Gene cloning, expression, and crystallization of a thermostable exo-inulinase from Geobacillus stearothermophilus KP1289

The gene ( inuA) encoding exo-inulinase (EC 3.2.1.80) was cloned from the thermophilic Geobacillus stearothermophilus ( Bacillus stearothermophilus) KP 1289 growing at between 41 degrees C and 69 degrees C. The inuA gene consisted of 1,482 bp encoding a protein of 493 amino acids. The deduced polypeptide of molecular mass ( M) 56,744 Da showed strong sequence similarity to Pseudomonas mucidolens exo-inulinase, Bacillus subtilis levanase, Paenibacillus polymyxa ( Bacillus polymyxa) fructosyltransferase, and so on, indicating that the enzyme belonged to glycosyl hydrolase family 32. The M of the purified exo-inulinase, expressed in Escherichia coli HB101, was estimated as approximately 54,000 Da by both SDS-PAGE and gel filtration. These results suggested that the active form of the enzyme is a monomer. The enzyme was active between 30 and 75 degrees C with an optimum at 60 degrees C. The properties were identical to those of the native enzyme. Additionally, for the first time for a prokaryotic GH32 protein, crystals of the recombinant enzyme were obtained.

A new prognosis factor analysis based on nonhomogeneous Markov description

To evaluate prognosis factors, Cox's proportional hazard model has been used. But it was found that the analytical ability was not sufficient. So we propose a new evaluation method combining Markov chain model and multiple logistic regression analysis to estimate the prognosis factors. Stage II breast cancer was chosen as the subject. The data was retrospective data gathered in National Cancer Center Central Hospital. As first step, a simple Markov chain model was constructed to describe the state transition of a breast cancer. Then the multiple property of each state transition was investigated in detail. And the patients who had gotten a recurrence for the first two and a half years were discriminated as the poor prognosis group by a nonparametric test (p < 0.05). And the result proved to corresponding with the clinical experience. As second step, three factors (n classification of pathological diagnosis, ductal spread, and estrogen receptor) were selected as the prognosis factors for the early death in Stage II breast cancer by a multiple logistic regression analysis. This new prognosis factor analysis could find out some scientific evidences. Especially, it was found to be remarkable efficient in proving clinically experienced observation.

Potential mechanism for the effects of dexamethasone on growth of androgen-independent prostate cancer

BACKGROUND

Dexamethasone, a synthetic glucocorticoid, has clinical benefit in patients with hormone-refractory prostate cancer (HRPC), but the mechanisms responsible for its effects are unknown. The nuclear factor-kappaB (NF-kappaB)-dependent cytokine interleukin (IL) 6 (IL-6) is thought to stimulate growth of HRPC. Because dexamethasone interferes with NF-kappaB activation, we determined whether dexamethasone inhibits prostate cancer growth by working through the glucocorticoid receptor (GR) to interfere with NF-kappaB-IL-6 pathway.

METHODS

Three human prostate cancer cell lines (DU145, PC-3, and LNCaP) were assessed for GR expression and responsiveness to dexamethasone. Levels of GR, NF-kappaB, and the cytoplasmic NF-kappB inhibitor IkappaBalpha were determined by western blotting and of IL-6 by enzyme immunoassay. The subcellular localization of NF-kappaB was analyzed by immunofluorescence. The effects of dexamethasone (thrice weekly injections of 1 microg/mouse) on DU145 xenografts in nude and severe combined immunodeficient (SCID) mice were evaluated. GR expression in human prostate cancers was assessed by immunohistochemistry. All statistical tests were two-sided.

RESULTS

Dexamethasone dose dependently decreased GR levels and inhibited the growth of DU145 and PC-3 but not LNCaP cells (DU145 cells, P< .001; PC-3 cells, P = .009). Dexamethasone increased IkappaBalpha protein levels and the cytosolic accumulation of NF-kappaB in DU145 cells and decreased secreted IL-6 levels to 37 pg/mL (95% confidence interval [CI] = 33 pg/mL to 41 pg/mL), compared with 164 pg/mL (95% CI = 162 pg/mL to 166 pg/mL) secreted by ethanol-treated control cells. Dexamethasone inhibited the growth of DU145 xenografts in nude (P = .006) and SCID (P = .026) mice without affecting GR levels. Eight of 16 human prostate cancers expressed GR at high levels (>or=30% GR-positive cells).

