Biomedical subjects

S J Korsmeyer

Publications and source records attributed to S J Korsmeyer.

At least 91 records · Page 5Linked to original sources

PubMed1998

BCL-2 family: regulators of cell death.

An expanding family of BCL-2 related proteins share homology, clustered within four conserved regions, namely BCL-2 homology (BH1-4) domains, which control the ability of these proteins to dimerize and function as regulators of apoptosis. Moreover, BCL-XL, BCL-2, and BAX can form ion-conductive pores in artificial membranes. The BCL-2 family, comprised of both pro-apoptotic and anti-apoptotic members, acts as a checkpoint upstream of CASPASES and mitochondrial dysfunction. BID and BAD possess the minimal death domain BH3, and the phosphorylation of BAD connects proximal survival signals to the BCL-2 family. BCL-2 and BCL-XL display a reciprocal pattern of expression during lymphocyte development. Gain- and loss-of-function models revealed stage-specific roles for BCL-2 and BCL-XL. BCL-2 can rescue maturation at several points of lymphocyte development. The BCL-2 family also reveals evidence for a cell-autonomous coordination between the opposing pathways of proliferation and cell death.

Animals↗

PubMed1998

Suppression of developmental retinal cell death but not of photoreceptor degeneration in Bax-deficient mice.

PURPOSE: Bax, a member of the Bcl2 family of cell death regulators, induces cell death by promoting the induction of apoptosis. Bax-deficient mice were examined in this study to determine whether Bax is required for cell death in the developing retina and for pathologic apoptotic photoreceptor degeneration resulting from the rd mutation. METHODS: Retinas from Bax-deficient mice and their wild-type siblings were harvested at postnatal day (P) 7 and processed for TdT-dUTP terminal nick-end labeling (TUNEL) staining, and the number of nuclei containing fragmented DNA were counted. Adult retinas and optic nerves were processed for plastic-embedded 1-microm sections, and the cross-sectional area was determined. The mutant Bax allele was outbred onto the C3H mouse strain, which carries the rd allele. Retinas from these animals were examined histologically at P21 after most of the photoreceptor cell death had occurred. RESULTS: At P7, around the time of peak cell death in the inner nuclear layer (INL), significantly fewer neurons in INL and ganglion cell layer (GCL) were TUNEL positive in Bax-deficient mice than in their wild-type siblings. In adult Bax-deficient mice, the cross-sectional area of the optic nerve was approximately 50% larger than in wild-type siblings, and the total number of retinal ganglion cell axons was increased to 226%. The INL of Bax-deficient mice was thicker than normal. The Bax genotype did not affect the thickness or histologic appearance of the outer nuclear layer in retinas of mice with wild-type or mutant rd alleles. CONCLUSIONS: In the absence of the expression of the Bax gene, there is a profound increase in the survival of retinal ganglion cells that lasts into adulthood. Similarly, death of INL cells is diminished but not completely abolished. The absence of Bax does not, however, protect photoreceptors from naturally occurring cell death or degeneration induced by the rd mutation. This shows that Bax is involved to a variable degree in the control of developmental cell death in the retina and that not all apoptotic retinal cell deaths are controlled by Bax.

Animals↗

PubMed1997

Comparison of the ion channel characteristics of proapoptotic BAX and antiapoptotic BCL-2.

The BCL-2 family of proteins is composed of both pro- and antiapoptotic regulators, although its most critical biochemical functions remain uncertain. The structural similarity between the BCL-XL monomer and several ion-pore-forming bacterial toxins has prompted electrophysiologic studies. Both BAX and BCL-2 insert into KCl-loaded vesicles in a pH-dependent fashion and demonstrate macroscopic ion efflux. Release is maximum at approximately pH 4.0 for both proteins; however, BAX demonstrates a broader pH range of activity. Both purified proteins also insert into planar lipid bilayers at pH 4.0. Single-channel recordings revealed a minimal channel conductance for BAX of 22 pS that evolved to channel currents with at least three subconductance levels. The final, apparently stable BAX channel had a conductance of 0.731 nS at pH 4. 0 that changed to 0.329 nS when shifted to pH 7.0 but remained mildly Cl- selective and predominantly open. When BAX-incorporated lipid vesicles were fused to planar lipid bilayers at pH 7.0, a Cl--selective (PK/PCl = 0.3) 1.5-nS channel displaying mild inward rectification was noted. In contrast, BCL-2 formed mildly K+-selective (PK/PCl = 3.9) channels with a most prominent initial conductance of 80 pS that increased to 1.90 nS. Fusion of BCL-2-incorporated lipid vesicles into planar bilayers at pH 7.0 also revealed mild K+ selectivity (PK/PCl = 2.4) with a maximum conductance of 1.08 nS. BAX and BCL-2 each form channels in artificial membranes that have distinct characteristics including ion selectivity, conductance, voltage dependence, and rectification. Thus, one role of these molecules may include pore activity at selected membrane sites.

