Interactions of the amino acid residue at position 31 of the c-Ha-Ras protein with Raf-1 and RalGDS

The Ras and Rap1A proteins can bind to the Raf and RalGDS families. Ras and Rap1A have Glu and Lys, respectively, at position 31. In the present study, we analyzed the effects of mutating the Glu at position 31 of the c-Ha-Ras protein to Asp, Ala, Arg, and Lys on the interactions with Raf-1 and RalGDS. The Ras-binding domain (RBD) of Raf-1 binds the E31R and E31K Ras mutants less tightly than the wild-type, E31A, and E31D Ras proteins; the introduction of the positively charged Lys or Arg residue at position 31 specifically impairs the binding of Ras with the Raf-1 RBD. On the other hand, the ability of the oncogenic RasG12V protein to activate Raf-1 in HEK293 cells was only partially reduced by the E31R mutation but was drastically impaired by the E31K mutation. Correspondingly, RasG12V(E31K) as well as Rap1A, but not RasG12V(E31R), exhibited abnormally tight binding with the cysteine-rich domain of Raf-1. On the other hand, the E31A, E31R, and E31K mutations, but not the E31D mutation, enhanced the RalGDS RBD-binding activity of Ras, indicating that the negative charge at position 31 of Ras is particularly unfavorable to the interaction with the RalGDS RBD. RasG12V(E31K), RasG12V(E31A), and Rap1A stimulate the RalGDS action more efficiently than the wild-type Ras in the liposome reconstitution assay. All of these results clearly show that the sharp contrast between the characteristics of Ras and Rap1A, with respect to the interactions with Raf-1 and RalGDS, depends on their residues at position 31.

Prevalence of verotoxin-producing Escherichia coli harbored in the intestine of cattle in Japan

The production of verotoxin was examined in 2152 Escherichia coli isolates from 387 cattle in Japan from 1992 to 1994. The toxin was detected in 263 isolates from 94 cattle (detection rate: 24.3%). Verotoxin-producing E. coli (VTEC) was isolated from the cattle in 15 out of 17 prefectures, and the strains were divided into 33 serotypes. E. coli O157:H7 was isolated from 7 out of 387 cattle (detection rate: 1.8%) in four prefectures. These results suggest that VTEC is widely distributed in Japan and include a wide variety of serotypes.

Identification of PLC210, a Caenorhabditis elegans phospholipase C, as a putative effector of Ras

Mammalian Ras proteins regulate multiple effectors including Raf, Ral guanine nucleotide dissociation stimulator (RalGDS), and phosphoinositide 3-kinase. In the nematode Caenorhabditis elegans, LIN-45 Raf has been identified by genetic analyses as an effector of LET-60 Ras. To search for other effectors in C. elegans, we performed a yeast two-hybrid screening for LET-60-binding proteins. The screening identified two cDNA clones encoding a phosphoinositide-specific phospholipase C (PI-PLC) with a predicted molecular mass of 210 kDa, designated PLC210. PLC210 possesses two additional functional domains unseen in any known PI-PLCs. One is the C-terminal Ras-associating domain bearing a structural homology with those of RalGDS and AF-6. This domain, which could be narrowed down to 100 amino acid residues, associated in vitro with human Ha-Ras in a GTP-dependent manner and competed with yeast adenylyl cyclase for binding Ha-Ras. The binding was abolished by specific mutations within the effector region of Ha-Ras. The other functional domain is the N-terminal CDC25-like domain, which possesses a structural homology to guanine nucleotide exchange proteins for Ras. These results strongly suggest that PLC210 belongs to a novel class of PI-PLC, which is a putative effector of Ras.

Chemoprevention of N-nitroso-N-methylurea-induced rat mammary carcinogenesis by soy foods or biochanin A

We examined the effects of soybeans, a soy product (miso) and biochanin A, an isoflavone derivative, on N-nitroso-N-methylurea (MNU)-induced rat mammary carcinogenesis. Seven-week-old female CD/Crj rats received a single i.v. dose (40 mg/kg body weight) of MNU. After administration of MNU, rats were fed diet containing 0% (control), 2% or 10% soybeans, or 10% miso as a soy-supplemented diet, or 10 or 50 mg/kg biochanin A. All rats were observed for 18 weeks after MNU administration. At 18 weeks, the multiplicity (mean tumors/rat) of palpable mammary tumors was significantly decreased in the 10% soybean (1.1) and 10% miso (1.2) diet groups compared to the control (2.2) (P<0.05, respectively). In the biochanin A-supplemented diet groups, the incidence (percentage of rats with tumors) was significantly decreased in the 50 mg/kg (32%) diet group compared to the control (80%) (P<0.01), and the multiplicity was significantly decreased in both the 10 mg/kg (0.7) and 50 mg/kg (0.5) diet groups compared to the control (2.2) (P<0.01 and P<0.001, respectively). The proliferative cell nuclear antigen labeling index of mammary tumors was significantly decreased in both biochanin A-supplemented diet groups compared to the control. The present results indicate that soybeans, miso, and biochanin A are useful for the prevention of mammary cancer.

Cholesterol-lowering effects of psyllium seed associated with urea metabolism

Twenty-eight mild hypercholesterolemic male and female adults were orally administered psyllium seed for 3 months. After psyllium treatment, the serum total cholesterol, low-density-lipoprotein-cholesterol and atherogenic index significantly decreased, but levels of high-density-lipoprotein-cholesterol, triglyceride and urea nitrogen did not. To determine the parameters associated with the cholesterol-lowering effect in the subjects' backgrounds, both biochemical and hematological parameters, we statistically examined the correlation between pretreatment parameters and the absolute change of total cholesterol level. The absolute change of total cholesterol level showed a direct correlation with the triglyceride level at pretreatment (r=0.41, P=0.03) and had an inverse correlation with urea nitrogen level (r=-0.46, P=0.01) but not with the total cholesterol level (r=-0.18). The change in urea nitrogen level had an inverse correlation with the urea nitrogen level itself at pretreatment (r=-0.82, P=7 x 10[-8]) and had a direct correlation with the triglyceride level (r=0.43, P=0.02). The change in triglyceride level had an inverse correlation with the urea nitrogen level (r=-0.48, P=0.008). Furthermore, the change in total cholesterol level had direct correlations with changes in the triglyceride level (r=0.56, P=0.002) and the urea nitrogen level (r=0.51, P=0.006), but these changes in triglyceride and urea nitrogen level did not correlate significantly. These findings suggest the close association of urea nitrogen and lipid metabolism in hyperlipidemia and psyllium seed treatment.

