An adult Drosophila glioma model to highlight metabolic dysfunctions and evaluate the role of the serotonin 5-HT7 receptor as a potential therapeutic target

Gliomas account for 50% of brain cancers and are therefore the most common brain tumors. Molecular alterations involved in adult gliomas have been identified and mainly affect tyrosine kinase receptors with amplification and/or mutation of the epidermal growth factor receptor (EGFR) and its associated signaling pathways. Several targeted therapies have been developed, but current treatments remain ineffective for glioblastomas, the most severe forms. Thus, it is a priority to identify new pharmacological targets. Drosophila glioma models established in larvae and adults are useful to identify new genes and signaling pathways involved in glioma progression. Here, we used a Drosophila glioma model in adults, to characterize metabolic disturbances associated with glioma and assess the consequences of 5-HT7 R expression on glioma development. First, by using in vivo magnetic resonance imaging, we have shown that expression of the constitutively active forms of EGFR and PI3K in adult glial cells induces brain enlargement. Then, we explored altered cellular metabolism by using high-resolution magic angle spinning NMR and 1 H-13 C heteronuclear single quantum coherence solution states. Discriminant metabolites identified highlight the rewiring of metabolic pathways in glioma and associated cachexia phenotypes. Finally, the expression of 5-HT7 R in this adult model attenuates phenotypes associated with glioma development. Collectively, this whole-animal approach in Drosophila allowed us to provide several rapid and robust phenotype readouts, such as enlarged brain volume and glioma-associated cachexia, as well as to determine the metabolic pathways involved in glioma genesis and finally to confirm the interest of the 5-HT7 R in the treatment of glioma.

Cefiderocol activity is compromised by acquired extended-spectrum oxacillinases in Pseudomonas aeruginosa

OBJECTIVES

Cefiderocol has an excellent in vitro activity on clinical strains of Pseudomonas aeruginosa (P. aeruginosa). However, the resistance of some isolates has been associated with the production of some β-lactamases. Whether some acquired extended-spectrum oxacillinases (ES-OXA) common in this species may compromise the susceptibility of P. aeruginosa to cefiderocol has not been evaluated so far.

METHODS

Eighteen genes encoding OXA belonging to the major subgroups identified in P. aeruginosa OXA-1 (n = 3); - 2 (n = 5); - 10 (n = 8), and - 46 (n = 2) were cloned into pUCP24 shuttle vector and transferred into reference strain PAO1.

RESULTS

Although production of the OXA-1 subgroup enzymes did not alter cefiderocol MICs, the β-lactamases of OXA-2, OXA-46, and four variants of the OXA-10 subgroup resulted in an 8-fold to 32-fold decrease in susceptibility in the PAO1 background. Interestingly, point mutations Ala149Pro and Asp150Gly in OXA-2 subgroup, Trp154Cys and Gly157Asp in OXA-10 subgroup (all located in the Ω loop), and the duplication of a Thr206 and a Gly207 in the β5-β6 loop of OXA-10 subgroup were related to decreased susceptibility to cefiderocol. We also showed that some ES-OXA, including the most frequent ES-OXA in P. aeruginosa strains, OXA-19 (derived from OXA-10 subgroup), significantly compromised activity of cefiderocol in addition to ceftazidime, ceftolozane/tazobactam, and ceftazidime/avibactam in clinical strains.

CONCLUSION

This work shows that several ES-OXA have a significant effect on cefiderocol susceptibility. Of concern are the Trp154Cys and Gly157Asp mutations that occur in some of these β-lactamases, as they are associated with a decreased activity of the most recent cephalosporins introduced to combat P. aeruginosa infections.

Structure-function relationship of new peptides activating human Nav1.1

Nav1.1 is an important pharmacological target as this voltage-gated sodium channel is involved in neurological and cardiac syndromes. Channel activators are actively sought to try to compensate for haploinsufficiency in several of these pathologies. Herein we used a natural source of new peptide compounds active on ion channels and screened for drugs capable to inhibit channel inactivation as a way to compensate for decreased channel function. We discovered that JzTx-34 is highly active on Nav1.1 and subsequently performed a full structure-activity relationship investigation to identify its pharmacophore. These experiments will help interpret the mechanism of action of this and formerly identified peptides as well as the future identification of new peptides. We also reveal structural determinants that make natural ICK peptides active against Nav1.1 challenging to synthesize. Altogether, the knowledge gained by this study will help facilitate the discovery and development of new compounds active on this critical ion channel target.

The diversification of the antimicrobial peptides from marine worms is driven by environmental conditions

Antimicrobial peptides (AMPs) play a key role in the external immunity of animals, offering an interesting model for studying the influence of the environment on the diversification and evolution of immune effectors. Alvinellacin (ALV), arenicin (ARE) and polaricin (POL, a novel AMP identified here), characterized from three marine worms inhabiting contrasted habitats ('hot' vents, temperate and polar respectively), possess a well conserved BRICHOS domain in their precursor molecule despite a profound amino acid and structural diversification of the C-terminal part containing the core peptide. Data not only showed that ARE, ALV and POL display an optimal bactericidal activity against the bacteria typical of the habitat where each worm species lives but also that this killing efficacy is optimal under the thermochemical conditions encountered by their producers in their environment. Moreover, the correlation between species habitat and the cysteine contents of POL, ARE and ALV led us to investigate the importance of disulfide bridges in their biological efficacy as a function of abiotic pressures (pH and temperature). The construction of variants using non-proteinogenic residues instead of cysteines (α-aminobutyric acid variants) leading to AMPs devoid of disulfide bridges, provided evidence that the disulfide pattern of the three AMPs allows for a better bactericidal activity and suggests an adaptive way to sustain the fluctuations of the worm's environment. This work shows that the external immune effectors exemplified here by BRICHOS AMPs are evolving under strong diversifying environmental pressures to be structurally shaped and more efficient/specific under the ecological niche of their producer.

Real-Time Fluorescence Microscopy on Living E. coli Sheds New Light on the Antibacterial Effects of the King Penguin β-Defensin AvBD103b

(1) Antimicrobial peptides (AMPs) are a promising alternative to conventional antibiotics. Among AMPs, the disulfide-rich β-defensin AvBD103b, whose antibacterial activities are not inhibited by salts contrary to most other β-defensins, is particularly appealing. Information about the mechanisms of action is mandatory for the development and approval of new drugs. However, data for non-membrane-disruptive AMPs such as β-defensins are scarce, thus they still remain poorly understood. (2) We used single-cell fluorescence imaging to monitor the effects of a β-defensin (namely AvBD103b) in real time, on living E. coli, and at the physiological concentration of salts. (3) We obtained key parameters to dissect the mechanism of action. The cascade of events, inferred from our precise timing of membrane permeabilization effects, associated with the timing of bacterial growth arrest, differs significantly from the other antimicrobial compounds that we previously studied in the same physiological conditions. Moreover, the AvBD103b mechanism does not involve significant stereo-selective interaction with any chiral partner, at any step of the process. (4) The results are consistent with the suggestion that after penetrating the outer membrane and the cytoplasmic membrane, AvBD103b interacts non-specifically with a variety of polyanionic targets, leading indirectly to cell death.

