A metalloproteinase disintegrin that releases tumour-necrosis factor-alpha from cells

Mammalian cells proteolytically release (shed) the extracellular domains of many cell-surface proteins. Modification of the cell surface in this way can alter the cell's responsiveness to its environment and release potent soluble regulatory factors. The release of soluble tumour-necrosis factor-alpha (TNF-alpha) from its membrane-bound precursor is one of the most intensively studied shedding events because this inflammatory cytokine is so physiologically important. The inhibition of TNF-alpha release (and many other shedding phenomena) by hydroxamic acid-based inhibitors indicates that one or more metalloproteinases is involved. We have now purified and cloned a metalloproteinase that specifically cleaves precursor TNF-alpha. Inactivation of the gene in mouse cells caused a marked decrease in soluble TNF-alpha production. This enzyme (called the TNF-alpha-converting enzyme, or TACE) is a new member of the family of mammalian adamalysins (or ADAMs), for which no physiological catalytic function has previously been identified. Our results should facilitate the development of therapeutically useful inhibitors of TNF-alpha release, and they indicate that an important function of adamalysins may be to shed cell-surface proteins.

An essential role for ectodomain shedding in mammalian development

The ectodomains of numerous proteins are released from cells by proteolysis to yield soluble intercellular regulators. The responsible protease, tumor necrosis factor-alpha converting enzyme (TACE), has been identified only in the case when tumor necrosis factor-alpha (TNFalpha) is released. Analyses of cells lacking this metalloproteinase-disintegrin revealed an expanded role for TACE in the processing of other cell surface proteins, including a TNF receptor, the L-selectin adhesion molecule, and transforming growth factor-alpha (TGFalpha). The phenotype of mice lacking TACE suggests an essential role for soluble TGFalpha in normal development and emphasizes the importance of protein ectodomain shedding in vivo.

Functional analysis of the domain structure of tumor necrosis factor-alpha converting enzyme

Many membrane-bound proteins, including cytokines, receptors, and growth factors, are proteolytically cleaved to release a soluble form of their extracellular domain. The tumor necrosis factor (TNF)-alpha converting enzyme (TACE/ADAM-17) is a transmembrane metalloproteinase responsible for the proteolytic release or "shedding" of several cell-surface proteins, including TNF and p75 TNFR. We established a TACE-reconstitution system using TACE-deficient cells co-transfected with TACE and substrate cDNAs to study TACE function and regulation. Using the TACE-reconstitution system, we identified two additional substrates of TACE, interleukin (IL)-1R-II and p55 TNFR. Using truncations and chimeric constructs of TACE and another ADAM family member, ADAM-10, we studied the function of the different domains of TACE in three shedding activities. We found that TACE must be expressed with its membrane-anchoring domain for phorbol ester-stimulated shedding of TNF, p75 TNFR, and IL-1R-II, but that the cytoplasmic domain is not required for the shedding of these substrates. The catalytic domain of ADAM-10 could not be functionally substituted for that of TACE. IL-1R-II shedding required the cysteine-rich domain of TACE as well as the catalytic domain, whereas TNF and p75 TNFR shedding required only the tethered TACE catalytic domain.

Crystal structure of the catalytic domain of human tumor necrosis factor-alpha-converting enzyme

Tumor necrosis factor-alpha (TNFalpha) is a cytokine that induces protective inflammatory reactions and kills tumor cells but also causes severe damage when produced in excess, as in rheumatoid arthritis and septic shock. Soluble TNFalpha is released from its membrane-bound precursor by a membrane-anchored proteinase, recently identified as a multidomain metalloproteinase called TNFalpha-converting enzyme or TACE. We have cocrystallized the catalytic domain of TACE with a hydroxamic acid inhibitor and have solved its 2.0 A crystal structure. This structure reveals a polypeptide fold and a catalytic zinc environment resembling that of the snake venom metalloproteinases, identifying TACE as a member of the adamalysin/ADAM family. However, a number of large insertion loops generate unique surface features. The pro-TNFalpha cleavage site fits to the active site of TACE but seems also to be determined by its position relative to the base of the compact trimeric TNFalpha cone. The active-site cleft of TACE shares properties with the matrix metalloproteinases but exhibits unique features such as a deep S3' pocket merging with the S1' specificity pocket below the surface. The structure thus opens a different approach toward the design of specific synthetic TACE inhibitors, which could act as effective therapeutic agents in vivo to modulate TNFalpha-induced pathophysiological effects, and might also help to control related shedding processes.

