Mechanism of DAPK1 for Regulating Cancer Stem Cells in Thyroid Cancer.

Death-associated protein kinase 1 (DAPK1) is a calcium/calmodulin (Ca2+/CaM)-dependent serine/threonine (Ser/Thr) protein kinase and is characteristically downregulated in metastatic cancer. Several studies showed that DAPK1 is involved in both the early and late stages of cancer. DAPK1 downregulation is elaborately controlled by epigenetic, transcriptional, posttranscriptional, and posttranslational processes. DAPK1 is known to regulate not only cancer cells but also stromal cells. Recent studies showed that DAPK1 was involved not only in tumor suppression but also in epithelial-mesenchymal transition (EMT) and cancer stem cell (CSC) formation in colon and thyroid cancers. CSCs are major factors in determining cancer aggressiveness in cancer metastasis and treatment prognosis by influencing EMT. However, the molecular mechanism involved in the regulation of cancer cells by DAPK1 remains unclear. In particular, little is known about the existence of CSCs and how they are regulated in papillary thyroid carcinoma (PTC) among thyroid cancers. In this review, we describe the molecular mechanism of CSC regulation by DAPK1 in PTC progression.

In Silico Prediction of Quercetin Analogs for Targeting Death-Associated Protein Kinase 1 (DAPK1) Against Alzheimer's Disease.

Alzheimer's Disease (AD) is a progressive neurodegenerative disorder that greatly affects the health and life quality of the elderly population. Existing drugs mainly alleviate symptoms but fail to halt disease progression, underscoring the urgent need for the development of novel drugs. Based on the neuroprotective effects of flavonoid quercetin in AD, this study was designed to identify potential AD-related targets for quercetin and perform in silico prediction of promising analogs for the treatment of AD. Database mining suggested death-associated protein kinase 1 (DAPK1) as the most promising AD-related target for quercetin among seven protein candidates. To achieve better biological effects for the treatment of AD, we devised a series of quercetin analogs as ligands for DAPK1, and molecular docking analyses, absorption, distribution, metabolism, and excretion (ADME) predictions, as well as molecular dynamics (MD) simulations, were performed. The energy for drug-protein interaction was predicted and ranked. As a result, quercetin-A1a and quercetin-A1a1 out of 19 quercetin analogs exhibited the lowest interaction energy for binding to DAPK1 than quercetin, and they had similar dynamics performance with quercetin. In addition, quercetin-A1a and quercetin-A1a1 were predicted to have better water solubility. Thus, quercetin-A1a and quercetin-A1a1 could be promising agents for the treatment of AD. Our findings paved the way for further experimental studies and the development of novel drugs.

Quantitative Proteomic and Phosphoproteomic Analyses Reveal a Role of Death-Associated Protein Kinase 1 in Regulating Hippocampal Synapse.

Death-associated protein kinase 1 (DAPK1) is a stress-responsive calcium/calmodulin (CaM)-regulated serine/threonine protein kinase that is actively involved in stress-induced cell death. The dysregulation of DAPK1 has been established in various neurological disorders such as epilepsy, Alzheimer's disease (AD), and Parkinson's disease (PD). Recent research indicates a synaptic localization of DAPK1 in neurons, suggesting a potential role of DAPK1 in modulating synaptic structure and function. However, the key molecules and pathways underlying the influence of DAPK1 on synapses remain elusive. We utilized quantitative proteomic and phosphoproteomic analyses to compare the differences in protein expression and phosphorylation in hippocampal tissues of wild-type (WT) and DAPK1-knockout (KO) mice. Bioinformatic analysis of differentially expressed proteins and phosphoproteins revealed a preferential enrichment of proteins involved in regulating synaptic function, cytoskeletal structure, and neurotransmission. Gene set enrichment analysis (GESA) highlighted altered presynaptic functions including synaptic vesicle priming and glutamate secretion in KO mice. Besides, we observed that proteins with potential phosphorylation motifs of ERK and DAPK1 were overrepresented among the differential phosphoproteins and were highly enriched in neuronal function-related pathways. Furthermore, Western blot analysis validated differences in the expression of several proteins closely associated with presynaptic organization, dendrites and calcium transmembrane transport between KO and WT mice, further corroborating the potential involvement of DAPK1 in the regulation of synaptic functions. Overall, our data provide molecular evidence to elucidate the physiological links between DAPK1 and neuronal functions and help clarify the role of DAPK1 in the pathogenesis of neurodevelopmental and neurodegenerative diseases.

Death-associated protein kinase 1 phosphorylates MDM2 and inhibits its protein stability and function.

