SARS-CoV-2 hijacks a cell damage response, which induces transcription of a more efficient Spike S-acyltransferase

SARS-CoV-2 infection requires Spike protein-mediated fusion between the viral and cellular membranes. The fusogenic activity of Spike depends on its post-translational lipid modification by host S-acyltransferases, predominantly ZDHHC20. Previous observations indicate that SARS-CoV-2 infection augments the S-acylation of Spike when compared to mere Spike transfection. Here, we find that SARS-CoV-2 infection triggers a change in the transcriptional start site of the zdhhc20 gene, both in cells and in an in vivo infection model, resulting in a 67-amino-acid-long N-terminally extended protein with approx. 40 times higher Spike acylating activity, resulting in enhanced fusion of viruses with host cells. Furthermore, we observed the same induced transcriptional change in response to other challenges, such as chemically induced colitis and pore-forming toxins, indicating that SARS-CoV-2 hijacks an existing cell damage response pathway to optimize it fusion glycoprotein.

Dynamics of CLIMP-63 S-acylation control ER morphology

The complex architecture of the endoplasmic reticulum (ER) comprises distinct dynamic features, many at the nanoscale, that enable the coexistence of the nuclear envelope, regions of dense sheets and a branched tubular network that spans the cytoplasm. A key player in the formation of ER sheets is cytoskeleton-linking membrane protein 63 (CLIMP-63). The mechanisms by which CLIMP-63 coordinates ER structure remain elusive. Here, we address the impact of S-acylation, a reversible post-translational lipid modification, on CLIMP-63 cellular distribution and function. Combining native mass-spectrometry, with kinetic analysis of acylation and deacylation, and data-driven mathematical modelling, we obtain in-depth understanding of the CLIMP-63 life cycle. In the ER, it assembles into trimeric units. These occasionally exit the ER to reach the plasma membrane. However, the majority undergoes S-acylation by ZDHHC6 in the ER where they further assemble into highly stable super-complexes. Using super-resolution microscopy and focused ion beam electron microscopy, we show that CLIMP-63 acylation-deacylation controls the abundance and fenestration of ER sheets. Overall, this study uncovers a dynamic lipid post-translational regulation of ER architecture.

S-acylation controls SARS-CoV-2 membrane lipid organization and enhances infectivity

SARS-CoV-2 virions are surrounded by a lipid bilayer that contains membrane proteins such as spike, responsible for target-cell binding and virus fusion. We found that during SARS-CoV-2 infection, spike becomes lipid modified, through the sequential action of the S-acyltransferases ZDHHC20 and 9. Particularly striking is the rapid acylation of spike on 10 cytosolic cysteines within the ER and Golgi. Using a combination of computational, lipidomics, and biochemical approaches, we show that this massive lipidation controls spike biogenesis and degradation, and drives the formation of localized ordered cholesterol and sphingolipid-rich lipid nanodomains in the early Golgi, where viral budding occurs. Finally, S-acylation of spike allows the formation of viruses with enhanced fusion capacity. Our study points toward S-acylating enzymes and lipid biosynthesis enzymes as novel therapeutic anti-viral targets.

European task force on atopic dermatitis position paper: treatment of parental atopic dermatitis during preconception, pregnancy and lactation period

Atopic dermatitis (AD) is a common inflammatory skin disease that affects both children and adults, including a large number of adults of reproductive age. Several guidelines for the treatment of AD exist, yet specific recommendations for the treatment of pregnant or lactating women and for adults planning to have a child are often lacking. This position paper from the European Task force on Atopic Dermatitis (ETFAD) is based on up-to-date scientific literature on treating pregnant and lactating women as wells as adults with AD planning to have a child. It is based on the expert opinions of members of the ETFAD and on existing safety data on the proposed treatments, many of which are derived from patients with other inflammatory diseases or from transplantation medicine. For treating future parents, as well as pregnant and lactating women with AD, the use of topical treatments including moisturizers, topical corticosteroids, tacrolimus, antiseptics such as chlorhexidine, octenidine, potassium permanganate and sodium hypochlorite (bleach) is deemed to be safe. Ultraviolet (UV) therapy may also be used. Systemic treatment should be prescribed only after careful consideration. According to the opinion of the ETFAD, treatment should be restricted to systemic corticosteroids and cyclosporine A, and, in selected cases, azathioprine.

