Aberrant induction of Par-4 is involved in apoptosis of hippocampal neurons in presenilin-1 M146V mutant knock-in mice

Cancer and Alzheimer's Inverse Correlation: an Immunogenetic Analysis

Numerous studies have demonstrated an inverse link between cancer and Alzheimer's disease (AD), with data suggesting that people with Alzheimer's have a decreased risk of cancer and vice versa. Although other studies have investigated mechanisms to explain this relationship, the connection between these two diseases remains largely unexplained. Processes seen in cancer, such as decreased apoptosis and increased cell proliferation, seem to be reversed in AD. Given the need for effective therapeutic strategies for AD, comparisons with cancer could yield valuable insights into the disease process and perhaps result in new treatments. Here, through a review of existing literature, we compared the expressions of genes involved in cell proliferation and apoptosis to establish a genetic basis for the reciprocal association between AD and cancer. We discuss an array of genes involved in the aforementioned processes, their relevance to both diseases, and how changes in those genes produce varying effects in either disease.

A new and simple approach for genotyping Alzheimer's disease presenilin-1 mutant knock-in mice

The use of transgenic mice expressing point mutations demands that the detection of the different alleles is efficient and reliable. In addition, the multiplication of transgenes included in mouse models of human disease underlines the importance of correct controls and the fact that investigators need an accurate and rapid genotyping of the littermates generated. In this study, we demonstrate a powerful alternative for genotyping using presenilin-1 mutant knock-in (PS1M146KI) mice as an example. Mutations in the presenilin-1 (PS1) gene are causally linked to many cases of early-onset inherited Alzheimer's disease (AD). PS1M146VKI mice that express the PS1M146V targeted allele at normal physiological levels and triple-transgenic model (3 x Tg-AD) derived from homozygous PS1M146VKI mice were generated to study the pathogenesis of AD. Genotyping PS1M146VKI line requires many steps and thus a large quantity of DNA. In PS1M146VKI mice, only three nucleotides are modified in the gene. Here we show that this small mutated DNA sequence can affect its secondary structure resulting in altered mobility that can be easily detected on a polyacrylamide gel, by the single-strand conformation polymorphism (SSCP) technique. Our results demonstrate that SSCP is a simple, accurate, repeatable and efficient method for the routine genotyping of this current AD model. This method could be easily applied to other transgenic mice.

Apoptosis and tumor resistance conferred by Par-4

Par-4 is a tumor suppressor protein with a pro-apoptotic function. Epigenetic silencing of Par-4 is seen in diverse tumors and Par-4 knockout mice develop spontaneous tumors in various tissues. Endogenous Par-4 is essential for sensitization of cells to diverse apoptotic stimuli, whereas ectopic expression of Par-4 can selectively induce apoptosis in cancer cells. The cancer-specific pro-apoptotic action of Par-4 resides in its centrally located SAC domain. This review emphasizes the role of Par-4/SAC in apoptosis and tumor resistance. SAC transgenic mice display normal development and life span, and, most importantly, are resistant to spontaneous, as well as oncogene-induced, autochthonous tumors. The tumor resistant phenotype and undetectable toxicity of SAC in vivo suggests the SAC domain possesses tremendous therapeutic potential.

Ceramide signaling in cancer and stem cells

Most of the previous work on the sphingolipid ceramide has been devoted to its function as an apoptosis inducer. Recent studies, however, have shown that in stem cells, ceramide has additional nonapoptotic functions. In this article, ceramide signaling will be reviewed in light of 'systems interface biology': as an interconnection of sphingolipid metabolism, membrane biophysics and cell signaling. The focus will be on the metabolic interconversion of ceramide and sphingomyelin or sphingosine-1-phosphate. Lipid rafts and sphingolipid-induced protein scaffolds will be discussed as a membrane interface for lipid-controlled cell signaling. Ceramide/sphingomyelin and ceramide/sphingosine-1-phosphate-interdependent cell-signaling pathways are significant for the regulation of cell polarity, apoptosis and/or proliferation, and as novel pharmacologic targets in cancer and stem cells.