Synthesis and structure-activity relationship of 3-Substituted benzamide, benzo [b]furan-7-carboxamide, 2,3-dihydrobenzo[b]furan-77-carboxamide, and indole-5-carboxamide derivatives as selective serotonin 5-HT4 receptor agonists

The title compounds (6-9) were prepared and evaluated for serotonin 5-HT4 agonistic activity in in vitro tests. Introducing a propyl or allyl group at the 3-position of benzamide caused only a slight enhancement of agonistic activity. Construction of the benzo[b]furan skeleton and 2,3-dihydrobenzo[b]furan skeleton caused a significant enhancement of the activity. 4-amino-N-[2-(1-azabicyclo[3.3.0]octan-5-yl)ethyl]-5-chloro- 2-methylbenzo[b]furan-7-carboxamide (7b) hemifumarate was as potent as cisapride. 4-Amino-N-[2-(1-azabicyclo[3.3.0]octan-5-yl)ethyl]-5-chloro- 2,3-dihydro-2-methylbenzo[b]furan-7-carboxamide (8a) hemifumarate, 4-amino-N-[2-(1-azabicyclo[3.3.0]octan-5-yl)ethyl]-5-chloro- 2,3-dihydro-2-ethylbenzo[b]furan-7-carboxamide (8c) hemifumarate, and 4-amino-N-[2-(1-azabicyclo[3.3.0]octan-5-yl)ethyl]-5-chloro- 2,3-dimethylbenzo[b]furan-7-carboxamide (8d) hemifumarate were more potent than cisapride. Furthermore, 8a hemifumarate was free from dopamine D1, D2, serotonin 5-HT1, 5-HT2 and muscarine M1, M2 receptor binding activity in the in in vitro tests. On the other hand, construction of the indole skeleton caused a remarkable decrease in activity.

Membrane recruitment of Raf-1 is not the only function of Ras in Raf-1 activation

Ras interacts with Raf-1 and stimulates its kinase activity, which results in activation of the mitogen-activated protein (MAP) kinase cascade. It has been proposed that the main function of Ras in Raf-1 activation is to recruit Raf-1 to the plasma membrane, where a separate activation event such as phosphorylation takes place. Here, we examined the activities of various mutants of human Ha-Ras to induce membrane translocation of Raf-1 and to activate Raf-1 in vivo. Overexpression of an activator region mutant Ha-Ras(V45E) in COS7 cells induced membrane translocation of Raf-1 as effectively as wild-type Ha-Ras. However, the activity of this mutant to activate Raf-1 and extracellular signal-regulated kinase-2 (ERK2) was attenuated by approximately 70% compared to that of wild-type Ha-Ras. The decrease in the specific activity was further demonstrated by measuring the activity of the Ha-Ras(V45E)-associated Raf-1 purified from the membrane fraction. These results imply that the association of Ras with Raf-1 has another important consequence, presumably dependent on the interaction between its activator region and Raf-1, than the simple recruitment of Raf-1 to the plasma membrane.

TRAIL receptors 1 (DR4) and 2 (DR5) signal FADD-dependent apoptosis and activate NF-kappaB

TRAIL induces apoptosis through two closely related receptors, TRAIL-R1 (DR4) and TRAIL-R2 (DR5). Here we show that TRAIL-R1 can associate with TRAIL-R2, suggesting that TRAIL may signal through heteroreceptor signaling complexes. Both TRAIL receptors bind the adaptor molecules FADD and TRADD, and both death signals are interrupted by a dominant negative form of FADD and by the FLICE-inhibitory protein FLIP. The recruitment of TRADD may explain the potent activation of NF-kappaB observed by TRAIL receptors. Thus, TRAIL receptors can signal both death and gene transcription, functions reminiscent of those of TNFR1 and TRAMP, two other members of the death receptor family.

[Pulmonary metastasis after resection of non-invasive thymoma: a case report--analysis of nuclear DNA pattern and pathological findings]

After resection of a non-invasive thymoma, two metastatic lung tumors were found in the left upper lobe and the left lower lobe. There were differences in tumor doubling time (TDT) and invasion between the metastatic tumor in the lower lobe and the one in the upper lobe. The TDTs of the tumors were 834.1 days and 328.3 days, and the tumor of the left lower lobe invaded the left lateral basal segmental bronchus (B9). The differences in the two tumors were determined by pathological findings and nuclear DNA pattern. Pathologically, the resected thymoma and both of the metastatic tumors were mixed type, which consisted of epithelial cells and lymphocytes. But by epithelium form, the resected thymoma and the tumor in the lower lobe were classified as cortex type, and only the slow growing tumor in the upper lobe contained a spindle-cell component. The DNA pattern of the resected thymoma was aneuploid and the two metastatic tumors were diploid. As this case is very interesting clinically and pathologically, we reported it.

Immunosuppressive effects of gallic acid and chebulagic acid on CTL-mediated cytotoxicity

Gallic acid (GA) and chebulagic acid (CA) were isolated from the extract of a herbal medicine, kashi (myrobalans: the fruit of Terminalia chebula) as active principles that blocked the cytotoxic T lymphocyte (CTL)-mediated cytotoxicity. GA and CA inhibited the killing activity of CD8+ CTL clone at IC50 values of 30 microM and 50 microM, respectively. Granule exocytosis in response to anti-CD3 stimulation was also blocked by GA and CA at the equivalent concentrations.

N-[2-(1-azabicyclo[3.3.0]octan-5-yl)ethyl]-2-nitroaniline, a potent muscarinic agonist

The muscarine receptor agonist SK-946, an aniline derivative with a characteristic bicyclo amine, was found. We describe a new synthetic method for 1-azabicyclo[3.3.0]octane and describe the biological activity of SK-946.