CONCLUSION

Dexamethasone inhibited the growth of GR-positive cancers, possibly through the disruption of the NF-kappaB-IL-6 pathway.

A thermostable collagenolytic protease with a very large molecular mass produced by thermophilic Bacillus sp. strain MO-1

A collagenolytic protease was purified to homogeneity from thermophilic Bacillus sp. strain MO-1. The protease from strain MO-1 showed high activity toward type I and IV collagens and gelatin. However, peptide substrates (4-phenylazobenzyloxycarbonyl-Pro-Leu-Gly-Pro-Arg and 2-furylacryloyl-Leu-Gly-Pro-Ala) for collagenases were inert as substrates. The collagenolytic protease cleaved oxidized insulin B-chain at 11 sites and degraded type I and IV collagens into anonymous small pieces, suggesting that the protease digests collagens at multiple sites. The collagenolytic protease was far more thermostable than a mesophilic Clostridium histolyticum collagenase. The collagenolytic protease possesses two salient features: (1) it has a very large molecular mass, 210 kDa, and consists of two, identical 105-kDa subunits; (2) it belongs to a serine protease group. The high molecular mass is unique among serine proteases but common for collagenases. The features of the enzyme from strain MO-1 suggest that it is a new collagenolytic protease which is distinct from previously reported collagenases and serine proteases.

Role of anti-apoptotic Bcl-2 protein in spinal muscular atrophy

Apoptosis is an essential physiological cell death for selective elimination of cells, involved in a variety of biological events including morphogenesis, cell turn over and removal of harmful cells. Disruption of the regulation of apoptosis may result in various diseases, including cancer and autoimmune diseases both associated with inhibition of apoptosis and various degenerative disorders associated with enhancement of apoptosis, and therefore, apoptosis is an important theme in the medical field. Apoptosis is driven by a family of cysteine proteases, called caspases and regulated by a Bcl-2 family of proteins, which is the best characterized apoptosis regulators. The Bcl-2 family consists of anti-apoptotic and pro-apoptotic members, and some members are implicated in cancer and nuronal diseases. Here, I overview the mechanism of how Bcl-2 family proteins regulate cell death, and how they are implicated in human diseases, particularly focusing on role of Bcl-2 in spinal muscular atropy.

Vascular smooth muscle maintains the levels of Bcl-2 in endothelial cells

Endothelial cells (ECs) play important roles in maintaining vascular homeostasis. Therefore, dysregulation of EC apoptosis may be involved in the mechanism of atherogenesis. Since recent evidence has shown that vascular endothelial growth factor (VEGF), an EC-specific growth factor, is released from vascular smooth muscle cells (VSMCs), we examined whether VSMCs can modulate EC apoptosis using a coculture system. Incubation of ECs with high levels of nitric oxide (NO) released by N-ethyl-2-[1-ethyl-2-hydroxy-2-nitrosohydrazino]-ethanamine, a NO releasing agent, resulted in apoptosis in association with decreased levels of Bcl-2, and increased levels of Bax, an accelerator of aoptosis. Exogenously added VEGF partially inhibited apoptosis and alterations of these bcl-2 family proteins induced by NO. On the other hand, NO-induced apoptosis and down-regulation of Bcl-2 in ECs were almost completely inhibited by coculturing with VSMCs. However, these inhibitory effects by VSMCs were suppressed by a neutralizing antibody against VEGF. In addition, overexpression of Bcl-2 prevented from NO-induced apoptosis in ECs. These findings indicate that VSMCs protect ECs from NO-induced apoptosis through inhibiting down-regulation of Bcl-2. Thus, vascular smooth muscle which releases EC survival factors including VEGF may play important roles in maintaining the levels of Bcl-2 in ECs.