In vivo spatiotemporal control of voltage-gated ion channels by using photoactivatable peptidic toxins

Photoactivatable drugs targeting ligand-gated ion channels open up new opportunities for light-guided therapeutic interventions. Photoactivable toxins targeting ion channels have the potential to control excitable cell activities with low invasiveness and high spatiotemporal precision. As proof-of-concept, we develop HwTxIV-Nvoc, a UV light-cleavable and photoactivatable peptide that targets voltage-gated sodium (NaV) channels and validate its activity in vitro in HEK293 cells, ex vivo in brain slices and in vivo on mice neuromuscular junctions. We find that HwTxIV-Nvoc enables precise spatiotemporal control of neuronal NaV channel function under all conditions tested. By creating multiple photoactivatable toxins, we demonstrate the broad applicability of this toxin-photoactivation technology.

Complementary Nuclear Magnetic Resonance-Based Metabolomics Approaches for Glioma Biomarker Identification in a Drosophila melanogaster Model

Human malignant gliomas are the most common type of primary brain tumor. Composed of glial cells and their precursors, they are aggressive and highly invasive, leading to a poor prognosis. Due to the difficulty of surgically removing tumors and their resistance to treatments, novel therapeutic approaches are needed to improve patient life expectancy and comfort. Drosophila melanogaster is a compelling genetic model to better understanding human neurological diseases owing to its high conservation in signaling pathways and cellular content of the brain. Here, glioma has been induced in Drosophila by co-activating the epidermal growth factor receptor and the phosphatidyl-inositol-3 kinase signaling pathways. Complementary nuclear magnetic resonance (NMR) techniques were used to obtain metabolic profiles in the third instar larvae brains. Fresh organs were directly studied by ¹H high resolution-magic angle spinning (HR-MAS) NMR, and brain extracts were analyzed by solution-state ¹H-NMR. Statistical analyses revealed differential metabolic signatures, impacted metabolic pathways, and glioma biomarkers. Each method was efficient to determine biomarkers. The highlighted metabolites including glucose, myo-inositol, sarcosine, glycine, alanine, and pyruvate for solution-state NMR and proline, myo-inositol, acetate, and glucose for HR-MAS show very good performances in discriminating samples according to their nature with data mining based on receiver operating characteristic curves. Combining results allows for a more complete view of induced disturbances and opens the possibility of deciphering the biochemical mechanisms of these tumors. The identified biomarkers provide a means to rebalance specific pathways through targeted metabolic therapy and to study the effects of pharmacological treatments using Drosophila as a model organism.

A Venomics Approach Coupled to High-Throughput Toxin Production Strategies Identifies the First Venom-Derived Melanocortin Receptor Agonists

Animal venoms are rich in hundreds of toxins with extraordinary biological activities. Their exploitation is difficult due to their complexity and the small quantities of venom available from most venomous species. We developed a Venomics approach combining transcriptomic and proteomic characterization of 191 species and identified 20,206 venom toxin sequences. Two complementary production strategies based on solid-phase synthesis and recombinant expression in Escherichia coli generated a physical bank of 3597 toxins. Screened on hMC4R, this bank gave an incredible hit rate of 8%. Here, we focus on two novel toxins: N-TRTX-Preg1a, exhibiting an inhibitory cystine knot (ICK) motif, and N-BUTX-Ptr1a, a short scorpion-CSαβ structure. Neither N-TRTX-Preg1a nor N-BUTX-Ptr1a affects ion channels, the known targets of their toxin scaffolds, but binds to four melanocortin receptors with low micromolar affinities and activates the hMC1R/Gs pathway. Phylogenetically, these two toxins form new groups within their respective families and represent novel hMC1R agonists, structurally unrelated to the natural agonists.

New protein-DNA complexes in archaea: a small monomeric protein induces a sharp V-turn DNA structure

MC1, a monomeric nucleoid-associated protein (NAP), is structurally unrelated to other DNA-binding proteins. The protein participates in the genome organization of several Euryarchaea species through an atypical compaction mechanism. It is also involved in DNA transcription and cellular division through unknown mechanisms. We determined the 3D solution structure of a new DNA-protein complex formed by MC1 and a strongly distorted 15 base pairs DNA. While the protein just needs to adapt its conformation slightly, the DNA undergoes a dramatic curvature (the first two bend angles of 55° and 70°, respectively) and an impressive torsional stress (dihedral angle of 106°) due to several kinks upon binding of MC1 to its concave side. Thus, it adopts a V-turn structure. For longer DNAs, MC1 stabilizes multiple V-turn conformations in a flexible and dynamic manner. The existence of such V-turn conformations of the MC1-DNA complexes leads us to propose two binding modes of the protein, as a bender (primary binding mode) and as a wrapper (secondary binding mode). Moreover, it opens up new opportunities for studying and understanding the repair, replication and transcription molecular machineries of Archaea.

White striping and wooden breast myopathies of broiler breast muscle is affected by time-limited feeding, genetic background, and egg storage

The effects of time-limited feeding, genetic background, and egg storage on white striping (WS) and wooden breast (WB) in broilers were studied. Male chicks (240) from 2 genetic backgrounds and 2 egg storage periods were fed on either an ad libitum (AL) or time-limited (TL) program from 7 d of age. A rapid growth strain (Growth) and an enhanced yield strain (Yield) of broiler breeder males were mated to a single female line and eggs were stored for periods of either 1 to 7 d or 8 to 14 d. Body weight (BW), feed consumption, and feed conversion ratio (FCR) were determined weekly. Carcass data including WS and WB scores were collected at 42 d of age. Breast muscle scoring was conducted either visually or by hand palpation using a 1 to 4 point ordinal scale (normal to greatest severity). Data were analyzed using the Mixed procedure of SAS. The TL fed broilers presented less WS (1.64 vs. 2.87) and WB (2.14 vs. 2.89), lower BW (2.99 vs. 3.27 kg), and improved FCR (1.55 vs. 1.58 g: g), as well as reduced dressing percentage (79.5 vs. 80.1%), breast muscle yield (33.3 vs. 34.6%), and 24 h muscle pH (5.82 vs. 5.95) relative to AL broilers (P < 0.01). Yield broilers exhibited reduced BW (2.97 vs. 3.28 kg), lower WS (2.04 vs. 2.47), and greater WB (2.65 vs. 2.38) (P < 0.05) but similar dressing percentage (80.0 vs. 79.7%) and breast muscle yield (34.3 vs. 33.6%) when compared to Growth broilers. Longer egg storage generated lower BW (3.07 vs. 3.18 kg) and when fed AL, an increased WS score (2.58 vs. 3.15) compared to the shorter egg storage period (P < 0.05). It was concluded that WS and WB could be reduced by TL feeding and that genetic background and egg storage period may influence the expression of WS and WB.