Long-chain ceramide is elevated in presenilin 1 (PS1M146V) mouse brain and induces apoptosis in PS1 astrocytes

The pro-apoptotic sphingolipid ceramide plays an emergent role in the etiology of Alzheimer's disease (AD), although its function for neurodegeneration is not known. We determined the concentration and composition of ceramide in hippocampal tissue from newborn presenilin 1 (PS1) knock-in (PS1M146V) mice, a mouse model for early-onset familial AD. We found that PS1 tissue contains 3.1 (+/-0.5)-fold more total ceramide than wild-type tissue. In particular, the proportion of C20 and C24 ceramide is increased by 4.0- or 8.5-fold, respectively. The ceramide elevation in PS1 brain is consistent with a 3.7 (+/-0.5)-fold increase of the protein level of the neurotrophin receptor p75NTR, which has been suggested to stimulate the hydrolysis of sphingomyelin to generate ceramide. The predominance of C20 and C24 ceramide is concurrent with the elevated gene expression of lass 2 and lass 4, two isoforms of ceramide synthase that generate dihydroceramide with long-chain fatty acid. Our study indicates that primary cultured astrocytes but not neurons from PS1 mice undergo apoptosis when incubated with C20 ceramide. In contrast, wild-type astrocytes remain unaffected. The sensitivity of PS1 astrocytes is most likely due to the 9.5 (+/-0.4)-fold elevated expression of PAR-4 (prostate apoptosis response-4), a protein that inhibits atypical PKC zeta/lambda in the presence of ceramide. Our results suggest that astroglial death due to ceramide/PAR-4-induced apoptosis may critically contribute to the etiology of AD.

Activation of p38MAPK contributes to expanded polyglutamine-induced cytotoxicity

Background

The signaling pathways that may modulate the pathogenesis of diseases induced by expanded polyglutamine proteins are not well understood.

Methodologies/Principal Findings

Herein we demonstrate that expanded polyglutamine protein cytotoxicity is mediated primarily through activation of p38MAPK and that the atypical PKC iota (PKCι) enzyme antagonizes polyglutamine-induced cell death through induction of the ERK signaling pathway. We show that pharmacological blockade of p38MAPK rescues cells from polyglutamine-induced cell death whereas inhibition of ERK recapitulates the sensitivity observed in cells depleted of PKCι by RNA interference. We provide evidence that two unrelated proteins with expanded polyglutamine repeats induce p38MAPK in cultured cells, and demonstrate induction of p38MAPK in an in vivo model of neurodegeneration (spinocerebellar ataxia 1, or SCA-1).

Conclusions/Significance

Taken together, our data implicate activated p38MAPK in disease progression and suggest that its inhibition may represent a rational strategy for therapeutic intervention in the polyglutamine disorders.

Rab5 mediates an amyloid precursor protein signaling pathway that leads to apoptosis

Alzheimer's disease (AD) involves activation of apoptotic pathways that may be regulated through signaling cascades initiated by the amyloid precursor protein (APP). Enlarged endosomes have been observed in postmortem AD brains at very early stages of the disease. We show here that exogenous expression of a familial AD (FAD) mutant of APP or of the APP binding protein APP-BP1 in neurons causes enlargement of early endosomes, increased receptor-mediated endocytosis via a pathway dependent on APP-BP1 binding to APP, and apoptosis. Levels of both APP-BP1 and Rab5 are elevated in early endosomes in cortical embryonic neurons expressing APP(V642I) or APP-BP1, in cultured skin fibroblast cells from Down syndrome subjects, and in postmortem hippocampal tissue of individuals with AD. Indeed, Rab5 was found to bind specifically to APP-BP1, between amino acids 443 and 479. Inhibition of Rab5 or dynamin activity, but not of Eps15 (epidermal growth factor receptor pathway substrate 15) activity, rescued neurons from apoptosis induced by either APP(V642I) or APP-BP1, without affecting levels of intracellular or secreted amyloid-beta (Abeta). Induction of Rab5 activity via expression of a constitutively active mutant led to an increase in neuronal apoptosis more than twice that attributable to induction of endosome enlargement via a Rab5-independent mechanism, regardless of Abeta production. Together, these findings suggest that Rab5 activation via an APP/APP-BP1-initiated signaling pathway mediates neuronal apoptosis caused by FAD mutants of APP and that, within this pathway, Rab5 has a specific role in signaling that is distinct from, although not independent of, its role in trafficking.