Molecular analysis of the period locus in Drosophila melanogaster and identification of a transcript involved in biological rhythms

We have isolated and analyzed DNA sequences encompassing the period (per) locus of Drosophila melanogaster. The location of this clock gene was delimited by the molecular mapping of chromosome aberrations at or very near the per locus. At least five RNAs are transcribed from this region. One of these transcripts, a 0.9 kb species, is strongly implicated in per's control of biological rhythms. Two independently isolated arrhythmic mutations at the per locus dramatically reduce the level of this transcript. Furthermore, the level of the 0.9 kb transcript is strongly modulated during a light/dark cycle. We discuss evidence, from previously reported genetic and phenotypic analysis of per's function, suggesting that this region may be complex and that several gene products from the per region, including this 0.9 kb transcript, may be involved in the different aspects of normal rhythmicity influenced by this clock gene.

P-element transformation with period locus DNA restores rhythmicity to mutant, arrhythmic Drosophila melanogaster

Mutations at the period (per) locus of Drosophila melanogaster disrupt several biological rhythms. Molecular cloning of DNA sequences encompassing the per+ locus has allowed germ-line transformation experiments to be carried out. Certain subsegments of the per region, transduced into the genome of arrhythmic pero flies, restore rhythmicity in circadian locomotor behavior and the male's courtship song.

Purification and characterization of a bovine acetyl low density lipoprotein receptor

The acetyl low density lipoprotein (LDL) receptor is expressed on macrophages and some endothelial cells and mediates macrophage-foam cell formation in culture. A 220-kDa acetyl LDL binding protein was partially purified from bovine liver membranes and was used to make a specific monoclonal antibody. The 220-kDa protein immunoprecipitated by this antibody retained binding activity, and the antibody was used to detect this protein in cells lining bovine liver sinusoids and on the surface of cultured bovine alveolar macrophages. In the human monocytic cell line THP-1, the expression of both acetyl LDL receptor activity and a 220-kDa acetyl LDL binding protein were dramatically induced in parallel after differentiation to a macrophage-like state induced by phorbol ester. The ligand specificity, tissue and cell-type specificity, and coinduction data indicated that this 220-kDa cell-surface binding protein is probably a receptor that mediates acetyl LDL endocytosis. The 220-kDa protein, which was purified 238,000-fold from bovine lung membranes to near homogeneity using monoclonal antibody affinity chromatography, is a trimer of 77-kDa subunits that contain asparagine-linked carbohydrate chains.

cJun overexpression in MCF-7 breast cancer cells produces a tumorigenic, invasive and hormone resistant phenotype

We have previously demonstrated decreased Jun/AP-1 activity in the breast cancer cell line MCF-7 when compared to normal or immortalized mammary epithelial cells. In this paper, we overexpress Jun in MCF-7 cells (MCF7Jun) and demonstrate that it results in diverse biologic and biochemical changes, which mimic those seen clinically in breast cancer. Overexpression of Jun causes significant alterations in the composition of AP-1, decreased junB and increased fra-1 expression and results in an increased biologic aggressiveness. MCF7Jun cells exhibit increased cellular motility, increased expression of a matrix degrading enzyme MMP-9, increased in vitro chemoinvasion and tumor formation in nude mice in the absence of exogenous estrogens. Furthermore, MCF7Jun cells are unresponsive to the growth stimulating effects of estrogen and growth inhibitory effects of tamoxifen. Analysis of the estrogen receptor (ER) expression and activity showed that the MCF7Jun cells have no detectable ER. MCF-7 cells overexpressing mutant forms of cJun were responsive to the growth stimulatory effects of estrogen indicating that full-length cJun is required to acquire the estrogen-independent phenotype in breast cancer cells.

Screening for extended-spectrum beta-lactamase-producing Enterobacteriaceae among high-risk patients and rates of subsequent bacteremia

BACKGROUND

Bloodstream infections due to extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae have been associated with increased hospital costs, length of stay, and patient mortality. However, the role of routine inpatient surveillance for ESBL colonization in predicting related infection is unclear.

