Expression of death-associated protein kinase and recruitment to the tumor necrosis factor signaling pathway following brief seizures

Dingxian pill alleviates hippocampal neuronal apoptosis in epileptic mice through TNF-α/TNFR1 signaling pathway inhibition

ETHNOPHARMACOLOGICAL RELEVANCE

Dingxian Pill (DXP), a famous traditional Chinese medicine prescription, and has been widely proven to have positive therapeutic effects on "Xianzheng" (the name of epilepsy in ancient China). However, the anti-epileptic molecular mechanisms of DXP are not yet fully understood and remain to be further investigated.

AIM OF THE STUDY

To elucidate the molecular mechanism of DXP's improvement in epileptic neuronal loss, damage and apoptosis by regulating TNF-α/TNFR1 signaling pathway.

MATERIALS AND METHODS

Sixty Kunming mice were randomly divided in 6 groups: control group (equal volume of normal saline), model group (180 mg kg-1 pilocarpine hydrochloride - used to establish the epilepsy animal model), carbamazepine group (30 mg kg-1), and low, medium, and high-dose Dingxian Pill groups (4.08, 8.16, and 16.32 g kg-1, respectively - oral administration once daily for 2 weeks). Successful establishment of the epileptic mouse model was monitored with electroencephalography. Pathological changes in hippocampal tissue were analyzed with hematoxylin-eosin staining. Hippocampal neuronal apoptosis was analyzed with TUNEL staining. TNF-α, TNFR1, TRADD, FADD, and caspase-8 mRNA and protein expression levels in hippocampal tissue were analyzed with real-time quantitative polymerase chain reaction, immunohistochemistry, and Western blot, respectively. Cleaved caspase-8 protein levels in hippocampal tissue were measured with immunohistochemistry and Western blot.

RESULTS

Compared to control, the model group showed an increase in continuous epileptic discharge waves on EEG, a damaged hippocampal neuron morphological structure, increased hippocampal neuronal apoptosis, and significantly increased TNF-α, TNFR1, TRADD, FADD, and caspase-8 mRNA and protein levels, and increased caspase-8 cleavage (P < 0.05). Compared to the model group, the carbamazepine group as well as the low-, medium-, and high-dose Dingxian Pill groups showed decreased epileptic discharges on EEG, an obvious hippocampal neuron morphological structure restoration, varying degrees of attenuated hippocampal neuronal apoptosis, and significantly decreased TNF-α, TNFR1, TRADD, FADD, and caspase-8 mRNA and protein levels as well as decreased caspase-8 cleavage (P < 0.05).

CONCLUSIONS

Dingxian Pill exerts an anti-epileptic effect through inhibition of TNF-α/TNFR1 signaling pathway-mediated apoptosis in hippocampal neurons.

Ablation of Death-Associated Protein Kinase 1 Changes the Transcriptomic Profile and Alters Neural-Related Pathways in the Brain

Death-associated protein kinase 1 (DAPK1), a Ca2+/calmodulin-dependent serine/threonine kinase, mediates various neuronal functions, including cell death. Abnormal upregulation of DAPK1 is observed in human patients with neurological diseases, such as Alzheimer’s disease (AD) and epilepsy. Ablation of DAPK1 expression and suppression of DAPK1 activity attenuates neuropathology and behavior impairments. However, whether DAPK1 regulates gene expression in the brain, and whether its gene profile is implicated in neuronal disorders, remains elusive. To reveal the function and pathogenic role of DAPK1 in neurological diseases in the brain, differential transcriptional profiling was performed in the brains of DAPK1 knockout (DAPK1-KO) mice compared with those of wild-type (WT) mice by RNA sequencing. We showed significantly altered genes in the cerebral cortex, hippocampus, brain stem, and cerebellum of both male and female DAPK1-KO mice compared to those in WT mice, respectively. The genes are implicated in multiple neural-related pathways, including: AD, Parkinson’s disease (PD), Huntington’s disease (HD), neurodegeneration, glutamatergic synapse, and GABAergic synapse pathways. Moreover, our findings imply that the potassium voltage-gated channel subfamily A member 1 (Kcna1) may be involved in the modulation of DAPK1 in epilepsy. Our study provides insight into the pathological role of DAPK1 in the regulatory networks in the brain and new therapeutic strategies for the treatment of neurological diseases.

Regulation of DAPK1 by Natural Products: An Important Target in Treatment of Stroke

Stroke is a sudden neurological disorder that occurs due to impaired blood flow to an area of the brain. Stroke can be caused by the blockage or rupture of a blood vessel in the brain, called ischemic stroke and hemorrhagic stroke, respectively. Stroke is more common in men than women. Atrial fibrillation, hypertension, kidney disease, high cholesterol and lipids, genetic predisposition, inactivity, poor nutrition, diabetes mellitus, family history and smoking are factors that increase the risk of stroke. Restoring blood flow by repositioning blocked arteries using thrombolytic agents or endovascular therapy are the most effective treatments for stroke. However, restoring circulation after thrombolysis can cause fatal edema or intracranial hemorrhage, and worsen brain damage in a process known as ischemia-reperfusion injury. Therefore, there is a pressing need to find and develop more effective treatments for stroke. In the past, the first choice of treatment was based on natural compounds. Natural compounds are able to reduce the symptoms and reduce various diseases including stroke that attract the attention of the pharmaceutical industry. Nowadays, as a result of the numerous studies carried out in the field of herbal medicine, many useful and valuable effects of plants have been identified. The death-associated protein kinase (DAPK) family is one of the vital families of serine/threonine kinases involved in the regulation of some biological functions in human cells. DAPK1 is the most studied kinase within the DAPKs family as it is involved in neuronal and recovery processes. Dysregulation of DAPK1 in the brain is involved in the developing neurological diseases such as stroke. Natural products can function in a variety of ways, including reducing cerebral edema, reducing brain endothelial cell death, and inhibiting TNFα and interleukin-1β (IL-1β) through regulating the DAPK1 signal against stroke. Due to the role of DAPK1 in neurological disorders, the aim of this article was to investigate the role of DAPK1 in stroke and its modulation by natural compounds.

