Premature transcription termination at the expanded GAA repeats and aberrant alternative polyadenylation contributes to the Frataxin transcriptional deficit in Friedreich's ataxia

Frataxin deficiency in Friedreich's ataxia results from transcriptional downregulation of the FXN gene caused by expansion of the intronic trinucleotide guanine-adenine-adenine (GAA) repeats. We used multiple transcriptomic approaches to determine the molecular mechanism of transcription inhibition caused by long GAAs. We uncovered that transcription of FXN in patient cells is prematurely terminated upstream of the expanded repeats leading to the formation of a novel, truncated and stable RNA. This FXN early terminated transcript (FXN-ett) undergoes alternative, non-productive splicing and does not contribute to the synthesis of functional frataxin. The level the FXN-ett RNA directly correlates with the length of the longer of the two expanded GAA tracts. Targeting GAAs with antisense oligonucleotides or excision of the repeats eliminates the transcription impediment, diminishes expression of the aberrant FXN-ett, while increasing levels of FXN mRNA and frataxin. Non-productive transcription may represent a common phenomenon and attractive therapeutic target in diseases caused by repeat-mediated transcription aberrations.

559 IDENTIFYING PATIENTS WITH MOOD DISORDER FOLLOWING ADMISSION WITH HIP FRACTURE WITH A VIEW TO STARTING TREATMENT & PROVIDE ADVICE

Introduction

The signs of depression in the elderly often go unnoticed. The MDT at RSCH observed that low mood could negatively impact on patient’s recovery, affecting pain thresholds and leading to poor engagement with rehabilitation. Proactive identification and management of mood disorder is an important part of CGA, but not routinely performed. The aim of this QI project is to improve identification and management of mood disorder in patients over 65 years admitted to RSCH with hip fractures by introducing a standardised assessment tool to guide appropriate interventions.

Method

Notes of patients with hip fracture admitted over a four-month period were retrospectively reviewed to establish if patients were screened for low mood. A mood screening tool, Cornell Score, was chosen and implemented by OT’s and junior doctors over a four-month period. Those identified with depression or probable depression were issued verbal advice, an information leaflet and follow-up arranged.

Results

Ninety-eight patients were included in the retrospective cohort; There was no indication that mood was considered or assessed at any point during admission. During the four-month prospective period, 86 patients (96%) were screened for low mood; 9% had major depression and 16% probable depression. Feedback from our occupational therapists and doctors was positive, with the tool being easy to use in patients with or without cognitive impairment. Much of the assessment could be incorporated into initial assessment or in gaining collateral history. Anecdotally, considering patients psychological well-being had a positive impact on inpatient therapy sessions guided the MDT in supporting the patient appropriately.

Conclusion

Implementation of a standardised and validated mood screening tool enabled us to identify that a quarter (25%) of the patients had, or probably had depression. This allowed us to intervene with simple measures such as verbal advice and an information leaflet and consider pharmacological intervention where appropriate.

Shortage of paediatric radiologists acting as an expert witness: position statement from the British Society of Paediatric Radiology (BSPR) National Working Group on Imaging in Suspected Physical Abuse (SPA)

One of the most challenging areas of radiological imaging in children is the diagnosis of physical abuse. There is a dearth of paediatric radiologists willing to act as expert witnesses, particularly in the family courts. There are a number of reasons why radiologists may not be interested or willing to put themselves forward to work as expert witnesses in this field. A group of imaging experts recently formed the "British Society of Paediatric Radiology (BSPR) Working Group on Imaging in Suspected Physical Abuse (SPA)". The group comprises radiologists and neuroradiologists with current or previous experience of providing expert witness reports to the court in cases of SPA. The group met in January 2019 to explore pragmatic solutions to the chronic inefficiencies in both medical and legal practices and the challenges that arise from working in a legal arena with different structures, goals, and assessment criteria. Key issues concerned organisational inefficiencies, variable support from National Health Service Trusts and the Royal College of Radiologists to conduct this work, and the risk/benefit of involvement. This work is important for the patient, parents, and society in general, and highly rewarding for clinical practitioners who are involved, but there are several issues with current practices that discourage active participation. With several members of the group either retired or close to retirement, the shortage of experts is becoming a pressing issue within the UK, which requires an engaged multidisciplinary group to come up with creative solutions. Here, the group provide a consensus opinion highlighting the current barriers and potential facilitators to increasing the number of radiologists willing to provide opinions to the court.