Inactivation and proteolytic degradation of perforin within lytic granules upon neutralization of acidic pH

In our recent studies, an inhibitor of vacuolar-type H(+)-ATPase, concanamycin A (CMA) has been shown to neutralize acidic pH in vacuolar organelles, including lytic granules, and to decrease the perforin content markedly. In the present paper, we have further investigated the role of acidification in perforin storage by using CMA. In CD8+ cytotoxic T-lymphocyte (CTL) clones, the amount of perforin decreased rapidly at 30-90 min but no more decrease occurred at 90-120 min after the addition of CMA. Since exposure to actinomycin D, cycloheximide, or brefeldin A failed to reduce the perforin content, the perforin decrease in CMA-treated cells seems to be largely due to a reduction in the perforin already stored in lytic granules, rather than to the inhibition of the de novo synthesis or the intracellular glycoprotein transport of perforin. Diisopropylfluorophosphoridate (DFP) markedly antagonized the decrease in the perforin content in CMA-treated cells, while other protease inhibitors, i.e. antipain, E-64, leupeptin, pepstatin A and phenylmethylsulphonyl fluoride, did not. Nevertheless, DFP hardly reversed the abrogation of the killing activity by CMA. Indeed, the lytic granules prepared from DFP plus CMA-treated cells showed only a marginal level of haemolytic activity. In cell-free experiments using perforin-enriched granule fractions, acidic pH completely blocked the perforin activity. Under the acidic conditions, perforin was more resistant to an inactivation by calcium when exposed to calcium prior to the haemolysis test. Thus, these data suggest that perforin is primarily inactivated, possibly in a calcium-dependent manner, and is subsequently hydrolysed by DFP-sensitive proteases in the lytic granules at neutral pH. We conclude that acidic pH plays an essential role to maintain the integrity of perforin within the lytic granules.

Coassociation of Rap1A and Ha-Ras with Raf-1 N-terminal region interferes with ras-dependent activation of Raf-1

Raf-1 is a major downstream effector of mammalian Ras. Binding of the effector domain of Ras to the Ras-binding domain of Raf-1 is essential for Ras-dependent Raf-1 activation. However, Rap1A, which has an identical effector domain to that of Ras, cannot activate Raf-1 and even antagonizes several Ras functions in vivo. Recently, we identified the cysteine-rich region (CRR) of Raf-1 as another Ras-binding domain. Ha-Ras proteins carrying mutations N26G and V45E, which failed to bind to CRR, also failed to activate Raf-1. Since these mutations replace Ras residues with those of Rap1A, we examined if Rap1A lacks the ability to bind to CRR. Contrary to the expectation, Rap1A exhibited a greatly enhanced binding to CRR compared with Ha-Ras. Enhanced CRR binding was also found with Ha-Ras carrying another Rap1A-type mutation E31K. Both Rap1A and Ha-Ras(E31K) mutant failed to activate Raf-1 and interfered with Ha-Ras-dependent activation of Raf-1 in Sf9 cells. Enhanced binding of Rap1A to CRR led to co-association of Rap1A and Ha-Ras with Raf-1 N-terminal region through binding to CRR and Ras-binding domain, respectively. These results suggest that Rap1A interferes with Ras-dependent Raf-1 activation by inhibiting binding of Ras to Raf-1 CRR.

Characterization of the carrot beta-tubulin gene coding a divergent isotype, beta-2

Four different beta-tubulin clones were isolated from carrot genomic and cDNA libraries. Their nucleotide sequences were determined 1 and their predicted amino acids were compared with each other. The predicted amino acid composition of the C-terminal region of three of them (beta-1, 3, 4) resembled one another, but that of one isotype (beta-2) was divergent. The beta-2 tubulin included two hydroxyl amino acids, serine and threonine, and consisted of a lower number of negatively charged amino acids than the others in the C-terminal region. The predicted hydrophobicity profile of the beta-2 tubulin around the residue 200 is less hydrophobic than beta-1, but it is still more hydrophobic than those of animal and fungal beta-tubulins. The beta-2 gene was transcribed in cultured cells and flowers, while the beta-1 gene was ubiquitously transcribed in cultured cells, roots, shoots and flowers. When the predicted amino acids of plant tubulin were compared with those of other organisms, substitutions from non-polar amino acids to those with hydroxyl group were conspicuous in the region corresponding to the third exon in the plant genes.

Association of elongation factor 1 alpha and ribosomal protein L3 with the proline-rich region of yeast adenylyl cyclase-associated protein CAP

CAP is a multifunctional protein; the N-terminal region binds adenylyl cyclase and controls its response to Ras while the C-terminal region is involved in cytoskeletal regulation. In between the two regions, CAP possesses two proline-rich segments, P1 and P2, resembling a consensus sequence for binding SH3 domains. We have identified two yeast proteins with molecular sizes of 48 and 46 kDa associated specifically with P2. Determination of partial protein sequences demonstrated that the 48-kDa and 46-kDa proteins correspond to EF1 alpha and rL3, respectively, neither of which contains any SH3-domain-like sequence. Deletion of P2 from CAP resulted in loss of the activity to bind the two proteins either in vivo or in vitro. Yeast cells whose chromosomal CAP was replaced by the P2-deletion mutant displayed an abnormal phenotype represented by dissociated localizations of CAP and F-actin, which were colocalized in wild-type cells. These results suggest that these associations may have functional significance.

Characterization of a series of vacuolar type H(+)-ATPase inhibitors on CTL-mediated cytotoxicity

Four vacuolar type H(+)-ATPase (V-ATPase) inhibitors, i.e. concanamycin A (CMA), bafilomycin A1 (BMA), destruxin E (DRE) and prodigiosin 25-C (PRG) profoundly blocked the perforin-dependent cytotoxicity mediated by CD8+ CTL clone. Cytoplasmic acidic compartments were not detected under fluorescent microscopy after treatment of the cells with these V-ATPase inhibitors. In the lytic granule fractions, BMA, CMA, DRE and PRG completely abrogated the perforin activity, although these drugs slightly decreased the granzyme A activity. Under the same conditions, BMA and CMA markedly reduced the perforin content, while DRE and PRG had no significant effects as assayed by immunoblotting using anti-perforin antibody. These data suggest that perforin is predominantly inactivated even without proteolysis in DRE- or PRG-treated cells. We propose that acidic pH is essential to maintain not only quantity but also quality of perform in the lytic granules.