Breast cancer is one of the major malignancies in women, and most related deaths are due to recurrence, drug resistance, and metastasis. The expression of the mouse double minute 2 (MDM2) oncogene is upregulated in breast cancer; however, its regulatory mechanism has yet to be fully elucidated. Herein, we identified the tumor suppressor death-associated protein kinase 1 (DAPK1) as a novel MDM2 regulator by unbiased peptide library screening. DAPK1 is directly bound to MDM2 and phosphorylates it at Thr419. DAPK1-mediated MDM2 phosphorylation promoted its protein degradation via the ubiquitin-proteasome pathway, resulting in upregulated p53 expression. DAPK1 overexpression, but not its kinase activity-deficient form, decreased colony formation and increased doxorubicin-induced cell death; however, DAPK1 knockdown produced the opposite effects in human breast cancer cells. In a xenograft tumorigenesis assay, DAPK1 overexpression significantly reduced tumor formation, whereas inhibition of DAPK1 kinase activity reduced its antitumorigenic effect. Finally, DAPK1 expression was negatively correlated with MDM2 levels in human breast cancer tissues. Thus, these results suggest that DAPK1-mediated MDM2 phosphorylation and its protein degradation may contribute to its antitumorigenic function in breast cancer.

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.

MiR-191-5p Attenuates Tau Phosphorylation, Aß Generation, and Neuronal Cell Death by Regulating Death-Associated Protein Kinase 1.

Dysregulation of microRNAs has been implicated in diverse diseases, including Alzheimer's disease (AD). MiR-191-5p in plasma/serum has been identified as a novel and promising noninvasive diagnostic biomarker for AD. However, whether miR-191-5p is involved in AD pathogenesis is largely unknown, and its levels in human AD brains are undetermined. Herein, we demonstrated that miR-191-5p downregulated tau phosphorylation at multiple AD-related sites and promoted neurite outgrowth using immunoblotting, immunofluorescence, and neurite outgrowth assays. Moreover, immunoblotting and enzyme-linked immunosorbent assays indicated that miR-191-5p decreased amyloid precursor protein phosphorylation levels and beta-amyloid (Aß) generation. Furthermore, miR-191-5p reduced ceramide-induced neuronal cell death analyzed by trypan blue staining, the in situ cell death detection kit, and Annexin V-FITC/PI flow cytometry. Next, we verified that death-associated protein kinase 1 (DAPK1) was a direct target of miR-191-5p through the dual luciferase reporter assay and confirmed that the effects of miR-191-5p were antagonized by restoration of DAPK1 expression. Finally, the hippocampal miR-191-5p level was found to be decreased in humans with AD compared with controls and was inversely correlated with the DAPK1 expression level. Collectively, these findings suggest that miR-191-5p might exert inhibitory effects on tau phosphorylation, Aß secretion, and neuronal cell death by directly targeting DAPK1, providing an attractive therapeutic option for AD.

Knockdown of DAPK1 attenuates IL-1B-induced extracellular matrix degradation and inflammatory response in osteoarthritis chondrocytes via regulating the p38 MAPK-signaling pathway

Objective To reveal the possible effects of death-associated protein kinase 1 (DAPK1) on the progression of osteoarthritis (OA) and the potential underlying mechanism. Methods : The expression of DAPK1 in OA and normal samples and interleukin (IL)-1β-stimulated chondrocytes was analyzed by quantitative real-time polymerase chain reaction and Immunoblot assay. Cell viability, proliferation, and apoptosis in DAPK1-knockdown cells stimulated with IL-1β were detected by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) solution, 5-ethynyl-2β-deoxyuridine staining and flow cytometry. The chondrocyte degradation and inflammatory response in IL-1β-induced chondrocytes were investigated by Immunoblot analysis and enzyme-linked-immunosorbent serologic assay. In addition, the effect of DAPK1 on p38 mitogen-activated protein kinase (MAPK) activation was analyzed by immunoblot assay. Results : This study revealed that DAPK1 was highly expressed in OA patients and IL-1β-induced chondrocytes. Down-regulation of DAPK1 enhanced IL-1β-induced chondrocyte proliferation. DAPK1 knockdown inhibited IL-1β-induced chondrocyte degradation. In addition, DAPK1 depletion inhibited IL-1β-induced chondrocyte inflammation. Mechanically, it was revealed that down--regulation of DAPK1 could inhibit the p38 MAPK pathway, and therefore affected progression of OA. Conclusion : DAPK1 knockdown attenuates IL-1β-induced extracellular matrix degradation and inflammatory response in OA chondrocytes by regulating the p38 MAPK pathway (AU)

Knockdown of DAPK1 attenuates IL-1ß-induced extracellular matrix degradation and inflammatory response in osteoarthritis chondrocytes via regulating the p38 MAPK-signaling pathway.