Blocking ERK-DAPK1 Axis Attenuates Glutamate Excitotoxicity in Epilepsy

Glutamate excitotoxicity induces neuronal cell death during epileptic seizures. Death-associated protein kinase 1 (DAPK1) expression is highly increased in the brains of epilepsy patients; however, the underlying mechanisms by which DAPK1 influences neuronal injury and its therapeutic effect on glutamate excitotoxicity have not been determined. We assessed multiple electroencephalograms and seizure grades and performed biochemical and cell death analyses with cellular and animal models. We applied small molecules and peptides and knocked out and mutated genes to evaluate the therapeutic efficacy of kainic acid (KA), an analog of glutamate-induced neuronal damage. KA administration increased DAPK1 activity by promoting its phosphorylation by activated extracellular signal-regulated kinase (ERK). DAPK1 activation increased seizure severity and neuronal cell death in mice. Selective ERK antagonist treatment, DAPK1 gene ablation, and uncoupling of DAPK1 and ERK peptides led to potent anti-seizure and anti-apoptotic effects in vitro and in vivo. Moreover, a DAPK1 phosphorylation-deficient mutant alleviated glutamate-induced neuronal apoptosis. These results provide novel insight into the pathogenesis of epilepsy and indicate that targeting DAPK1 may be a potential therapeutic strategy for treating epilepsy.

Inhibition of Death-associated Protein Kinase 1 protects against Epileptic Seizures in mice

Epilepsy is a chronic encephalopathy and one of the most common neurological disorders. Death-associated protein kinase 1 (DAPK1) expression has been shown to be upregulated in the brains of human epilepsy patients compared with those of normal subjects. However, little is known about the impact of DAPK1 on epileptic seizure conditions. In this study, we aim to clarify whether and how DAPK1 is regulated in epilepsy and whether targeting DAPK1 expression or activity has a protective effect against epilepsy using seizure animal models. Here, we found that cortical and hippocampal DAPK1 activity but not DAPK1 expression was increased immediately after convulsive pentylenetetrazol (PTZ) exposure in mice. However, DAPK1 overexpression was found after chronic low-dose PTZ insults during the kindling paradigm. The suppression of DAPK1 expression by genetic knockout significantly reduced PTZ-induced seizure phenotypes and the development of kindled seizures. Moreover, pharmacological inhibition of DAPK1 activity exerted rapid antiepileptic effects in both acute and chronic epilepsy mouse models. Mechanistically, PTZ stimulated the phosphorylation of NR2B through DAPK1 activation. Combined together, these results suggest that DAPK1 regulation is a novel mechanism for the control of both acute and chronic epilepsy and provide new therapeutic strategies for the treatment of human epilepsy.

Tumor suppressor death-associated protein kinase 1 inhibits necroptosis by p38 MAPK activation

Death-associated protein kinase 1 (DAPK1, DAPk, DAPK) is known for its involvement in apoptosis and autophagy-associated cell death. Here, we identified an unexpected function of DAPK1 in suppressing necroptosis. DAPK1-deficiency renders macrophages and dendritic cells susceptible to necroptotic death. We also observed an inhibitory role for DAPK1 in necroptosis in HT-29 cells, since knockdown or knockout of DAPK1 in such cells increased their sensitivity to necroptosis. Increased necroptosis was associated with enhanced formation of the RIPK1-RIPK3-MLKL complex in these DAPK1-deficient cells. We further found that DAPK1-deficiency led to decreased MAPK activated kinase 2 (MK2) activation and reduced RIPK1 S321 phosphorylation, with this latter representing a critical step controlling necrosome formation. Most TNF signaling pathways, including ERK, JNK, and AKT, were not regulated by DAPK. In contrast, DAPK bound p38 MAPK and selectively promoted p38 MAPK activation, resulting in enhanced MK2 phosphorylation. Our results reveal a novel role for DAPK1 in inhibiting necroptosis and illustrate an unexpected selectivity for DAPK1 in promoting p38 MAPK-MK2 activation. Importantly, our study suggests that modulation of necroptosis and p38/MK2-mediated inflammation may be achieved by targeting DAPK1.

Metformin and trimetazidine ameliorate diabetes-induced cognitive impediment in status epileptic rats

Patients with diabetes and epilepsy are more prone to cognitive impairment, dementia, and even Alzheimer's disease. Diabetes-induced inflammatory process is one of the main contributing factors; however, the impact on seizure is not clear. The current study is aimed to examine the role of metformin and trimetazidine in the reduction of neuronal damage caused by inflammatory mediators and apoptotic factors in diabetic epileptic rodent model. Diabetic epileptic rats received orally either metformin (100 mg/kg) or trimetazidine (10 mg/kg) for 3 weeks exhibited reduced cognitive function and ameliorated the disturbed brain neurotransmission. Besides, they improved both the inflammatory status and the histopathologic alterations. Administration of metformin or trimetazidine ameliorated the deterioration in cognitive function in Morris water maze (MWM) and reduced seizure score. Furthermore, brain neurotransmitters glutamate and γ-aminobutyric acid (GABA) were reverted back to their normal values. Both treatments reduced the rise in inflammatory cytokines interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), apoptotic markers nuclear factor-κB (NF-κB) and caspase-3, and improved the pathological photomicrograph of the hippocampus of diabetic epileptic rats. Such effects were closely correlated to the observed increase in the adenosine triphosphate and adenosine diphosphate (ATP/ADP) ratio and reduction of death-associated protein (DAP) and mammalian target of rapamycin (mTOR). In conclusion, the current study shed light on the potential neuroprotective role of metformin and trimetazidine in the amelioration of cognitive function via hindering inflammatory processes in diabetic epileptic rats.

Novel Functions of Death-Associated Protein Kinases through Mitogen-Activated Protein Kinase-Related Signals

Death associated protein kinase (DAPK) is a calcium/calmodulin-regulated serine/threonine kinase; its main function is to regulate cell death. DAPK family proteins consist of DAPK1, DAPK2, DAPK3, DAPK-related apoptosis-inducing protein kinases (DRAK)-1 and DRAK-2. In this review, we discuss the roles and regulatory mechanisms of DAPK family members and their relevance to diseases. Furthermore, a special focus is given to several reports describing cross-talks between DAPKs and mitogen-activated protein kinases (MAPK) family members in various pathologies. We also discuss small molecule inhibitors of DAPKs and their potential as therapeutic targets against human diseases.

MutY DNA Glycosylase Protects Cells From Tumor Necrosis Factor Alpha-Induced Necroptosis

Numerous studies have implied that mutY DNA glycosylase (MYH) is involved in the repair of post-replicative mispairs and plays a critical role in the base excision repair pathway. Recent in vitro studies have shown that MYH interacts with tumor necrosis factor receptor type 1-associated death domain (TRADD), a key effector protein of tumor necrosis factor receptor-1 (TNFR1) signaling. The association between MYH and TRADD is reversed during tumor necrosis factor alpha (TNF-α)- and camptothecin (CPT)-induced apoptosis, and enhanced during TNF-α-induced survival. After investigating the role of MYH interacts with various proteins following TNF-α stimulation, here, we focus on MYH and TRADD interaction functions in necroptosis and its effects to related proteins. We report that the level of the MYH and TRADD complex was also reduced during necroptosis induced by TNF-α and zVAD-fmk. In particular, we also found that MYH is a biologically important necrosis suppressor. Under combined TNF-α and zVAD-fmk treatment, MYH-deficient cells were induced to enter the necroptosis pathway but primary mouse embryonic fibroblasts (MEFs) were not. Necroptosis in the absence of MYH proceeds via the inactivation of caspase-8, followed by an increase in the formation of the kinase receptor- interacting protein 1 (RIP1)-RIP3 complex. Our results suggested that MYH, which interacts with TRADD, inhibits TNF-α necroptotic signaling. Therefore, MYH inactivation is essential for necroptosis via the downregulation of caspase-8. J. Cell. Biochem. 118: 1827-1838, 2017. © 2017 Wiley Periodicals, Inc.

