Nuclear Localization of the Serine/Threonine Kinase DRAK2 Is Involved in UV-Induced Apoptosis

Abstract

Apoptosis, a type of programmed cell death, plays an essential role in the survival of multicellular organisms and is observed in a wide variety of physiological situations. 1)Apoptosis is important for biological self-defense, and defects in the ability to undergo apoptosis can lead to various diseases, including cancer, neurodegenerative diseases, and autoimmune diseases.2) Apoptosis is a well-defined cellular process characterized by morphological changes that include condensation of nuclear chromatin, cell shrinkage, and plasma membrane blebbing.3)The Fas family cytokine and tumor necrosis factor (TNF) cascades can mediate apoptosis, 4,5) but recently, many additional apoptotic components have been identified. Using a functional cloning strategy, Deiss et al. identified the deathassociated protein kinase (DAPK) as a positive mediator of apoptosis triggered by interferon-g.6) The kinase activity of DAPK, which shares homology with myosin light chain kinases, is regulated by calmodulin in a Ca 2+ -dependent manner in vitro.7) Overexpression of DAPK in various cell lines results in cell death, and this death-promoting property strictly depends on the intrinsic kinase activity. Additional isoforms of the DAPK family, including DRP-1, ZIP kinase, DAP kinase-related apoptosis-inducing kinase 1 (DRAK1), and DRAK2 have been identified. These proteins share homology in their primary structures, especially in the catalytic domain.8-11) All of these kinases have an apoptosis-promoting activity that is dependent on the kinase activity.We have studied the function of the small Ca 2ϩ -binding protein CHP1 (calcineurin B homologous protein1).12) CHP1 is a multifunctional regulator of various proteins, including Na ϩ /H ϩ antiporters, a kinesin-like motor protein, and calcineurin. [13][14][15] We identified DRAK2 as a CHP1 binding protein, and found that CHP1 inhibits the kinase activity of DRAK2 in a Ca 2ϩ -dependent manner.16) DRAK2 is found in thymus, testis, spleen, and brain, tissues in which apoptosis plays an important role.12) Overexpression of DRAK2 in NIH3T3 cells causes apoptosis like cell death through a mechanism that requires the kinase activity. 10) However, overexpression studies do not necessarily indicate whether DRAK2 causes apoptosis during normal physiological processes.Several components of apoptotic signal transduction pathways, such as DNases, Bcl family members, and caspases, are localized to specific areas of the cell.17) During UV-induced apoptosis, damaged double stranded DNA signals translocation of the mitochondrial components AIF and Endo-G to the nucleus. 18,19) UV irradiation also activates cytoplasmic targets, such as the transcriptional factors AP-1 and NF-kB.20,21) NF-kB migrates to the nucleus and binds to specific response elements of various genes. Thus, the intracellular localization and translocation of molecules are important elements of apoptosis, and understanding these dynamics will elucidate the regulatory mechanisms of apoptosis.The DAPK family members ZIP kinase and DAP kinase...

Serine/Threonine Kinase 17A Is a Novel p53 Target Gene and Modulator of Cisplatin Toxicity and Reactive Oxygen Species in Testicular Cancer Cells

“…In mice, STK17B is enriched in lymphocytes and raises the threshold for T cell activation while maintaining T cell survival but appears not to have a direct role in apoptosis in this setting (15,16). However, other studies suggest a role for STK17B in apoptosis, including UV radiationinduced apoptosis in rat kidney and rat colon cancer cells (47,48). Together, these and the present findings suggest a possible role for STK17B in apoptosis and cell survival during cancer therapy that warrants further investigation.…”

Cyclic Pressure Stimulates DNA Synthesis through the PI3K/Akt Signaling Pathway in Rat Bladder Smooth Muscle Cells

“…SMCs exposed to UV light for 15 min were used as a positive control. 28,40 Quantification of Akt Phosphorylation Following exposure to cyclic pressure for 10, 30, 60 min, and 12 h, SMCs were lysed in cell extraction buffer (Biosource International Inc., Camarillo, CA) supplemented with 1 mM PMSF (Sigma) and protease inhibitor cocktail (Sigma). Total Akt and phosphorylated Akt (Ser473) in cell lysates at each time point were quantified using a commercially available ELISA kit (BioSource) and following the manufacturerÕs instructions.…”

The Role of Drak2 in T Cell Function and Autoimmunity

“…Thus, as reported in certain tumors, Drak2 may function to negatively regulate TGF-β signaling and promote tumorigenesis [10]. However, this is contrary to other reports that describe Drak2 as a tumor suppressor [11,15,30]. Therefore, the role of Drak2 in different types of tumors is also controversial and needs to be studied further.…”

“…However, enforced expression of Drak2 did not cause apoptosis in COS-7 cells [7]. Additional investigations suggest that the intracellular location of Drak2 determines whether it contributes to apoptosis [15]. Ectopic Drak2 expression in ACL-15, HeLa, and WI-38 cells, where Drak2 was localized to the cytoplasm, did not enhance cell death.…”

“…Drak2 was primarily restricted to the cytoplasm upon ectopic expression in ACL-15, HeLa, and WI-38 cells [15,16]. Alternatively, its overexpression in NRK, NIH 3T3, and Caco-2 cells caused Drak2 to localize to the nucleus.…”