Reduction in CHT1-mediated choline uptake in primary neurons from presenilin-1 M146V mutant knock-in mice

The memory loss in Alzheimer's disease (AD) has been linked to cholinergic hypoactivity. Mutations in presenilin-1 (PS-1) may regulate cholinergic signaling, although their precise roles in cholinergic neurotransmission in AD are unsettled. Neuronal uptake of choline via the high affinity choline transporter (CHT1) is essential for cholinergic neurotransmission. CHT1 is a Na+-dependent, hemicholinium-3 (HC-3)-sensitive choline transporter. Although cholinergic neurons in the nucleus basalis of Meynert are a major source of cholinergic projections for the cerebral cortex, it is unclear whether cortical neurons exhibit intrinsic CHT1 activity that is altered in AD. We now report that primary cortical neurons express intrinsic and biologically active CHT1, and that, in these neurons, CHT1-mediated choline uptake activity is significantly reduced in PS-1 M146V mutant knock-in mice. Further kinetic studies using HC-3 binding and cell surface biotinylation assays showed that the PS-1 mutation inhibits CHT1 mediated choline uptake by reducing the ligand binding affinity of CHT1 without significantly altering levels of CHT1 expression in the plasma membrane. Since human neocortex has recently been shown to possess intrinsic cholinergic innervation, our results indicate that alterations in CHT1-mediated high affinity choline uptake in cortical neurons may contribute to Alzheimer's dementia.

Apoptosis antagonizing transcription factor protects renal tubule cells against oxidative damage and apoptosis induced by ischemia-reperfusion

Apoptosis antagonizing transcription factor (AATF) is a leucine zipper domain-containing protein that has antiapoptotic properties. AATF is expressed in several organs and tissues, including the kidney. AATF may participate in inhibition of proapoptotic pathways and/or activation of antiapoptotic pathways. Ischemia/reperfusion-induced renal injury (IRI) is clinically important because it typically damages renal tubular epithelial cells and glomerular cells and is the most common cause of acute renal failure. It now is reported that AATF is expressed in human kidney proximal tubule (HK-2) cells and in mouse primary renal tubule epithelial cells. Levels of AATF expression were altered significantly in these cells in a well-established in vitro model of renal IRI. In transfected HK-2 cells, RNA interference-mediated silencing of AATF exacerbated whereas overexpression of the full-length AATF ameliorated mitochondrial dysfunction, accumulation of superoxide and peroxynitrite, lipid peroxidation, caspase-3 activation, and apoptotic death that were induced by IRI. In primary renal tubule epithelial cells, overexpression of AATF mediated by recombinant adeno-associated virus (AAV) vectors resulted in significant antiapoptotic activity, whereas knockdown of AATF by small interference RNA led to exacerbated cell death after IRI. These results identify AATF as a novel cytoprotective factor against oxidative and apoptotic damage in renal tubular cells. AATF may represent a potential candidate for therapeutic application in IRI.

Dysfunction of amyloid precursor protein signaling in neurons leads to DNA synthesis and apoptosis

The classic neuropathological diagnostic markers for AD are amyloid plaques and neurofibrillary tangles, but their role in the etiology and progression of the disease remains incompletely defined. Research over the last decade has revealed that cell cycle abnormalities also represent a major neuropathological feature of AD. These abnormalities appear very early in the disease process, prior to the appearance of plaques and tangles; and it has been suggested that neuronal cell cycle regulatory failure may be a significant component of the pathogenesis of AD. The amyloid precursor protein (APP) is most commonly known as the source of the beta-amyloid (Abeta) peptides that accumulate in the brains of patients with AD. However, a large body of work supports the idea that APP is also a signaling receptor. Most recently, it has been shown that familial AD (FAD) mutations in APP or simple overexpression of wild type APP cause dysfunction of APP signaling, resulting in initiation of DNA synthesis in neurons and consequent apoptosis. In this article, we review the evidence that APP has the potential to activate aberrant neuronal cell cycle re-entry in AD, and we describe a signal transduction pathway that may mediate this abnormal activation of the cell cycle.