Identification and dynamics of the human ZDHHC16-ZDHHC6 palmitoylation cascade

S-Palmitoylation is the only reversible post-translational lipid modification. Knowledge about the DHHC palmitoyltransferase family is still limited. Here we show that human ZDHHC6, which modifies key proteins of the endoplasmic reticulum, is controlled by an upstream palmitoyltransferase, ZDHHC16, revealing the first palmitoylation cascade. The combination of site specific mutagenesis of the three ZDHHC6 palmitoylation sites, experimental determination of kinetic parameters and data-driven mathematical modelling allowed us to obtain detailed information on the eight differentially palmitoylated ZDHHC6 species. We found that species rapidly interconvert through the action of ZDHHC16 and the Acyl Protein Thioesterase APT2, that each species varies in terms of turnover rate and activity, altogether allowing the cell to robustly tune its ZDHHC6 activity.

CMG2/ANTXR2 regulates extracellular collagen VI which accumulates in hyaline fibromatosis syndrome

Loss-of-function mutations in capillary morphogenesis gene 2 (CMG2/ANTXR2), a transmembrane surface protein, cause hyaline fibromatosis syndrome (HFS), a severe genetic disorder that is characterized by large subcutaneous nodules, gingival hypertrophy and severe painful joint contracture. Here we show that CMG2 is an important regulator of collagen VI homoeostasis. CMG2 loss of function promotes accumulation of collagen VI in patients, leading in particular to nodule formation. Similarly, collagen VI accumulates massively in uteri of Antxr2-/- mice, which do not display changes in collagen gene expression, and leads to progressive fibrosis and sterility. Crossing Antxr2-/- with Col6a1-/- mice leads to restoration of uterine structure and reversion of female infertility. We also demonstrate that CMG2 may act as a signalling receptor for collagen VI and mediates its intracellular degradation.

Patient-Oriented SCORAD (PO-SCORAD): a new self-assessment scale in atopic dermatitis validated in Europe

BACKGROUND

Patient-oriented medicine is an emerging concept, encouraged by the World Health Organization, to greater involvement of the patient in the management of chronic diseases. The Patient-Oriented SCORing Atopic Dermatitis (PO-SCORAD) index is a self-assessment score allowing the patient to comprehensively evaluate the actual course of atopic dermatitis (AD), using subjective and objective criteria derived mainly from the SCORAD, a validated AD severity clinical assessment tool.

OBJECTIVES

To validate the PO-SCORAD index in a large European population of patients exhibiting all forms of AD severity by assessing its correlation with the SCORAD index.

PATIENTS/METHODS

Four hundred and seventy-one patients (185 adults, 286 children) consulting for AD in hospitals from 9 European countries were recruited. The investigators and the patients used the SCORAD and PO-SCORAD scales, respectively, to assess AD severity at inclusion (D0) and 28 ± 7 days later (D28).

RESULTS

Patient-Oriented SCORing Atopic Dermatitis and SCORAD scores were significantly correlated at D0 [r = 0.67 (95% CI: 0.62; 0.72), P < 0.0001]. Consistency was confirmed at D28, with a stronger linear correlation between both scales [r = 0.79 (95% CI: 0.75; 0.83), P < 0.0001]. Absolute changes from baseline in SCORAD and PO-SCORAD scores were also significantly correlated [r= 0.71 (95% CI: 0.64; 0.76), P < 0.0001]. Although no specific intervention was investigated, AD improved over the study, with a decrease of PO-SCORAD and SCORAD scores from D0 to D28 by -19.19% and -24.39%, respectively. The consistency of the correlations was similar in the adult and children groups.

CONCLUSIONS

This study validated the use of PO-SCORAD to self-assess AD severity and demonstrated its good correlation with SCORAD.

Endocytosis of the anthrax toxin is mediated by clathrin, actin and unconventional adaptors

The anthrax toxin is a tripartite toxin, where the two enzymatic subunits require the third subunit, the protective antigen (PA), to interact with cells and be escorted to their cytoplasmic targets. PA binds to cells via one of two receptors, TEM8 and CMG2. Interestingly, the toxin times and triggers its own endocytosis, in particular through the heptamerization of PA. Here we show that PA triggers the ubiquitination of its receptors in a β-arrestin-dependent manner and that this step is required for clathrin-mediated endocytosis. In addition, we find that endocytosis is dependent on the heterotetrameric adaptor AP-1 but not the more conventional AP-2. Finally, we show that endocytosis of PA is strongly dependent on actin. Unexpectedly, actin was also found to be essential for efficient heptamerization of PA, but only when bound to one of its 2 receptors, TEM8, due to the active organization of TEM8 into actin-dependent domains. Endocytic pathways are highly modular systems. Here we identify some of the key players that allow efficient heptamerization of PA and subsequent ubiquitin-dependent, clathrin-mediated endocytosis of the anthrax toxin.