METHODS

From 2000 through 2005, we screened 17,872 patients hospitalized in designated high-risk units for rectal colonization with vancomycin-resistant enterococci and ESBL-producing Enterobacteriaceae using a selective culture medium. In patients with a bloodstream infection due to ESBL-producing Enterobacteriaceae (ESBL-BI) during the study period, surveillance results were evaluated for evidence of antecedent ESBL-producing Enterobacteriaceae colonization.

RESULTS

The rate of ESBL-producing Enterobacteriaceae colonization doubled during the 6-year study period, increasing from 1.33% of high-risk patients in 2000 to 3.21% in 2005. Among patients with ESBL-producing Enterobacteriaceae colonization, 49.6% also carried vancomycin-resistant enterococci. The number of ESBL-BIs increased >4-fold in 5 years, from 9 cases in 2001 to 40 cases in 2005. Of 413 patients colonized with ESBL-producing Enterobacteriaceae, 35 (8.5%) developed a subsequent ESBL-BI. Of concern, more than one-half of all ESBL-BIs occurred in patients who were not screened. These 56 patients received a diagnosis of ESBL-BI in the emergency department, when hospitalized in low-risk medical units, or at transfer from an acute or long-term health care facility.

CONCLUSIONS

Colonization with ESBL-producing Enterobacteriaceae is increasing at a rapid rate, and routine rectal surveillance for ESBL-producing Enterobacteriaceae may have clinical implications. However, in our experience, over one-half of patients with an ESBL-BI did not undergo screening through our current surveillance measures. As a result, targeted screening for ESBL-producing Enterobacteriaceae among additional patient populations may be integral to future ESBL-BI prevention and management efforts.

Oral amiodarone for prevention of atrial fibrillation after open heart surgery, the Atrial Fibrillation Suppression Trial (AFIST): a randomised placebo-controlled trial

BACKGROUND

Beta-blockers and amiodarone reduce the frequency of atrial fibrillation after open-heart surgery but the effectiveness of oral amiodarone in older patients already receiving beta-blockers is unknown. We have assessed the efficacy of oral amiodarone in preventing atrial fibrillation in patients aged 60 years or older undergoing open-heart surgery.

METHODS

We did a randomised, double-blind placebo-controlled trial in which patients undergoing open-heart surgery (n=220, average age 73 years) received amiodarone (n=120) or placebo (n=100). Patients enrolled less than 5 days before surgery received 6 g of amiodarone or placebo over 6 days beginning on preoperative day 1. Patients enrolled at least 5 days before surgery received 7 g over 10 days beginning on preoperative day 5.

FINDINGS

Patients on amiodarone had a lower frequency of any atrial fibrillation (22.5% vs 38.0%; p=0.01; absolute difference 15.5% [95% CI 3.4-27.6%]), and there were significant differences in favour of the active drug for symptomatic atrial fibrillation (4.2% vs 18.0%, p=0.001), cerebrovascular accident (1.7% vs 7.0%, p=0.04), and postoperative ventricular tachycardia (1.7% vs 7.0%, p=0.04). Beta-blocker use (87.5% amiodarone vs 91.0% placebo), nausea (26.7% vs 16.0%), 30-day mortality (3.3% vs 4.0%), symptomatic bradycardia (7.5% vs 7.0%), and hypotension (14.2% vs 10.0%) were similar.

INTERPRETATION

Oral amiodarone prophylaxis in combination with beta-blockers prevents atrial fibrillation and symptomatic fibrillation and reduces the risk of cerebrovascular accidents and ventricular tachycardia.

Oxidative stress and AP-1 activity in tamoxifen-resistant breast tumors in vivo

BACKGROUND

Most breast cancers, even those that are initially responsive to tamoxifen, ultimately become resistant. The molecular basis for this resistance, which in some patients is thought to involve stimulation of tumor growth by tamoxifen, is unclear. Tamoxifen induces cellular oxidative stress, and because changes in cell redox state can activate signaling pathways leading to the activation of activating protein-1 (AP-1), we investigated whether tamoxifen-resistant growth in vivo is associated with oxidative stress and/or activation of AP-1 in a xenograft model system where resistance is caused by tamoxifen-stimulated growth.

