The combination of bcl-2 expression and NGF-deprivation facilitates the selective destruction of BAD protein in living sympathetic neurons

Autophagy and apoptosis cascade: which is more prominent in neuronal death?

Autophagy and apoptosis are two crucial self-destructive processes that maintain cellular homeostasis, which are characterized by their morphology and regulated through signal transduction mechanisms. These pathways determine the fate of cellular organelle and protein involved in human health and disease such as neurodegeneration, cancer, and cardiovascular disease. Cell death pathways share common molecular mechanisms, such as mitochondrial dysfunction, oxidative stress, calcium ion concentration, reactive oxygen species, and endoplasmic reticulum stress. Some key signaling molecules such as p53 and VEGF mediated angiogenic pathway exhibit cellular and molecular responses resulting in the triggering of apoptotic and autophagic pathways. Herein, based on previous studies, we describe the intricate relation between cell death pathways through their common genes and the role of various stress-causing agents. Further, extensive research on autophagy and apoptotic machinery excavates the implementation of selective biomarkers, for instance, mTOR, Bcl-2, BH3 family members, caspases, AMPK, PI3K/Akt/GSK3β, and p38/JNK/MAPK, in the pathogenesis and progression of neurodegenerative diseases. This molecular phenomenon will lead to the discovery of possible therapeutic biomolecules as a pharmacological intervention that are involved in the modulation of apoptosis and autophagy pathways. Moreover, we describe the potential role of micro-RNAs, long non-coding RNAs, and biomolecules as therapeutic agents that regulate cell death machinery to treat neurodegenerative diseases. Mounting evidence demonstrated that under stress conditions, such as calcium efflux, endoplasmic reticulum stress, the ubiquitin-proteasome system, and oxidative stress intermediate molecules, namely p53 and VEGF, activate and cause cell death. Further, activation of p53 and VEGF cause alteration in gene expression and dysregulated signaling pathways through the involvement of signaling molecules, namely mTOR, Bcl-2, BH3, AMPK, MAPK, JNK, and PI3K/Akt, and caspases. Alteration in gene expression and signaling cascades cause neurotoxicity and misfolded protein aggregates, which are characteristics features of neurodegenerative diseases. Excessive neurotoxicity and misfolded protein aggregates lead to neuronal cell death by activating death pathways like autophagy and apoptosis. However, autophagy has a dual role in the apoptosis pathways, i.e., activation and inhibition of the apoptosis signaling. Further, micro-RNAs and LncRNAs act as pharmacological regulators of autophagy and apoptosis cascade, whereas, natural compounds and chemical compounds act as pharmacological inhibitors that rescue neuronal cell death through inhibition of apoptosis and autophagic cell death.

Attenuation of diabetic cardiomyopathy by relying on kirenol to suppress inflammation in a diabetic rat model

Diabetic cardiomyopathy is characterized by diabetes‐induced myocardial abnormalities, accompanied by inflammatory response and alterations in inflammation‐related signalling pathways. Kirenol, isolated from Herba Siegesbeckiae, has potent anti‐inflammatory properties. In this study, we aimed to investigate the cardioprotective effect of kirenol against DCM and underlying the potential mechanisms in a type 2 diabetes mellitus model. Kirenol treatment significantly decreased high glucose‐induced cardiofibroblasts proliferation and increased the cardiomyocytes viability, prevented the loss of mitochondrial membrane potential and further attenuated cardiomyocytes apoptosis, accompanied by a reduction in apoptosis‐related protein expression. Kirenol gavage could affect the expression of pro‐inflammatory cytokines in a dose‐dependent manner but not lower lipid profiles, and only decrease fasting plasma glucose, fasting plasma insulin and mean HbA1c levels in high‐dose kirenol‐treated group at some time‐points. Left ventricular dysfunction, hypertrophy, fibrosis and cell apoptosis, as structural and functional abnormalities, were ameliorated by kirenol administration. Moreover, in diabetic hearts, oral kirenol significantly attenuated activation of mitogen‐activated protein kinase subfamily and nuclear translocation of NF‐κB and Smad2/3 and decreased phosphorylation of IκBα and both fibrosis‐related and apoptosis‐related proteins. In an Electrophoretic mobility shift assay, the binding activities of NF‐κB, Smad3/4, SP1 and AP‐1 in the nucleus of diabetic myocardium were significantly down‐regulated by kirenol treatment. Additionally, high dose significantly enhanced myocardial Akt phosphorylation without intraperitoneal injection of insulin. Kirenol may have potent cardioprotective effects on treating for the established diabetic cardiomyopathy, which involves the inhibition of inflammation and fibrosis‐related signalling pathways and is independent of lowering hyperglycaemia, hyperinsulinemia and lipid profiles.