Hijacking a key chromatin modulator creates epigenetic vulnerability for MYC-driven cancer

While the genomic binding of MYC protein correlates with active epigenetic marks on chromatin, it remains largely unclear how major epigenetic mechanisms functionally impact the tumorigenic potential of MYC. Here, we show that, compared with the catalytic subunits, the core subunits, including DPY30, of the major H3K4 methyltransferase complexes were frequently amplified in human cancers and selectively upregulated in Burkitt lymphoma. We show that DPY30 promoted the expression of endogenous MYC and was also functionally important for efficient binding of MYC to its genomic targets by regulating chromatin accessibility. Dpy30 heterozygosity did not affect normal animal physiology including lifespan, but significantly suppressed Myc-driven lymphomagenesis, as cells failed to combat oncogene-triggered apoptosis as a result of insufficient epigenetic modulation and expression of a subset of antiapoptotic genes. Dpy30 reduction also greatly impeded MYC-dependent cellular transformation, without affecting normal cell growth. These results suggest that MYC hijacks a major epigenetic pathway - H3K4 methylation - to facilitate its molecular activity in target binding and to coordinate its oncogenic program for efficient tumorigenesis, meanwhile creating "epigenetic vulnerability." DPY30 and the H3K4 methylation pathway are thus potential epigenetic targets for treating certain MYC-driven cancers.

Factors associated with reduced FEV1 in adult patients with cystic fibrosis in a relatively affluent area

Data collected on adult cystic fibrosis (CF) patients and entered onto the CF database in the south and west regions of England were analysed for the year 2001. FEV1 was taken as a marker of lung disease severity. Data on 371 patients (158 female) mean age 24.7 years (range 16.0-48.9) were assessed. FEV1 was reduced in CF patients infected with Pseudomonas aeruginosa (Pa) (mean 62.6% predicted) compared with those without (mean FEV1 77.8%, P < 0.00001). The reduction was noted irrespective of age group. FEV1 progressively reduced with the increasing need for high-intensity treatment (P < 0.00001) and with the diagnosis of diabetes mellitus (P = 0.03). FEV, correlated with body mass index (BMI) (r = + 0.42, P < 0.0001). Genetic profile and poverty and deprivation score did not affect the value of FEV1. Chronic infection with Pa mainly in young adults, treatment intensity, diabetes mellitus and reduced body mass index are associated with reduced FEV, in adult patients with cystic fibrosis in the south and west regions of England. In this relatively affluent area, scores of poverty and deprivation were not associated with the decline in lung function tests.

Abstract 2164: Revisiting the mechanisms of PTEN loss in melanoma

Introduction

Inactivation of the PTEN tumor suppressor, a negative regulator of oncogenic PI3K/Akt signaling, occurs in a subset of melanomas and is correlated with disease progression, treatment resistance and reduced patient survival. PTEN loss of function in melanoma is thought to result largely from gene deletion, mutation and/or methylation. However, the low frequency of these genomic alterations cannot explain the higher rate of loss of PTEN protein expression that is observed in melanoma. In this study, we tested the hypothesis that loss of PTEN expression in melanoma might be the consequence of predominantly non-genomic mechanisms, including post-transcriptional and post-translational dysregulation. Specifically, we postulated that PTEN loss in some melanomas might result from aberrant expression of PTENP1, a PTEN pseudogene-derived long non-coding RNA, and from increased PTEN ubiquitination and hence protein degradation.

Experimental Procedures

We performed an integrated analysis of data obtained from The Cancer Genome Atlas (TCGA; n = 276) and metastatic melanoma human specimens from patients enrolled at NYU (n = 48). We examined the frequency of PTEN copy number loss using genomic qPCR, PTEN mutations using targeted sequencing and qPCR mutation arrays, and PTEN methylation status was determined in tumors lacking PTEN deletion or mutation with bisulfite treatment and pyrosequencing. Furthermore, we assessed PTEN and PTENP1 expression in tumor samples by RT-qPCR, western blotting and immunohistochemistry.