OBJECTIVE: To reveal the possible effects of death-associated protein kinase 1 (DAPK1) on the progression of osteoarthritis (OA) and the potential underlying mechanism. METHODS: : The expression of DAPK1 in OA and normal samples and interleukin (IL)-1ß-stimulated chondrocytes was analyzed by quantitative real-time polymerase chain reaction and Immunoblot assay. Cell viability, proliferation, and apoptosis in DAPK1-knockdown cells stimulated with IL-1ß were detected by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) solution, 5-ethynyl-2ß-deoxyuridine staining and flow cytometry. The chondrocyte degradation and inflammatory response in IL-1ß-induced chondrocytes were investigated by Immunoblot analysis and enzyme-linked-immunosorbent serologic assay. In addition, the effect of DAPK1 on p38 mitogen-activated protein kinase (MAPK) activation was analyzed by immunoblot assay. RESULTS: : This study revealed that DAPK1 was highly expressed in OA patients and IL-1ß-induced chondrocytes. Down-regulation of DAPK1 enhanced IL-1ß-induced chondrocyte proliferation. DAPK1 knockdown inhibited IL-1ß-induced chondrocyte degradation. In addition, DAPK1 depletion inhibited IL-1ß-induced chondrocyte inflammation. Mechanically, it was revealed that down--regulation of DAPK1 could inhibit the p38 MAPK pathway, and therefore affected progression of OA. CONCLUSION: : DAPK1 knockdown attenuates IL-1ß-induced extracellular matrix degradation and inflammatory response in OA chondrocytes by regulating the p38 MAPK pathway.

Computational Dissection of the Role of Trp305 in the Regulation of the Death-Associated Protein Kinase-Calmodulin Interaction.

Death-associated protein kinase 1 (DAPK1), as a calcium/calmodulin (CaM) regulated serine/threonine kinase, functions in apoptotic and autophagy pathways and represents an interesting drug target for inflammatory bowel disease and Alzheimer's disease. The crystal structure of the DAPK1 catalytic domain and the autoregulatory domain (ARD) in complex with CaM provides an understanding of CaM-dependent regulation of DAPK1 activity. However, the molecular basis of how distinct Trp305 (W305Y and W305D) mutations in the ARD modulate different DAPK1 activities remains unknown. Here, we performed multiple, µs-length molecular dynamics (MD) simulations of the DAPK1-CaM complex in three different (wild-type, W305Y, and W305D) states. MD simulations showed that the overall structural complex did not change significantly in the wild-type and W305Y systems, but underwent obvious conformational alteration in the W305D system. Dynamical cross-correlation and principal component analyses revealed that the W305D mutation enhanced the anti-correlated motions between the DAPK1 and CaM and sampled a broader distribution of conformational space relative to the wild-type and W305Y systems. Structural and energetical analyses further exhibited that CaM binding was unfavored in response to the W305D mutation, resulting in the decreased binding of CaM to the W305D mutant. Furthermore, the hydrogen bonds and salt bridges responsible for the loss of CaM binding on the interface of the DAPK1-CaM complex were identified in the W305D mutant. This result may provide insights into the key role of Trp305 in the regulation of CaM-mediated DAPK1 activity.

Identification of Novel Aryl Carboxamide Derivatives as Death-Associated Protein Kinase 1 (DAPK1) Inhibitors with Anti-Proliferative Activities: Design, Synthesis, In Vitro, and In Silico Biological Studies.

Death-associated protein kinase 1 (DAPK1) is a serine/threonine protein kinase involved in diverse fundamental cellular processes such as apoptosis and autophagy. DAPK1 isoform plays an essential role as a tumor suppressor and inhibitor of metastasis. Consequently, DAPK1 became a promising target protein for developing new anti-cancer agents. In this work, we present the rational design and complete synthetic routes of a novel series of eighteen aryl carboxamide derivatives as potential DAPK1 inhibitors. Using a custom panel of forty-five kinases, a single dose of 10 µM of the picolinamide derivative 4a was able to selectively inhibit DAPK1 kinase by 44.19%. Further investigations revealed the isonicotinamide derivative 4q as a promising DAPK1 inhibitory lead compound with an IC50 value of 1.09 µM. In an in vitro anticancer activity assay using a library of 60 cancer cell lines including blood, lung, colon, CNS, skin, ovary, renal, prostate, and breast cancers, four compounds (4d, 4e, 4o, and 4p) demonstrated high anti-proliferative activity with mean % GI ~70%. Furthermore, the most potent DAPK1 inhibitor (4q) exhibited remarkable activity against leukemia (K-562) and breast cancer (MDA-MB-468) with % GI of 72% and 75%, respectively.