METHODS

Control estrogen-treated, tamoxifen-sensitive, and tamoxifen-resistant MCF-7 xenograft tumors were assessed for oxidative stress by measuring levels of antioxidant enzyme (e.g., superoxide dismutase [SOD], glutathione S-transferase [GST], and hexose monophosphate shunt [HMS]) activity, glutathione, and lipid peroxidation. AP-1 protein levels, phosphorylated c-jun levels, and phosphorylated Jun NH(2)-terminal kinase (JNK) levels were examined by western blot analyses, and AP-1 DNA-binding and transcriptional activities were assessed by electrophoretic mobility shift assays and a reporter gene system. All statistical tests are two-sided.

RESULTS

Compared with control estrogen-treated tumors, tamoxifen resistant tumors had statistically significantly increased SOD (more than threefold; P=.004) and GST (twofold; P=.004) activity and statistically significantly reduced glutathione levels (greater than twofold; P<.001) and HMS activity (10-fold; P<.001). Lipid peroxides were not significantly different between control and tamoxifen-resistant tumors. We observed no differences in AP-1 protein components or DNA-binding activity. However, AP-1-dependent transcription (P=.04) and phosphorylated c-Jun and JNK levels (P<.001) were statistically significantly increased in the tamoxifen-resistant tumors.

CONCLUSION

Our results suggest that the conversion of breast tumors to a tamoxifen-resistant phenotype is associated with oxidative stress and the subsequent antioxidant response and with increased phosphorylated JNK and c-Jun levels and AP-1 activity, which together could contribute to tumor growth.

Germ-line transformation involving DNA from the period locus in Drosophila melanogaster: overlapping genomic fragments that restore circadian and ultradian rhythmicity to per0 and per- mutants

P-element-mediated transformations involving DNA fragments from the period (per) clock gene of Drosophila melanogaster have shown that several subsegments of the locus restore rhythmicity to per0 or per- mutants. Such fragments overlap in a genomic region complementary to one transcript, a 4.5-kb RNA which is probably the per message, in that it is necessary and (in terms of expression from this X-chromosomal locus) sufficient for the fly's circadian rhythms. It is also at least necessary for the high-frequency oscillations normally produced by courting males as they vibrate their wings. The entirety of the 4.5-kb transcript is not necessary for rather strong rhythmicity; nor does it seem to be sufficient, in transformants, for wild-type behavioral phenotypes. A 0.9-kb RNA, homologous to genomic region immediately adjacent to the source of the 4.5-kb species, oscillates in its abundance over the course of a day; but coverage of this transcript source in several transformants carrying a per0 mutation--which eliminates the 0.9-kb RNA's oscillation--does not restore rhythmicity. All of the independently isolated arrhythmic mutations tested were covered by the same array of overlapping per+-derived DNA fragments, implying that the only portion of the locus which has mutated to arrhythmicity is complementary to the 4.5-kb transcript.

Interleukin-18 regulates acute graft-versus-host disease by enhancing Fas-mediated donor T cell apoptosis

Interleukin (IL)-18 is a recently discovered cytokine that modulates both T helper type 1 (Th1) and Th2 responses. IL-18 is elevated during acute graft-versus-host disease (GVHD). We investigated the role of IL-18 in this disorder using a well characterized murine bone marrow transplantation (BMT) model (B6 --> B6D2F1). Surprisingly, blockade of IL-18 accelerated acute GVHD-related mortality. In contrast, administration of IL-18 reduced serum tumor necrosis factor (TNF)-alpha and lipopolysaccharide (LPS) levels, decreased intestinal histopathology, and resulted in significantly improved survival (75 vs. 15%, P < 0.001). Administration of IL-18 attenuated early donor T cell expansion and was associated with increased Fas expression and greater apoptosis of donor T cells. The administration of IL-18 no longer protected BMT recipients from GVHD when Fas deficient (lpr) mice were used as donors. IL-18 also lost its ability to protect against acute GVHD when interferon (IFN)-gamma knockout mice were used as donors. Together, these results demonstrate that IL-18 regulates acute GVHD by inducing enhanced Fas-mediated apoptosis of donor T cells early after BMT, and donor IFN-gamma is critical for this protective effect.