Animals↗

PubMed1997

Bax deletion further orders the cell death pathway in cerebellar granule cells and suggests a caspase-independent pathway to cell death.

Dissociated cerebellar granule cells maintained in medium containing 25 mM potassium undergo an apoptotic death when switched to medium with 5 mM potassium. Granule cells from mice in which Bax, a proapoptotic Bcl-2 family member, had been deleted, did not undergo apoptosis in 5 mM potassium, yet did undergo an excitotoxic cell death in response to stimulation with 30 or 100 microM NMDA. Within 2 h after switching to 5 mM K+, both wild-type and Bax-deficient granule cells decreased glucose uptake to <20% of control. Protein synthesis also decreased rapidly in both wild-type and Bax-deficient granule cells to 50% of control within 12 h after switching to 5 mM potassium. Both wild-type and Bax -/- neurons increased mRNA levels of c-jun, and caspase 3 (CPP32) and increased phosphorylation of the transactivation domain of c-Jun after K+ deprivation. Wild-type granule cells in 5 mM K+ increased cleavage of DEVD-aminomethylcoumarin (DEVD-AMC), a fluorogenic substrate for caspases 2, 3, and 7; in contrast, Bax-deficient granule cells did not cleave DEVD-AMC. These results place BAX downstream of metabolic changes, changes in mRNA levels, and increased phosphorylation of c-Jun, yet upstream of the activation of caspases and indicate that BAX is required for apoptotic, but not excitotoxic, cell death. In wild-type cells, Boc-Asp-FMK and ZVAD-FMK, general inhibitors of caspases, blocked cleavage of DEVD-AMC and blocked the increase in TdT-mediated dUTP nick end labeling (TUNEL) positivity. However, these inhibitors had only a marginal effect on preventing cell death, suggesting a caspase-independent death pathway downstream of BAX in cerebellar granule cells.

Animals↗

PubMed1997

BH3 domain of BAD is required for heterodimerization with BCL-XL and pro-apoptotic activity.

BAD interacts with anti-apoptotic molecules BCL-2 and BCL-XL and promotes apoptosis. BAD is phosphorylated on serine residues in response to a survival factor, interleukin-3. Phosphorylated BAD cannot bind to BCL-XL or BCL-2 at membrane sites and is found in the cytosol bound to 14-3-3. We report here that deletion mapping and site-directed mutagenesis identified a BH3 domain within BAD that proved necessary for both its heterodimerization with BCL-XL and its death agonist activity. Substitution of the conserved Leu151 with Ala in the BH3 amphipathic alpha-helix abrogated both functions. The BAD Leu151 mutant was predominantly in the cytosol bound to 14-3-3. The BH3 domain of BCL-2 also proved important for BCL-2/BAD interaction. These results establish a critical role for a BH3 domain within BAD and provide evidence that BAD may function as a death ligand whose pro-apoptotic activity requires heterodimerization with BCL-XL.

Amino Acid Sequence↗

PubMed1997

Defects in yolk sac hematopoiesis in Mll-null embryos.

Translocations involving the mixed lineage leukemia gene (MLL), the human homolog of the Drosophila gene trithorax, are one of the most common genetic alterations in human acute leukemias. Each translocation involving MLL results in loss of one functional copy of MLL and the generation of a chimeric fusion protein with potential dominant negative or neomorphic activity. Mll is a positive regulator of Hox genes, which have been implicated in both axial skeleton patterning and hematopoietic development. Previous studies indicated that Hox gene expression is altered in Mll heterozygous (+/-) and homozygous (-/-) deficient mice. To study the role of Mll in hematopoiesis and to obtain insights into leukemogenesis, we have examined the effects of haplo-insufficiency or absence of Mll by in vitro differentiation of Mll +/+, +/-, and -/- yolk sac progenitor cells. Mll -/- colonies were fewer in number, took longer to develop, and contained fewer cells than their wild-type and heterozygous counterparts. Formation of colony-forming unit-granulocyte, erythroid, macrophage, megakaryocyte (CFU-GEMM), colony-forming unit-macrophage (CFU-M), and burst-forming unit-erythroid (BFU-E) was markedly decreased in Mll -/- cultures, while numbers of colony-forming unit-erythroid (CFU-E), colony-forming unit-granulocyte (CFU-G), and colony-forming unit-granulocyte macrophage (CFU-GM) were essentially unaffected. Despite the decreased numbers of colonies present, Mll -/- cultures showed all cell types without morphologic evidence of maturation arrest. These studies indicate that Mll is required for normal numbers of hematopoietic progenitors and their proper differentiation, especially along the myeloid and macrophage pathways.