Results

Complete PTEN deletions were found in 8% of TCGA cases and in 10% of NYU cases, while partial PTEN deletions were detected in 27% of NYU cases. Somatic PTEN mutations were found in 8% of TCGA cases and 3% of NYU cases. The frequency of PTEN methylation at five CpG islands ranged between 0% and 28% and did not predict PTEN protein expression, thus identifying a subset of tumors that exhibit PTEN protein loss despite a lack of detectable PTEN deletions, mutations or methylation. Integration of PTEN and PTENP1 expression data from TCGA and the NYU cohort revealed a strong positive correlation between PTEN and PTENP1 levels in melanoma. Analysis of a role for aberrant PTEN ubiquitination in promoting PTEN loss in melanoma is ongoing.

Conclusions

Our data challenge the existing model in which PTEN loss in melanoma is thought to occur primarily as a result of gene deletion, mutation or methylation. Rather, we find that these are uncommon events in melanoma and that PTEN loss may instead be attributed to post-transcriptional or post-translational mechanisms, such as dysregulation by loss of the PTENP1 long non-coding RNA. A comprehensive understanding of these non-genomic processes could identify novel approaches (“PTEN-restoring therapy”) to block tumor progression and improve treatment responses and patient survival, suggesting that suppression of PTEN levels in melanoma might be reversible and thus could be exploited clinically.

Citation Format: Keith Giles, Yang Li, Amel Salhi, Jinhua Wang, Eric Robinson, Iman Osman. Revisiting the mechanisms of PTEN loss in melanoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2164. doi:10.1158/1538-7445.AM2015-2164

Chromatin domains, insulators, and the regulation of gene expression

The DNA sequence elements called insulators have two basic kinds of properties. Barrier elements block the propagation of heterochromatic structures into adjacent euchromatin. Enhancer blocking elements interfere with interaction between an enhancer and promoter when placed between them. We have dissected a compound insulator element found at the 5' end of the chicken β-globin locus, which possesses both activities. Barrier insulation is mediated by two kinds of DNA binding proteins: USF1/USF2, a heterodimer which recruits multiple enzyme complexes capable of marking histone on adjacent nucleosomes with 'activating' marks, and Vezf1, which protects against DNA methylation. We have found that the heterochromatic region upstream of the insulator element is maintained in its silent state by a dicer-dependent mechanism, suggesting a mechanism for Vezf1 function in the insulator. Enhancer blocking function in the β-globin insulator element is conferred by a binding site for CTCF. Consistent with this property, CTCF binding was found some years ago to be essential for imprinted expression at the Igf2/H19 locus. Work in many laboratories has since demonstrated that CTCF helps stabilize long-range interactions in the nucleus. We have recently shown that in the case of the human insulin locus such an interaction, over a distance of ~300kb, can result in stimulation of a target gene which itself is important for insulin secretion. This article is part of a Special Issue entitled: Chromatin in time and space.

miR-124a is frequently down-regulated in glioblastoma and is involved in migration and invasion

Glioblastoma (GBM) represents a formidable clinical challenge for both patients and treating physicians. Due to better local treatments and prolonged patient survival, remote recurrences are increasingly observed, underpinning the importance of targeting tumour migration and attachment. Aberrant expression of microRNA (miRNA) is commonly associated with cancer and loss of miR-124a has previously been implicated to function as a tumour suppressor. The assessment of miR-124a in clinical specimens has been limited and a potential role in migration and invasion has been unexplored until now. We measured the expression levels of mature miR-124a in a retrospective series of 119 cases of histologically confirmed GBM and found its expression was markedly lower in over 80% of the GBM clinical specimens compared to normal brain tissue. The level of reduction in the clinical cohort varied significantly and patients with lower than the average miR-124a expression levels displayed shorter survival times. Endogenous miR-124a expression and the protein expression of three of its targets; IQ motif containing GTPase activating protein 1 (IQGAP1), laminin γ1 (LAMC1) and integrin β1 (ITGB1) were significantly reciprocally associated in the majority of the clinical cases. We confirmed this association in our in vitro model. Functionally, the ectopic expression of mature miR-124a in a GBM cell line resulted in significant inhibition of migration and invasion, demonstrating a role for miR-124a in promoting tumour invasiveness. Our results suggest that miR-124a may play a role in GBM migration, and that targeted delivery of miR-124a may be a novel inhibitor of GBM invasion.

