1612

DAPK1

DAPK;death-associated protein kinase 1;DAPK1;death-associated protein kinase 1

DAP kinase 1

9q21.33

protein-coding

The viability of vertebrate cells depends on a complex signaling interplay between survival factors and cell-death effectors. Subtle changes in the equilibrium between these regulators can result in abnormal cell proliferation or cell death, leading to various pathological manifestations. Death-associated protein kinase (DAPK) is a multidomain calcium/calmodulin (CaM)-dependent Ser/Thr protein kinase with an important role in apoptosis regulation and tumor suppression. The molecular signaling mechanisms regulating this kinase, however, remain unclear. Here, we show that DAPK is phosphorylated upon activation of the Ras-extracellular signal-regulated kinase (ERK) pathway. This correlates with the suppression of the apoptotic activity of DAPK. We demonstrate that DAPK is a novel target of p90 ribosomal S6 kinases (RSK) 1 and 2, downstream effectors of ERK1/2. Using mass spectrometry, we identified Ser-289 as a novel phosphorylation site in DAPK, which is regulated by RSK. mutation of Ser-289 to alanine results in a DAPK mutant with enhanced apoptotic activity, whereas the phosphomimetic mutation (Ser289Glu) attenuates its apoptotic activity. Our results suggest that RSK-mediated phosphorylation of DAPK is a unique mechanism for suppressing the proapoptotic function of this death kinase in healthy cells as well as Ras/Raf-transformed cells.

The role of aberrant tumor suppressor gene methylation in the aggressiveness of papillary thyroid cancer (PTC) has not been documented. By showing promoter methylation-induced gene silencing in PTC-derived cell lines, we first demonstrated the functional consequence of methylation of several recently identified tumor suppressor genes, including those for tissue inhibitor of metalloproteinase-3 (TIMP3), SLC5A8, death-associated protein kinase (DAPK) and retinoic acid receptor beta2 (RARbeta2). We then investigated the role of methylation of these genes in the aggressiveness of PTC by examining the relationship of their aberrant methylation to clinicopathological characteristics and BRAF mutation in 231 primary PTC tumors. Methylation of TIMP3, SLC5A8 and DAPK was significantly associated with several aggressive features of PTC, including extrathyroidal invasion, lymph node metastasis, multifocality and advanced tumor stages. Methylation of these genes was also significantly associated with BRAF mutation in PTC, either individually or collectively in various combinations. Methylation of these genes, either individually or collectively, occurred more frequently in more aggressive classical and tall-cell PTC subtypes than in less aggressive follicular-variant PTC, with the latter known to infrequently harbor BRAF mutation. Several other tumor suppressor genes investigated were not methylated. These results suggest that aberrant methylation and hence silencing of TIMP3, SLC5A8, DAPK and RARbeta2, in association with BRAF mutation, may be an important step in PTC tumorigenesis and progression.

Lung cancer is one of the most frequent neoplasia in the Russia, the United States and Europe. This cancer is associated with functional activity changes of many genes. In the present study TIMP3, DAPK1 and AKR1B10 genes transcription analysis of squamous cell lung cancer specimens was carried out using reverse transcription-PCR. Substantial increasing of AKR1B10 transcription level is revealed in 80% tumor samples. TIMP3 and DAPK1 transcription level is considerably decreased in 76 and 72% tumor specimens, accordingly. These results may point out that all three genes are important for squamous cell lung cancer tumorogenesis while AKR1B10 is potential oncogene whereas TIMP3 and DAPK1 are potential tumor suppressor genes. We suggest that revealed substantial transcription level-changes of investigated genes may be used for oncodiagnostics.

Death-associated protein kinase (DAPK) is a unique multidomain kinase acting both as a tumor suppressor and an apoptosis inducer. The molecular mechanism underlying the effector function of DAPK is not fully understood, while the role of DAPK in T lymphocyte activation is mostly unknown. DAPK was activated after TCR stimulation. Through the expression of a dominant-negative and a constitutively active form of DAPK in T cells, we found that DAPK negatively regulated T cell activation. DAPK markedly affected T cell proliferation and IL-2 production. We identified TCR-induced NF-kappaB activation as a target of DAPK. In contrast, IL-1beta- and TNF-alpha-triggered NF-kappaB activation was not affected by DAPK. We further found that DAPK selectively modulated the TCR-induced translocation of protein kinase Ctheta, Bcl-10, and IkappaB kinase into membrane rafts. Notably, the effect of DAPK on the raft entry was specific for the NF-kappaB pathway, as other raft-associated molecules, such as linker for activation of T cells, were not affected. Our results clearly demonstrate that DAPK is a novel regulator targeted to TCR-activated NF-kappaB and T cell activation.

BACKGROUND: Cigarette smoking is the most established risk factor, and genetic variants and/or gene promoter methylations are also considered to play an essential role in development of lung cancer, but the pathogenesis of lung cancer is still unclear. METHODS: We collected the data of 150 cases and 150 age-matched and sex-matched controls on a Hospital-Based Case-Control Study in China. Face to face interviews were conducted using a standardized questionnaire. gene polymorphism and methylation status were measured by RFLP-PCR and MSP, respectively. Logistic regressive model was used to estimate the odds ratios (OR) for different levels of exposure. RESULTS: After adjusted age and other potential confounding factors, smoking was still main risk factor and significantly increased 3.70-fold greater risk of NSCLC as compared with nonsmokers, and the ORs across increasing levels of pack years were 1, 3.54, 3.65 and 7.76, which the general dose-response trend was confirmed. Our striking findings were that the risk increased 5.16, 8.28 and 4.10-fold, respectively, for NSCLC with promoter hypermethylation of the p16, DAPK or RAR beta gene in smokers with CYP1A1 variants, and the higher risk significantly increased in smokers with null GSTM1 and the OR was 17.84 for NSCLC with p16 promoter hypermethylation, 17.41 for DAPK, and 8.18 for RAR beta in smokers with null GSTM1 compared with controls (all p < 0.01). CONCLUSION: Our study suggests the strong combined effects of cigarette smoke, CYP1A1 and GSTM1 Polymorphisms, hypermethylations of p16, DAPK and RAR beta promoters in NSCLC, implying complex pathogenesis of NSCLC should be given top priority in future research.

Interleukin-1beta (IL-1beta) is critical for inflammation and control of infection. The production of IL-1beta depends on expression of pro-IL-1beta and inflammasome component induced by inflammatory stimuli, followed by assembly of inflammasome to generate caspase-1 for cleavage of pro-IL-1beta. Here we show that tumor suppressor death-associated protein kinase (DAPK) deficiency impaired IL-1beta production in macrophages. generation of tumor necrosis factor-alpha in macrophages, in contrast, was not affected by DAPK knockout. Two tiers of defects in IL-1beta generation were found in DAPK-deficient macrophages: decreased pro-IL-1beta induction by some stimuli and reduced caspase-1 activation by all inflammatory stimuli examined. With a normal NLRP3 induction in DAPK-deficient macrophages, the diminished caspase-1 generation is attributed to impaired inflammasome assembly. There is a direct binding of DAPK to NLRP3, suggesting an involvement of DAPK in inflammasome formation. We further illustrated that the formation of NLRP3 inflammasome in situ induced by inflammatory signals was impaired by DAPK deficiency. Taken together, our results identify DAPK as a molecule required for full production of IL-1beta and functional assembly of the NLRP3 inflammasome. In addition, DAPK knockout reduced uric acid crystal-triggered peritonitis, suggesting that DAPK may serve as a target in the treatment of IL-1beta-associated autoinflammatory diseases.