Par-4 is a novel mediator of renal tubule cell death in models of ischemia-reperfusion injury

Prostate apoptosis response-4 (Par-4) is a leucine zipper protein linked to apoptotic cell death in prostate cancer and neuronal tissues. The leucine zipper domain of Par-4 (Leu.zip) mediates protein-protein interactions that are essential for sensitization of cells to apoptosis, and overexpression of Leu.zip blocks Par-4 activity in a dominant negative fashion. Ischemia-reperfusion-induced renal injury (IRI) is clinically important because it typically damages renal tubular epithelial cells and glomerular cells, and it is the most common cause of acute renal failure (ARF). We now report that Par-4 is expressed in renal tubule cells and that aberrant expression of Par-4 activity plays a crucial role in activating apoptotic pathways in well-characterized models of renal IRI. Increased levels of Par-4 were observed following chemical ischemia-reperfusion in HK-2 cells in vitro and in mouse renal tubular cells following bilateral clamping of renal pedicles in vivo. Inhibition of Par-4 expression by specific par-4 antisense oligonucleotides largely prevented HK-2 cell apoptosis induced by IRI. Overexpression of Par-4 in these cells exacerbated mitochondrial dysfunction and caspase activation and conferred increased sensitivity to IRI-induced apoptosis. Expression of Leu.zip, a dominant negative regulator of Par-4, largely prevented mitochondrial dysfunction and caspase activation and significantly inhibited IRI-induced apoptosis in HK-2 cells. In addition, transfection of Par-4 increased while transfection of Leu.zip decreased necrosis in HK-2 cells following prolonged IRI. These results identify Par-4 as a novel and early mediator of renal tubule cell injury following IRI and provide a potential target for developing new therapeutic strategies for renal IRI and ARF.

Interaction of presenilins with FKBP38 promotes apoptosis by reducing mitochondrial Bcl-2

Presenilins 1 and 2 (PS1/2), causative molecules for familial Alzheimer's disease (FAD), are multipass transmembrane proteins localized predominantly in the endoplasmic reticulum (ER) and Golgi apparatus. Heteromeric protein complexes containing PS1/2 are thought to participate in several functions, including intramembrane proteolysis mediated by their gamma-secretase activities. Previous studies have shown that PS1/2 are also involved in the regulation of apoptotic cell death, although the underlying mechanism remains unknown. Here, we demonstrate that FKBP38, an immunophilin family member residing in the mitochondrial membrane, is an authentic PS1/2-interacting protein. PS1/2 and FKBP38 form macromolecular complexes together with anti-apoptotic Bcl-2. PS1/2 promote the degradation of FKBP38 and Bcl-2 and sequester these proteins in the ER/Golgi compartments, thereby inhibiting FKBP38-mediated mitochondrial targeting of Bcl-2 via a gamma-secretase-independent mechanism. Thus, PS1/2 increase the susceptibility to apoptosis by antagonizing the anti-apoptotic function of FKBP38. In contrast, C-terminal fragments of caspase-processed PS1/2 redistribute Bcl-2 to the mitochondria by abrogating the activity of full-length PS1/2, resulting in a dominant-negative anti-apoptotic effect. In cultured cells and mutant PS1-knockin mice brains, FAD-linked PS1/2 mutants enhance the pro-apoptotic activity by causing a more efficient reduction in mitochondrial Bcl-2 than wild-type PS1/2. These results suggest a novel molecular mechanism for the regulation of mitochondria-mediated apoptosis by competition between PS1/2 and FKBP38 for subcellular targeting of Bcl-2. Excessive pro-apoptotic activity of PS1/2 may play a role in the pathogenesis of FAD.

Binding of Par-4 to the actin cytoskeleton is essential for Par-4/Dlk-mediated apoptosis

Prostate apoptosis response-4 (Par-4) is a 38-kDa protein originally identified as a gene product upregulated in prostate cancer cells undergoing apoptosis. Cell death mediated by Par-4 and its interaction partner DAP like kinase (Dlk) is characterized by dramatic changes of the cytoskeleton. To uncover the role of the cytoskeleton in Par-4/Dlk-mediated apoptosis, we analyzed Par-4 for a direct association with cytoskeletal structures. Confocal fluorescence microscopy revealed that endogenous Par-4 is specifically associated with stress fibers in rat fibroblasts. In vitro cosedimentation analyses and in vivo FRET analyses showed that Par-4 directly binds to F-actin. Actin binding is mediated by the N-terminal 266 amino acids, but does not require the C-terminal region of Par-4 containing the leucine zipper and the death domain. Furthermore, the interaction of Par-4 with actin filaments leads to the formation of actin bundles in vitro and in vivo. In rat fibroblasts, this microfilament association is essential for the pro-apoptotic function of Par-4, since both disruption of the actin cytoskeleton by cytochalasin D treatment and overexpression of Par-4 constructs impaired in actin binding result in a significant decrease of apoptosis induction by Par-4 and Dlk. We propose a model, in which Par-4 recruits Dlk to stress fibers, leading to enhanced phosphorylation of the regulatory light chain of myosin II (MLC) and to the induction of apoptosis.