Bacillus anthracis is the bacterium responsible for the anthrax disease. Its virulence is mainly due to 2 factors, the anthrax toxin and the anti-phagocytic capsule. This toxin is composed of three independent polypeptide chains. Two of these have enzymatic activity and are responsible for the effects of the toxin. The third has no activity but is absolutely required to bring the 2 enzymatic subunits into the cell where they act. If one blocks entry into the cells, one blocks the effects of these toxins, which is why it is important to understand how the toxin enters into the cell at the molecular level. Here we identified various molecules that are involved in efficiently bringing the toxin into the cell. First, we found that the actin cytoskeleton plays an important role in organizing one of the two anthrax toxin receptors at the cell surface. Second, we found a cytosolic protein, β-arrestin, that is required to modify the intracellular part of the toxin receptor, to allow uptake. Finally, we directly show, for the first time, that anthrax toxin uptake is mediated by the so-called clathrin-dependent pathway, a very modular entry pathway, but that the toxin utilizes this pathway in an unconventional way.

Functional interactions between anthrax toxin receptors and the WNT signalling protein LRP6

To exert its activity, anthrax toxin must be endocytosed and its enzymatic toxic subunits delivered to the cytoplasm. It has been proposed that, in addition to the anthrax toxin receptors (ATRs), lipoprotein-receptor-related protein 6 (LRP6), known for its role in Wnt signalling, is also required for toxin endocytosis. These findings have however been challenged. We show that LRP6 can indeed form a complex with ATRs, and that this interaction plays a role both in Wnt signalling and in anthrax toxin endocytosis. We found that ATRs control the levels of LRP6 in cells, and thus the Wnt signalling capacity. RNAi against ATRs indeed led to a drastic decrease in LRP6 levels and a subsequent drop in Wnt signalling. Conversely, LRP6 plays a role in anthrax toxin endocytosis, but is not essential. We indeed found that toxin binding triggered tyrosine phosphorylation of LRP6, induced its redistribution into detergent-resistant domains, and its subsequent endocytosis. RNAis against LRP6 strongly delayed toxin endocytosis. As the physiological role of ATRs is probably to interact with the extracellular matrix, our findings raise the interesting possibility that, through the ATR-LRP6 interaction, adhesion to the extracellular matrix could locally control Wnt signalling.

Treatment of patients with atopic dermatitis using wet-wrap dressings with diluted steroids and/or emollients. An expert panel's opinion and review of the literature

BACKGROUND

The use of dampened bandages to reduce inflamed eczema (synonyme dermatitis) is an old remedy. In order to evaluate the current indications for so-called wet-wrap treatment (WWT) for atopic dermatitis (AD), and to compare the different currently recognized methods, a group of experts critically reviewed their own expertise on WWT in respect to the existing literature on the subject.

RESULTS

WWT is well tolerated in eczema due to the cooling effect on the skin and the rapid improvement in skin inflammation. It has been shown to be an extremely effective treatment for acute erythrodermic dermatitis, therapy-resistant AD and intolerable pruritus. Advantages of WWT include rapid response to therapy, reduction in itch and sleep disturbance, and potential for reduction in usage of topical corticosteroids (TCS). However, disadvantages include high cost, the necessity for special training in usage, potential for increased TCS absorption, increased cutaneous infections and folliculitis, and poor tolerability. Precautions to reduce the risks of long-term treatment should include education, monitoring of weight and height and, if necessary, serum cortisol levels. In adolescents the risk of striae from TCS absorption around puberty is high, and WWT with TCS in this age group should be used as a short-term therapy only and with extreme caution. To reduce risks, dilutions of steroids may be used ranging from 5 to 10%. In the maintenance phase this treatment can be rotated with the use of emollients only. Low potency TCS should be used on the face (with a mask).

CONCLUSION

WWT using diluted steroids is a relatively safe addition to the therapeutic treatment options for children and adults with severe and/or refractory AD. Explanation and education is extremely important in the treatment of AD and WWT should only be employed by practitioners trained in its use. Specialized nursing care is essential, especially when using WWT for prolonged periods.