DAPK1 Signaling Pathways in Stroke: from Mechanisms to Therapies

Death-associated protein kinase 1 (DAPK1), a Ca²⁺/calmodulin (CaM)-dependent serine/threonine protein kinase, plays important roles in diverse apoptosis pathways not only in tumor suppression but also in neuronal cell death. The requirement of DAPK1 catalytic activity for its proposed cell functions and the elevation of catalytic activity of DAPK1 in injured neurons in models of neurological diseases, such as ischemia and epilepsy, validate that DAPK1 can be taken as a potential therapeutic target in these diseases. Recent studies show that DAPK1-NR2B, DAPK1-DANGER, DAPK1-p53, and DAPK1-Tau are currently known pathways in stroke-induced cell death, and blocking these cascades in an acute treatment effectively reduces neuronal loss. In this review, we focus on the role of DAPK1 in neuronal cell death after stroke. We hope to provide exhaustive summaries of relevant studies on DAPK1 signals involved in stroke damage. Therefore, disrupting DAPK1-relevant cell death pathway could be considered as a promising therapeutic approach in stroke.

Death Associated Protein Kinase 1 (DAPK1): A Regulator of Apoptosis and Autophagy

Death-Associated Protein Kinase 1 (DAPK1) belongs to a family of five serine/threonine (Ser/Thr) kinases that possess tumor suppressive function and also mediate a wide range of cellular processes, including apoptosis and autophagy. The loss and gain-of–function of DAPK1 is associated with various cancer and neurodegenerative diseases respectively. In recent years, mechanistic studies have broadened our knowledge of the molecular mechanisms involved in DAPK1-mediated autophagy/apoptosis. In the present review, we have discussed the structural information and various cellular functions of DAPK1 in a comprehensive manner.

Protein engineering strategies with potential applications for altering clinically relevant cellular pathways at the protein level

All diseases can be fundamentally viewed as the result of malfunctioning cellular pathways. Protein engineering offers the potential to develop new tools that will allow these dysfunctional pathways to be better understood, in addition to potentially providing new routes to restore proper function. Here we discuss different approaches that can be used to change the intracellular activity of a protein by intervening at the protein level: targeted protein sequestration, protein recruitment, protein degradation, and selective inhibition of binding interfaces. The potential of each of these tools to be developed into effective therapeutic treatments will also be discussed, along with any major barriers that currently block their translation into the clinic.

Identification of Novel Death-Associated Protein Kinase 2 Interaction Partners by Proteomic Screening Coupled with Bimolecular Fluorescence Complementation

Death-associated protein kinase 2 (DAPK2) is a Ca(2+)/calmodulin-dependent Ser/Thr kinase that possesses tumor-suppressive functions and regulates programmed cell death, autophagy, oxidative stress, hematopoiesis, and motility. As only few binding partners of DAPK2 have been determined, the molecular mechanisms governing these biological functions are largely unknown. We report the identification of 180 potential DAPK2 interaction partners by affinity purification-coupled mass spectrometry, 12 of which are known DAPK binding proteins. A small subset of established and potential binding proteins detected in this screen was further investigated by bimolecular fluorescence complementation (BiFC) assays, a method to visualize protein interactions in living cells. These experiments revealed that α-actinin-1 and 14-3-3-β are novel DAPK2 binding partners. The interaction of DAPK2 with α-actinin-1 was localized at the plasma membrane, resulting in massive membrane blebbing and reduced cellular motility, whereas the interaction of DAPK2 with 14-3-3-β was localized to the cytoplasm, with no impact on blebbing, motility, or viability. Our results therefore suggest that DAPK2 effector functions are influenced by the protein's subcellular localization and highlight the utility of combining mass spectrometry screening with bimolecular fluorescence complementation to identify and characterize novel protein-protein interactions.

miRNA-26b Overexpression in Ulcerative Colitis-associated Carcinogenesis

BACKGROUND

Longstanding ulcerative colitis (UC) bears a high risk for development of UC-associated colorectal carcinoma (UCC). The inflammatory microenvironment influences microRNA expression, which in turn deregulates target gene expression. microRNA-26b (miR-26b) was shown to be instrumental in normal tissue growth and differentiation. Thus, we aimed to investigate the impact of miR-26b in inflammation-associated colorectal carcinogenesis.

METHODS

Two different cohorts of patients were investigated. In the retrospective group, a tissue microarray with 38 samples from 17 UC/UCC patients was used for miR-26b in situ hybridization and quantitative reverse transcription polymerase chain reaction analyses. In the prospective group, we investigated miR-26b expression in 25 fresh-frozen colon biopsies and corresponding serum samples of 6 UC and 15 non-UC patients, respectively. In silico analysis, Ago2-RNA immunoprecipitation, luciferase reporter assay, quantitative reverse transcription polymerase chain reaction examination, and miR-26b mimic overexpression were employed for target validation.

RESULTS

miR-26b expression was shown to be upregulated with disease progression in tissues and serum of UC and UCC patients. Using miR-26b and Ki-67 expression levels, an UCC was predicted with high accuracy. We identified 4 novel miR-26b targets (DIP1, MDM2, CREBBP, BRCA1). Among them, the downregulation of the E3 ubiquitin ligase DIP1 was closely related to death-associated protein kinase stabilization along the normal mucosa-UC-UCC sequence. In silico functional pathway analysis revealed that the common cellular pathways affected by miR-26b are highly related to cancerogenesis and the development of gastrointestinal diseases.

CONCLUSIONS

We suggest that miR-26b could serve as a biomarker for inflammation-associated processes in the gastrointestinal system. Because miR-26b expression is downregulated in sporadic colon cancer, it could discriminate between UCC and the sporadic cancer type.