Effect of association with adenylyl cyclase-associated protein on the interaction of yeast adenylyl cyclase with Ras protein

Posttranslational modification of Ras protein has been shown to be critical for interaction with its effector molecules, including Saccharomyces cerevisiae adenylyl cyclase. However, the mechanism of its action was unknown. In this study, we used a reconstituted system with purified adenylyl cyclase and Ras proteins carrying various degrees of the modification to show that the posttranslational modification, especially the farnesylation step, is responsible for 5- to 10-fold increase in Ras-dependent activation of adenylyl cyclase activity even though it has no significant effect on their binding affinity. The stimulatory effect of farnesylation is found to depend on the association of adenylyl cyclase with 70-kDa adenylyl cyclase-associated protein (CAP), which was known to be required for proper in vivo response of adenylyl cyclase to Ras protein, by comparing the levels of Ras-dependent activation of purified adenylyl cyclase with and without bound CAP. The region of CAP required for this effect is mapped to its N-terminal segment of 168 amino acid residues, which coincides with the region required for the in vivo effect. Furthermore, the stimulatory effect is successfully reconstituted by in vitro association of CAP with the purified adenylyl cyclase molecule lacking the bound CAP. These results indicate that the association of adenylyl cyclase with CAP is responsible for the stimulatory effect of posttranslational modification of Ras on its activity and that this may be the mechanism underlying its requirement for the proper in vivo cyclic AMP response.

Synergistic activation of c-fos promoter activity by Raf and Ral GDP dissociation stimulator

Ral, a member of small GTP-binding protein (G protein) superfamily, has been suggested to act downstream of Ras, since Ral GDP dissociation stimulator (RalGDS) has been found to be an effector protein of Ras. In this study, we examined the effects of RalGDS and Ral on gene expression using c-fos promoter linked to the luciferase reporter gene (c-fos-luciferase). RalGDS interacted with RasG12V/E37G (in which Gly-12 and Glu-37 were changed to Val and Gly, respectively) which failed to bind to Raf in COS cells. RafCAAX is an active Raf kinase targeted to the plasma membranes by virtue of the addition of a C-terminal localization signal from K-Ras. Transfection of either RalGDS or RafCAAX into NIH3T3 cells slightly stimulated c-fos-luciferase expression and cotransfection of both proteins greatly enhanced the expression. RalGDS and an activated Rac (RacG12V) did not act synergistically to stimulate c-fos-luciferase expression. Transfection of an activated Ral (RalG23V) stimulated c-fos-luciferase expression. Furthermore, cotransfection of RalG23V and an activated Ras (RasG12V) enhanced RasG12V-dependent c-fos-luciferase expression. However, RalG23V did not synergize with RafCAAX, RacG12V or RalGDS to stimulate the expression. These results show that RalGDS and Ral regulate c-fos promoter activity and suggest that RalGDS may activate c-fos promoter synergistically with the signal from Raf by transmitting the signal to a target other than Ral.

Prodigiosin 25-C and metacycloprodigiosin suppress the bone resorption by osteoclasts

Prodigiosin 25-C and metacycloprodigiosin were found to suppress PTH-stimulated pit formation by cultured osteoclasts on bone slices. They also inhibited the acidification of vacuolar organelles in intact osteoclastic cells. Since the acidic pH in these organelles is generated by the action of proton-pumping ATPases of the organelle, these results indicate that the proton-pumping activity of V-ATPase in osteoclastic cells is essential in bone resorption and that the inhibition of the acidification of vacuolar organelles by prodigiosins results in suppression of PTH-stimulated bone resorption.

Responses to arm exercise in patients with compensated heart failure

PURPOSE

This study compares the responses of 20 male patients (mean age 51 +/- 11 years) with stable heart failure during peak and submaximal arm and leg exercise.

METHODS

On day 1, subjects completed two symptom-limited graded exercise tests, one with their arms and one with their legs. On day 2, subjects performed arm only and leg only exercise at a matched power output of 30 Watts (W). Ten age-matched healthy subjects served as controls.

RESULTS

During peak arm exercise power output, oxygen consumption (VO2), ventilation, and rate-pressure product were higher in healthy subjects than in patients with heart failure. However, when a subject's peak VO2 or power output during arm exercise was expressed as a percentage of that achieved during peak leg exercise, no significant differences were noted between patients with heart failure and healthy subjects. Among both groups, rate-pressure product, VO2, ventilation, the ventilatory equivalent for O2, and respiratory exchange ratio were all higher when exercising at 30 W with the arms versus 30 W with the legs. Also, in patients with heart failure heart rate was higher (+6 min-1) and stroke volume index lower (-4 mL/m2) during submaximal arm than leg exercise.

CONCLUSIONS

Although peak exercise capacity (Watts, VO2) during arm exercise is lower in patients with heart failure than healthy subjects, when expressed as a percentage of peak leg capacity, the extent of the exercise intolerance they experience during arm exercise does not differ from healthy subjects.