Synthesis by native chemical ligation and characterization of the scorpion toxin AmmTx3

The scorpion toxin AmmTx3 is a specific blocker of K_v4 channels. It was shown to have interesting potential for neurological disorders. In this study, we report the first chemical synthesis of AmmTx3 by using the native chemical ligation strategy and validate its biological activity. We determined its 3D structure by nuclear magnetic resonance spectroscopy, and pointed out that AmmTx3 possesses the well-known CSαβ structural motif, which is found in a large number of scorpion toxins. Overall, this study establishes an easy synthetic access to biologically active AmmTx3 toxin.

Complete 1H, 15N and 13C assignment of trappin-2 and 1H assignment of its two domains, elafin and cementoin

Trappin-2 is a serine protease inhibitor with a very narrow inhibitory spectrum and has significant anti-microbial activities. It is a 10 kDa cationic protein composed of two distinct domains. The N-terminal domain (38 residues) named cementoin is known to be intrinsically disordered when it is not linked to the elafin. The C-terminal domain (57 residues), corresponding to elafin, is a cysteine-rich domain stabilized by four disulfide bridges and is characterized by a flat core and a flexible N-terminal part. To our knowledge, there is no structural data available on trappin-2. We report here the complete (1)H, (15)N and (13)C resonance assignment of the recombinant trappin-2 and the (1)H assignments of cementoin and elafin, under the same experimental conditions. This is the first step towards the 3D structure determination of the trappin-2.

Backbone assignment of the three dimers of HU from Escherichia coli at 293 K: EcHUα2, EcHUβ2 and EcHUαβ

HU is one of the major nucleoid-associated proteins involved in bacterial chromosome structure and in all DNA-dependent cellular activities. Similarly to eukaryotic histones, this small dimeric basic protein wraps DNA in a non-sequence specific manner, promoting DNA super-structures. In most bacteria, HU is a homodimeric protein encoded by a single gene. However, in enterobacteria such as Escherichia coli, the presence of two genes coding for two peptidic chains, HUα and HUβ, lead to the coexistence of three forms: two homodimers EcHUα2 and EcHUβ2, as well as a heterodimer EcHUαβ. Genetic and biochemical investigation suggest that each EcHU dimer plays a specific physiological role in bacteria. Their relative abundance depends on the environmental conditions and is driven by an essential, yet unknown, fast outstanding chain-exchange mechanism at physiological temperature. Our goal is to understand this fundamental mechanism from a structural and kinetics standpoint using NMR. For this purpose, the first steps are the assignment of each dimer in their native and intermediate states. Here, we report the backbone assignment of each HU dimers from E. coli at 293 K in their native state.

Chemical shifts assignments of the archaeal MC1 protein and a strongly bent 15 base pairs DNA duplex in complex

MC1 is the most abundant architectural protein present in Methanosarcina thermophila CHTI55 in laboratory growth conditions and is structurally unrelated to other DNA-binding proteins. MC1 functions are to shape and to protect DNA against thermal denaturation by binding to it. Therefore, MC1 has a strong affinity for any double-stranded DNA. However, it recognizes and preferentially binds to bent DNA, such as four-way junctions and negatively supercoiled DNA minicircles. Combining NMR data, electron microscopy data, biochemistry, molecular modelisation and docking approaches, we proposed recently a new type of DNA/protein complex, in which the monomeric protein MC1 binds on the concave side of a strongly bent 15 base pairs DNA. We present here the NMR chemical shifts assignments of each partner in the complex, (1)H (15)N MC1 protein and (1)H (13)C (15)N bent duplex DNA, as first step towards the first experimental 3D structure of this new type of DNA/protein complex.

Three-dimensional NMR structure of Hen Egg Gallin (Chicken Ovodefensin) reveals a new variation of the β-defensin fold

Gallin is a 41-residue protein, first identified as a minor component of hen egg white and found to be antimicrobial against Escherichia coli. Gallin may participate in the protection of the embryo during its development in the egg. Its sequence is related to antimicrobial β-defensin peptides. In the present study, gallin was chemically synthesized 1) to further investigate its antimicrobial spectrum and 2) to solve its three-dimensional NMR structure and thus gain insight into structure-function relationships, a prerequisite to understanding its mode(s) of action. Antibacterial assays confirmed that gallin was active against Escherichia coli, but no additional antibacterial activity was observed against the other Gram-positive or Gram-negative bacteria tested. The three-dimensional structure of gallin, which is the first ovodefensin structure to have been solved to date, displays a new five-stranded arrangement. The gallin three-dimensional fold contains the three-stranded antiparallel β-sheet and the disulfide bridge array typical of vertebrate β-defensins. Gallin can therefore be unambiguously classified as a β-defensin. However, an additional short two-stranded β-sheet reveals that gallin and presumably the other ovodefensins form a new structural subfamily of β-defensins. Moreover, gallin and the other ovodefensins calculated by homology modeling exhibit atypical hydrophobic surface properties, compared with the already known vertebrate β-defensins. These specific structural features of gallin might be related to its restricted activity against E. coli and/or to other yet unknown functions. This work provides initial understanding of a critical sequence-structure-function relationship for the ovodefensin family.

The addressing fragment of mitogaligin: first insights into functional and structural properties

Mitogaligin is a mitochondrion-targeting protein involved in cell death. The sequence of the protein is unrelated to that of any known pro- or antiapoptotic protein. Mitochondrial targeting is controlled by an internal sequence from residues 31 to 53, and although this sequence is essential and sufficient to provoke cell death, the precise mechanism of action at the mitochondrial membrane remains to be elucidated. Here, by focusing on the [31-53] fragment, we first assessed and confirmed its cell cytotoxicity by microinjection. Subsequently, with the aid of membrane models, we evaluated the impact of the membrane environment on the 3D structure of the peptide and on how the peptide is embedded and oriented within membranes. The fragment is well organized, even though it does not contain a canonical secondary structure, and adopts an interfacial location. Structural comparison with other membrane-interacting Trp-rich peptides demonstrated similarities with the antimicrobial peptide tritrpcidin.