Functional interaction between hMYH and hTRADD in the TNF-α-mediated survival and death pathways of HeLa cells

The tumor necrosis factor (TNF) signaling pathway is a classical immune system pathway that plays a key role in regulating cell survival and apoptosis. The TNF receptor-associated death domain (TRADD) protein is recruited to the death domain of TNF receptor 1 (TNFR1), where it interacts with TNF receptor-associated factor 2 (TRAF2) and receptor-interacting protein (RIP) for the induction of apoptosis, necrosis, nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB), and mitogen-activated protein (MAP) kinase activation. In this study, we found that the human MutY homolog (hMYH) interacted with human TRADD (hTRADD) via the C-terminal domain of hMYH. Moreover, under conditions promoting TNF-α-induced cell death or survival in HeLa cells, this interaction was weakened or enhanced, respectively. The interaction between hMYH and hTRADD was important for signaling pathways mediated by TNF-α. Our results also suggested that the hTRADD-hMYH association was involved in the nuclear translocation of NFκB and formation of the TNFR1-TRADD complex. Thus, this study identified a novel mechanism through which the hMYH-hTRADD interaction may affect the TNF-α signaling pathway.

IMPLICATIONS

In HeLa cells, the hTRADD-hMYH interaction functioned in both cell survival and apoptosis pathways following TNF-α stimulation.

Death-associated protein kinase: A molecule with functional antagonistic duality and a potential role in inflammatory bowel disease (Review)

The cytoskeleton-associated serine/threonine kinase death-associated protein kinase (DAPK) has been described as a cancer gene chameleon with functional antagonistic duality in a cell type and context specific manner. The broad range of interaction partners and substrates link DAPK to inflammatory processes especially in the gut. Herein we summarize our knowledge on the role of DAPK in different cell types that play a role under inflammatory conditions in the gut. Besides some promising experimental data suggesting DAPK as an interesting drug target in inflammatory bowel disease there are many open questions regarding direct evidence for a role of DAPK in intestinal inflammation.

Evaluating DAPK as a therapeutic target

Death associated protein kinase 1 (DAPK) is an important serine/theoreine kinase involved in various cellular processes such as apoptosis, autophagy and inflammation. DAPK expression and activity are misregulated in multiple diseases including cancer, neuronal death, stoke, et al. Methylation of the DAPK gene is common in many types of cancer and can lead to loss of DAPK expression. In this review, we summarize the pathological status and functional roles of DAPK in disease and compare the published reagents that can manipulate the expression or activity of DAPK. The pleiotropic functions of DAPK make it an intriguing target and the barriers and opportunities for targeting DAPK for future clinical application are discussed.

Regulation of inflammation by DAPK

Death-associated protein kinase (DAPK) is a tumor suppressor and negatively regulates several activation signals. Consistent with its potential anti-inflammatory activity, DAPK promotes the formation of IFN-γ-activated inhibitor of translation (GAIT) complex that suppresses the translation of selected inflammatory genes. DAPK has been found to inhibit tumor necrosis factor-α (TNF-α)- or lipopolysaccharides (LPS)-induced NF-κB activation and pro-inflammatory cytokine expression. Inflammation is always associated with T cell activation, while DAPK attenuates T cell activation by a selective suppression in T cell receptor-triggered NF-κB activation. Recent studies, however, also reveal a contribution of DAPK to pro-inflammatory processes. DAPK is shown to mediate pro-inflammatory signaling downstream of TNF-α, LPS, IL-17, or IL-32. In addition, DAPK is required for the full formation of NLRP3 inflammasome, essential for the generation of IL-1β and IL-18. These results suggest the complicated role of DAPK in the regulation of inflammation that is likely dependent on cell types and environmental cues.

Role of DAPK in neuronal cell death

Neuronal cell death happens as a result of the normal physiological process that occurs during development, or as part of the pathological process that occurs during disease. Death-associated protein kinase (DAPK) is an intracellular protein that mediates cell death by its serine/threonine kinase activity, and transmits apoptotic cell death signals in various cells, including neurons. DAPK is elevated in injured neurons in acute models of injury such as ischemia and seizure. The absence of DAPK has been shown to protect neurons from a wide variety of acute toxic insults. Moreover, DAPK also regulates neuronal cell death during central nervous system development. Neurons are initially overproduced in the developing nervous system, following which approximately one-half of the original cell population dies. This "naturally-occurring" or "programmed" cell death is essential for the construction of the developing nervous system. In this review, we focus on the role of DAPK in neuronal cell death after neuronal injury. The participation of DAPK in developmental neuronal death is also explained.

Mice Lacking Functional Fas Death Receptors Are Protected from Kainic Acid-Induced Apoptosis in the Hippocampus

The Fas receptor (FasR)/Fas ligand (FasL) system plays a significant role in the process of neuronal loss in neurological disorders. Thus, in the present study, we used a real-time PCR array focused apoptosis (Mouse Apoptosis RT(2) PCR Array) to study the role of the Fas pathway in the apoptotic process that occurs in a kainic acid (KA) mice experimental model. In fact, significant changes in the transcriptional activity of a total of 23 genes were found in the hippocampus of wild-type C57BL/6 mice after 12 h of KA treatment compared to untreated mice. Among the up-regulated genes, we found key factors involved in the extrinsic apoptotic pathway, such as tnf, fas and fasL, and also in caspase genes (caspase -4, caspase-8 and caspase-3). To discern the importance of the FasR/FasL pathway, mice lacking the functional Fas death receptor (lpr) were also treated with KA. After 24 h of neurotoxin treatment, lpr mice exhibited a reduced number of apoptotic positive cells, determined by the terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) method in different regions of the hippocampus, when compared to wild-type mice. In addition, treatment of lpr mice with KA did not produce significant changes in the transcriptional activity of genes related to apoptosis in the hippocampus, either in the fas and fas ligand genes or in caspase-4 and caspase-8 and the executioner caspase-3 genes, as occurred in wild-type C57BL/6 mice. Thus, these data provide direct evidence that Fas signalling plays a key role in the induction of apoptosis in the hippocampus following KA treatment, making the inhibition of the death receptor pathway a potentially suitable target for excitotoxicity neuroprotection in neurological conditions such as epilepsy.

Rapid and reversible knockdown of endogenous proteins by peptide-directed lysosomal degradation

Rapid and reversible methods for altering the level of endogenous proteins are critically important for studying biological systems and developing therapeutics. Here, we describe a membrane permeable targeting peptide-based method that rapidly and reversibly knocks down endogenous proteins through chaperone-mediated autophagy in vitro and in vivo. We demonstrated the specificity, efficacy and generalizability of the method by showing efficient knockdown of various proteins including death associated protein kinase 1 (160kDa), scaffolding protein PSD-95 (95kDa) and α-synuclein (18kDa) with their respective targeting peptides in a dose-, time- and lysosomal activity-dependent manner in neuronal cultures. More significantly, we showed that when given systemically, the peptide system efficiently knocked down the targeted protein in the brain of intact rats. Our study provides a robust and convenient research tool to manipulate endogenous protein levels, and may also lead to the development of protein knockdown-based novel therapeutics for treating various human diseases.

