New chemotypes for wALADin1-like inhibitors of delta-aminolevulinic acid dehydratase from Wolbachia endobacteria

Substituted benzimidazoles of the wALADin1-family have recently been identified as a new class of species-selective inhibitors of delta-aminolevulinic acid dehydratase (ALAD) from Wolbachia endobacteria of parasitic filarial worms. Due to its Wolbachia-dependent antifilarial activity, wALADin1 is a starting point for the development of new drugs against filarial nematodes. We now present several other chemotypes of ALAD inhibitors that have been identified based upon their molecular similarity to wALADin1. A tricyclic quinoline derivative (wALADin2) with a different inhibitory mechanism and improved inhibitory potency and selectivity may represent an improved drug lead candidate.     

Isolation and characterization of rat primary lung cells

Summary Lung cell culture may be useful as anin vitro alternative to study the susceptibility of the lung to various toxic agents. Lungs from female Wistar rats were enzymatically digested by recirculating perfusion through the pulmonary artery with a sequence of solutions containing deoxyribonuclease, chymopapain, pronase, collagenase, and elastase. Lung tissue was microdissected and resuspended and the cells obtained were washed by centrifugation. By this isolation method, 2×10⁸ cells per rat lung were obtained with an average viability of 97%. Lung cells cultured in medium containing antibiotics and serum maintained a viability of >70% for 5 d. Rat primary lung cells were exposed to various toxic agents and their viability was assessed by formazan production capacity after 18 h of incubation. Compared to rat and mouse hepatocyte cultures (EC⁵⁰=5.8 mM), rat primary lung cells were much more susceptible to hydrogen peroxide (EC₅₀=0.6 mM). All cell types were equally sensitive to the more potent toxicanttert-butylhydroperoxide (EC₅₀=0.1 mM). Paraquat was more toxic to lung cells (EC₅₀=0.03 mM) than to rat (EC₅₀=2.8 mM) and mouse (EC₅₀=0.2 mM) hepatocytes. In contrast, rat lung cells were less sensitive to sodium nitroprusside (EC₅₀=2.6 mM) compared to rat (EC₅₀=0.2 mM) and mouse (EC₅₀=0.03 mM) hepatocytes. Nitrofurantoin and menadione (at EC₅₀=0.04 mM and 0.006 mM, respectively) were more toxic to rat lung and liver cells than to murine hepatocytes (EC₅₀=0.2 mM and 0.04 mM, respectively). Our findings demonstrate the applicability of this rat primary lung cell culture for studying the effects of lung toxicants. Parts of the study had been presented orally at the meeting of the German Society of Toxicology and Pharmacology in Mainz (FRG), March 15–17, 1994.     

Attitudes Towards the Donation of Human Embryos for Stem Cell Research Among Chinese IVF Patients and Students

Bioethical debates on the use of human embryos and oocytes for stem cell research have often been criticized for the lack of empirical insights into the perceptions and experiences of the women and couples who are asked to donate these tissues in the IVF clinic. Empirical studies that have investigated the attitudes of IVF patients and citizens on the (potential) donation of their embryos and oocytes have been scarce and have focused predominantly on the situation in Europe and Australia. This article examines the viewpoints on the donation of embryos for stem cell research among IVF patients and students in China. Research into the perceptions of patients is based on in-depth interviews with IVF patients and IVF clinicians. Research into the attitudes of students is based on a quantitative survey study (n=427). The empirical findings in this paper indicate that perceptions of the donation of human embryos for stem cell research in China are far more diverse and complex than has commonly been suggested. Claims that ethical concerns regarding the donation and use of embryos and oocytes for stem cell research are typical for Western societies but absent in China cannot be upheld. The article shows that research into the situated perceptions and cultural specificities of human tissue donation can play a crucial role in the deconstruction of politicized bioethical argumentation and the (often ill-informed) assumptions about “others” that underlie socio-ethical debates on the moral dilemmas of technology developments in the life sciences.     