Initial insights into structure-activity relationships of avian defensins

Numerous β-defensins have been identified in birds, and the potential use of these peptides as alternatives to antibiotics has been proposed, in particular to fight antibiotic-resistant and zoonotic bacterial species. Little is known about the mechanism of antibacterial activity of avian β-defensins, and this study was carried out to obtain initial insights into the involvement of structural features or specific residues in the antimicrobial activity of chicken AvBD2. Chicken AvBD2 and its enantiomeric counterpart were chemically synthesized. Peptide elongation and oxidative folding were both optimized. The similar antimicrobial activity measured for both L- and D-proteins clearly indicates that there is no chiral partner. Therefore, the bacterial membrane is in all likelihood the primary target. Moreover, this work indicates that the three-dimensional fold is required for an optimal antimicrobial activity, in particular for gram-positive bacterial strains. The three-dimensional NMR structure of chicken AvBD2 defensin displays the structural three-stranded antiparallel β-sheet characteristic of β-defensins. The surface of the molecule does not display any amphipathic character. In light of this new structure and of the king penguin AvBD103b defensin structure, the consensus sequence of the avian β-defensin family was analyzed. Well conserved residues were highlighted, and the potential strategic role of the lysine 31 residue of AvBD2 was emphasized. The synthetic AvBD2-K31A variant displayed substantial N-terminal structural modifications and a dramatic decrease in activity. Taken together, these results demonstrate the structural as well as the functional role of the critical lysine 31 residue in antimicrobial activity.

Rational design of peptides active against the gram positive bacteria Staphylococcus aureus

In an attempt to increase the antimicrobial activity of the insect defensin from Anopheles gambiae, which is active against Staphylococcus aureus at low concentration, hybrid defensins were designed by combining conserved sequence regions and variable regions of insect defensins. Their activity against S. aureus strains sensitive and resistant to conventional antibiotics was evaluated, and the toxicity of the most active molecules was tested. The three-dimensional structure of Anopheles gambiae defensin and five hybrids were determined by NMR and molecular modelling. This strategy led to the design of two chimeric defensins with increased activity compared with the native molecule, but one of them appears to be toxic to mice at a rather low concentration. The structure of the CS alphabeta motif, which is a characteristic of insect defensin, is sensitive to sequence modifications, in particular in the N-terminal loop. The existence of the CS alphabeta is most probably a prerequisite for the stability and the activity of the molecule, but is not sufficient by itself since the hybrid displaying the best defined structure is not active against the tested strains. The analysis of the structure, in relation with the activity and the toxicity data, underlines the importance of turns and of the N-terminal loop. Residues located in the turns contributing to the preservation of positive electrostatic areas at the surface of the molecules seem particularly important for the activity of the molecule, while residues involved in the N-terminal loop are both involved in the modulation of the activity and the toxicity of the molecule.

Surgical management of pelvic organ prolapse in females: functional outcome of mesh sacrocolpopexy and rectopexy as a combined procedure

PURPOSE

Urogenital prolapse is relatively common compared with rectal prolapse and the combination of urogenital prolapse and rectal prolapse is still more infrequent. This study was designed to evaluate the functional outcome of a series of patients who have undergone open mesh sacrocolporectopexy surgery for combined vaginal and rectal prolapse.

METHODS

Consecutive patients from June 2000 to June 2004 with confirmed vaginal and rectal prolapse subsequently underwent open mesh sacrocolporectopexy. The Cleveland Clinic Short Form-20 Pelvic Floor Distress Inventory questionnaire with Urinary Distress Inventory, Pelvic Organ Prolapse Distress Inventory, and Colorectal-Anal Distress Inventory subscales was completed by all patients preoperatively and at six months postoperatively.

RESULTS

There were 29 patients with a median age of 66 (interquartile range, 59-73) years. Median period of follow-up was 26 (interquartile range, 15-33) months. Median global pelvic floor distress inventory scores were lower postoperatively compared with preoperatively (96.4 (interquartile range, 50.8-149.7) vs. 182.3 (interquartile range, 140.6-208.6; P = 0.001). All three median subscales scores also were significantly lower postoperatively compared with preoperatively.

CONCLUSIONS

In patients with concurrent vaginal and rectal prolapse, open mesh sacrocolporectopexy confers good symptomatic improvement for urinary-, vaginal-, and rectal-related symptoms.

Accessibility of tobacco lipid transfer protein cavity revealed by 15N NMR relaxation studies and molecular dynamics simulations

Plant LTP1 are small helical proteins stabilized by four disulfide bridges and are characterized by the presence of an internal cavity, in which various hydrophobic ligands can be inserted. Recently, we have determined the solution structure of the recombinant tobacco LTP1_1. Unexpectedly, despite a global fold very similar to the structures already known for cereal seed LTP1, its binding properties are different: Tobacco LTP1_1 is able to bind only one monoacylated lipid, whereas cereal LTP1 can bind either one or two. The 3D structure of tobacco LTP1_1 revealed the presence of a hydrophobic cluster, not observed on cereal LTP1 structures, which may hinder one of the two entrances of the cavity defined for wheat LTP1. To better understand the mechanism of lipid entrance for tobacco LTP1_1 and to define the regions of the protein monitoring the accessibility of the cavity, we have complemented our structural data by the study of the internal dynamics of tobacco LTP1_1, using (15)N magnetic relaxation rate data and MD simulations at room and high temperatures. This work allowed us to define two regions of the protein experiencing the largest motions. These two regions delineate a portal that opens up during the simulation constituting a unique entrance of the hydrophobic cavity, in contrast with wheat LTP1 where two routes were detected. The hydrophobic interactions resulting from a few point mutations are strong enough to completely block the second portal so that the accessibility of the cavity is restricted to one entrance, explaining why this particular LTP1 binds only one lipid molecule.

Solution structures of stomoxyn and spinigerin, two insect antimicrobial peptides with an alpha-helical conformation

Stomoxyn and spinigerin belong to the class of linear cysteine-free insect antimicrobial peptides that kill a range of microorganisms, parasites, and some viruses but without any lytic activity against mammalian erythrocytes. Stomoxyn is localized in the gut epithelium of the nonvector stable fly that is sympatric with the trypanosome vector tsetse fly. Spinigerin is stored and secreted by hemocytes from the fungus-growing termite. The structure of synthetic stomoxyn and spinigerin in aqueous solution and in TFE/water mixtures was analyzed by CD and NMR spectroscopy combined with molecular modeling calculations. Stomoxyn and spinigerin adopt a flexible random coil structure in water while both assume a stable helical structure in the presence of TFE. In 50% TFE, the structure of stomoxyn is typical of cecropins, including an amphipathic helix at the N-terminus and a hydrophobic C-terminus with helical features that probably fold in a helical conformation at higher TFE concentration. In contrast to stomoxyn, spinigerin acquires very rapidly a helical conformation. In 10% TFE the helix is highly bent and the structure is poorly defined. In 50% TFE, the helical structure is well defined all along its sequence, and the slightly bent alpha-helix displays an amphiphilic character, as observed for magainin 2. The structural similarities between stomoxyn and cecropin A from Hyalophora cecropia and between spinigerin and magainin 2 suggest a similar mode of action on the bacterial membranes of both pairs of peptides. Our results also confirm that TFE induces helix formation and propagation for amino acids showing helical propensity in water but also enhances the helix propagation propensity of nonpolar beta-branched residues.