Suppression of VEGF expression through interruption of the HIF‑1α and Akt signaling cascade modulates the anti‑angiogenic activity of DAPK in ovarian carcinoma cells

Death-associated protein kinase (DAPK) plays an important role in apoptosis regulation and has been shown to maintain antitumor and metastasis suppressor properties. In the present study, we investigated whether DAPK overexpression may mediate vascular endothelial growth factor (VEGF)/hypoxia-inducible factor-1α (HIF-1α) expression and angiogenic activity in the human carcinoma cell model system. VEGF plays a pivotal role in tumor angiogenesis and tumorigenesis. We found that DAPK significantly downregulated VEGF-induced endothelial cell proliferation, migration and tube formation as well as VEGF receptor-2 (VEGFR-2) phosphorylation in vitro. In addition, DAPK exhibited potent anti-angiogenic activity and clearly decreased the levels of VEGF and HIF-1α expression, a key regulator for angiogenesis. Notably, our results strongly indicated that DAPK can disturb VEGFR-2 transcriptional activity by inhibiting VEGFR-2 phosphorylation through the PI3K/Akt signaling cascade. Collectively, our study identified a novel function of DAPK in regulating cellular VEGF/HIF-1α activity during tumorigenesis, which may act together with its anti-angiogenic function to inhibit tumor progression.

Ubiquitin carboxy-terminal hydrolase L1 (UCH-L1) is increased in cerebrospinal fluid and plasma of patients after epileptic seizure

Background

Clinical and experimental studies have demonstrated that seizures can cause molecular and cellular responses resulting in neuronal damage. At present, there are no valid tests for assessing organic damage to the brain associated with seizure. The aim of this study was to investigate cerebrospinal fluid (CSF) and plasma concentrations of Ubiquitin carboxy-terminal hydrolase L1 (UCH-L1), a sensitive indicator of acute injury to brain neurons, in patients with tonic–clonic or partial secondarily generalized seizures due to various etiologies.

Methods

CSF and plasma concentrations of UCH-L1 were assessed in 52 patients within 48 hours after epileptic seizure and in 19 controls using ELISA assays.

Results

CSF obtained within 48 hours after seizure or status epilepticus (SE) presented significantly higher levels of UCH-L1 compared to controls (p = 0.008). Plasma UCH-L1 concentrations were negatively correlated with time to sample withdrawal. An analysis conducted using only the first 12 hours post-seizure revealed significant differences between concentrations of UCH-L1 in plasma and controls (p = 0.025). CSF and plasma concentrations were strongly correlated with age in patients with seizure, but not in control patients. Plasma UCH-L1 levels were also significantly higher in patients after recurrent seizures (n = 4) than in those after one or two seizures (p = 0.013 and p = 0.024, respectively).

Conclusion

Our results suggest that determining levels of neuronal proteins may provide valuable information on the assessment of brain damage following seizure. These data might allow clinicians to make more accurate therapeutic decisions, to identify patients at risk of progression and, ultimately, to provide new opportunities for monitoring therapy and targeted therapeutic interventions.

Death-associated proliferation kinetic in normal and transformed cells

Pyruvate kinase M2 (PKM2) may occur in both a tetrameric and a dimeric form. When the majority of PKM2 molecules are in the highly active tetrameric conformation, glucose is primarily degraded to pyruvate and lactate with the regeneration of energy. A tumor suppressor protein, death-associated protein kinase (DAPK), interacts with PKM2 protein and stabilizes PKM2 in its active tetrameric form in normal proliferating cells. However, DAPK is widely inactivated in cancer cells, leading to the loss of the active conformation of PKM2. This may render PKM2 sensitive to cellular oxidants, switching the enzyme into its inactive dimeric form. Consequently, inhibition of PKM2 after oxidative stress contributes optimal tumor growth and allows cancer cells to withstand oxidative stress.

DAPk1 inhibits NF-κB activation through TNF-α and INF-γ-induced apoptosis

Recent studies have shown DAPk as a molecular modulator induced by the second messenger, responsible for controlling cell destiny decisions, but the detailed mechanism mediating the role of DAPk1 during cell death is still not fully understood. In this present report, we attempted to characterize the effects of TNF-α and INF-γ on DAPk1 in human ovarian carcinoma cell lines, OVCAR-3. Both TNF-α and INF-γ significantly induce DAPk1 levels in a time-dependent manner. At the same time, they both arrested cell cycle progression in the G(0)-G(1) and G2/M phase, down-regulated cyclin D1, CDK4 and NF-κB expression, while also up-regulating p27 and p16 expression. Subsequently, the efficacy of the combined treatment with DAPk1 was investigated. In the presence of DAPk1, TNF-α or INF-γ-induced apoptosis was additively increased, while TNF-α or INF-γ-induced NF-κB activity was inhibited. Conversely, TNF-α or INF-γ-dependent NF-κB activity was further enhanced by the inhibition of DAPk1 with its specific siRNA. The activity of NF-κB was dependent on the level of DAPk1, indicating the requirement of DAPk1 for the activation of NF-κB. Low levels of DAPk1 expression were frequently observed in different human patient's tissue and cancer cell lines compared to normal samples. In addition, over-expression of DAPk1 from either TNF-α or INF-γ-treatment cells suppressed the anti-apoptosis protein XIAP as well as COX-2 and ICAM-1, more than control. Taken together, our data findings suggest that DAPk1 can mediate the pro-apoptotic activity of TNF-α and INF-γ via the NF-κB signaling pathways.

Death-associated protein kinase (DAPK) and signal transduction: regulation in cancer

Death-associated protein kinase (DAPK) is a pro-apoptotic serine/threonine protein kinase that is dysregulated in a wide variety of cancers. The mechanism by which this occurs has largely been attributed to promoter hypermethylation, which results in gene silencing. However, recent studies indicate that DAPK expression can be detected in some cancers, but its function is still repressed, suggesting that DAPK activity can be subverted at a post-translational level in cancer cells. This review will focus on recent data describing potential mechanisms that may alter the expression, regulation or function of DAPK.

Vulnerability of postnatal hippocampal neurons to seizures varies regionally with their maturational stage

The mechanism of status epilepticus-induced neuronal death in the immature brain is not fully understood. In the present study, we examined the contribution of caspases in our lithium-pilocarpine model of status epilepticus in 14 days old rat pups. In CA1, upregulation of caspase-8, but not caspase-9, preceded caspase-3 activation in morphologically necrotic cells. Pretreatment with a pan-caspase inhibitor provided neuroprotection, showing that caspase activation was not an epiphenomenon but contributed to neuronal necrosis. By contrast, upregulation of active caspase-9 and caspase-3, but not caspase-8, was detected in apoptotic dentate gyrus neurons, which were immunoreactive for doublecortin and calbindin-negative, two features of immature neurons. These results suggest that, in cells which are aligned in series as parts of the same excitatory hippocampal circuit, the same seizures induce neuronal death through different mechanisms. The regional level of neuronal maturity may be a determining factor in the execution of a specific death program.