RNAi knockdown of Par-4 inhibits neurosynaptic degeneration in ALS-linked mice

Evidence from human amyotrophic lateral sclerosis (ALS) patients and ALS-linked Cu/Zn superoxide dismutase (Cu/Zn-SOD) transgenic mice bearing the mutation of glycine to alanine at position 93 (G93A) suggests that the pro-apoptotic protein prostate apoptosis response-4 (Par-4) might be a critical link in the chain of events leading to motor neuron degeneration. We now report that Par-4 is enriched in synaptosomes and post-synaptic density from the ventral horn of the spinal cord. Levels of Par-4 in synaptic compartments increased significantly during rapid and slow declining stages of muscle strength in hSOD1 G93A mutant mice. In the pre-muscle weakness stage, hSOD1 G93A mutation sensitized synaptosomes from the ventral horn of the spinal cord to increased levels of Par-4 expression following excitotoxic and apoptotic insults. In ventral spinal synaptosomes, Par-4-mediated production of pro-apoptotic cytosolic factor(s) was significantly enhanced by the hSOD1 G93A mutation. RNA interference (RNAi) knockdown of Par-4 inhibited mitochondrial dysfunction and caspase-3 activation induced by G93A mutation in synaptosomes from the ventral horn of the spinal cord, and protected spinal motor neurons from apoptosis. These results identify the synapse as a crucial cellular site for the cell death promoting actions of Par-4 in motor neurons, and suggest that targeted inhibition of Par-4 by RNAi may prove to be a neuroprotective strategy for motor neuron degeneration.

AATF protects neural cells against oxidative damage induced by amyloid beta-peptide

Extensive loss of neurons and synapses in vulnerable regions of the brain is one of the most important pathological features of Alzheimer's disease (AD). Increased oxidative stress has been shown to contribute to the neurodegenerative process in AD. Aggregation of amyloid beta-peptide (Abeta) in amyloid plaques is one of the defining features of Alzheimer's disease. Indeed, Abeta has been shown to induce oxidative stress and apoptosis in many in vivo and in vitro models of AD. We now report that AATF (apoptosis-antagonizing transcription factor), a leucine zipper protein initially identified as an interaction partner of DAP like kinase (Dlk, a member of the pro-apoptotic Death-Associated Protein kinase family), is expressed in cortical neurons and in neural PC12 cells. Abeta induces alterations in AATF expression in cortical neurons. Inhibition of AATF induction sensitizes neurons to Abeta toxicity. Overexpression of AATF suppressed superoxide production, inhibited peroxynitrite formation and membrane lipid peroxidation, and protected against Abeta-induced apoptosis in PC12 cells. These results suggest that AATF is a novel neuroprotective factor and it may protect against Abeta-induced apoptosis through its effects on suppressing the production of reactive oxygen species (ROS). AATF may therefore represent a potential candidate for therapeutic intervention of neurodegeneration in both sporadic and familial forms of AD.

Par-4 Inhibits Choline Uptake by Interacting with CHT1 and Reducing Its Incorporation on the Plasma Membrane

CHT1 is a Na(+)- and Cl(-)-dependent, hemicholinium-3 (HC-3)-sensitive, high affinity choline transporter. Par-4 (prostate apoptosis response-4) is a leucine zipper protein involved in neuronal degeneration and cholinergic signaling in Alzheimer's disease. We now report that Par-4 is a negative regulator of CHT1 choline uptake activity. Transfection of neural IMR-32 cells with human CHT1 conferred Na(+)-dependent, HC-3-sensitive choline uptake that was effectively inhibited by cotransfection of Par-4. Mapping studies indicated that the C-terminal half of Par-4 was physically involved in interacting with CHT1, and the absence of Par-4.CHT1 complex formation precluded the loss of CHT1-mediated choline uptake induced by Par-4, indicating that Par-4.CHT1 complex formation is essential. Kinetic and cell-surface biotinylation assays showed that Par-4 inhibited CHT1-mediated choline uptake by reducing CHT1 expression in the plasma membrane without significantly altering the affinity of CHT1 for choline or HC-3. These results suggest that Par-4 is directly involved in regulating choline uptake by interacting with CHT1 and by reducing its incorporation on the cell surface.