The second BRCT domain of BRCA1 proteins interacts with p53 and stimulates transcription from the p21WAF1/CIP1 promoter

Inherited mutations in the breast and ovarian cancer susceptibility gene BRCA1 are associated with high risk for developing breast and ovarian cancers. Several studies link BRCA1 to transcriptional regulation, DNA repair, apoptosis and growth/tumor suppression. BRCA1 associates with p53 and stimulates transcription in both p53 dependent and p53-independent manners. BRCA1 splice variants BRCA1a (p110) and BRCA1b (p100) associates with CBP/p300 co-activators. Here we show that BRCA1a and BRCA1b proteins stimulate p53-dependent transcription from the p21WAF1/CIP1 promoter. In addition, the C-terminal second BRCA1 (BRCT) domain is sufficient for p53 mediated transactivation of the p21 promoter. Previous studies emphasized the importance of the BRCT domain, which shows homology with p53 binding protein (53BP1), in transcriptional activation, growth inhibition and tumor suppression. Our findings demonstrate an additional function for this domain in protein-protein interaction and co-activation of p53. We also found that BRCA1a and BRCA1b proteins interact with p53 in vitro and in vivo. The p53 interaction domain of BRCA1a/1b maps, in vitro, to the second BRCT domain (aa 1760-1863). The BRCT domain binds to the central domain of p53 which is required for sequence specific DNA binding. These results demonstrate for the first time the presence of a second p53 interaction domain in BRCA1 proteins and suggests that BRCA1a and BRCA1b proteins, like BRCA1, function as p53 co-activators. This BRCT domain also binds in vitro to CBP. These results suggest that one of the mechanisms by which BRCA1 proteins function is through recruitment of CBP/p300 associated HAT/FAT activity for acetylation of p53 to specific promoters resulting in transcriptional activation.

Universal DNA methylation age across mammalian tissues

Aging, often considered a result of random cellular damage, can be accurately estimated using DNA methylation profiles, the foundation of pan-tissue epigenetic clocks. Here, we demonstrate the development of universal pan-mammalian clocks, using 11,754 methylation arrays from our Mammalian Methylation Consortium, which encompass 59 tissue types across 185 mammalian species. These predictive models estimate mammalian tissue age with high accuracy (r > 0.96). Age deviations correlate with human mortality risk, mouse somatotropic axis mutations and caloric restriction. We identified specific cytosines with methylation levels that change with age across numerous species. These sites, highly enriched in polycomb repressive complex 2-binding locations, are near genes implicated in mammalian development, cancer, obesity and longevity. Our findings offer new evidence suggesting that aging is evolutionarily conserved and intertwined with developmental processes across all mammals.

Shedding of interleukin-6 receptor and tumor necrosis factor alpha. Contribution of the stalk sequence to the cleavage pattern of transmembrane proteins

A functionally and structurally diverse group of transmembrane proteins including transmembrane forms of mediators or receptors can be proteolytically cleaved to form soluble growth factors or receptors. Recently, the proteolytic activity responsible for pro-tumor necrosis factor alpha (proTNFalpha) processing has been identified and named TACE (TNFalpha converting enzyme). In experiments with TACE deficient (TACE-/-) fibroblasts we found that 4beta-phorbol 12-myristate 13-acetate (PMA)-induced shedding of the interleukin-6 receptor (IL-6R) is strongly reduced. A basal hydroxamate sensitive release of IL-6R, however, could still be detected. This result demonstrates that TACE plays a role in IL-6R processing and that additional metalloproteases might be involved. PMA-induced shedding of IL-6R in TACE deficient mouse fibroblasts could be restored by stable transfection of a TACE cDNA. To characterize differences between shedding of IL-6R and proTNFalpha we generated chimeric IL-6R and proTNFalpha proteins wherein the endogenous cleavage sites (CS) had been replaced by the corresponding region of proTNFalpha and IL-6R, respectively. Interestingly, proTNFalpha chimeric proteins showed only minimal shedding. In contrast, IL-6R chimeras containing the proTNFalpha CS were shed spontaneously, processing was not further induced by PMA. Thus, the cleavage pattern transferred by the introduction of the proTNFalpha CS is similar to that of proTNFalpha itself. We conclude that the amino-acid sequence at the proteolytic CS contributes to the cleavage characteristics of a protein. However, this information alone is not sufficient to transfer cleavability as seen with proTNFalpha chimeras containing the IL-6R CS and which were resistant to shedding.