Combined therapeutic use of AdGFPFasL and small molecule inhibitors of ceramide metabolism in prostate and head and neck cancers: a status report

As of January 2005, there were 1020 gene therapy clinical trials ongoing worldwide with 675 or 66.2% devoted to cancer gene therapy. The majority are occurring in the US and Europe (http://www.wiley.co.uk/genetherapy/clinical/). At the present time, to our knowledge there are no trials that employ gene delivery of Fas Ligand (FasL). As an important note, and in contrast to somatic cell therapy trials, there are no reported deaths due to therapeutic vector administration in any cancer gene therapy trial. That said, from our studies and from the published literature, the issue of gene delivery remains the major obstacle to successfully employing gene therapy for cancer treatment. Numerous laboratories are studying this with many different approaches. My co-workers and I have focused on the delivery issue by using various approaches that address tumor targeting and transgene expression. In addition, we are focusing on enhancing tumor cell killing via the bystander effect and through use of small molecules to enhance bystander activity.

Solution structure of a tobacco lipid transfer protein exhibiting new biophysical and biological features

Plant lipid transfer proteins are small soluble extracellular proteins that are able to bind and transfer a variety of lipids in vitro. Recently, it has been proposed that lipid transfer proteins may play a key role in plant defence mechanisms, especially during the induction of systemic acquired resistance. However, very little is known about the proteins expressed in developing plants and tissues, since almost all the biophysical and structural data available to date on lipid transfer proteins originate from proteins present in storage tissues of monocot cereal seeds. In this paper, we report the structural and functional characteristics of a lipid transfer protein (named LTP1_1) constitutively expressed in young aerial organs of Nicotiana tabacum (common tobacco). The unlabelled and uniformly labelled proteins were produced in the yeast Pichia pastoris, and we determined the three-dimensional (3D) structure of LTP1_1 using nuclear magnetic resonance (NMR) spectroscopy and molecular modeling techniques. The global fold of LTP1_1 is very close to the previously published structures of LTP1 extracted from cereal seeds, including an internal cavity. However, the chemical shift variations of several NMR signals upon lipid binding show that tobacco LTP1_1 is able to bind only one LysoMyristoylPhosphatidylCholine (LMPC), while wheat and maize LTPs can bind either one or two. Titration experiments using intrinsic tyrosine fluorescence confirm this result not only with LMPC but also with two fatty acids. These differences can be explained by the presence in tobacco LTP1_1 of a hydrophobic cluster closing the second possible access to the protein cavity. This result suggests that LTP1 lipid binding properties could be modulated by subtle changes in a conserved global structure. The biological significance of this finding is discussed in the light of the signalling properties of the tobacco LTP1_1-jasmonate complex described elsewhere.

Probing the hydrophobic cavity of lipid transfer protein from Nicotiana tabacum through xenon-based NMR spectroscopy

The hydrophobic cavity of Lipid Transfer Protein 1 from Nicotiana tabacum is investigated in detail by NMR using xenon as a spy. The analysis of the (129)Xe chemical shifts and self-relaxation times gives evidence of protein-xenon interaction. Thermodynamics of the binding is characterized through the study of aliphatic (1)H and (13)C chemical shift variation as a function of xenon pressure. The binding constant is evaluated to 75.5 +/- 1.0 M(-1) at 293 K. The location of xenon inside the cavity is deduced from SPINOE experiments. The noble gas appears to occupy four sites, and xenon self-relaxation experiments indicate that it quickly jumps between different sites. The chemical shifts of amide protons and nitrogens also depend on the xenon concentration, either specifically or nonspecifically for atoms at the external surface of the protein. Yet, contrary to aliphatic atoms, they do not correspond to short-range interactions as confirmed by magnetization transfer experiments between laser-polarized xenon and protons in H(2)O. These (15)N chemical shift variations, used in combination with (15)N transverse self-relaxation rates to determine the lower limit of the binding rate, consequently reveal subtle changes in the structure of the protein upon binding.

Lead optimization of antifungal peptides with 3D NMR structures analysis

Antimicrobial peptides are key components of the innate immune response in most multicellular organisms. These molecules are considered as one of the most innovative class of anti-infective agents that have been discovered over the last two decades, and therefore, as a source of inspiration for novel drug design. Insect cystine-rich antimicrobial peptides with the CS alpha beta scaffold (an alpha-helix linked to a beta-sheet by two disulfide bridges) represent particularly attractive templates for the development of systemic agents owing to their remarkable resistance to protease degradation. We have selected heliomicin, a broad spectrum antifungal CS alpha beta peptide from Lepidoptera as the starting point of a lead optimization program based on phylogenic exploration and fine tuned mutagenesis. We report here the characterization, biological activity, and 3D structure of heliomicin improved analogs, namely the peptides ARD1, ETD-135, and ETD-151. The ARD1 peptide was initially purified from the immune hemolymph of the caterpillars of Archeoprepona demophoon. Although it differs from heliomicin by only two residues, it was found to be more active against the human pathogens Aspergillus fumigatus and Candida albicans. The peptides ETD-135 and ETD-151 were engineered by site-directed mutagenesis of ARD1 in either cationic or hydrophobic regions. ETD-135 and ETD-151 demonstrated an improved antifungal activity over the native peptides, heliomicin and ARD1. A comparative analysis of the 3D structure of the four molecules highlighted the direct impact of the modification of the amphipathic properties on the molecule potency. In addition, it allowed to characterize an optimal organization of cationic and hydrophobic regions to achieve best antifungal activity.

Solution Structure of Spheniscin, a β-Defensin from the Penguin Stomach

Recently two beta-defensins, named spheniscins, have been isolated from the stomach content of the king penguin (Aptenodytes patagonicus), which is capable of preserving food for several weeks during egg incubation (Thouzeau, C., Le Maho, Y., Froget, G., Sabatier, L., Le Bohec, C., Hoffmann, J. A., and Bulet, P. (2003) J. Biol. Chem. 278, 51053-51058). It has been proposed that, in combination with other antimicrobial peptides, spheniscins may be involved in this long term preservation of food in the bird's stomach. To draw some structure/function features, the three-dimensional structure in aqueous solution of the most abundant spheniscin (Sphe-2) was determined by two-dimensional NMR and molecular modeling techniques. The overall fold of Sphe-2 includes a three-stranded antiparallel beta-sheet stabilized by three disulfide bridges with a pairing typical of beta-defensins. In addition, the N-terminal segment shows helical features on most structures. Sphe-2 is highly cationic, and its surface displays a hydrophobic patch. Comparative modeling revealed that this patch is preserved in avian defensins. The activity of Sphe-2 against a pathogenic Gram-positive strain was retained in vitro in the conditions of osmolarity found in penguin stomach content and also in different salt concentrations and compositions up to those reported for seawater. Comparison with structurally related mammalian beta-defensins showed that the hydrophobic patch is not preserved in mammalian beta-defensins and that the high cationicity of Sphe-2 is presumably the critical factor for its retained activity in high salt concentrations. Such peculiarities, in addition to a broad activity spectrum, suggest that penguin defensins may represent interesting probes for the design of highly efficient antibiotics to fight off pathogens that develop in relatively salt-rich body fluids.