Risk factors for increased need for intravenous antibiotics for pulmonary exacerbations in adult patients with cystic fibrosis

BACKGROUND

Pulmonary exacerbations (P Exs) are important in cystic fibrosis (CF). They are very common, and are associated with poor quality of life. P Exs are regarded as an important end point in clinical trials. Risk factors associated with increase in P Exs have not been examined at a large scale. This study investigates factors associated with P Exs in a large cohort of adolescent and adult patients.

PATIENTS AND METHODS

This is a cross-sectional study on data collected in the South and West Regions in England in 2002. Patients aged 16 years and over were included. Data on age, gender, FEV(1), body mass index (BMI), infection with Pseudomonas aeruginosa (Pa) and on CF-related diabetes were included in the analysis. P Ex was defined as an episode treated with IV antibiotics. Forward stepwise multiple regression analysis was performed with the number of P Exs being the independent variable. The rest of the variables were considered to be the dependent variables.

RESULTS

Data from 341 patients (194 female), mean age (SD), 24.9 (8.9) years were available. In 2002, a total of 599 P Exs were reported, median 1.00 range 0-16 P Exs. Using stepwise multiple regression analysis factors associated with increased number of P Exs were: infection with Pa (t-value -5.0, P < 0.0001), FEV(1), (t-value -4.9, P < 0.0001) and diabetes mellitus, (t-value -2.1, P = 0.04). Age, gender and BMI did not influence the annual number of exacerbations.

CONCLUSIONS

In this study, risk factors for P Exs were found to be as follows: growth of Pa in the sputum, reduced FEV1 and CF-related diabetes mellitus.

The Transplantation Society--new key opinion leaders of tomorrow 2006

One of the new initiatives taken by the immediate past president of The Transplantation Society, KJ Wood, is to introduce a new series of meetings named 'New Key Opinion Leaders of Tomorrow'. The Transplantation Society invites the leading young investigators in the field of transplantation to participate in this meeting together with the present leaders of the field. The key objective of this meeting is to identify the potential key opinion leaders of tomorrow. Each presentation during the meeting was jointly given by the senior and junior investigators. The meeting in Buenos Aires covered six main topics on clinical, translational and basic transplantation. These included: innate immunity and inflammation; transplant infectious diseases; tumour and transplantation; medical and ethical aspects of transplantation; dendritic cells (stimulating and manipulating the immune response to a transplant); and ABO incompatible donor recipient pairs. This report focuses on the emerging biological therapeutics and their ramifications on clinical transplantation.

Differential effects of very high doses of doxercalciferol and paricalcitol on serum phosphorus in hemodialysis patients

BACKGROUND

Treatment of secondary hyperparathyroidism (SHPT) includes use of calcitriol (1,25D(3)) to suppress parathyroid hormone (PTH), but dosing of 1,25D(3) is limited by the development of hypercalcemia and a high calcium x phosphorus (Ca x P) product due to gut absorption of calcium and phosphorus as well as enhanced bone resorption. The vitamin D analog 19-Nor-1,25(OH)2-vitamin D2 (paricalcitol) and the prohormone 1alpha-OH-vitamin D2 (doxercalciferol) have been proposed as alternatives which may cause less hypercalcemia and elevated Ca x P, while still suppressing PTH.

METHODS

We performed a prospective study to assess the acute bone mobilization effects of very high doses of paricalcitol and doxercalciferol. 13 hemodialysis patients received 160 mcg of paricalcitol and 120 mcg of doxercalciferol on 2 separate occasions in a research center while on a low calcium, low phosphorus diet, and sevelamer alone as a phosphorus binder. Changes in Ca, PO4, and PTH were measured over 36 h.

RESULTS

Serum phosphorus rose faster, and peaked significantly higher at 36 h following doxercalciferol (2.12 +/- 0.11 mmol/l) than paricalcitol (1.85 +/- 0.07 mmol/l; p = 0.025). Ca x P product also rose more following doxercalciferol than paricalcitol, and peaked higher at 36 h (5.02 +/- 0.26 vs. 4.54 +/- 0.21 mmol/l; p = 0.061). In contrast, suppression of PTH at 36 h was comparable (63% after paricalcitol and 65% with doxercalciferol).