A single-chain Fv fragment 2A3 specific for native lysozyme: isolation from a human synthetic phage display antibody library and characterization

We have isolated from a human synthetic phage display library a clone, 2A3, which discriminates native lysozyme from denatured forms. Binding of single-chain Fv fragments (scFvs) of the clone to native hen egg white lysozyme was competitively inhibited by native hen egg white (hew) and human (h) lysozymes. Dot blotting analysis indicated that scFv of the clone did not react with denatured lysozymes. The K(d) values for scFv of 2A3 binding to native hew- and h-lysozymes were 3.78 x 10(-9) and 9.31 x 10(-9) M, respectively, indicating that 2A3 binds more strongly to native hew-lysozyme than to native h-lysozyme. The deduced amino acid sequence of the V(H) chain-CDR3 region of 2A3 was RRYALDY, of which the Arg residues at positions 1 and 2 of the CDR3 region were observed to be extremely rare in other antibodies by homology analysis. Based on these observations, site-directed mutagenesis of the RRYALDY-coding region was carried out. The results, combined with biomolecular analyses, demonstrated that Arg residues at positions 1 and 2 of this region were important for native lysozyme-binding.

VDAC regulation by the Bcl-2 family of proteins

The Bcl-2 family of proteins consists of anti-apoptotic and pro-apoptotic members, which determine the life or death of cells by altering mitochondrial membrane permeability. Pro-apoptotic Bcl-2 family members increase mitochondrial membrane permeability, resulting in the release of mitochondrial apoptogenic factors such as cytochrome c that activates death proteases called caspases, whereas anti-apoptotic family members prevent this increase of mitochondrial membrane permeability. The release of cytochrome c is central to apoptotic signal transduction in mammals, and has been studied extensively, leading to the development of several models for cytochrome c release including rupture of the mitochondrial outer membrane and involvement of specific channels. This article describes the important role of a mitochondrial outer membrane channel, the voltage-dependent anion channel (VDAC), in apoptogenic cytochrome c release and its regulation by Bcl-2 family members, and also discusses the molecular architecture of the life - death switch in mammalian cells. Cell Death and Differentiation (2000) 7, 1174 - 1181

A novel protein, RTN-XS, interacts with both Bcl-XL and Bcl-2 on endoplasmic reticulum and reduces their anti-apoptotic activity

Bcl-2 and Bcl-XL serve as critical inhibitors of apoptosis triggered by a broad range of stimuli, mainly acting on the mitochondria. We identified two members of the reticulon (RTN) family as Bcl-XL binding proteins, i.e., NSP-C (RTN1-C) and a new family member, RTN-XS, both of which did not belong to the Bcl-2 family and were predominantly localized on the endoplasmic reticulum (ER). RTN-XS interacted with both Bcl-XL and Bcl-2, increased the localization of Bcl-XL and Bcl-2 on the ER, and reduced the anti-apoptotic activity of Bcl-XL and Bcl-2. On the other hand, NSP-C interacted only with Bcl-XL, affected the localization of Bcl-XL, and reduced Bcl-XL activity, but had no effect on Bcl-2. These results suggest that RTN family proteins can modulate the anti-apoptotic activity of Bcl-XL and Bcl-2 by binding with them and can change their localization to the ER.

Rare somatic inactivation of the multiple endocrine neoplasia type 1 gene in secondary hyperparathyroidism of uremia