Animals↗

PubMed1997

On the key role of secondary lymphoid organs in antiviral immune responses studied in alymphoplastic (aly/aly) and spleenless (Hox11(-)/-) mutant mice.

The role of the spleen and of other organized secondary lymphoid organs for the induction of protective antiviral immune responses was evaluated in orphan homeobox gene 11 knockout mice (Hox11(-/-)) lacking the spleen, and in homozygous alymphoplastic mutant mice (aly/aly) possessing a structurally altered spleen but lacking lymph nodes and Peyer's patches. Absence of the spleen had no major effects on the immune response, other than delaying the antibody response by 1-2 d. In aly/aly mice, the thymus-independent IgM response against vesicular stomatitis virus (VSV) was delayed and reduced, whereas the T-dependent switch to the protective IgG was absent. Therefore, aly/aly mice were highly susceptible to VSV infection. Since aly/aly spleen cells yielded neutralizing IgM and IgG after adoptive transfer into recipients with normally structured secondary lymphoid organs, these data suggest that the structural defect was mainly responsible for inefficient T-B cooperation. Although aly/aly mice generated detectable, but reduced, CTL responses after infection with vaccinia virus (VV) and lymphocytic choriomeningitis virus (LCMV), the elimination of these viruses was either delayed (VV) or virtually impossible (LCMV); irrespective of the dose or the route of infection, aly/aly mice developed life-long LCMV persistence. These results document the critical role of organized secondary lymphoid organs in the induction of naive T and B cells. These structures also provide the basis for cooperative interactions between antigen-presenting cells, T cells, and B cells, which are a prerequisite for recovery from primary virus infections via skin or via blood.

Adoptive Transfer↗

PubMed1997

bax-deficiency promotes drug resistance and oncogenic transformation by attenuating p53-dependent apoptosis.

Inactivation of p53-dependent apoptosis promotes oncogenic transformation, tumor development, and resistance to many cytotoxic anticancer agents. p53 can transcriptionally activate bax, a bcl-2 family member that promotes apoptosis. To determine whether bax is required for p53-dependent apoptosis, the effects of bax deficiency were examined in primary fibroblasts expressing the E1A oncogene, a setting where apoptosis is dependent on endogenous p53. We demonstrate that bax can function as an effector of p53 in chemotherapy-induced apoptosis and contributes to a p53 pathway to suppress oncogenic transformation. Furthermore, we show that additional p53 effectors participate in these processes. These p53-controlled factors act synergistically with Bax to promote a full apoptotic response, and their action is suppressed by the Bcl-2 and E1B 19K oncoproteins. These studies demonstrate that Bax is a determinant of p53-dependent chemosensitivity and illustrate how p53 can promote apoptosis by coordinating the activities of multiple effectors.

Animals↗

PubMed1997

Bax suppresses tumorigenesis and stimulates apoptosis in vivo.

The protein p53 is a key tumour-suppressor, as evidenced by its frequent inactivation in human cancers. Animal models have indicated that attenuation of p53-dependent cell death (apoptosis) can contribute to both the initiation and progression of cancer, but the molecular mechanisms are unknown. Although p53-mediated transcriptional activation is one possible explanation, none of the known p53-responsive genes has been shown to function in p53-dependent apoptosis. Here we test the role of the death-promoting gene bax in a transgenic mouse brain tumour, a model in which p53-mediated apoptosis attenuates tumour growth. Inactivation of p53 causes a dramatic acceleration of tumour growth owing to a reduction in apoptosis of over ninety per cent. We show that p53-dependent expression of bax is induced in slow-growing apoptotic tumours. Moreover, tumour growth is accelerated and apoptosis drops by fifty per cent in Bax-deficient mice, indicating that it is required for a full p53-mediated response. To our knowledge this is the first demonstration that Bax acts as a tumour suppressor, and our findings indicate that Bax could be a component of the p53-mediated apoptotic response in this system.

Animals↗

PubMed1997

HOX11 interacts with protein phosphatases PP2A and PP1 and disrupts a G2/M cell-cycle checkpoint.

