DAP-kinase: from functional gene cloning to establishment of its role in apoptosis and cancer

Abstract

DAP-kinase is a pro-apoptotic Ca 2+ calmodulin-regulated serine/threonine kinase that participates in a wide array of apoptotic systems initiated by interferon-g, TNF-a, activated Fas, and detachment from extracellular matrix. It was isolated by an unbiased functional approach to gene cloning aimed at hitting central mediators of the apoptotic process. This 160 Kd protein kinase is localized to actin microfilaments and carries interesting modules such as ankyrin repeats and the death domain. The death promoting effects of DAP-kinase depend on its intact catalytic activity, the correct intracellular localization, and on the presence of the death domain. A few mechanisms restrain the killing effects of the protein in healthy cells. The enzyme's active site is negatively controlled by an adjacent CaM regulatory domain whose effect is relieved by binding to Ca 2+ -activated calmodulin. A second mode of autoinhibition engages the serine-rich C-terminal tail, spanning the last 17 amino acids of the protein. A link between DAPkinase and cancer has been established. It was found that the mRNA and protein expression is frequently lost in various human cancer cell lines. Analysis of the methylation status of DAP-kinase's 5' UTR in DNA extracted from fresh tumor samples, showed high incidence of hypermethylation in several human carcinomas and B cell malignancies. The antitumorigenic effect of DAP-kinase was also studied experimentally in mouse model systems where the re-introduction of DAP-kinase into highly metastatic mouse lung carcinoma cells who had lost the protein, strongly reduced their metastatic capacity. Thus, it appears that loss of DAP-kinase confers a selective advantage to cancer cells and may play a causative role in tumor progression. A few novel kinases sharing high homology in their catalytic domains with DAPkinase have been recently identified constituting altogether a novel family of death promoting serine/threonine kinases. Cell Death and Differentiation (2001) 8, 6 ± 15.

DNA Hypermethylation of Cell Cycle (p15 and p16) and Apoptotic (p14, p53, DAPK and TMS1) Genes in Peripheral Blood of Leukemia Patients

“…Methylation in DAPK gene is associated with increased tumor virulence in lung cancer (Tang et al, 2000). It was also associated with resistance to apoptosis in leukemia cell lines subjected to INF-γ (Cohen and Kimchi, 2001). Silencing of DAPK gene provides a number of selective advantages for tumor cells.…”

“…It is activated by INF-γ, Fas, and detachment from the extracellular matrix (Cohen and Kimchi, 2001). DAPK activates p53-mediated apoptosis via p14 (Raveh et al, 2001).…”

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

“…The members of DAPK family, including DAPkinase, DRP-1/DAPK2, Dlk/ZIP kinase, DRAK1 and DRAK2, share highly conserved catalytic domains but differ in their extra-catalytic domains [1,2]. These structure features account for their phosphorylation of common substrate and capability of inducing apoptosis and yet diverse subcellular localization and certain unique activities.…”

Aberrant methylation of DAP-kinase in therapy-related acute myeloid leukemia and myelodysplastic syndromes

“…3 Among genes identified as deregulated through hypermethylation and that could be of functional significance as tumor suppressor gene is death-associated protein kinase (DAP-kinase). 9 DAP-kinase is a proapoptotic calcium/calmodulin-regulated serine/ threonine kinase that participates in several apoptotic pathways initiated by interferon ␥ (IFN-␥), tumor necrosis factor ␣ (TNF-␣), activated Fas, and detachment from extracellular matrix. 9,10 DAPkinase is abnormally methylated in a significant proportion of human tumors, providing evidence that inactivation of this gene is critical for cancer development.…”