Initiation and limitation of Ly-49A NK cell receptor acquisition by T cell factor-1

The establishment of clonally variable expression of MHC class I-specific receptors by NK cells is not well understood. The Ly-49A receptor is used by approximately 20% of NK cells, whereby most cells express either the maternal or paternal allele and few express simultaneously both alleles. We have previously shown that NK cells expressing Ly-49A were reduced or almost absent in mice harboring a single or no functional allele of the transcription factor T cell factor-1 (TCF-1), respectively. In this study, we show that enforced expression of TCF-1 in transgenic mice yields an expanded Ly-49A subset. Even though the frequencies of Ly-49A(+) NK cells varied as a function of the TCF-1 dosage, the relative abundance of mono- and biallelic Ly-49A cells was maintained. Mono- and biallelic Ly-49A NK cells were also observed in mice expressing exclusively a transgenic TCF-1, i.e., expressing a fixed amount of TCF-1 in all NK cells. These findings suggest that Ly-49A acquisition is a stochastic event due to limiting TCF-1 availability, rather than the consequence of clonally variable expression of the endogenous TCF-1 locus. Efficient Ly-49A acquisition depended on the expression of a TCF-1 isoform, which included a domain known to associate with the TCF-1 coactivator beta-catenin. Indeed, the proximal Ly-49A promoter was beta-catenin responsive in reporter gene assays. We thus propose that Ly-49A receptor expression is induced from a single allele in occasional NK cells due to a limitation in the amount of a transcription factor complex requiring TCF-1.

[Positioning of the premaxilla in cases of bilateral cleft lip, alveolus and palate using Latham's appliance]

SUBJECT MATTER: In cases of bilateral cleft lip, alveolus and palate, preoperative positioning of the premaxilla using Latham's appliance has been described. This method is controversial, since it may cause growth defects.

PATIENTS AND METHODS

From 1992 to 2000, Latham's appliance was inserted preoperatively into 20 patients with bilateral lip, alveolus and palate clefts with extreme premaxillary protrusion. Pin fixation ensued at the age of 3 months. After adjustment of the premaxilla, the soft palate was closed and bilateral lip adhesion as well as bilateral gingivoperiosteoplasty were performed directly after the removal of the appliance. Final lip closure took place 4-6 weeks later. At the age of 2 years, the hard palate was closed. Evaluation was based on combined face-maxilla models, standard photographs and, when available, lateral skull x-rays showing the relative position of the segments, the influence of Latham's appliance on the nasal septum and the relation of the upper jaw to the skull base and mandibula.

RESULTS

In all cases, a satisfactory alveolar alignment was achieved; thickening and curvature of the nasal septum occurred but receded. Neither growth disturbances nor dental germ damage were seen. In two cases, complications arose from suture dehiscence of the lip adhesion: in one patient, a screw defect caused a loosening of the appliance and there was also a transmigration of the postpremaxillary pin.

CONCLUSIONS

On the basis of our experience, the use of Latham's appliance, combined with consistent orthodontic supervision and, if necessary, treatment, represents a practical option for the treatment of bilateral cleft lip, alveolus and palate, especially in cases with extreme protrusion of the premaxilla.

A pervaporation-bio-hybridreactor (PBHR) for improved aroma biosynthesis with submerged culture of Ceratocystis fimbriata

In the present study a Pervaporation-bio-hybridreactor was investigated for the improved biotechnological production of volatile flavour compounds. The mixture of esters and alcohols produced by the fungus Ceratocystis fimbriata had a fruity, banana-like odour and can legally be defined as "natural flavour". Increasing consumer demand and high market prices make the production of bioflavours an attractive alternative to chemical synthesises. However, the yield of biotechnological flavour production is often very low due to product inhibition. In situ product-removal processes can yield higher productivities by preventing product inhibition. A bioreactor with an integrated pervaporation membrane was used to determine the effects of in-situ product removal on the metabolic productivity of C. fimbriata. Fed-batch fermentations with and without integrated product removal were conducted and the performance of the processes in terms of productivities was compared. Improved productivities were observed for all products. Figure 1a and 1b show the increased amount of product gained through the application of the PBHR with fed-batch fermentation.