Hox11 is an orphan homeobox gene that controls the genesis of the spleen. HOX11 is also oncogenic, having been isolated from a chromosomal breakpoint in human T-cell leukaemia. Transgenic mice that redirected HOX11 to the thymus demonstrated cell-cycle aberration and progression to malignancy. We observed that the protein HOX11 interacted with protein serine-threonine phosphatase 2A catalytic subunit (PP2AC), as well as protein phosphatase 1 (PP1C) in mammalian cells. Inhibition of PP2A can regulate the cell cycle and control the activation of maturation-promoting factor in Xenopus oocytes. Microinjection of HOX11 into Xenopus oocytes arrested at the G2 phase of the cell cycle promoted progression to the M phase. G2 arrest can be induced by gamma-irradiation, but is eliminated by expression of HOX11 within a T-cell line. Thus HOX11 is a cellular oncogene that targets PP2A and PP1, both of which are targets for oncogenic viruses and chemical tumour promoters. This interaction suggests a mechanism by which a homeobox can alter the cell cycle.

Animals↗

PubMed1997

Errors of homeostasis and deregulated apoptosis.

Apoptosis research has accelerated with the discovery of genes within a common cell death pathway and evidence for their inter-relationship. Breakthroughs include insights into the mechanism of action of the Bcl-2 family, caspases and their targets, and death receptor complexes. Deregulation of apoptosis is evident in tumors and viral infection, as well as in autoimmune disease, immunodeficiency, neurodegeneration, and infertility.

Animals↗

PubMed1997

Bcl-2 and Bax function independently to regulate cell death.

The BCL-2 family has various pairs of antagonist and agonist proteins that regulate apoptosis. Whether their function is interdependent is uncertain. Using a genetic approach to address this question, we utilized gain- and loss-of-function models of Bcl-2 and Bax and found that apoptosis and thymic hypoplasia characteristic of Bcl-2-deficient mice are largely absent in mice also deficient in Bax. A single copy of Bax promoted apoptosis in the absence of Bcl-2. In contrast, overexpression of Bcl-2 still repressed apoptosis in the absence of Bax. While an in vivo competition exists between Bax and Bcl-2, each is able to regulate apoptosis independently.

Animals↗

PubMed1997

Enx (Hox11L1)-deficient mice develop myenteric neuronal hyperplasia and megacolon.

The isolated homeobox gene Enx (Hox11L1) is expressed in enteric neurons innervating distal ileum, and proximal and distal colon. Enx-deficient mice develop megacolon with massive distension of the proximal colon. The number of myenteric ganglia, total neurons per ganglion, and NADPH diaphorase presumptive inhibitory neurons per ganglion are increased in the proximal and distal colon, but decreased in the distal ileum of all Enx-/- mice. Enx-/- mice provide a model for human neuronal intestinal dysplasia (NID), in which myenteric neuronal hyperplasia and megacolon are seen. These results suggest that Enx is required for the proper positional specification and differentiative cell fate of enteric neurons.

Animals↗

PubMed1997

Apoptosis-associated signaling pathways are required for chemotherapy-mediated female germ cell destruction.

Female sterility resulting from oocyte destruction is an unfortunate, and in many cases inevitable, consequence of chemotherapy. We show that unfertilized mouse oocytes exposed to therapeutic levels of the antitumor drug, doxorubicin (DXR), undergo apoptosis; however, fertilized oocytes do not initiate apoptosis, but enter cell-cycle arrest, when treated with DXR. Apoptosis induced by DXR in oocytes is blocked by sphingosine-1-phosphate, an inhibitor of ceramide-promoted cell death. Oocytes from Bax-deficient, but not p53-null, female mice display complete resistance to DXR-induced apoptosis in vivo and in vitro. Pretreatment of oocytes with a specific peptide inhibitor of caspases also abrogates the apoptotic response to DXR. These findings indicate that oocyte destruction caused by chemotherapy can be prevented by manipulation of apoptosis-associated signaling pathways.

Amino Acid Chloromethyl Ketones↗

PubMed1997

BCL-XL-regulated apoptosis in T cell development.