Validating Resolution Revolution

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The FTLD risk factor TMEM106B and MAP6 control dendritic trafficking of lysosomes

TMEM106B is a major risk factor for frontotemporal lobar degeneration with TDP‐43 pathology. TMEM106B localizes to lysosomes, but its function remains unclear. We show that TMEM106B knockdown in primary neurons affects lysosomal trafficking and blunts dendritic arborization. We identify microtubule‐associated protein 6 (MAP6) as novel interacting protein for TMEM106B. MAP6 over‐expression inhibits dendritic branching similar to TMEM106B knockdown. MAP6 knockdown fully rescues the dendritic phenotype of TMEM106B knockdown, supporting a functional interaction between TMEM106B and MAP6. Live imaging reveals that TMEM106B knockdown and MAP6 overexpression strongly increase retrograde transport of lysosomes in dendrites. Downregulation of MAP6 in TMEM106B knockdown neurons restores the balance of anterograde and retrograde lysosomal transport and thereby prevents loss of dendrites. To strengthen the link, we enhanced anterograde lysosomal transport by expressing dominant‐negative Rab7‐interacting lysosomal protein (RILP), which also rescues the dendrite loss in TMEM106B knockdown neurons. Thus, TMEM106B/MAP6 interaction is crucial for controlling dendritic trafficking of lysosomes, presumably by acting as a molecular brake for retrograde transport. Lysosomal misrouting may promote neurodegeneration in patients with TMEM106B risk variants.     

A generic approach to engineer antibody pH-switches using combinatorial histidine scanning libraries and yeast display

There is growing interest in the fast and robust engineering of protein pH-sensitivity that aims to reduce binding at acidic pH, compared to neutral pH. Here, we describe a novel strategy for the incorporation of pH-sensitive antigen binding functions into antibody variable domains using combinatorial histidine scanning libraries and yeast surface display. The strategy allows simultaneous screening for both, high affinity binding at pH 7.4 and pH-sensitivity, and excludes conventional negative selection steps. As proof of concept, we applied this strategy to incorporate pH-dependent antigen binding into the complementary-determining regions of adalimumab. After 3 consecutive rounds of separate heavy and light chain library screening, pH-sensitive variants could be isolated. Heavy and light chain mutations were combined, resulting in 3 full-length antibody variants that revealed sharp, reversible pH-dependent binding profiles. Dissociation rate constants at pH 6.0 increased 230- to 780-fold, while high affinity binding at pH 7.4 in the sub-nanomolar range was retained. Furthermore, binding to huFcRn and thermal stability were not affected by histidine substitutions. Overall, this study emphasizes a generalizable strategy for engineering pH-switch functions potentially applicable to a variety of antibodies and further proteins-based therapeutics.     

First insight into the genome of an uncultivated crenarchaeote from soil

Molecular phylogenetic surveys based on the characterization of 16S rRNA genes have revealed that soil is an environment particularly rich in microbial diversity. A clade of crenarchaeota (archaea) has frequently been detected among many other novel lineages of uncultivated bacteria. In this study we have initiated a genomic approach for the characterization of uncultivated microorganisms from soil. We have developed a procedure based on a two-phase electrophoresis technique that allows the fast and reliable purification of concentrated and clonable, high molecular weight DNA. From this DNA we have constructed complex large-insert genomic libraries. Using archaea-specific 16S rRNA probes we have isolated a 34 kbp fragment from a 900 Mbp fosmid library of soil DNA. The clone contained a complete 16S/23S rRNA operon and 17 genes encoding putative proteins. Phylogenetic analyses of the rRNA genes and of several protein encoding genes (e.g. DNA polymerase, FixAB, glycosyl transferase) confirmed the specific affiliation of the genomic fragment with the non-thermophilic clade of the crenarchaeota. Content and structure of the genomic fragment indicated that the archaea from soil differ significantly from their previously studied uncultivated marine relatives. The protein encoding genes gave the first insights into the physiological potential of these organisms and can serve as a basis for future genomic and functional genomic studies.     