Peptide combinatorial libraries identify TSC2 as a death-associated protein kinase (DAPK) death domain-binding protein and reveal a stimulatory role for DAPK in mTORC1 signaling

Death-associated protein kinase (DAPK) is a multidomain enzyme that plays a central role in autophagic and apoptotic signaling, although the protein-protein interactions regulating DAPK functions are not well defined. Peptide aptamer libraries were used to identify the tumor suppressor protein tuberin (TSC2) as a novel DAPK death domain-binding protein, and we evaluated whether DAPK is a positive or negative effector of the TSC2-regulated mammalian target of rapamycin (mTORC1) signaling pathway. Binding studies using death domain miniproteins in vitro and deletion analysis in vivo determined that the death domain of DAPK is the major site for the interaction with TSC2. Recombinant DAPK phosphorylates TSC2 in vitro, and DAPK kinase activity is stimulated by growth factor signaling. Transfection of DAPK promotes phosphorylation of TSC2 in vivo, whereas short interfering RNA-mediated attenuation of DAPK reduces growth factor-stimulated phosphorylation of TSC2. DAPK-dependent phosphorylation leads to TSC1-TSC2 complex dissociation, and consequently manipulation of DAPK by transfection or short interfering RNA demonstrated that DAPK is a positive regulator of mTORC1 in response to growth factor activation. Epistatic studies suggest that DAPK functions downstream from the RAS-MEK-ERK and phosphatidylinositol 3-kinase-AKT growth factor signaling pathways. DAPK(+/-) mouse embryo fibroblasts have attenuated mTORC1 signaling compared with DAPK+/+ counterparts, and overexpression of DAPK in DAPK(+/-) MEFs stimulates mTORC1 activity. These data uncover a novel interaction between DAPK and TSC2 proteins that has revealed a positive link between growth factor stimulation of DAPK and mTORC1 signaling that may ultimately affect autophagy, cell survival, or apoptosis.

Detection of 14-3-3zeta in cerebrospinal fluid following experimentally evoked seizures

Surrogate and peripheral (bio)markers of neuronal injury may be of value in assessing effects of seizures on the brain or epilepsy development following trauma. The presence of 14-3-3 isoforms in cerebrospinal fluid (CSF) is a diagnostic indicator of Creutzfeldt-Jakob disease but these proteins may also be present following acute neurological insults. Here, we examined neuronal and 14-3-3 proteins in CSF from rats after seizures. Seizures induced by intra-amygdala microinjection of 0.1 microg kainic acid (KA) caused damage which was mainly restricted to the ipsilateral CA3 subfield of the hippocampus. 14-3-3zeta was detected at significant levels in CSF sampled 4 h after seizures compared with near absence in control CSF. Neuron-specific nuclear protein (NeuN) was also elevated in CSF in seizure rats. CSF 14-3-3zeta levels were significantly lower in rats treated with 0.01 microg KA. These data suggest the presence of 14-3-3zeta within CSF may be a biomarker of acute seizure damage.

Distinct spatial and temporal activation of caspase pathways in neurons and glial cells after excitotoxic damage to the immature rat brain

Although cleaved caspase-3 is known to be involved in apoptotic cell death mechanisms in neurons, it can also be involved in a nonapoptotic role in astrocytes after postnatal excitotoxic injury. Here we evaluate participation of upstream pathways activating caspase-3 in neurons and glial cells, by studying the intrinsic pathway via caspase-9, the extrinsic pathway via caspase-8, and activation of the p53-dependent pathway. N-methyl-D-aspartate (NMDA) was injected intracortically in 9-day-old postnatal rats, which were sacrificed at several survival times between 4 hr postlesion (pl) and 7 days pl. We analyzed temporal and spatial expression of caspase-8, caspase-9, and p53 and correlation with neuronal and glial markers and caspase-3 activation. Caspase-9 was significantly activated at 10 hpl, strongly correlating with caspase-3. It was present mainly in damaged cortical and hippocampal neurons but was also seen in astrocytes and oligodendrocytes in layer VI and corpus callosum (cc). Caspase-8 showed a diminished correlation with caspase-3. It was present in cortical neurons at 10-72 hpl, showing layer specificity, and also in astroglial and microglial nuclei, mainly in layer VI and cc. p53 Expression increased at 10-72 hpl but did not correlate with caspase-3. p53 Was seen in neurons of the degenerating cortex and in some astrocytes and microglial cells of layer VI and cc. In conclusion, after neonatal excitotoxicity, mainly the mitochondrial intrinsic pathway mediates neuronal caspase-3 and cell death. In astrocytes, caspase-3 is not widely correlated with caspase-8, caspase-9, or p53, except in layer VI-cc astrocytes, where activation of upstream cascades occurs.

Transient receptor potential melastatin 7-like current in human head and neck carcinoma cells: role in cell proliferation

Ion channels are involved in normal physiologic processes and in the pathology of various diseases. In this study, we investigated the presence and potential function of transient receptor potential melastatin 7 (TRPM7) channels in the growth and proliferation of FaDu and SCC25 cells, two common human head and neck squamous carcinoma cell lines, using a combination of patch-clamp recording, Western blotting, immunocytochemistry, small interfering RNA (siRNA), fluorescent Ca(2+) imaging, and cell counting techniques. Although voltage-gated K(+) currents were recorded in all cells, none of FaDu cells express voltage-gated Na(+) or Ca(2+) currents. Perfusion of cells with NMDA or acidic solution did not activate inward currents, indicating a lack of NMDA receptor and acid-sensing channels. Lowering extracellular Ca(2+), however, induced a large nondesensitizing current reminiscent of Ca(2+)-sensing cation current or TRPM7 current previously described in other cells. This Ca(2+)-sensing current can be inhibited by Gd(3+), 2-aminoethoxydiphenyl borate (2-APB), or intracellular Mg(2+), consistent with the TRPM7 current being activated. Immunocytochemistry, Western blot, and reverse transcription-PCR detected the expression of TRPM7 protein and mRNA in these cells. Transfection of FaDu cells with TRPM7 siRNA significantly reduced the expression of TRPM7 mRNA and protein as well as the amplitude of the Ca(2+)-sensing current. Furthermore, we found that Ca(2+) is critical for the growth and proliferation of FaDu cells. Blockade of TRPM7 channels by Gd(3+) and 2-APB or suppression of TRPM7 expression by siRNA inhibited the growth and proliferation of these cells. Similar to FaDu cells, SCC25 cells also express TRPM7-like channels. Suppressing the function of these channels inhibited the proliferation of SCC25 cells.