The molecular pathway of autonomous growth of the parathyroid glands in uremic patients is poorly understood. Loss of heterozygosity at the recently identified multiple endocrine neoplasia type 1 (MEN1) gene locus on chromosome 11q13 has been found in a subset of parathyroid glands from patients with refractory hyperparathyroidism. To clarify the role of the MEN1 gene in parathyroid tumorigenesis, we analyzed 81 parathyroid glands from 22 Japanese uremic patients for allelic loss on chromosomal arm 11q13 DNA using 3 flanking markers (PYGM, D11S4946, and D11S449) and for mutations of the MEN1-coding exons by PCR-based single strand conformation polymorphism analysis and sequencing. Allelic loss on 11q13 was observed in 6 glands (7%), and 1 of 6 demonstrated a previously unrecognized somatic frameshift deletion (331delG) of the MEN1 gene. This mutation would probably result in a nonfunctional menin protein, consistent with a tumor suppressor mechanism. Clinical and pathological characteristics of hyperparathyroidism were unrelated to the presence or absence of loss of heterozygosity on 11q13 and MEN1 gene mutations. These observations indicate that somatic inactivation of the MEN1 gene contributes to the pathogenesis of uremia-associated parathyroid tumors, but its role in this disease appears to be very limited.

Human gelsolin prevents apoptosis by inhibiting apoptotic mitochondrial changes via closing VDAC

Gelsolin is a Ca2+-dependent actin-regulatory protein that modulates actin assembly and disassembly, and is believed to regulate cell motility through modulation of the actin network. Gelsolin was also recently suggested to be involved in the regulation of apoptosis: human gelsolin (hGsn) has anti-apoptotic activity, whereas mouse gelsolin (mGsn) exerts either proapoptotic or anti-apoptotic activity depending on different cell types. Here, we studied the basis of anti-apoptotic activity of hGsn. We showed that both endogenous and overexpressed hGsn has anti-apoptotic activity, that depends on its C-terminal half. We also found that hGsn and its C-terminal half but not mGsn could prevent apoptotic mitochondrial changes such as Apsi loss and cytochrome c release in isolated mitochondria to a similar extent as Bcl-xL, indicating that hGsn targets the mitochondria to prevent apoptosis via its C-terminal half. In the same way as anti-apoptotic Bcl-xL, which we recently found to prevent apoptotic mitochondrial changes by binding and closing the voltage-dependent anion channel (VDAC), hGsn and its C-terminal half inhibited the activity of VDAC on liposomes through direct binding in a Ca2+-dependent manner. These results suggest that hGsn inhibits apoptosis by blocking mitochondrial VDAC activity.

Bax and Bcl-xL independently regulate apoptotic changes of yeast mitochondria that require VDAC but not adenine nucleotide translocator

Mitochondria play an essential role in apoptosis by releasing apoptogenic molecules such as cytochrome c and AIF, and some caspases, which are all regulated by Bcl-2 family proteins. Pro-apoptotic Bax and Bak have been shown to induce cytochrome c release and loss of membrane potential (Deltapsi) leading to AIF release in the isolated mitochondria. We have previously shown that Bax and Bak open the voltage-dependent anion channel (VDAC) allowing cytochrome c to pass through the channel, and Bcl-xL closes the channel. However, it has been reported that it is adenine nucleotide translocator (ANT) with which Bax/Bcl-xL interacts that modulate the channel activity. Here, we investigated the role of ANT and VDAC in the changes of isolated mitochondria triggered by Bax and by chemicals that induce permeability transition (PT). In rat and yeast mitochondria, Bax did not affect the ADP/ATP exchange activity of ANT. VDAC-deficient but not ANT-deficient yeast mitochondria showed resistance to cytochrome c release, Deltapsi loss, and swelling caused by Bax and PT inducers. Bcl-xL showed similar inhibition of all these changes in ANT-deficient and wild type yeast mitochondria. Furthermore, Bax induces cytochrome c release in wild type yeast cells but not VDAC1-deficient yeast cells. These data indicate that VDAC, but not ANT, is essential for apoptotic mitochondrial changes. The data also indicate that Bcl-xL and Bax possess an ability to regulate mitochondrial membrane permeability independently of other Bcl-2 family members.