Apoptotic cell death regulation in neurons

Apoptosis plays a major role in shaping the developing nervous system during embryogenesis as neuronal precursors differentiate to become post-mitotic neurons. However, once neurons are incorporated into functional circuits and become mature, they greatly restrict their capacity to die via apoptosis, thus allowing the mature nervous system to persist in a healthy and functional state throughout life. This robust restriction of the apoptotic pathway during neuronal differentiation and maturation is defined by multiple unique mechanisms that function to more precisely control and restrict the intrinsic apoptotic pathway. However, while these mechanisms are necessary for neuronal survival, mature neurons are still capable of activating the apoptotic pathway in certain pathological contexts. In this review, we highlight key mechanisms governing the survival of post-mitotic neurons, while also detailing the physiological and pathological contexts in which neurons are capable of overcoming this high apoptotic threshold.

Blood Coagulation Factor X Exerts Differential Effects on Adenovirus Entry into Human Lymphocytes

It has been proposed that blood coagulation factors, principally factor X (FX), enhance the uptake of human adenovirus type 5 (Ad5) into cultured epithelial cells by bridging the viral hexon capsid protein and cell-surface heparan sulphate proteoglycans (HSPGs). We studied the effects of FX on Ad transduction of lymphoid cell lines (NK92MI, a natural killer cell line; Daudi, a B-cell line and Jurkat, a T-cell line) as well as primary peripheral blood lymphocytes (PBL) and HeLa epithelial cells using either replication-deficient Ad5, or a derivative in which the Ad5 fiber was replaced with that of another Ad type, Ad35, termed Ad5F35. PBL and NK92MI were resistant to Ad5 transduction. Transduction of Jurkat and Daudi cells by Ad5 was reduced by FX but without discernible effects on cell-surface Ad5 binding. FX reduced virus binding and transduction of all lymphoid cell lines by Ad5F35, as well as transduction of the T- and Natural Killer (NK)-cell populations of PBL. Flow cytometry analysis showed that all lymphoid cell lines were negative for HSPG components, in contrast to HeLa cells. FX reduced transduction of an HSPG-negative mutant Chinese hamster ovary cell line (CHOpgsA745) by Ad5 and Ad5F35, with Ad5F35 binding also being reduced by FX. These results point to fiber-dependent differences (Ad5 versus Ad35 fiber) in Ad binding to and transduction of human lymphoid and epithelial cells in the presence of FX.

The roles of cell surface attachment molecules and coagulation Factor X in adenovirus 5-mediated gene transfer in pancreatic cancer cells

Transduction of 11 pancreatic cancer cell lines with a replication-deficient adenovirus 5 expressing enhanced green fluorescent protein (Ad5EGFP) was analyzed and variable EGFP levels were observed, ranging from <1% to ∼40% of cells transduced, depending on the cell line. Efficient Ad5EGFP transduction was associated mainly with higher levels of cell surface Coxsackie and adenovirus receptor (CAR) but not with expression of α(v)β(3) and α(v)β(5) integrins and was fiber dependent. Reduction of CAR by RNA interference resulted in a corresponding decrease in Ad5EGFP transduction. Pre-treatment of Ad5EGFP with blood coagulation Factor X increased virus entry even in the presence of low CAR levels generated by RNA interference, suggesting a potential alternative route of Ad5 entry into pancreatic cancer cells. Immunohistochemistry carried out on 188 pancreatic ductal adenocarcinomas and 68 matched controls showed that CAR was absent in 102 (54%) of adenocarcinomas, whereas moderate and strong staining was observed in 58 (31%) and 28 (15%) cases, respectively. Weak or absent CAR immunolabeling correlated with poor histological differentiation of pancreatic cancer. In normal tissue, strong immunolabeling was detected in islet cells and in the majority of inter- and intralobular pancreatic ducts.