Dominant negative mutations in yeast TFIID define a bipartite DNA-binding region

Genetic analysis showed that the conserved C-terminal 180 amino acids of yeast TFIID contain all the essential functions for growth of yeast and response to acidic transcriptional activation signals. A genetic screen was used to identify functionally important residues within this C-terminal region. Five dominant TFIID mutations were isolated that had lost the ability to bind DNA. Four of these mutations were single amino acid substitutions in the most N-terminal of two 66-67 amino acid repeats in TFIID. Analogous mutations made in the most C-terminal repeat all failed to bind DNA and inhibited growth of cells, suggesting that the DNA-binding function of TFIID is partitioned between the two repeated regions. Overproduction of wild-type TFIID rescued the dominance of the TFIID mutants, suggesting that the mutant proteins are dominant because they compete with wild-type TFIID for binding to one or more essential transcription factors.

The period clock locus of D. melanogaster codes for a proteoglycan

The period (per) gene of D. melanogaster is involved in the generation of biological rhythms. The most striking feature of the predicted coding sequence, corresponding to the key 4.5 kb transcript from this locus, is an extensive run of alternating Gly-Thr residues. This is homologous to a series of Gly-Ser repeats in a chondroitin sulfate proteoglycan. To determine whether the per transcript codes for a proteoglycan, a region of its coding sequence was expressed (in bacteria) as part of a fusion protein, which was used to immunize rabbits. When the resultant immune sera were used to probe fly protein preparations, they detected an antigen that is present in wild-type flies and absent in a per- mutant. Biochemical characterization of this antigen indicated that it is indeed a proteoglycan.

Translational efficiency of the Escherichia coli adenylate cyclase gene: mutating the UUG initiation codon to GUG or AUG results in increased gene expression

Roy et al. [Roy, A., Haziza, C. & Danchin, A. (1983) EMBO J. 2, 791-797] established that translation of Escherichia coli adenylate cyclase initiates at a UUG codon, and they suggested this might decrease the efficiency of translation. We investigated the effect of varying the initiation codon on the expression of the adenylate cyclase (cya) gene. Using oligonucleotide-directed mutagenesis, we changed the UUG initiation codon to GUG and the more common initiator AUG and assayed for cya gene expression in a number of ways. First, the GUG initiation codon, in place of UUG, doubled cya expression when cya was expressed from the dual cya P1/P2 promoters. The corresponding AUG codon construct was nonviable. Second, when the cya gene was placed under the transcriptional control of the thermoinducible phage lambda PL promoter, the relative amounts of cya gene product were 1:2:6 for the UUG, GUG, and AUG initiation codons, respectively. Finally, the cya P2 promoter, Shine-Dalgarno sequence, and the DNA corresponding to the first 86 codons of cya were fused to DNA encoding the E. coli galactokinase gene beginning at the second codon. The relative amounts of the fusion polypeptides, which had galactokinase activity, were 1:2:3 for the UUG, GUG, and AUG initiation codons, respectively. These results demonstrate that the cya UUG initiation codon limits cya expression at the level of translation.

Mechanistic and physiological consequences of HPr(ser) phosphorylation on the activities of the phosphoenolpyruvate:sugar phosphotransferase system in gram-positive bacteria: studies with site-specific mutants of HPr

The bacterial phosphotransferase system (PTS) catalyzes the transport and phosphorylation of its sugar substrates. The protein-kinase-catalyzed phosphorylation of serine 46 in the phosphocarrier protein, HPr, inhibits PTS activity, but neither the mechanism of this inhibition nor its physiological significance is known. Site-specific HPr mutants were constructed in which serine 46 was replaced by alanine (S46A), threonine (S46T), tyrosine (S46Y) or aspartate (S46D). The purified S46D protein exhibited markedly lower Vmax and higher Km values than the wild-type, S46T or S46A protein for the phosphoryl transfer reactions involving HPr(His approximately P). Interactions of HPr with the enzymes catalyzing phosphoryl transfer to and from HPr regulated the kinase-catalyzed reaction. These results establish the inhibitory effect of a negative charge at position 46 on PTS-mediated phosphoryl transfer and suggest that HPr is phosphorylated on both histidyl and seryl residues by enzymes that recognize its tertiary rather than its primary structure. In vivo studies showed that a negative charge on residue 46 of HPr strongly inhibits PTS-mediated sugar uptake, but that competition of two PTS permeases for HPr(His approximately P) is quantitatively more important to the regulation of PTS function than serine 46 phosphorylation.