CONCLUSION

Consistent with animal studies, paricalcitol provides profound PTH suppression, while stimulating bone resorption and/or intestinal absorption less than doxercalciferol, resulting in less elevation of serum phosphorus and Ca x P.

Accurate mass liquid chromatography/mass spectrometry on quadrupole orthogonal acceleration time-of-flight mass analyzers using switching between separate sample and reference sprays. 2. Applications using the dual-electrospray ion source

A new electrospray dual sprayer, LockSpray, was developed for accurate mass measurements on a quadrupole orthogonal acceleration time-of-flight mass spectrometer (oa-Q-ToF). With the dual-sprayer ion source, both sprays are orthogonal to each other. A mechanism similar to the one employed on the multiplexed electrospray source (MUX) allows switching between reference and sample sprayer. The reference sprayer is optimized for low flow rates, whereas the sample sprayer is a conventional Z-spray type sprayer. Earlier work using a modified MUX ion source on an orthogonal acceleration time-of-flight instrument showed promising results. In this paper, examples obtained with the LockSpray, specifically designed for accurate mass measurements on an oa-Q-ToF, are presented. The examples include results obtained for the identification of impurities in drug substances such as cimetidine and rosiglitazone, using accurate mass tandem mass spectrometry in both positive and negative ion electrospray modes. Good mass accuracies, i.e., within 2 mDa of the theoretical value, were obtained in MS and MS/MS operation.

Structures of recombinant native and E202Q mutant human acetylcholinesterase complexed with the snake-venom toxin fasciculin-II

Structures of recombinant wild-type human acetylcholinesterase and of its E202Q mutant as complexes with fasciculin-II, a 'three-finger' polypeptide toxin purified from the venom of the eastern green mamba (Dendroaspis angusticeps), are reported. The structure of the complex of the wild-type enzyme was solved to 2.8 A resolution by molecular replacement starting from the structure of the complex of Torpedo californica acetylcholinesterase with fasciculin-II and verified by starting from a similar complex with mouse acetylcholinesterase. The overall structure is surprisingly similar to that of the T. californica enzyme with fasciculin-II and, as expected, to that of the mouse acetylcholinesterase complex. The structure of the E202Q mutant complex was refined starting from the corresponding wild-type human acetylcholinesterase structure, using the 2.7 A resolution data set collected. Comparison of the two structures shows that removal of the charged group from the protein core and its substitution by a neutral isosteric moiety does not disrupt the functional architecture of the active centre. One of the elements of this architecture is thought to be a hydrogen-bond network including residues Glu202, Glu450, Tyr133 and two bridging molecules of water, which is conserved in other vertebrate acetylcholinesterases as well as in the human enzyme. The present findings are consistent with the notion that the main role of this network is the proper positioning of the Glu202 carboxylate relative to the catalytic triad, thus defining its functional role in the interaction of acetylcholinesterase with substrates and inhibitors.

Accurate mass liquid chromatography/mass spectrometry on orthogonal acceleration time-of-flight mass analyzers using switching between separate sample and reference sprays. 1. Proof of concept

This paper describes the use of two separate electrosprays for introducing sample and reference for accurate mass liquid chromatography/mass spectrometry (LC/MS) on an orthogonal acceleration time-of-flight mass analyzer. This is carried out using an adaptation of the multiplexed electrospray ion source in which only two of the sprays are utilized. Results are shown for the positive ion detection of trace-level components in complex matrixes and good mass accuracies are obtained, even for very low level components. An example of accurate mass measurements obtained using negative ion LC/MS is also shown. To obtain additional structural information, an example of cone voltage fragmentation is included and shows that good mass accuracy can be obtained for both precursor and fragment ions.