Protection from rapamycin-induced apoptosis by insulin-like growth factor-I is partially dependent on protein kinase C signaling

Rapamycin-induced apoptosis in sarcoma cells is inhibited by insulin-like growth factor-I (IGF-I) through a signaling pathway independent of Ras-extracellular signal-regulated kinase 1/2 and Akt. IGF-I induces Bad phosphorylation (Ser112, Ser136, and Ser155) in a pathway involving phosphoinositide 3' kinase (PI3K) and protein kinase C (PKC; mu, epsilon, or theta) resulting in sequestering Bad from mitochondria and subsequently interacting with 14-3-3gamma in the cytosol. Gene knockdown of Bad, Bid, Akt1, Akt2, PKC-mu, PKC-epsilon, or PKC-theta was achieved by transient transfection using small interfering RNAs. Results indicate that IGF-I signaling to Bad requires activation of PI3K and PKC (mu, theta, epsilon) but not mTOR, Ras-extracellular signal-regulated kinase 1/2, protein kinase A, or p90(RSK). Wortmannin blocked the phosphorylation of PKC-mu (Ser744/Ser748), suggesting that PI3K is required for the activation of PKCs. PKCs phosphorylate Bad under in vitro conditions, and the association of phosphorylated Bad with PKC-mu or PKC-epsilon, as shown by immunoprecipitation, indicated direct involvement of PKCs in Bad phosphorylation. To confirm these results, cells overexpressing pEGFP-N1, wt-Bad, or Bad with a single site mutated (Ser112Ala; Ser136Ala; Ser155Ala), two sites mutated (Ser(112/136)Ala; Ser(112/155)Ala; Ser(136/155)Ala), or the triple mutant were tested. IGF-I protected completely against rapamycin-induced apoptosis in cells overexpressing wt-Bad and mutants having either one or two sites of phosphorylation mutated. Knockdown of Bid using small interfering RNA showed that Bid is not required for rapamycin-induced cell death. Collectively, these data suggest that IGF-I-induced phosphorylation of Bad at multiple sites via a pathway involving PI3K and PKCs is important for protecting sarcoma cells from rapamycin-induced apoptosis.

Regulation of neuronal survival by the extracellular signal-regulated protein kinase 5

The extracellular signal-regulated protein kinase 5 (ERK5) is a mitogen-activated protein kinase (MAPK) that phosphorylates and regulates various transcription factors in response to growth factors and extra-cellular stresses. To address its biological function during the development of the peripheral nervous system (PNS), we have engineered a novel model of sympathetic neurons in which the erk5 gene can be deleted in vitro. Our data provide for the first time genetic evidence that ERK5 is required to mediate the survival response of neurons to nerve growth factor (NGF). Increased cell death associated with the loss of ERK5 is caused by elevated expression of the BH3-only members of the Bcl-2 family, Bad and Bim. Further investigation indicated that ERK5 suppresses the transcription of the bad and the bim genes via Ca⁺⁺/cAMP response element binding protein (CREB) and Forkhead box 03a (Foxo3a), respectively. Consistently, we found that the phosphorylation of both p90 ribosomal S6 kinase (RSK) and protein kinase B (PKB) is impaired in neurons lacking ERK5. Together these findings reveal a novel signaling mechanism that promotes neuronal survival during the development of the PNS.

Lysosomal membrane permeabilization in cell death

Mitochondrial outer membrane permeabilization (MOMP) constitutes one of the major checkpoint(s) of apoptotic and necrotic cell death. Recently, the permeabilization of yet another organelle, the lysosome, has been shown to initiate a cell death pathway, in specific circumstances. Lysosomal membrane permeabilization (LMP) causes the release of cathepsins and other hydrolases from the lysosomal lumen to the cytosol. LMP is induced by a plethora of distinct stimuli including reactive oxygen species, lysosomotropic compounds with detergent activity, as well as some endogenous cell death effectors such as Bax. LMP is a potentially lethal event because the ectopic presence of lysosomal proteases in the cytosol causes digestion of vital proteins and the activation of additional hydrolases including caspases. This latter process is usually mediated indirectly, through a cascade in which LMP causes the proteolytic activation of Bid (which is cleaved by the two lysosomal cathepsins B and D), which then induces MOMP, resulting in cytochrome c release and apoptosome-dependent caspase activation. However, massive LMP often results in cell death without caspase activation; this cell death may adopt a subapoptotic or necrotic appearance. The regulation of LMP is perturbed in cancer cells, suggesting that specific strategies for LMP induction might lead to novel therapeutic avenues.