Cooperative regulation of DOG2, encoding 2-deoxyglucose-6-phosphate phosphatase, by Snf1 kinase and the high-osmolarity glycerol-mitogen-activated protein kinase cascade in stress responses of Saccharomyces cerevisiae

We screened the genome of Saccharomyces cerevisiae for the genes responsive to oxidative stress by using the lacZ transposon-insertion library. As a result, we found that expression of the DOG2 gene coding for 2-deoxyglucose-6-phosphate phosphatase was induced by oxidative stress. The expression of DOG2 was also induced by osmotic stress. We found a putative cis element (STRE, a stress response element) in the DOG2 promoter adjacent to a consensus sequence to which the Mig1p repressor is known to bind. The basal levels of DOG2 gene expression were increased in a mig1Delta mutant, while the derepression of DOG2 was not observed in a snf1Delta mutant under glucose-deprived conditions. Induction of the DOG2 gene expression by osmotic stress was observed in any of the three disruptants pbs2Delta, hog1Delta, and snf1Delta. However, the osmotic induction was completely abolished in both the snf1Delta pbs2Delta mutant and the snf1Delta hog1Delta mutant. Additionally, these single mutants as well as double mutants failed to induce DOG2 expression by oxidative stress. These results suggest that Snf1p kinase and the high-osmolarity glycerol-mitogen-activated protein kinase cascade are likely to be involved in the signaling pathway of oxidative stress and osmotic stress in regulation of DOG2.

[Renocolic fistula: a case report]

A 78-year-old woman had disregarded pneumaturia since April 1998. In March 1999, computed tomography and barium enema were done to examine anemia and positive fecal occult blood, revealing a left renocolic fistula and bilateral renal stones. Intravenous pyelography revealed a left staghorn calculus, non-functioning kidney, and right partial staghorn calculus. Urinalysis showed pyuria and the culture grew Proteus vulgaris and Klebsiella oxytoca. Smear and culture of the urine were negative for acid-fast bacilli. In consideration of the patient's age and conservation of right renal function, right pyelolithotomy was performed first. Three weeks later, left nephrectomy and partial colectomy were done. The postoperative course was uneventful. A renocolic fistula is relatively rare and to our knowledge there have been 37 cases reported in Japan, including our case. Surgery is the main therapy and was performed in 31 patients. Among them, surgery was not curative in 1 and 5 died of postoperative complications. Thus, surgery is not safe in all cases. However, despite her age and bilateral renal dysfunction, our patient was successfully operated on.

Gelsolin inhibits apoptosis by blocking mitochondrial membrane potential loss and cytochrome c release

Apoptotic cell death, characterized by chromatin condensation, nuclear fragmentation, cell membrane blebbing, and apoptotic body formation, is also accompanied by typical mitochondrial changes. The latter includes enhanced membrane permeability, fall in mitochondrial membrane potential (Deltapsi(m)) and release of cytochrome c into the cytosol. Gelsolin, an actin regulatory protein, has been shown to inhibit apoptosis, but when cleaved by caspase-3, a fragment that is implicated as an effector of apoptosis is generated. The mechanism by which the full-length form of gelsolin inhibits apoptosis is unclear. Here we show that the overexpression of gelsolin inhibits the loss of Deltapsi(m) and cytochrome c release from mitochondria resulting in the lack of activation of caspase-3, -8, and -9 in Jurkat cells treated with staurosporine, thapsigargin, and protoporphyrin IX. These effects were corroborated in vitro using recombinant gelsolin protein on isolated rat mitochondria stimulated with Ca(2+), atractyloside, or Bax. This protective function of gelsolin, which was not due to simple Ca(2+) sequestration, was inhibited by polyphosphoinositide binding. In addition we confirmed that gelsolin, besides its localization in the cytosol, is also present in the mitochondrial fraction of cells. Gelsolin thus acts on an early step in the apoptotic signaling at the level of mitochondria.