Solution structure of Alo-3: a new knottin-type antifungal peptide from the insect Acrocinus longimanus

Insect peptides are key elements of the innate immunity against bacteria and fungi. These molecules offer remarkable properties: high efficacy, a low probability of resistance, limited toxicity, and immunogenicity. In this context, we are investigating several classes of peptides, and we have been successful in identifying biologically important classes of peptides and small molecules that will provide a stream of drug candidates for treating severe, life-threatening, hospital-acquired infections and other pathologies of high medical need. Recently, we have isolated a new class of antifungal peptides from the coleopteran Acrocinus longimanus. Three homologous peptides, Alo-1, Alo-2, and Alo-3, with sequence identity above 80% and active against the Candida glabrata yeast strain were identified. Alo-3 displayed the highest activity against Candida glabrata and was thus chosen for structure determination using NMR spectroscopy and molecular modeling. Alo-3 contains six cysteine residues forming three disulfide bridges. The pairing of the cysteines was assessed using ambiguous disulfide restraints within the ARIA software, allowing us to establish that Alo-3 belongs to the inhibitor cystine-knot family. It exhibits all the structural features characteristic of the knottin fold, namely, a triple-stranded antiparallel beta-sheet with a long flexible loop connecting the first strand to the second strand and a series of turns. To our knowledge, Alo-3 is the first peptide from insects with antimicrobial activity adopting the knottin fold. Alo-3 shows a level of activity significantly higher against C. glabrata than Alo-1 or Alo-2. It has no negatively charged residues and displays on its surface a cationic pole that may account for its antifungal activity. This finding is validated by the comparison of the structure of Alo-3 with the structure of other structurally related peptides from other sources also showing antifungal activity.

Most of the structural elements of the globular domain of murine prion protein form fibrils with predominant beta-sheet structure

The conversion of the cellular prion protein into the beta-sheet-rich scrapie prion protein is thought to be the key step in the pathogenesis of prion diseases. To gain insight into this structural conversion, we analyzed the intrinsic structural propensity of the amino acid sequence of the murine prion C-terminal domain. For that purpose, this globular domain was dissected into its secondary structural elements and the structural propensity of the protein fragments was determined. Our results show that all these fragments, excepted that strictly encompassing helix 1, have a very high propensity to form structured aggregates with a dominant content of beta-sheet structures.

Solution structures of the antifungal heliomicin and a selected variant with both antibacterial and antifungal activities

In response to an experimental infection, the lepidopteran Heliothis virescens produces an antifungal protein named heliomicin. Heliomicin displays sequence similarities with antifungal plant defensins and antibacterial or antifungal insect defensins. To gain information about the structural elements required for either antifungal or antibacterial activity, heliomicin and selected point-mutated variants were expressed in yeast as fusion proteins. The effects of mutations, defined by comparing the primary structure of heliomicin with the sequences of members of the insect defensin family, were analyzed using antibacterial and antifungal assays. One of the variants shows significant activity against Gram-positive bacteria while remaining efficient against fungi. The three-dimensional structures of this variant and of the wild-type protein were determined by two-dimensional (1)H NMR to establish a correlation between structure and antibacterial or antifungal activity. Wild-type and mutated heliomicins adopt a similar scaffold, including the so-called cysteine-stabilized alphabeta motif. A comparison of their structures with other defensin-type molecules indicates that common hydrophobic characteristics can be assigned to all the antifungal proteins. A comparative analysis of various structural features of heliomicin mutant and of antibacterial defensins enables common properties to be assessed, which will help to design new mutants with increased antibacterial activity.

Quality of hospital care of children with asthma: Medicaid versus privately insured patients

Asthma is an important condition to study in the Medicaid population because it is the most frequent reason for hospital admission of Medicaid children, with rates substantially higher than those of non-Medicaid children. This study addressed how the quality of hospital care provided to children with asthma on Medicaid compares with that provided to privately insured children. Children inpatient records were studied in California, Georgia, and Michigan, comparing the care that was provided to standards created by a national panel of physician experts. Process-of-care analysis showed that Medicaid children in each state were more likely than privately insured children to be discharged on suboptimal medication regimens. This study concluded that hospitals serving Medicaid children, at least in these three states, are providing asthma inpatient care of fairly comparable quality to that of privately insured children. However, there remain significant problems surrounding outpatient medication regimens and follow-up care.

Magnetization transfer from laser-polarized xenon to protons located in the hydrophobic cavity of the wheat nonspecific lipid transfer protein

Nonspecific lipid transfer protein from wheat is studied by liquid-state NMR in the presence of xenon. The gas-protein interaction is indicated by the dependence of the protein proton chemical shifts on the xenon pressure and formally confirmed by the first observation of magnetization transfer from laser-polarized xenon to the protein protons. Twenty-six heteronuclear nOes have allowed the characterization of four interaction sites inside the wheat ns-LTP cavity. Their locations are in agreement with the variations of the chemical shifts under xenon pressure and with solvation simulations. The richness of the information obtained by the noble gas with a nuclear polarization multiplied by approximately 12,000 makes this approach based on dipolar cross-relaxation with laser-polarized xenon promising for probing protein hydrophobic pockets at ambient pressure.

The active site of drosomycin, a small insect antifungal protein, delineated by comparison with the modeled structure of Rs-AFP2, a plant antifungal protein

Drosomycin is the first strictly antifungal protein isolated from an insect (Drosophila melanogaster). The solution structure of this 44-residue protein has been reported previously. It involves a three-stranded beta-sheet and an alpha-helix, the protein global fold being maintained by four disulfide bridges. Rs-AFP2 is a plant antifungal protein exhibiting 41% sequence similarity with drosomycin. Mutational analysis of Rs-AFP2 showed the importance of some residues in the antifungal activity of the protein against the fungus target. In order to determine the structural features responsible for antifungal activity in both drosomycin and Rs-AFP2, we modeled the three-dimensional structure of Rs-AFP2, and of other antifungal proteins, using the solution structure of drosomycin as a template. Structure analysis of drosomycin and Rs-AFP2, and comparisons with the other modeled antifungal structures, revealed that the two proteins shared a hydrophobic cluster located at the protein surface in which a lysine residue is embedded. Based on these close structural similarities and the experimental data available for Rs-AFP2 mutants, an antifungal active site of the insect protein is proposed.

Differences between child and parent reports of symptoms among Latino children with asthma

OBJECTIVES

To determine, in a population of predominantly Latino children with asthma 6 to 18 years old, whether parent and child reports of asthma symptoms with exercise differ and to evaluate the validity of child and parent reports of symptoms.

DESIGN

Data obtained from child and parent interviews; pulmonary function tests (forced vital capacity, forced expiratory volume in 1 second, forced expiratory flow25-75, peak expiratory flow), and observation of symptoms after exercise.

SETTING

Three summer camps for minority children with asthma in Los Angeles County.