A role for the src family kinase Fyn in NK cell activation and the formation of the repertoire of Ly49 receptors

NK cell function is regulated by a dual receptor system, which integrates signals from triggering receptors and MHC class I-specific inhibitory receptors. We show here that the src family kinase Fyn is required for efficient, NK cell-mediated lysis of target cells, which lack both self-MHC class I molecules and ligands for NKG2D, an activating NK cell receptor. In contrast, NK cell inhibition by the MHC class I-specific receptor Ly49A was independent of Fyn, suggesting that Fyn is specifically required for NK cell activation via non-MHC receptor(s). Compared to wild type, significantly fewer Fyn-deficient NK cells expressed the inhibitory Ly49A receptor. The presence of a transgenic Ly49A receptor together with its H-2(d) ligand strongly reduced the usage of endogenous Ly49 receptors in Fyn-deficient mice. These data suggest a model in which the repertoire of inhibitory Ly49 receptors is formed under the influenced of Fyn-dependent NK cell activation as well as the respective MHC class I environment. NK cells may acquire Ly49 receptors until they generate sufficient inhibitory signals to balance their activation levels. Such a process would ensure the induction of NK cell self-tolerance.

Test-retest-reliability and validity of the Kinesiology muscle test

OBJECTIVES

To assess the test-retest-reliability and validity of the Health Kinesiology muscle test.

PATIENTS

Seven patients with clinically and allergologically confirmed wasp venom allergy.

DESIGN

Four Health Kinesiology-examiners tested each patient in a random order for 10 verum and 10 placebo bottles. All examiners used the anterior deltoid as indicator muscle. Patients and examiners were completely blinded.

OUTCOME MEASURES

Weak muscle holds were rated as 'sensitivity' towards the test substance, stable holding as normal (not sensitive).

RESULTS

An overall kappa of 0.03 (95%-CI: -0.02-0.07) indicates the test is not reliable. Individual kappas do not substantially vary from examiner to examiner. Sensitivity and specificity were estimated at 40% and 60%.

CONCLUSIONS

The results suggest that the use of Health Kinesiology as a diagnostic tool is not more useful than random guessing. This should at least be true in patients with insect venom allergy that are tested by examiners with average skills.

Positive and negative roles of the trans-acting T cell factor-1 for the acquisition of distinct Ly-49 MHC class I receptors by NK cells

Members of the Ly-49 gene family code for class I MHC-specific receptors that regulate NK cell function. Due to a combinatorial distribution of Ly-49 receptors, NK cells display considerable clonal heterogeneity. The acquisition of one Ly-49 receptor, Ly-49A is strictly dependent on the transcriptional trans-acting factor T cell-specific factor-1 (TCF-1). Indeed, TCF-1 binds to two sites in the Ly-49a promoter and regulates its activity, suggesting that the Ly-49a gene is a direct TCF-1 target. TCF-1 deficiency resulted in the altered usage of additional Ly-49 receptors. We show in this study, using TCF-1 beta(2)-microglobulin double-deficient mice, that these repertoire alterations are not due to Ly-49/MHC class I interactions. Our findings rather suggest a TCF-1-dependent, cell autonomous effect on the acquisition of multiple Ly-49 receptors. Besides reduced receptor usage (Ly-49A and D), we also observed no effect (Ly-49C) and significantly expanded (Ly-49G and I) receptor usage in the absence of TCF-1. These effects did not in all cases correlate with the presence of TCF binding sites in the respective proximal promoter. Therefore, besides TCF-1 binding to the proximal promoter, Ly-49 acquisition may also be regulated by TCF-1 binding to more distant cis-acting elements and/or by regulating the expression of additional trans-acting factors. Consistent with the observed differential, positive or negative role of TCF-1 for Ly-49 receptor acquisition, reporter gene assays revealed the presence of an inducing as well as a repressing TCF site in certain proximal Ly-49 promoters. These findings reveal an important role of TCF-1 for the formation of the NK cell receptor repertoire.

Amino acid sequences and hapten binding of catalytic and noncatalytic antibodies against N(alpha)-(5'-phosphopyridoxyl)-L-lysine