The BH3-only protein Puma is both necessary and sufficient for neuronal apoptosis induced by DNA damage in sympathetic neurons

DNA damage activates apoptosis in several neuronal populations and is an important component of neuropathological conditions. While it is well established that neuronal apoptosis, induced by DNA damage, is dependent on the key cell death regulators p53 and Bax, it is unknown which proteins link the p53 signal to Bax. Using rat sympathetic neurons as an in vitro model of neuronal apoptosis, we show that cytosine arabinoside is a DNA damaging drug that induces the expression of the BH3-only pro-apoptotic genes Noxa, Puma and Bim. Increased expression occurred after p53 activation, measured by its phosphorylation at serine 15, but prior to the conformational change of Bax at the mitochondria, cytochrome c (cyt c) release and apoptosis. Hence Noxa, Puma and Bim could potentially link p53 to Bax. We directly tested this hypothesis by the use of nullizygous mice. We show that Puma, but not Bim or Noxa, is a crucial mediator of DNA damage-induced neuronal apoptosis. Despite the powerful pro-apoptotic effects of overexpressed Puma in Bax-expressing neurons, Bax nullizygous neurons were resistant to Puma-induced death. Therefore, Puma provides the critical link between p53 and Bax, and is both necessary and sufficient to mediate DNA damage-induced apoptosis of sympathetic neurons.

JNK inhibitory kinase is up-regulated in retinal ganglion cells after axotomy and enhances BimEL expression level in neuronal cells

Optic nerve transection results in retinal ganglion cell (RGC) death in adult mammals, after the alteration of gene expression of RGCs. To elucidate the molecular mechanism by which axotomy induces RGC death, we isolated the molecules up-regulated after optic nerve transection. One of these, axotomy-related [corrected] gene (ARG)357, an 898-amino-acid [corrected] protein containing a complete serine-threonine kinase domain, was isolated from a subtraction library of the rat retina. The sequence showed that this gene was a rat homolog of human c-Jun N-terminal kinase (JNK) inhibitory kinase and so belonged to the germinal center kinase-VIII subfamily of Sterile20s protein kinase. We designated ARG357 as rat JNK inhibitory kinase (JIK). Rat JIK was expressed ubiquitously in various tissues and was highly expressed in the retina, with selective expression in RGCs. After axotomy, BimEL and Hrk, which are BH3-only proteins, and rat JIK were up-regulated in RGCs. Overexpression of rat JIK in neuronal cells up-regulated the expression of BimEL, but not that of Hrk. These results indicate that JIK may contribute to axotomy-induced RGC death by up-regulating the expression of BH3-only protein.

Uth1p: a yeast mitochondrial protein at the crossroads of stress, degradation and cell death

UTH1 is a yeast aging gene that has been identified on the basis of stress resistance and longer life span of mutants. It was also shown to participate in mitochondrial biogenesis. The absence of Uth1p was found to trigger resistance to autophagy induced by rapamycin. Uth1p is therefore the first mitochondrial protein proven to be required for the autophagic degradation of mitochondria. Since this protein is also involved in yeast cell death induced by heterologous expression of the pro-apoptotic protein Bax, the results are discussed in the light of evidence suggesting a co-regulation of apoptosis and autophagy in mammalian cells.

Uth1p is involved in the autophagic degradation of mitochondria

The absence of the outer mitochondrial membrane protein Uth1p was found to induce resistance to rapamycin treatment and starvation, two conditions that induce the autophagic process. Biochemical studies showed the onset of a fully active autophagic activity both in wild-type and Deltauth1 strains. On the other hand, the disorganization of the mitochondrial network induced by rapamycin treatment or 15 h of nitrogen starvation was followed in cells expressing mitochondria-targeted green fluorescent protein; a rapid colocalization of green fluorescent protein fluorescence with vacuole-selective FM4-64 labeling was observed in the wild-type but not in the Deltauth1 strain. Degradation of mitochondrial proteins, followed by Western blot analysis, did not occur in mutant strains carrying null mutations of the vacuolar protease Pep4p, the autophagy-specific protein Atg5p, and Uth1p. These data show that, although the autophagic machinery was fully functional in the absence of Uth1p, this protein is involved in the autophagic degradation of mitochondria.