Sham versus transurethral microwave thermotherapy in patients with symptoms of benign prostatic bladder outflow obstruction

Transurethral microwave thermotherapy (TUMT) is a single-session, minimally invasive outpatient treatment for patients with symptoms of benign prostatic bladder outflow obstruction. We designed a prospective randomised trial to identify any placebo response. Patients with a Madsen symptom score over 8 for at least 6 months were eligible for study. Two measurements of urinary flow less than 15 mL/s and a residual urine of under 350 mL were also required for entry. Patients with renal dysfunction, upper urinary tract disease, co-existing bladder disease, and malignant prostatic change were excluded. 43 patients were studied: 21 were randomised to receive a sham treatment and 22 to thermotherapy. Sham treatments were done with the urethral applicator in situ. 40 patients were available for evaluation at 3 months. 2 patients had delayed follow-up and 1 patient randomised to TUMT has undergone transurethral resection. The thermotherapy group showed a 70% decrease (from 14.5 to 4.3) in the mean Madsen score, a 53% increase in flow-rate (8.5 to 13.0 mL/s), and 92% decrease in residual urine volume (147 to 12 mL). No significant change was seen in these mean indices in the sham group. There was no difference in the main complication of transient haematuria between the two groups. However, there was a 22% frequency of acute retention in the TUMT group. The results show little significant placebo component to the subjective and objective improvement that occurs in patients who have received TUMT.

A critical evaluation of resting intracellular free calcium regulation in dystrophic mdx muscle

There are conflicting reports regarding whether resting free calcium levels ([Ca2+]i) are elevated in dystrophic mouse (mdx) myotubes and adult myofibers. We reinvestigated this question and found several lines of evidence supporting the hypothesis that increased calcium influx via leak channels leads to increases in resting [Ca2+]i. 1) Step calibration of fura 2/free acid in myofibers with use of microinjected Ca(2+)-ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid buffers revealed greater [Ca2+]i in dystrophic cells. Careful calibration of fura PE3-AM, a compartmentalization-resistant derivative of fura 2, also showed elevated [Ca2+]i in mdx myotubes. 2) Chronic, but not acute, application of tetrodotoxin reduced resting [Ca2+]i in dystrophic myotubes, suggesting that elevated resting [Ca2+]i is a consequence of previous long-term contractile activity. 3) Rates of manganese quenching of fura 2 fluorescence, an indirect indicator of calcium influx, were significantly higher in mdx myotubes and were increased by nifedipine, a calcium leak channel agonist. 4) Calcium leak channel activity, measured using patch clamping, was greater in the sarcolemma of adult non-enzyme-treated mdx myofibers.

A capacitative calcium current in cultured skeletal muscle cells is mediated by the calcium-specific leak channel and inhibited by dihydropyridine compounds

Calcium stores from cultured skeletal muscle cells were depleted using cyclopiazonic acid (CPA), a reversible inhibitor of Ca2+-ATPases at the sarcoplasmic reticulum. Store depletion led to activation of the calcium-specific leak channel, as assayed using single-channel patch clamp analysis and rates of manganese influx and quenching of fura-2 fluorescence. Two novel dihydropyridine compounds inhibited this single-channel leak channel activity, the resting and depletion-induced manganese influx, and refilling of the CPA-depleted intracellular calcium store. These compounds represent the first antagonists for a calcium leak channel and for a channel that mediates a capacitative current. The development of the skeletal muscle capacitative current was inhibited by genistein, a tyrosine kinase inhibitor, but was not affected by okadaic acid, a phosphatase inhibitor, or econazole. Thus, the capacitative current in cultured skeletal muscle cells was mediated by the calcium leak channel and was inhibited by pharmacological antagonists and may provide a model system for uncovering the complete set of signals leading from store depletion to channel activation.