Suppression of apoptotic cell death of IL-3-dependent cell lines by ER/SR Ca2+-ATPase inhibitors upon IL-3 deprivation

An ER/SR Ca2+-ATPase inhibitor, cyclopiazonic acid (CPA), was found to suppress apoptotic cell death of IL-3-dependent cell lines, FDC.P2, IC-2, and Ba/F3, upon IL-3 deprivation. Structurally unrelated ER/SR Ca2+-ATPase inhibitors, thapsigargin and 2,5-di(tert-butyl)-1,4-benzohydroquinone also maintained cell viability in the absence of IL-3. In the Ca2+-free medium CPA failed to suppress apoptosis, suggesting that the anti-apoptotic activity of CPA is dependent on extracellular calcium. The culture supernatant of CPA-treated cells was able to prolong cell survival of FDC.P2 in the absence of IL-3. An anti-IL-4 antibody almost completely eliminated the anti-apoptotic activity of CPA. Indeed, a significant amount of IL-4 was detected in the supernatant of cells treated with ER/SR Ca2+-ATPase inhibitors. Thus, our present data clearly demonstrate not only that ER/SR Ca2+-ATPase inhibitors induce the secretion of IL-4 in IL-3-dependent cell lines, but also that IL-4 can replace IL-3 in protecting these cells from apoptotic cell death in an autocrine manner.

Identification of low molecular weight probes on perforin- and Fas-based killing mediated by cytotoxic T lymphocytes

Perforin- and Fas-based killing pathways are two major mechanisms of cytotoxic T lymphocytes (CTL)-mediated cytotoxicity. In this paper, we have reported the identification of low molecular weight probes on CTL-mediated cytolysis. In addition to inhibitors of acidification so far reported, three other groups of compounds have been identified to block perforin-based cytolysis by the CD8+ CTL clone: (1) an inhibitor of actin polymerization (cytochalasin D), (2) respiratory inhibitors (antimycin A and oligomycin A), and (3) protein kinase inhibitors (calphostin C, herbimycin A, K252a, and staurosporine). Since Fas-based cytolysis by CD4+ CTL clone was inhibitable or rather increased by these agents, only vacuolar type H(+)-ATPase inhibitors such as concanamycin A have been shown to be highly specific probes to block perforin-based CTL-mediated cytotoxicity.

Estimation of pH and the number of lytic granules in a CD8+ CTL clone treated with an inhibitor of vacuolar type H(+)-ATPase concanamycin A

A vacuolar type H(+)-ATPase inhibitor, concanamycin A (CMA), raised the pH and induced morphologic changes such as vacuolation in lytic granules in the CD8+ cytotoxic T lymphocyte clone OE4. Here we measured the pH in lytic granules present in OE4 by immunoelectron microscopic observation using (3-(2,4-dinitroanilino)-3'-amino-N-methyldipropylamine (DAMP) as a pH probe. In control OE4, only the peripheral region, but not cores, were heavily stained with DAMP. Exposure to 100 nM CMA for 60 min raised the pH in the lytic granules from 5.7 +/- 0.2 to 6.8 +/- 0.2. Furthermore, the number of lytic granules in OE4 was estimated under phase contrast microscopy after Wright staining. About 20 lytic granules in average were detected in control cells, while CMA induced vacuolation and decreased their number by 20 to 30%.

Changes of plasma levels of human growth hormone with age in relation to mammary tumour appearance in whey acidic protein/human growth hormone (mWAP/hGH) transgenic female and male mice

Plasma levels of human growth hormone (hGH) were determined in female and male transgenic mice with human growth hormone fusion gene driven by the promoter of mouse whey acidic protein (mWAP/hGH) at 3, 6 and 9 months of age and at mammary tumour appearance. In female transgenic mice developing mammary tumours, the plasma hGH level decreased markedly upon tumour appearance, which was associated with little change in body weight. In contrast, the hGH level changed little in transgenic male mice with tumours. In female and male transgenic mice without mammary tumours, the pattern of the change of hGH levels was variable; some showed high levels at all three time points (3, 6, and 9 months) and others had none or high levels at one or two time points.

Difference in the mechanism of interaction of Raf-1 and B-Raf with H-Ras

Ras is known to possess multiple cellular targets including Raf-1. Here, we measured both direct binding of various H-Ras mutants to two representative mammalian Ras targets, Raf-1 and B-Raf, and the activity of the mutants to stimulate Raf-1 and B-Raf, and analysed the difference in their Ras-interaction mechanisms. B-Raf was shown to share almost the same H-Ras binding-specificity with Raf-1 by examining binding of the H-Ras mutants to Raf-1 and B-Raf in the yeast two-hybrid and in vitro binding assays. Mutants, Y32F, A59E, and V45E bound to Raf-1 in Sf9 cells coexpressing them, but failed to activate Raf-1. On the other hand, Y32F activated B-Raf in a cell-free system which consisted of rat brain cytosol and recombinant MEK. These results suggest that there is a subtle structural difference in requirements for the interaction of Ras with Raf-1 and B-Raf.

Exercise training in patients with heart failure. A randomized, controlled trial

OBJECTIVE

To assess the benefit of exercise training in patients with heart failure caused by left ventricular systolic dysfunction and to further describe the physiologic changes associated with exercise training in these patients.

DESIGN

Randomized, controlled trial.

SETTING

Urban outpatient clinic.

PATIENTS

40 men with compensated heart failure who were receiving standard medical therapy were randomly assigned to an exercise-training group or to a control group that did not exercise. Fifteen of the 21 patients assigned to exercise training and 14 of the 19 patients assigned to the control group completed the study.

INTERVENTION

Patients assigned to exercise training participated in a program of three exercise sessions per week for 24 weeks.

MEASUREMENTS

Symptom-limited exercise tests with gas exchange analysis done just before randomization, at week 12, and at week 24.

RESULTS

At week 24, the following changes (mean +/- SE) were seen in patients in the exercise group and patients in the control group, respectively; exercise duration, 2.8 +/- 0.6 minutes and 0.5 +/- 0.5 minutes; peak oxygen consumption (VO2), 231 +/- 54 L/min and 58 +/- 38 L/min; peak ventilation, 12 +/- 3 L/min and -4 +/- 3 L/min; peak heart rate, 10 +/- 4 beats/min and -2 +/- 4 beats/min; and peak power output, 20 +/- 6 W and 2 +/- 5 W. Differences between the increases occurring in the exercise group and the changes occurring in the control group were significant (P < 0.05). Among patients in the exercise group, 85% of the increase in peak VO2 occurred by week 12, and 46% of the increase in peak VO2 was caused by the increase in peak heart rate.

