The Cell Death-promoting Gene DP5, Which Interacts with the BCL2 Family, Is Induced during Neuronal Apoptosis Following Exposure to Amyloid β Protein

Abstract

DP5, which contains a BH3 domain, was cloned as a neuronal apoptosis-inducing gene. To confirm that DP5 interacts with members of the Bcl-2 family, 293T cells were transiently co-transfected with DP5 and Bcl-xl cDNA constructs, and immunoprecipitation was carried out. The 30-kDa Bcl-xl was co-immunoprecipitated with Myc-tagged DP5, suggesting that DP5 physically interacts with Bcl-xl in mammalian cells. Previously, we reported that DP5 is induced during neuronal apoptosis in cultured sympathetic neurons. Here, we analyzed DP5 gene expression and the specific interaction of DP5 with Bcl-xl during neuronal death induced by amyloid-␤ protein (A ␤). DP5 mRNA was induced 6 h after treatment with A ␤ in cultured rat cortical neurons. The protein encoded by DP5 mRNA showed a specific interaction with Bcl-xl. Induction of DP5 gene expression was blocked by nifedipine, an inhibitor of L-type voltage-dependent calcium channels, and dantrolene, an inhibitor of calcium release from the endoplasmic reticulum. These results suggested that the induction of DP5 mRNA occurs downstream of the increase in cytosolic calcium concentration caused by A ␤. Moreover, DP5 specifically interacts with Bcl-xl during neuronal apoptosis following exposure to A ␤, and its binding could impair the survival-promoting activities of Bcl-xl. Thus, the induction of DP5 mRNA and the interaction of DP5 and Bcl-xl could play significant roles in neuronal degeneration following exposure to A ␤.Apoptosis, or programmed cell death, plays an important role not only in neuronal development and differentiation of the central nervous system but also in the pathogenesis of a variety of neurodegenerative disorders such as Alzheimer's disease. However, the molecular events or cascades underlying neuronal death regulated by the genetic program still remain unclear. Elucidation of the molecular mechanisms underlying neuronal death could contribute to understanding of the pathophysiology of neurodegenerative disorders such as Alzheimer's disease.Previously, we isolated a novel gene named DP5 that is induced during neuronal apoptosis using rat sympathetic neurons in culture deprived of NGF (1).1 This gene has the following unique features: 1) the encoded protein has a BH3 domain, which is essential for interaction with Bcl-2 and Bcl-xl, and a transmembrane region at its C-terminal; 2) its expression shows marked induction with peak levels at 15 h after NGF withdrawal, concurrent with the time at which neurons are committed to die in the sympathetic culture model; and 3) overexpression of full-length DP5 in cultured neurons was sufficient to induce apoptosis. In the developing murine nervous system, DP5 mRNA was localized in several tissues such as the trigeminal and dosal root ganglia and the anterior horn of the spinal cord, which are known to contain a number of apoptotic cells in the mouse embryo. These observations suggested that DP5 could be associated with the phenomena of neuronal death in vivo (2).Recently, Inohara et al. (3) cloned the human gene Harakiri ...

Physical and functional interaction between BH3-only protein Hrk and mitochondrial pore-forming protein p32

“…9,10 The initial studies demonstrated that Hrk expression is relatively restricted to the brain and in the lymphoid tissues, 9,10 suggesting that Hrk may have a specific role in these tissues. Consistent with this idea, induction of Hrk expression has been demonstrated in NGF-deprived sympathetic neurons, 9 in apoptosis of cortical neurons after amyloid-b protein exposure, 11 in apoptotic cerebellar granule neurons cultured under a low potassium condition, 12 in spinal neurons of amyotrophic lateral sclerosis patients, 13 in retinal ganglion cells of axontomized retina, 14 as well as in growth factor-deprived hematopoietic cells. 15 Although Hrk expression has also been detected in blastomere undergoing fragmentation during embryonic development, 16 these characteristic patterns of Hrk expression strongly suggest that this BH3-only protein may have a specific role in initiating neuronal and hematopoietic cell apoptosis under physiological and pathological conditions.…”

Identification of Novel Cytokine-Induced Genes in Pancreatic β-Cells by High-Density Oligonucleotide Arrays

“…Thus, the death protein-5 was increased at 24 h by both exposure to IL-1␤ alone and IL-1␤ ϩ INF-␥. Death protein-5 is a gene induced in neuronal apoptosis, and it possesses a BH3 domain that allows interaction with Bcl-2 and Bcl-xl (78). It will be of interest to investigate whether this gene has a similar role in ␤-cells.…”

Identification of ligands and coligands for the ecdysone-regulated gene switch

“…Deliberate manipulation of gene activity is also an indispensable tool for clinical applications such as gene therapy. The ecdysone-inducible system has proved useful for studying a multitude of processes, such as apoptosis (32)(33)(34)(35)(36), cancer and cell-cycle regulation (37)(38)(39)(40), embryonic development (41,42), signal transduction (43)(44)(45), lipid metabolism (46), and neuronal function (47)(48)(49)(50). The strengths of the system appear to be its tight regulation, its dose responsiveness, and the favorable uptake and clearance kinetics of the steroid inducer, which results in rapid gene switching.…”