with other cancer therapies, many patients develop resistance to TRAIL-induced apoptosis and there is thus impetuous for identifying additional resistance mechanisms that may be targetable and usable in combination therapies. Here, we show that the death-associated protein kinase 2 (DAPK2) is a modulator of TRAIL signalling. Genetic ablation of DAPK2 using RNA interference causes phosphorylation of NF-jB and its transcriptional activity in several cancer cell lines. This then leads to the induction of a variety of NF-jB target genes, which include proapoptotic DR4 and DR5. DR4 and DR5 protein expression is correspondingly increased on the cell surface and this leads to the sensitisation of resistant cells to TRAILinduced killing, in a p53-independent manner. As DAPK2 is a kinase, it is imminently druggable, and our data thus offer a novel avenue to overcome TRAIL resistance in the clinic. Despite the effort and resources invested in cancer research, cancer remains a serious public health problem. Most patients are treated surgically, with chemotherapeutic drugs and/or antibodies and small molecule inhibitors. Patients generally respond well to the initial therapy but frequently develop resistance to it. This poses a challenge to their treatment and calls for alternative approaches to be developed. Indeed, much excitement was generated in the mid-1990s when tumour necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) was identified. [1][2][3][4] TRAIL is a death receptor (DR) ligand that signals through DR4 and DR5, two members of the TNF receptor family. 5-7 DR5 has two isoforms that differ by 29 amino acids and which are functionally indistinguishable. 5,8 TRAIL ligation activates primarily the extrinsic apoptotic pathway. The formation of ligand/receptor complexes leads to the assembly of a multiprotein death-inducing signalling complex (DISC), which in the case of TRAIL is typically composed of the adaptor Fasassociated death domain, caspase-8, caspase-10 and/or c-FLIP. These initiator caspases proteolytically cleave effector caspases such as caspase-3, caspase-6 and/or caspase-7 thereby activating them. This leads to the destruction of key cellular components and the appearance of typical features of apoptosis. TRAIL can also activate intrinsic apoptotic pathways via BID and thus involve mitochondria. By virtue of preferentially killing tumour cells, TRAIL is seen by many as a 'magic bullet' against cancer cells. Some cancer cells, however, are resistant, or develop resistanc...

“…6 Overexpression of DAPk leads, in some cells, to the appearance of autophagic vesicles and cell death that does not involve activation of caspases. 7 However, though it is associated with a large number of cell death scenarios, relatively few specific downstream targets of DAPk, such as direct substrates and interacting proteins, have been identified and the molecular mechanisms underlying DAPk's function are still not well defined. Also, a possible link to type-III necrotic cell death has not been studied so far.…”

mentioning

confidence: 99%

DAP kinase regulates JNK signaling by binding and activating protein kinase D under oxidative stress

Eisenberg‐Lerner

Kimchi

2007

The stress-activated kinase JNK mediates key cellular responses to oxidative stress. Here we show that DAP kinase (DAPk), a cell death promoting Ser/Thr protein kinase, plays a main role in oxidative stress-induced JNK signaling. We identify protein kinase D (PKD) as a novel substrate of DAPk and demonstrate that DAPk physically interacts with PKD in response to oxidative stress. We further show that DAPk activates PKD in cells and that induction of JNK phosphorylation by ectopically expressed DAPk can be attenuated by knocking down PKD expression or by inhibiting its catalytic activity. Moreover, knockdown of DAPk expression caused a marked reduction in JNK activation under oxidative stress, indicating that DAPk is indispensable for the activation of JNK signaling under these conditions. Finally, DAPk is shown to be required for cell death under oxidative stress in a process that displays the characteristics of caspase-independent necrotic cell death. Taken together, these findings establish a major role for DAPk and its specific interaction with PKD in regulating the JNK signaling network under oxidative stress.