CONCLUSION

Exercise training does not appear to be contraindicated in patients with compensated heart failure. Exercise training improved exercise tolerance, as measured by increases in peak VO2, exercise duration, and power output. This improved exercise tolerance was caused in part by an increase in peak heart rate.

Concanamycin A, a powerful tool for characterization and estimation of contribution of perforin- and Fas-based lytic pathways in cell-mediated cytotoxicity

Perforin- and Fas-based cytolytic pathways are two major mechanisms of cell-mediated cytotoxicity. Recently, we have shown that an inhibitor of vacuolar type H+-ATPase, concanamycin A (CMA), inhibits perforin-based cytotoxic activity, mostly due to accelerated degradation of perforin by an increase in the pH of lytic granules. Here we show that CMA failed to inhibit the cytolytic activity of CD4+ CTL clone and perforin-deficient CD8+ CTL clone, which exclusively mediate Fas-based cytotoxicity, although CMA inhibited acidification and induced drastic vacuolation of cytoplasmic granules in these clones. In a wide range of alloantigen-specific CTL, a significant amount of the lysis of Con A blasts from normal mice and of Fas-positive tumor cells remained unaffected even in excess concentrations of CMA. However, CMA almost completely inhibited the lysis of Con A blasts from lpr mice and of Fas low expressing or negative tumor cells. Cytolysis by alloantigen-specific CD8+ CTL derived from gld mice was completely prevented by CMA. Furthermore, CMA-insensitive cytolysis exerted by CD8+ CTL clone was completely inhibitable by soluble Fas molecules. Thus, these data clearly indicate not only that CMA-insensitive cytolysis mediated by alloantigen-specific CTL is Fas dependent, but also that CMA is a selective inhibitor to block only the perforin-based killing pathway. In contrast, brefeldin A blocked the Fas-based cytotoxicity, but only marginally reduced the perforin-based cytotoxicity. Moreover, CMA and brefeldin A in combination completely abrogated all cytolytic activity of alloantigen-specific CTL. Taken together, these results reveal that CTL mainly exert perforin-based cytotoxicity and complementary Fas-based cytotoxicity, and that CMA is a powerful tool to clarify the contributions of the two distinct cytolytic pathways.

Concanamycin A, a powerful tool for characterization and estimation of contribution of perforin- and Fas-based lytic pathways in cell-mediated cytotoxicity

Perforin- and Fas-based cytolytic pathways are two major mechanisms of cell-mediated cytotoxicity. Recently, we have shown that an inhibitor of vacuolar type H+-ATPase, concanamycin A (CMA), inhibits perforin-based cytotoxic activity, mostly due to accelerated degradation of perforin by an increase in the pH of lytic granules. Here we show that CMA failed to inhibit the cytolytic activity of CD4+ CTL clone and perforin-deficient CD8+ CTL clone, which exclusively mediate Fas-based cytotoxicity, although CMA inhibited acidification and induced drastic vacuolation of cytoplasmic granules in these clones. In a wide range of alloantigen-specific CTL, a significant amount of the lysis of Con A blasts from normal mice and of Fas-positive tumor cells remained unaffected even in excess concentrations of CMA. However, CMA almost completely inhibited the lysis of Con A blasts from lpr mice and of Fas low expressing or negative tumor cells. Cytolysis by alloantigen-specific CD8+ CTL derived from gld mice was completely prevented by CMA. Furthermore, CMA-insensitive cytolysis exerted by CD8+ CTL clone was completely inhibitable by soluble Fas molecules. Thus, these data clearly indicate not only that CMA-insensitive cytolysis mediated by alloantigen-specific CTL is Fas dependent, but also that CMA is a selective inhibitor to block only the perforin-based killing pathway. In contrast, brefeldin A blocked the Fas-based cytotoxicity, but only marginally reduced the perforin-based cytotoxicity. Moreover, CMA and brefeldin A in combination completely abrogated all cytolytic activity of alloantigen-specific CTL. Taken together, these results reveal that CTL mainly exert perforin-based cytotoxicity and complementary Fas-based cytotoxicity, and that CMA is a powerful tool to clarify the contributions of the two distinct cytolytic pathways.

Immunosuppressive activity of streptonigrin in vitro and in vivo

The immune system is composed of various cells with distinct functions. Thus, highly selective immunomodulators are necessary for artificial regulation of immune reactions. We screened microbial products for such immunomodulators and we identified streptonigrin as a selective suppressor of B-cell proliferation induced by lipopolysaccharide. Streptonigrin directly suppressed the late phase of proliferation of B-cells. The inhibition of topoisomerase II was implicated as the mechanism of the B-cell-selective suppression. In cultured cell lines, however, streptonigrin preferentially suppressed the growth of an interleukin-3-dependent myeloid cell line rather than B-cell lines. In addition, the treatment with streptonigrin in vivo suppressed T-cells more significantly than B-cells and dramatically reduced the spleen weight. These results suggest that streptonigrin preferentially suppresses myeloid T-cell precursors in vivo.

Differential structural requirements for interaction of Ras protein with its distinct downstream effectors

Ras proteins have multiple effectors of distinct structures that do not share significant structural homology at their Ras interaction sites. To prove possible differences in their recognition mechanisms of Ras, we screened 44 human Ha-Ras proteins carrying mutations in the effector region and its flanking sequences for interaction with human Raf-1, Schizosaccharomyces pombe Byr2, and Saccharomyces cerevisiae adenylyl cyclase. The Ras binding specificities were largely shared between Raf-1 and Byr2 although Ras mutants, Y32F, T35S, and A59E, had their affinities for Byr2 selectively reduced. The only exception was Ras(D38N), which lost the ability to bind Raf-1 while retaining the activity to bind Byr2 and complement the Byr2- phenotype of S. pombe. On the other hand, adenylyl cyclase had quite distinct requirements for Ras residues; mutations P34G and T58A selectively abolished the ability to bind and activate it without considerably affecting the interaction with Raf-1 and Byr2. Y32F mutant, whereas losing the ability to activate Raf-1 and Byr2, could activate adenylyl cyclase efficiently. In addition, V45E mutation was found to impair the ability of Ras to activate both Raf-1 and adenylyl cyclase without significantly affecting the binding affinities for them. These results demonstrate that significant differences exist in the recognition mechanisms by which the three effector molecules associate with Ras and suggest that a region of Ras required for activation of the effectors in general may exist separately from that for binding the effectors.