AATF Inhibits Aberrant Production of Amyloid β Peptide 1-42 by Interacting Directly with Par-4

Aggregation of the neurotoxic amyloid beta peptide 1-42 (Abeta-(1-42)) in the brain is considered to be an early event in the pathogenesis of Alzheimer's disease (AD). Par-4 (prostate apoptosis response-4) is a leucine zipper protein that is pro-apoptotic and associated with neuronal degeneration in AD. Overexpression of Par-4 significantly increased production of Abeta-(1-42) after initiation of apoptotic cascades, indicating factors regulating apoptotic pathways may also affect processing of beta-amyloid precursor protein (APP). AATF (apoptosis-antagonizing transcription factor) was recently identified as an interaction partner of DAP-like kinase (Dlk), a member of the DAP (death-associated protein) kinase family. AATF antagonizes apoptosis induced by Par-4, suggesting that AATF might directly or indirectly participate in regulation of Par-4 activity. We now report that AATF colocalizes with Par-4 in both cytoplasmic and nuclear compartments, and it interacts directly and selectively with Par-4 via the leucine zipper domain in neural cells. Par-4 induced an aberrant production and secretion of Abeta in neuroblastoma IMR-32 cells after apoptotic cascades are initiated. Co-expression of AATF completely blocked aberrant production and secretion of Abeta-(1-42) induced by Par-4, and AATF/Par-4 complex formation was essential for the inhibitory effect of AATF on aberrant Abeta secretion. These results indicate that AATF is an endogenous antagonist of Par-4 activity and an effective inhibitor of aberrant Abeta production and secretion under apoptotic conditions.

Regulation of cell death in mitotic neural progenitor cells by asymmetric distribution of prostate apoptosis response 4 (PAR-4) and simultaneous elevation of endogenous ceramide

Cell death and survival of neural progenitor (NP) cells are determined by signals that are largely unknown. We have analyzed pro-apoptotic signaling in individual NP cells that have been derived from mouse embryonic stem cells. NP formation was concomitant with elevated apoptosis and increased expression of ceramide and prostate apoptosis response 4 (PAR-4). Morpholino oligonucleotide-mediated antisense knockdown of PAR-4 or inhibition of ceramide biosynthesis reduced stem cell apoptosis, whereas PAR-4 overexpression and treatment with ceramide analogs elevated apoptosis. Apoptotic cells also stained for proliferating cell nuclear antigen (a nuclear mitosis marker protein), but not for nestin (a marker for NP cells). In mitotic cells, asymmetric distribution of PAR-4 and nestin resulted in one nestin(-)/PAR-4(+) daughter cell, in which ceramide elevation induced apoptosis. The other cell was nestin(+), but PAR-4(-), and was not apoptotic. Asymmetric distribution of PAR-4 and simultaneous elevation of endogenous ceramide provides a possible mechanism underlying asymmetric differentiation and apoptosis of neuronal stem cells in the developing brain.

Apoptosis by Par-4 in cancer and neurodegenerative diseases

Prostate apoptosis response-4 (par-4) is a pro-apoptotic gene identified in prostate cancer cells undergoing apoptosis. Par-4 protein, which contains a leucine zipper domain at the carboxy-terminus, functions as a transcriptional repressor in the nucleus. Par-4 selectively induces apoptosis in androgen-independent prostate cancer cells and Ras-transformed cells but not in androgen-dependent prostate cancer cells or normal cells. Cells that are resistant to apoptosis by Par-4 alone, however, are greatly sensitized by Par-4 to the action of other pro-apoptotic insults such as growth factor withdrawal, tumor necrosis factor, ionizing radiation, intracellular calcium elevation, or those involved in neurodegenerative diseases such as Alzheimer's, Parkinson's, Huntington's, and stroke. Apoptosis induction by Par-4 involves a complex mechanism that requires activation of the Fas death receptor signaling pathway and coparallel inhibition of cell survival NF-kappaB transcription activity. The unique ability of Par-4 to induce apoptosis in cancer cells but not normal cells and the ability of Par-4 antisense or dominant-negative mutant to abrogate apoptosis in neurodegenerative disease paradigms makes it an appealing candidate for molecular therapy of cancer and neuronal diseases.