Hydrophobic protein that copurifies with human brain acetylcholinesterase: amino acid sequence, genomic organization, and chromosomal localization

The mechanism of attachment of acetylcholinesterase (AChE) to neuronal membranes in interneuronal synapses is poorly understood. We have isolated, sequenced, and cloned a hydrophobic protein that copurifies with AChE from human caudate nucleus and that we propose forms a part of a complex of membrane proteins attached to this enzyme. It is a short protein of 136 amino acids and has a molecular mass of 18 kDa. The sequence contains stretches of both hydrophobic and hydrophilic amino acids and two cysteine residues. Analysis of the genomic sequence reveals that the coding region is divided among five short exons. Fluorescence in situ hybridization localizes the gene to chromosome 6p21.32-p21.2. Northern blot analysis shows that this gene is widely expressed in the brain with an expression pattern that parallels that of AChE.

High throughput liquid chromatography/mass spectrometric analyses using a novel multiplexed electrospray interface

A novel four- channel multiplexed electrospray liquid chromatography interface is described. This device has been used to analyse both single components and mixtures by liquid chromatography/mass spectrometry (LC/MS) as well as synthetic samples prepared by automated procedures. These data provided unambiguous molecular weight assignments to both major components and synthetic by-products in these samples. In this work particular attention has also been paid to the elimination of interchannel crosstalk. Copyright 1999 John Wiley & Sons, Ltd.

aCHEdb: the database system for ESTHER, the alpha/beta fold family of proteins and the Cholinesterase gene server

Acetylcholinesterase belongs to a family of proteins, the alpha/beta hydrolase fold family, whose constituents evolutionarily diverged from a common ancestor and share a similar structure of a central beta sheet surrounded by alpha helices. These proteins fulfil a wide range of physiological functions (hydrolases, adhesion molecules, hormone precursors) [Krejci,E., Duval,N., Chatonnet,A., Vincens,P. and Massoulié,J. (1991) Proc. Natl. Acad. Sci. USA , 88, 6647-6651]. ESTHER (for esterases, alpha/beta hydrolase enzymes and relatives) is a database aimed at collecting in one information system, sequence data together with biological annotations and experimental biochemical results related to the structure-function analysis of the enzymes of the family. The major upgrade of the database comes from the use of a new database management system: aCHEdb which uses the ACeDB program designed by Richard Durbin and Jean Thierry-Mieg. It can be found at http://www.ensam.inra.fr/cholinesterase

The evolution of MHC diversity by segmental duplication and transposition of retroelements

Sequence analysis of a 237 kb genomic fragment from the central region of the MHC has revealed that the HLA-B and HLA-C genes are contained within duplicated segments peri-B (53 kb) and peri-C (48 kb), respectively, and separated by an intervening sequence (IF) of 30 kb. The peri-B and peri-C segments share at least 90% sequence homology except when interrupted by insertions/deletions including Alu, L1, an endogenous retrovirus, and pseudogenes. The sequences of peri-B, IF, and peri-C were searched for the presence of Alu elements to use as markers of evolution, chromosomal rearrangements, and polymorphism. Of 29 Alu elements, 14 were identified in peri-B, 11 in peri-C, and 4 in IF. The Alu elements in peri-B and peri-C clustered phylogenetically into two clades which were classified as "preduplication" and "postduplication" clades. Four Alu J elements that are shared by peri-B and peri-C and are flanked by homologous sequences in their paralogous locations, respectively, clustered into a "preduplication" clade. By contrast, the majority of Alu elements, which are unique to either peri-B or peri-C, clustered into a postduplication clade together with the Alu consensus subfamily members ranging from platyrrhine-specific (Spqxcg) to catarrhine-specific Alu sequences (Y). The insertion of platyrrhine-specific Alu elements in postduplication locations of peri-B and peri-C implies that these two segments are the products of a duplication which occurred in primates prior to the divergence of the New World primate from the human lineage (35-44 mya). Examination of the paralogous Alu integration sites revealed that 9 of 14 postduplication Alu sequences have produced microsatellites of different length and sequence within the Alu 3'-poly A tail. The present analysis supports the hypothesis that HLA-B and HLA-C genes are products of an extended segmental duplication between 44 and 81 million years ago (mya), and that subsequent diversification of both genomic segments occurred because of the mobility and mutation of retroelements such as Alu repeats.