Post-translational modification of H-Ras is required for activation of, but not for association with, B-Raf

B-Raf is regulated by Ras protein and acts as a mitogen-activated protein (MAP) kinase kinase kinase in PC12 cells and brain. Ras protein undergoes a series of post-translational modifications on its C-terminal CAAX motif, and the modifications are critical for its function. To elucidate the role of the post-translational modifications in interaction with, and activation of, B-Raf, we have analyzed a direct association between H-Ras and B-Raf, and constructed an in vitro system for B-Raf activation by H-Ras. By using methods based on inhibition of yeast adenylyl cyclase or RasGAP activity and by in vitro binding assays, we have shown that the segment of B-Raf corresponding to amino acid 1-326 binds directly to H-Ras with a dissociation constant (Kd) comparable to that of Raf-1 and that the binding is not significantly affected by the post-translational modifications. However, when the activity of B-Raf to stimulate MAP kinase was measured by using a cell-free system derived from rat brain cytosol, we observed that the unmodified form of H-Ras possesses an almost negligible activity to activate B-Raf in vitro compared to the fully modified form. H-RasSer-181,184 mutant, which was farnesylated but not palmitoylated, was equally active as the fully modified form. These results indicate that the post-translational modifications, especially farnesylation, are required for H-Ras to activate B-Raf even though they have no apparent effect on the binding properties of H-Ras to B-Raf.

Telomerase activity in human breast tumors

BACKGROUND

The activity of the ribonucleoprotein enzyme telomerase is not detected in normal somatic cells; thus, with each cell division, the ends of chromosomes consisting of the telomeric repeats TTAGGG progressively erode. The current model gaining support is that telomerase activity in germline and immortal cells maintains telomere length and thus compensates for the "end-replication problem."

PURPOSE

Our objective was to determine when telomerase activity is reactivated in the progression to malignant breast cancer and if knowledge of telomerase activity may be an indicator for the diagnosis and potential treatment of breast cancer.

METHODS

Using a polymerase chain reaction-based telomerase activity assay, we examined telomerase activity in 140 breast cancer specimens (from 140 patients), four phyllodes tumors (from four patients), 38 noncancerous lesions (20 fibroadenomas, 17 fibrocystic diseases, one gynecomastia; from 38 patients), and 55 adjacent noncancerous mammary tissues (from 55 of the 140 breast cancer patients). In addition, 33 fine-needle-aspirated breast samples (from 33 patients) were analyzed.

RESULTS

Among surgically resected samples, telomerase activity was detected in 130 (93%) of 140 breast cancers. Telomerase activity was detected in 68% of stage I primary breast cancers, in 73% of cancers smaller than 20 mm, and in 81% of axillary lymph node-negative cancers. Moreover, the activity was detected in more than 95% of advanced stage tumors but in only two (4%) of 55 adjacent noncancerous tissues. While telomerase activity was not detected in any of 17 specimens of fibrocystic disease, surprisingly low levels of telomerase activity were detected in nine (45%) of 20 fibroadenomas. Among samples obtained by fine-needle aspiration, 14 (100%) of 14 patients whose fine-needle-aspirated specimen contained telomerase activity and who subsequently underwent surgery were confirmed to have breast cancer. Multivariate analysis of 125 specimens from patients for whom data were available on age at surgery, stage of disease, tumor size, lymph node status tumor histology, and menopausal status indicated that stage classification exhibited the strongest association with telomerase activity (for stage I versus stages II-IV: odds ratio = 1.0 versus 73.4; 95% confidence interval = 2.0-959.0; P = .02).

CONCLUSION

Telomerase activity was detected in more than 95% of advanced stage breast cancers. It was absent in 19%-32% of less advanced cancers. Since a determination of any association between telomerase activity and patient survival is not possible at the present time, it remains to be determined whether lack of telomerase activity predicts for favorable outcome.

Structure-activity relationship within a series of degradation products of tautomycin

Tautomycin, a protein serine/threonine phosphatase inhibitor, was chemically degraded, and five derivatives were investigated for their biological activities. None of them exerted any inhibitory effects on the activity of protein phosphatase types 1 and 2A. However, one derivative, named TM2a, induced a significant morphological change (bleb-formation) of human myeloid leukemia K562 cells. TM2b, the trimethyl ester of TM2, did not induce bleb-formation. Thus, the maleic anhydride structure played an important role in the biological activity. The biological properties of TM2a toward K562 cells resembled those of a phorbol ester, rather than of tautomycin. The phorbol ester-induced bleb formation was abrogated by a non-specific inhibitor of protein kinases, staurosporine, and by an inhibitor of protein kinase C (PKC), H-7, but TM2a-induced bleb formation was abrogated only by staurosporine. Enhanced phosphorylation of the two proteins was observed after their exposure to TM2a. This suggest that the effect was not due to any inhibition of protein phosphatase 1 or 2A, but rather to the activation of an unidentified kinase, possibly of the PKC family, or to inhibition of a protein phosphatase other than type 1 or 2A.

Cysteine-rich region of Raf-1 interacts with activator domain of post-translationally modified Ha-Ras

The interaction between "switch I/effector domain" of Ha-Ras and the Ras-binding domain (RBD, amino acid 51-131) of Raf-1 is essential for signal transduction. However, the importance of the "activator domain" (approximately corresponding to amino acids 26-28 and 40-49) of Ha-Ras and of the "cysteine-rich region" (CRR, amino acids 152-184) of Raf-1 have also been proposed. Here, we found that Raf-1 CRR interacts directly with Ha-Ras independently of RBD and that participation of CRR is necessary for efficient Ras-Raf binding. Furthermore, Ha-Ras carrying mutations (N26G and V45E) in the activator domain failed to bind CRR, whereas they bound RBD normally. On the contrary, Ha-Ras carrying mutations in the switch I/effector domain exhibited severely reduced ability to bind RBD, whereas their ability to bind CRR was unaffected. Mutants that bound to either RBD or CRR alone failed to activate Raf-1. Ha-Ras without post-translational modifications, which lacks the ability to activate Raf-1, selectively lost the ability to bind CRR. These results suggest that the activator domain of Ha-Ras participates in activation of Raf-1 through interaction with CRR and that post-translational modifications of Ha-Ras are required for this interaction.