The same cellular signaling pathways mediate survival in sensory neurons that switch their trophic requirements during development

A distinct subpopulation of rat dorsal root sensory (DRG) neurons, termed P-neurons, switch their trophic requirements for survival during development from nerve growth factor (NGF) at embryonic stages to basic fibroblast growth factor (bFGF) just after birth. We investigated in cultured P-neurons the intracellular signaling pathways mediating survival before and after this switch. The NGF-induced survival was completely blocked by either wortmannin (100 nM) or PD98059 (25-50 nM), which selectively inhibit the phosphatidylinositol 3-kinase-AKT (PI3 kinase-AKT) and mitogen-activated kinase kinase extracellular regulated kinase (MEK-ERKs) pathways, respectively. NGF activated AKT and ERKs in single embryonic P-neurons, as assayed by immunofluorescence of phosphorylated proteins. In concordance with the survival assays, wortmannin and PD98059 blocked AKT and ERKs activation, respectively. Following the trophic switch, bFGF used the same signaling pathways to promote survival of post-natal P-neurons, as either wortmannin or PD98059 blocked its effect. Also, bFGF activated AKT and ERKs in single P-neurons, and this activation was blocked by the same inhibitors. These results strongly suggest that both pathways concurrently mediate the action of NGF and bFGF during embryonic and post-natal periods, respectively. Thus, we report the novel result that the switch in trophic requirements occurs with conservation of the signaling pathways mediating survival.

Roles of ionotropic glutamate receptors in early developing neurons derived from the P19 mouse cell line

We cultured a P19 mouse teratocarcinoma cell line and induced its neuronal differentiation to study the function of ionotropic glutamate receptors (GluRs) in early neuronal development. Immunocytochemical studies showed 85% neuronal population at 5 days in vitro (DIV) with microtubule-associated protein 2-positive staining. Thirty percent and 50% of the cells expressed the alpha-amino-3-hydroxy-5-methyl-4-isopropinonate (AMPA) receptor subunit, GluR2/3, and the kainate (kainic acid; KA) receptor subunit, GluR5/6/7, respectively. In Western blot analysis, the temporal expression of GluR2/3 began to appear at 3 DIV, whereas GluR5/6/7 was already expressed in the undifferentiated cells. P19-derived neurons began to respond to glutamate, AMPA and KA, but not to the metabotropic GluR agonist trans-1-aminocyclopentane-1,3-decarboxylic acid, by 5 DIV in terms of increases in intracellular calcium and phospholipase C-mediated poly-phosphoinositide turnover. Furthermore, KA reduced cell death of P19-derived neurons in both atmospheric and hypobaric conditions in a phospholipase C-dependent manner. The common AMPA/KA receptor antagonist, 6-cyano-7-nitroquinoxaline-2,3-dione, but not the AMPA receptor antagonist, 1,2,3,4-tetrahydro-6-nitro-2,3-dioxo-benzo[f]quinoxaline-7-sulfonamide disodium, profoundly increased hypobaric insult-induced neurotoxicity. In a flow cytometry study, the nerve growth factor-mediated antiapoptotic effect was facilitated by AMPA, with an induction of TrkA, but not p75(NTR) expression. Therefore, AMPA and KA receptors might mediate neurotrophic functions to facilitate neurotrophic factor signaling to protect neurons against hypoxic insult in early neuronal development.

Engineered expression of the Coxsackie B and adenovirus receptor (CAR) in human dendritic cells enhances recombinant adenovirus-mediated gene transfer

Dendritic cells (DCs) are key antigen-presenting cells (APCs) that act as central modulators of cellular immune responses. Genetic modification of DCs has considerable therapeutic potential in the treatment of a wide spectrum of diseases, including cancer and persistent viral infection. In this report, we show that pre-treatment of DCs with a recombinant adenovirus encoding the major adenovirus receptor, Coxsackie B and adenovirus receptor (CAR), significantly increased the uptake of recombinant adenoviruses (Ads) by primary immature monocyte-derived DCs. This could be correlated with CAR mRNA and surface protein expression. Transduction of DCs by recombinant adenoviruses did not significantly alter cellular viability. Therefore, we propose that pre-treatment of DCs with Ad5-CAR is one strategy to increase the susceptibility of DCs to transduction by recombinant Ads.

In vivo PDGF beta receptor activation in the dorsocaudal brainstem of the rat prevents hypoxia-induced apoptosis via activation of Akt and BAD