Filaria-induced IL-10 suppresses murine cerebral malaria

Filarial nematodes achieve long survival in their hosts due to their capacity to modulate immune responses. Therefore, immunomodulation by filarial nematodes may alter responses to concomitant infections such as malaria. Cerebral malaria (CM), a severe complication of Plasmodium falciparum infections, is triggered as a consequence of the immune response developed against malaria parasites. The question arises whether prior infection with helminth parasites is beneficial against CM. In the present work a murine model for subsequent has been used to assess this hypothesis. C57BL/6 mice were infected with the rodent filarial parasite Litomosoides sigmodontis and the murine model parasite for CM, Plasmodium berghei ANKA. Previously filaria-infected C57BL/6 mice showed significantly reduced CM rates. CD8⁺ T cell recruitment to the brain, a hallmark for CM development, was reduced in protected mice. Furthermore, in contrast to P. berghei single-infected animals, filaria-infected mice had significantly higher levels of circulating IL-10. The requirement for IL-10 in CM protection was demonstrated by the lack of protection in IL-10 KO mice. This suggests that the anti-inflammatory IL-10 elicited by filarial nematodes is able to suppress the overwhelming inflammatory reaction otherwise triggered against malaria parasites in C57BL/6 mice, preventing full progress to CM.     

Identification of invariant chain CD74 as a functional receptor of tissue inhibitor of metalloproteinases-1 (TIMP-1)

Multifunctionality of tissue inhibitor of metalloproteinases-1 (TIMP-1) comprising antiproteolytic as well as cytokinic activity has been attributed to its N-terminal and C-terminal domains, respectively. The molecular basis of the emerging proinflammatory cytokinic activity of TIMP-1 is still not completely understood. The cytokine receptor invariant chain (CD74) is involved in many inflammation-associated diseases and is highly expressed by immune cells. CD74 triggers zeta chain–associated protein kinase-70 (ZAP-70) signaling–associated activation upon interaction with its only known ligand, the macrophage migration inhibitory factor. Here, we demonstrate TIMP-1–CD74 interaction by coimmunoprecipitation and confocal microscopy in cells engineered to overexpress CD74. In silico docking in HADDOCK predicted regions of the N-terminal domain of TIMP-1 (N-TIMP-1) to interact with CD74. This was experimentally confirmed by confocal microscopy demonstrating that recombinant N-TIMP-1 lacking the entire C-terminal domain was sufficient to bind CD74. Interaction of TIMP-1 with endogenously expressed CD74 was demonstrated in the Namalwa B lymphoma cell line by dot blot binding assays as well as confocal microscopy. Functionally, we demonstrated that TIMP-1–CD74 interaction triggered intracellular ZAP-70 activation. N-TIMP-1 was sufficient to induce ZAP-70 activation and interference with the cytokine-binding site of CD74 using a synthetic peptide–abrogated TIMP-1-mediated ZAP-70 activation. Altogether, we here identified CD74 as a receptor and mediator of cytokinic TIMP-1 activity and revealed TIMP-1 as moonlighting protein harboring both cytokinic and antiproteolytic activity within its N-terminal domain. Recognition of this functional TIMP-1–CD74 interaction may shed new light on clinical attempts to therapeutically target ligand-induced CD74 activity in cancer and other inflammatory diseases.     

The structural basis for unidirectional rotation of thermoalkaliphilic F1-ATPase

The ATP synthase of the thermoalkaliphilic Bacillus sp. TA2.A1 operates exclusively in ATP synthesis direction. In the crystal structure of the nucleotide-free alpha(3)beta(3)gamma epsilon subcomplex (TA2F(1)) at 3.1 A resolution, all three beta subunits adopt the open beta(E) conformation. The structure shows salt bridges between the helix-turn-helix motif of the C-terminal domain of the beta(E) subunit (residues Asp372 and Asp375) and the N-terminal helix of the gamma subunit (residues Arg9 and Arg10). These electrostatic forces pull the gamma shaft out of the rotational center and impede rotation through steric interference with the beta(E) subunit. Replacement of Arg9 and Arg10 with glutamines eliminates the salt bridges and results in an activation of ATP hydrolysis activity, suggesting that these salt bridges prevent the native enzyme from rotating in ATP hydrolysis direction. A similar bending of the gamma shaft as in the TA2F(1) structure was observed by single-particle analysis of the TA2F(1)F(o) holoenzyme.