PARTICIPANTS

A total of 97 children with asthma (78% Latino, 12% non-Latino White, 9% Other; 6 to 18 years of age) and their parents.

INTERVENTION(S)

None.

PRIMARY OUTCOME MEASURES

Child and parent reports of cough and wheezing with exercise and pulmonary function tests before and after exercise. While at camp, children underwent spirometry after completing the self-administered survey. The pulmonary function tests were conducted and interpreted according to the pediatric specifications for spirometry, and results >80% of predicted, adjusted for gender, age, height, and race, were considered normal. Six peak expiratory flow rates (PEFR) by peak flow meter also were recorded by trained research assistants immediately before spirometry, and values >80% of predicted based on height were considered normal. To observe child symptoms with exercise, children participated in a relay running race of 200 feet followed by a swimming race of 300 feet. Research assistants measured heart rate and 6 PEFRs using ASSESS portable peak flow meters immediately before and after each exercise. A positive exercise challenge was defined as a 15% reduction in mean PEFR and/or observed asthma symptoms (cough, wheezing, chest pain, asthma attack).

RESULTS

Of the children, 18% reported never having a cough when they exercised, 46% reported having it occasionally when they exercised, and 36% reported having it quite often or always when they exercised. For wheezing, 20% of children reported never having wheezing when they exercised, 35% having it occasionally when they exercised, and 45% having it quite often or always when they exercised. Parents reported fewer symptoms than did their children. Of the parents, 34% reported that their children did not have cough with exercise, 37% reported few to some days, and 29% reported most days or every day. Forty-seven percent of parents reported that their child did not wheeze with exercise in the last 2 months, 35% reported wheezing on a few days to some days, and 17% reported wheezing most days to every day. Parent and child reports of cough or wheezing after exercise correlated mildly with each other (parent/child cough r = 0. 23; kappa = 0.03; parent/child wheezing r = 0.21; kappa = 0.14). Children were more likely to report cough: 59 of 71 (83%) of children versus 44 of 71 (62%) of parents. The 22 children who reported cough when their parents did not account for most of the disagreement between parents and children. Children were more likely than were their parents to report wheezing; 55 of 69 (80%) children versus 36 of 69 (52%) parents reported that the child wheezed. The 24 children who reported wheezing when their parents did not account for most of the disagreement between parents and children. Forty-seven percent of the children had a value <80% of predicted for at least one of the four spirometry tests; 29% of mean baseline PEFRs were <80% of predicted. Overall, 86% of the children met one or more of the following: any percent of predicted pulmonary function tests <80% or any symptom or PEFR reduction of 15% after exercise, or other occurrence of nonexercise symptoms during camp. Almost all child reports of cough and wheezing correlated significantly with the criterion validity criteria. For example, child reports of wheezing were, as expected, correlated negatively with the percent of predicted FEV1 (r = -0.28) and correlated positive

[Scorpion toxins and defensins]

The scorpion venoms possess many neurotoxic peptides which constitute a group of molecular families with a common architecture and a high degree of polymorphism. This architecture is found also in circulating antimicrobial peptides belonging to the defensins family, which are especially structurally related to the blocking potassium channels neurotoxins. The diversification in functions with a unique architectural scheme is discussed taking in account the biophysiological characteristics of the scorpion order.

A novel composite 90 degrees pulse sequence which provides distortionless NMR spectra and suppresses without destroying the water magnetization

A novel 90 degrees composite pulse sequence which allows one to record 1D and 2D NMR spectra without disturbing the water magnetization is described. A home-written program was used to optimize the pulse angles for which the pulse sequence response fitted best the desired excitation profile, producing a neat and distortionless spectrum with a broad null excitation at the carrier frequency. The resulting pulse sequence was first evaluated using the simulation program "PENCIL" and then tested on two protein samples. A 3.5 degrees phase shift of the last pulse was required to cancel correctly the water signal. The pulse scheme was appended to a NOESY pulse sequence. Inspection of the water cross section revealed interactions between water and some protons of drosomycine, a small insect antifungal protein.

Early presentation of type 2 diabetes in Mexican-American youth

OBJECTIVE

To describe features of pediatric-onset type 2 diabetes in the Hispanic population.

RESEARCH DESIGN AND METHODS

The medical records of 55 Hispanic subjects with diabetes who were treated from 1990 to 1994 in a pediatric clinic serving lower income Mexican-Americans were reviewed to assess the frequency and clinical features of type 2 diabetes. Additionally, nondiabetic siblings of several patients underwent oral glucose tolerance testing, and a survey of six high schools in the same county was performed.

RESULTS

Seventeen of 55 (31%) of the diabetic children and adolescents had type 2 diabetes. An additional 4 Hispanic children with type 2 diabetes treated in other clinics were also identified, yielding a total of 21 subjects who were used to describe the characteristics of childhood type 2 diabetes. At presentation, all were obese (mean BMI 32.9 +/- 6.2 kg/m2), 62% had no ketonuria, and fasting C-peptide levels were elevated (4.28 +/- 3.43 ng/ml). Diabetes was easily controlled with diet, sulfonylureas, or low-dose insulin. No autoantibodies were present in those tested, and family histories were positive for type 2 diabetes. Compliance was poor, and 3 subjects developed diabetic complications. Of the tested siblings, 2 of 8 had impaired glucose tolerance and 5 of 8 had stimulated hyperinsulinemia, correlated with BMI (r = 0.80, P < 0.05). The school survey identified 28 diabetic adolescents, 75% more than expected (P < 0.01). The Hispanic enrollment at each school was highly correlated with the number of diabetic students (r = 0.87, P = 0.011).

CONCLUSIONS

Genetic susceptibility to type 2 diabetes, when coupled with obesity, can produce type 2 diabetes in Mexican-American children. This diagnosis should be considered in young Hispanic patients, who might otherwise be assumed to have type 1 diabetes, and also when caring for overweight Hispanic youth with a family history of type 2 diabetes, in whom intervention may prevent or delay diabetes onset.

Solution structure of drosomycin, the first inducible antifungal protein from insects

Drosomycin is the first antifungal protein characterized recently among the broad family of inducible peptides and proteins produced by insects to respond to bacterial or septic injuries. It is a small protein of 44 amino acid residues extracted from Drosophila melanogaster that exhibits a potent activity against filamentous fungi. Its three-dimensional structure in aqueous solution was determined using 1H 2D NMR. This structure, involving an alpha-helix and a twisted three-stranded beta-sheet, is stabilized by three disulfide bridges. The corresponding Cysteine Stabilized alpha beta (CS alpha beta) motif, which was found in other defense proteins such as the antibacterial insect defensin A, short- and long-chain scorpion toxins, as well as in plant thionins and potent antifungal plant defensins, appears as remarkably persistent along evolution.