Upon immunization with a transition-state analog, only a minority of the hapten-binding antibodies will possess catalytic activity, which will vary in efficacy and substrate specificity. Here, the amino acid sequences of the variable domains of two pyridoxal-5'-phosphate-dependent catalytic and five noncatalytic hapten-binding antibodies raised by immunization with protein-conjugated N(alpha)-(5'-phosphopyridoxyl)-L-lysine (Gramatikova, S., Christen, P., 1997. J. Biol. Chem. 272, 9779-9784) were determined by sequencing their cDNAs. The analysis revealed that the light chains of this set of antibodies were closely related (pairwise identity 65-80%), whereas the heavy chains could be traced back to two different but related groups (intergroup identity 50-54%). The majority of the antibodies proved not to be clonally related, a finding which correlates with their differences in enantiomeric selectivity in ligand binding and reaction specificity. Only one noncatalytic antibody was found to be clonally related with a catalytic antibody, the sequence identity being >95% in both the V(H) and V(L) domains. The complementarity-determining regions were invariably abundant in tyrosine residues. Nitration of three to four tyrosine residues with tetranitromethane abolished hapten binding and catalytic activity. Partial protection by pyridoxal-5'-phosphate against inactivation suggested the presence of functionally important tyrosine residues in the binding sites of the antibodies.

Impaired natural killing of MHC class I-deficient targets by NK cells expressing a catalytically inactive form of SHP-1

NK cell function is negatively regulated by MHC class I-specific inhibitory receptors. Transduction of the inhibitory signal involves protein tyrosine phosphatases such as SHP-1 (SH2-containing protein tyrosine phosphatase-1). To investigate the role of SHP-1 for NK cell development and function, we generated mice expressing a catalytically inactive, dominant-negative mutant of SHP-1 (dnSHP-1). In this paper we show that expression of dnSHP-1 does not affect the generation of NK cells even though MHC receptor-mediated inhibition is partially impaired. Despite this defect, these NK cells do not kill syngeneic, normal target cells. In fact dnSHP-1-expressing NK cells are hyporesponsive toward MHC-deficient target cells, suggesting that non-MHC-specific NK cell activation is significantly reduced. In contrast, these NK cells mediate Ab-dependent cell-mediated cytotoxicity and prevent the engraftment with beta2-microglobulin-deficient bone marrow cells. A similar NK cell phenotype is observed in viable motheaten (mev) mice, which show reduced SHP-1 activity due to a mutation in the Shp-1 gene. In addition, NK cells in both mouse strains show a tendency to express more inhibitory MHC-specific Ly49 receptors. Our results demonstrate the importance of SHP-1 for the generation of functional NK cells, which are able to react efficiently to the absence of MHC class I molecules from normal target cells. Therefore, SHP-1 may play an as-yet-unrecognized role in some NK cell activation pathways. Alternatively, a reduced capacity to transduce SHP-1-dependent inhibitory signals during NK cell development may be compensated by the down-modulation of NK cell triggering pathways.

Hopelessness and its impact on rehabilitation outcome in schizophrenia -an exploratory study

The primary focus in contemporary psychiatry on symptoms and their neurobiological basis, although fundamentally important, is nevertheless incomplete. The long-term course and outcome of schizophrenia are determined not only by the disorder, but also by the interaction between the person and the disorder. Not only psychopathological symptoms but also cognitive variables such as negative self-concepts, low expectations and external loci of control can influence the patient's coping strategies and may lead to hopelessness and chronicity. Hopelessness here refers to a cognitive-affective state in which the patient perceives the disorder and its consequences to be beyond his control, feels helpless and has given up expecting to influence its course positively, thereby abandoning responsibility and active coping strategies. In a prospective study, we examined these relationships by using logistic regression in data from 46 schizophrenic outpatients who were participating in a vocational rehabilitation program. Negative self-concepts, external loci of control, and depression correlated to a higher extent with depressive-resigned coping strategies than did schizophrenic symptoms. Thus, poor rehabilitation outcome may be predicted to a high degree by the presence of external loci of control, pessimistic outcome expectancies, negative symptoms, and depressive-resigned coping strategies. After having eliminated the influence of negative symptoms, external control beliefs still had significant predictive value for the outcome. Rehabilitation outcome in schizophrenic patients can be only partially predicted by negative symptoms; the other predictive factor is whether the patient has already given up or not.

Mono-allelic Ly49 NK cell receptor expression

Each cell is equipped with two copies (alleles) of each autosomal gene. While the vast majority use both alleles, occasional genes are expressed from a single allele. The reason for mono-allelic expression is not always evident and can serve distinct purposes. First, it may facilitate the tight control over the dosage of certain gene products such as some growth factors and their receptors or X-linked genes. Second, the differential usage of the two parental alleles may reflect the mechanisms that ensure mono-specificity, e.g. olfactory receptors, T and B cell receptors. The context of allele-specific expression of the murine Ly49 natural killer (NK) cell receptor genes suggests that their allele-specific expression reflects a process that generates clonal variability.