Thymocyte differentiation progresses through well-defined stages in which apoptosis is central to the selection of a functional TCR repertoire. In the present study, we explored the developmental effects of BCL-XL, a repressor of apoptosis. We found that endogenous BCL-XL is down-regulated by both positive and negative selection signals at the CD4+ CD8+ stage of thymocyte development. We examined the role of BCL-XL regulatable apoptosis in T cell development in the context of an alpha beta TCR transgene, Rag-1 deficiency and the scid model. We found that BCL-XL expression promoted accumulation of CD8 single-positive thymocytes even in MHC class II-restricted TCR transgenic mice. However, the apoptotic resistance conferred by BCL-XL could not fully substitute for TCR-mediated positive selection signals nor did it prevent negative selection. Overexpression of BCL-XL promoted partial maturation of CD4-CD8- thymocytes to CD4+CD8+ cells in a Rag-deficient, but not a scid background. Thus, TCR-mediated signals mediate the regulation of endogenous BCL-XL during thymocyte development, indicating that the principal protection of double-positive thymocytes by BCL-XL occurs prior to selection. The impact of BCL-XL on the CD8 but not CD4 lineage supports the asymmetric model of lineage commitment. Moreover, several critical control points in T cell development could be distinguished as BCL-XL responsive or unresponsive.

Animals↗

PubMed1997

A major human immunodeficiency virus type 1-initiated killing pathway distinct from apoptosis.

We have investigated the relative contribution of apoptosis or programmed cell death (PCD) to cell killing during acute infection with T-cell-tropic, cytopathic human immunodeficiency virus type 1 (HIV-1), by employing diverse strategies to inhibit PCD or to detect its common end-stage sequelae. When Bcl-2-transfected cell lines were infected with HIV-1, their viability was only slightly higher than that of control infections. Although the adenovirus E1B 19-kDa protein has been reported to be a stronger competitor of apoptosis than Bcl-2, it did not inhibit HIV-mediated cell death better than Bcl-2 protein. Competition for Fas ligand or inactivation of the Fas pathway secondary to intracellular mutation (MOLT-4 T cells) also had modest effects on overall cell death during acute HIV infection. In contrast to these observations with HIV infection or with HIV envelope-initiated cell death, Tat-expressing cell lines were much more susceptible (200% enhancement) to Fas-induced apoptosis than controls and Bcl-2 overexpression strongly (75%) inhibited this apoptotic T-cell death. PCD associated with FasR ligation resulted in the cleavage of common interleukin-1beta-converting enzyme (ICE)-protease targets, poly(ADP-ribose) polymerase (PARP) and pro-ICE, whereas cleaved products were not readily detected during HIV infection of peripheral blood mononuclear cells or T-cell lines even during periods of extensive cell death. These results indicate that one important form of HIV-mediated cell killing proceeds by a pathway that lacks the characteristics of T-cell apoptosis. Our observations support the conclusion that at least two HIV genes (env and tat) can kill T cells by distinct pathways and that an envelope-initiated process of T-cell death can be discriminated from apoptosis by many of the properties most closely associated with apoptotic cell death.

Adenovirus E1B Proteins↗

PubMed1997

Bcl-2 gene family in the nervous system.

A growing family of genes that share homology with the bcl-2 proto-oncogene is involved in the regulation of cell death. Many of these proteins show widespread expression and are expressed in the nervous system in developing and adult organisms. A physiologic role for Bcl-2 and Bcl-x in neuron survival has been shown. In addition, these proteins have been shown to protect neurons from a wide array of toxic insults. In this review, we discuss the Bcl-2 family of proteins with regard to their structure and interactions. We then discuss the role of apoptotic cell death in the development of the nervous system and as a response to neuronal injury. Lastly, we discuss the evidence for a role for these cell death regulators in neuronal death decisions.

Animals↗

PubMed1996

BAX-induced cell death may not require interleukin 1 beta-converting enzyme-like proteases.

Expression of BAX, without another death stimulus, proved sufficient to induce a common pathway of apoptosis. This included the activation of interleukin 1 beta-converting enzyme (ICE)-like proteases with cleavage of the endogenous substrates poly(ADP ribose) polymerase and D4-GDI (GDP dissociation inhibitor for the rho family), as well as the fluorogenic peptide acetyl-Asp-Glu-Val-Asp-aminotrifluoromethylcoumarin (DEVD-AFC). The inhibitor benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (zVAD-fmk) successfully blocked this protease activity and prevented FAS-induced death but not BAX-induced death. Blocking ICE-like protease activity prevented the cleavage of nuclear and cytosolic substrates and the DNA degradation that followed BAX induction. However, the fall in mitochondrial membrane potential, production of reactive oxygen species, cytoplasmic vacuolation, and plasma membrane permeability that are downstream of BAX still occurred. Thus, BAX-induced alterations in mitochondrial function and subsequent cell death do not apparently require the known ICE-like proteases.

Apoptosis↗