Costunolide and dehydrocostus lactone as inhibitors of killing function of cytotoxic T lymphocytes

Costunolide and dehydrocostus lactone were isolated from an extract of mokko (Saussurea lappa Clarke) as inhibitors of killing activity of cytotoxic T lymphocytes (CTL). Mokko lactone was also isolated as an inactive compound from the extract. The structure-activity relationship indicated that alpha-methylene-gamma-butyrolactone is required for the inhibitory effect. Costunolide markedly inhibited the granule exocytosis and the production of inositol phosphates in response to anti-CD3 monoclonal antibody (mAb) stimulation at a concentration that did not affect the binding of anti-CD3 mAb. Tyrosine phosphorylation induced by crosslinking of CD3 molecules was significantly inhibited by costunolide in a dose-dependent manner. These results suggest that costunolide inhibits the killing activity of CTL through preventing the increase in tyrosine phosphorylation in response to the crosslinking of T-cell receptors.

Establishment and characterization of a novel cell line, TK-6, derived from T cell blast crisis of chronic myelogenous leukemia, with the secretion of parathyroid hormone-related protein

We established a novel T cell line, designated TK-6, from a patient with T cell lineage blast crisis of chronic myelogenous leukemia (CML) complicated by hypercalcemia. A surface marker study showed T cell phenotype, cluster designation (CD)4, CD5 and CD7. Light and electron microscopic examination revealed myeloperoxidase (MPO)-negative, however, ultrastructural examination under certain specific conditions demonstrated that some cells were MPO-positive. The TK-6 cell karyotype carried a t(9;22)(q34;q11) and additional chromosome aberrations, including a deletion of the long arm of chromosome 6 and the abnormality of chromosome 7. Southern blot analysis showed rearrangement of the T cell receptor beta-chain (TCR beta) gene and the major breakpoint cluster region (bcr) gene. Northern blot analysis detected the expression of the parathyroid hormone-related protein (PTHrP) gene, however, the proviral genome of human T cell leukemia virus type I (HTLV-I) was negative. This cell line will provide a valuable resource for the analysis of the relationship between T cell lineage crisis and myeloid differentiation and for the analysis of humoral hypercalcemia of malignancy (HHM) or leukemia.

Prodigiosin 25-C perturbs permeation of acetate in a cultured cell line

Prodigiosin 25-C had little effect on DNA, RNA, and protein synthesis, and cellular ATP content, but the drug markedly inhibited the incorporation of acetate into lipid fractions. Under the same conditions, the incorporation of other lipid precursors including glycerol, mevalonate, palmitate, and oleate was not affected. A decrease in the incorporation of acetate was not due to the inhibition of fatty acid biosynthesis, because prodigiosin 25-C did not affect the activity of acetyl-CoA synthetase, acetyl-CoA carboxylase or fatty acid synthase in cell-free assay systems prepared from rat liver cytosol. In contrast, prodigiosin 25-C strongly inhibited the rapid uptake of acetate into acid-soluble fraction in intact cells. The results suggest that prodigiosin 25-C specifically perturbs the permeation of acetate through plasma membranes.

1'-Acetoxychavicol acetate as an inhibitor of phagocytosis of macrophages

We screened extracts of edible plants for inhibitors of phagocytosis by peritoneal exudate macrophages. 1'-Acetoxychavicol acetate was isolated from the ethyl acetate extract of Languas galanga, and this compound strongly inhibited phagocytosis at an IC50 value of 1.2 microM with negligible effects on pinocytosis and cell viability. Target(s) of 1'-acetoxychavicol acetate was suggested to be downstream of the signal transduction pathway that is mediated by protein kinase C.

Prodigiosin 25-C suppression of cytotoxic T cells in vitro and in vivo similar to that of concanamycin B, a specific inhibitor of vacuolar type H(+)-ATPase

The effects of prodigiosin 25-C (PrG) which preferentially suppresses cytotoxic T cells (CTL), was examined in comparison with concanamycin B (CMB), a specific inhibitor of vacuolar type H(+)-ATPase (V-ATPase). PrG and CMB directly inhibited the cytotoxic function of CTL and neutralized acidic organelles of CTL in vitro. In addition, PrG or CMB was injected in C57BL/6 mice after immunization with an allogeneic mastocytoma, P815. PrG and CMB inhibited the killing activity of CTL against the tumor and reduced the population of CD8+ cells without affecting CD4+ and B220+ populations in the spleen. PrG and CMB had only a negligible effect on antibody production induced by sheep red blood cells (SRBC) and mitogenic responses of lymphocytes. These results suggest that PrG and CMB have similar immunosuppressive properties at least through their inhibitory effects on acidification of intracellular organelles required for the effective function of CTL.

Thiol-protease inhibitors selectively inhibit presentation of antigen incorporated through B cell antigen receptors

B cells efficiently uptake exogenous antigens through cell surface IgM molecules and present them to specific T cells. Although it is implicated that antigens taken up by surface IgM associate with newly synthesized class II molecules, the precise pathway of the presentation is still unclear. Here we report that thiol-protease inhibitors inhibit the presentation of trinitrophenol-conjugated ovalbumin by a leukemic B cell line, A20.HL, which constitutively expresses trinitrophenol-specific surface IgM although they had only a minimum effect on the presentation of unconjugated ovalbumin. In addition, thiol-protease inhibitors slightly reduced the surface expression of class II molecules. Our results suggest that exogenous antigen taken up through surface IgM is presented by a pathway which involves proteolysis by thiol-proteases and distinct from that for the antigens taken up through non-specific endocytosis.