Primary care, process improvement, and turmoil

The current health care environment in the United States is in turmoil, especially in regions that are further ahead in the transition from free-for-service to managed care. This article examines turmoil within primary care during a health-maintenance-organization-sponsored and federally funded randomized trial of using continuous quality improvement for adult clinical preventive services. The external and internal changes in structure and leadership occurring in primary care clinics are profound and prevalent. The sponsors of the project have responded to the turmoil by encouraging greater leadership involvement within the clinic and by supporting more skill building for change management.

Interactions underlying subunit association in cholinesterases

Cholinesterases occur in a family of molecular forms, both as homo-oligomers of catalytic subunits, which can be either soluble, amphiphilic or lipid-anchored to the membrane; and hetero-oligomers of catalytic subunits and structural subunits. The structural subunits afford a method for precise localization of cholinesterases for specific function. A number of mutagenesis studies suggest that the C-terminal region of one alternatively spliced form of cholinesterase is involved in association of catalytic subunits into tetramers and in the association of these tetramers with structural subunits, however, there is currently no structural information about this region. In addition, none of the mutagenesis studies have clearly defined the residues important in these interactions. Here, multiple sequence alignment, structure prediction techniques and analysis of three-dimensional structural data are combined with a re-examination of mutagenesis and biochemical data. Three-dimensional models for the C-terminal region and for soluble tetrameric cholinesterase are proposed, and a set of rules governing subunit association are formulated. The simple model for association of catalytic and structural subunits presented is consistent with data for all known cholinesterases from species as divergent as nematode and man.

The alpha/beta fold family of proteins database and the cholinesterase gene server ESTHER

ESTHER (for esterases, alpha/betahydrolase enzyme and relatives) is a database of sequences phylogenetically related to cholinesterases. These sequences define a homogeneous group of enzymes (carboxylesterases, lipases and hormone-sensitive lipases) sharing a similar structure of a central beta-sheet surrounded by alpha-helices. Among these proteins a wide range of functions can be found (hydrolases, adhesion molecules, hormone precursors). The purpose of ESTHER is to help comparison of structures and functions of members of the family. Since the last release, new features have been added to the server. A BLAST comparison tool allows sequence homology searches within the database sequences. New sections are available: kinetics and inhibitors of cholinesterases, fasciculin-acetylcholinesterase interaction and a gene structure review. The mutation analysis compilation has been improved with three-dimensional images. A mailing list has been created.

Identification of the gene encoding DNA topoisomerase I from Candida albicans

A gene encoding a type I topoisomerase (TOP1) was isolated from Candida albicans, sequenced, and expressed in Saccharomyces cerevisiae. The TOP1 gene was identified from a C. albicans genomic library by hybridization with the product of a polymerase chain reaction with degenerate primer sets encoding regions conserved in other TOP1 genes. A clone containing an open reading frame of 2463 bp and predicted to encode a protein of 778 amino acids with sequence similarity to eukaryotic type I topoisomerases was identified. The C. albicans TOP1 gene restored camptothecin sensitivity and increased the topoisomerase activity in S. cerevisiae, indicating that the DNA fragment encodes a functional C. albicans topoisomerase I.

Involvement of the NMDA receptor in a non-cholinergic action of acetylcholinesterase in guinea-pig substantia nigra pars compacta neurons

Evidence is accumulating that a soluble, secretory form of acetylcholinesterase may have novel, non-cholinergic functions in certain brain regions, such as the substantia nigra. In this study, application of human recombinant acetylcholinesterase (rhAChE) to pars compacta neurons in the rostral substantia nigra resulted in a sustained hyperpolarization that was not only mimicked by application of N-methyl-D-aspartate (NMDA) but also blocked by the NMDA receptor antagonists MK8O1 and 2-amino-5-phosphonopentanoic acid. Neither the rhAChE- nor the NMDA-induced hyperpolarization was seen when the calcium chelator BAPTA was injected into the neuron; hence the effect is mediated by accumulation of intracellular calcium. This intracellular calcium appears sufficient to compromise neuronal metabolism since the rhAChE-induced hyperpolarization was reversed by application of the K-ATP channel antagonist tolbutamide. Butyrylcholinesterase, a protein of similar molecular weight to acetylcholinesterase, which also hydrolyses acetylcholine, had no effect whatsoever. The results suggest that, independent of its normal catalytic function, acetylcholinesterase can act via the NMDA receptor complex to enhance calcium entry into nigral neurons and jeopardize cell metabolism. This non-classical action of acetylcholinesterase might thus be an important factor in the mechanisms underlying parkinsonian neurodegeneration.