Disposable-sheath, flexible gastroscope system versus standard gastroscopes: a prospective, randomized trial

BACKGROUND

Endoscopically transmitted infections due to inadequate disinfection are rare but well-recognized complications. A new prototype of a flexible, fiberoptic endoscope has been developed that uses a disposable sheath to cover and protect all working surfaces of the endoscope from contamination. The present study investigated the function, reprocessing, and hygienic status of this endoscope system in comparison with standard systems.

METHODS

In a prospective, randomized trial, 100 upper endoscopic procedures (50 standard, 50 sheathed) were performed. Analog rating scales were used to evaluate endoscopic performance and reprocessing. Reprocessing time, procedure duration, insertion depth, total instrument downtime, and problems occurring during the procedure were recorded. Microbiologic swabs were obtained from each endoscope.

RESULTS

Mean procedure duration was slightly longer with the sheathed system than with standard endoscope (9.9 vs. 8.4 min). Set up and reprocessing times, however, were significantly shorter with the Endosheath (8.9 vs. 48.4 min with the standard endoscope). The disposable-sheath endoscope system permits the rate of performance of procedures to be increased by a factor of up to 3.0. Both endoscopists and reprocessing personnel preferred the standard endoscope. No post-procedure sheath leakage or rupture was seen.

CONCLUSION

Our results suggest that the "disposable endoscope" may have important advantages in terms of decreased instrument turn-around time and potentially improved safety.

Clonal acquisition of the Ly49A NK cell receptor is dependent on the trans-acting factor TCF-1

Families of clonally expressed major histocompatibility complex (MHC) class I-specific receptors provide specificity to and regulate the function of natural killer (NK) cells. One of these receptors, mouse Ly49A, is expressed by 20% of NK cells and inhibits the killing of H-2D(d) but not D(b)-expressing target cells. Here, we show that the trans-acting factor TCF-1 binds to two sites in the Ly49A promoter and regulates its activity. Moreover, we find that TCF-1 determines the size of the Ly49A NK cell subset in vivo in a dosage-dependent manner. We propose that clonal Ly49A acquisition during NK cell development is regulated by TCF-1.

Neurotoxicity of prion peptide 106-126 not confirmed

Prion-related diseases are accompanied by neurodegeneration, astroglial proliferation and formation of proteinase K-resistant aggregates of the scrapie isoform of the prion protein (PrPSc). The synthetic PrP fragment 106-126 was reported to be neurotoxic towards cultured rat hippocampal neurons (Forloni, G., Angeretti, N., Chiesa, R., Monzani, E., Salmona, M., Bugiani, O. and Tagliavini, F. (1993) Nature 362, 543-546) and mouse cortical cells (Brown, D.R., Herms, J. and Kretzschmar, H.A. (1994) Neuroreport 5, 2057-2060). However, we found the viability of these and other neuronal cell types not to be impaired in the presence of PrP106-126 under widely varied sets of conditions. Aged preparations of the peptide as well as synthetic deamidated and isomerized derivatives that correspond to the aging products of the peptide proved also to lack neurotoxicity. Apparently, PrP106-126 cannot serve as a model for the interaction of PrP with neuronal cells.

Spontaneous deamidation and isomerization of Asn108 in prion peptide 106-126 and in full-length prion protein

In prion-related encephalopathies, the cellular prion protein (PrP(C)) undergoes a change in conformation to become the scrapie prion protein (PrP(Sc)) which forms infectious deposits in the brain. Conceivably, the conformational transition of PrP(C) to PrP(Sc) might be linked with posttranslational alterations in the covalent structure of a fraction of the PrP molecules. We tested a synthetic peptide corresponding to residues 106-126 of human PrP for the occurrence of spontaneous chemical modifications. The only asparagine residue, Asn108, was deamidated to aspartic acid and isoaspartic acid with a half-life of about 12 days. The same posttranslational modifications were found in recombinant murine full-length protein. On aging, 0.8 mol of isoaspartyl residue per mole of protein was detected by the protein-l-isoaspartyl methyltransferase assay (t(1/2) approximately 30 days). Mass spectrometry and Edman degradation of Lys-C fragments identified Asn108 in the amino-terminal flexible part of the protein to be partially converted to aspartic acid and isoaspartic acid. A second modification was the partial isomerization of Asp226' which is only present in rodents.