Electrophysiological study of a novel large pore formed by Bax and the voltage-dependent anion channel that is permeable to cytochrome c

The Bcl-2 family of proteins, consisting of anti-apoptotic and pro-apoptotic members, regulates cell death by controlling mitochondrial membrane permeability that is crucial for apoptotic signal transduction. We have recently shown that some of these proteins, such as Bcl-x(L), Bax, and Bak, directly modulate the mitochondrial voltage-dependent anion channel (VDAC) and thus regulate apoptogenic cytochrome c release and potential loss. To elucidate the molecular mechanisms of VDAC regulation by Bcl-2 family proteins, an electrophysiological study was carried out. It was found that VDAC and pro-apoptotic Bax created a large pore, with conductance levels 4- and 10-fold greater than those of the VDAC and Bax channels, respectively. Although the VDAC and Bax channels both show ion selectivity and voltage-dependent modulation of their activity, the VDAC-Bax channel had neither of their properties. Anti-apoptotic Bcl-x(L) and its BH4 oligopeptide completely closed the VDAC, in contrast to the Bax. Cytochrome c passed through a single VDAC-Bax channel but not through the VDAC or Bax channel in a planar lipid bilayer. These data provide direct evidence that VDAC forms a novel large pore together with Bax.

Regions essential for the interaction between Bcl-2 and SMN, the spinal muscular atrophy disease gene product

The SMN gene is implicated in spinal muscular atrophy (SMA), and its product has been shown to interact with Bcl-2 protein to enhance its anti-apoptotic activity. In this study, we determined the regions that were essential for the interaction of Bcl-2 and SMN by co-immunoprecipitation of deletion mutants. Bcl-2 lacking its amino-terminal 20 amino acid residues or its carboxyl-terminal membrane-anchoring domain showed no or greatly reduced binding with SMN, respectively. However, Bcl-2 lacking other regions could still bind to SMN. Because Bcl-2 lacking the membrane-anchoring domain could bind to SMN in a yeast two-hybrid system, the amino-terminal region of Bcl-2 seems to be the most important domain for binding with SMN. A fragment of SMN encoded by exon 6 could bind to Bcl-2, but SMN lacking this region could not. From these results, we concluded that Bcl-2 and SMN proteins bound with each other at the amino-terminal region near the BH4 domain of Bcl-2 and the region encoded by exon 6 of SMN, both regions known to be important for their function.

Identification of the dimethylbenzyl mercapturic acid in urine of rats administered with 1,2,4-trimethylbenzene

A study was undertaken of the mercapturic acid metabolism of 1,2,4-trimethylbenzene in the rat. Of three regioisomeric dimethylbenzyl mercapturic acids, i.e. 2,4-, 2,5- and 3,4-dimethylbenzyl isomers, the third isomer was not found in the urinary mercapturic acid isolated by preparative HPLC, from the comparison of NMR spectrum of the isolate with those of authentic specimens. The urinary mercapturate was then assigned to 2,4- and/or 2,5-dimethylbenzyl isomers. The excretion rate of the mercapturic acid was 14-20% of dose as 2,4-dimethylbenzyl isomer.

Determination of mercapturic acids in urine by solid-phase extraction followed by liquid chromatography-electrospray ionization mass spectrometry

A novel method for the determination of five kinds of mercapturic acids, found in urine as metabolites of alkylbenzenes, based on liquid chromatography-electrospray ionization mass spectrometry is described. A solid-phase extraction procedure was used for the extraction of the mercapturic acids from urine and the separation was performed on a reversed-phase C30 column. The detection limits were in the range 2.4-3.2 ng ml-1.

BH4 domain of antiapoptotic Bcl-2 family members closes voltage-dependent anion channel and inhibits apoptotic mitochondrial changes and cell death

A change of mitochondrial membrane permeability is essential for apoptosis, leading to translocation of apoptogenic cytochrome c and apoptosis-inducing factor into the cytoplasm. We recently showed that the Bcl-2 family of proteins regulate cytochrome c release and the mitochondrial membrane potential (Deltapsi) by directly modulating the activity of the voltage-dependent anion channel (VDAC) through binding. Here we investigated the biochemical role of the conserved N-terminal homology domain (BH4) of Bcl-x(L), which has been shown to be essential for inhibition of apoptosis, with respect to the regulation of mitochondrial membrane permeability and found that BH4 was required for Bcl-x(L) to prevent cytochrome c release and Deltapsi loss. A study using VDAC liposomes revealed that Bcl-x(L), but not Bcl-x(L) lacking the BH4 domain, inhibited VDAC activity. Furthermore, BH4 oligopeptides of Bcl-2 and Bcl-x(L), but not mutant peptides, were able to inhibit both VDAC activity on liposomes even in the presence of Bax and apoptotic Deltapsi loss in isolated mitochondria. It was also shown that the BH4 domain, fused to the protein transduction domain of HIV TAT protein (TAT-BH4), efficiently prevented apoptotic cell death. These results indicate that the BH4 of Bcl-2/Bcl-x(L) is essential and sufficient for inhibiting VDAC activity, which in turn prevents apoptotic mitochondrial changes, and for preventing apoptotic cell death. Finally, the data suggest that the TAT-BH4 peptide is potentially useful as a therapeutic agent for diseases caused by accelerated apoptosis.