Neuroprotective strategies to avert seizure-induced neurodegeneration in epilepsy

Neurodegeneration in limbic circuits is a hallmark feature of chronic temporal lobe epilepsy (TLE). Studies in experimental animal models and human patients indicate that seizure-induced neuronal injury involves some active, as well as passive cell death processes. Experimental approaches that inhibit active steps in cell death programs have been shown to reduce neuronal cell death and sclerosis, but not to prevent epileptogenesis in animal models of TLE. These findings suggest that we need additional research using both animal models and brain slices from human patients to understand the pathological mechanisms underlying seizure generation. Such comparative studies will also aid in evaluating the potential therapeutic value of inhibiting cell death in seizure disorders.

Apoptosis signalling pathways in seizure-induced neuronal death and epilepsy

Delineating the molecular pathways underlying seizure-induced neuronal death may yield novel strategies for brain protection against prolonged or repetitive seizures. Glutamate-mediated excitotoxicity and necrosis is a primary contributing mechanism but seizures also activate programmed (apoptotic) cell death pathways. Apoptosis signalling pathways are typically initiated following perturbation of intracellular organelle function (intrinsic pathway) or by activated cell-surface-expressed death receptors (extrinsic pathway), with signalling cascades orchestrated in part by the Bcl-2 and caspase gene families. In this review, evidence for these pathways from experimental seizure modelling and clinical material from patients with intractable temporal lobe epilepsy is examined. Seizures cause mitochondrial dysfunction and activate intrinsic pathway components including pro-apoptotic Bcl-2 family proteins and caspases, processes that may be partly calcium-induced. The ER (endoplasmic reticulum) has emerged as a major intrinsic pathway trigger for apoptosis and its function may also be compromised following seizures and in epilepsy. The extrinsic, death-receptor-dependent pathway is also rapidly engaged following experimental seizures and in patient brain, supporting a previously unexpected apical role for a calcium-independent pathway. When considered alongside emerging functions of apoptosis-regulatory proteins in non-cell-death processes, including regulating intracellular calcium release and neuronal (re)structuring, apoptosis signalling pathways can be viewed as an important developing focus of research into how to obviate the deleterious impact of seizures on the brain.

Identification of a dominant negative functional domain on DAPK-1 that degrades DAPK-1 protein and stimulates TNFR-1-mediated apoptosis

DAPK-1 is a stress-activated tumor suppressor protein that plays a role in both proapoptotic or antiapoptotic signal transduction pathways. To define mechanisms of DAPK-1 protein regulation, we have determined that DAPK-1 protein has a long half-life, and therefore its activity is primarily regulated at the protein level. Changes in DAPK-1 protein levels occur by a cathepsin B-dependent pathway, prompting us to evaluate whether cathepsin B plays positive or negative role in DAPK-1 function. The transfection of p55-TNFR-1 induced complex formation between DAPK-1 and cathepsin B. Depletion of cathepsin B protein using small interfering RNA stimulated TNFR-1 dependent apoptosis. The minimal binding region on DAPK-1 for cathepsin B was mapped to amino acids 836-947. The transfection of the DAPK-1-(836-947) miniprotein acted in a dominant negative manner inducing endogenous DAPK-1 protein degradation in a TNFR-1-dependent manner. These data suggest that DAPK-1 forms a multiprotein survival complex with cathepsin B countering the rate of TNFR-1-dependent apoptosis and highlights the importance of developing DAPK-1 inhibitors as agents to sensitize cells to stress-induced apoptosis.

Death-associated protein kinase phosphorylates mammalian ribosomal protein S6 and reduces protein synthesis

Death-associated protein kinase (DAPK) is a pro-apoptotic, calcium/calmodulin-regulated protein kinase that is a drug discovery target for neurodegenerative disorders. Despite the potential profound physiological role of DAPK in neuronal function and pathophysiology, the endogenous substrate(s) of this kinase and the mechanisms via which DAPK elicits its biological action remain largely unknown. We report here that the mammalian 40S ribosomal protein S6 is a DAPK substrate. Results from immunoprecipitation experiments are consistent with endogenous DAPK being associated with endogenous S6 in rat brain. When S6 is a component of the 40S ribosomal subunit complex, DAPK selectively phosphorylates it at serine 235, one of the five sites in S6 that are phosphorylated by the S6 kinase family of proteins. The amino acid sequence flanking serine 235 matches the established pattern for DAPK peptide and protein substrates. Kinetic analyses using purified 40S subunits revealed a K(m) value of 9 microM, consistent with S6 being a potential physiological substrate of DAPK. This enzyme-substrate relationship has functional significance. DAPK suppresses translation in rabbit reticulocyte lysate, and treatment of neuroblastoma cells with a stimulator of DAPK reduces protein synthesis. In both cases, suppression of translation correlates with increased phosphorylation of S6 at serine 235. These results demonstrate that DAPK is a S6 kinase and provide evidence for a novel role of DAPK in the regulation of translation.

Sphingolipids in apoptosis, survival and regeneration in the nervous system

Simple sphingolipids such as ceramide, sphingosine and sphingosine 1-phosphate are key regulators of diverse cellular functions. Their roles in the nervous system are supported by extensive evidence derived primarily from studies in cultured cells. More recently animal studies and studies with human samples have revealed the importance of ceramide and its metabolites in the development and progression of neurodegenerative disorders. The roles of sphingolipids in neurons and glial cells are complex, cell dependent, and many times contradictory. In this review I will summarize the effects elicited by ceramide and ceramide metabolites in cells of the nervous system, in particular those effects related to cell survival and death, emphasizing the molecular mechanisms involved. I also discuss recent evidence for the implication of sphingolipids in the development and progression of certain dementias.

Control of death-associated protein kinase (DAPK) activity by phosphorylation and proteasomal degradation

Activation of death-associated protein kinase (DAPK) occurs via dephosphorylation of Ser-308 and subsequent association of calcium/calmodulin. In this study, we confirmed the existence of the alternatively spliced human DAPK-beta, and we examined the levels of DAPK autophosphorylation and DAPK catalytic activity in response to tumor necrosis factor or ceramide. It was found that DAPK is rapidly dephosphorylated in response to tumor necrosis factor or ceramide and then subsequently degraded via proteasome activity. Dephosphorylation and activation of DAPK are shown to temporally precede its subsequent degradation. This results in an initial increase in kinase activity followed by a decrease in DAPK expression and activity. The decline in DAPK expression is paralleled with increased caspase activity and cell apoptosis. These results suggest that the apoptosis regulatory activities mediated by DAPK are controlled both by phosphorylation status and protein stability.