The single-staff model for bone marrow transplantation

This paper will demonstrate the advantages of pursuing an integrated model of care that utilizes one staff of caregivers in one facility for all phases of patient care from the time of patient evaluation through the time the patient returns to the care of his or her primary physician. We took the opportunity afforded by the development of a new program at the University of Alabama at Birmingham, the Bone Marrow Transplantation (BMT) Program, to reconsider as many variables as possible in an attempt to develop a model of care that would represent the best of all worlds, i.e., high levels of quality of care, quality of life, staff job enrichment, patient convenience, operational efficiency, and cost reduction.

National Surgical Adjuvant Breast and Bowel Project's Breast Cancer Prevention Trial

The Breast Cancer Prevention Trial is the largest breast cancer prevention study ever undertaken. Administered by the National Surgical Adjuvant Breast and Bowel Project, it is the first trial seeking to demonstrate whether a drug, tamoxifen, can prevent breast cancer in high-risk women. The objectives of this trial are to determine whether tamoxifen is effective in 1) reducing the incidence of invasive breast cancer, 2) reducing breast cancer mortality, 3) reducing deaths from cardiovascular disease, and 4) reducing bone fractures. In addition, the study will evaluate side effects, toxicity, and the quality of life of all study participants.

Psychological disturbances and an exaggerated response to pain in patients with whiplash injury

Psychological state, response to pain and style of interpreting everyday experiences were measured in 32 patients who had suffered a whiplash injury 1-84 months before the study. For comparison, measures were also obtained in 15 general practice attenders. Ratings of depression and anxiety were greater in patients than in controls, and patients reported more cold-induced pain during a cold pressor test. Within the patient sample, anxious subjects gave the highest ratings of cold-induced pain. Those with the longest history of pain gave the highest ratings of whiplash injury pain, and were most depressed. Most of these patients were involved in litigation. The findings demonstrate that, like most patients with chronic pain, whiplash injury sufferers are anxious and depressed. Their psychological distress could be aggravated by litigation. Behavioural assessment and treatment of chronic pain syndromes such as whiplash injury could benefit from early evaluation of the patient's psychological state, and response to standard painful stimuli.

Long-term effects of calcium carbonate and 2.5 mEq/liter calcium dialysate on mineral metabolism

Many investigators have shown that calcium carbonate (CaCO3) is an effective phosphate binder which also prevents the potential disabling effects of aluminum (Al) accumulation. However, hypercalcemia may develop in a substantial numbers of patients. Thus, to control serum phosphate (PO4) and prevent hypercalcemia, we performed studies in 21 patients on maintenance hemodialysis in which, in addition to the oral administration of CaCO3, the concentration of calcium (Ca) in the dialysate was reduced from 3.25 to 2.5 mEq/liter. The studies were divided in three periods: I. control, on Al-binders (one month); II. no Al-binders (one month); III. CaCO3 (seven months). Blood was obtained three times/week before dialysis for the first five months of the study and once a week for the remaining four months. During the control period, the mean serum calcium was 8.86 +/- 0.08 mg/dl. The value decreased to 8.65 +/- 0.07 mg/dl when phosphate binders containing aluminum were discontinued, and increased to 9.19 +/- 0.07 mg/dl (P less than 0.001 compared to period II) during oral supplementation with calcium carbonate. The mean serum phosphorus was 5.03 +/- 0.07 mg/dl during the control period, and increased to 7.29 +/- 0.91 mg/dl (P less than 0.001) after phosphate binders were discontinued. It decreased to 4.95 +/- 0.06 mg/dl (P less than 0.001) with the administration of calcium carbonate. During CaCO3 administration, serum Al decreased from 64.2 +/- 8.5 to 37.1 +/- 3.6 and 25.1 +/- 3.0 micrograms/liter (P less than 0.001) at three and seven months, respectively. Serum parathyroid hormone (PTH) decreased by 20%.(ABSTRACT TRUNCATED AT 250 WORDS)