Refined solution structure of the anti-mammal and anti-insect LqqIII scorpion toxin: comparison with other scorpion toxins

The solution structure of the anti-mammal and anti-insect LqqIII toxin from the scorpion Leiurus quinquestriatus quinquestriatus was refined and compared with other long-chain scorpion toxins. This structure, determined by 1H-NMR and molecular modeling, involves an alpha-helix (18-29) linked to a three-stranded beta-sheet (2-6, 33-39, and 43-51) by two disulfide bridges. The average RMSD between the 15 best structures and the mean structure is 0.71 A for C alpha atoms. Comparison between LqqIII, the potent anti-mammal AaHII, and the weakly active variant-3 toxins revealed that the LqqIII three-dimensional structure is closer to that of AaHII than to the variant-3 structure. Moreover, striking analogies were observed between the electrostatic and hydrophobic potentials of LqqIII and AaHII. Several residues are well conserved in long-chain scorpion toxin sequences and seem to be important in protein structure stability and function. Some of them are involved in the CS alpha beta (Cysteine Stabilized alpha-helix beta-sheet) motif. A comparison between the sequences of the RII rat brain and the Drosophila extracellular loops forming scorpion toxin binding-sites of Na+ channels displays differences in the subsites interacting with anti-mammal or anti-insect toxins. This suggests that hydrophobic as well as electrostatic interactions are essential for the binding and specificity of long-chain scorpion toxins.

1H-NMR-derived secondary structure and the overall fold of the potent anti-mammal and anti-insect toxin III from the scorpion Leiurus quinquestriatus quinquestriatus

We describe the secondary structure and the overall fold of toxin III from the venom of the scorpion Leiurus quinquestriatus quinquestriatus determined using two-dimensional-1H-NMR spectroscopy. This protein, which contains 64 amino acids and 4 disulfide bridges, belongs to the long-chain toxin category and is highly toxic to both mammals and insects. The overall fold was determined on the basis of 1208 inter-proton-distance restraints derived from NOE measurements and 90 psi, phi dihedral-angle restraints derived from NOE connectivities and 3JNH-alphaH coupling constants using the HABAS program. This fold, which mainly consists of an alpha-helix packed against a small antiparallel three-stranded beta-sheet, and of several turns and loops, is similar to that of other long-chain scorpion toxins. Aromatic and non-polar residues form several patches on the surface of the protein which alternate with patches of charged and polar residues. Such a topology should be important in the interactions of toxin III with sodium channels in membranes. Two weakly constrained loops introduce some flexibility to the structure which could be related to the activity of this toxin. The central core of toxin III is compared with the cysteine-stabilized alpha beta motif (an alpha-helix connected to a beta-sheet through two disulfide bridges) found in insect defensins and plant thionins. Defensins and thionins are small proteins (approximately 40--50 amino acid residues) containing three or four disulfide bridges, respectively. This comparison confirms that the cysteine-stabilized alpha beta motif is a common core to a number of small proteins from different origins and having different activities.

Comparison of the T cell receptors on insulin-specific hybridomas from insulin transgenic and nontransgenic mice. Loss of a subpopulation of self-reactive clones

Transgenic mice expressing the human insulin gene do not produce insulin-specific antibody after injection of human insulin. Nevertheless, they have some peripheral T cells that proliferate to human insulin in vitro. To investigate the nature of these T cells, human insulin-specific T cell hybridomas were produced from transgenic and nontransgenic mice. Transgenic hybridomas required more insulin to achieve maximum responses and they produced lower levels of lymphokines than nontransgenic hybridomas. The majority of nontransgenic hybridomas recognized only human and pork insulin whereas transgenic hybridomas recognized beef, sheep, and/or horse insulin in addition to human and pork insulin. The TCR expressed by transgenic and nontransgenic hybridomas were determined by Northern analysis. Both types of hybridomas used several different V alpha and V beta gene families and no favored association between V alpha and V beta gene usage was detected in either type. V beta 1 was used by 7 of 16 nontransgenic hybridomas but only by 1 of 16 transgenic hybridomas. V beta 6 receptors were predominantly expressed by the transgenic hybridomas and all V beta 6-bearing hybridomas recognized beef as well as human insulin. The differences in Ag reactivity and TCR gene usage suggest that V beta 1-bearing human insulin-reactive T cells were clonally deleted or inactivated in the transgenic animal. Other clones, representing a minor subpopulation in nontransgenic mice, were recovered from transgenic mice.

Comparison of the T cell receptors on insulin-specific hybridomas from insulin transgenic and nontransgenic mice. Loss of a subpopulation of self-reactive clones

Transgenic mice expressing the human insulin gene do not produce insulin-specific antibody after injection of human insulin. Nevertheless, they have some peripheral T cells that proliferate to human insulin in vitro. To investigate the nature of these T cells, human insulin-specific T cell hybridomas were produced from transgenic and nontransgenic mice. Transgenic hybridomas required more insulin to achieve maximum responses and they produced lower levels of lymphokines than nontransgenic hybridomas. The majority of nontransgenic hybridomas recognized only human and pork insulin whereas transgenic hybridomas recognized beef, sheep, and/or horse insulin in addition to human and pork insulin. The TCR expressed by transgenic and nontransgenic hybridomas were determined by Northern analysis. Both types of hybridomas used several different V alpha and V beta gene families and no favored association between V alpha and V beta gene usage was detected in either type. V beta 1 was used by 7 of 16 nontransgenic hybridomas but only by 1 of 16 transgenic hybridomas. V beta 6 receptors were predominantly expressed by the transgenic hybridomas and all V beta 6-bearing hybridomas recognized beef as well as human insulin. The differences in Ag reactivity and TCR gene usage suggest that V beta 1-bearing human insulin-reactive T cells were clonally deleted or inactivated in the transgenic animal. Other clones, representing a minor subpopulation in nontransgenic mice, were recovered from transgenic mice.

Nicotinamide and 3-aminobenzamide interfere with receptor-mediated transmembrane signaling in murine cytotoxic T cells: independence of Golgi reorientation from calcium mobilization and inositol phosphate generation

The two competitive inhibitors of ADP-ribosylation, nicotinamide and 3-aminobenzamide, have been reported to interfere with TNF-induced cell apoptosis, and there is evidence that they inhibit killer-induced target cell lysis as well. There are very few drugs known to specifically interfere with target apoptosis induced by killer cells. We therefore sought to explore the effects these inhibitors have on CTL-mediated cell lysis. Here we show that TcR-mediated transmembrane signaling in CTL, measured by Ca2+ mobilization and generation of inositol phosphates, is inhibited by nicotinamide. The possibility that all cell functions are suppressed by the drug is excluded by the finding that constitutive secretion of BLT serine esterase is not inhibited, whereas stimulated secretion of this enzyme is suppressed. We also show that nicotinamide does not interfere with CTL target cell binding or reorientation of the Golgi apparatus toward the target binding site. It is concluded that nicotinamide inhibits transmembrane signaling in CTL and thereby interferes with delivery of the lethal hit to targets.