Isoform- and subcellular fraction-specific differences in hippocampal 14-3-3 levels following experimentally evoked seizures and in human temporal lobe epilepsy

14-3-3 proteins are a family of signaling molecules involved in diverse cellular functions, which can mediate anti-apoptotic effects. Seizure-induced neuronal death may involve programmed (apoptotic) cell death pathways and is associated with a decline in brain 14-3-3 levels. Presently, we investigated the subcellular localization and effects of seizures on isoforms of 14-3-3 in rat hippocampus, and contrasted these to findings in human temporal lobe epilepsy (TLE). All brain isoforms of 14-3-3 were detected in the cytoplasmic compartment of rat hippocampus, while 14-3-3gamma and -zeta were also present in mitochondrial and microsome-enriched fractions. Focally evoked seizures in rats significantly reduced 14-3-3gamma levels within the microsome-enriched compartment at 4 h, with similar responses for 14-3-3zeta, while cytoplasm-localized 14-3-3beta, -epsilon and -eta remained unchanged. Analysis of human autopsy control hippocampus revealed similar 14-3-3 isoform expression profiles. In TLE samples, the microsome-enriched fraction also showed differences, but here 14-3-3epsilon and -zeta levels were higher than controls. TLE sample 14-3-3 isoform abundance within the cytoplasmic fraction was not different to controls. This study defines the subcellular localization of 14-3-3 isoforms in rat and human hippocampus and identifies the microsome-enriched fraction as the main site of altered 14-3-3 levels in response to acute prolonged and chronic recurrent seizures.

Activation of the caspase 8 pathway mediates seizure-induced cell death in cultured hippocampal neurons

In response to harmful stresses, cells induce programmed cell death (PCD) or apoptosis. Seizures can induce neural damage and activate biochemical pathways associated with PCD. Since seizures trigger intracellular calcium overload, it has been presumed that the intrinsic cell death pathway mediated by mitochondrial dysfunction would modulate cell death following seizures. However, previous work suggests that the extrinsic cell death pathway may initiate the damage program. Here we investigate intrinsic versus extrinsic cell death pathway activation using caspase cleavage as a marker for activation of these pathways in a rat in vitro model of seizures. Hippocampal cells, chronically treated with kynurenic acid, had kynurenic acid withdrawn to induce seizure-like activity for 40 min. Subjecting rat hippocampal cultures to seizures increased cell death and apoptosis-like DNA fragmentation using TUNEL staining. Seizure-induced cell death was blocked by both MK801 (10 microM) and CNQX (40 microM), which suggests multiple glutamate receptors regulate seizure-induced cell death. Cleavage of the initiator caspases, caspase 8 and 12 were increased 4h following seizure, and cleavage of the quintessential executioner caspase, caspase 3 was increased 4h following seizure. In contrast, caspase 9 cleavage only increased 24h following seizure. Using an affinity labeling approach to trap activated caspases in situ, we show that caspase 8 is the apical caspase activated following seizures. Finally, we show that the caspase 8 inhibitor Ac-IETD-CHO was more effective at blocking seizure-induced cell death than the caspase 9 inhibitor Ac-LEHD-CHO. Taken together, our data suggests the extrinsic cell death pathway-associated caspase 8 is activated following seizures in vitro.

Transgenic drak2 overexpression in mice leads to increased T cell apoptosis and compromised memory T cell development

Drak2 is a death-associated protein family serine-threonine kinase. Its expression and roles in the immune system were investigated in this study. According to in situ hybridization, Drak2 expression was ubiquitous at the mid-gestation stage in embryos, followed by more focal expression in various organs in the perinatal period and adulthood, notably in the thymus, spleen, lymph nodes, cerebellum, suprachiasmatic nuclei, pituitary, olfactory lobes, adrenal medulla, stomach, skin, and testes. Drak2 transgenic (Tg) mice were generated using the human beta-actin promoter. These Tg mice showed normal T cell versus B cell and CD4 versus CD8 populations in the spleen, but their spleen weight cellularity was lower in comparison with wild type mice. After TCR activation, the proliferation response in Drak2 Tg T cells was normal, although their interleukin (IL)-2 and IL-4 but not interferon-gamma production was augmented. Activated Drak2 Tg T cells demonstrated significantly enhanced apoptosis in the presence of exogenous IL-2. At the molecular level, Drak2 Tg T cells manifested a lower increase of anti-apoptotic factors during activation; such a change probably rendered the cells vulnerable to subsequent IL-2 insults. The compromised apoptosis in Drak2 Tg T cells was associated with reduced numbers of T cells with the memory cell phenotype (CD62L(lo)) and repressed secondary T cell responses in delayed type hypersensitivity. Our study demonstrates that Drak2 expresses in the T cell compartment but is not T cell-specific; it plays critical roles in T cell apoptosis and memory T cell development.

The tumor suppressor DAP-kinase links cell adhesion and cytoskeleton reorganization to cell death regulation

Death-associated protein (DAP)-kinase, an actin-cytoskeleton localized serine/threonine kinase, functions as a novel tumor suppressor and participates in a wide variety of cell death systems. Recent studies indicate that DAP-kinase elicits a potent cytoskeletal reorganization effect and is capable of modulating integrin inside-out signaling. Using this understanding of DAP-kinase protein function as a framework, we discuss the functional mechanisms of this kinase in regulating death-associated morphological and signaling events. Furthermore, a potential role of DAP-kinase to be a drug target is also discussed.

Epilepsy and apoptosis pathways

Epilepsy is a common, chronic neurologic disorder characterized by recurrent unprovoked seizures. Experimental modeling and clinical neuroimaging of patients has shown that certain seizures are capable of causing neuronal death. Such brain injury may contribute to epileptogenesis, impairments in cognitive function or the epilepsy phenotype. Research into cell death after seizures has identified the induction of the molecular machinery of apoptosis. Here, the authors review the clinical and experimental evidence for apoptotic cell death pathway function in the wake of seizure activity. We summarize work showing intrinsic (mitochondrial) and extrinsic (death receptor) apoptotic pathway function after seizures, activation of the caspase and Bcl-2 families of cell death modulators and the acute and chronic neuropathologic impact of intervening in these molecular cascades. Finally, we describe evolving data on nonlethal roles for these proteins in neuronal restructuring and cell excitability that have implications for shaping the epilepsy phenotype. This review highlights the work to date on apoptosis pathway signaling during seizure-induced neuronal death and epileptogenesis, and speculates on how emerging roles in brain remodeling and excitability have enriched the number of therapeutic strategies for protection against seizure-damage and epileptogenesis.