Characterization of the activity of L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H-1-be nzopyran-6-yl-hydrogen phosphate] potassium salt in hydroxyl radical elimination

The effect of L-ascorbic acid 2-[3,4-dihydro-2,5,7,8-tetramethyl-2-(4,8,12-trimethyltridecyl)-2H -1-benzopyran-6-yl-hydrogen phosphate] potassium salt (EPC-K1) on hydroxyl radical (*OH) elimination was studied using electron spin resonance (ESR) and spectrophotometric experiments. The addition of EPC-K, and *OH scavengers eliminated the *OH generated from Cu2+/H2O2, Fe2+/H2O2 and H2O2/UV-irradiation reaction systems. However, in competitive reactions using different concentrations of a spin-trap agent, the addition of the *OH scavenger altered the IC50 values, whereas the addition of EPC-K1 and a metal chelater did not change the value in the Cu2+/H2O2 and Fe2+/H2O2 reaction systems. The addition of EPC-K1 and metal chelater changed the ESR signal for free Cu2+. The spectrophotometric experiments confirmed that the addition of EPC-K1 and metal chelater altered the absorption spectra due to CuCl2 and FeSO4, whereas the *OH scavenger did not alter the spectra. Therefore, it was demonstrated that EPC-K, has the ability both to scavenge *OH directly and to inhibit the generation of *OH by the chelation of Cu2+ and Fe2+.

Association of insulin receptor substrate proteins with Bcl-2 and their effects on its phosphorylation and antiapoptotic function

Insulin receptor substrate (IRS) proteins are docking proteins that couple growth factor receptors to various effector molecules, including phosphoinositide-3 kinase, Grb-2, Syp, and Nck. Here we show that IRS-1 associates with the loop domain of Bcl-2 and synergistically up-regulates antiapoptotic function of Bcl-2. IRS-2 but not IRS-3 binds to Bcl-2, and IRS-1 associates with Bcl-XL but not with Bax or Bik. Overexpression of IRS-1 suppresses phosphorylation of Bcl-2 induced by stimulation with insulin, and the hypophosphorylation may lead to its enhanced antiapoptotic activity. The binding site for Bcl-2 is located on the carboxyl half-domain of IRS-1. IRS-3, which lacks the corresponding region, dominant-negatively abrogates the survival effects of IRS-1 and Bcl-2. For the antiapoptotic activity of IRS-1, binding to Bcl-2 is more critical than activating phosphoinositide-3 kinase. Our results indicate that IRS proteins transmit signals from the insulin receptor to Bcl-2, thus regulating cell survival probably through regulating phosphorylation of Bcl-2.

Bcl-2 family: life-or-death switch

The Bcl-2 family of proteins that consists of anti-apoptotic and pro-apoptotic members determines life-or-death of a cell by controlling the release of mitochondrial apoptogenic factors, cytochrome c and apoptosis-inducing factor (AIF), that activate downstream executional phases, including the activation of death proteases called caspases. Cytochrome c release is, thus, central to apoptotic signal transduction in mammals, making study of the mechanism for cytochrome c release a major issue. Several models for cytochrome c release have been proposed, including rupture of mitochondrial outer membrane and involvement of a specific channel. Here, we provide an overview of recent findings on the role of Bcl-2 family members in the life-or-death decision of a cell.