Activation of platelet-derived growth factor receptor beta (PDGFR) within the caudal brainstem modulates the hypoxic ventilatory response. Since hypoxia does not induce apoptosis in the caudal brainstem, PDGFR could underlie such protective mechanism via a PI3 kinase-dependent phosphorylation of both Akt and BAD pathways. To further study this issue, caudal brainstem lysates were harvested from Sprague--Dawley rats during hypoxia (10% O(2)) after treatment with either vehicle or CGP 57148B (100 mg/kg), a selective blood-brain barrier-permeable PDGFR antagonist. Time-dependent increases in phosphorylated Akt occurred during hypoxia, peaking at 45' and lasting for up to 6 h, without parallel changes in total Akt protein. CGP 57148B attenuated Akt activation at all time points. Similarly, phosphorylation of BAD at serine136 but not at serine 112 occurred in the caudal brainstem as early as 15' of hypoxia, and was completely blocked by CGP 57148B. Furthermore, CGP 57148B treatment elicited significant increases in single-stranded DNA, caspase-like activity, and cleaved caspase 3 after 24 h of hypoxia that were absent in the caudal brainstem of hypoxic vehicle-treated animals. We conclude that PDGFR-dependent in vivo activation of both Akt and BAD during hypoxia prevents induction of apoptosis, and may contribute to the increased hypoxic tolerance of brainstem neurons.

Mitochondria are selectively eliminated from eukaryotic cells after blockade of caspases during apoptosis

Pan caspase inhibitors are potentially powerful cell-protective agents that block apoptosis in response to a wide variety of insults that cause tissue degeneration. In many conditions, however, the blockade of apoptosis by caspase inhibitors does not permit long-term cell survival, but the reasons are not entirely clear. Here we show that the blockade of apoptosis by Boc.Aspartyl(O-methyl)CH2F can result in the highly selective elimination of the entire cohort of mitochondria, including mitochondrial DNA, from both neurons and HeLa cells, irrespective of the stimulus used to trigger apoptosis. In cells that lose their mitochondria, the nuclear DNA, Golgi apparatus, endoplasmic reticulum, centrioles, and plasma membrane remain undamaged. The capacity to remove mitochondria is both specific and regulated since mitochondrial loss in neurons is completely prevented by the expression of the antiapoptotic protein Bcl-2 and partially suppressed by the autolysosomal inhibitor bafilomycin. Cells without mitochondria are more tolerant to an anaerobic environment but are essentially irreversibly committed to death. Prevention of mitochondrial loss may be crucial for the long-term regeneration of tissues emerging from an apoptotic episode in which death was prevented by caspase blockade.

Inhibition of JNK by overexpression of the JNL binding domain of JIP-1 prevents apoptosis in sympathetic neurons

Studies in non-neuronal cells show that c-Jun N-terminal kinases (JNK) play a key role in apoptotic cell death. In some neurons JNK is also thought to initiate cell death by the activation of c-Jun. JNK inhibition has been achieved pharmacologically by inhibiting upstream kinases, but there has been no direct demonstration that inhibition of JNK can prevent neuronal death. We have therefore examined whether the JNK binding domain (JBD) of JNK-interacting protein-1 (JIP-1, a scaffold protein and specific inhibitor of JNK) can inhibit c-Jun phosphorylation and support the survival of sympathetic neurons deprived of NGF. We show that expression of the JBD in >80% of neurons was sufficient to prevent the phosphorylation of c-Jun and its nuclear accumulation as well as abrogate neuronal cell death induced by NGF deprivation. JBD expression also preserved the capacity of mitochondria to reduce MTT. Interestingly, although the PTB domain of JIP was reported to interact with rhoGEF, expression of the JBD domain was sufficient to localize the protein to the membrane cortex and growth cones. Hence, JNK activation is a key event in apoptotic death induced by NGF withdrawal, where its point of action lies upstream of mitochondrial dysfunction.

Functional characterization of two splice variants of rat bad and their interaction with Bcl-w in sympathetic neurons

Neuronal cell death is in many cases regulated by competitive interactions between pro- and antiapoptotic proteins of the Bcl-2 family. In this study we have identified two splice variants of the rat proapoptotic molecule Bad, which differ in their carboxy-terminal regions. Both splice variants of Bad interacted with the antiapoptotic molecule Bcl-w as shown by yeast two-hybrid assay and by co-immunoprecipitation experiments from transfected cells. mRNA expression for the two variants of bad were detected in all neonatal and adult rat tissues tested. Overexpression of either of the two isoforms of Bad in nerve growth factor (NGF)-maintained sympathetic neurons by microinjection induced the cell death of these neurons, which was neutralized by co-expression of Bcl-w. Overexpression of Bcl-w in sympathetic neurons also counteracted death induced by NGF deprivation, which was not reduced by co-expression of either of the two Bad variants. The results suggest that Bcl-w, Bad-alpha, and Bad-beta may participate in the regulation of apoptosis in the sympathetic nervous system.